bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Tertiary Gamma Prime (γ′) Size Evolution on Dwell Fatigue Crack Growth Behavior in CG RR1000
Authors: Schulz F. , Li H. Y. , Kitaguchi H. , Child D. , Williams S. , Bowen P. 
Published: July 2018

Abstract
This work investigates coarsening behavior of strengthening precipitates (γ′) in coarse-grained RR1000 after isothermal exposure for various times (50 to 500 hours) at 700 °C and 750 °C. The impact of these isothermal treatments is then studied by carrying out dwell (1 hour) fatigue crack growth tests at 700 °C in air. Such dwell periods can increase crack growth rates by nearly two orders of magnitude compared with baseline (0.25 Hz trapezoidal waveform) fatigue crack growth tests. Predominantly, scanning electron microscopy was used for γ′ analysis. Transmission electron microscopy was also utilized when necessary. Overaging as a thermodynamically driven and diffusion-controlled process strongly affects tertiary γ′ precipitates for the temperatures and treatment times investigated here. No influence of overaging on baseline fatigue behavior is observed. However, after overaging at 750 °C for 500 hours (which increases the mean tertiary γ′ size by a factor of two from 17 to 37 nm), dwell crack growth rates at 700 °C are reduced by one order of magnitude. Increased dwell fatigue crack growth resistance is also measured after overaging for 100 hours at 700 °C. The potential influence of γ′ distributions on dwell fatigue crack growth resistance is discussed in terms of stress relaxation behavior during dwell periods.
Geochemical features and genesis of continental cobalt-rich ferromanganese crusts
Authors: Maksimov S.O. , Safronov P.P. 
Published: July 2018

Abstract
Mass cobalt-rich ferromanganese microcrusts and nodules similar in morphology and chemical composition to cobalt-rich ferromanganese deep-ocean crusts were found in Cenozoic volcanic rocks in southern Primorye. Research has shown that ore genesis of this type is genetically related to argillization and destruction of siliceous rocks by CO2-rich fluids, which is confirmed by experimental data on carbon erosion of iron-containing materials. Two types of this fluid ore genesis are recognized: (1) relatively high-temperature (vapor–condensate), related to late volcanic processes and fracture gas infiltration, and (2) low-temperature (vapor–liquid–condensate), controlled by degassing followed by carbon mobilization (gasification). Primarily colloidal ferromanganese segregations have high contents of Co, Ni, Pb, Cu, and Ce, typical of oceanic ore genesis. Regardless of the concentrations of these metals in the protoliths, their contents in microcrusts are similar (n–10n wt.%). This indicates the same ore genesis mechanism and similar sorption properties of the colloidal ferromanganese material formed. Barium- and cerium-rich ferromanganese microcrusts and nodules are abundant. Condensed drops of iron-containing platinum were found in apobasaltic nickel-rich ferromanganese segregations. There is a cerium paradox expressed as a minimum or a total lack of cerium among rare-earth phosphates associated with ferromanganese microcrusts. Fluid destruction and oxide metallization of ocean-floor basalts are assumed to be the main source of metals for oceanic ferromanganese crusts and nodules.
The global biogeography of avian haemosporidian parasites is characterized by local diversification and intercontinental dispersal
Authors: Ellis Vincenzo A. , Sari Eloisa H. R. , Rubenstein Dustin R. , Dickerson Rebecca C. , Bensch Staffan , Ricklefs Robert E. 
Published: July 2018

AbstractThe biogeographic histories of parasites and pathogens are infrequently compared with those of free-living species, including their hosts. Documenting the frequency with which parasites and pathogens disperse across geographic regions contributes to understanding not only their evolution, but also the likelihood that they may become emerging infectious diseases. Haemosporidian parasites of birds (parasite generaPlasmodium,HaemoproteusandLeucocytozoon) are globally distributed, dipteran-vectored parasites. To date, over 2000 avian haemosporidian lineages have been designated by molecular barcoding methods. To achieve their current distributions, some lineages must have dispersed long distances, often over water. Here we quantify such events using the global avian haemosporidian database MalAvi and additional records primarily from the Americas. We scored lineages as belonging to one or more global biogeographic regions based on infection records. Most lineages were restricted to a single region but some were globally distributed. We also used part of the cytochromebgene to create genus-level parasite phylogenies and scored well-supported nodes as having descendant lineages in regional sympatry or allopatry. Descendant sister lineages ofPlasmodium,HaemoproteusandLeucocytozoonwere distributed in allopatry in 11, 16 and 15% of investigated nodes, respectively. Although a small but significant fraction of the molecular variance in cytochromebof all three genera could be explained by biogeographic region, global parasite dispersal likely contributed to the majority of the unexplained variance. Our results suggest that avian haemosporidian parasites have faced few geographic barriers to dispersal over their evolutionary history.
Accepting, active and in control: older women's experiences of ageing with peripheral arterial disease
Authors: Bassett Kimberley , Gullifer Judith , Varcoe Ramon L. 
Published: July 2018

AbstractThe population of Australia is ageing, with women being the primary beneficiaries of this increase in longevity. Increasingly older individuals are being diagnosed with different chronic illnesses such as peripheral arterial disease (PAD) which causes blockages of the blood vessels in the legs resulting in pain, non-healing ulcers, immobility and the potential amputation of the threatened limb. PAD has been traditionally thought to affect men more than women. Resultingly, women have been under-represented in clinical trials of PAD and under-diagnosed in the health-care setting. However, it has recently been acknowledged that women are indeedmorelikely to suffer from PAD than men due to increased presence of disease and survival advantage. As such, very little is known about women's understanding of and the meaning they create of their experiences of PAD. Therefore, how older women with PAD experience the ageing process is the focus of this qualitative research project. Interviews were conducted with 11 women from Sydney, Australia aged over 65 years who had been diagnosed with PAD. The interviews were analysed using an inductive thematic analysis. Three manifest themes were constructed: independence and control, active and involved, and the acceptance of ageing. These findings emphasised the idea that despite the presence of a chronic illness and increased age, remaining independent and engaged with life was vital to these women's wellbeing. Their subjective experiences of ageing reflect the fact that by adapting to the physical, mental and social changes that come with growing older, the focus does not need to be on loss and decline but rather can be about the continuation of life that can be both positive and meaningful.
Australian attitudes to intergenerational equity: impacts of social and policy change
Authors: Kendig Hal , Hussain Rafat , O'Loughlin Kate , Cannon Lisa 
Published: July 2018

AbstractAttitudes to ageing can predispose decision-making as governments, interest groups and electorates negotiate competing demands in the context of economic constraints and social change. This paper, based on national survey data, investigates change and stability in Australian attitudes to intergenerational equity from 2009–2010 to 2015–2017, alongside concurrent socio-economic and policy change as well as cohort succession. The emphasis is on the baby-boom cohort who are viewed as significant beneficiaries of social change relative to opportunities of younger and older cohorts. Views of older people as a needy group may be changing slightly as more enter later life with substantial wealth and resources. Our results show that there is little perception of intergenerational conflict with the exception of the Millennial cohort whose life chances are compromised by economic and expenditure constraint over the past decade. Overall, attitudes remain sympathetic to older people, especially among women and people rendered vulnerable by poor health, non-home-ownership and low socio-economic positions. The findings do not align with government portrayals of intergenerational inequalities notwithstanding many having negative views of the future and ongoing expenditure restraint strategies. At what appears to be a critical turning point in the life chances of successive cohorts, the findings indicate the interplay between attitudes and social and policy change, as well as implications for social equity and processes of attitudinal change.
The Maser-Starburst connection in NGC 253
Authors: Ellingsen Simon P. 
Published: July 2018

AbstractNGC 253 is one of the closest starburst galaxies to the Milky Way and as such it has been studied in detail across the electromagnetic spectrum. Recent observations have detected the first extragalactic class I methanol masers at 36 and 44 GHz and the first extragalactic HC3N (cyanoacetylene) masers in this source. Here we discuss the location of the masers with respect to key morphological features within NGC 253 and the association between the masers and the ongoing starburst.
A detailed study toward the Water fountain IRAS 15445-5449
Authors: Pérez-Sánchez Andrés F. , López Rebeca García , Vlemmings Wouter , Tafoya Daniel 
Published: July 2018

AbstractPost-Asymptotic giant branch (post-ABG) sources with high-velocity spectral features of H2O maser emission detected toward their circumstellar envelopes (CSEs) are known as Water Fountain (WF) nebulae. These are low- or intermediate-mass Galactic stellar sources that are undergoing the late stages of an intense mass-loss process. The velocity and the spatial distribution of the H2O maser spectral features can provide information about the kinematics of the molecular gas component of their CSEs. Hence, observational studies toward WF nebulae could help to better understand the formation of the asymmetric structures (hundred to thousand AUs) commonly seen toward Planetary nebulae (PNe). Here we present preliminary results of observations done toward the WF IRAS 15445-5449 using the Australia Telescope Compact Array (ATCA) and the Very Large Telescope (SINFONI/VLT). Assuming that the pumping of the H2O maser transitions is a consequence of shocks between different velocity winds, the spatial distribution of the emission shed light on the scales of the regions affected by the propagation of the shock-fronts.
SWAG Water Masers in the Galactic Center
Authors: Ott Jürgen , Krieger Nico , Rickert Matthew , Meier David , Ginsburg Adam , Yusef-Zadeh Farhad ,   the SWAG team
Published: July 2018

AbstractThe Galactic Center contains large amounts of molecular and ionized gas as well as a plethora of energetic objects. Water masers are an extinction-insensitive probe for star formation and thus ideal for studies of star formation stages in this highly obscured region. With the Australia Telescope Compact Array, we observed 22 GHz water masers in the entire Central Molecular Zone with sub-parsec resolution as part of the large SWAG survey: “Survey of Water and Ammonia in the Galactic Center”. We detect of order 600 22 GHz masers with isotropic luminosities down to ~10−7 L⊙. Masers with luminosities of ≳10−6 L⊙ are likely associated with young stellar objects. They appear to be close to molecular gas streamers and may be due to star formation events that are triggered at pericenter passages near Sgr A*. Weaker masers are more widely distributed and frequently show double line features, a tell-tale sign for an origin in evolved star envelopes.
Periodic methanol masers and colliding wind binaries
Authors: van den Heever Stefanus P. , van der Walt D. J. , Pittard J. M. , Hoare M. G. 
Published: July 2018

AbstractSince the discovery of periodic variability of Class II methanol masers associated with high-mass star formation, several possible driving mechanisms have been proposed to explain this phenomenon. Here the colliding wind binary (CWB) hypothesis is proposed to describe the periodic variability. It is shown that the recombination of a partially ionized gas describes the flare profiles remarkably well. In addition, the quiescent state flux density is also described remarkably well by the time-dependent change of the electron density. This suggests that the periodicity is caused by the time-dependent change in the radio free-free emission from the background HII regions against which the maser is projected.
Bow shocks in water fountain jets
Authors: Orosz Gabor , Gómez José F. , Tafoya Daniel , Imai Hiroshi , Torrelles José M. , Ngendo Ann Njeri , Burns Ross A. 
Published: July 2018

AbstractWe briefly introduce the VLBI maser astrometric analysis of IRAS 18043–2116 and IRAS 18113–2503, two remarkable and unusual water fountains with spectacular bipolar bow shocks in their high-speed collimated jet-driven outflows. The 22 GHz H2O maser structures and velocities clearly show that the jets are formed in very short-lived, episodic outbursts, which may indicate episodic accretion in an underlying binary system.
A systematic observational study of radio properties of H2O megamaser Seyfert 2s: A Guide for H2O megamaser surveys
Authors: Zhang J. S. , Liu Z. W. , Henkel C. 
Published: July 2018

AbstractAnalyzing archival data from different telescopes, H2O megamaser Seyfert 2s appeared to exhibit higher nuclear radio luminosities than non-masing Seyfert 2s (Zhang et al. 2012). This has been confirmed by our follow-up study on multi-band (11, 6, 3.6, 2, 1.3 cm) radio properties of maser host Seyfert 2s, through systematic Effelsberg observations (Liu et al. 2017). The nuclear radio luminosity was supposed to be a suitable indicator to guide future AGN maser searches. Thus we performed a pilot survey with the Effelsberg telescope on H2O maser emission toward a small sample of radio-bright Seyfert 2 galaxies with relatively higher redshift (>0.04). Our pilot survey led to one new megamaser source and one additional possible detection, which reflects our success in selecting H2O megamaser candidates compared to previous observations (higher detection rate, larger distance). Our successful selection technique choosing Seyfert 2s with radio-bright nuclei may provide good guiding for future H2O megamaser surveys. Therefore we are conducting a large systematic survey toward a big Seyfert 2 sample with such radio-bright nuclei. Detections of luminous H2O masers at large distance (z>0.04) may hold the great potential to increase our knowledge on the central highly obscured but still very enigmatic regions of active Seyfert galaxies (Zhang et al. 2017).
Filamentary Flows and Clump-fed High-mass Star Formation in G22
Authors: Yuan J. , Li J.-Z. , Wu Y. 
Published: July 2018

AbstractG22 is a hub-filament system composed of four supercritical filaments. Velocity gradients are detected along three filaments. A total mass infall rate of 700 M⊙ Myr−1 would double the hub mass in about three free-fall times. The most massive clump C1 would be in global collapse with an infall velocity of 0.26 km s−1 and a mass infall rate of 5 × 10−4M⊙ yr−1, which is supported by the prevalent HCO+ (3-2) and 13CO (3-2) blue profiles. A hot molecular core (SMA1) was revealed in C1. At the SMA1 center, there is a massive protostar (MIR1) driving multipolar outflows which are associated with clusters of class I methanol masers. MIR1 may be still growing with an accretion rate of 7 × 10−5M⊙ yr−1. Filamentary flows, clump-scale collapse, core-scale accretion coexist in G22, suggesting that high-mass starless cores may not be prerequisite to form high-mass stars. In the high-mass star formation process, the central protostar, the core, and the clump can grow in mass simultaneously.
Methanol masers and magnetic field in IRAS18089-1732
Authors: Dall’Olio Daria , Vlemmings W. H. T. , Surcis G. , Beuther H. , Lankhaar B. , Persson M. V. , Richards A. M. S. , Varenius E. 
Published: July 2018

AbstractTheoretical simulations have shown that magnetic fields play an important role in massive star formation: they can suppress fragmentation in the star forming cloud, enhance accretion via disc and regulate outflows and jets. However, models require specific magnetic configurations and need more observational constraints to properly test the impact of magnetic fields. We investigate the magnetic field structure of the massive protostar IRAS18089-1732, analysing 6.7 GHz CH3OH maser MERLIN observations. IRAS18089-1732 is a well studied high mass protostar, showing a hot core chemistry, an accretion disc and a bipolar outflow. An ordered magnetic field oriented around its disc has been detected from previous observations of polarised dust. This gives us the chance to investigate how the magnetic field at the small scale probed by masers relates to the large scale field probed by the dust.
A Masing Event in the Cat’s Paw
Authors: MacLeod G. , Smits D. , Goedhart S. , Ellingsen S. , Hunter T. , Brogan C. 
Published: July 2018

AbstractWe present Kitty, an unprecedented and near simultaneous flaring event in ten transitions (6 hydroxyl, 1 water and 3 methanol), that began on 1 January 2015 in the massive star-forming region NGC6334F located in the Cat’s Paw Nebula. The brightest components in each transition increased by factors of 20 to 70 in line with a factor of ~70 increase in dust emission luminosity for the source MM1. We also report the detection of only the fifth known 4.660 GHz hydroxyl maser and that it varied in a correlated fashion with 1.720, 6.031, and 6.035 GHz hydroxyl counterparts. We postulate that if Kitty, and two historical flares in 1965 & 1999, are accretion events and are caused by the successive passages of a secondary star disrupting the accretion disk, where the frequency of occurrence is cycling down at a rate of ~2.2, it is possible another event will occur in 2022.
Linear polarisation of Class I methanol masers in massive star formation regions
Authors: Kang Ji-hyun , Byun Do-Young , Kim Kee-Tae , Lyo Aran , Kim Jongsoo , Kim Mi-kyoung , Vlemmings Wouter , Lankhaar Boy , Surcis Gabriele 
Published: July 2018

AbstractWe present the results of the linear polarisation observations of methanol masers at 44 and 95 GHz towards 39 massive star forming regions (Kanget al.2016). These two lines are observed simultaneously with the 21-m Korean VLBI Network (KVN) telescope in single dish mode. About 60% of the observed showed fractional polarisation of a few percents at least at one of the two transition lines. We note that the linear polarisation of the 44 GHz methanol maser is first detected in this study including single dish and interferometer observations. We find the polarisation properties of these two lines are similar as expected, since they trace similar regions. As a follow-up study, we have carried out the VLBI polarisation observations toward some 44 GHz maser targets using the KVN telescope. We present preliminary VLBI polarisation results of G10.34-0.14, which show consistent polarisation properties in multiple epoch observations.
The extraordinary outburst in NGC6334I-MM1: the rise of dust and emergence of 6.7 GHz methanol masers
Authors: Hunter Todd R. , Brogan Crystal L. , Chibueze James O. , Cyganowski Claudia J. , Hirota Tomoya , MacLeod Gordon C. 
Published: July 2018

AbstractOur 2015-2016 ALMA 1.3 to 0.87 mm observations (resolution ~200 au) of the massive protocluster NGC6334I revealed that an extraordinary outburst had occurred in the dominant millimeter dust core MM1 (luminosity increase of 70×) when compared with earlier SMA data. The outburst was accompanied by the flaring of ten maser transitions of three species. We present new results from our recent JVLA observations of Class II 6.7 GHz methanol masers and 6 GHz excited OH masers in this region. Class II masers had not previously been detected toward MM1 in any interferometric observations recorded over the past 30 years that targeted the bright masers toward other members of the protocluster (MM2 and MM3=NGC6334F). Methanol masers now appear both toward and adjacent to MM1 with the strongest spots located in a dust cavity ~1 arcsec (1300 au) north of the MM1B hypercompact HII region. In addition, new excited OH masers appear on the non-thermal source CM2. These data reveal the dramatic effects of episodic accretion onto a deeply-embedded high mass protostar and demonstrate its ongoing impact on the surrounding protocluster.
Spatially resolving the OH masers in M82
Authors: Argo Megan 
Published: July 2018

AbstractWith luminosities between those of typical Galactic OH masers and more distant OH megamasers, the masers in the nearby galaxy M82 are an interesting population which can be used to probe the physical conditions in the central starburst region of this irregular galaxy. Following on from previous low spatial resolution studies, here we present the initial results of two high-resolution observations separated by eight years. We find that some of the maser spots are resolved into multiple spatial components when observed with the EVN, as predicted by our previous studies, but that significantly less flux is recovered that that seen with the previous VLA observations. We conclude that some of this flux difference is likely due to variability but that, in common with the results seen in Arp220, there may also be a significant diffuse component.
Physical properties of Class I methanol masers
Authors: Leurini Silvia , Menten Karl M. 
Published: July 2018

AbstractAs first realised in the late 1980s, methanol masers come in two varieties, termed Class I and Class II. While Class II masers had observationally been extensively studied in the past, until recently relatively little attention was paid to Class I methanol masers due to their low luminosities compared to other maser transitions. In this review, we will focus on the recent progress in our understanding of Class I methanol masers both from an observational and from a theoretical point of view.
Long-term photometric observations in the field of the star formation region NGC7129
Authors: Semkov Evgeni , Peneva Stoyanka , Ibryamov Sunay , Mutafov Asen 
Published: July 2018

AbstractWe present results from long-term optical photometric observations of the Pre-Main Sequence (PMS) stars, located in the star formation region around the bright nebula NGC 7129. Using the long-term light curves and spectroscopic data, we tried to classify the PMS objects in the field and to define the reasons for the observed brightness variations. Our main goal is to explore the known PMS stars and discover new, young, variable stars. The new variable PMS star 2MASS J21403576+6635000 exhibits unusual brightness variations for very short time intervals (few minutes or hours) with comparatively large amplitudes (ΔI = 2.65 mag).
VLA Observations of a Sample of Low-Brightness 6.7 GHz Methanol Masers
Authors: Olmi Luca , Araya Esteban D. , Armstrong Jason 
Published: July 2018

AbstractIn 2014 we conducted a survey for 6.7 GHz methanol masers with the Arecibo Telescope toward far infrared sources selected from the Hi-GAL catalog of massive cores. We found a number of sources with weak 6.7 GHz methanol masers, possibly indicating regions in early stages of star formation. Here we describe the results of follow-up observations that were conducted with the Very Large Array in New Mexico to characterize this new population of “weak” 6.7 GHz methanol masers.