bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative study of 3.4 micron band features from carbon dust analogues obtained in pulsed plasmas
Authors: Cristina Gerber Ioana , Chiper Alina , Pohoata Valentin , Mihaila Ilarion , Topala Ionut 
Published: October 2020

AbstractSyntheses of carbon dust analogues are key experiments in laboratory astrophysics, as an approach to study some chemical and topological features of interplanetary and interstellar carbon dust. We report a comparative experimental study for carbon dust analogues obtained in (1) an atmospheric pressure dielectric barrier discharge (DBD), fed with helium – saturated hydrocarbons gas mixtures, (2) a low pressure radio frequency (RF) discharge and (3) a pulsed laser deposition (PLD) experiment with a Nd:YAG laser and a graphite target. The aliphatic –C–H stretching band, known as the 3.4 micron feature, as well as the CH2/CH3 ratio, the H/C ratio value and the physical appearance at microscopic scale, show a variability that is influenced by the synthesis method and the experimental parameters of each specific technique.
Gas-phase reactivity of CH3OH+OH down to 11.7 K: Astrophysical implications
Authors: Ocaña Antonio J. , Blázquez Sergio , González Daniel , Potapov Alexey , Ballesteros Bernabé , Canosa André , Antiñolo María , Albaladejo José , Jiménez Elena 
Published: October 2020

AbstractMethanol (CH3OH) and hydroxyl (OH) radicals are two species abundant in cold and dense molecular clouds which are important for the chemistry of the interstellar medium (ISM). CH3OH is a well-known starting point for the formation of more complex organic molecules (COMs) in these molecular clouds. Thus, the reactivity of CH3OH in the gas-phase with OH may play a crucial role in the formation of species as complex as prebiotic molecules in the ISM and reliable rate coefficients should be used in astrochemical models describing low temperature reaction networks.
Prebiotic molecules in interstellar space: Rotational spectroscopy and quantum chemistry
Authors: Puzzarini Cristina 
Published: October 2020

AbstractThe starting point for the development of any astrochemical model is the knowledge of whether a molecule is present in the astrophysical environment considered, with the astronomical observations of spectroscopic signatures providing the unequivocal proof of its presence. Among the goals of astrochemistry, the detection of potential prebiotic molecules in the interstellar medium and planetary atmospheres is fundamental in view of possibly understanding the origin of life. The detection of new molecules in space requires the spectroscopic signatures (mostly, rotational transition frequencies) to be accurately determined over a large frequency range. This task is more and more often the result of a synergic interplay of experiment and theory.
Photofragmentation of coronene cations
Authors: Panchagnula Sanjana , Bouwman Jordy , Kamer Jerry , Linnartz Harold , Tielens Alexander 
Published: October 2020

AbstractRecent laboratory studies have shown that PAH cations dehydrogenate to give charged molecules consisting of only carbon atoms. Our experiments using ion-trap time-of-flight mass spectrometry show that a key group of photodissociation fragments from the coronene cation $({{\rm{C}}_{24}}{\rm{H}}_{12}^ + )$ are carbon clusters of ${\rm{C}}_n^ +$ composition. Density functional theory calculations shed light onto potential dissociation pathways leading up to the main ${\rm{C}}_{11}^ +$ and ${\rm{C}}_{12}^ +$ clusters, and highlight the importance of pentagon formations in the carbon backbone of the precursor molecule in generating certain fragments.
Chemical dynamics in interstellar ice
Authors: Theulé Patrice 
Published: October 2020

AbstractChemistry in the interstellar medium is generally out-of-equilibrium and as such is kinetically controlled by a set of time-dependent equations, both for gas-phase chemistry and solid-state chemistry. The competition between the different possible reactions will determine toward which complex molecules the chemical network is driven to. The formation of complex molecules on the surface of the grains or in the ice mantle covering them is set by the diffusion-reaction equation, which is depending on temperature dependent reaction rate constants and diffusion coefficients. This paper shows how these two parameters can be experimentally determined by laboratory experiments. It also shows how the ice mantle reorganization plays an important role in the trapping and reactivity, which leads to the formation of complex organic molecules.
The Sun: Our own backyard plasma laboratory
Authors: Young Peter R. 
Published: October 2020

AbstractThe Sun's atmosphere increases in temperature from 6000 degrees at the surface to over a million degrees at heights of a few thousand kilometers. This surprising temperature increase is still an active area of scientific study, but is generally thought to be driven by the dynamics of the Sun's magnetic field. The combination of a 2-to-3 order of magnitude temperature range and a low plasma density makes the solar atmosphere perhaps the best natural laboratory for the study of ionized atoms. Atomic transitions at ultraviolet (UV) and X-ray wavelength regions generally show no optical depth effects, and the lines are not subject to the interstellar absorption that affects astronomical sources. Here I highlight the importance of atomic data to modeling UV and X-ray solar spectra, with a particular focus on the CHIANTI atomic database. Atomic data needs and problems are discussed and future solar mission concepts presented.
Infrared spectra of complex organic molecules in astronomically relevant ice matrices
Authors: Terwisscha van Scheltinga J. , Ligterink N. F. W. , Boogert A. C. A. , van Dishoeck E. F. , Linnartz H. 
Published: October 2020

AbstractThe identification of complex organic molecules, COMs, in inter- and circumstellar gas phase environments is steadily increasing. The formation of such COMs takes largely place on the icy dust grains, as has been shown in recent laboratory studies. Until now solid state features of smaller molecular species have been directly identified in these environments. The presented work on acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and dimethyl ether (CH3OCH3) in different astronomically relevant ice environments and for temperatures in the range 15 to 160 Kelvin, provides the necessary tools to guide or interpret astronomical observations, specifically for upcoming James Webb Space Telescope observations.
Planet forming disks, debris disks and the Solar System
Authors: Kamp Inga 
Published: October 2020

AbstractVLT instruments and ALMA with their high spatial resolution have revolutionized in the past five years our view and understanding of how disks turn into planetary systems. This talk will briefly outline our current understanding of the physical processes occurring and chemical composition evolving as these disks turn into debris disks and eventually planetary systems like our own solar system. I will especially focus on the synergy between disk structure/evolution modeling and astrochemical laboratory/theoretical work to highlight the most recent advances, and open questions such as (1) how much of the chemical composition in disks is inherited from molecular clouds, (2) the relevance of snowlines for planet formation, and (3) what is the origin of the gas in debris disks and what can we learn from it. For each of the three, I will outline briefly how the combination of theory/lab astrochemistry, astrophysical models and observations are required to advance our understanding.
Formation of complex organic molecules in astrophysical environments: Sugars and derivatives
Authors: Nuevo Michel , Cooper George , Saunders John M. , Buffo Christina E. , Sandford Scott A. 
Published: October 2020

AbstractCarbonaceous meteorites contain a large variety of complex organic molecules, including amino acids, nucleobases, sugar derivatives, amphiphiles, and other compounds of astrobiological interest. Photoprocessing of ices condensed on cold grains with ultraviolet (UV) photons was proposed as an efficient way to form such complex organics in astrophysical environments. This hypothesis was confirmed by laboratory experiments simulating photo-irradiation of ices containing H2O, CH3OH, CO, CO2, CH4, H2CO, NH3, HCN, etc., condensed on cold (~10–80 K) substrates. These experiments resulted in the formation of amino acids, nucleobases, sugar derivatives, amphiphilic compounds, and other organics comparable to those identified in carbonaceous meteorites. This work presents results for the formation of sugars, sugar alcohols, sugar acids, and their deoxy variants from the UV irradiation of ices containing H2O and CH3OH in relative proportions 2:1, and their comparison with meteoritic data. The formation mechanisms of these compounds and the astrobiological implications are also discussed.
Tracing the physical conditions of planet formation with molecular excitation
Authors: Teague Richard 
Published: October 2020

AbstractUnderstanding the physical structure of the planet formation environment, the protoplanetary disk, is essential for the interpretation of high resolution observations of the dust and future observations of the magnetic field structure. Observations of multiple transitions of molecular species offers a unique view of the underlying physical structure through excitation analyses. Here we describe a new method to extract high-resolution spectra from low-resolution observations, then provide two case studies of how molecular excitation analyses were used to constrain the physical structure in TW Hya, the closest protoplanetary disk to Earth.
Microscopic simulations of laboratory and interstellar ice structure and chemistry
Authors: Garrod Robin T. , Clements Aspen R. 
Published: October 2020

AbstractWe describe recent simulations of interstellar and laboratory ices using the 3-D, off-lattice microscopic Monte Carlo kinetics model MIMICK. The simulations indicate that interstellar ices are capable of achieving porous structures, dependent on physical conditions. In some cases, such structures may be filled as they are formed, by mobile/volatile species such as H2 that become trapped in those structures. Simulations of laboratory water-ice deposition using MIMICK suggest that an additional non-thermal diffusion mechanism is required to reproduce the high degree of porosity achieved for experimental ices at temperatures less than ~80 K. This mechanism is related to the deposition process itself. Simulations of temperature-programmed desorption of mixed molecular ices are ongoing. The interstellar models have also recently been developed to incorporate a full gas-phase chemistry, coupled with the grain-surface chemistry.
Photochemistry vs. radiation chemistry of cosmic ice analogs
Authors: Mullikin Ella , Hay Aurland , Anderson Hannah , O’Hern Natalie , Arumainayagam Chris 
Published: October 2020

AbstractWhile gas-phase reactions and surface reactions on bare carbonaceous or siliceous dust grains contribute to cosmic chemistry, the energetic processing of cosmic ices via photochemistry and radiation chemistry is thought to be the dominant mechanism for the cosmic synthesis of prebiotic molecules. Because most previous laboratory astrochemical studies have used light sources that produce >10 eV photons and are, therefore, capable of ionizing cosmic ice analogs, discerning the role of photochemistry vs. radiation chemistry in astrochemistry is challenging. By using a source whose photon energy does not exceed 8 eV, we have studied ammonia and methanol cosmic ice reactions attributable solely to photochemistry. We compare these results to those obtained in the same ultrahigh vacuum chamber with 1 keV electrons which instead initiate radiation chemistry in cosmic ice analogs.
The Titan haze simulation experiment: Investigating Titan’s low-temperature atmospheric chemistry in a pulsed plasma jet expansion
Authors: O’Brien Ella Sciamma , Raymond Alexander W. , Dubois David , Mazur Eric , Salama Farid 
Published: October 2020

AbstractThe Titan Haze Simulation (THS) experiment is a unique experimental platform that allows to simulate Titan’s complex atmospheric chemistry at low Titan-like temperature by generating a plasma discharge in the stream of a plasma jet expansion. Both gas and solid phase products are generated and can be analyzed using different in-situ and ex-situ diagnostics. Here, we present an overall description of the work accomplished with the THS in the last 10 years, our current research efforts, and the important implications for the analysis of Cassini’s returned data and preparation for future Titan missions.
The Belgian Repository of fundamental Atomic data and Stellar Spectra (BRASS)
Authors: Laverick M. , Lobel A. , Royer P. , Merle T. , Martayan C. , van Hoof P. , Van der Swaelmen M. , David M. , Hensberge H. , Thienpont E. 
Published: October 2020

AbstractThe Belgian Repository of fundamental Atomic data and Stellar Spectra (BRASS) aims to provide one of the largest systematic and homogeneous quality assessment to date of literature atomic data required for stellar spectroscopy. By comparing state-of-the-art synthetic spectrum calculations with extremely high-quality observed benchmark spectra, we have critically evaluated fundamental atomic data, such as line wavelengths and oscillator strengths, for thousands of astrophysically-relevant transitions found in the literature and across several major atomic data repositories. These proceedings provide a short overview of the BRASS project to date, highlighting our recent efforts to investigate and quality-assess the atomic literature data pertaining to over a thousand atomic transitions present in FGK-type stellar spectra. BRASS provides all quality assessed data, theoretical spectra, and observed spectra in a new interactive database under development at brass.sdf.org.
Modelling the properties of interstellar dust using the Si K-edge
Authors: Zeegers Sascha , Costantini Elisa , Rogantini Daniele , Vries Cor de , Mutschke Harald , Groot Frank de , Tielens Alexander 
Published: October 2020

AbstractThe properties of interstellar dust (ID) can be studied in great detail by making use of X-ray spectroscopy techniques. The radiation of X-rays sources is scattered and absorbed by dust grains in the interstellar medium. The X-ray band is especially suitable to study silicates - one of the main components of ID -since it contains the absorption edges of Si, Mg, O and Fe. In the Galaxy, we can use absorption features in the spectra of X-ray binaries to study the size distribution, composition and crystalline structure of grains. In order to derive these properties, it is necessary to acquire a database of detailed extinction cross sections models, that reflects the composition of the dust in the interstellar medium. We present the extinction profiles of a set of newly acquired measurements of 14 dust analogues at the Soleil Synchrotron facility in Paris, where we focus on silicates and the Si-K edge in particular, which is modelled with unprecedented accuracy. These models are used to analyse ID in the dense environments of the Galaxy.
Deuteration of C60 on a highly oriented pyrolytic graphite surface
Authors: Pantazidis G. , Scheffler M. , Simonsen F. D. S. , Cassidy A. , Jensen P. A. , Hornekær L. , Thrower J. D. 
Published: October 2020

AbstractReactions on carbonaceous surfaces play an important role in processes such as H2 formation in the interstellar medium. We have investigated the adsorption of C2 molecules on a highly oriented pyrolytic graphite (HOPG) surface and then exposed them to a beam of deuterium atoms in order to investigate the formation of deuterated fullerenes. Scanning tunneling microscopy (STM) was used to probe the adsorbed molecules and their deuteration. Deuteration of C2 films results in increased thermal stability of the film, relative to films of pristine C2, along with an evolution towards higher deuterated species. The STM data provide confirmatory evidence for the formation of deuterated fullerene species.
Underground nuclear astrophysics experiment JUNA in China
Authors: WeiPing LIU , ZhiHong LI , JiangJun HE , XiaoDong TANG , Gang LIAN , Zhu An , JianJun Chang , LiHua Chen , Han Chen , QingHao Chen , XiongJun Chen , ZhiJun Chen , BaoQun Cui , XianChao Du , ChangBo Fu , Lin Gan , Bing Guo , GuoZhu He , Alexander Heger , SuQing Hou , HanXiong Huang , Ning Huang , BaoLu Jia , LiYang Jiang , Shigeru Kubono , JianMin Li , KuoAng Li , Tao Li , YunJu Li , Maria Lugaro , XiaoBing Luo , HongYi Ma , ShaoBo Ma , DongMing Mei , YongZhong Qian , JiuChang Qin , Jie Ren , YangPing Shen , Jun Su , LiangTing Sun , WanPeng Tan , Isao Tanihata , Shuo Wang , Peng Wang , YouBao Wang , Qi Wu , ShiWei Xu , ShengQuan Yan , LiTao Yang , Yao Yang , XiangQing Yu , Qian Yue , Sheng Zeng , HuanYu Zhang , Hui Zhang , LiYong Zhang , NingTao Zhang , QiWei Zhang , Tao Zhang , XiaoPeng Zhang , XueZhen Zhang , ZiMing Zhang , Wei Zhao , Zuo Zhao , Chao Zhou 
Published: October 2020

AbstractUnderground Nuclear Astrophysics in China (JUNA) will take the advantage of the ultra-low background in Jinping underground lab. High current accelerator with an ECR source and detectors were commissioned. JUNA plans to study directly a number of nuclear reactions important to hydrostatic stellar evolution at their relevant stellar energies. At the first period, JUNA aims at the direct measurements of 25Mg(p,γ)26 Al, 19F(p,α) 16 O, 13C(α, n) 16O and 12C(α,γ) 16O near the Gamow window. The current progress of JUNA will be given.
Laboratory astrophysics for the interpretation of stellar spectra
Authors: Heiter Ulrike 
Published: October 2020

AbstractHigh-resolution stellar spectra are important tools for studying the chemical evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Large amounts of data have been accumulating, in particular in the optical and infrared wavelength regions. The observed spectral lines are interpreted using model spectra that are calculated based on transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce high-quality experimental and theoretical atomic data for the relevant transitions. We give examples for the precision with which the chemical composition of stars observed by different surveys can be determined, and discuss future needs from laboratory astrophysics.
Brittle Deformation of Carbonated Peridotite—Insights From Listvenites of the Samail Ophiolite (Oman Drilling Project Hole BT1B)
Authors: Menzel Manuel D. , Urai Janos L. , de Obeso Juan Carlos , Kotowski Alissa , Manning Craig E. , Kelemen Peter B. , Kettermann Michael , Jesus Ana P. , Harigane Yumiko ,   the Oman Drilling Project Phase 1 Science Team
Published: October 2020

AbstractHole BT1B of the Oman Drilling Project provides a continuous sampling from listvenite into the metamorphic sole that preserves the deformation, hydration, and carbonation processes of oceanic mantle peridotite at the base of the Samail ophiolite, Oman. We present evidence of multistage brittle deformation in listvenites and serpentinites based on field observations, visual core logging and petrography. About 10 vol% of listvenite and serpentinite in Hole BT1B is composed of cataclasite bands. Cataclasites contain lithic clasts of listvenite with spheroidal, zoned magnesite and quartz, and fragments of chalcedony‐carbonate veins that elsewhere crosscut listvenite—showing that cataclasis postdates listvenite formation. Locally the cataclasites are reworked and cut by thin, sharp faults, pointing to repeated reactivation of brittle structures. SEM‐EDS mapping shows that cataclasis was related to dissolution of carbonate and/or silica cementation. Dolomite veins crosscut cataclasites and breccias, suggesting that part of the Ca gain in BT1B is related to late fluids after listvenite formation. These results indicate a multistage tectonic overprint after peridotite carbonation and listvenite formation, which may be related to the tectonic history of the deformed continental margin under the ophiolite. These relatively late brittle structures should be excluded when trying to understand the carbonation of peridotite to listvenite.
Dynamic Upwelling Beneath the Salton Trough Imaged With Teleseismic Attenuation Tomography
Authors: Byrnes Joseph S. , Bezada Maximiliano 
Published: October 2020

AbstractThe Salton Trough is one of the few regions on Earth where rifting is subaerial instead of submarine. We use the relative attenuation of teleseismic P phases recorded by the Salton Trough Seismic Imaging Project to investigate lithospheric and asthenospheric structures that form during extension. Map‐view analysis reveals stronger attenuation within the Salton Trough than in the adjacent provinces. We then construct tomographic models for variations in seismic attenuation with depth to discriminate between crustal and mantle signals with a damped least squares approach and a Bayesian approach. Synthetic tests show that models from damped least squares significantly underestimate the strength of attenuation and cannot separate crustal and mantle signals even if the tomographic models are allowed to be discontinuous at the lithosphere‐asthenosphere boundary (LAB). We show that a Bayesian approach overcomes these problems when inverting the same synthetic data sets and that shallow and deep signals are more clearly separated when imposing a discontinuity. With greater than 95% confidence, the results reveal first, that attenuation occurs primarily beneath the LAB; second, that the width of the attenuative region is narrower than the rift at 120 km depth; and third, that the strength of attenuation requires that the attenuative feature represents a melting‐column similar to those beneath mid‐ocean ridges. The narrow width of the melting column below the volatile‐free solidus is inconsistent with models for passive upwelling, where flow is driven only by rifting. Instead, we attribute the generation of incipient oceanic crust to mantle upwelling focused by buoyancy into a narrow diapir.
Cannabinoid CB1 receptor agonist ACEA alleviates brain ischemia/reperfusion injury via CB1–Drp1 pathway
Authors: Yang Shuai , Hu Bin , Wang Zongming , Zhang Changming , Jiao Haosen , Mao Zhigang , Wei Liguang , Jia Ji , Zhao Jingling 
Published: October 2020

AbstractActivation of the cannabinoid CB1 receptor induces neuroprotection against brain ischemia/reperfusion injury (IRI); however, the mechanism is still unknown. In this study, we used oxygen-glucose deprivation/reoxygenation (OGD/R)-induced injury in neuronal cells and middle cerebral artery occlusion (MCAO)-induced brain IRI in rats to mimic ischemic brain injury, and hypothesized that the CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA) would protect ischemic neurons by inhibiting mitochondrial fission via dynamin-related protein 1 (Drp1). We found that OGD/R injury reduced cell viability and mitochondrial function, increased lactate dehydrogenase (LDH) release, and increased cell apoptosis, and mitochondrial fission. Notably, ACEA significantly abolished the OGD/R-induced neuronal injuries described above. Similarly, ACEA significantly reversed MCAO-induced increases in brain infarct volume, neuronal apoptosis and mitochondrial fission, leading to the recovery of neurological functions. The neuroprotective effects of ACEA were obviously blocked by coadministration of the CB1 receptor antagonist AM251 or by the upregulation of Drp1 expression, indicating that ACEA alleviates brain IRI via the CB1–Drp1 pathway. Our findings suggest that the CB1 receptor links aberrant mitochondrial fission to brain IRI, providing a new therapeutic target for brain IRI treatment.