bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pavement performance evaluation for different combinations of temperature conditions and bituminous mixes
Authors: Ranadive M. S. , Tapase Anand 
Published: September 2016

Abstract
The effectiveness of 2D axisymmetric finite element analysis in predicting the performance of flexible pavements at different temperatures is illustrated in the present study. The critical parameters are examined for variation in thicknesses and material properties of the bituminous layer, to select the right binder grade of bituminous mixes for the particular climatic condition or the selected temperature profile. To observe the effect of decrement in temperature profile of the under layer on the performance of the pavement, variation in modulus of dense bituminous macadam is analyzed for material properties reported as per IRC: 37-2012. For the modern trucks, which usually have more than 0.800 MPa tyre pressure, the right binder grade of bituminous layer comprising a wearing course and dense bituminous macadam is 1700 MPa for 250 mm-thick bituminous layer. When more stiffer binder is used, drastic change in the value of critical parameters is observed. A reduction of 18.98 and 5.25 % in horizontal tensile strain and vertical compressive strain, respectively, is observed at a 200 mm thickness of bituminous layer and around 21.12 and 6.72 % in horizontal tensile strain and vertical compressive strain, respectively, at 250 mm thickness of bituminous layer. As the values of the critical parameters are noticed well within the allowable limits at 200 mm, it is concluded that the use of a stiffer binder for DBM makes the pavement safe as far as fatigue of bituminous layer and rutting in subgrade is concerned with the reduction in thickness of the bituminous layer even at higher temperature. It is observed that the use of waste plastic/rubber is found in safe limits at 250 mm-thick bituminous layer for the selected condition. It is concluded that the use of too soft a bituminous mix results in lowering the structural capacity of the pavement at high temperatures and too hard bituminous mixes would become brittle at low temperatures.
Percutaneous cholecystostomy for acute cholecystitis in high‐risk elderly patients
Authors: Lin Wei‐Chen , Chang Chen‐Wang , Chu Cheng‐Hsin 
Published: September 2016

AbstractEmergency cholecystectomy for acute cholecystitis (AC) is associated with high morbidity and mortality rates in elderly patients with significant comorbidities. The aim of this study was to evaluate percutaneous cholecystostomy for AC in elderly patients with various coexisting diseases. We retrospectively reviewed the records of 4311 patients with AC treated in Mackay Memorial Hospital between the years 2000 and 2015. The clinical course of AC was compared between nonelderly (age ≤70 years) and elderly patients (age >70 years). In total, 67 elderly patients and 32 nonelderly patients received percutaneous cholecystostomy. The rate of percutaneous cholecystostomy increased between the years 2011 and 2015 (from 2.5% to 12.2%) and this procedure was more common in the elderly group (p = 0.009). In addition, the comorbidities of ischemic heart disease and chronic kidney disease were higher in elderly than in nonelderly patients (p = 0.014 and p = 0.015, respectively). The American Society of Anesthesiologists' classification was higher in the elderly patients (p = 0.001). The overall survival‐free rate of recurrent cholecystitis in patients who did not receive cholecystectomy was not significantly different in the two groups. When compared with emergent cholecystectomy in high‐risk elderly patients, percutaneous cholecystostomy resulted in reduced hospital stay and morbidity (p = 0.002 and p = 0.013, respectively). Our results demonstrate that percutaneous cholecystostomy has become a common and early treatment for AC in high‐risk elderly patients with ischemic heart disease or chronic kidney disease. Identifying such patients will possibly improve clinical outcomes, reduce hospital stay and morbidity, and facilitate delayed laparoscopic cholecystectomy.
Giant Molecular Cloud Populations in Nearby Galaxies
Authors: Hughes Annie , Meidt Sharon , Colombo Dario , Schruba Andreas , Schinnerer Eva , Leroy Adam , Wong Tony ,   the PAWS, MAGMA, CANON and M31-CARMA survey teams
Published: September 2016

AbstractWe present new results from a comparative analysis of the resolved giant molecular cloud (GMC) populations in six nearby galaxies. We show that the GMCs in denser environments–M51, the centre of NGC6946–have greater CO surface brightness and higher velocity dispersions relative to their size than GMCs in less dense environments. We find systematic differences in the GMC mass distribution among galaxies, such that more of the molecular gas in the low-mass galaxies (M33, the Large Magellanic Cloud) and the outer disk of M31 is located in low mass clouds. Using the number density of GMCs in the interarm regions of M51, we argue that GMC destruction in this region is regulated by shear, and that cloud lifetimes there are finite and short, ~20 to 30 Myr. Our results indicate the importance of galactic environment on the evolution of GMCs, and on a galaxy's global pattern of star formation.
Probing star formation relations of mergers and normal galaxies across the CO ladder
Authors: Greve Thomas R. 
Published: September 2016

AbstractWe examine integrated luminosity relations between the IR continuum and the CO rotational ladder observed for local (ultra) luminous infra-red galaxies ((U)LIRGs, LIR ≥ 1011 M⊙) and normal star forming galaxies in the context of radiation pressure regulated star formation proposed by Andrews & Thompson (2011). This can account for the normalization and linear slopes of the luminosity relations (log LIR = α log L'CO + β) of both low- and high-J CO lines observed for normal galaxies. Super-linear slopes occur for galaxy samples with significantly different dense gas fractions. Local (U)LIRGs are observed to have sub-linear high-J (Jup > 6) slopes or, equivalently, increasing LCOhigh-J/LIR with LIR. In the extreme ISM conditions of local (U)LIRGs, the high-J CO lines no longer trace individual hot spots of star formation (which gave rise to the linear slopes for normal galaxies) but a more widespread warm and dense gas phase mechanically heated by powerful supernovae-driven turbulence and shocks.
The Formation and Destruction of Molecular Clouds and Galactic Star Formation
Authors: Inutsuka Shu-ichiro , Inoue Tsuyoshi , Iwasaki Kazunari , Hosokawa Takashi , Kobayashi Masato I. N. 
Published: September 2016

AbstractWe discuss an overall picture of star formation in the Galaxy. Recent high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a new scenario of molecular cloud formation through interacting shells or bubbles on galactic scales. We estimate the ensemble-averaged growth rate of individual molecular clouds, and predict the associated cloud mass function. This picture naturally explains the accelerated star formation over many million years that was previously reported by stellar age determination in nearby star forming regions. The recent claim of cloud-cloud collisions as a mechanism for forming massive stars and star clusters can be naturally accommodated in this scenario. This explains why massive stars formed in cloud-cloud collisions follows the power-law slope of the mass function of molecular cloud cores repeatedly found in low-mass star forming regions.
Observational studies of the formation and evolution of dense cores
Authors: Tafalla Mario 
Published: September 2016

AbstractDense cores are the simplest star-forming sites. They represent the end stage of the fragmentation hierarchy that characterizes molecular clouds, and they likely control the efficiency of star formation via their relatively low numbers. Recent dust continuum observations of entire molecular clouds show that dense cores often lie along large-scale filamentary structures, suggesting that the cores form by some type of fragmentation process in an approximately cylindrical geometry. To understand the formation mechanism of cores, additional kinematic information is needed, and this requires observations in molecular-line tracers of both the dense cores and their surrounding cloud material. Here I present some recent efforts to clarify the kinematic structure of core-forming regions in the nearby Taurus molecular cloud. These new observations show that the filamentary structures seen in clouds are often more complex than suggested by the maps of continuum emission, and that they consist of multiple fiber-like components that have different velocities and sonic internal motions. These components likely arise from turbulent fragmentation of the large-scale flows that generate the filamentary structures. While not all these fiber-like components further fragment to form dense cores, a small group of them does so, likely by gravitational instability. This fragmentation produces characteristic chain-like groups of dense cores that further evolve to form stars.
Small-scale properties of Class 0 protostars from the CALYPSO IRAM-PdBI survey
Authors: Maury Anaëlle , André Philippe , Maret Sébastien , Belloche Arnaud , Codella Claudio , Cabrit Sylvie , Gueth Frédéric ,   CALYPSO collaboration
Published: September 2016

AbstractBecause the formation of protostars is believed to be closely tied to the angular momentum problem of star formation, characterizing the properties of the youngest disks around Class 0 objects is crucial. However, not much is known on the structure of the youngest protostellar envelopes, on the small scales at which disks and multiple systems are observed around more evolved YSOs, due to a lack of comprehensive high angular resolution observations (probing <100 AU). In order to tackle this issue, we conducted a large observing program with the IRAM Plateau de Bure interferometer (PdBI): the CALYPSO survey, providing us with detailed maps of molecular lines and millimeter continuum emission, probing scales down to ~30–50 au towards a sample of 17 Class 0 protostars. Here we present our analysis of the CALYPSO dust continuum emission maps, constraining disk properties of the Class 0 protostars in our sample. We show that large, r > 50 au, disk structures are not observed in most Class 0 protostars from our sample, which can be described by various envelope models reproducing satisfactorily the intensity distribution of the dust emission at all scales from 50 au to 5000 au.
SMA and ALMA studies of protoplanetary disk formation around low-mass protostars
Authors: Takakuwa Shigehisa , Ohashi Nagayoshi , Yen Hsi-Wei , Chou Ti-Lin , Saigo Kazuya , Saito Masao , Aso Yusuke , Aikawa Yuri , Koyamatsu Shin , Machida Masahiro N. , Takahashi Sanemichi Z. , Tomida Kengo , Tomisaka Kohji 
Published: September 2016

AbstractWe report our systematic survey observations of protostellar sources with the SubMillimeter Array (SMA) and Atacama Large Millimeter/submillimeter Array (ALMA). The purpose of our survey is to investigate formation mechanism of protoplanetary disks, precursors of planetary systems, out of ~1000 AU-scale protostellar envelopes surrounding the protostars. We found that in the early protostars (B335, NGC1333 IRAS 4B), the envelopes do not show significant rotating motions but infalling motions toward the central protostars. In more evolved protostars (L1527 IRS, L1448-mm, L1551 IRS 5), the envelopes are infalling and rotating with the conserved specific angular momenta (that is, vrot ∝ r−1). In most evolved sources (L1551 NE, TMC-1A, L1489 IRS) large-scale (≳100 AU) disks in Keplerian rotation or protoplanetary disks are evident. These results demonstrate a systematic evolutionary trend of envelope gas motions toward the disk formation.
Central Molecular Zone of the Milky Way: Star Formation in an extreme Environment
Authors: Kauffmann Jens 
Published: September 2016

AbstractThe Central Molecular Zone (CMZ; inner ~100 pc) hosts some of the most dense and massive molecular clouds of the Milky Way. These clouds might serve as local templates for dense clouds seen in nearby starburst galaxies or in the early universe. The clouds have a striking feature: they form stars at a very slow pace, considering their mass and high average density. Here we use interferometer data from ALMA and the SMA to show that this slow star formation is a consequence of the cloud density structure: CMZ clouds have a very flat density structure. They might, for example, exceed the average density of the Orion A molecular cloud by an order of magnitude on spatial scales ~5 pc, but CMZ “cores” of ~0.1 pc radius have masses and densities lower than what is found in the Orion KL region. This absence of highest–density gas probably explains the suppression of star formation. The clouds are relatively turbulent, and ALMA observations of H2CO and SiO indicate that the turbulence is induced by high–velocity shocks. We speculate that these shocks might prevent the formation of high–mass cores. It has been argued that the state of CMZ clouds depends on their position along the orbit around Sgr A*. Our incomplete data indicate no evolution in the density structure, and only a modest evolution in star formation activity per unit mass.
Local Physics and Star Formation in Galaxies
Authors: Leroy Adam K. , Bigiel Frank , Hughes Annie , Schinnerer Eva , Usero Antonio ,   the PAWS, EMPIRE, and HERACLES Dense Gas Collaborations
Published: September 2016

AbstractA next main step in understanding star formation is to link the sharp but narrow view of Galactic molecular cloud studies to the wider context accessed by less detail by extragalactic work. In this proceeding, we discuss how new technology and large programs at millimeter wavelengths are improving our ability to access physical conditions in the interstellar medium (ISM) of other galaxies. We highlight results from the multi-line survey of Usero et al. (2015), which measured density sensitive lines across nearby galaxy disks, and two new mapping studies of M51: the high resolution Plateau de Bure Arcsecond Whirlpool Survey (PAWS) and the EMPIRE multi-line mapping survey. These results argue for a context-dependent role for gas density in star formation; that is, gas at a particular density does not appear to form stars in a universal way. They also demonstrate the influence of cloud-scale conditions, especially surface density and the velocity dispersion, in setting the small-scale density distribution and highlight gravitational boundedness as a main driver of the ability of gas to form stars. Beyond these specific results, we argue that ability to gauge detailed physical conditions in the star-forming gas of other galaxies promises major advances that will help unify the fields of Galactic and extragalactic star formation in the next few years.
How does metallicity affect the gas and dust properties of galaxies?
Authors: Madden Suzanne C. , Cormier Diane , Rémy-Ruyer Aurélie 
Published: September 2016

AbstractComparison of the ISM properties of a wide range of metal poor galaxies with normal metal-rich galaxies reveals striking differences. We find that the combination of the low dust abundance and the active star formation results in a very porous ISM filled with hard photons, heating the dust in dwarf galaxies to overall higher temperatures than their metal-rich counterparts. This results in photodissociation of molecular clouds to greater depths, leaving relatively large PDR envelopes and difficult-to-detect CO cores. From detailed modeling of the low-metallicity ISM, we find significant fractions of CO-dark H2 - a reservoir of molecular gas not traced by CO, but present in the [CII] and [CI]-emitting envelopes. Self-consistent analyses of the neutral and ionized gas diagnostics along with the dust SED is the necessary way forward in uncovering the multiphase structure of galaxies.
AGN feedback and star formation in ETGs: negative and positive feedback
Authors: Ciotti Luca , Ostriker Jeremiah P. , Negri Andrea , Pellegrini Silvia , Posacki Silvia , Novak Greg 
Published: September 2016

AbstractAGN feedback from supermassive black holes (SMBHs) at the center of early type galaxies is commonly invoked as the explanation for the quenching of star formation in these systems. The situation is complicated by the significant amount of mass injected in the galaxy by the evolving stellar population over cosmological times. In absence of feedback, this mass would lead to unobserved galactic cooling flows, and to SMBHs two orders of magnitude more massive than observed. By using high-resolution 2D hydrodynamical simulations with radiative transport and star formation in state-of-the-art galaxy models, we show how the intermittent AGN feedback is highly structured on spatial and temporal scales, and how its effects are not only negative (shutting down the recurrent cooling episodes of the ISM), but also positive, inducing star formation in the inner regions of the host galaxy.
High Mass Star Formation: Properties of NH3 clumps in Southern Galactic Plane
Authors: Akhter Shaila , Cunningham Maria R. , Harvey-Smith Lisa , Nawaz Mohammad Ali , Jones Paul A. , Purcell Cormac , Walsh Andrew 
Published: September 2016

AbstractMassive stars are some of the most important objects in the Universe, shaping the evolution of galaxies, creating chemical elements, and hence shaping the evolution of the Universe. However, the processes by which they form, and how they shape their environment during their birth processes, are not well understood. We are using NH3 data from the “The H2O Southern Galactic Plane Survey” (HOPS) to define the positions of dense cores/clumps of gas in the southern Galactic plane that are likely to form stars. We did a comparative study with different methods for finding clumps and found Fellwalker to be the best for this dataset. We detected ~ 500 clumps with mean kinetic temperature ~ 20 K and virial mass ~ 680 solar masses.
A supernova scenario for magnetic fields and rotation measures in galaxies
Authors: Beck Alexander M. , Dolag Klaus 
Published: September 2016

AbstractWe present a model for the seeding and evolution of magnetic fields in galaxies by supernovae (SN). SN explosions during galaxy assembly provide seed fields, which are subsequently amplified by compression, shear flows and random motions. Our model explains the origin of μG magnetic fields within galactic structures. We implement our model in the MHD version of the cosmological simulation code Gadget-3 and couple it with a multi-phase description of the interstellar medium. We perform simulations of Milky Way-like galactic halo formation and analyze the distribution and strength of the magnetic field. We investigate the intrinsic rotation measure (RM) evolution and find RM values exceeding 1000 rad/m2 at high redshifts and RM values around 10 rad/m2 at present-day. We compare our simulations to a limited set of observational data points and find encouraging similarities. In our model, galactic magnetic fields are a natural consequence of the very basic processes of star formation and galaxy assembly.
Detection and measurement of expanding ionized shells around young star clusters
Authors: Beckman John , Fariña Artemi Camps , Cardiel Javier Zaragoza , Font Joan 
Published: September 2016

AbstractWe present a new method (BUBBLY) for detecting expanding components of ionized gas using integral field spectroscopy, showing its capabilities not only in detecting but also in obtaining the key physical parameters of the expanding shells: their expansion velocities and masses. The main advantages are that the detection is performed automatically via software and that we can derive most parameters of the shells, so it is suitable for detailed studies of feedback in nearby galaxies. The software can easily be configured to run on any data cube mapping an emission line over a spatial field. We also present results obtained by running BUBBLY on observations of Hα emission with the Fabry-Perot spectrograph GHαFaS: two sets of spectacular results at widely different spatial scales: the Antennae galaxies show multiple giant bubbles of size ~300pc around the brightest clusters, while inside a region in M33 we find three nested supernova remnants, with which we can study the feedback on the molecular gas surrounding the cluster.
A Statistical Comparison of the Near Infrared Emission with the Hα Emission from the HII regions of NGC4321, NGC4736 and NGC4254
Authors: Beckman J.E. , Chan S.J. , Li A. , Borissova J. 
Published: September 2016

AbstractWe report on our ongoing project “Statistical studies of HII regions in the nearby extra-galaxies”. We present an overview of our detailed study of warm dust in the nearby Galaxy NGC 4321 (M100), measuring the flux values in the 4 Spitzer-IRAC bands of some 275 HII regions in M100. In addition, we present new measurements of the flux values in the 4 Spitzer-IRAC bands of a complete sample of 70 isolated luminous HII regions in NGC 4736 and 157 regions in NGC 4254. We study the relations between the Hα luminosity and the near-IR luminosity and temperature of HII regions in the three galaxies. We estimate the near-IR luminosities and compare them with the Hα luminosities from archive and literature sources. We find a linear relation between the Hα luminosity and the IRAC luminosity for the HII regions, but no apparent relation between the luminosity and the colour temperature of the regions in any of the three galaxies. The colour temperatures of regions especially in M100 and NGC4254 are confined to a surprisingly narrow range, with a small fraction forming a higher temperature tail to the distribution. These results give new insight into the size function and the 3D distribution of the dust in these regions, and we propose scenarios to explain them.
Time evolution of chemistry with fixed physical parameters in TMC-1
Authors: Berczik Peter , Bertsyk Peter , Fehér Orsolya , Harju Jorma , Onishi Toshikazu , Tóth L. Viktor 
Published: September 2016

AbstractWe present a set of time dependent chemical evolution models (based on the UMIST† astrochemistry 2012 code, Woodall et al. (2007); McElroy et al. (2013) for a range of initial physical cloud parameters: 10 K < T < 20 K; 103 cm−3 < n(H2) < 5 · 104 cm−3; 1 < AV < 10 and with estimated values of scaled interstellar ultraviolet radiation field. Our computation model included the full UMIST gas-phase reaction network for 467 species Garrod et al. (2008), Graedel et al. (1982). We compare our chemical model results with the relative abundances of: CO, CH, OH, HCO+, HCN, HNC, NH3, N2H+ and H2CO molecules. We find significant time dependent variations of the chemical ratios of: X(NH3/H2); X(HCO+/H2) and X(HCO+/NH3). We derive an ammonia age spread for the parts of TMC-1 (Taurus Molecular Cloud-1) that looks more complex than previous estimated showed. Age estimates based on X(NH3/H2); X(HCO+/H2) and X(HCO+/NH3) were compared in 3 selected positions, and were found to be very similar (with ±9% differences).
Quantifying the Magnetic Alignment of Hi and Dust in the Diffuse ISM
Authors: Clark S.E. , Peek J.E.G. , Hill J. Colin , Putman M.E. 
Published: September 2016

AbstractSensitive, high resolution observations of Galactic neutral hydrogen (Hi) reveal an intricate network of slender linear features, much as sensitive surveys of dust in Galactic molecular clouds reveal ubiquitous filamentary structure. Across the high Galactic latitude sky, diffuse Histructures are aligned with the interstellar magnetic field, as revealed by background starlight polarization (Clark, Peek, & Putman 2014) and by Planck 353 GHz polarized dust emission (Clark et al. 2015). These discoveries were enabled by the Rolling Hough Transform, a recently developed, open source machine vision algorithm.