bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acceleration of ion recombination reaction rates in cold dark clouds through spontaneous polarization charge on CO ice mantles
Authors: Cassidy Andrew , Rosu-Finsen Alexander , Lasne Jérôme , McCoustra Martin R. S. , Field David 
Published: October 2020

AbstractWe propose a role for CO ice mantles in ion recombination reactions, and demonstrate how the subsequent fall in the degree of gas phase ionization decreases the time required for cloud collapse under gravity by a factor of 5-6. Experimental results demonstrate that CO films prepared at cryo-temperatures spontaneously harbour electric fields immediately upon growth. Using what is known from observations about prestellar cloud conditions in the ISM, we explain how this phenomenon can lead to an acceleration in ion recombination reaction rates. The result is a pathway for cloud collapse to occur before cloud disruption by supernova remnants.
Crystallisation of amorphous Mg-Fe silicates produced from microwave-dried sol-gels
Authors: Thompson Stephen P. , Herlihy Anna , Murray Claire A. , Baker Annabelle R. , Day Sarah J. 
Published: October 2020

AbstractAmorphous Mg-Fe silicates are produced from microwave-dried sol-gels and their thermal crystallisation is studied via in situ synchrotron X-ray powder diffraction. Mg-pyroxene crystallised to forsterite, enstatite and cristobalite. The inclusion of 10% Fe formed only forsterite at much higher temperature, while pure Mg-olivine crystallised at a lower temperature than Mg-pyroxene. Cristobalite is observed as a high-temperature crystallite in the pure-Mg compositions. Crystallisation activation energies are derived and discussed in relation to protoplanetary disks.
Chemical evolution of planetary materials in a dynamic solar nebula
Authors: Ciesla Fred J. 
Published: October 2020

AbstractAs observational facilities improve, providing new insights into the chemistry occurring in protoplanetary disks, it is important to develop more complete pictures of the processes that shapes the chemical evolution of materials during this stage of planet formation. Here we describe how primitive meteorites in our own Solar System can provide insights into the processes that shaped planetary materials early in their evolution around the Sun. In particular, we show how this leads us to expect protoplanetary disks to be very dynamic objects and what modeling and laboratory studies are needed to provide a more complete picture for the early chemical evolution that occurs for planetary systems.
Nitrogen bearing species in massive star forming regions
Authors: Awad Zainab , Shalabiea Osama M. 
Published: October 2020

AbstractRecent observations revealed that there is a difference in the spatial distribution of both nitrogen and oxygen bearing species towards massive star forming regions. These differences can be explained under different temperature regimes in hot cores. In this study, we attempt to model the chemistry of few nitrogen species; namely, vinyl cyanide (CH2CHCN), ethyl cyanide (CH3CH2CN), and formamide (NH2CHO), using gas-grain chemical models. A special attention is given to the role and efficiency of surface chemistry as it is suggested to play one of the main key roles in manufacturing these species.
Evolution of solids in planet forming disks: The interplay of experiments, simulations, and observations
Authors: Birnstiel T. 
Published: October 2020

AbstractCircumstellar dust analogues can be studied experimentally to determine their collisional behavior and their optical properties. These results affect simulations of circumstellar disks in various, substantial ways: Collision results determine how dust aggregates grow and how their aerodynamic properties change with time. This determines how solids move throughout the disk, how they accumulate, and how planetesimals might be formed. The optical properties determine the observational signature of these effects and allow us to constrain the spatial distribution of dust in disks, the sizes of the aggregates, as well as the temperature and optical depth of the dust emission. In this contribution, it is discussed how theoretical models and their predictions depend on laboratory results and what we learned about disks from high spatial resolution radio interferometry.
H2 photochemistry in interstellar ices:The formation of HCO in UV irradiated CO:H2 ice mixtures
Authors: Chuang K.-J. , Fedoseev G. , Qasim D. , Ioppolo S. , van Dishoeck E. F. , Jäger C. , Henning T. , Linnartz H. 
Published: October 2020

AbstractThe role of H2 in forming interstellar complex organics is still not clear due to the high activation energies required for “non-energetic” association reactions. In this work, we investigated the potential contribution of H2 to the hydrogenated species (HnNCO) formation on dust grains when the “energetic” processing is involved. The goal is to test whether an additional hydrogenation pathway is possible upon UV irradiation of a CO:H2 ice mixture. It is proposed that the electronically excited carbon monoxide (CO*) induced by UV-photons can react with a ground-state H2 to form HCO, ultimately enhancing the production of COMs in ice mantle.
Laboratory data in support of JWST observations of interstellar ices
Authors: Rachid Marina G. , van Scheltinga Jeroen Terwisscha , Koletzki Daniël , Marcandalli Giulia , van Dishoeck Ewine F. , Linnartz Harold 
Published: October 2020

AbstractExperimental and theoretical studies have shown that Complex Organic Molecules (COMs) can be formed on icy dusty grains in molecular clouds and protoplanetary disks. The number of astronomical detections of solid COMs, however, is very limited. With the upcoming launch of the James Webb Space Telescope (JWST) this should change, but in order to identify solid state features of COMs, accurate laboratory data are needed. Here we present high resolution (0.5 cm–1) infrared ice spectra of acetone (C3H6O) and methyl formate (HCOOCH3), two molecules already identified in astronomical gas phase surveys, whose interstellar synthesis is expected to follow solid state pathways.
Ab initio investigations of isopropyl cyanide reaction mechanisms and kinetics of formation on an icy grain model
Authors: Kerkeni Boutheïna 
Published: October 2020

AbstractIsopropyl-cyanide (iso-PrCN) was recently observed in Sagittarius B2 with an abundance higher than its straight-chain structure isomer (n-PrCN). Here we study theoretically by means of [UMP2(full)/aug-cc-pVTZ/Amber] a hybrid ab initio/molecular mechanics methodology, the routes leading to its formation on a formaldehyde doped water ice grain model of the interstellar medium. The reaction path and the energetics are calculated, the mechanism is found to be exothermic by ∼ 30 kcal/mol and the barrier is ∼ 70 kcal/mol. We use the CVT/ZCT semiclassical method to predict the kinetics of the reaction path starting from initially adsorbed HCN and CH2CHCH3 molecules colliding from the gas phase over the temperature range [100–500K].
Ion irradiation of astrophysically relevant frozen mixtures with INGMAR-T
Authors: Urso R. G. , Alemanno G. , Baklouti D. , Borondics F. , Djouadi Z. , d’Hendecourt L. , Maupin R. , Mivumbi O. , Brunetto R. 
Published: October 2020

AbstractLaboratory experiments are essential to support the interpretation of astronomical observations and space mission data. Here we present a new experimental setup to characterize in the Vis-MIR range in both reflection and transmission modes astrophysically-relevant frozen volatiles deposited at low temperature and exposed to ion bombardment.
H2 catalysis through superhydrogenation of interstellar polycyclic aromatic hydrocarbons
Authors: Simonsen Frederik Doktor S. , Jensen Pernille A. , Skov Anders W. , Jaganathan Rijutha , Thrower John D. , Hornekær Liv 
Published: October 2020

AbstractExperimental data showing superhydrogenation of neutral polycyclic aromatic hydrocarbons (PAHs) coronene, pentacene and pentacenequinone is presented. PAH monolayers were prepared on a highly oriented pyrolytic graphite surface and subsequently exposed to a beam of atomic hydrogen. The superhydrogenated PAH species were examined via temperature programmed desorption measurements. Stable intermediate superhydrogenation degrees as well as fully superhydrogenated species are observed and the initial reaction cross section for coronene has been determined.
Laboratory plasmas for high-energy astrophysics: A method to measure effective Landé g-factors
Authors: Giarrusso Marina 
Published: October 2020

AbstractEffective Landé g-factors (geff) are fundamental quantities in order to derive stellar magnetic field intensities. The determination of geff involves both total angular momenta and Landé g-factors of the transition levels. Theoretical g-factors are generally adopted, and the corresponding geff, often quite different from the one obtained in laboratory, affects the accuracy on magnetic field strength measurements. In this work we discuss a method to experimentally determine geff for highly ionised species, based on high resolution spectropolarimetry applied to Electron Cyclotron Resonance laboratory plasmas.
How to accurately model IR spectra of nanosized silicate grains
Authors: Mariñoso Guiu Joan , Macià Antoni , Bromley Stefan T. 
Published: October 2020

AbstractWe assess the accuracy of various computational methods for obtaining infrared (IR) spectra of nanosized silicate dust grains directly from their atomistic structure and atomic motions. First, IR spectra for a selection of small nanosilicate clusters with a range of sizes and chemical compositions are obtained within the harmonic oscillator approximation employing density functional theory (DFT) based quantum chemical calculations. To check if anharmonic effects play a significant role in the IR spectra of these nanoclusters, we further obtain their IR spectra from finite temperature DFT-based ab initio molecular dynamics (AIMD). Finally, we also study the effect of temperature on the broadening of the obtained IR spectra peaks in larger nanosilicate grains with a range of crystallinities. In this case, less computationally costly classical molecular dynamics simulations are necessary due to the large number of atoms involved. Generally, we find that although DFT-based methods are more accurate, surprisingly good IR spectra can also be obtained from classical molecular dynamics calculations.
Collision of centimeter-sized particles
Authors: Ghesquiere Pierre , Deguin Vincent , Gärtner Sabrina , Fraser Helen J. 
Published: October 2020

AbstractA characterisation of the collision properties between icy interstellar grains is crucial to understand planet formation. Here, we measure collision properties on a reference elastic system to evaluate the inelasticity of ice particles collisions. We propose upgrades to correct for some experimental biases and to investigate water evaporation as possible explanation for the energy loss during collision.
Probing Fault Frictional Properties During Afterslip Updip and Downdip of the 2017 Mw 7.3 Sarpol‐e Zahab Earthquake With Space Geodesy
Authors: Wang Kang , Bürgmann Roland 
Published: October 2020

AbstractWe use interferometric synthetic aperture radar (InSAR) data collected by the Sentinel‐1 mission to study the coseismic and postseismic deformation due to the 2017 Mw 7.3 Sarpol‐e Zahab earthquake that occurred near the Iran‐Iraq border in Northwest Zagros. We find that most of the coseismic moment release is between 15‐ and 21‐km depths, well beneath the boundary between the sedimentary cover and underlying basement. Data from four satellite tracks reveal robust postseismic deformation during ~12 months after the mainshock (from November 2017 to December 2018). Kinematic inversions show that the observed postseismic InSAR line‐of‐sight (LOS) displacements are well explained by oblique (thrust + dextral) afterslip both updip and downdip of the coseismic peak slip area. The dip angle of the shallow afterslip fault plane is found to be significantly smaller than that of the coseismic rupture, corresponding to a shallowly dipping detachment located near the base of the sediments or within the basement, depending on the thickness of the sedimentary cover, which is not well constrained over the epicentral area. Aftershocks during the same time period exhibit a similar temporal evolution as the InSAR time series, with most of aftershocks being located within and around the area of maximum surface deformation. The postseismic deformation data are consistent with stress‐driven afterslip models, assuming that the afterslip evolution is governed by rate‐strengthening friction. The inferred frictional properties updip and downdip of the coseismic rupture are significantly different, which likely reflect differences in fault zone material at different depths along the Zagros.
Alpha-2-macroglobulin from circulating exosome-like vesicles is increased in women with preterm pregnancies
Authors: Tronco Júlia A. , Ramos Bruna R. de A. , Bastos Natália M. , Alcântara Sérgio A. , da Silveira Juliano C. , da Silva Márcia G. 
Published: October 2020

AbstractPreterm labor (PTL) and Preterm Premature Rupture of Membranes (PPROM) impose substantial morbimortality on mothers and newborns. Exosomes act in intercellular communication carrying molecules involved in physiopathological processes. Little is known about exosomal proteins in prematurity. Our aim was to evaluate the protein expression of hemopexin, C1 inhibitor (C1INH) and alpha-2-macroglobulin (A2M) from circulating exosomes of women with PTL and PPROM. Plasma was obtained from PTL, PPROM, Term in labor and Term out of labor (T) patients, exosomes were isolated by ultracentrifugation, then lysed and the proteins quantified. Western Blot (WB) and Nanoparticle Tracking Analysis (NTA) were performed. Data were compared by Kruskal–Wallis, unpaired T-test and one-way ANOVA. WB and NTA confirmed exosome isolation (concentration: 4.3 × 1010 particles/ml ± 1.9 × 1010). There was no difference regarding hemopexin or C1INH expression between the groups. For A2M, the fold change was significantly higher on preterm groups when compared to term groups (1.07 ± 0.30 vs. 0.42 ± 0.17, p < 0.0001). Higher levels of A2M in circulating exosomes are linked to preterm pregnancies. sEV are strong candidates to intermediate maternal–fetal communication, carrying preterm labor-related immunomodulatory proteins.
Mitochondrial genome sequencing and phylogeny of Haemagogus albomaculatus, Haemagogus leucocelaenus, Haemagogus spegazzinii, and Haemagogus tropicalis (Diptera: Culicidae)
Authors: da Silva Fábio Silva , Cruz Ana Cecília Ribeiro , de Almeida Medeiros Daniele Barbosa , da Silva Sandro Patroca , Nunes Márcio Roberto Teixeira , Martins Lívia Carício , Chiang Jannifer Oliveira , da Silva Lemos Poliana , Cunha Gabriel Muricy , de Araujo Renato Freitas , de Oliveira Monteiro Hamilton Antônio , Nunes Neto Joaquim Pinto 
Published: October 2020

AbstractThe genus Haemagogus (Diptera: Culicidae) comprises species of great epidemiological relevance, involved in transmission cycles of the Yellow fever virus and other arboviruses in South America. So far, only Haemagogus janthinomys has complete mitochondrial sequences available. Given the unavailability of information related to aspects of the evolutionary biology and molecular taxonomy of this genus, we report here, the first sequencing of the mitogenomes of Haemagogus albomaculatus, Haemagogus leucocelaenus, Haemagogus spegazzinii, and Haemagogus tropicalis. The mitogenomes showed an average length of 15,038 bp, average AT content of 79.3%, positive AT-skews, negative GC-skews, and comprised 37 functional subunits (13 PCGs, 22 tRNA, and 02 rRNA). The PCGs showed ATN as start codon, TAA as stop codon, and signs of purifying selection. The tRNAs had the typical leaf clover structure, except tRNASer1. Phylogenetic analyzes of Bayesian inference and Maximum Likelihood, based on concatenated sequences from all 13 PCGs, produced identical topologies and strongly supported the monophyletic relationship between the Haemagogus and Conopostegus subgenera, and corroborated with the known taxonomic classification of the evaluated taxa, based on external morphological aspects. The information produced on the mitogenomes of the Haemagogus species evaluated here may be useful in carrying out future taxonomic and evolutionary studies of the genus.
The first reported case of the rare mitochondrial haplotype H4a1 in ancient Egypt
Authors: Drosou Konstantina , Collin Thomas C. , Freeman Peter J. , Loynes Robert , Freemont Tony 
Published: October 2020

AbstractTakabuti, was a female who lived in ancient Egypt during the 25th Dynasty, c.660 BCE. Her mummified remains were brought to Belfast, Northern Ireland, in 1834 and are currently displayed in the Ulster Museum. To gain insight into Takabuti’s ancestry, we used deep sampling of vertebral bone, under X-ray control, to obtain non-contaminated bone tissue from which we extracted ancient DNA (aDNA) using established protocols. We targeted the maternally inherited mitochondrial DNA (mtDNA), known to be highly informative for human ancestry, and identified 38 single nucleotide variants using next generation sequencing. The specific combination of these SNVs suggests that Takabuti belonged to mitochondrial haplogroup H4a1. Neither H4 nor H4a1 have been reported in ancient Egyptian samples, prior to this study. The modern distribution of H4a1 is rare and sporadic and has been identified in areas including the Canary Islands, southern Iberia and the Lebanon. H4a1 has also been reported in ancient samples from Bell Beaker and Unetice contexts in Germany, as well as Bronze Age Bulgaria. We believe that this is an important finding because first, it adds to the depth of knowledge about the distribution of the H4a1 haplogroup in existing mtDNA, thus creating a baseline for future occurrences of this haplogroup in ancient Egyptian remains. Second, it is of great importance for archaeological sciences, since a predominantly European haplogroup has been identified in an Egyptian individual in Southern Egypt, prior to the Roman and Greek influx (332BCE).
Qualification of Customised Medical Implants Produced by Ti6Al4V(ELI) Additive Manufacturing
Authors: du Preez W B , Booysen G J 
Published: October 2020

Although many cases of medical implants produced through additive manufacturing (AM) in Ti6Al4V have been reported in literature, most of these processes had not been qualified. To enable certification and commercialisation of medical implants and devices an ISO 13485:2016 quality management system was successfully implemented in the Centre for Rapid Prototyping and Manufacturing (CRPM) at the Central University of Technology, Free State in South Africa. This certification covers qualification of both design, development and production of patient specific custom made titanium implants, as well as preoperative models, jigs and cutting guides in nylon by means of AM and supports commercialisation.
With this quality management system as framework for ensuring the reliability and repeatability of the AM performed at the CRPM, the generation of data to validate the individual processes in the AM process chain was pursued. Sufficient research data has been produced and published to prove that medical implants produced through AM can fully comply with the international standards for material, physical, chemical and mechanical properties. In this paper the research performed towards the qualification of AM of Ti6Al4V medical implants is discussed. Examples are given of internationally leading work on utilising these implants in maxillofacial and orthopaedic surgeries.
LINEAR FRICTION WELDING – PROCESS CONTROL AND MACHINE TECHNOLOGY
Authors: PIOLLE N. 
Published: October 2020

Linear Friction Welding (LFW) is well adapted to produce titanium aircraft engine and structure parts, as an alternative to machining from solid, from forging or from electron beam welded blanks. The process can be described through a small number of mechanical variables: the amplitude and frequency of oscillation motion, the contact pressure and the axial displacement resulting of hot material flowing outside of the joint interface. Nonetheless, because of the high speeds and loads, the correct control and monitoring of linear friction welding requires special care on machine and tooling design.
The main principles of LFW machine design are described, with a special focus on the consistency between process quality requirements and machine characteristics: the static and dynamic machine behavior, the control system performance, the sensor technology and the tooling clamping solutions shall allow a good control of the weld parameters and an accurate monitoring of the physical phenomena at the joint interface.
Effects of strain rate on tensile deformation behaviour in Ti-6Al-4V at cryogenic temperature
Authors: Ji Min-Ki , Lee Min-Su , Hyun Yong-Taek , Jun Tea-Sung 
Published: October 2020

In this study, we investigated the effects of strain rate on tensile deformation behaviour in Ti-6Al-4V sheet at cryogenic temperature. X-ray diffraction (XRD) was used to identify the crystallographic orientation of rolled Ti-6Al-4V. A series of tensile tests were performed by constant strain rate method (CRS) with variable strain rates (i.e., on the order of 1x10-2 to 10-4•s-1). Liquid nitrogen (LN2) was used to mimic cryogenic environment, and for the thermal equilibrium the specimens were immersed in the vessel containing liquid nitrogen for ~10 minutes before tensile testing, and the temperature condition was continuously maintained during the testing. Microstructure and fracture surface was analysed by polarised light microscopy and scanning electron microscope (SEM). Electron backscatter diffraction (EBSD) was further used to characterise local deformation behaviour. Deformation twinning is occurred at cryogenic tempearture, which is rather different to the deformation at room temperature. It is thought that the twinning induced deformation behaviour may lead to a strength enhancement and a rate dependent ductility improvement.
Key words: Ti-6Al-4V, cryogenic, microstructure, deformation twinning, EBSD
Synthetic rutile derived titanium alloy development utilising the Metalysis Process and field assisted sintering technology
Authors: Graham Simon J. , Benson Lyndsey L. , Jackson Martin 
Published: October 2020

Utilising novel extraction and processing technologies allows for the realisation of an alternative titanium alloy production route, with many benefits over the traditional Kroll-based one. The route proposed has the potential to reduce the cost of titanium and offers the ability to create alloys which are difficult to make conventionally. It combines the Metalysis Process, an electrolytic metal extraction technique, with field assisted sintering technology (FAST), a rapid and effective solid-state sintering technique. The Metalysis Process reduces metal oxide powders directly into metal powders, which can then be consolidated using FAST. Using synthetic rutile (SR) as the feedstock, compared to pigment grade rutile and TiCl4, further reduces the cost of titanium produced via this route.
This research investigates the use of this route to create a range of pseudo-binary Ti-Fe alloys, by co-reducing SR with iron (III) oxide (Fe O ). Various techniques were used to analyse the feedstock, reduced alloy powders and consolidated material post-FAST to 23 determine chemistry and microstructure.