bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extreme Debris Disk Variability: Exploring the Diverse Outcomes of Large Asteroid Impacts During the Era of Terrestrial Planet Formation
Authors: Su Kate Y. L. , Jackson Alan P. , Gáspár András , Rieke George H. , Dong Ruobing , Olofsson Johan , Kennedy G. M. , Leinhardt Zoë M. , Malhotra Renu , Hammer Michael , Meng Huan Y. A. , Rujopakarn W. , Rodriguez Joseph E. , Pepper Joshua , Reichart D. E. , James David , Stassun Keivan G. 
Published: April 2019

Abstract
The most dramatic phases of terrestrial planet formation are thought to be oligarchic and chaotic growth, on timescales of up to 100–200 Myr, when violent impacts occur between large planetesimals of sizes up to protoplanets. Such events are marked by the production of large amounts of debris, as has been observed in some exceptionally bright and young debris disks (termed extreme debris disks). Here we report five years of Spitzer measurements of such systems around two young solar-type stars: ID8 and P1121. The short-term (weekly to monthly) and long-term (yearly) disk variability is consistent with the aftermaths of large impacts involving large asteroid-sized bodies. We demonstrate that an impact-produced clump of optically thick dust, under the influence of the dynamical and viewing geometry effects, can produce short-term modulation in the disk light curves. The long-term disk flux variation is related to the collisional evolution within the impact-produced fragments once released into a circumstellar orbit. The time-variable behavior observed in the P1121 system is consistent with a hypervelocity impact prior to 2012 that produced vapor condensates as the dominant impact product. Two distinct short-term modulations in the ID8 system suggest two violent impacts at different times and locations. Its long-term variation is consistent with the collisional evolution of two different populations of impact-produced debris dominated by either vapor condensates or escaping boulders. The bright, variable emission from the dust produced in large impacts from extreme debris disks provides a unique opportunity to study violent events during the era of terrestrial planet formation.
Orbital Deflection of Comets by Directed Energy
Authors: Zhang Qicheng , Lubin Philip M. , Hughes Gary B. 
Published: April 2019

Abstract
Cometary impacts pose a long-term hazard to life on Earth. Impact mitigation techniques have been studied extensively, but they tend to focus on asteroid diversion. Typical asteroid interdiction schemes involve spacecraft physically intercepting the target, a task feasible only for targets identified decades in advance and in a narrow range of orbits—criteria unlikely to be satisfied by a threatening comet. Comets, however, are naturally perturbed from purely gravitational trajectories via solar heating of their surfaces, which activates sublimation-driven jets. Artificial heating of a comet, such as by a laser, may supplement natural heating by the Sun to purposefully manipulate its path and thereby avoid an impact. Deflection effectiveness depends on the comet’s heating response, which varies dramatically depending on factors including nucleus size, orbit, and dynamical history. These factors are incorporated into a numerical orbital model to assess the effectiveness and feasibility of using high-powered laser arrays in Earth orbit and on the ground for comet deflection. Simulation results suggest that a diffraction-limited 500 m orbital or terrestrial laser array operating at 10 GW for 1% of each day over 1 yr is sufficient to fully avert the impact of a typical 500 m diameter comet with primary nongravitational parameter A
1 = 2 × 10−8 au day−2. Strategies to avoid comet fragmentation during deflection are also discussed.
Parallaxes for Star-forming Regions in the Inner Perseus Spiral Arm
Authors: Zhang Bo , Reid Mark J. , Zhang Lian , Wu Yuanwei , Hu Bo , Sakai Nobuyuki , Menten Karl M. , Zheng Xingwu , Brunthaler Andreas , Dame Thomas M. , Xu Ye 
Published: April 2019

Abstract
We report trigonometric parallax and proper motion measurements of 6.7 GHz CH3OH and 22 GHz H2O masers in eight high-mass star-forming regions (HMSFRs) based on Very Long Baseline Array (VLBA) observations as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey. The distances of these HMSFRs combined with their Galactic coordinates, radial velocities, and proper motions, allow us to assign them to a segment of the Perseus arm with ℓ ≲ 70°. These HMSFRs are clustered in Galactic longitude from ≈30° to ≈50° neighboring a dearth of such sources between longitudes ≈50° to ≈90°.
Dicarbon Formation in Collisions of Two Carbon Atoms
Authors: Babb James F. , Smyth R. T. , McLaughlin B. M. 
Published: April 2019

Abstract
Radiative association cross sections and rates are computed, using a quantum approach, for the formation of C2 molecules (dicarbon) during the collision of two ground-state C(3
P) atoms. We find that transitions originating in the C 1Π
g
, d 3Π
g
, and 1 5Π
u
states are the main contributors to the process. The results are compared and contrasted with previous results obtained from a semiclassical approximation. New ab initio potential curves and transition dipole moment functions have been obtained for the present work using the multi-reference configuration interaction approach with the Davidson correction (MRCI+Q) and aug-cc-pCV5Z basis sets, substantially increasing the available molecular data on dicarbon. Applications of the current computations to various astrophysical environments and laboratory studies are briefly discussed, focusing on these rates.
Evidence for a Young Stellar Population in Nearby Type 1 Active Galaxies
Authors: Kim Minjin , Ho Luis C. 
Published: April 2019

Abstract
To understand the physical origin of the close connection between supermassive black holes (BHs) and their host galaxies, it is vital to investigate star formation properties in active galaxies. Using a large data set of nearby type 1 active galactic nuclei (AGNs) with detailed structural decomposition based on high-resolution optical images obtained with the Hubble Space Telescope, we study the correlation between BH mass and bulge luminosity and the (Kormendy) relation between bulge effective radius and surface brightness. In both relations, the bulges of type 1 AGNs tend to be more luminous than those of inactive galaxies with the same BH mass or the same bulge size. This suggests that the central regions of AGN host galaxies have characteristically lower mass-to-light ratios than inactive galaxies, most likely due to the presence of a younger stellar population in active systems. In addition, the degree of luminosity excess appears to be proportional to the accretion rate of the AGN, revealing a physical connection between stellar growth and BH growth. Adopting a simple toy model for the increase of stellar mass and BH mass, we show that the fraction of young stellar population flattens out toward high accretion rates, possibly reflecting the influence of AGN-driven feedback.
Detection of a White Dwarf Companion to a Blue Straggler Star in the Outskirts of Globular Cluster NGC 5466 with the Ultraviolet Imaging Telescope (UVIT)
Authors: Sahu Snehalata , Subramaniam Annapurni , Simunovic Mirko , Postma J. , Côté Patrick , Rao N. Kameswera , Geller Aaron M. , Leigh Nathan , Shara Michael , Puzia Thomas H. , Stetson Peter B. 
Published: April 2019

Abstract
We report the discovery of a hot white dwarf (WD) companion to a blue straggler star (BSS) in the globular cluster (GC) NGC 5466, based on observations from the Ultra-Violet Imaging Telescope (UVIT) on board AstroSat. The Spectral Energy Distribution (SED) of the Far-UV detected BSS NH 84 was constructed by combining the flux measurements from four filters of UVIT, with GALEX, GAIA, and other ground-based observations. The SED of NH 84 reveals the presence of a hot companion to the BSS. The temperature and radius of the BSS (T

K, R/R

) derived from Gemini spectra and SED fitting using Kurucz atmospheric models are consistent with each other. The temperature and radius of the hotter companion of NH 84 (T

K, R/R

) derived by fitting Koester WD models to the SED suggest that it is likely to be a hot WD. The radial velocity derived from the spectra along with the proper motion from GAIA DR2 confirms NH 84 to be a kinematic member of the cluster. This is the second detection of a BSS-WD candidate in a GC, and the first in the outskirts of a low-density GC. The location of this BSS in NGC 5466 along with its dynamical age supports the mass-transfer pathway for BSS formation in low-density environments.
Unbiased Cosmological Parameter Estimation from Emission-line Surveys with Interlopers
Authors: Grasshorn Gebhardt Henry S. , Jeong Donghui , Awan Humna , Bridge Joanna S. , Ciardullo Robin , Farrow Daniel , Gebhardt Karl , Hill Gary J. , Komatsu Eiichiro , Molina Mallory , Paulino-Afonso Ana , Saito Shun , Schneider Donald P. , Zeimann Greg 
Published: April 2019

Abstract
The galaxy catalogs generated from low-resolution emission-line surveys often contain both foreground and background interlopers due to line misidentification, which can bias the cosmological parameter estimation. In this paper, we present a method for correcting the interloper bias by using the joint analysis of auto- and cross-power spectra of the main and the interloper samples. In particular, we can measure the interloper fractions from the cross-correlation between the interlopers and survey galaxies, because the true cross-correlation must be negligibly small. The estimated interloper fractions, in turn, remove the interloper bias in the cosmological parameter estimation. For example, in the Hobby–Eberly Telescope Dark Energy Experiment low-redshift (z < 0.5) [O ii] λ3727Å emitters contaminate high-redshift (1.9 < z < 3.5) Lyα line emitters. We demonstrate that the joint-analysis method yields a high signal-to-noise ratio measurement of the interloper fractions while only marginally increasing the uncertainties in the cosmological parameters relative to the case without interlopers. We also show that the same is true for the high-latitude spectroscopic survey of the Wide-field Infrared Survey Telescope mission where contamination occurs between the Balmer-α line emitters at lower redshifts (1.1 < z < 1.9) and oxygen ([O iii] λ5007Å) line emitters at higher redshifts (1.7 < z < 2.8).
Constraining the Tail End of Reionization Using Lyα Transmission Spikes
Authors: Garaldi Enrico , Gnedin Nickolay Y. , Madau Piero 
Published: April 2019

Abstract
We investigate Lyα transmission spikes at z > 5 in synthetic quasar spectra and discuss their connection to the properties of the intergalactic medium and their ability to constrain reionization models. We use state-of-the-art radiation-hydrodynamic simulations from the Cosmic Reionization On Computers series to predict the number of transmission spikes as a function of redshift, both in the ideal case of infinite spectral resolution and in a realistic observational setting. Transmission spikes are produced in highly ionized underdense regions located in the vicinity of UV sources. We find that most of the predicted spikes are unresolved by current observations and show that our mock spectra are consistent with observations of the quasar ULAS J1120+0641 in about 15% of the realizations. The spike height correlates with both the gas density and the ionized fraction, but the former link is erased when synthetic spectra are smoothed to realistically achievable spectral resolutions. There exists a linear relationship between spike width and the extent of the associated underdense region, with a slope that is redshift dependent. In agreement with observations, the spike transmitted flux is suppressed at small distance from bright galaxies as these reside in overdense regions. We argue that this anticorrelation can be used to constrain large-scale density modes.
Noncircular Motions in the Outer Perseus Spiral Arm
Authors: Sakai Nobuyuki , Reid Mark J. , Menten Karl M. , Brunthaler Andreas , Dame Thomas M. 
Published: April 2019

Abstract
We report measurements of parallax and proper motion for five 6.7 GHz methanol maser sources in the outer regions of the Perseus arm as part of the BeSSeL Survey of the Galaxy. By combining our results with previous astrometric results, we determine an average spiral arm pitch angle of 9.°2 ± 1.°5 and an arm width of 0.39 kpc for this spiral arm. For sources on the interior side of the Perseus arm, we find on average a radial inward motion in the Galaxy of 13.3 ± 5.4 km s−1 and counter to Galactic rotation of 6.2 ± 3.2 km s−1. These characteristics are consistent with models for spiral arm formation that involve gas entering an arm to be shocked and then to form stars. However, similar data for other spiral arms do not show similar characteristics.
Hydrodynamical Models of Protoplanetary Nebulae Including the Photoionization of the Central Star
Authors: Estrella-Trujillo D. , Hernández-Martínez L. , Velázquez P. F. , Esquivel A. , Raga A. C. 
Published: April 2019

Abstract
We have carried out 3D hydrodynamic simulations of a precessing jet/counterjet ejection. We have included the photoionization from the central source, considering three different ionizing photon rates (

, 1046, and 1047 phots s−1), in order to determine its effect on the morphology and kinematics of the protoplanetary nebula. We have considered a time-dependent ejection density that generates dense knot structures in the jet, which are then partially photoionized by the ionizing photon field from the central source. We also explore the role of the medium in which the jet is propagated, under these conditions. The photoionization results in a larger Hα emission of the knots, and in an acceleration of the knots as a result of the so-called “rocket effect.” We find that for larger values of the ionizing photon rate, a clear outwards acceleration of the knots is produced. These models are appropriate for explaining protoplanetary nebulae in which such outwards accelerations are observed.
On Neutron Star Mergers as the Source of r-process-enhanced Metal-poor Stars in the Milky Way
Authors: Safarzadeh Mohammadtaher , Sarmento Richard , Scannapieco Evan 
Published: April 2019

Abstract
We model the history of Galactic r-process enrichment using high-redshift, high-resolution zoom cosmological simulations of a Milky Way–type halo. We assume that all r-process sources are neutron star mergers (NSMs) with a power-law delay time distribution. We model the time to mix pollutants at subgrid scales, which allows us to better compute the properties of metal-poor (MP) and carbon-enhanced metal-poor (CEMP) stars, along with statistics of their r-process-enhanced subclasses. Our simulations underpredict the cumulative ratios of r-process-enhanced MP and CEMP stars (MP-r, CEMP-r) over MP and CEMP stars by about one order of magnitude, even when the minimum coalescence time of the double neutron stars (DNSs), t
min, is set to 1 Myr. No r-process-enhanced stars form if t
min = 100 Myr. Our results show that even when we adopt the r-process yield estimates observed in GW170817, NSMs by themselves can only explain the observed frequency of r-process-enhanced stars if the birth rate of DNSs per unit mass of stars is boosted to

.
Time Evolution of Broadband Nonthermal Emission from Supernova Remnants in Different Circumstellar Environments
Authors: Yasuda Haruo , Lee Shiu-Hang 
Published: April 2019

Abstract
Supernova remnants (SNRs) are thought to be one of the major acceleration sites of galactic cosmic rays and an important class of objects for high-energy astrophysics. SNRs produce multiwavelength, nonthermal emission via accelerated particles at collisionless shocks generated by the interactions between the SN ejecta and the circumstellar medium (CSM). Although it is expected that the rich diversities observed in supernovae (SNe) and their CSM can result in distinct very high energy (VHE) electromagnetic signals in the SNR phase, there are only a handful of SNRs observed in both GeV and TeV γ-rays so far. A systematic understanding of particle acceleration at SNRs in different ambient environments is therefore limited. Here we explore nonthermal emission from SNRs in various circumstellar environments up to 5000 yr from explosion using hydrodynamical simulations coupled with efficient particle acceleration. We find that time evolution of emission characteristics in the VHE regime is mainly dictated by two factors: the number density of the target particles and the amplified magnetic field in the shocked medium. We also predict that the Cherenkov Telescope Array (CTA) will have sufficient sensitivity to detect VHE γ-rays from most young SNRs at distances ≲5.0 kpc. Future SNR observations with CTA will thus be promising for probing the CSM environment of SNe and hence their progenitor properties, including the mass-loss history of massive stars.
A Survey of C2H, HCN, and C18O in Protoplanetary Disks
Authors: Bergner Jennifer B. , Öberg Karin I. , Bergin Edwin A. , Loomis Ryan A. , Pegues Jamila , Qi Chunhua 
Published: April 2019

Abstract
Molecular lines observed toward protoplanetary disks carry information about physical and chemical processes associated with planet formation. We present ALMA Band 6 observations of C2H, HCN, and C18O in a sample of 14 disks spanning a range of ages, stellar luminosities, and stellar masses. Using C2H and HCN hyperfine structure fitting and HCN/H13CN isotopologue analysis, we extract optical depth, excitation temperature, and column density radial profiles for a subset of disks. C2H is marginally optically thick (τ ∼ 1–5) and HCN is quite optically thick (τ ∼ 5–10) in the inner 200 au. The extracted temperatures of both molecules are low (10–30 K), indicative of either subthermal emission from the warm disk atmosphere or substantial beam dilution due to chemical substructure. We explore the origins of C2H morphological diversity in our sample using a series of toy disk models and find that disk-dependent overlap between regions with high UV fluxes and high atomic carbon abundances can explain a wide range of C2H emission features (e.g., compact versus extended and ringed versus ringless emission). We explore the chemical relationship between C2H, HCN, and C18O and find a positive correlation between C2H and HCN fluxes but no relationship between C2H or HCN with C18O fluxes. We also see no evidence that C2H and HCN are enhanced with disk age. C2H and HCN seem to share a common driver; however, more work remains to elucidate the chemical relationship between these molecules and the underlying evolution of C, N, and O chemistries in disks.
Le « Fil rouge ». Outil de recueil et de transmission d’informations pour des jeunes bénéficiant d’une mesure d’aide ou de protection
Authors: Lambert Marie-France , Staquet Pascale 
Published: April 2019

Cet article présente le Fil rouge, un outil élaboré au sein d’une plate-forme d’intervenants de la région bruxelloise, et destiné à recueillir et transmettre les informations relatives aux enfants placés. Il est constitué de plusieurs sections : une ligne de vie, un génogramme, un répertoire, une anamnèse et un résumé du travail des intervenants successifs. Il sauvegarde les informations et les événements concernant l’enfant ainsi que ses relations avec sa famille.	Trois vignettes illustrent l’utilité du Fil rouge pour les bénéficiaires qui y contribuent et pour les professionnels qui se le transmettent. L’enfant, l’adolescent ou l’adulte ont la possibilité d’y retrouver des éléments nécessaires pour pouvoir comprendre leur histoire et les interventions qui les concernent.
Using an Intraprofessional Global Immersion to Foster Role Formation in Nursing Students
Authors: Ferrillo Heather , Watson Sherylyn M. 
Published: April 2019

Background:
Nursing programs are instrumental in developing the knowledge, skills, and attitudes necessary for nursing practice. Opportunities are lacking for role formation for successful transition into practice.

Method:
An intraprofessional global clinical immersion program was utilized as the setting for students to develop their role identity. Students from each level of nursing traveled to Jamaica to participate in a clinical immersion experience. Students participated in structured collaboration among students in different programs and acted as the instrument other students utilized to develop their role. Students had the opportunity to work with each other every day, and they provided authentic feedback for each other on their role-formation process.

Results:
Program evaluation revealed that the immersion helped students gain confidence in their roles as they transition into practice.

Conclusion:

Results of this evaluation support the sustainability of the structured global immersion experiences for professional role formation.

[
J Nurs Educ.
2019;58(5):294–297.]
Analysis the Efficient Energy Prediction for 5G Wireless Communication Technologies
Authors: Alrikabi Haider TH. , Alaidi Abdul Hadi M. , Abdalrada Ahmad Shaker , Abed Faisal Theyab 
Published: April 2019

With the growth of technological devices, gadgets and utility products in routine life, there is need to escalate the energy optimization with higher degree of accuracy and performance. Earlier the 4G networks were used are quite prominent and the wireless scientists are working ahead towards the direction of 5G. In 5G based next-generation networks there are the projected features to transmit the huge amount of data and signals to the different locations whether to short or distant locations. The energy optimization, preservation and harvesting are key perspectives of research in advance gadgets in which the key focus is to minimize the energy loss and escalate the overall life period time of the network environment. These gadgets include assorted sensor nodes which communicate to each other using clustering and sharing of signals with the overall collaboration on the specific domain. In this manuscript, the mechanisms and methodologies for the energy parameter in the 5G networks are presented so that the greater accuracy and throughput can be obtained. In addition, a comparison has been established among the old classical network generations and the new 5G networks. The comparison is done predictably in terms of data rate, Latency, Mobility, Energy, and Efficiency of Spectrum. These specifications of the various network generations have been compared in order understand and highlight the benefits and advantages of the new coming generation (5G) over the features of the traditional network generations. Moreover, this paper is intended to show the challenges and related issues might be faced to achieve the implementation of the features and specifications of the new generation technology (5G). As a result, the new ( 5G ) will be more efficient and effective in terms of high data transfer rate, low latency, Mobility, and Energy. This is very important because it draws a road map for many exciting technologies and infrastructures including Internet of Things (IOT) , remote control of industrial machinery and robotics, and much faster download speed. Thus, 5G will support carrying huge amount of data faster which will help to support smarter and reliable technology infrastructures and environment.
Keywords: 5G, wireless communications, New Radio, Mechanisms Prediction of energy, River Formation Dynamics (RFD), Nature Inspired Approach (NIA), Chanal State Information (CSI).