bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shocks and UV radiation around low-mass protostars: the Herschel-PACS legacy
Authors: Karska Agata , Kaufman Michael J. , Kristensen Lars E. , van Dishoeck Ewine F. ,   WISH, DIGIT, and WILL teams
Published: September 2018

AbstractFar-infrared spectroscopy reveals gas cooling and its underlying heating due to physical processes taking place in the surroundings of protostars. These processes are reflected in both the chemistry and excitation of abundant molecular species. Here, we present the Herschel-PACS far-IR spectroscopy of 90 embedded low-mass protostars from the WISH (van Dishoeck et al. 2011), DIGIT (Green et al. 2013), and WILL surveys (Mottram et al. 2017). The 5 × 5 spectra covering the ∼50″ × 50″ field-of-view include rotational transitions of CO, H2O, and OH lines, as well as fine-structure [O I] and [C II] in the ∼50-200 μm range. The CO rotational temperatures are typically ∼300 K, with some sources showing additional components with temperatures as high as ∼1000 K. The H2O / CO and H2O / OH flux ratios are low compared to stationary shock models, suggesting that UV photons may dissociate some H2O and decrease its abundance. Comparison to C shock models illuminated by UV photons show a good agreement between the line emission and the models for pre-shock densities of 105 cm−3 and UV fields 0.1-10 times the interstellar value. The far-infrared molecular and atomic lines are the unique diagnostic of shocks and UV fields in deeply-embedded sources.
Fire from Ice - Massive Star Birth from Infrared Dark Clouds
Authors: Tan Jonathan C. 
Published: September 2018

AbstractI review massive star formation in our Galaxy, focussing on initial conditions in Infrared Dark Clouds (IRDCs), including the search for massive pre-stellar cores (PSCs), and modeling of later stages of massive protostars, i.e., hot molecular cores (HMCs). I highlight how developments in astrochemistry, coupled with rapidly improving theoretical/computational and observational capabilities are helping to improve our understanding of the complex process of massive star formation.
The chemical connection between 67P/C-G and IRAS 16293-2422
Authors: Drozdovskaya Maria Nikolayevna , van Dishoeck Ewine F. , Rubin Martin , Jørgensen Jes Kristian , Altwegg Kathrin 
Published: September 2018

AbstractThe chemical evolution of a star- and planet-forming system begins in the prestellar phase and proceeds across the subsequent evolutionary phases. The chemical trail from cores to protoplanetary disks to planetary embryos can be studied by comparing distant young protostars and comets in our Solar System. One particularly chemically rich system that is thought to be analogous to our own is the low-mass IRAS 16293-2422. ALMA-PILS observations have made the study of chemistry on the disk scales (<100 AU) of this system possible. Under the assumption that comets are pristine tracers of the outer parts of the innate protosolar disk, it is possible to compare the composition of our infant Solar System to that of IRAS 16293-2422. The Rosetta mission has yielded a wealth of unique in situ measurements on comet 67P/C-G, making it the best probe to date. Herein, the initial comparisons in terms of the chemical composition and isotopic ratios are summarized. Much work is still to be carried out in the future as the analysis of both of these data sets is still ongoing.
The Remarkable Molecular Content of Planetary Nebulae
Authors: Schmidt D. R. , Ziurys L. M. 
Published: September 2018

AbstractIn order to further define the molecular content of planetary nebulae (PNe), we have conducted searches for HCN, HCO+, HNC, and CCH at millimeter wavelengths in a sample of seventeen PNe using the new 12 m and Sub-Millimeter Telescopes of the Arizona Radio Observatory (ARO). HCN and HCO+ were identified in 75% of the PNe, with corresponding fractional abundances of f(HCN/H2) ~ 0.1-9.1 × 10−7 and f(HCO+/H2) ~ 0.04-7.4 × 10−7. HNC was subsequently identified in twelve PNe with f(HNC/H2) ~ 0.02-2.2 × 10−7. The [HCN]/[HNC] ratio was found to be ~1-8 in nebulae observed. CCH was also detected in eight PNe. The abundances for all molecules were found to remain relatively constant with nebular age across 10,000 years, in contrast to model predictions. They are also 10-100 greater than those observed in diffuse clouds, and suggest that molecular material from PNe seed the diffuse ISM.
Recent Progress in Laboratory Astrophysics Achieved with NASA Ames’ COSmIC Facility
Authors: Salama Farid , Sciamma-O’Brien Ella , Contreras Cesar S. , Bejaoui Salma 
Published: September 2018

AbstractWe describe the characteristics and the capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to generate, process and analyze interstellar, circumstellar and planetary analogs in the laboratory. COSmIC stands for ’Cosmic Simulation Chamber’ and is dedicated to the study of neutral and ionized molecules and nanoparticles under the low temperature and high vacuum conditions that are required to simulate various space environments such as diffuse interstellar clouds, circumstellar outflows and planetary atmospheres. Recent results obtained using COSmIC will be highlighted. In particular, the progress that has been achieved in the domain of the diffuse interstellar bands (DIBs) and in monitoring, in the laboratory, the formation of circumstellar dust grains and planetary atmosphere aerosols from their gas-phase molecular precursors. Plans for future laboratory experiments on interstellar and planetary molecules and grains will also be addressed, as well as the implications of the studies underway for astronomical observations and past and future space mission data analysis.
Forging Women's Substantive Representation: Intersectional Interests, Political Parity, and Pensions in Bolivia
Authors: Ewig Christina 
Published: September 2018

AbstractLacking tools to measure substantive representation, empirical research to date has determined women’s substantive representation by identifying “women’s interests” a priori, with little attention to differences across race, class, or other inequalities. To address this problem, I develop the concept of intersectional interests and a method for identifying these. Intersectional interests represent multiple perspectives and are forged through a process of political intersectionality that purposefully includes historically marginalized perspectives. These interests can be parsed into three types: expansionist, integrationist, and reconceived. Identification of intersectional interests requires, first, an inductive mapping of the differing women’s perspectives that exist in a specific context and then an examination of the political processes that lead to these new, redefined interests. I demonstrate the concept of intersectional interests and how to identify these in Bolivia, where I focus on the political process of forging reconceived intersectional interests in Bolivia’s political parity and pension reforms.
Facts and Fiction: The Myth of Suvaṇṇabhūmi Through the Thai and Burmese Looking Glass
Authors: Revire Nicolas 
Published: September 2018

AbstractMost scholars think that the generic name ‘Golden Land’ (Sanskrit, Suvarṇabhūmi; Pali, Suvaṇṇabhūmi) was first used by Indian traders as a vague designation for an extensive region beyond the subcontinent, presumably in Southeast Asia. Some Pali sources specifically link Suvaṇṇabhūmi with the introduction of Buddhism to the region. The locus classicus is the Sri Lankan Mahāvaṃsa chronicle (fifth century AD) which states that two monks, Soṇa and Uttara, were sent there for missionary activities in the time of King Asoka (third century BC). However, no Southeast Asian textual or epigraphic sources refer to this legend or to the Pali term Suvaṇṇabhūmi before the second millennium AD. Conversely, one may ask, what hard archaeological evidence is there for the advent of Buddhism in mainland Southeast Asia? This article re-examines the appropriation of the name Suvaṇṇabhūmi in Thailand and Burma for political and nationalist purposes and deconstructs the connotation of the term and what it has meant to whom, where, and when. It also carefully confronts the Buddhist literary evidence and earliest epigraphic and archaeological data, distinguishing material discoveries from legendary accounts, with special reference to the ancient Mon countries of Rāmaññadesa (lower Burma) and Dvāravatī(central Thailand).
Anticyclonic Eddy Edge Effects on Phytoplankton Communities and Particle Export in the Northern South China Sea
Authors: Wang Lei , Huang Bangqin , Laws Edward A. , Zhou Kuanbo , Liu Xin , Xie Yuyuan , Dai Minhan 
Published: September 2018

AbstractWe examined response of phytoplankton total chlorophyll a (TChl a) and community composition to three coherent anticyclonic eddies (ACEs) observed during a cruise to the northern South China Sea on 28 July to 7 August 2007. Photosynthetic pigments were measured to estimate the contribution of nine phytoplankton groups to TChl a. Although the water column‐integrated TChl a inventory in the upper 100 m was very similar among the three ACEs (17.6–18.9 mg/m2) we observed during the cruise, there were remarkable enhancements in biomasses at the eddy edges. TChl a inventory was 20.8 ± 3.0 mg/m2 at the edge, which was 33% or 60% higher than at the center and reference. The greatest enhancement of the TChl a at edge was attributed to haptophyte‐8, which was 1.6 and 2.2 times the analogous concentrations at the center and reference sites. The Prochlorococcus Chl a was ~50% greater at the edge relative to the reference and was intermediate at the center. Diatom Chl a at the edge was ~2.5 times the concentrations at the center and reference sites. The positive correlation between particulate organic carbon flux and haptophyte‐8 Chl a at the edge implied an important role of haptophyte‐8 in particle export productivity. It is interesting to note that there occurred higher fluxes of biogenic Si at the center of the ACEs due likely to lateral transport of diatoms from the edge. The phenomenon of higher TChl a at the edge but higher export at the center may have been the combined result of vertical convection and lateral transport within the eddies.
Emergent Wave Conversion as a Precursor to Shear Crack Initiation
Authors: Modiriasari Anahita , Pyrak‐Nolte Laura J. , Bobet Antonio 
Published: September 2018

AbstractGeophysical assessments of subsurface instability rely on a link between physical failure mechanisms and a geophysical measurement. Here a laboratory study demonstrates the emergence of a converted phase at the damage onset in limestone prior to failure from shear crack formation. Shear (S) to compressional (P) wave conversions arise from the presence of an array of disconnected microcracks and occur prior to the crack initiation detection from surface displacement measurements. The converted waves increase in amplitude with shear crack propagation until crack coalescence. The inception of the S to P wave converted phase supports the use of elastic wave conversions as an active diagnostic tool to detect the initiation and propagation of shear cracks.
Asymmetry in Stimulated Emission Polarization and Irregularity Evolution During Ionospheric Electron Gyroharmonic Heating
Authors: Fu H. Y. , Scales W. A. , Bernhardt P. A. , Jin Y. Q. , Briczinski S. J. 
Published: September 2018

AbstractThe first report is made of a holistic investigation of stimulated electromagnetic emission (SEE) during ionospheric electron gyroharmonic heating using a diagnostic approach at the High Frequency Active Auroral Research Program facility. The evolution of SEE polarization and plasma irregularity development near the third electron gyroharmonic 3fce is investigated, which provides new insights into SEE generation mechanisms by the associated parametric decay instabilities. New more complex SEE spectral line behavior is clearly observed for varying transmitter beam angles. New SEE spectral emissions are observed at ∼75 kHz when pumping below 3fce. The high‐frequency radar echoes and SEE polarimetry appear asymmetric for pumping above 3fce, which implies that the broad upshifted maximum spectral line formation involves plasma irregularities scattered by high‐frequency radar echoes. This has important implications for understanding artificial ionization layer generation during ionospheric modification.
Juno Constraints on the Formation of Jupiter's Magnetospheric Cushion Region
Authors: Gershman Daniel J. , DiBraccio Gina A. , Connerney John E. P. , Bagenal Fran , Kurth William S. , Hospodarsky George B. , Spalsbury Lori , Clark George , Ebert Robert W. , Wilson Robert J. , Levin Steve , Bolton Scott J. 
Published: September 2018

AbstractObservations by the Pioneer, Voyager, Ulysses, and Galileo spacecraft in Jupiter's dayside magnetosphere revealed a cushion region, where the magnetic field became increasingly dipolar and the 10‐hr periodicity associated with rotation of the magnetodisc was no longer visible. Focused observations at the dawn terminator by the Juno spacecraft provide critical constraints on the formation physics of the dayside cushion. We observe a persistent 10‐hr periodicity at dawn with only minor distortions of the field near the magnetopause boundary, indicating the absence of a systematic dawn cushion region. These data suggest that the dayside cushion is not formed via mass loss associated with magnetic reconnection along a localized X line but rather may be due to the gradual compression of the dawnside magnetic field as it rotates toward local noon.
Diversity of ENSO Events Unified by Convective Threshold Sea Surface Temperature: A Nonlinear ENSO Index
Authors: Williams Ian N. , Patricola Christina M. 
Published: September 2018

AbstractWe show that the well‐known failure of any single index to capture the diversity and extremes of El Niño‐Southern Oscillation (ENSO) results from the inability of existing indices to uniquely characterize the average longitude of deep convection in the Walker Circulation. We present a simple sea surface temperature (SST)‐based index of this longitude that compactly characterizes the different spatial patterns, or flavors of observed and projected ENSO events. It recovers the familiar global responses of temperature, precipitation, and tropical cyclones to ENSO and identifies historical extreme El Niño events. Despite its simplicity, the new longitude index describes the nonlinear relationship between the first two principal components of SST, and unlike previous indices, accounts for background SST changes associated with the seasonal cycle and climate change. The index reveals that extreme El Niño, El Niño Modoki, and La Niña events are projected to become more frequent in the future at the expense of neutral ENSO conditions.
Differential Impacts of 1.5 and 2 °C Warming on Extreme Events Over China Using Statistically Downscaled and Bias‐Corrected CESM Low‐Warming Experiment
Authors: Yang Yi , Tang Jianping , Wang Shuyu , Liu Gang 
Published: September 2018

AbstractUsing statistically downscaled and bias‐corrected CESM (Community Earth System Model) 11‐member ensemble, we investigate the changes in precipitation and temperature extremes over China in 1.5 and 2 °C warmer climates. Most regions will experience a significant increase in wet extreme indices accompanied by fewer consecutive dry days under both warming targets. An additional 0.5 °C warming may result in stronger increases in wet extreme indices over most subregions and weak decreases over North China, although the grid point‐level changes between the two scenarios are mostly nonsignificant. A robust increase in extreme high‐temperature events and TNn (the coldest night) is found across China at a 2 °C relative to 1.5 °C scenario. Compared to a 2 °C world, a 0.5 °C less warming avoids 32–34% of the increases in the frequency and intensity of temperature extremes in China, particularly over Northeast China.
Experimental Determination of Eutectic Liquid Compositions in the MgO‐SiO2System to the Lowermost Mantle Pressures
Authors: Ozawa Keisuke , Anzai Miyuki , Hirose Kei , Sinmyo Ryosuke , Tateno Shigehiko 
Published: September 2018

AbstractWe have performed melting experiments on the MgO‐SiO2binary system to 139 GPa in a diamond anvil cell. Both MgO‐MgSiO3and MgSiO3‐SiO2eutectic compositions were examined by textural/chemical characterizations of recovered samples. Results demonstrate that the MgO‐MgSiO3eutectic becomes more enriched in MgO with increasing pressure and is close in composition to Mg2SiO4at the core‐mantle boundary (CMB) pressure. On the other hand, the MgSiO3‐SiO2eutectic is more SiO2‐rich at higher pressure and exhibits SiO2/(MgO + SiO2) = 0.66 at the CMB. These have profound implications for a large‐scale compositional stratification possibly formed upon solidification of a magma ocean. The MgO‐MgSiO3eutectic liquid being more MgO‐rich than previously predicted suggests that only bridgmanite crystallizes up to 60 wt% solidification from a fully molten state of a pyrolitic lowermost mantle. In contrast, an SiO2layer may develop when melting/crystallization occurs in rocky objects with silica‐rich enstatite‐chondritic compositions.
Reconsidering Effective Elastic Thickness Estimates by Incorporating the Effect of Sediments: A Case Study for Europe
Authors: Kaban M. K. , Chen B. , Tesauro M. , Petrunin A. G. , El Khrepy S. , Al‐Arifi N. 
Published: September 2018

AbstractIn the present study we analyzed the influence of density heterogeneity in the sedimentary cover on estimates of the effective elastic thickness (EET) of the lithosphere based on a cross‐spectral analysis of gravity and topography data. The fan wavelet coherence technique was employed to calculate EET for most of Europe and adjoining southern mountain belts. We employed Bouguer gravity anomalies and topography corrected for the effect of density variations within sediments. Correcting for sediments considerably suppresses the effect of unexpressed subsurface loads and substantially reduces EET estimates in areas with negligible topography variations as it was demonstrated for North Europe and East European Platform. The results show a good correspondence between the EET patterns and tectonic fragmentation of Europe and better agree with independent estimates based on the strength model of the lithosphere. Therefore, considering of the effect of sediments is essential for correct determinations of EET in flat areas.
A Tenuous Lunar Ionosphere in the Geomagnetic Tail
Authors: Halekas J. S. , Poppe A. R. , Harada Y. , Bonnell J. W. , Ergun R. E. , McFadden J. P. 
Published: September 2018

AbstractWe utilize measurements of electron plasma frequency oscillations made by the two‐probe Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun mission to investigate the charged particle density in the lunar environment as the Moon passes through the Earth's geomagnetic tail. We find that the Moon possesses a tenuous ionosphere with an average density of ~0.1–0.3 cm−3, present at least 50% of the time in the geomagnetic tail, primarily confined to within a few thousand kilometers of the dayside of the Moon. The day‐night asymmetry and dawn‐dusk symmetry of the observed plasma suggests that photoionization of a neutral exosphere with dawn‐dusk symmetry produces the majority of the lunar‐derived plasma. The lunar plasma density commonly exceeds the ambient plasma density in the tail, allowing the presence of the lunar ionosphere to appreciably perturb the local plasma environment.
Permeability Evolution of a Cemented Volcanic Ash During Carbonation and CO2 Depressurization
Authors: Clark A. C. , MacFarlane J. , Vanorio T. 
Published: September 2018

AbstractThe presence of calcium‐cemented ash beds serving as caprocks in hydrothermal systems calls for the examination of any chemo‐mechanical processes that may undermine or enhance their sealing capacity. Understanding these processes provides new information regarding how to model time‐dependent observations associated with seismicity and/or deformation in volcanic areas. In addition, since these ash beds are inherently similar to ash‐based concrete, a bridge of knowledge can be built across disciplines in the earth sciences and engineering. This paper investigates how the permeability of a volcanic ash cemented with hydrated lime changes upon exposure to carbon dioxide (CO2) in humid and hydrous conditions relevant to natural or human‐driven processes such as those found in hydrothermal settings or near wellbores used for secondary oil recovery, CO2 plume geothermal energy, or carbon storage. We characterized samples by their permeability during carbonation and subsequent changes in pore pressure and confining pressure. Products from the reaction of CO2 with the cemented ash matrix reduced permeability and entrapped fluids. The regions within samples permeated with unreacted CO2 were susceptible to fracturing upon rapid depressurization, but only when the effective stress state was sufficiently low. Altogether, the results indicate that lime‐cemented volcanic ash beds are particularly suited to act as flow barriers to CO2‐rich fluids.
Observations of the Intermediate Water Exchange Between the South China Sea and the Pacific Ocean Deduced From Transient Tracer Measurements
Authors: Deng Hengxiang , Huang Peng , Tanhua Toste , Stöven Tim , Ke Hongwei , Guo Weidong , Wang Weimin , Cai Minggang 
Published: September 2018

AbstractThe South China Sea (SCS) is the largest semienclosed marginal sea in the western Pacific (WP) and connects to the west Pacific through the Luzon Strait (LU). In this study, we use the observation of transient tracer chlorofluorocarbon‐12 (CFC‐12) to calculate the ventilation time scales of the SCS, LU, and WP. The CFC‐12 and oxygen data are used together to identify the sandwiched structure vertically of the flows across the LU. The CFC‐12 and oxygen distributions reveal a pronounced decrease westward across the LU and a slight decrease southward in the transport of the SCS. The mean age gradient of the salinity minimum (Smin) water between the WP and the northern SCS could be a consequence of intensive mixing and entrainment of the inflow water from the WP. An expected difference in age between the LU and SSCS is verified to reflect the transit time for the given water layers in the SCS. Thus, a mean transit time of 77 ± 20 years is estimated for the intermediate water in the SCS interior.