bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Properties and Size of Microscopic Pollutant Particles in the Urban Area of Coimbra
Authors: Gomes C.R. , Dinis A.M. , Rocha A.F. , Gomes E.M.C. , Neves L.F.
Published: October 2008

Pollutant particles of small size are produced and resuspended every day as a result of traffic. These particles, identified as particulate matter (PM10, PM2.5), can affect human health when inhaled, mostly the respiratory and cardiopulmonary systems. Some of these particles are ferromagnetic (s.l.) and their magnetic properties indicate their sources, composition and size. Coimbra is an inland city situated in the center of Portugal at a distance of 40 km from the coast. Coimbra has a total area of 320 km2 and a population of about 168.000. Motor vehicle traffic is the main source of air pollutant in the city. The main goal of this research is to assess pollution levels in the urban area of Coimbra using the magnetic properties of microscopic pollutant particles on Nerium oleander leaves.
Trichomes Morphology and Essential Oils Characterization of Field-Growing and In Vitro Propagated Plants of Lavandula pedunculata
Authors: Zuzarte M. , Dinis A.M. , Cavaleiro C. , Canhoto J. , Salgueiro L.
Published: October 2008

The selection of native Lavandula species and their economic exploitation have increased in the last few years. Micropropagation techniques have been used as an alternative for vegetative propagation allowing the multiplication of selected genotypes and chemotypes. Our previous studies showed that the essential oils of Lavandula pedunculata have an important antifungal activity against dermatophyte strains. Therefore, a new line of investigation concerning the in vitro culture of this species is justified. In the present study we compare the morphology of the leaf trichomes and the chemical composition of their essential oils in both field-growing and in vitro propagated plants.
Helicobacter pylori Phage Screening
Authors: Vale Filipa F. , Matos António P.A. , Carvalho Patrícia , Vítor Jorge M.B.
Published: October 2008

Helicobacter pylori is a helical shaped Gram-negative bacterium that colonizes the human stomach. It is associated with several human pathologies, such as gastritis, peptic ulcer, and gastric cancer. The standard first-line treatment is a one week triple therapy: the association of two antibiotics, most frequently amoxicillin and clarithromycin, and a proton pump inhibior. Despite the evolution of the treatment strategy, quadruple therapy, there is an increasing percentage of failure of the antibiotic therapy, due to antibiotics resistance. Phage therapy is the therapeutic use of lytic bacteriophages to treat pathogenic bacterial infections and H. pylori is a good target. However there are no available phage collections, and H. pylori phages description is diminutive on literature.
Comparative ultrastructural study of human corpus cavernosum during ageing
Authors: Tomada N. , Oliveira R. , Tomada I. , Vendeira P. , Neves D.
Published: October 2008

Erectile Dysfunction (ED), the inability to achieve or maintain an erection of sufficient rigidity for completion of sexual act, is a common condition affecting more than 150 million of men worldwide. This disorder is highly associated with aging, however concomitant pathologies such as hyperlipidemia, hypertension, and diabetes also contribute to ED progression. In the Massachusetts Male Aging Study, age was considered an independent variable strongly associated with ED, showing that the prevalence of this disease increased with age from 38% in the youngest group of men (mean age 40 y.) to almost 70% in the oldest group of men examined (mean age 70 y.). It is well demonstrated that aging leads to changes in the cardiovascular system, which results in a decrease in elasticity due to fibrosis and an increase in stiffness of the arterial system, independently of the effects of concurrent pathologies. Vasculogenic ED is the most prevalent condition, affecting nearly 80% of patients with organic etiology. Small vessels of the penis are very sensitive to structural and functional changes, and small disturbances can conduce to ED. ED is now considered by some authors as synonymous to endothelial dysfunction and an early manifestation of atherosclerosis, being a precursor of systemic vascular disease. Human cavernous tissue is mainly constituted by smooth muscle fibers that surround sinusoid vessels. Corpus cavernosum structural elements act in concert, allowing increase of intra-cavernous arterial flow and smooth muscle relaxation processes which are fundamental to penile erection. The aim of this study was to compare the ultrastructural anatomy of the young and aged human corpus cavernosum, in the absence of additional risk factors.
Testing the Reliability of Anatomical and Epidermical Characters in Grass Taxonomy
Authors: Cristina M. , Dinis A. , Sales F.
Published: October 2008

Grasses are simplified plants and the leaf is one of the few organs that provides taxonomic characters. Leaf anatomy and epidermis (and associated structures) have been used as characters in taxonomy of Poaceae since the 1930s. Such characters became well-established and accepted in the 1960s with Metcalfe's investigations. However, recent research casts doubts on the consistency and reliability of such characters [e.g. 3]. Grasses are highly adaptable plants due to their marked phenotypic plasticity. In order to assess the reliability of leaf characters, species that occur in very contrasting habitats constitute the ideal case study. Corynephorus canescens (L.) P. Beauv. and Antinoria agrostidea (DC.) Parl. were selected; the former occurs from coastal sandy dunes to high altitude, the latter survives submerged and in ponds that dry-out during summer.
The Palynological Compass: A Case Study In Viticoideae (Vitex L.)
Authors: Cabral C. , Möller M. , Sales F.
Published: October 2008

The concept of palynological compass was introduced in 1969 by Erdtman to express the way palynological evidence points to systematic relationships. Recent evidence shows that, in the cases studied, the palynological compass points to the same phylogenetic direction as the molecular data.
Evaluating Structural Differences in Cortical Bone Tissue After Demineralization and Calcination
Authors: Martins Gabriela , Freitas João , Judas Fernando , Trindade Bruno , Figueiredo Helena
Published: October 2008

Although the best results in bone grafting have been achieved with autogeneuos bone tissue, allografts and xenografts have been widely used either in mineralized, demineralized, or calcined forms. Demineralized bone has been proven to stimulate new bone formation by exposing, proteins and growth factors necessary for osteoinduction. On the other hand, calcined bone offers a natural architectural mineralized matrix, not present in synthetic apatite materials, as well as an excellent source of calcium. Despite the extensive use and importance of these materials, systematic works regarding their characterization are relatively scarce.
Organic matter in space - An overview
Authors: van Dishoeck Ewine F.
Published: October 2008

Organic compounds are ubiquitous in space: they are found in diffuse clouds, in the envelopes of evolved stars, in dense star-forming regions, in protoplanetary disks, in comets, on the surfaces of minor planets, and in meteorites and interplanetary dust particles. This brief overview summarizes the observational evidence for the types of organics found in these regions, with emphasis on recent developments. The Stardust sample-return mission provides the first opportunity to study primitive cometary material with sophisticated equipment on Earth. Similarities and differences between the types of compounds in different regions are discussed in the context of the processes that can modify them. The importance of laboratory astrophysics is emphasized.
Molecular spectral line surveys and the organic molecules in the interstellar molecular clouds
Authors: Ohishi Masatoshi
Published: October 2008

It is known that more than 140 interstellar and circumstellar molecules have so far been detected, mainly by means of the radio astronomy observations. Many organic molecules are also detected, including alcohols, ketons, ethers, aldehydes, and others, that are distributed from dark clouds and hot cores in the giant molecular clouds. It is believed that most of the organic molecules in space are synthesized through the grain surface reactions, and are evaporated from the grain surface when they are heated up by the UV radiation from adjacent stars.

On the other hand the recent claim on the detection of glycine have raised an important issue how difficult it is to confirm secure detection of weak spectra from less abundant organic molecules in the interstellar molecular cloud.

I will review recent survey observations of organic molecules in the interstellar molecular clouds, including independent observations of glycine by the 45 m radio telescope in Japan, and will discuss the procedure to securely identify weak spectral lines from organic molecules and the importance of laboratory measurement of organic species.
A confusion-limited spectral-line survey of Sgr B2(N) at 1, 2, and 3mm: Establishing the organic inventory in molecular clouds
Authors: Halfen DeWayne T. , Ziurys Lucy M.
Published: October 2008

We present preliminary results of an spectral-line survey at 1, 2, and 3 mm of the galactic center cloud Sgr B2(N). With the current data, several simple prebiotic molecules have been conclusively identified, while several more complex molecules have not. When complete, this survey will provide an accurate database of the gas-phase organic inventory in Sgr B2(N).
An ab-initio study of multiple conformers of glycine
Authors: Kaplan Dan , Recine Greg , Zhang H.
Published: October 2008

The recent combination of new computational chemistry techniques and high performance computational hardware is allowing unprecedented levels of accuracy in the calculations of physical quantities such as potential energy surfaces and rotational-vibrational spectra. Previous results exist in the literature for the first three most stable conformers of glycine at the aug-cc-pVDZ basis set. In this work, we extend the known results, presenting calculations of the four most stable conformers of glycine using the aug-cc-pVQZ basis set. We compare our calculations to experimental values and show that our current calculations differ by <2% from measured values, much better than results from previous years. When searching for molecules in the Interstellar Medium this small difference suggests that computational methods are becoming well-suited for the task. The natural question to ask is: at what point will the small deviation from experimental values render our computations just as reliable as experiments? We feel that the current results show that we are indeed close to this goal.
A Search for Interstellar CH2D+
Authors: Wootten Alwyn , Turner Barry E.
Published: October 2008

We report on a search for interstellar CH2D+. Four transitions occur in easily accessible portions of the spectrum; we report on emission at the frequencies of these transitions toward high column density star-forming regions. While the observations can be interpreted as being consistent with a detection of the molecule, further observations will be needed to secure its identification. The CH2D+ rotational spectrum has not been measured to high accuracy. Its lines are weak, as the dipole moment induced by the inclusion of deuterium in the molecule is small. Astronomical detection is favored by observations toward strongly deuterium-fractionated sources. However, enhanced deuteration is expected to be most significant at low temperatures. The sparseness of the available spectrum and the low excitation in regions of high fractionation make secure identification of CH2D+ difficult. Nonetheless, owing to the importance of CH3+ to interstellar chemistry, and the lack of rotational transitions of that molecule owing to its planar symmetric structure, a measure of its abundance would provide key data to astrochemical models.
Comparing ice composition in dark molecular clouds
Authors: Knez C. , Moore M. , Travis S. , Ferrante R. , Chiar J. , Boogert A. , Mundy L. , Pendleton Y. , Tielens A. , van Dishoeck E. , Evans N.
Published: October 2008

We present 5–20 μm Spitzer/IRS spectroscopy toward stars behind dark molecular clouds. We present preliminary results from the Serpens dark cloud to show the variation between environments within a cloud. We are surveying 3 clouds with varying levels of star formation activity. Serpens has the highest level of activity from our 3 clouds. We show that location as well extinction can cause variations in ice composition. We also find that some lines of sight contain organic molecules such as methane and methanol, and the first detection of acetylene ice in the interstellar medium. We believe the high extinction lines of sight have been enriched by star formation activity near those lines of sight.
Fullerenes as carriers of extinction, diffuse interstellar bands and anomalous microwave emission
Authors: Iglesias-Groth Susana
Published: October 2008

According to semiempirical models, photoabsorption by fullerenes (single and multishell) could explain the shape, width and peak energy of the most prominent feature of the interstellar absorption, the UV bump at 2175 Å. Other weaker transitions are predicted in the optical and near-infrared providing a potential explanation for diffuse interstellar bands. In particular, we find that several fullerenes could contribute to the well known strong DIB at 4430 Å. Comparing cross sections and available data for this DIB and the UV bump we estimate a density of fullerenes in the diffuse interstellar medium of 0.1–0.2 ppm. These molecules could then be a major reservoir for interstellar carbon. We also study the rotation rates and electric dipole emission of hydrogenated icosahedral fullerenes. We investigate these molecules as potential carriers of the anomalous (dust-correlated) microwave emission recently detected by several cosmic microwave background experiments.
Testing the attribution of selected DIBs to dehydrogenated coronene cations
Authors: Mulas G. , Malloci G. , Porceddu I. , Joblin C.
Published: October 2008

Dehydrogenated coronene molecules have been proposed as the source of the UV-bump in the interstellar extinction curve as well as of some of the diffuse interstellar bands (DIBs). To test this hypothesis we have recently undertaken a combined (a) modelling, and (b) observational work on the subject. (a) In the framework of a global approach to the photophysics of a PAH–like species in space, we used combined theoretical calculated properties, obtained with (time–dependent) density functional theory, and a Monte–Carlo model simulating the time evolution of the population of levels of a given molecule, to obtain the detailed ro–vibrational spectral structure of selected electronic transitions. (b) From the observational point of view, we compare our predictions with observations of the well–known λ6284 and λ5780 DIBs.
Depleted diffuse bands in circumstellar envelopes of post-AGB stars
Authors: Cox N. L. J. , Luna R. , Satorre M. A. , García Hernández D. A. , Suárez O. , García Lario P.
Published: October 2008

We report on new results in the search for diffuse bands, signatures of still unknown origin, in the circumstellar envelopes of evolved (post-AGB) stars.
On buckyonions as a carrier of the 2175 Å interstellar extinction feature
Authors: Chen Juhua , Li Moping , Li Aigen , Wang Yongjiu
Published: October 2008

In recent years buckyonions have been suggested as a carrier of the 2175 Å interstellar extinction feature, based on the close similarity between the electronic transition spectra of buckyonions and the 2175 Å interstellar extinction feature. We examine this hypothesis by calculating the interstellar extinction with buckyonions as a dust component. It is found that dust models containing buckyonions (in addition to amorphous silicates, PAHs, graphite or amorphous carbon) can closely reproduce the observed interstellar extinction curve. However, a more severe challenge to the buckyonion hypothesis is provided by the non-detection of the ~7–8 μm C–H stretching bands expected from buckyonions in the diffuse interstellar medium. This will allow us to place an upper limit on the abundance of buckyonions.
Organic molecules in protostellar environments
Authors: Ceccarelli Cecilia
Published: October 2008

The sequence that brings matter from a molecular cloud to a fully developed star plus planetary system seems to be a unique and rich chemistry laboratory where, step by step, molecular complexity increases. During the cold pre-collapse phase, atoms and simple molecules, like CO, freeze out onto the dust grains, forming icy mantles. Reactions on the grain surfaces likely form hydrogenated molecules (notably H2O, CH4, H2CO, CH3OH, and NH3) and perhaps even more complex organic molecules. The hallmark of this era is the super-deuteration phenomenon, i. e. the abnormal enhancement of molecules containing one or more D atoms instead of H atoms, by up to 13 orders of magnitude with respect to the cosmic elemental D/H ratio (~10−5). The frozen molecules are released into the gas upon warming by the forming star and undergo reactions which further increase the molecular complexity, leading to several complex organic molecules. Products of this efficient chemical factory are observed in the hot corinos, which are warm (~100 K), dense (~107–108 cm−3) solar-system-sized regions at the centre of the collapsing envelopes of solar type protostars. In this contribution, I review what is known about the organic molecules in protostellar environments, with emphasis on the hot corinos, and how possibly the organic molecules formed at this stage may constitute an heritage for the forming planetary system.
The birth and death of organic molecules in protoplanetary disks
Authors: Henning Thomas , Semenov Dmitry
Published: October 2008

The most intriguing question related to the chemical evolution of protoplanetary disks is the genesis of pre-biotic organic molecules in the planet-forming zone. In this contribution we briefly review current observational knowledge of physical structure and chemical composition of disks and discuss whether organic molecules can be present in large amounts at the verge of planet formation. We predict that some molecules, including CO-bearing species such as H2CO, can be underabundant in inner regions of accreting protoplanetary disks around low-mass stars due to the high-energy stellar radiation and chemical processing on dust grain surfaces. These theoretical predictions are further compared with high-resolution observational data and the limitations of current models are discussed.
Precursors of complex organic molecules: NH3 and CH3OH in the ices surrounding low-mass protostars
Authors: Bottinelli Sandrine , Boogert Adwin C. A. , van Dishoeck Ewine F. , Beckwith Martha , Bouwman Jordy , Linnartz Harold , Öberg Karin I.
Published: October 2008

NH3 and CH3OH are key molecules in the chemical networks leading to the formation of complex N- and O-bearing organic molecules. However, despite a number of recent studies, there is still a lot to learn about their abundances in the solid state and how they relate to those of other N/O-bearing organic molecules or to NH3 and CH3OH abundances in the gas phase. This is particularly true in the case of low-mass young stellar objects (YSOs), for which only the recent advent of the Spitzer Space Telescope has allowed high sensitivity observations of the ices in their enveloppes. We present a combined study of Spitzer data (obtained within the Legacy program “From Molecular Cores to Planet-Forming Disks”, c2d) and laboratory spectra, leading to the detections of NH3 and CH3OH in the ices of low-mass protostars. We investigate correlations with other ice features and conclude with prospects on further studies linking these two precursors of complex organic molecules with their gas-phase products.
Chemical changes during transport from cloud to disk
Authors: Visser Ruud , van Dishoeck Ewine F. , Doty Steven D.
Published: October 2008

We present the first semi-analytical model that follows the chemical evolution during the collapse of a molecular cloud and the formation of a low-mass star and the surrounding disk. It computes infall trajectories from any starting point in the cloud and it includes a full time-dependent treatment of the temperature structure. We focus here on the freeze-out and desorption of CO and H2O. Both species deplete towards the centre before the collapse begins. CO evaporates during the infall phase and re-adsorbs when it enters the disk. H2O remains in the solid phase everywhere, except within a few AU of the star. Material that ends up in the planet- and comet-forming zones is predicted to spend enough time in a warm zone during the collapse to form complex organic species.
High-resolution observations of CH3CN in the hot corino of NGC1333-IRAS4A
Authors: Bottinelli Sandrine , Ceccarelli Cecilia , Neri Roberto , Williams Jonathan P.
Published: October 2008

The formation and evolution of complex organic molecules in the early stages of solar-type protostars (Class 0 objects) is crucial as it sets the stage for the content in pre-biotic molecules of the subsequent proto-planetary nebula. In order to understand the chemistry of these Class 0 objects, it is necessary to perform interferometric observations which allow us to resolve the hot corino, that is the warm, dense inner region of the envelope of a Class 0 object, where the complex organic molecules are located. Such observations exist for only two objects so far, IRAS16293-2422 and NGC1333-IRAS2A and we present here Plateau de Bure interferometric maps of a third hot corino, NGC1333-IRAS4A, which show emission of the complex organic molecule CH3CN arising from a region of size ~0.8″/175 AU, that is, of the order of the size of the Solar System. Combining these high-angular resolution maps with prior single-dish observations of the same transitions of CH3CN indicates that extended emission is also present, and we investigate the implications for organic chemistry in hot corinos.
Complex organic molecules in the intermediate mass protostar OMC2-FIR4
Authors: Crimier Nicolas , Ceccarelli Cecilia , Lefloch Bertrand , Faure Alex
Published: October 2008

We present the physical structure (density and temperature profiles) and the distribution of formaldehyde and methanol in intermediate mass protostar OMC2-FIR4 in the Orion molecular cloud complex.
Methanol formation: A Monte Carlo study
Authors: Das Ankan , Acharyya Kinsuk , Chakrabarti Sonali , Chakrabarti Sandip K.
Published: October 2008

We carry out a Monte-Carlo simulation to study the formation of methanol on the grain surfaces. We found that the recombination efficiencies are strongly dependent on the extrinsic properties of the grain, such as the number of sites on the grain surface and the flux of the accreting matter. This uses the concept of effective grain surface (denoted through a factor α) area which changes as the grain is populated.
Solid CH4 toward low-mass protostars: How much is there to build complex organics?
Authors: Öberg Karin I. , Boogert A. C. Adwin , Pontoppidan Klaus M. , Blake Geoffrey A. , Evans Neal J. , Lahuis Fred , van Dishoeck Ewine F.
Published: October 2008

We use Spitzer IRS spectra to determine the solid CH4 abundance toward a large sample (52 sources) of low mass protostars. 50% of the sources have an absorption feature at 7.7 μm, attributed to solid CH4. The solid CH4/H2O abundances are 2–13%, but toward sources with H2O column densities above 2 × 1018 cm−2, the CH4 abundances (20 out of 25) are nearly constant at 4.7 ± 1.6%. Correlations with CO2 and H2O together with the inferred abundances are consistent with CH4 formation through sequential hydrogenation of C on grain surfaces, but not with formation from CH3OH and formation in gas phase with subsequent freeze-out.
Collisional excitation of complex organic molecules
Authors: Faure Alexandre , Josselin Eric , Wiesenfeld Laurent , Ceccarelli Cecilia
Published: October 2008

A major difficulty in modelling the infrared and (sub)millimeter spectra of gas-phase complex organic molecules is the lack of state-to-state collisional rate coefficients. Accurate quantum or classical scattering calculations for large polyatomic species are indeed computationally highly challenging, particularly when both rotation and low frequency vibrations such as bending and torsional modes are involved. We briefly present here an approximate approach to estimate and/or extrapolate rotational and rovibrational rates for polyatomic molecules with many degrees of freedom.
Ion chemistry in the interstellar medium
Authors: Martinez Oscar , Snow Theodore P. , Bierbaum Veronica M.
Published: October 2008

Without accurate data on reaction rates and branching ratios, models of interstellar chemistry are unreliable. Recent research has identified a number of reactions of unusual importance because the rates and branching ratios are unknown or poorly known. Efforts to expand and improve on current databases are underway using a flowing afterglow-selected ion flow tube (FA-SIFT) coupled to a quadrupole mass spectrometer. Our current focus is on the reactions of C+, a major cation in the interstellar medium, with the neutrals O2, H2O, CH4, NH3 and C2H2. Future planned work includes studies of polycyclic aromatic hydrocarbons (PAHs), developing comprehensive pathways for their formation, and identification of those PAHs important to interstellar chemistry. The recent discovery of ISM anions has highlighted the importance of examining mechanisms of anionic chemistry in the interstellar medium, and we plan to obtain data relevant to the formation and destruction processes of molecular anions in space.
Molecular collisions : State-of-the-art calculations of inelastic collisions
Authors: Wiesenfeld Laurent , Faure Alexandre , Troscompt Nicolas , Wernli Michael , Ceccarelli Cecilia , Valiron Pierre
Published: October 2008

We set up a framework for calculating in a precise and controlled way the collisional properties of several molecules of astrophysical meaning. The quantities that are relevant for astrophysics are rotational and vibrational quenching/excitation rates by means of collisions of H2 with water and some organic molecules (HC3N, H2CO). We calculate those rates by means of successively determining a intermolecular potential energy surface and calculating inelastic cross sections and rates classically and/or quantum mechanically. These calculations are part of the European Union FP6 Molecular Universe program.
Observational constraints on the formation of interstellar methanol
Authors: Wirström E. S. , Persson C. M. , Hjalmarson Å. , Black J. H. , Bergman P. , Geppert W. D. , Hamberg M. , Vigren E.
Published: October 2008

The processes by which methanol, one of the most abundant interstellar organics, is formed in the interstellar medium are not yet accurately known. Pure gas-phase chemistry models fail to reproduce observed abundances by orders of magnitude, pointing to formation on grains and subsequent desorption.

Observations of methanol and its isotopologue 13CH3OH in several sources have been used to trace the origin, and thus the formation routes of methanol on interstellar grains, by means of isotope labelling a posteriori.
Molecular line observations and chemical modelling of galactic edge clouds
Authors: Ruffle Paul , Millar Tom , Roberts Helen , Lubowich Don , Henkel Christian
Published: October 2008

Edge Clouds 1 and 2 (EC1 and EC2) are large molecular clouds with the largest galactocentric distances known to exist in the Milky Way. We present observations of these clouds and use them to determine physical characteristics. For EC2 we calculate a gas temperature of 20 K and a density ofn(H2) ~ 104cm−3. Based on our CO maps, we estimate the mass of EC2 at around 104M⊙, and continuum observations suggest a dust-to-gas mass ratio as low as 0.001. Chemical models have been developed to reproduce the abundances in EC2 and they indicate that: heavy element abundances may be reduced by a factor of five relative to the solar neighbourhood (similar to dwarf irregular galaxies and damped Lyman alpha systems); very low extinction (AV< 4 mag) due to a very low dust-to-gas ratio; an enhanced cosmic ray ionisation rate; and a higher UV field compared to local interstellar values. The reduced abundances may be attributed to the low level of star formation in this region and are probably also related to the continuing infall of low metallicity halo gas since the Milky Way formed. We find that shocks from an old supernova remnant may have determined the morphology and dynamics of EC2, including the recently discovered star clusters embedded in the northern and southern cores. However, compared to EC2, EC1 appears to be a chemically less varied environment. The apparent molecule-poor nature of EC1 demonstrates the characteristics of clouds that have not had the benefit of SN shocks to stimulate an active cloud chemistry and star formation.
Ethylene in the circumstellar envelope of IRC+10216
Authors: Hinkle K. H. , Wallace L. , Richter M. J. , Cernicharo J.
Published: October 2008

Ethylene (C2H4) is a symmetric molecule that is best detected using mid-infrared transitions. We report on observations of the 10.5 μm ν7 band using the cryogenic grating spectrograph TEXES. These confirm the previous ethylene detection in the IRC+10216 circumstellar shell. We detect 18 ethylene lines. The lines are both narrow and weak with depths of no more than ~2%. The ethylene lines suggest an excitation temperature of ~80 K.
Molecular line observations of the SiO maser source IRAS 19312+1950
Authors: Nakashima J. , Deguchi S. , Imai H. , Kemball A.
Published: October 2008

IRAS 19312+1950 is a unique SiO maser source, exhibiting a rich set of molecular radio lines, although SiO maser sources are usually identified as oxygen-rich evolved stars, in which chemistry is relatively simple comparing with carbon-rich environments. The rich chemistry of IRAS 19312+1950 has raised a problem in circumstellar chemistry if this object is really an oxygen-rich evolved star, but its evolutional status is still controversial. In this paper, we briefly review the previous observations of IRAS 19312+1950, as well as presenting preliminary results of recent VLBI observations in maser lines. PDF file of the poster is available from http://www.geocities.jp/nakashima_junichi/
The physics and chemistry of circumstellar envelopes of S-stars on the AGB
Authors: Ramstedt Sofia , Schöier Fredrik L. , Olofsson Hans
Published: October 2008

Presented here are the preliminary results of a long-term study of S-stars on the AGB. S-stars are important as possible transition objects between oxygen-rich M-stars and carbon stars. The aim of the study is to compare results from our newly gathered observational database for the S-stars with those already obtained for the M- and carbon stars. We can thus follow the changes as the stars evolve along the AGB and more firmly establish the suggested M-MS-S-SC-C evolutionary sequence. It will also allow us to determine the relative importance of processes such as non-equilibrium chemistry, grain formation, and photodissociation in regulating the chemistry in circumstellar envelopes of AGB stars.
Molecular lines in the envelopes of evolved stars
Authors: Zhang Yong , Kwok Sun , Trung Dinh-V-
Published: October 2008

We report a spectral line survey of the circumstellar envelopes of evolved stars at millimeter wavelengths. The data allow us to investigate the chemical processes in different physical environments and evolutionary stages. A total of more than 500 emission features (mostly rotational transitions of molecules) are detected in the survey. Our observations show that the sources in different evolutionary stages have remarkably different chemical composition. As a star evolves from AGB stage to proto-planetary nebula, the abundances of Si-bearing molecules (SiO, SiCC, and SiS) decrease, while the abundances of some long-chain molecules, such as CH3CN, C4H, and HC3N, increase. After further evolution to planetary nebula, the abundances of neutral molecules dramatically decrease, and the emission from molecular ions becomes more intense. These differences can be attributed to the changes of the role that dust, stellar winds, shock waves, and UV/X-rays from the central star play in different evolutionary stages. These results will provide significant constraints on models of circumstellar chemistry.
The 1 mm spectrum of VY Canis Majoris: Chemistry in an O-rich envelope
Authors: Tenenbaum Emily D. , Milam Stefanie N. , Apponi Aldo J. , Woolf Neville J. , Ziurys Lucy M. , Schöier Fredrik L.
Published: October 2008

We present preliminary results of an unbiased spectral survey at 1 mm of the oxygen-rich supergiant, VY CMa. A number of exotic molecules have been detected, including NaCl and PO, and a relatively rich organic chemistry is observed. Results of the survey will be compared with carbon-rich stars.
HCO+ emission possibly related with a shielding mechanism that protects water molecules in the young PN K 3-35
Authors: Gómez Y. , Tafoya D. , Anglada G. , Loinard L. , Torrelles J. M. , Miranda L. F. , Osorio M. , Franco-Hernández R. , Nyman L. , Nakashima J. , Deguchi S.
Published: October 2008

Water maser emission has been detected only toward three planetary nebulae (PNe). In particular, in K3-35, the first PN where water vapor maser emission was detected, the components are located in a torus-like structure with a radius of 85 AU and also at the surprisingly large distance of 5000 AU from the star, in the tips of the bipolar lobes. The existence of these water molecules in PNe is puzzling, probably related to some unknown mechanism shielding them against the ionizing radiation. We report the detection of HCO+ (J = 1 − 0) emission toward K 3-35, that not only suggests that dense molecular gas (~105 cm−3) is present in this PN, but also that this kind of PN can enrich their surroundings with organic molecules.
Synthesis of organic compounds in the circumstellar environment
Authors: Kwok Sun
Published: October 2008

Through the techniques of millimeter-wave and infrared spectroscopy, over 60 species of gas-phase molecules and a variety of inorganic and organic solids have been detected in the short phase of stellar evolution between the asymptotic giant branch and planetary nebulae. The chemical pathways that lead to the synthesis of complex organic compounds in such low-density environments are therefore important topics of astrochemistry. In this review, we summarize the observational evidence for the existence of complex aliphatic and aromatic compounds in these circumstellar environments, and discuss the nature of their possible carriers. Also discussed are a number of unidentified emission features which may also have an organic origin. The possible relations between these circumstellar organic matter with Solar System organic matter are explored.
A Spitzer Space Telescope study of dust features in planetary nebula and Hii regions
Authors: Bernard-Salas Jeronimo , Peeters Els , Lebouteiller Vianney , Sloan Gregory C. , Brandl Bernhard R. , Houck James R.
Published: October 2008

One of the key questions of infrared astronomy is how the characteristics of dust depend on the physical properties of the surrounding medium. To address this question, we present results from the Spitzer Space Telescope on two projects designed to study the dust properties of a sample of 25 Planetary Nebulae (PNe) in the Magellanic Clouds, and three well-known Giant Hii regions (NGC 3603, 30 Doradus and N 66/NGC 346). Most PNe show emission from polycyclic aromatic hydrocarbons (PAHs) and only two of them show amorphous silicates. Eleven PNe display a strong broad feature around 11 μm which is attributed to silicon carbide and 8 of them show magnesium sulfide. One PNe, SMP LMC 11, shows spectacular absorption bands due to molecules which are the precursors from which more complex hydrocarbons are formed. The Spitzer spectra of the Hii regions, NGC 3603, 30 Doradus, and NGC 346 are very rich, displaying a wealth of spectral features within each region. This not only allows us to compare the dust at different metallicities but also to study the spatial variations of many features across a given region and correlate it with the distance to the ionizing cluster(s) and other parameters.
Spitzer spectroscopy of unusual hydrocarbons in cool radiative environments
Authors: Sloan G. C.
Published: October 2008

The Spitzer Space Telescope has discovered several objects with unusual spectra, where the emission features from polycyclic aromatic hydrocarbons (PAHs) are shifted to longer wavelengths than normally observed. Previously, only two of these class C PAH spectra had been identified. The new and larger sample reveals that PAHs emit at longer wavelengths when processed by cooler radiation fields. Limited laboratory data show that samples with mixtures of aromatic and aliphatic hydrocarbons produce emission features at longer wavelengths than purely aromatic samples. The aliphatic bonds are more fragile and would only survive in cooler radiation fields. In harsher radiation fields, the aliphatics attached to the aromatic hydrocarbons are destroyed.
Carbon-rich AGB stars in our Galaxy and nearby galaxies as possible sources of PAHs
Authors: Matsuura M. , Sloan G. C. , Bernard-Salas J. , Zijlstra A. A. , Wood P. R. , Whitelock P. A. , Menzies J. W. , Feast M. , Lagadec E. , Groenewegen M. A. T. , Cioni M. R. , van Loon J. Th. , Harris G.
Published: October 2008

We have obtained infrared spectra of carbon-rich AGB stars in three nearby galaxies – the Large and Small Magellanic Clouds, and the Fornax dwarf spheroidal galaxy. Our primary aim is to investigate gas compositions and mass-loss rate of these stars as a function of metallicity, by comparing AGB stars in several galaxies with different metallicities. C2H2are detectable from AGB stars, and possibly PAHs are subsequently formed from C2H2. Thus, it is worth investigating chemical processes at low metallicity. These stars were observed using the Infrared Spectrometer (irs) onboard theSpitzer Space Telescopewhich covers 5–35 μm region, and the Infrared Spectrometer And Array Camera (isaac) on the Very Large Telescope which covers the 2.9–4.1 μm region. HCN, CH and C2H2molecular bands, as well as SiC and MgS dust features are identified in the spectra. The equivalent width of C2H2molecular bands is larger at lower metallicity, thus PAHs might be abundant in AGB stars at low metallicity. We find no evidence that mass-loss rates depend on metallicity. Chemistry of carbon stars is affected by carbon production during the AGB phase rather than the metallicities. We argue that lower detection rate of PAHs from the interstellar medium of lower metal galaxies is caused by destruction of PAHs in the ISM by stronger UV radiation field.
PAH anions as carriers of the mid-IR emission bands in planetary nebulae
Authors: Szczerba Ryszard , Joblin Christine , Berné Olivier , Szyszka Cezary
Published: October 2008

We present results of the mid-IR spectra decomposition for planetary nebulae and compact H ii regions in our Galaxy and Magellanic Clouds. The striking correlation between the required PAH component with “7.7” μm band shifted to about 7.8 μm and electron densities of the modeled sources allows us to argue that this PAH component may be in fact PAH anions (PAH−).
On the inorganic carriers of the 21 micron emission feature in post-AGB stars
Authors: Zhang Ke , Jiang Biwei , Li Aigen
Published: October 2008

The mysterious 21 μm emission feature seen in only 12 C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen materials have been suggested as the carrier candidates while none of them has received general acceptance. We investigate the inorganic carrier candidates by applying the observational constraints of the feature strength and associated features. It is found that: (1) three candidates, TiC clusters, fullerenes with Ti impurity atoms, and SiS2, are not abundant enough to account for the emission power of the 21 μm band, (2) five candidates, doped-SiC, SiO2-mantled SiC dust, carbon and silicon mixtures, Fe2O3, and Fe3O4, all show associated features which are either not detected in the 21 μm sources or detected but with a much lower strength, and (3) FeO, which satisfies the abundance constraints, does not display any associated features which are not seen in the 21 μm sources. Moreover, FeO is more likely to survive in the C-rich environment than Fe2O3and Fe3O4. Thus FeO seems to be the most plausible one among the inorganic carrier candidates.
Dust properties in the circumstellar shells of evolved stars: Observational constraints from ISO and Spitzer infrared spectroscopy
Authors: García-Lario P. , Calderón J. V. Perea , García-Hernández D. A. , Stanghellini L. , Engels D. , Manchado A. , Davies J. E. , Villaver E. , Shaw R. A. , Bobrowsky M.
Published: October 2008

We present the results of a systematic analysis of the solid state features identified in the circumstellar environments of a large sample of evolved stars with ISO/SWS and Spitzer/IRS spectroscopy. The sample includes several hundred stars with a wide variety of progenitor masses evolving from the early AGB phase to the PN stage. Our observations are used to propose an evolutionary scheme in which the results obtained can be interpreted as a consequence of the nucleosynthesis processes that take place in this short phase of the stellar evolution, in particular the third dredge-up and hot bottom burning, which in turn are also strongly modulated by the stellar metallicity.
A survey of 3.3 micron PAH emission in planetary nebulae using FLITECAM
Authors: Smith Erin C. , McLean Ian S.
Published: October 2008

We have performed a study of 3.3 micron PAH emission in planetary nebulae using ground-based observations with FLITECAM, one of a suite of instruments designed for airborne astronomy aboard SOFIA, NASA's Stratospheric Observatory for Infrared Astronomy. The survey was performed on the Shane 3 meter telescope at Lick Observatory as part of the ground-based commissioning of the FLITECAM grism spectroscopy mode. Spectral resolution of R ~ 1700 was obtained with direct-ruled KRS-5 grisms. Targets included AGB stars and sources showing PAH emission in KAO, ISO or IRAS observations. Additionally, several oxygen-rich nebulae were observed in order to test methodology. Twenty objects were surveyed, of which 11 showed PAH emission. In objects exhibiting PAH emission, the relationship between the nebular C/O ratio and PAH equivalent width was found, showing a detectable PAH emission cutoff at a nebular C/O ratio of 0.65 ± 0.28. Selected objects with detected PAH emission were further investigated to trace PAH emission spectral variation within individual nebulae.
Molecules in nearby and primordial supernovae
Authors: Cherchneff Isabelle , Lilly Simon
Published: October 2008

We present new chemical models of supernova (SN) ejecta based on a chemical kinetic approach. We focus on the formation of inorganic and organic molecules including gas phase dust precursors, and consider zero-metallicity progenitor, massive supernovae and nearby core-collapse supernovae such as SN1987A. We find that both types are forming large amounts of molecules in their ejecta at times as early as 200 days after explosion. Upper limits on the dust formation budget are derived. Our results on dust precursors do not agree with existing studies on dust condensation in SN ejecta. We conclude that PMSNe could be the first non-primodial molecule providers in the early universe, ejecting up to 34% of their progenitor mass under molecular form to the pristine, local gas.
Organic compounds in galaxies
Authors: Onaka Takashi , Matsumoto Hiroko , Sakon Itsuki , Kaneda Hidehiro
Published: October 2008

The unidentified infrared (UIR) emission bands in the near- to mid-infrared are thought to originate from organic compounds in the interstellar medium. Recent space observations with Spitzer and AKARI have clearly revealed that the UIR bands are commonly seen in external galaxies, including elliptical galaxies, except for very metal-poor dwarf galaxies. They are also detected in extended structures of galaxies, such as extra-planar components and filaments produced by outflows, suggesting that the band carriers are ubiquitous organic compounds in galaxies. Since the UIR bands are prominent features in the infrared spectrum of galaxies and are linked to the star-formation activity, it is highly important to understand the nature, formation, processing, and destruction of the UIR band carriers in galaxies. While there is no systematic variation detected in the UIR spectrum in normal galaxies, significantly low values are derived for the ratio of the 7.7 μm to 11.2 μm bands in elliptical galaxies as well as in galaxies with low-luminosity AGNs compared to normal star-forming galaxies. Relatively low band ratios are also seen in the UIR band spectrum of extended structures in galaxies. If the same mechanism leads to the low band ratio, it would provide important information on the band carrier properties. It should also be noted that the band carriers are believed to be destroyed in a short time scale in environments where low band ratios are detected. The survival and supply processes in these environments are a key to understand the nature of the band carriers.
Diffuse interstellar bands in the Local Group: From the Milky Way, the Magellanic Clouds to the Andromeda galaxy
Authors: Cox N. L. J. , Cordiner M. A.
Published: October 2008

We report on recent developments in the study of diffuse interstellar bands in the Local Group galaxies. We present preliminary results on the detection of the 5780 Å DIB toward 17 targets in the vicinity of NGC 206 in M31.
Polycyclic aromatic hydrocarbons in elliptical galaxies
Authors: Kaneda Hidehiro , Onaka Takashi , Sakon Itsuki , Matsumoto Hiroko , Suzuki Toyoaki
Published: October 2008

We have observed 18 nearby dusty elliptical galaxies in the near- to far-infrared with Spitzer and AKARI. We have found that polycyclic aromatic hydrocarbons are present in 14 out of the 18 elliptical galaxies.
A 3-mm molecular line study of the Central Molecular Zone of the Galaxy
Authors: Jones Paul A. , Burton Michael G. , Lowe Vicki
Published: October 2008

We are studying the Central Molecular Zone (CMZ) in the inner few degrees around the Galactic Centre, by mapping multiple 3-mm molecular lines, with the 22-m Mopra telescope. During 2006, we covered a 5 × 5 arcmin2 area of the Sagittarius B2 molecular cloud complex (Jones et al. 2008). We find substantial differences in chemical and physical conditions within the complex. We show some results here of Principal Component Analysis (PCA) of line features in this Sgr B2 area. During 2007 we covered the larger region of longitude −0.2 to 0.9 deg. and latitude -0.20 to 0.12 deg., including Sgr A and Sgr B2, in the frequency range 85.3 to 91.3 GHz. This includes lines of C3H2, CH3CCH, HOCO+, SO, H13CN, H13CO+, SO, H13NC, C2H, HNCO, HCN, HCO+, HNC, HC3N, 13CS and N2H+.
ISM spectrum by cosmic dust?
Authors: Prevenslik Thomas V.
Published: October 2008

The interstellar medium (ISM) spectrum is usually explained by the response of dust particles (DPs) to the absorption of ultraviolet (UV) and visible (VIS) photons from nearby stars. With regard to the unidentified infrared (UIR) bands, the DPs are thought heated by UV and VIS photons to about 100 K thereby exciting the polycyclic aromatic hydrocarbons (PAHs). However, the UIR bands may be explained with the DPs at 2.7 K. To wit, the UIR bands form by the direct excitation of PAHs by infrared (IR) radiation induced from the absorption of cosmic microwave background (CMB) radiation in DPs by quantum electrodynamics (QED).