bluuebunny/crossref_metadata_2025_split huggingface dataset:
The VLT-FLAMES Tarantula Survey
Authors: Vink Jorick S. , Evans C.J. , Bestenlehner J. , McEvoy C. , Ramírez-Agudelo O. , Sana H. , Schneider F. ,   VFTS
Published: July 2017

AbstractWe present a number of notable results from the VLT-FLAMES Tarantula Survey (VFTS), an ESO Large Program during which we obtained multi-epoch medium-resolution optical spectroscopy of a very large sample of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). This unprecedented data-set has enabled us to address some key questions regarding atmospheres and winds, as well as the evolution of (very) massive stars. Here we focus on O-type runaways, the width of the main sequence, and the mass-loss rates for (very) massive stars. We also provide indications for the presence of atop-heavyinitial mass function (IMF) in 30 Dor.
Pre-SN neutrino emissions from ONe cores in the progenitors of CCSNe
Authors: Kato Chinami , Yamada S. , Nagakura H. , Furusawa S. , Takahashi K. , Umeda H. , Yoshida T. , Ishidoshiro K. 
Published: July 2017

AbstractIn order to investigate the distinguishability about the progenitors of FeCCSNe and ECSNe, we calculate the luminosities and spectra of their pre-SN neutrinos and estimate the number of events at neutrino detectors.
Observations of Bright Massive Stars Using Small Size Telescopes
Authors: Beradze Sopia , Kochiashvili Nino 
Published: July 2017

AbstractThe size of a telescope determines goals and objects of observations. During the latest decades it becomes more and more difficult to get photometric data of bright stars because most of telescopes of small sizes do not operate already. But there are rather interesting questions connected to the properties and evolution ties between different types of massive stars. Multi-wavelength photometric data are needed for solution of some of them. We are presenting our observational plans of bright Massive X-ray binaries, WR and LBV stars using a small size telescope. All these stars, which are presented in the poster are observational targets of Sopia Beradze’s future PhD thesis. We already have got very interesting results on the reddening and possible future eruption of the massive hypergiant star P Cygni. Therefore, we decided to choose some additional interesting massive stars of different type for future observations. All Massive stars play an important role in the chemical evolution of galaxies because of they have very high mass loss - up to 10−4M⊙/a year. Our targets are on different evolutionary stages and three of them are the members of massive binaries. We plan to do UBVRI photometric observations of these stars using the 48 cm Cassegrain telescope of the Abastumani Astrophisical Observatory.
Massive Stars in M31
Authors: Lomax Jamie R. , Peters Matthew , Wisniewski John , Dalcanton Julianne , Williams Benjamin , Lutz Julie , Choi Yumi , Sigut Aaron 
Published: July 2017

AbstractMassive stars are intrinsically rare and therefore present a challenge to understand from a statistical perspective, especially within the Milky Way. We recently conducted follow-up observations to the Panchromatic Hubble Andromeda Treasury (PHAT) survey that were designed to detect more than 10,000 emission line stars, including WRs, by targeting regions in M31 previously known to host large numbers of young, massive clusters and very young stellar populations. Because of the existing PHAT data, we are able to derive an effective temperature, bolarimetric luminosity, and extinction for each of our detected stars. We report on preliminary results of the massive star population of our dataset and discuss how our results compare to previous studies of massive stars in M31.
ALMA Observation of Mass Loss from Massive Stars
Authors: Gunawan D. Y. A. Setia , Curé M. , Kanaan S. , Puls J. , Najarro F. , Sundqvist J. , Diez M. M. Rubio , Whyborn N. 
Published: July 2017

AbstractWe present a pilot study of using the Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum observations to constrain the density structure in the intermediate wind zone of massive stars, in which the wind is extremely sensitive to clumping.
Progenitors of binary black hole mergers detected by LIGO
Authors: Postnov Konstantin , Kuranov Alexander 
Published: July 2017

AbstractPossible formation mechanisms of massive close binary black holes that can merge in the Hubble time to produce powerful gravitational wave bursts detected during advanced LIGO O1 science run are briefly discussed. The pathways include the evolution from field low-metallicity massive binaries, the dynamical formation in globular clusters and primordial black holes. Low effective black hole spins inferred for LIGO GW150914 and LTV151012 events are discussed. Population synthesis calculations of the expected spin and chirp mass distributions from the standard field massive binary formation channel are presented for different metallicities (from zero-metal Population III stars up to solar metal abundance). We conclude that that merging binary black holes can contain systems from different formation channels, discrimination between which can be made with increasing statistics of mass and spin measurements from ongoing and future gravitational wave observations.
Reconstructing the Scene: New Views of Supernovae and Progenitors from the SNSPOL Project
Authors: Hoffman Jennifer L. , Williams G. Grant , Leonard Douglas C. , Bilinski Christopher , Dessart Luc , Huk Leah N. , Mauerhan Jon C. , Milne Peter , Porter Amber L. , Smith Nathan , Smith Paul S. 
Published: July 2017

AbstractBecause polarization encodes geometrical information about unresolved scattering regions, it provides a unique tool for analyzing the 3-D structures of supernovae (SNe) and their surroundings. SNe of all types exhibit time-dependent spectropolarimetric signatures produced primarily by electron scattering. These signatures reveal physical phenomena such as complex velocity structures, changing illumination patterns, and asymmetric morphologies within the ejecta and surrounding material. Interpreting changes in polarization over time yields unprecedentedly detailed information about supernovae, their progenitors, and their evolution.Begun in 2012, the SNSPOL Project continues to amass the largest database of time-dependent spectropolarimetric data on SNe. I present an overview of the project and its recent results. In the future, combining such data with interpretive radiative transfer models will further constrain explosion mechanisms and processes that shape SN ejecta, uncover new relationships among SN types, and probe the properties of progenitor winds and circumstellar material.
Core-Collape Supernova Progenitors: Light-Curve and Stellar-Evolution Models
Authors: Bersten Melina C. 
Published: July 2017

AbstractA very active area of research in the field of core-collapse supernovae (SNe) is the study of their progenitors and the links with different subtypes. Direct identification using pre- and post-SN images is a powerful method but it can only be applied to the most nearby events. An alternative method is the hydrodynamical modeling of SN light curves and expansion velocities, which can serve to characterize the progenitor (e.g. mass and radius) and the explosion itself (e.g. explosion energy and radioactive yields). This latter methodology is particularly powerful when combined with stellar evolution calculations. We review our current understanding of the properties of normal core-collapse SNe based chiefly on these two methods.
The supergiant O + O binary system HD 166734: a new study
Authors: Gosset E. , Mahy L. , Damerdji Y. , Nitschelm C. , Sana H. , Eenens P. , Nazé Y. 
Published: July 2017

AbstractWe present here a modern study of the radial velocity curve and of the photometric light curve of the very interesting supergiant O7.5If + O9I(f) binary system HD 166734. The physical parameters of the stars and the orbital parameters are carefully determined. We also perform the analysis of the observed X-ray light curve of this colliding-wind binary.
The very massive star content of the nuclear star clusters in NGC 5253
Authors: Smith Linda J. , Crowther Paul A. , Calzetti Daniela 
Published: July 2017

AbstractThe blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters. Calzetti et al. (2015) find that the two clusters have an age of 1 Myr, in contradiction to the age of 3–5 Myr inferred from the presence of Wolf-Rayet (W-R) spectral features. We use Hubble Space Telescope (HST) far-ultraviolet (FUV) and ground-based optical spectra to show that the cluster stellar features arise from very massive stars (VMS), with masses greater than 100 M⊙, at an age of 1–2 Myr. We discuss the implications of this and show that the very high ionizing flux can only be explained by VMS. We further discuss our findings in the context of VMS contributing to He ii λ1640 emission in high redshift galaxies, and emphasize that population synthesis models with upper mass cut-offs greater than 100 M⊙ are crucial for future studies of young massive clusters.
A high-contrast imaging survey of nearby red supergiants
Authors: Scicluna Peter , Siebenmorgen Ralf , Blommaert Joris , Kemper Francisca , Wesson Roger , Wolf Sebastian 
Published: July 2017

AbstractMass-loss in cool supergiants remains poorly understood, but is one of the key elements in their evolution towards exploding as supernovae. Some show evidence of asymmetric mass loss, discrete mass-ejections and outbursts, with seemingly little to distinguish them from more quiescent cases. To explore the prevalence of discrete ejections and companions we have conducted a high-constrast survey using near-infrared imaging and optical polarimetric imaging of nearby southern and equatorial red supergiants, using the extreme adaptive optics instrument SPHERE, which was designed to image planets around nearby stars. We present the initial results of this survey, including the detection of large (500 nm) dust grains in the ejecta of VY CMa and a candidate dusty torus aligned with the maser ring of VX Sgr. We briefly speculate on the consequences for our understanding of mass loss in these extreme stars.
Recent advances in non-LTE stellar atmosphere models
Authors: Sander Andreas A. C. 
Published: July 2017

AbstractIn the last decades, stellar atmosphere models have become a key tool in understanding massive stars. Applied for spectroscopic analysis, these models provide quantitative information on stellar wind properties as well as fundamental stellar parameters. The intricate non-LTE conditions in stellar winds dictate the development of adequate sophisticated model atmosphere codes. The increase in both, the computational power and our understanding of physical processes in stellar atmospheres, led to an increasing complexity in the models. As a result, codes emerged that can tackle a wide range of stellar and wind parameters.After a brief address of the fundamentals of stellar atmosphere modeling, the current stage of clumped and line-blanketed model atmospheres will be discussed. Finally, the path for the next generation of stellar atmosphere models will be outlined. Apart from discussing multi-dimensional approaches, I will emphasize on the coupling of hydrodynamics with a sophisticated treatment of the radiative transfer. This next generation of models will be able to predict wind parameters from first principles, which could open new doors for our understanding of the various facets of massive star physics, evolution, and death.
Radiation Hydrodynamical Models for Type I Superluminous Supernovae: Constraints on Progenitors and Explosion Mechanisms
Authors: Nomoto Ken’ichi , Tolstov Alexey , Sorokina Elena , Blinnikov Sergei , Bersten Melina , Suzuki Tomoharu 
Published: July 2017

AbstractThe physical origin of Type-I (hydrogen-less) superluminous supernovae (SLSNe-I), whose luminosities are 10 to 500 times higher than normal core-collapse supernovae, remains still unknown. Thanks to their brightness, SLSNe-I would be useful probes of distant Universe. For the power source of the light curves of SLSNe-I, radioactive-decays, magnetars, and circumstellar interactions have been proposed, although no definitive conclusions have been reached yet. Since most of light curve studies have been based on simplified semi-analytic models, we have constructed multi-color light curve models by means of detailed radiation hydrodynamical calculations for various mass of stars including very massive ones and large amount of mass loss. We compare the rising time, peak luminosity, width, and decline rate of the model light curves with observations of SLSNe-I and obtain constraints on their progenitors and explosion mechanisms. We particularly pay attention to the recently reported double peaks of the light curves. We discuss how to discriminate three models, relevant models parameters, their evolutionary origins, and implications for the early evolution of the Universe.
The First 3D Simulations of Carbon Burning in a Massive Star
Authors: Cristini A. , Meakin C. , Hirschi R. , Arnett D. , Georgy C. , Viallet M. 
Published: July 2017

AbstractWe present the first detailed three-dimensional hydrodynamic implicit large eddy simulations of turbulent convection for carbon burning. The simulations start with an initial radial profile mapped from a carbon burning shell within a 15 M⊙stellar evolution model. We considered 4 resolutions from 1283to 10243zones. These simulations confirm that convective boundary mixing (CBM) occurs via turbulent entrainment as in the case of oxygen burning. The expansion of the boundary into the surrounding stable region and the entrainment rate are smaller at the bottom boundary because it is stiffer than the upper boundary. The results of this and similar studies call for improved CBM prescriptions in 1D stellar evolution models.
Students’ Growth Mindsets, Goals, and Academic Outcomes in	Mathematics
Authors: Bostwick Keiko C. P. , Collie Rebecca J. , Martin Andrew J. , Durksen Tracy L. 
Published: July 2017

Abstract. The majority of educational research on the associations between growth constructs and academic outcomes has adopted a somewhat piecemeal approach, focusing on either growth mindset (implicit beliefs about intelligence) or growth goals. We explore an integrative approach to analyzing the impact of well-established and emerging growth constructs (viz. growth mindset, self-based growth goals, task-based growth goals) on academic outcomes in mathematics. Our participants were secondary school students (n = 4,411) in grades 7–9 from 19 schools in Australia. We used confirmatory factor analysis (CFA) and structural equation modeling (SEM) to test the measurement and substantive hypotheses in our study. We found that growth mindset, self-based growth goals, and task-based growth goals were well represented by an underlying growth orientation factor. Additionally, after controlling for five student background factors (e.g., sex, socioeconomic status [SES]), students’ growth orientation positively predicted mathematics engagement and achievement. These results contribute to the growing literature on educational growth constructs and academic success.
Onion-like multilayered polymer capsules synthesized by a bioinspired inside-out technique
Authors: Zarket Brady C. , Raghavan Srinivasa R. 
Published: July 2017

AbstractDiverse structures in nature, such as the spinal disc and the onion have many concentric layers, and are created starting from the core and proceeding outwards. Here, we demonstrate an inside-out technique for creating multilayered polymer capsules. First, an initiator-loaded gel core is placed in a solution of monomer 1. The initiator diffuses outward and induces polymerization, leading to a shell of polymer 1. Thereafter, the core-shell structure is loaded with fresh initiator and placed in monomer 2, which causes a concentric shell of polymer 2 to form around the first shell. This process can be repeated to form multiple layers, each of a distinct polymer, and of controlled layer thickness. We show that these multilayered capsules can exhibit remarkable mechanical resilience as well as stimuli-responsive properties. The release of solutes from these capsules can be tailored to follow specific profiles depending on the chemistry and order of adjacent layers.
Modulation of the tick gut milieu by a secreted tick protein favors Borrelia burgdorferi colonization
Authors: Narasimhan Sukanya , Schuijt Tim J. , Abraham Nabil M. , Rajeevan Nallakkandi , Coumou Jeroen , Graham Morven , Robson Andrew , Wu Ming-Jie , Daffre Sirlei , Hovius Joppe W. , Fikrig Erol 
Published: July 2017

AbstractThe Lyme disease agent, Borrelia burgdorferi, colonizes the gut of the tick Ixodes scapularis, which transmits the pathogen to vertebrate hosts including humans. Here we show that B. burgdorferi colonization increases the expression of several tick gut genes including pixr, encoding a secreted gut protein with a Reeler domain. RNA interference-mediated silencing of pixr, or immunity against PIXR in mice, impairs the ability of B. burgdorferi to colonize the tick gut. PIXR inhibits bacterial biofilm formation in vitro and in vivo. Abrogation of PIXR function in vivo results in alterations in the gut microbiome, metabolome and immune responses. These alterations influence the spirochete entering the tick gut in multiple ways. PIXR abrogation also impairs larval molting, indicative of its role in tick biology. This study highlights the role of the tick gut in actively managing its microbiome, and how this impacts B. burgdorferi colonization of its arthropod vector.
Ex vivo pretreatment of human vessels with siRNA nanoparticles provides protein silencing in endothelial cells
Authors: Cui Jiajia , Qin Lingfeng , Zhang Junwei , Abrahimi Parwiz , Li Hong , Li Guangxin , Tietjen Gregory T. , Tellides George , Pober Jordan S. , Mark Saltzman W. 
Published: July 2017

AbstractHuman endothelial cells are initiators and targets of the rejection response. Pre-operative modification of endothelial cells by small interfering RNA transfection could shape the nature of the host response post-transplantation. Ablation of endothelial cell class II major histocompatibility complex molecules by small interfering RNA targeting of class II transactivator can reduce the capacity of human endothelial cells to recruit and activate alloreactive T cells. Here, we report the development of small interfering RNA-releasing poly(amine-co-ester) nanoparticles, distinguished by their high content of a hydrophobic lactone. We show that a single transfection of small interfering RNA targeting class II transactivator attenuates major histocompatibility complex class II expression on endothelial cells for at least 4 to 6 weeks after transplantation into immunodeficient mouse hosts. Furthermore, silencing of major histocompatibility complex class II reduces allogeneic T-cell responses in vitro and in vivo. These data suggest that poly(amine-co-ester) nanoparticles, potentially administered during ex vivo normothermic machine perfusion of human organs, could be used to modify endothelial cells with a sustained effect after transplantation.
The contribution of hydrogen evolution processes during corrosion of aluminium and aluminium alloys investigated by potentiodynamic polarisation coupled with real-time hydrogen measurement
Authors: Laurent Christophe , Scenini Fabio , Monetta Tullio , Bellucci Francesco , Curioni Michele 
Published: July 2017

AbstractWater reduction, which leads to the evolution of hydrogen, is a key cathodic process for corrosion of many metals of technological interest such as magnesium, aluminium, and zinc; and its understanding is critical for design of new alloys or protective treatments. In this work, real-time hydrogen evolution measurement was coupled with potentiodynamic measurements on high-purity aluminium and AA2024-T3 aluminium alloy. The results show that both materials exhibit superfluous hydrogen evolution during anodic polarisation and that the presence of cathodically active alloying elements enhances hydrogen evolution. Furthermore, it was observed for the first time that superfluous hydrogen evolution also occurs during cathodic polarisation. Both the anodic and cathodic behaviours can be rationalised by a model assuming that superfluous hydrogen evolution occurs locally where the naturally formed oxide is disrupted. Specifically, during anodic polarisation, oxide disruption is due to the combined presence of chloride ions and acidification, whereas during cathodic polarisation, such disruption is due to alkalinisation. Furthermore, the presence of cathodically active alloying elements enhances superfluous hydrogen evolution in response to either anodic or cathodic polarisation, and results in ‘cathodic activation’ of the dissolved regions.
Inhibition of glutamate decarboxylase (GAD) by ethyl ketopentenoate (EKP) induces treatment-resistant epileptic seizures in zebrafish
Authors: Zhang Yifan , Vanmeert Michiel , Siekierska Aleksandra , Ny Annelii , John Jubi , Callewaert Geert , Lescrinier Eveline , Dehaen Wim , de Witte Peter A. M. , Kaminski Rafal M. 
Published: July 2017

AbstractEpilepsy is a chronic brain disorder characterized by recurrent seizures due to abnormal, excessive and synchronous neuronal activities in the brain. It affects approximately 65 million people worldwide, one third of which are still estimated to suffer from refractory seizures. Glutamic acid decarboxylase (GAD) that converts glutamate into GABA is a key enzyme in the dynamic regulation of neural network excitability. Importantly, clinical evidence shows that lowered GAD activity is associated with several forms of epilepsy which are often treatment resistant. In the present study, we synthetized and explored the possibility of using ethyl ketopentenoate (EKP), a lipid-permeable GAD-inhibitor, to induce refractory seizures in zebrafish larvae. Our results demonstrate that EKP evoked robust convulsive locomotor activities, excessive epileptiform discharges and upregulatedc-fosexpression in zebrafish. Moreover, transgenic animals in which neuronal cells express apoaequorin, a Ca2+-sensitive bioluminescent photoprotein, displayed large luminescence signals indicating strong EKP-induced neuronal activation. Molecular docking data indicated that this proconvulsant activity resulted from the direct inhibition of both gad67 and gad65. Limited protective efficacy of tested anti-seizure drugs (ASDs) demonstrated a high level of treatment resistance of EKP-induced seizures. We conclude that the EKP zebrafish model can serve as a high-throughput platform for novel ASDs discovery.
Single-shot Monitoring of Ultrafast Processes via X-ray Streaking at a Free Electron Laser
Authors: Buzzi Michele , Makita Mikako , Howald Ludovic , Kleibert Armin , Vodungbo Boris , Maldonado Pablo , Raabe Jörg , Jaouen Nicolas , Redlin Harald , Tiedtke Kai , Oppeneer Peter M. , David Christian , Nolting Frithjof , Lüning Jan 
Published: July 2017

AbstractThe advent of x-ray free electron lasers has extended the unique capabilities of resonant x-ray spectroscopy techniques to ultrafast time scales. Here, we report on a novel experimental method that allows retrieving with a single x-ray pulse the time evolution of an ultrafast process, not only at a few discrete time delays, but continuously over an extended time window. We used a single x-ray pulse to resolve the laser-induced ultrafast demagnetisation dynamics in a thin cobalt film over a time window of about 1.6 ps with an excellent signal to noise ratio. From one representative single shot measurement we extract a spin relaxation time of (130 ± 30) fs with an average value, based on 193 single shot events of (113 ± 20) fs. These results are limited by the achieved experimental time resolution of 120 fs, and both values are in excellent agreement with previous results and theoretical modelling. More generally, this new experimental approach to ultrafast x-ray spectroscopy paves the way to the study of non-repetitive processes that cannot be investigated using traditional repetitive pump-probe schemes.