bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamma-Ray Burst Jet Breaks Revisited
Authors: Wang Xiang-Gao , Zhang Bing , Liang En-Wei , Lu Rui-Jing , Lin Da-Bin , Li Jing , Li Long 
Published: June 2018

Abstract
Gamma-ray Burst (GRB) collimation has been inferred with the observations of achromatic steepening in GRB light curves, known as jet breaks. Identifying a jet break from a GRB afterglow light curve allows a measurement of the jet opening angle and true energetics of GRBs. In this paper, we re-investigate this problem using a large sample of GRBs that have an optical jet break that is consistent with being achromatic in the X-ray band. Our sample includes 99 GRBs from 1997 February to 2015 March that have optical and, for Swift GRBs, X-ray light curves that are consistent with the jet break interpretation. Out of the 99 GRBs we have studied, 55 GRBs are found to have temporal and spectral behaviors both before and after the break, consistent with the theoretical predictions of the jet break models, respectively. These include 53 long/soft (Type II) and 2 short/hard (Type I) GRBs. Only 1 GRB is classified as the candidate of a jet break with energy injection. Another 41 and 3 GRBs are classified as the candidates with the lower and upper limits of the jet break time, respectively. Most jet breaks occur at 90 ks, with a typical opening angle θ

j
= (2.5 ± 1.0)°. This gives a typical beaming correction factor

f

b

−
1

∼
1000

for Type II GRBs, suggesting an even higher total GRB event rate density in the universe. Both isotropic and jet-corrected energies have a wide span in their distributions: log(E

γ,iso/erg) = 53.11 with σ = 0.84; log(E
K,iso/erg) = 54.82 with σ = 0.56; log(E

γ
/erg) = 49.54 with σ = 1.29; and log(E
K/erg) = 51.33 with σ = 0.58. We also investigate several empirical correlations (Amati, Frail, Ghirlanda, and Liang–Zhang) previously discussed in the literature. We find that in general most of these relations are less tight than before. The existence of early jet breaks and hence small opening angle jets, which were detected in the Swfit era, is most likely the source of scatter. If one limits the sample to jet breaks later than 104 s, the Liang–Zhang relation remains tight and the Ghirlanda relation still exists. These relations are derived from Type II GRBs, and Type I GRBs usually deviate from them.
Effects of Anomalous Cosmic Rays on the Structure of the Outer Heliosphere
Authors: Guo Xiaocheng , Florinski Vladimir , Wang Chi 
Published: June 2018

Abstract
Based on Voyager 1 observations, some anomalous cosmic rays (ACRs) may have crossed the heliopause and escaped into the interstellar medium, providing a mechanism of energy transfer between the inner and outer heliosheaths that is not included in conventional magnetohydrodynamics (MHD) models. In this paper, we study the effect of energetic particles’ escape through the heliopause on the size and shape of the heliosphere using a simple model that includes diffusive transport of cosmic rays. We show that the presence of ACRs significantly changes the heliosphere structure, including the location of the heliopause and termination shock. It was found that the heliopause would contract for certain values of the ACR diffusion coefficients when the diffusive particles’ pressure is comparable to the pressure of the plasma background. The difference in Voyager 1 and 2 observations of energetic particles during their respective termination shock crossings is interpreted here as due to the differences in diffusion environments during the different phases of the solar cycle. The shorter period of enhanced ACR intensities upstream of the shock measured by Voyager 2 may have been caused by weaker radial diffusive transport compared with the time of Voyager 1 crossing. We conclude that ACR diffusive effects could be prominent and should be included in MHD models of the heliosphere.
The First Empirical Determination of the Fe10+ and Fe13+ Freeze-in Distances in the Solar Corona
Authors: Boe Benjamin , Habbal Shadia , Druckmüller Miloslav , Landi Enrico , Kourkchi Ehsan , Ding Adalbert , Starha Pavel , Hutton Joseph 
Published: June 2018

Abstract
Heavy ions are markers of the physical processes responsible for the density and temperature distribution throughout the fine-scale magnetic structures that define the shape of the solar corona. One of their properties, whose empirical determination has remained elusive, is the “freeze-in” distance (R

f
) where they reach fixed ionization states that are adhered to during their expansion with the solar wind. We present the first empirical inference of R

f
for

and

derived from multi-wavelength imaging observations of the corresponding Fe xi (

) 789.2 nm and Fe xiv (

) 530.3 nm emission acquired during the 2015 March 20 total solar eclipse. We find that the two ions freeze-in at different heliocentric distances. In polar coronal holes (CHs) R

f
is around 1.45 R
⊙ for

and below 1.25 R
⊙ for

. Along open field lines in streamer regions, R

f
ranges from 1.4 to 2 R
⊙ for

and from 1.5 to 2.2 R
⊙ for

. These first empirical R

f
values: (1) reflect the differing plasma parameters between CHs and streamers and structures within them, including prominences and coronal mass ejections; (2) are well below the currently quoted values derived from empirical model studies; and (3) place doubt on the reliability of plasma diagnostics based on the assumption of ionization equilibrium beyond 1.2 R
⊙.
Fully Kinetic Large-scale Simulations of the Collisionless Magnetorotational Instability
Authors: Inchingolo Giannandrea , Grismayer Thomas , Loureiro Nuno F. , Fonseca Ricardo A. , Silva Luis O. 
Published: June 2018

Abstract
We present two-dimensional particle-in-cell simulations of the fully kinetic collisionless magnetorotational instability (MRI) in weakly magnetized (high β) pair plasma. The central result of this numerical analysis is the emergence of a self-induced turbulent regime in the saturation state of the collisionless MRI, which can only be captured for large enough simulation domains. One of the underlying mechanisms for the development of this turbulent state is the drift-kink instability (DKI) of the current sheets resulting from the nonlinear evolution of the channel modes. The onset of the DKI can only be observed for simulation domain sizes exceeding several linear MRI wavelengths. The DKI and ensuing magnetic reconnection activate the turbulent motion of the plasma in the late stage of the nonlinear evolution of the MRI. At steady-state, the magnetic energy has an MHD-like spectrum with a slope of k
−5/3 for kρ < 1 and k
−3 for sub-Larmor scale (kρ > 1). We also examine the role of the collisionless MRI and associated magnetic reconnection in the development of pressure anisotropy. We study the stability of the system due to this pressure anisotropy, observing the development of mirror instability during the early-stage of the MRI. We further discuss the importance of magnetic reconnection for particle acceleration during the turbulence regime. In particular, consistent with reconnection studies, we show that at late times the kinetic energy presents a characteristic slope of ϵ
−2 in the high-energy region.
The Structure of a Quasi-Keplerian Accretion Disk around Magnetized Stars
Authors: Habumugisha Isaac , Jurua Edward , Tessema Solomon B. , Simon Anguma K. 
Published: June 2018

Abstract
In this paper, we present the complete structure of a quasi-Keplerian thin accretion disk with an internal dynamo around a magnetized neutron star. We assume a full quasi-Keplerian disk with the azimuthal velocity deviating from the Keplerian fashion by a factor of ξ (0 < ξ < 2). In our approach, we vertically integrate the radial component of the momentum equation to obtain the radial pressure gradient equation for a thin quasi-Keplerian accretion disk. Our results show that, at large radial distance, the accretion disk behaves in a Keplerian fashion. However, close to the neutron star, pressure gradient force (PGF) largely modifies the disk structure, resulting into sudden dynamical changes in the accretion disk. The corotation radius is shifted inward (outward) for ξ > 1 (for ξ < 1), and the position of the inner edge with respect to the new corotation radius is also relocated accordingly, as compared to the Keplerian model. The resulting PGF torque couples with viscous torque (when ξ < 1) to provide a spin-down torque and a spin-up torque (when ξ > 1) while in the advective state. Therefore, neglecting the PGF, as has been the case in previous models, is a glaring omission. Our result has the potential to explain the observable dynamic consequences of accretion disks around magnetized neutron stars.
Factors Influencing Clinical Performance of Baccalaureate Nursing Majors: A Retrospective Audit
Authors: Johnston Sandra , Fox Amanda , Coyer Fiona Maree 
Published: June 2018

Background:
Transition of nursing student to new graduate depends on successful completion of clinical work placement during an undergraduate course. Supporting students during the clinical placement is imperative. This study examined associations between grade point average, domestic or international status, course entry qualification, and single or dual nursing degree to successful completion of clinical placement.

Method:
A retrospective audit of 665 students in a baccalaureate nursing program was conducted to examine factors influencing clinical performance of baccalaureate nursing students.

Results:

A significant association between entry qualification, lower grade point average, international status, and receipt of a constructive note was found: χ
2
= 8.678,
df
= 3,
p
= .034,
t
(3.862),
df
= 663,
p
⩽ .001, and Fisher's exact test = 8.581,
df
= 1,
p
= .003, respectively.

Conclusion:

Understanding factors that affect clinical performance may help early identification of students at risk and allow for supportive intervention during placement and subsequent program completion. [
J Nurs Educ.
2018;57(6):333–338.]
Generating Gratitude in the Workplace to Improve Faculty Job Satisfaction
Authors: Stegen Amy , Wankier Jamie 
Published: June 2018

Background:
The current nursing shortage affects all settings. In an effort to promote retention of nursing faculty, an “attitude of gratitude” was cultivated to improve job satisfaction and increase collaboration in one school of nursing.

Method:
This was a quantitative study using a convenience sample of faculty at one school of nursing. A presurvey of faculty on perceived gratitude levels and job satisfaction was administered prior to the start of the school year. Multiple gratitude interventions were implemented throughout the year and a postsurvey was administered to measure the effectiveness of interventions.

Results:
The findings of this study show an improvement of 17.9% in overall job satisfaction, which is consistent with other studies on the topic. Collaboration was not affected by gratitude interventions.

Conclusion:

Implementing gratitude is a cost-effective and easy way to improve job satisfaction to increase faculty retention rates. [
J Nurs Educ.
2018;57(6):375–378.]
Calabi–Yau Quotients of Hyperkähler Four-folds
Authors: Camere Chiara , Garbagnati Alice , Mongardi Giovanni 
Published: June 2018

AbstractThe aim of this paper is to construct Calabi–Yau 4-folds as crepant resolutions of the quotients of a hyperkähler 4-fold$X$by a non-symplectic involution$\unicode[STIX]{x1D6FC}$. We first compute the Hodge numbers of a Calabi–Yau constructed in this way in a general setting, and then we apply the results to several specific examples of non-symplectic involutions, producing Calabi–Yau 4-folds with different Hodge diamonds. Then we restrict ourselves to the case where$X$is the Hilbert scheme of two points on a K3 surface$S$, and the involution$\unicode[STIX]{x1D6FC}$is induced by a non-symplectic involution on the K3 surface. In this case we compare the Calabi–Yau 4-fold$Y_{S}$, which is the crepant resolution of$X/\unicode[STIX]{x1D6FC}$, with the Calabi–Yau 4-fold$Z_{S}$, constructed from$S$through the Borcea–Voisin construction. We give several explicit geometrical examples of both these Calabi–Yau 4-folds, describing maps related to interesting linear systems as well as a rational$2:1$map from$Z_{S}$to$Y_{S}$.
Potential Challenges Meeting the American Academy of Pediatrics’ Lead in School Drinking Water Goal of 1 μg/L
Authors: Parks Jeffrey , Pieper Kelsey J. , Katner Adrienne , Tang Min , Edwards Marc 
Published: June 2018

Concern about lead in drinking water has heightened since the Flint water crisis. Moreover, recent medical evidence increasingly shows damage to children’s health at levels of lead exposure once considered low. In order to better protect children from these hazards, the American Academy of Pediatrics (AAP) recommends that drinking water in public schools does not exceed 1 μg/L lead. Meeting this goal with current plumbing and fixtures will be challenging, because current “lead-free” standards did not anticipate targets this low. Three styles of recently manufactured “lead-free” faucets were tested and average lead leaching ranged from 1.5 μg/L to 3.0 μg/L after 19 d. Given that the NSF/ANSI 61 test water is less aggressive than some potable waters, even newly manufactured “lead-free” faucets may not meet the standards recommended by AAP.
Observing ice particle growth along fall streaks in mixed-phase clouds using spectral polarimetric radar data
Authors: Pfitzenmaier Lukas , Unal Christine M. H. , Dufournet Yann , Russchenberg Herman W. J. 
Published: June 2018

Abstract. The growth of ice crystals in presence of supercooled liquid droplets
represents the most important process for precipitation formation in the
mid-latitudes. However, such mixed-phase interaction processes remain relatively unknown, as capturing the complexity in cloud dynamics and microphysical
variabilities turns to be a real observational challenge. Ground-based radar
systems equipped with fully polarimetric and Doppler capabilities in high
temporal and spatial resolutions such as the S-band transportable atmospheric
radar (TARA) are best suited to observe mixed-phase growth processes. In this
paper, measurements are taken with the TARA radar during the ACCEPT campaign
(analysis of the composition of clouds with extended polarization
techniques). Besides the common radar observables, the 3-D wind field is also
retrieved due to TARA unique three beam configuration. The novelty of this
paper is to combine all these observations with a particle evolution
detection algorithm based on a new fall streak retrieval technique in order
to study ice particle growth within complex precipitating mixed-phased cloud
systems. In the presented cases, three different growth processes of ice
crystals, plate-like crystals, and needles are detected and related to the
presence of supercooled liquid water. Moreover, TARA observed signatures are
assessed with co-located measurements obtained from a cloud radar and
radiosondes. This paper shows that it is possible to observe ice particle
growth processes within complex systems taking advantage of adequate
technology and state of the art retrieval algorithms. A significant
improvement is made towards a conclusive interpretation of ice particle
growth processes and their contribution to rain production using fall streak
rearranged radar data.
Estimating grassland curing with remotely sensed data
Authors: Chaivaranont Wasin , Evans Jason P. , Liu Yi Y. , Sharples Jason J. 
Published: June 2018

Abstract. Wildfire can become a catastrophic natural hazard, especially during dry summer seasons in Australia. Severity is influenced by various meteorological, geographical, and fuel characteristics. Modified Mark 4 McArthur's Grassland Fire Danger Index (GFDI) is a commonly used approach to determine the fire danger level in grassland ecosystems. The degree of curing (DOC, i.e. proportion of dead material) of the grass is one key ingredient in determining the fire danger. It is difficult to collect accurate DOC information in the field, and therefore ground-observed measurements are rather limited. In this study, we explore the possibility of whether adding satellite-observed data responding to vegetation water content (vegetation optical depth, VOD) will improve DOC prediction when compared with the existing satellite-observed data responding to DOC prediction models based on vegetation greenness (normalised difference vegetation index, NDVI). First, statistically significant relationships are established between selected ground-observed DOC and satellite-observed vegetation datasets (NDVI and VOD) with an r2 up to 0.67. DOC levels estimated using satellite observations were then evaluated using field measurements with an r2 of 0.44 to 0.55. Results suggest that VOD-based DOC estimation can reasonably reproduce ground-based observations in space and time and is comparable to the existing NDVI-based DOC estimation models.
Seasonal monitoring of melt and accumulation within the deep percolation zone of the Greenland Ice Sheet and comparison with simulations of regional climate modeling
Authors: Heilig Achim , Eisen Olaf , MacFerrin Michael , Tedesco Marco , Fettweis Xavier 
Published: June 2018

Abstract. Increasing melt over the Greenland Ice Sheet (GrIS) recorded
over the past several years has resulted in significant changes of the percolation
regime of the ice sheet. It remains unclear whether Greenland's percolation
zone will act as a meltwater buffer in the near future through gradually
filling all pore space or if near-surface refreezing causes the formation of
impermeable layers, which provoke lateral runoff. Homogeneous ice layers
within perennial firn, as well as near-surface ice layers of several meter
thickness have been observed in firn cores. Because firn coring is a
destructive method, deriving stratigraphic changes in firn and allocation of
summer melt events is challenging. To overcome this deficit and provide
continuous data for model evaluations on snow and firn density, temporal
changes in liquid water content and depths of water infiltration, we
installed an upward-looking radar system (upGPR) 3.4 m below the snow
surface in May 2016 close to Camp Raven
(66.4779∘ N, 46.2856∘ W) at 2120 m a.s.l. The radar is
capable of quasi-continuously monitoring changes in snow and firn
stratigraphy, which occur above the antennas. For summer 2016, we observed
four major melt events, which routed liquid water into various depths beneath
the surface. The last event in mid-August resulted in the deepest percolation
down to about 2.3 m beneath the surface. Comparisons with simulations from
the regional climate model MAR are in very good agreement in terms of
seasonal changes in accumulation and timing of onset of melt. However,
neither bulk density of near-surface layers nor the amounts of liquid water
and percolation depths predicted by MAR correspond with upGPR data. Radar
data and records of a nearby thermistor string, in contrast, matched very
well for both timing and depth of temperature changes and observed water
percolations. All four melt events transferred a cumulative mass of
56 kg m−2 into firn beneath the summer surface of 2015. We find that
continuous observations of liquid water content, percolation depths and rates
for the seasonal mass fluxes are sufficiently accurate to provide valuable
information for validation of model approaches and help to develop a better
understanding of liquid water retention and percolation in perennial firn.
Logic of the Egotistical Sentence: A Reading of Descartes
Authors: Descombes Vincent 
Published: June 2018

This text is a translation of two extracts from Vincent Descombes' 2014 book Le parler de soi. The majority of the translation consists of the chapter (I.3) that Descombes dedicates to discussing Descartes extensively. In this text, Descombes analyzes “egotistical sentences,” or I-statements, beginning with the infamous example from Descartes (cogito ergo sum). From here, he develops a substantial meditation on the nature of the self and its inherent philosophical paradoxes. The “radical question” guiding Descombes is whether or not an egotistical sentence has or implies a subject in the metaphysical sense. The conclusion, ultimately supported in part by Anscombe’s work on “I-thoughts,” explains how it could be that a subject is not implied by an egotistical sentence.
As ciências sociais e as mudanças climáticas
Authors: Veltrone Allan Rogério 
Published: June 2018

ResumoA proposta do artigo é mostrar o quão importante são as ciências sociais para a compreensão das mudanças climáticas. Trata-se de um tema inegavelmente hibrido, onde os aspectos sociais da questão são tão importantes quanto as analises dos cientistas do clima. Estas análises são realizadas com o objetivo de se elaborarem ações de mitigação, que devem contar, de alguma forma, com a participação do publico. Este, no entanto, tem mais facilidade para acessar os argumentos dos chamados céticos, que são, em sua maioria, divulgadores científicos, e não cientistas. Explorando estas controvérsias, mostraremos então a relevância de algumas teorias de autores consagrados: Beck, Latour, Giddens e Hanningan.Palavras-chave: 1-Mudança Climática; 2-Sociologia da Ciência; 3-Sociologia Ambiental. AbstractThe purpose of the article is to show how important social sciences are to understanding climate change. This is an undeniably hybrid theme, where the social aspects of the issue are as important as the analyses by the climate scientists. These analyses are performed in order to develop mitigation actions, which should depend, in some way, on the participation of the public. However, it is easier to access the arguments of so-called skeptics, who are mostly science communicators, and not scientists. Exploring these controversies, we then show the relevance of some theories by renowned authors: Beck, Latour, Giddens and Hanningan.Keywords: 1-Change Climate; 2-Sociology of Science; 3-Environmental Sociology. ResumenEl propósito de este artículo es mostrar la importancia de las ciencias sociales para la comprensión de los cambios climáticos. Se trata de un tema híbrido, donde los aspectos sociales son tan importantes como los análisis de los científicos del clima. Dichos análisis se realizan con el fin de desarrollar medidas de mitigación, las cuales deben contar con la participación del público. Sin embargo, es más fácil acceder a los argumentos de los llamados escépticos que, en su mayoría, son más comunicadores de la ciencia que científicos. Luego de estudiar estas controversias, mostraremos la relevancia de algunas teorías de autores de renombre: Beck, Latour, Giddens y Hanningan.Palabras Clave: 1-Cambio Climático; 2-Sociología De La Ciencia; 3-Sociología Ambiental.