bluuebunny/crossref_metadata_2025_split huggingface dataset:
IRON OPACITY BUMP CHANGES THE STABILITY AND STRUCTURE OF ACCRETION DISKS IN ACTIVE GALACTIC NUCLEI
Authors: Jiang(姜燕飞) Yan-Fei , Davis Shane W. , Stone James M. 
Published: August 2016

ABSTRACT
Accretion disks around supermassive black holes have regions where the Rosseland mean opacity can be larger than the electron scattering opacity due to the large number of bound–bound transitions in iron. We study the effects of this iron opacity “bump” on the thermal stability and vertical structure of radiation-pressure-dominated accretion disks, utilizing three-dimensional radiation magnetohydrodynamic (MHD) simulations in the local shearing box approximation. The simulations self-consistently calculate the heating due to MHD turbulence caused by magneto-rotational instability and radiative cooling by using the radiative transfer module based on a variable Eddington tensor in Athena. For a 5 × 108 solar mass black hole with ∼3% of the Eddington luminosity, a model including the iron opacity bump maintains its structure for more than 10 thermal times without showing significant signs of thermal runaway. In contrast, if only electron scattering and free–free opacity are included as in the standard thin disk model, the disk collapses on the thermal timescale. The difference is caused by a combination of (1) an anti-correlation between the total optical depth and the midplane pressure, and (2) enhanced vertical advective energy transport. These results suggest that the iron opacity bump may have a strong impact on the stability and structure of active galactic nucleus (AGN) accretion disks, and may contribute to a dependence of AGN properties on metallicity. Since this opacity is relevant primarily in UV emitting regions of the flow, it may help to explain discrepancies between observation and theory that are unique to AGNs.
SPACE-BASED MICROLENS PARALLAX OBSERVATION AS A WAY TO RESOLVE THE SEVERE DEGENERACY BETWEEN MICROLENS-PARALLAX AND LENS-ORBITAL EFFECTS
Authors: Han C. , Udalski A. , Lee C.-U. , Gould A. , Bozza V. , Szymański M. K. , Soszyński I. , Skowron J. , Mróz P. , Poleski R. , Pietrukowicz P. , Kozłowski S. , Ulaczyk K. , Wyrzykowski Ł. , Pawlak M. ,   (The OGLE Collaboration), Albrow M. D. , Chung S.-J. , Kim S.-L. , Cha S.-M. , Jung Y. K. , Kim D.-J. , Lee Y. , Park B.-G. , Ryu Y.-H. , Shin I.-G. , Yee J. C. ,   (The KMTNet Collaboration)
Published: August 2016

ABSTRACT
In this paper, we demonstrate the severity of the degeneracy between the microlens-parallax and lens-orbital effects by presenting the analysis of the gravitational binary-lens event OGLE-2015-BLG-0768. Despite the obvious deviation from the model based on the linear observer motion and the static binary, it is found that the residual can be almost equally well explained by either the parallactic motion of the Earth or the rotation of the binary-lens axis, resulting in the severe degeneracy between the two effects. We show that the degeneracy can be readily resolved with the additional data provided by space-based microlens parallax observations. By enabling us to distinguish between the two higher-order effects, space-based microlens parallax observations will not only make it possible to accurately determine the physical lens parameters but also to further constrain the orbital parameters of binary lenses.
ON THE THERMAL LINE EMISSION FROM THE OUTFLOWS IN ULTRALUMINOUS X-RAY SOURCES
Authors: Xu Ya-Di , Cao Xinwu 
Published: August 2016

ABSTRACT
The atomic features in the X-ray spectra of ultraluminous X-ray sources (ULXs) may be associated with the outflow, which may provide a way to explore the physics of the ULXs. We construct a conical outflow model and calculate the thermal X-ray Fe emission lines from the outflows. Our results show that thermal line luminosity decreases with increasing outflow velocity and/or opening angle of the outflow for a fixed kinetic power of the outflows. Assuming the kinetic power of the outflows to be comparable with the accretion power in the ULXs, we find that the equivalent width can be several eV for the thermal X-ray Fe emission line from the outflows in the ULXs with stellar-mass black holes. The thermal line luminosity is proportional to 1/M
bh (M
bh is the black hole mass of the ULX). The equivalent width decreases with the black hole mass, which implies that the Fe line emission from the outflows can hardly be detected if the ULXs contain intermediate-mass black holes. Our results suggest that the thermal X-ray Fe line emission should be preferentially be detected in the ULXs with high kinetic power slowly moving outflows from the accretion disks surrounding stellar-mass black holes/neutron stars. The recently observed X-ray atomic features of the outflows in a ULX may imply that it contains a stellar-mass black hole.
COMPARING EXTENDED SYSTEM INTERACTIONS WITH MOTIONS IN SOFTENED POTENTIALS
Authors: Barnes Eric I. 
Published: August 2016

ABSTRACT
Using an N-body evolution code that does not rely on softened potentials, I have created a suite of unbound interacting cluster pair simulations. The motions of the centers of mass of the clusters have been tracked and compared to the trajectories of point masses interacting via one of four different softened potential prescriptions. I find that the relationship between the impact parameter of the cluster interaction and the point-mass softening length that best approximates each cluster’s center-of-mass motion depends on the adopted prescription. In general, the range of allowed softening lengths grows roughly linearly with the impact parameter, but zero softening is acceptable in the majority of situations. In an N-body simulation that adopts a fixed softening length, such relationships lead to the possibility of two-body effects, like dynamical friction, being either larger or smaller than the corresponding cluster situation. Further consideration of more specific N-body situations leads to estimating that a very small fraction of point-mass encounters experience two-body effects significantly different from those of equivalent clusters.
PITCH-ANGLE SCATTERING OF ENERGETIC CHARGED PARTICLES IN NEARLY CONSTANT MAGNITUDE MAGNETIC TURBULENCE
Authors: Sun P. , Jokipii J. R. , Giacalone J. 
Published: August 2016

ABSTRACT
We use a method developed by Roberts that optimizes the phase angles of an ensemble of plane waves with amplitudes determined from a Kolmogorov-like power spectrum, to construct magnetic field vector fluctuations having nearly constant magnitude and large variances in its components. This is a representation of the turbulent magnetic field consistent with that observed in the solar wind. Charged-particle pitch-angle diffusion coefficients are determined by integrating the equations of motion for a large number of charged particles moving under the influence of forces from our predefined magnetic field. We tested different cases by varying the kinetic energy of the particles (E
p) and the turbulent magnetic field variance (

). For each combination of E
p and

, we tested three different models: (1) the so-called “slab” model, where the turbulent magnetic field depends on only one spatial coordinate and has significant fluctuations in its magnitude (

); (2) the slab model optimized with nearly constant magnitude b; and (3) the slab model turbulent magnetic field with nearly constant magnitude plus a “variance-conserving” adjustment. In the last case, this model attempts to conserve the variance of the turbulent components (

), which is found to decrease during the optimization with nearly constant magnitude. We found that there is little or no effect on the pitch-angle diffusion coefficient

between models 1 and 2. However, the result from model 3 is significantly different. We also introduce a new method to accurately determine the pitch-angle diffusion coefficients as a function of μ.
CONSTRAINTS ON THE DISTANCE MODULI, HELIUM AND METAL ABUNDANCES, AND AGES OF GLOBULAR CLUSTERS FROM THEIR RR LYRAE AND NON-VARIABLE HORIZONTAL-BRANCH STARS. I. M3, M15, AND M92
Authors: VandenBerg Don A. , Denissenkov P. A. , Catelan Márcio 
Published: August 2016

ABSTRACT
Up-to-date isochrones, zero-age horizontal-branch (ZAHB) loci, and evolutionary tracks for core He-burning stars are applied to the color–magnitude diagrams of M3, M15, and M92, focusing in particular on their RR Lyrae populations. Periods for the ab- and c-type variables are calculated using the latest theoretical calibrations of

and

as a function of luminosity, mass, effective temperature (

), and metallicity. Our models are generally able to reproduce the measured periods to well within the uncertainties implied by the stellar properties on which pulsation periods depend, as well as the mean periods and cluster-to-cluster differences in

and

, on the assumption of well-supported values of

,

, and [Fe/H]. While many of RR Lyrae in M3 lie close to the same ZAHB that fits the faintest horizontal-branch (HB) stars at bluer or redder colors, the M92 variables are all significantly evolved stars from ZAHB locations on the blue side of the instability strip. M15 appears to contain a similar population of HB stars as M92, along with additional helium-enhanced populations not present in the latter which comprise most of its RR Lyrae stars. The large number of variables in M15 and the similarity of the observed values of

and

in M15 and M92 can be explained by HB models that allow for variations in Y. Similar ages (∼12.5 Gyr) are found for all three clusters, making them significantly younger than the field halo subgiant HD 140283. Our analysis suggests a preference for stellar models that take diffusive processes into account.
BREAKING THE CURVE WITH CANDELS: A BAYESIAN APPROACH TO REVEAL THE NON-UNIVERSALITY OF THE DUST-ATTENUATION LAW AT HIGH REDSHIFT
Authors: Salmon Brett , Papovich Casey , Long James , Willner S. P. , Finkelstein Steven L. , Ferguson Henry C. , Dickinson Mark , Duncan Kenneth , Faber S. M. , Hathi Nimish , Koekemoer Anton , Kurczynski Peter , Newman Jeffery , Pacifici Camilla , Pérez-González Pablo G. , Pforr Janine 
Published: August 2016

ABSTRACT
Dust attenuation affects nearly all observational aspects of galaxy evolution, yet very little is known about the form of the dust-attenuation law in the distant universe. Here, we model the spectral energy distributions of galaxies at z ∼ 1.5–3 from CANDELS with rest-frame UV to near-IR imaging under different assumptions about the dust law, and compare the amount of inferred attenuated light with the observed infrared (IR) luminosities. Some individual galaxies show strong Bayesian evidence in preference of one dust law over another, and this preference agrees with their observed location on the plane of infrared excess (IRX,

/

) and UV slope (β). We generalize the shape of the dust law with an empirical model,

where k

λ
is the dust law of Calzetti et al., and show that there exists a correlation between the color excess

and tilt δ with

. Galaxies with high color excess have a shallower, starburst-like law, and those with low color excess have a steeper, SMC-like law. Surprisingly, the galaxies in our sample show no correlation between the shape of the dust law and stellar mass, star formation rate, or β. The change in the dust law with color excess is consistent with a model where attenuation is caused by scattering, a mixed star–dust geometry, and/or trends with stellar population age, metallicity, and dust grain size. This rest-frame UV-to-near-IR method shows potential to constrain the dust law at even higher redshifts (

).
MASS TRANSPORT AND TURBULENCE IN GRAVITATIONALLY UNSTABLE DISK GALAXIES. II. THE EFFECTS OF STAR FORMATION FEEDBACK
Authors: Goldbaum Nathan J. , Krumholz Mark R. , Forbes John C. 
Published: August 2016

ABSTRACT
Self-gravity and stellar feedback are capable of driving turbulence and transporting mass and angular momentum in disk galaxies, but the balance between them is not well understood. In the previous paper in this series, we showed that gravity alone can drive turbulence in galactic disks, regulate their Toomre Q parameters to ∼1, and transport mass inwards at a rate sufficient to fuel star formation in the centers of present-day galaxies. In this paper we extend our models to include the effects of star formation feedback. We show that feedback suppresses galaxies’ star formation rates by a factor of ∼5 and leads to the formation of a multi-phase atomic and molecular interstellar medium. Both the star formation rate and the phase balance produced in our simulations agree well with observations of nearby spirals. After our galaxies reach steady state, we find that the inclusion of feedback actually lowers the gas velocity dispersion slightly compared to the case of pure self-gravity, and also slightly reduces the rate of inward mass transport. Nevertheless, we find that, even with feedback included, our galactic disks self-regulate to Q ∼ 1, and transport mass inwards at a rate sufficient to supply a substantial fraction of the inner disk star formation. We argue that gravitational instability is therefore likely to be the dominant source of turbulence and transport in galactic disks, and that it is responsible for fueling star formation in the inner parts of galactic disks over cosmological times.
THE X-RAY THROUGH OPTICAL FLUXES AND LINE STRENGTHS OF TIDAL DISRUPTION EVENTS
Authors: Roth Nathaniel , Kasen Daniel , Guillochon James , Ramirez-Ruiz Enrico 
Published: August 2016

ABSTRACT
We study the emission from tidal disruption events (TDEs) produced as radiation from black hole accretion propagates through an extended, optically thick envelope formed from stellar debris. We analytically describe key physics controlling spectrum formation, and present detailed radiative transfer calculations that model the spectral energy distribution and optical line strengths of TDEs near peak brightness. The steady-state transfer is coupled to a solver for the excitation and ionization states of hydrogen, helium, and oxygen (as a representative metal), without assuming local thermodynamic equilibrium. Our calculations show how an extended envelope can reprocess a fraction of soft X-rays and produce the observed optical fluxes of the order of 1043 erg s−1, with an optical/UV continuum that is not described by a single blackbody. Variations in the mass or size of the envelope may help explain how the optical flux changes over time with roughly constant color. For high enough accretion luminosities, X-rays can escape to be observed simultaneously with the optical flux. Due to optical depth effects, hydrogen Balmer line emission is often strongly suppressed relative to helium line emission (with He ii-to-H line ratios of at least 5:1 in some cases) even in the disruption of a solar-composition star. We discuss the implications of our results to understanding the type of stars destroyed in TDEs and the physical processes responsible for producing the observed flares.
AN EMPIRICAL DETERMINATION OF THE INTERGALACTIC BACKGROUND LIGHT FROM UV TO FIR WAVELENGTHS USING FIR DEEP GALAXY SURVEYS AND THE GAMMA-RAY OPACITY OF THE UNIVERSE
Authors: Stecker Floyd W. , Scully Sean T. , Malkan Matthew A. 
Published: August 2016

ABSTRACT
We have previously calculated the intergalactic background light (IBL) as a function of redshift from the Lyman limit in the far-ultraviolet to a wavelength of 5 μm in the near-infrared range, based purely on data from deep galaxy surveys. Here, we use similar methods to determine the mid- and far-infrared IBL from 5 to 850 μm. Our approach enables us to constrain the range of photon densities by determining the uncertainties in observationally determined luminosity densities and spectral gradients. By also including the effect of the 2.7 K cosmic background photons, we determine upper and lower limits on the opacity of the universe to γ-rays up to PeV energies within a 68% confidence band. Our direct results on the IBL are consistent with those from complimentary γ-ray analyses using observations from the Fermi γ-ray space telescope and the H.E.S.S. air Čerenkov telescope. Thus, we find no evidence of previously suggested processes for the modification of γ-ray spectra other than that of absorption by pair production alone.
CHROMOSPHERIC AND CORONAL WAVE GENERATION IN A MAGNETIC FLUX SHEATH
Authors: Kato Yoshiaki , Steiner Oskar , Hansteen Viggo , Gudiksen Boris , Wedemeyer Sven , Carlsson Mats 
Published: August 2016

ABSTRACT
Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab “pump” the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.
Suites et séquelles de l’intrusion maternelle
Authors: de Mijolla-Mellor Sophie 
Published: August 2016

Derrière l’enfant réel gît une exigence démesurée : revivre avec un enfant issu de soi la relation idéale que l’on n’a pas connue – mais dont paradoxalement on garde la nostalgie – avec une mère elle-même idéale. Aussi le conflit ne manquera de surgir lorsque l’évolution de l’enfant le confrontera au fait qu’il n’est en réalité plus le même que le personnage auquel il était assigné à vie. L’incapacité à supporter la réalité et les limites de l’enfant conduit en retour à considérer la maternité comme une expérience qui requiert une réélaboration pulsionnelle. Celle-ci ne se limite pas à un refoulement des pulsions sexuelles et agressives mais implique leur sublimation.
Retinoblastoma Control With Primary Intra-arterial Chemotherapy: Outcomes Before and During the Intravitreal Chemotherapy Era
Authors: Shields Carol L. , Alset Adel E. , Say Emil Anthony T. , Caywood Emi , Jabbour Pascal , Shields Jerry A. 
Published: August 2016

Purpose:
To compare outcomes of intra-arterial chemotherapy for retinoblastoma as primary therapy before (Era I) and during (Era II) the intravitreal chemotherapy era.

Methods:
In this retrospective interventional case series at a tertiary referral center, 66 eyes of 66 patients with untreated unilateral retinoblastoma were used. intraarterial chemotherapy into the ophthalmic artery under fluoroscopic guidance was performed using melphalan in every case, with additional topotecan as necessary. Intravitreal chemotherapy using melphalan and/or topotecan was employed as needed for active vitreous seeding. Globe salvage was measured based on the International Classification of Retinoblastoma (ICRB) during two eras.

Results:

The two eras encompassed 2008 to 2012 (intraarterial chemotherapy alone, Era I) and 2012 to 2015 (intraarterial chemotherapy plus intravitreal chemotherapy, Era II). Over this period, there were 66 patients with unilateral untreated retinoblastoma treated with primary intra-arterial chemotherapy. A comparison of features (Era I vs Era II) revealed no significant difference in mean patient age (24 vs 24 months), ICRB groups, mean largest tumor diameter (19 vs 17 mm), mean largest tumor thickness (10 vs 10 mm), vitreous seed presence (56% vs 59%), subretinal seed presence (67% vs 62%), retinal detachment (70% vs 66%), or vitreous hemorrhage (0% vs 5%). There was no significant difference in mean number of intra-arterial chemotherapy cycles (3 vs 3.1) or intraarterial chemotherapy dosages. Following therapy, there was a significant difference (Era I vs Era II) in the need for enucleation overall (44% vs 15%,
P
= .012), especially for group E eyes (75% vs 27%,
P
= .039). Four of the eyes that initiated therapy in Era I later required intravitreal chemotherapy during Era II. The enucleation rate was 0% for groups B and C in both eras and non-significant for group D (23% vs 13%). There were no patients with stroke, seizure, limb ischemia, extraocular tumor extension, secondary leukemia, metastasis, or death.

Conclusions:
The current era of retinoblastoma management using intra-arterial chemotherapy plus additional intravitreal chemotherapy (as needed for vitreous seeding) has improved globe salvage in eyes with advanced retinoblastoma.

[
J Pediatr Ophthalmol Strabismus
. 2016;53(5):275–284.]
Internal Medicine Residents' Retention of Knowledge and Skills in Bedside Ultrasound
Authors: Town James A. , Bergl Paul A. , Narang Akhil , McConville John F. 
Published: August 2016

ABSTRACT

Background
The long-term retention of knowledge and skills in bedside ultrasound by internal medicine residents after ultrasound training is not well understood.

Objective
We sought to determine whether knowledge and skills acquired from focused training in bedside ultrasound are retained over time, and whether retention is related to independent practice.

Methods
We conducted a prospective observational trial of 101 internal medicine residents at an academic medical center who participated in a bedside ultrasound workshop followed by 12 months of independent practice. Performance was measured on image-based knowledge and skills assessment using direct observation, both before the workshop and 12 months later. Individual usage data were obtained along with a survey on attitudes toward bedside ultrasound.

Results
Participants' mean knowledge assessment score increased from a baseline of 63.7% to 84.5% immediately after training (P &lt; .001). At 12 months, mean knowledge score fell to 73.0%, significantly different from both prior assessments (P &lt; .001). Despite knowledge decline, the mean skills assessment score improved from a baseline of 30.5% to 50.4% at 12 months (P &lt; .001). Residents reporting more ultrasound use (&gt; 25 examinations) had higher scores in baseline knowledge and skills assessments than those with lower usage (&lt; 25 examinations). Change in knowledge and image acquisition skills between assessments was equal in both subgroups.

Conclusions
Residents' knowledge of ultrasound improved after brief training but decayed over time, whereas skills showed marginal improvement over the study, with minimal support. Growth and retention of ultrasound abilities were not impacted by usage rates.