bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing the effect of resolution on gravitational fragmentation with Lagrangian hydrodynamic schemes
Authors: Yamamoto Yasuyoshi , Okamoto Takashi , Saitoh Takayuki R 
Published: April 2021

ABSTRACT
To study the resolution required for simulating gravitational fragmentation with newly developed Lagrangian hydrodynamic schemes, meshless finite-volume method (MFV) and meshless finite-mass method, we have performed a number of simulations of the Jeans test and compared the results with both the expected analytical solution and results from the more standard Lagrangian approach: smoothed particle hydrodynamics (SPH). We find that the different schemes converge to the analytical solution when the diameter of a fluid element is smaller than a quarter of the Jeans wavelength, λJ. Among the three schemes, SPH/MFV shows the fastest/slowest convergence to the analytical solution. Unlike the well-known behaviour of Eulerian schemes, none of the Lagrangian schemes investigated displays artificial fragmentation when the perturbation wavelength, λ, is shorter than λJ, even at low numerical resolution. For larger wavelengths (λ &gt; λJ), the growth of the perturbation is delayed when it is not well resolved. Furthermore, with poor resolution, the fragmentation seen with the MFV scheme proceeds very differently compared to the converged solution. All these results suggest that, when unresolved, the ratio of the magnitude of hydrodynamic force to that of self-gravity at the sub-resolution scale is the largest/smallest in MFV/SPH, the reasons for which we have discussed in detail. These tests are repeated to investigate the effect of kernels of higher order than the fiducial cubic spline. Our results indicate that the standard deviation of the kernel is a more appropriate definition of the ‘size’ of a fluid element than its compact support radius.
Scale invariance, horizons, and inflation
Authors: Maeder Andre , Gueorguiev Vesselin G 
Published: April 2021

ABSTRACTMaxwell equations and the equations of general relativity are scale invariant in empty space. The presence of charge or currents in electromagnetism or the presence of matter in cosmology are preventing scale invariance. The question arises on how much matter within the horizon is necessary to kill scale invariance. The scale-invariant field equation, first written by Dirac in 1973 and then revisited by Canuto et al. in 1977, provides the starting point to address this question. The resulting cosmological models show that, as soon as matter is present, the effects of scale invariance rapidly decline from ϱ = 0 to ϱc, and are forbidden for densities above ϱc. The absence of scale invariance in this case is consistent with considerations about causal connection. Below ϱc, scale invariance appears as an open possibility, which also depends on the occurrence of inflation in the scale-invariant context. In the present approach, we identify the scalar field of the empty space in the scale-invariant vacuum context to the scalar field φ in the energy density $\varrho = \frac{1}{2} \dot{\varphi }^2 + V(\varphi)$ of the vacuum at inflation. This leads to some constraints on the potential. This identification also solves the so-called ‘cosmological constant problem’. In the framework of scale invariance, an inflation with a large number of e-foldings is also predicted. We conclude that scale invariance for models with densities below ϱc is an open possibility; the final answer may come from high redshift observations, where differences from the ΛCDM models appear.
Stellar evolution models with entropy-calibrated mixing-length parameter: application to red giants
Authors: Spada Federico , Demarque Pierre , Kupka Friedrich 
Published: April 2021

ABSTRACT
We present evolutionary models for solar-like stars with an improved treatment of convection that results in a more accurate estimate of the radius and effective temperature. This is achieved by improving the calibration of the mixing-length parameter, which sets the length scale in the 1D convection model implemented in the stellar evolution code. Our calibration relies on the results of 2D and 3D radiation hydrodynamics simulations of convection to specify the value of the adiabatic specific entropy at the bottom of the convective envelope in stars as a function of their effective temperature, surface gravity, and metallicity. For the first time, this calibration is fully integrated within the flow of a stellar evolution code, with the mixing-length parameter being continuously updated at run-time. This approach replaces the more common, but questionable, procedure of calibrating the length scale parameter on the Sun, and then applying the solar-calibrated value in modelling other stars, regardless of their mass, composition, and evolutionary status. The internal consistency of our current implementation makes it suitable for application to evolved stars, in particular to red giants. We show that the entropy calibrated models yield a revised position of the red giant branch that is in better agreement with observational constraints than that of standard models.
Particle acceleration and non-thermal emission in colliding-wind binary systems
Authors: Pittard J M , Romero G E , Vila G S 
Published: April 2021

ABSTRACT
We present a model for the creation of non-thermal particles via diffusive shock acceleration in a colliding-wind binary. Our model accounts for the oblique nature of the global shocks bounding the wind–wind collision region and the finite velocity of the scattering centres to the gas. It also includes magnetic field amplification by the cosmic ray induced streaming instability and the dynamical back reaction of the amplified field. We assume that the injection of the ions and electrons is independent of the shock obliquity and that the scattering centres move relative to the fluid at the Alfvén velocity (resulting in steeper non-thermal particle distributions). We find that the Mach number, Alfvénic Mach number, and transverse field strength vary strongly along and between the shocks, resulting in significant and non-linear variations in the particle acceleration efficiency and shock nature (turbulent versus non-turbulent). We find much reduced compression ratios at the oblique shocks in most of our models compared to our earlier work, though total gas compression ratios that exceed 20 can still be obtained in certain situations. We also investigate the dependence of the non-thermal emission on the stellar separation and determine when emission from secondary electrons becomes important. We finish by applying our model to WR 146, one of the brightest colliding wind binaries in the radio band. We are able to match the observed radio emission and find that roughly 30 per cent of the wind power at the shocks is channelled into non-thermal particles.
SDSS-IV MaNGA: 3D spin alignment of spiral and S0 galaxies
Authors: Kraljic Katarina , Duckworth Christopher , Tojeiro Rita , Alam Shadab , Bizyaev Dmitry , Weijmans Anne-Marie , Boardman Nicholas Fraser , Lane Richard R 
Published: April 2021

ABSTRACT
We investigate the 3D spin alignment of galaxies with respect to the large-scale filaments using the MaNGA survey. The cosmic web is reconstructed from the Sloan Digital Sky Survey using disperse and the 3D spins of MaNGA galaxies are estimated using the thin disc approximation with integral field spectroscopy kinematics. Late-type spiral galaxies are found to have their spins parallel to the closest filament’s axis. The alignment signal is found to be dominated by low-mass spirals. Spins of S0-type galaxies tend to be oriented preferentially in perpendicular direction with respect to the filament’s axis. This orthogonal orientation is found to be dominated by S0s that show a notable misalignment between their kinematic components of stellar and ionized gas velocity fields and/or by low-mass S0s with lower rotation support compared to their high-mass counterparts. Qualitatively similar results are obtained when splitting galaxies based on the degree of ordered stellar rotation, such that galaxies with high spin magnitude have their spin aligned, and those with low spin magnitude in perpendicular direction to the filaments. In the context of conditional tidal torque theory, these findings suggest that galaxies’ spins retain memory of their larger scale environment. In agreement with measurements from hydrodynamical cosmological simulations, the measured signal at low redshift is weak, yet statistically significant. The dependence of the spin-filament orientation of galaxies on their stellar mass, morphology, and kinematics highlights the importance of sample selection to detect the signal.
Ultra-compact dwarfs beyond the centre of the Fornax galaxy cluster: hints of UCD formation in low-density environments
Authors: Saifollahi Teymoor , Janz Joachim , Peletier Reynier F , Cantiello Michele , Hilker Michael , Mieske Steffen , Valentijn Edwin A , Venhola Aku , Kleijn Gijs Verdoes 
Published: April 2021

ABSTRACT
Ultra-compact dwarf galaxies (UCDs) were serendipitously discovered by spectroscopic surveys in the Fornax cluster 20 yr ago. Nowadays, it is commonly accepted that many bright UCDs are the nuclei of galaxies that have been stripped. However, this conclusion might be driven by biased samples of UCDs in high-density environments, on which most searches are based. With the deep optical images of the Fornax Deep Survey, combined with public near-infrared data, we revisit the UCD population of the Fornax cluster and search for UCD candidates, for the first time, systematically out to the virial radius of the galaxy cluster. Our search is complete down to magnitude mg = 21 mag or M$_g\, \sim$ −10.5 mag at the distance of the Fornax cluster. The UCD candidates are identified and separated from foreground stars and background galaxies by their optical and near-infrared colours. This primarily utilizes the u−i/i−Ks diagram and a machine learning technique is employed to incorporate other colour combinations to reduce the number of contaminants. The newly identified candidates (44) in addition to the spectroscopically confirmed UCDs (61), increase the number of known Fornax UCD considerably (105). Almost all of the new UCD candidates are located outside the Fornax cluster core (360 kpc), where all of the known UCDs were found. The distribution of UCDs within the Fornax cluster shows that a population of UCDs may form in low-density environments. This most likely challenges the current models of UCD formation.
Three-body capture, ejection, and the demographics of bound objects in binary systems
Authors: Lehmann Benjamin V , Ross Olivia G , Webber Ava , Profumo Stefano 
Published: April 2021

ABSTRACT
We study the capture of light objects of arbitrary velocity by binary systems. Extending results for the capture of comets in the Solar system, we develop a simple geometric characterization of the capture cross-section, leading directly to the distribution of orbital parameters of captured objects. We use the same framework to study the lifetimes of these bound orbits prior to ejection, and find that a simplified version of the Öpik–Arnold approach readily yields a closed-form estimate for the ejection rate that agrees well with numerical experiments. Without any detailed-balance assumptions, our results make manifest the characteristics of close encounters leading to capture and ejection. As an application of our results, we demonstrate the estimation of the equilibrium population of captured dark matter particles in a binary system.
Neutral–neutral synthesis of organic molecules in cometary comae
Authors: Cordiner M A , Charnley S B 
Published: April 2021

ABSTRACT
Remote and in situ observations of cometary gases have revealed the presence of a wealth of complex organic molecules, including carbon chains, alcohols, imines, and the amino acid glycine. Such chemical complexity in cometary material implies that impacts by comets could have supplied reagents for prebiotic chemistry to young planetary surfaces. However, the assumption that some of the molecules observed in cometary comae at millimetre wavelengths originate from ices stored inside the nucleus has not yet been proven. In fact, the comae of moderately-active comets reach sufficient densities within a few thousand kilometres of the nucleus for an active (solar radiation-driven) photochemistry to ensue. Here, we present results from our latest chemical-hydrodynamic models incorporating an updated reaction network, and show that the commonly-observed HC3N (cyanoacetylene) and NH2CHO (formamide) molecules can be efficiently produced in cometary comae as a result of two-body, neutral–neutral, gas-phase reactions involving well-known coma species. In the presence of a near-nucleus distributed source of CN (similar to that observed by the Rosetta spacecraft at comet 67P), we find that sufficient HC3N and NH2CHO can be synthesized to match the abundances of these molecules observed previously in Oort cloud comets. The precise coma origins of these (and other) complex organic molecules can be verified through radio interferometric mapping observations, for example using the Atacama Large Millimeter/submillimeter Array.
Coendou vestitus(Rodentia: Erethizontidae)
Authors: Torres-Martínez María M , Aya-Cuero Carlos A , Noguera-Urbano Elkin A , Passos Fernando C , Ramírez-Chaves Héctor E 
Published: April 2021

AbstractCoendou vestitus Thomas, 1899, a rodent commonly known as the brown hairy dwarf porcupine, is one of the smallest Neotropical porcupines; its body is covered by three different types of hair and a short tail. C. vestitus is endemic to the western foothills of the Eastern Cordillera (Cordillera Oriental) of the Andes region of Colombia, where it has been confirmed through museum voucher specimens from only six localities characterized by lower montane moist forest vegetation. Globally, C. vestitus is listed as “Data Deficient” (DD) by the International Union for Conservation of Nature (IUCN); however, in Colombia it is categorized as “Vulnerable” (VU) by the Minister of Environment and Sustainable Development.
SIRIUS project. II. A new tree-direct hybrid code for smoothed particle hydrodynamics/N-body simulations of star clusters
Authors: Fujii Michiko S , Saitoh Takayuki R , Wang Long , Hirai Yutaka 
Published: April 2021

Abstract
Star clusters form via clustering star formation inside molecular clouds. In order to understand the dynamical evolution of star clusters in their early phase, in which they are still embedded in their surrounding gas, we need accurate integration of individual stellar orbits without gravitational softening in the systems including both gas and stars, as well as modeling of individual stars with a realistic mass function. We develop a new tree-direct hybrid smoothed particle hydrodynamics/N-body code, ASURA$+$BRIDGE, in which stars are integrated using a direct N-body scheme or PeTar, a particle–particle particle-tree scheme code, without gravitational softening. In ASURA$+$BRIDGE, stars are assumed to have masses randomly drawn from a given initial mass function. With this code, we perform star cluster formation simulations starting from molecular clouds without gravitational softening. We find that artificial dense cores in star cluster centers due to the softening disappear when we do not use softening. We further demonstrate that star clusters are built up via mergers of smaller clumps. The star clusters formed in our simulations include some dynamically formed binaries with minimum semi-major axes of a few au, and the binary fraction is higher for more massive stars.
Pain Intensity Predicts Pain Catastrophizing During the Postpartum Period: A Longitudinal Random Intercept Cross-Lagged Panel Study
Authors: Román Camila , Cumsille Patricio , Gómez-Pérez Lydia 
Published: April 2021

Abstract

Objective
Pain catastrophizing is an important psychological predictor of pain. Recent evidence suggests the relationship between catastrophizing and pain intensity could be bidirectional, but most studies have been conducted on chronic pain patients and using criticized statistical methods. The present study aimed to examine if the relationship between pain intensity and catastrophizing was bidirectional in the context of childbirth.

Methods
A total of 504 women without chronic pain were recruited on their 32–37 gestational week. They completed measures of catastrophizing and pain intensity on the first encounter and then again at 1, 3, and 6 months postpartum. The temporal relationship between the variables was assessed using a random intercept cross-lagged panel model.

Results
The hypothesis of reciprocal association did not receive support, as pain intensity predicted catastrophizing during the postpartum period, but catastrophizing did not show an effect over pain intensity at any moment.

Conclusions
Pain intensity predicting catastrophizing is consistent with previous literature, while the lack of effect of catastrophizing over pain intensity is an unexpected result, which may suggest that catastrophizing plays a different role in the postpartum period. These results highlight the importance of timely efforts for pain management during the postpartum period and contribute to the theoretical conceptualization of catastrophizing.
DIAGNOSTIC REFERENCE LEVELS OF CARDIAC COMPUTED TOMOGRAPHY ANGIOGRAPHY IN A SINGLE MEDICAL CENTER IN TAIWAN: A 3-Y ANALYSIS
Authors: Chen Li-Guo , Wu Ping-An , Tu Hsing-Yang , Sheu Ming-Huei , Huang Li-Chuan 
Published: April 2021

Abstract
This study aimed to establish the diagnostic reference levels (DRLs) for coronary computed tomography angiography (CCTA) and coronary arterial calcium score (CACS) owing to a large variability in patient radiation dose and the lack of dose recommendations in Taiwan. Volume computed tomography dose index (CTDIvol) and dose-length product (DLP) were obtained using CCTAs and the CACS of 445 patients over a 3-y period in a single medical center in Taiwan. CCTAs were performed using routine protocols and 256-detector CT scanners. Electrocardiogram gating was retrospective. The obtained data were analyzed using Prism 6 to determine the 25th, 50th (median) and 75th DRL percentiles for CTDIvol and DLP. These DRL results were compared with existing DRLs from seven countries. The DRLs for CCTA determined from this survey were similar to the existing data from other countries. Such DRLs could provide a useful tool for the optimization of radiation dose for CCTA in Taiwan.
Implementation of peer recovery coach services for opioid overdose patients in emergency departments in Indiana: findings from an informal learning collaborative of stakeholders
Authors: Staton Monte D , Watson Dennis P , Thorpe Dillon 
Published: April 2021

AbstractThe Recovery Coach and Peer Support Initiative (RCPSI) in Indiana focused on implementing peer recovery coaches (PRCs) to engage opioid overdose patients in emergency department (ED) settings and promote entry into recovery services. State workers and researchers organized an informal learning collaborative primarily through teleconference meetings with representatives of 11 health service vendors to support implementation. This study presents qualitative analysis of the teleconference meeting discussions that guided RCPSI implementation to display how the informal learning collaborative functioned to support implementation. This informal learning collaborative model can be applied in similar situations where there is limited guidance available for a practice being implemented by multidisciplinary teams. Authors conducted a thematic analysis of data from 32 stakeholder teleconference meetings held between February 2018 and April 2020. The analysis explored the function of these collaborative teleconferences for stakeholders. Major themes representing functions of the meetings for stakeholders include: social networking; executing the implementation plan; identifying and addressing barriers and facilitators; educating on peer recovery services and target population; and working through data collection. During the last 2 months of meetings, stakeholders discussed how the COVID-19 pandemic created multiple barriers but increased use of telehealth for recovery services. Teleconference meetings served as the main component of an informal learning collaborative for the RCPSI through which the vendor representatives could speak with each other and with organizers as they implemented the use of PRCs in EDs.
From One Pain to Many
Authors: Logan Deirdre E. , Donado Carolina , Kaczynski Karen , Lebel Alyssa , Schechter Neil 
Published: April 2021

Objectives:
The objective of this study was to compare children and adolescents with overlapping chronic pains (OCP) to those with single chronic pains (SCP) among youth presenting in specialized clinical settings, in an effort to identify potential risk factors for developing overlapping pains.

Methods:
A total of 1235 youth ages 8 to 18 seen in a tertiary care multidisciplinary pain clinic or a multidisciplinary headache clinic completed self-report measures of pain, disability, psychological functioning and clinical history and characteristics at the time of initial clinic visit. Information was captured in a chronic pain data repository and accessed for the current study.

Results:
Subsequent pain symptoms developed on average 11.9 months (SD=24.5 mo) after onset of the first pain symptom. Compared with patients with SCP, patients with OCP report more medical comorbidity, more developmental issues, and poorer current sleep and school functioning. They also scored significantly higher than patients with SCP on self-reported functional disability, pain catastrophizing, fear of pain, depression, anxiety, and psychological stress and lower quality of life (all Ps<0.001). In multivariate analysis, variables most strongly associated with presenting with OCP were age (odds ratio [OR]: 1.1, P<0.001), having a clinically significant high functional disability (OR: 1.4, P=0.3), and low quality of life (OR: 2.5, P<0.001).

Discussion:
Given their tendency toward more psychological and medical comorbidities, patients with OCP may require more intense and diverse treatment approaches. Some early life experiences may be a risk factor for development of OCP. Longitudinal studies are needed to fully evaluate the heightened risk for OCP associated with some of these factors.