bluuebunny/crossref_metadata_2025 huggingface dataset:
Astrophysically motivated laboratory measurements of deuterium reacting with isotopologues of H
Authors: Bowen K. P. , Hillenbrand P.-M. , Liévin J. , Urbain X. , Savin D. W.
Published: October 2020

H2D+and D2H+are important chemical tracers of prestellar cores due to their pure rotational spectra that can be excited at the ~20 K temperature of these environments. The use of these molecules as probes of prestellar cores requires understanding the chemistry that forms and destroys these molecules. Of the eight key reactions that have been identified (Albertssonet al. 2013), five are thought to be well understood. The remaining three are the isotope exchange reactions of atomic D with H$${ + \over 3}$$, H2D+, and D2H+. Semi-classical results differ from the classical Langevin calculations by an order of magnitude (Moyanoet al.2004). To resolve this discrepancy, we have carried out laboratory measurements for these three reactions. Absolute cross sections were measured using a dual-source, merged fast-beams apparatus for relative collision energies between ~10 meV to ~10 eV (Hillenbrandet al.2019). A semi-empirical model was developed incorporating high level quantum mechanicalab initiocalculations for the zero-point-energy-corrected potential energy barrier in order to generate thermal rate coefficients for astrochemical models. Based on our studies, we find that these three reactions proceed too slowly at prestellar core temperatures to play a significant role in the deuteration of H$${ + \over 3}$$isotopologues.
Interstellar polycyclic aromatic hydrocarbons: Spectroscopy, photofragmentation and photoproducts
Authors: Bouwman Jordy , Kamer Jerry , Castellanos Pablo , Bulak Michał , Panchagnula Sanjana , Zhen Junfeng , de Haas Arjen , Oomens Jos , Linnartz Harold , Tielens Alexander
Published: October 2020

Ubiquitous strong mid-infrared emission bands are observed towards many objects and are attributed to interstellar Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are ionized, or even dissociate, when exposed to strong interstellar radiation fields. By means of ion trap mass spectrometry, light-induced dissociation patterns of PAH cations are measured and the mid-infrared spectroscopic signatures of the parent ion and its dissociation products are characterized. These results are then combined with density functional theory (DFT) calculations to obtain insight into the dissociation characteristics of interstellar PAHs at a molecular level.
Investigation of rotational state-changing collisions of C2N− ions with helium
Authors: Franz Jan , Gianturco Francesco Antonio
Published: October 2020

The cross sections for rotational inelastic collisions between atoms and a molecular anion can be very large, if the anion has a dipole moment. This makes molecular anions very efficient in cooling atomic gases. We address rotational inelastic collisions of Helium atoms with the molecular anion C2N–. Here we present preliminary calculations of the potential energy surface.
Are SiO molecules the seed of silicate dust around evolved stars?
Authors: Jiang Biwei , Liu Jiaming
Published: October 2020

Silicate is the most popular dust species in the circumstellar envelope of evolved oxygen-rich stars, yet its seed particles have not been well identified. Among the candidates, corundum and SiO attract intense attention and study. SiO was suggested to be the seed particles in early 1980s and has received various supports as well as oppositions. In this work we investigate the relation of SiO maser and silicate dust emission powers. With both our own observation by using the PMO/Delingha 13.7-m telescope and the archival data, a sample is assembled of 21 SiO v=1, J=2-1 sources and 28 SiO v=1, J=1-0 sources that exhibit silicate emission features in the ISO/SWS spectrum. The analysis of their SiO maser and silicate emission power shows a moderate correlation, which agrees with the idea that SiO molecules are the seed nuclei of silicate dust.
Nanoscale structure of amorphous solid water: What determines the porosity in ASW?
Authors: Gärtner Sabrina , Headen Thomas F. , Youngs Tristan G. A. , Hill Catherine R. , Pascual Natalia , Auriacombe Olivier , Ioppolo Sergio , Loerting Thomas , Bowron Daniel T. , Fraser Helen J.
Published: October 2020

The pore structure of vapour deposited ASW is poorly understood, despite its importance to fundamental processes such as grain chemistry, cooling of star forming regions, and planet formation. We studied structural changes of vapour deposited D2O on intra-molecular to 30 nm length scales at temperatures ranging from 18 to 180 K and observed enhanced mobility from 100 to 150 K. An Arrhenius type model describes the loss of surface area and porosity with a common set of kinetic parameters. The low activation energy (428 K) is commensurate with van der Waals forces between nm-scale substructures in the ice. Our findings imply that water porosity will always change with time, even at low temperatures.
Benchmarked atomic data for astrophysics
Authors: Del Zanna Giulio
Published: October 2020

The recent calculations of atomic data for ions of astrophysical interest are reviewed with a focus on work performed in Cambridge. The calculations have been benchmarked against high-resolution laboratory and astrophysical spectra. A framework for assessing uncertainties in atomic data has also been developed. Long-standing discrepancies in predicted spectral line intensities have been resolved, and a significant number of levels in coronal ions have finally been identified, improving the modelling of the extreme-ultraviolet and soft X-ray spectral regions. Recent improvements based on collisional-radiative modelling are presented. They are relevant for the modelling of satellite lines in the X-rays and for solving the long-standing problems in the chromosphere-corona transition in stellar atmospheres.
On the correlation of the abundances of HNCO and NH2CHO: Advantages of solid para-H2 to study astrochemical H-atom addition and abstraction reactions
Authors: Tarczay György , Haupa Karolina , Lee Yuan-Pern
Published: October 2020

In dense interstellar clouds that are shielded from high-energy radiation (e.g., UV photons or cosmic rays), H-atom addition and abstraction reactions that take place on grain surfaces play principal roles in the synthesis or decomposition of complex organic molecules (COMs). These reactions are extensively investigated with laboratory experiments by bombarding astrophysical analogue ices with a beam of low-temperature H atoms. Here we demonstrate that, although 2-4 K solid para-H2 does not represent a typical environment of the surface of interstellar grains, para-H2 matrix isolation combined with IR spectroscopy is a complementary tool to sensitively detect astrochemical hydrogenation and dehydrogenation processes.
Behaviour of radicals on interstellar dust analogues
Authors: Watanabe Naoki
Published: October 2020

Surface reactions of radicals play important roles in the formation of complex molecules on interstellar dust grains. Under interstellar conditions, because the coverage of adsorbates on dust is significantly low, surface reactions are often limited by precedent processes, namely, the adsorption and diffusion of reactants. Therefore, to appropriately incorporate dust surface reactions into chemical models, information on the adsorption and diffusion of radicals is crucial. However, it is not easy to follow the behaviour of radicals on surfaces by conventional experimental methods. To monitor radicals on interstellar dust analogues, we have recently succeeded in applying a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods. In this paper, we briefly review our recent experiments for clarifying radical behaviour on water ice, pure solid CO and diamond-like carbon.
The chemistry of episodic accretion
Authors: Rab C. , Elbakyan V. , Vorobyov E. , Postel A. , Güdel M. , Dionatos O. , Audard M. , Kamp I. , Thi W.-F. , Woitke P.
Published: October 2020

Episodic accretion is an important process in the evolution of young stars and their surroundings. A consequence of an episodic accretion event is a luminosity burst, which heats the protostellar environment and has a long lasting impact on the chemical evolution of the disk and envelope of young stars. We present a new model for the chemistry of episodic accretion based on the 2D radiation thermo-chemical disk code ProDiMo. We discuss the impact of an episodic accretion burst on the chemical evolution of CO and its observables. Furthermore we present a model for the outbursting source V883 Ori where we fitted available observational data to get an accurate physical structure that allows for a detailed study of the chemistry.
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

We 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

Amorphous 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

As 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

Recent 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

Circumstellar 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

The 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

Experimental 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

Isopropyl-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

Laboratory 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

Experimental 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

Effective 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

We 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

A 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.
The Future of Laboratory Astrophysics
Authors: Salama Farid
Published: October 2020

A Round Table discussion on the future of Laboratory Astrophysics and the role of IAU Commission B5 was held on the fourth day of the conference to discuss how the IAU Laboratory Astrophysics Commission (B5) can best support the astronomy community and help promote laboratory astrophysics.
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

We 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

Preterm 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

The 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

Takabuti, 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).
Unveiling the mechanism of rare earth doping to optimize the optical performance of the CsPbBr3 perovskite
Authors: He Lingjun , Meng Junling , Feng Jing , Liu Xiaojuan , Zhang Hongjie
Published: October 2020

The types of electronic transitions in the lanthanide-activated CsPbBr3:RE family.
Highly enantioselective 1,6-addition of dienolates to coumarins and chromones through N-heterocyclic carbene catalysis
Authors: Liu Qiang , Wang Zhi-Xiang , Chen Xiang-Yu
Published: October 2020

An efficient protocol employing NHC-organocatalysis in asymmetric γ,δ-difunctionalization of cyanocoumarins and nitrochromonesviaa 1,6-addition of dienolates is established.
Total and formal syntheses of fostriecin
Authors: Dong Gao , Li Bohui , O'Doherty George A.
Published: October 2020

Two formal syntheses and one total synthesis of fostriecin (1) have been achieved, as well as, the synthesis of its related congener dihydro-dephospho-fostriecin.
Temperature effects on the C–H symmetric stretching vibrational frequencies of guest hydrocarbon molecules in 512, 51262 and 51264 cages of sI and sII clathrate hydrates
Authors: Fuseya Go , Takeya Satoshi , Hachikubo Akihiro
Published: October 2020

Temperature effects on the C–H symmetric stretch of hydrocarbons in various cages of sI and sII clathrate hydrates were observed.
Electrochemical performance of activated carbon fiber with hydrogen bond-induced high sulfur/nitrogen doping
Authors: Ruan Chaohui , Xie Yibing
Published: October 2020

Sulfur/nitrogen co-doped activated carbon fiber is prepared by thermal treatment of thiourea-bonded hydroxyl-rich carbon fiber, which achieves high doping level and electrochemical performance.
Justification of crystal stability and origin of transport properties in ternary half-Heusler ScPtBi
Authors: Majumder R. , Mitro S. K.
Published: October 2020

In Fermi surface topology, the flatness of the planes of hole like sheet atΓpoint is the main origin of the transport behaviors of ScPtBi cubic half-Heusler compound.
Production of pyrolytic oil from ULDP plastics using silica-alumina catalyst and used as fuel for DI diesel engine
Authors: Gopinath Soundararajan , Devan P. K. , Pitchandi K.
Published: October 2020

Lower acidity ratio of SA catalyst influences higher yield of ULDP oil and is suggested as a novel fuel for unmodified diesel engine.
Asymmetric aggregation-induced emission materials with double stable configurations toward promoted performance in non-doped organic light-emitting diodes
Authors: Li Jiatao , Yang Zhiwen , Feng Yaomiao , Su Zhifei , Qiu Zhipeng , Tan Ji-Hua , Chen Wen-Cheng , Zhang Maohua , Xu Zong-Xiang , Huo Yanping
Published: October 2020

Among three new AIE compounds, the two with double stable configurations performed much superior than the one adopting single configuration, when they were all used as the non-doped emission layers in OLEDs.
High quantum efficiency Ce:(Lu,Y)3(Al,Sc)2Al3O12 transparent ceramics with excellent thermal stability for high-power white LEDs/LDs
Authors: Ma Yuelong , Zhang Le , Zhou Tianyuan , Hou Chen , Kang Jian , Yang Shunshun , Xi Xiaoqian , Yuan Mingxing , Huang Jin , Wang Rui , Selim Farida A. , Li Ming , Wang Yun , Chen Hao
Published: October 2020

Transparent ceramics (TCs) with high quantum efficiency and excellent thermal stability are essential for the applications in high-power remote excitation white light-emitting diode or laser diode (LED/LD) lighting devices as color convertors.
Aluminium-enriched metal-poor stars buried in the inner Galaxy
Authors: Fernández-Trincado José G. , Beers Timothy C. , Minniti Dante , Tang Baitian , Villanova Sandro , Geisler Doug , Pérez-Villegas Angeles , Vieira Katherine
Published: October 2020

Stars with higher levels of aluminium and nitrogen enrichment are often key pieces in the chemical makeup of multiple populations in almost all globular clusters (GCs). There is also compelling observational evidence that some Galactic components could be partially built from dissipated GCs. The identification of such stars among metal-poor field stars may therefore provide insight into the composite nature of the Milky Way (MW) bulge and inner stellar halo, and could also reveal other chemical peculiarities. Here, based on APOGEE spectra, we report the discovery of 29 mildly metal-poor ([Fe/H] ≲ −0.7) stars with stellar atmospheres strongly enriched in aluminium (Al-rich stars: [Al/Fe] ≳ +0.5), well above the typical Galactic levels, located within the solar radius toward the bulge region, which lies in highly eccentric orbits (e ≳ 0.6). We find many similarities for almost all of the chemical species measured in this work with the chemical patterns of GCs, and therefore we propose that they have likely been dynamically ejected into the bulge and inner halo from GCs formed in situ and/or GCs formed in different progenitors of known merger events experienced by the MW, such as the Gaia-Sausage-Enceladus and/or Sequoia.
New research and development of titanium production and application in the CIS
Authors: Alexandrov A.
Published: October 2020

Review of the titanium industry in the CIS in research, production and application of titanium over the past four years. Plans and forecasts of development.
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.
Effect of Manufacturing Process of Master Alloy Powders on Homogeneity of Sintered Ti-5Al-1Fe by Blended Elemental Powder Metallurgy
Authors: Hayakawa Masashi , Fujii Hideki , Horikawa Matsuhide , Inoue Yosuke , Morita Masahiro
Published: October 2020

To narrow down the candidates of the alloying element powders for Ti-5Al-1Fe products manufactured with BE/PM, two master alloy powders, atomized spherical 5Al-1Fe and crushed-andground polyhedron 5Al-1Fe-4Ti ternary powders, were investigated with emphasizing on homogeneity of alloying elements, Al and Fe, in sintered Ti-5Al-1Fe. Intense Al segregation is recognized in the sintered specimen manufactured using 5Al-1Fe atomized powders, while strong segregation is not observed in the specimen manufactured using 5Al-1Fe-4Ti crushed-and-ground powders. Density of sintered specimen manufactured using 5Al-1Fe atomized powders is lower than that manufactured using 5Al-1Fe-4Ti crushed-and-ground powders. Al segregation and lower sintered density are probably caused by lower density of the powder substance, high flowability of spherical powders and phase constitutions some of which have low melting points. Those factors have to be taken into account to manufacture sintered titanium alloys with high homogeneity by BE/PM.
In situ synchrotron X-ray diffraction line-profile analysis of additively manufactured Ti−6Al−4V alloy under tensile deformation
Authors: Yamanaka K. , Kuroda A. , Ito M. , Mori M. , Shobu T. , Sato S. , Chiba A.
Published: October 2020

In this study, the tensile deformation behavior of an electron beam melted Ti−6Al−4V alloy was examined by in situ X-ray diffraction (XRD) line-profile analysis. The as-built Ti−6Al−4V alloy specimen showed a fine acicular microstructure that was produced through the decomposition of the α′-martensite during the post-melt exposure to high temperatures. Using high-energy synchrotron radiation, XRD line-profile analysis was successfully applied for examining the evolution of dislocation structures not only in the α-matrix but also in the nanosized, low-fraction β-phase precipitates located at the interfaces between the α-laths. The results indicated that the dislocation density was initially higher in the β-phase and an increased dislocation density with increasing applied tensile strain was quantitatively captured in each constitutive phase. It can be thus concluded that the EBM Ti−6Al−4V alloy undergoes a cooperative plastic deformation between the constituent phases in the duplex microstructure. These results also suggested that XRD line-profile analysis combined with highenergy synchrotron XRD measurements can be utilized as a powerful tool for characterizing duplex microstructures in titanium alloys.
Ti-6Al-4V microstructural orientation at different length scales as a function of scanning strategies in Electron Beam Melting in additive manufacturing
Authors: Agrawal Priyanka , Quintana Maria J. , Kenney Matt , Kumar Sabina , Saville Alec , Clarke Amy , Collins Peter C.
Published: October 2020

Additive manufacturing has been around for many years, yet the underlying physics of thermal gradients, local pressure environment, and other non-steady state manufacturing conditions are not fully understood. A Multi-University Research Initiative (MURI) is currently ongoing to measure liquid/solid and solid/solid interface stabilities in AM Ti-6Al-4V. Samples were produced with different beamscanning strategies in order to study the role of thermal gradients on the resulting microstructure. The motivation is to determine which beam-scanning strategy leads to desired grain size and texture. Orientation at different length scales (from mm to nm) can be quantified and compared with a combination of techniques including Precession Electron Diffraction (PED), Electron Backscatter Diffraction (EBSD) and Neutron diffraction. This new information will help predict properties of additively manufactured parts.
Laser polishing of titanium surfaces obtained by additive manufacturing process
Authors: Rosa Benoit , Hascoët Jean-Yves
Published: October 2020

Additive Manufacturing (AM) surfaces are composed by different textures and high roughness values which tend to limit its functionalities. Laser polishing process is enabling to smooth surfaces by material melting, change surface texture and decrease surface roughness (Sa). Based on a five axes machine, which consist of milling and Laser Metal Deposition (LMD) processes, the machine is additionally integrating laser polishing process on the same architecture. This paper aims at study laser polishing of laser metal deposition of titanium surfaces. LMD of titanium surfaces are composed by chaotic texture directly induced by the physical phenomenon of the process in use. Laser polishing process (LP) has an impact on the final surface regarding a multi-scale approach. The determined operating parameters and path strategy of laser polishing process decreases surface roughness by 78% and allow smoothing the initial chaotic texture. A polished surface roughness of 6.01 μm was obtained from an initial of 27.6μm.
Aerospace Titanium Alloy Melt Process Quality Improvements
Authors: Woodfield Andrew , Lemaitre Gérard
Published: October 2020

This Jet Engine Titanium Quality Committee (JETQC) paper describes industry quality improvements since 1990. Quality refers to freedom from melt-related hard-alpha and high-density inclusions (HDI). JETQC, formed under the auspices of the U.S. Federal Aviation Administration (FAA) following the Sioux City aircraft accident in 1989, is comprised of U.S., E.U. and Japanese aircraft engine manufacturers to address the quality of premium / rotor quality titanium alloy production. Titanium suppliers provide melt-related inclusion data. JETQC focuses on hard-alpha and HDI inclusion rates in premium quality (PQ) titanium alloy products for critical rotating aircraft engine applications. PQ materials typically are produced via triple vacuum arc re-melt (3XVAR) or hearth melt VAR (HMVAR) processes, but more recently, the Skull plus VAR (SVAR) process has been introduced. Hard-alpha rates have continued to decline over the last decade primarily for the HMVAR process. HDI rates declined in the early 90’s, but more recently the overall rate has stayed approximately constant with inclusions confined to the 3XVAR process. Combining the trends for both hard-alpha and HDIs, the HMVAR process has demonstrated in recent years to be higher quality compared with the 3XVAR process.
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.
Development of numerical tool for hybrid manufacturing process for titanium sheet metal forming
Authors: ACHOURI Mohamed
Published: October 2020

The use of titanium in the aerospace industry has grown considerably in recent years in conjunction with the development of composite aircraft. In this way, improving titanium forming has become an important issue for the industry, both for productivity objectives and the ability to deliver basic parts according to the needs imposed by aircraft delivery rates, as well as for cost objectives. Currently, hot forming of titanium parts can be achieved through two processes: Super-plastic forming (SPF) or Hot Forming (HF). The aeronautical industry wanted to develop an innovative process for the manufacture of titanium parts by coupling the HF and SPF processes in order to exploit the advantages of these two technologies. The development of a mixed HF / SPF process will thus not only improve the rates and allow better control of the quality of the formed parts (thickness homogeneity), but also, by allowing forming at lower temperatures, this hybrid process presents a large interest at the energy plan. The study was devoted to the development of a hybrid HF/SPF process, carried out at a common temperature, allowing the “pre-forming” of the part in HF mode and the “calibration” of the part in SPF mode, while respecting a global cycle time compatible with the objectives of the aerospace industry and guaranteeing the quality expected for the final complex part. Improving the performance of the final part requires a development of numerical simulation tool of the forming process. The available simulation tool (ABAQUS/ Standard) must be adapted to define the best simulation strategy according to the simulated parts; moreover, it remains imperative to determine the input data (material behavior laws of titanium alloys) adapted to the cases to be treated (strain rate and process temperature).
Controlling of mechanical property in additive manufactured porous titanium by structural control and alloying for bone substitutes
Authors: Ueda Masato , Ikeda Masahiko
Published: October 2020

Mechanical properties of metallic materials can be controlled by not only alloy design but also constructing appropriate structure. A porous material with adequate pore structure showing appropriate mechanical properties has long been sought as the ideal bone substitute, because it exhibits low Young’s modulus and bone ingrowth. Additive manufacturing (AM) can produce metallic tailor-made products such as artificial bone, several joints etc. The purpose of this work was to control the mechanical property of porous Ti by controlling the porous structure. In addition, the characteristics of Ti-Zr-Fe alloys were also investigated as the materials for the AM. First, porous polylactic acid with rhombicuboctahedron-derived structure was prepared by a 3D printer to determine appropriated structure for bone substitutes. The compressive strength and Young’s modulus was strongly influenced by the minimum cross-sectional area fraction perpendicular to the loading direction. Then the porous Ti with similar structures were prepared by a laser AM. The strength and Young’s modulus were extremely low compared with the expected ones. Then Ti-xmass%Zr-1mass%Fe alloys (x=0, 5, 10) were prepared as the materials for the AM. Vickers hardness increased almost linearly with Zr content by solution hardening. Ideal bone substitutes would be produced by such structural design and alloying.
Oxidation of Ti–6Al–4V alloy between 450 and 600°C. Evolution of microstructure and mechanical properties
Authors: Poquillon Dominique , Parrens Coralie , Pugliara Alessandro , Perrais Maxime , Malard Benoit
Published: October 2020

Titanium alloys are widely used in many applications thanks to their good corrosion resistance and to their high specific modulus. However, at temperatures above 450°C, oxidation must be taken into account to improve life assessment of components. Especially for long-term exposures, oxidation leads to an oxide scale along with an oxygen enrichment in the metal below this oxide scale. In this study, the oxidation behaviour of Ti– 6Al–4V is investigated between 450 and 600°C for a maximum duration of about 6800 h. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) are used to characterize the oxide layer and the layer affected by oxygen uptake. The local oxygen content is quantified. Vibration tests are performed to determine elastic properties on thin specimens with different thicknesses affected by oxygen enrichment. Creep tests are also carried out to quantify the influence of this oxygen uptake on viscoplastic behaviour. An oxygen-enriched zone occupying 5% of the cross-section of a specimen is sufficient to induce detectable changes in its creep behaviour.
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