bluuebunny/crossref_metadata_2025_split huggingface dataset:
صعوبات دراسة مادة فلسفة التاريخ وحلولها المقترحة من وجهة نظر طالبات قسم التاريخ بكلية التربية للبنات بجامعة بغداد
Authors: الاستاذ المساعد الدكتور احمد هاشم محمد العميري  
Published: April 2020

يهدف البحث إلى معرفة صعوبات دراسة مادة فلسفة التاريخ وحلولها المقترحة من وجهة نظر طالبات قسم التأريخ بكلية التربية للبنات بجامعة بغداد، تكون مجتمع البحث من جميع طالبات الدراسات الاولية بقسم التأريخ في كلية التربية للبنات بجامعة بغداد والبالغ عددهن ( 352 ) طالبة . ولتحقيق هدف البحث أختار الباحث الأستبانة أداة لدراسته ؛ اذ تم استخراج صدقها من خلال عرضها على مجموعة من المتخصصين في العلوم التربوية والنفسية والتاريخ ؛ وثباتها بالاعتماد على طريقة ( إعادة تطبيق الأداة) ؛ ولحساب معامل ثباتها اعتمد الباحث على معامل ارتباط بيرسون( pearson ) فقد تراوح ثبات فقرات مجالاتها الرئيسة بين ( 0.79 – 0.73 ) ، في حين بلغ المتوسط الحسابي العام لثبات الأداة ( 0.78 ) . ولبيان نتائج البحث اعتمدت الوسائل الإحصائية (معامل ارتباط بيرسون ومعادلة فيشر والوزن المئوي) ، اذ أظهرت النتائج وجود عدد من الصعوبات الحقيقة المتحققة الخاصة بدراسة مادة فلسفة التاريخ البالغ عددها ( 17 ) فقرة ؛ كما دلت البيانات عن وجود صعوبات غير حقيقية تم تشخيصها من وجهة نظرهن وعدنها غير متحققة في ضوء المعيار المعتمد (2.00) والبالغ عددها ( 8 ) فقرات من مجموع فقرات الأداة البالغة عدد فقراتها (25) فقرة . وفي ضوء ذلك وضع الباحث عدة استنتاجات وتوصيات ومقترحات .
Understanding the Origin of the Magnetic Field Morphology in the Wide-binary Protostellar System BHR 71
Authors: Hull Charles L. H. , Gouellec Valentin J. M. Le , Girart Josep M. , Tobin John J. , Bourke Tyler L. 
Published: April 2020

Abstract
We present 1.3 mm Atacama Large Millimeter/submillimeter Array observations of polarized dust emission toward the wide-binary protostellar system BHR 71 IRS1 and IRS2. IRS1 features what appears to be a natal, hourglass-shaped magnetic field. In contrast, IRS2 exhibits a magnetic field that has been affected by its bipolar outflow. Toward IRS2, the polarization is confined mainly to the outflow cavity walls. Along the northern edge of the redshifted outflow cavity of IRS2, the polarized emission is sandwiched between the outflow and a filament of cold, dense gas traced by N2D+, toward which no dust polarization is detected. This suggests that the origin of the enhanced polarization in IRS2 is the irradiation of the outflow cavity walls, which enables the alignment of dust grains with respect to the magnetic field—but only to a depth of ∼300 au, beyond which the dust is cold and unpolarized. However, in order to align grains deep enough in the cavity walls, and to produce the high polarization fraction seen in IRS2, the aligning photons are likely to be in the mid- to far-infrared range, which suggests a degree of grain growth beyond what is typically expected in very young, Class 0 sources. Finally, toward IRS1 we see a narrow, linear feature with a high (10%–20%) polarization fraction and a well-ordered magnetic field that is not associated with the bipolar outflow cavity. We speculate that this feature may be a magnetized accretion streamer; however, this has yet to be confirmed by kinematic observations of dense-gas tracers.
TXS 2116−077: A Gamma-Ray Emitting Relativistic Jet Hosted in a Galaxy Merger
Authors: Paliya Vaidehi S. , Pérez Enrique , García-Benito Rubén , Ajello Marco , Prada Francisco , Alberdi Antxon , Suh Hyewon , Chandra C. H. Ishwara , Domínguez Alberto , Marchesi Stefano , Matteo Tiziana Di , Hartmann Dieter , Chiaberge Marco 
Published: April 2020

Abstract
What triggers collimated relativistic outflows or jets from the centers of galaxies remains a fundamental question in astrophysics. The merging of two galaxies has been proposed to realize the conditions to successfully launch and drive such jets into the intergalactic medium. However, evidence for the operation of this mechanism is scarce. Here we report the first unambiguous detection of an ongoing merger of a narrow-line Seyfert 1 galaxy, TXS 2116−077, hosting a closely aligned, γ-ray emitting relativistic jet with a Seyfert 2 galaxy at a separation of ∼12 kpc, using the observations taken with the 8.2 m Subaru Telescope. Our subsequent follow-up observations with the 10.4 m Gran Telescopio Canarias, 4.2 m William Herschel Telescope, and Chandra X-ray observatory have provided what is likely to be the first glimpse of the merging environment hosting a closely aligned relativistic jet. Our finding that the jet is considerably younger than the merger demonstrates that jet activity can be triggered by galaxy mergers and that γ-ray detected narrow-line Seyfert 1 galaxies represent the beginning phase of that activity. These results also highlight the crucial role of mergers in shaping the fate of galaxies in their cosmological evolution and are consistent with recent studies focused on the host galaxy imaging of this enigmatic class of active galactic nuclei.
Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-forming Galaxies
Authors: Sun (孙嘉懿) Jiayi , Leroy Adam K. , Ostriker Eve C. , Hughes Annie , Rosolowsky Erik , Schruba Andreas , Schinnerer Eva , Blanc Guillermo A. , Faesi Christopher , Kruijssen J. M. Diederik , Meidt Sharon , Utomo Dyas , Bigiel Frank , Bolatto Alberto D. , Chevance Mélanie , Chiang (江宜達) I-Da , Dale Daniel , Emsellem Eric , Glover Simon C. O. , Grasha Kathryn , Henshaw Jonathan , Herrera Cinthya N. , Jimenez-Donaire Maria Jesus , Lee Janice C. , Pety Jérôme , Querejeta Miguel , Saito Toshiki , Sandstrom Karin , Usero Antonio 
Published: April 2020

Abstract
We compare the observed turbulent pressure in molecular gas, P
turb, to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, P
DE. To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multiwavelength data that trace the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that P
turb correlates with—but almost always exceeds—the estimated P
DE on kiloparsec scales. This indicates that the molecular gas is overpressurized relative to the large-scale environment. We show that this overpressurization can be explained by the clumpy nature of molecular gas; a revised estimate of P
DE on cloud scales, which accounts for molecular gas self-gravity, external gravity, and ambient pressure, agrees well with the observed P
turb in galaxy disks. We also find that molecular gas with cloud-scale

in our sample is more likely to be self-gravitating, whereas gas at lower pressure it appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between P
turb and the observed SFR surface density,

, is compatible with stellar feedback-driven momentum injection in most cases, while a subset of the regions may show evidence of turbulence driven by additional sources. The correlation between

and kpc-scale P
DE in galaxy disks is consistent with the expectation from self-regulated star formation models. Finally, we confirm the empirical correlation between molecular-to-atomic gas ratio and kpc-scale P
DE reported in previous works.
Oversized Gas Clumps in an Extremely Metal-poor Molecular Cloud Revealed by ALMA’s Parsec-scale Maps
Authors: Shi Yong , Wang Junzhi , Zhang Zhi-Yu , Zhang Qizhou , Gao Yu , Zhou Luwenjia , Gu Qiusheng , Qiu Keping , Xia Xiao-Yang , Hao Cai-Na , Chen Yanmei 
Published: April 2020

Abstract
Metals are thought to have profound effects on the internal structures of the molecular clouds in which stars are born. The absence of metals is expected to prevent gas from efficient cooling and fragmentation in theory. However, this effect has not yet been observed in low-metallicity environments, such as in the early universe and local dwarf galaxies, because of the lack of high-spatial-resolution maps of gas. We carried out Atacama Large Millimeter/submillimeter Array observations of the carbon monoxide (CO) J = 2–1 emission line at 1.4 parsec resolutions of a molecular cloud in DDO 70 at 7% solar metallicity, the most metal-poor galaxy currently known with a CO detection. In total, five clumps have been identified and they are found to more or less follow Larson’s law. Since the CO emission exists in regions with visual extinction A
V around 1.0, we converted this A
V to the gas-mass surface density using a gas-to-dust ratio of 4594 ± 2848 for DDO 70. We found that the CO clumps in DDO 70 exhibit significantly larger (on average four times) sizes than those at the same gas-mass surface densities in the massive star formation regions of the Milky Way. The existence of such large clumps appears to be consistent with theoretical expectations that gas fragmentation in low-metallicity clouds is suppressed. While our observation is only for one cloud in the galaxy, if it is representative, the above result implies suppressed gas fragmentation during the cloud collapse and star formation in the early universe.
A Small-scale Investigation of Molecular Emission toward the Tip of the Western Lobe of W50/SS 433
Authors: Liu Qian-Cheng , Chen Yang , Zhou Ping , Zhang Xiao , Jiang Bing 
Published: April 2020

Abstract
We perform a molecular (CO and CN) line observation using the IRAM 30 m telescope toward two small regions near the western edge of supernova remnant (SNR) W50/SS 433. CO observation reveals spatial correspondence of two molecular clumps at the local-standard-of-rest (LSR) velocity around +53

, with multiwavelength local features of the W50/SS 433 system. One of the two clumps appears to be embedded in a void of diffuse radio and X-ray emission. Toward the two clumps, asymmetric broad-line profiles of the 12CO lines are obtained, which provide kinematic evidence of the association between the clumps and the jet-related gas. The 12CO J = 2–1/J = 1–0 line ratios (≳0.9) and the kinetic temperatures (∼30 K) of the clumps are distinctively higher than all those of the clumps at other LSR velocities along the same line of sight, which may be physical signatures of the association. We show that the clump coincident with the void can survive the thermal heating if it is surrounded by hot gas, with an evaporation timescale much larger than the age of SNR W50. We also show that the thermal equilibrium in the high-temperature clumps can be maintained by the heating of the penetrating environmental cosmic rays. CN (J = 3/1–1/2) line emission is detected in the two clumps, and the CN abundances derived are much higher than that in the interstellar molecular clouds (MCs) and that in the SNR-interacting MCs.
SN 2017cfd: A Normal Type Ia Supernova Discovered Very Young
Authors: Han Xuhui , Zheng WeiKang , Stahl Benjamin E. , Burke Jamison , Vinko Jozsef , Jaeger Thomas de , Arcavi Iair , Brink Thomas G. , Cseh Borbala , Hiramatsu Daichi , Hosseinzadeh Griffin , Howell D. Andrew , Ignacz Bernadett , Konyves-Toth Reka , Krezinger Mate , McCully Curtis , Ordasi Andras , Pinter Dora , Sarneczky Krisztian , Szakats Robert , Tang Kevin , Vida Krisztian , Wang Jing , Wei Jianyan , Wheeler J. Craig , Xin Liping , Filippenko Alexei V. 
Published: April 2020

Abstract
The Type Ia supernova (SN Ia) 2017cfd in IC 0511 (redshift

) was discovered by the Lick Observatory Supernova Search 1.6 ± 0.7 day after the fitted first-light time (15.2 days before B-band maximum brightness). Photometric and spectroscopic follow-up observations show that SN 2017cfd is a typical, normal SN Ia with a peak luminosity

mag, Δm
15(B) = 1.16 mag, and reached a B-band maximum ∼16.8 days after the first light. We estimate there to be moderately strong host-galaxy extinction (A

V
= 0.39 ± 0.03 mag) based on MLCS2k2 fitting. The spectrum reveals a Si ii
λ6355 velocity of ∼11,200 km s−1 at peak brightness. SN 2017cfd was discovered very young, with multiband data taken starting 2 days after the first light, making it a valuable complement to the currently small sample (fewer than a dozen) of SNe Ia with color data at such early times. We find that its intrinsic early-time

color evolution belongs to the “blue” population rather than to the distinct “red” population. Using the photometry, we constrain the companion-star radius to be ≲2.5 R
☉ with the Kasen model, thus ruling out a red-giant companion.
Spectral Signatures of Quasar Ages at z ≈ 3
Authors: Zheng Wei 
Published: April 2020

Abstract
Insight into quasar ages may be obtained from the proximity effect, but so far only in a limited number of bright quasars. Based on ∼2600 Sloan Digital Sky Survey quasar spectra at 2.5 ≤ z ≤ 3.5, a search for spectral voids between Lyα forest lines finds proximity zones over a wide range of radial distances. The majority of zone sizes are less than 5 Mpc, with their numbers decreasing exponentially toward larger distances. After a normalization by luminosities, the zone sizes are distributed with an e-folding scale of 0.64 as compared with the anticipated values. A group of quasars are selected for their large proximity zones of ≳10 Mpc. Their composite spectrum displays strong narrow cores and large equivalent widths in Lyα and other major UV emission lines. If the proximity zones along lines of sight are indicative of quasar ages, these features may be the signatures of old quasars. Another group of quasars are selected as they show no proximity zone and exhibit intrinsic absorption lines at z

ab
> z

em
. They are likely young quasars and exhibit weaker narrow emission-line components. The significant difference of spectral features between the two groups may reflect an evolution pattern over quasars’ lifetimes.
Effects of Scattering, Temperature Gradients, and Settling on the Derived Dust Properties of Observed Protoplanetary Disks
Authors: Sierra Anibal , Lizano Susana 
Published: April 2020

Abstract
It is known that the millimeter dust thermal emission of protoplanetary disks is affected by scattering, such that for optically thick disks, the emission decreases with respect to the pure absorption case and the spectral indices can reach values below 2. The latter can also be obtained with temperature gradients. Using simple analytical models of radiative transfer in thin slabs, we quantify the effect of scattering, vertical temperature gradients, and dust settling on the emission and spectral indices of geometrically thin face-on accretion disks around young stars. We find that, in vertically isothermal disks with large albedo (

), the emergent intensity can increase at optical depths between 10−2 and 10−1. We show that dust settling has important effects on the spectral indices in the optically thick regime, since the disk emission mainly traces small dust grains in the upper layers of the disk. The λ = 870 μm emission of these small grains can hide large grains at the disk midplane when the dust surface density is larger than ∼3.21 g cm−2. Finally, because of the change of the shape of the spectral energy distribution, optically thick disks at 1.3 mm and grains with sizes between

mm have a 7 mm flux ∼60% higher than the extrapolation from higher millimeter frequencies, assumed when scattering is neglected. This effect could provide an explanation for the excess emission at

reported in several disks.
Fast Radio Burst Counterparts and Their Implications for the Central Engine
Authors: Wang Jie-Shuang , Lai Dong 
Published: April 2020

Abstract
While the radiation mechanism of fast radio bursts (FRBs) is unknown, coherent curvature radiation and synchrotron maser are promising candidates. We find that both radiation mechanisms work for a neutron star (NS) central engine with

G, while for a synchrotron maser, the central engine can also be an accreting black hole (BH) with

G and a white dwarf (WD) with

G. We study the electromagnetic counterparts associated with such central engines, i.e., nebulae for repeating FRBs and afterglows for nonrepeating FRBs. In general, the energy spectrum and flux density of the counterpart depend strongly on its size and total injected energy. We apply the calculation to the nebula of FRB 121102 and find that the persistent radio counterpart requires the average energy injection rate into the nebula to be between

and

, and the minimum injected energy to be

in around 7 yr. Consequently, we find that for FRB 121102 and its nebula: (1) WD and accretion BH central engines are disfavored; (2) a rotation-powered NS central engine works when

with initial period

ms, but the radio emission must be more efficient than that in typical giant pulses of radio pulsars; and (3) a magnetic-powered NS central engine works when its internal magnetic field

G. We also find that the radio-emitting electrons in the nebula could produce a significant rotation measure (RM), but cannot account for the entire observed RM of FRB 121102.
A Fast O(N2) Fragmentation Algorithm
Authors: Rafikov Roman R. , Silsbee Kedron , Booth Richard A. 
Published: April 2020

Abstract
Collisional fragmentation is a ubiquitous phenomenon arising in a variety of astrophysical systems, from asteroid belts to debris and protoplanetary disks. Numerical studies of fragmentation typically rely on discretizing the size distribution of colliding objects into a large number N of bins in mass space, usually logarithmically spaced. A standard approach for redistributing the debris produced in collisions into the corresponding mass bins results in

calculation, which leads to significant computational overhead when N is large. Here, we formulate a more efficient explicit

fragmentation algorithm, which works when the size spectrum of fragments produced in an individual collision has a self-similar shape with only a single characteristic mass scale (which can have arbitrary dependence on the energy and masses of colliding objects). Fragment size spectra used in existing fragmentation codes typically possess this property. We also show that our

approach can be easily extended to work with non-self-similar fragment size distributions, for which we provide a worked example. This algorithm offers a substantial speedup of fragmentation calculations for large N ≳ 102, even over the implicit methods, making it an attractive tool for studying collisionally evolving systems.
Observing the Effects of Galaxy Interactions on the Circumgalactic Medium
Authors: Zhang 张 Huanian 华 年 , Fang 方 Taotao 陶 陶 , Zaritsky Dennis , Behroozi Peter , Werk Jessica , Yang 杨 Xiaohu 小 虎 
Published: April 2020

Abstract
We continue our empirical study of the emission line flux originating in the cool (T ∼ 104 K) gas that populates the halos of galaxies and their environments. Specifically, we present results obtained for a sample of galaxy pairs with a range of projected separations,

, and mass ratios <1:5, intersected by 5443 Sloan Digital Sky Survey lines of sight at projected radii of 10–50 kpc from either or both of the two galaxies. We find significant enhancement in Hα emission and a moderate enhancement in [N ii]6583 emission for low-mass pairs (mean stellar mass per galaxy,

) relative to the results from a control sample. This enhanced Hα emission comes almost entirely from sight lines located between the galaxies, consistent with a short-term, interaction-driven origin for the enhancement. We find no enhancement in Hα emission, but significant enhancement in [N ii]6583 emission for high-mass (

) pairs. Furthermore, we find a dependence of the emission line properties on the galaxy pair mass ratio such that those with a mass ratio below 1:2.5 have enhanced [N ii]6583 and those with a mass ratio between 1:2.5 and 1:5 do not. In all cases, departures from the control sample are only detected for close pairs (S

p
< 100 kpc). Attributing an elevated [N ii]6583/Hα ratio to shocks, we infer that shocks play a role in determining the circumgalactic medium properties for close pairs that are among the more massive and have mass ratios closer to 1:1.
Addictions et problèmes bucco-dentaires
Authors: Tinta Struillou Haoua , Lemaire Christine , Sculo Chaiban Tiphaine , Guillou Landreat Morgane 
Published: April 2020

L’état bucco-dentaire des patients rencontrés en service d’addictologie est souvent préoccupant. Soigner les dents efficacement et sur la durée est difficile. Quelles en sont les causes ? Est-ce une conséquence de la prise de toxique, d’une désocialisation ou de l’état psychique antérieur du patient ? Après quelques recherches sur ces thèmes en évoquant un possible rôle de la précarité, un questionnaire est mené sur trois groupes. Des patients, des soignants d’un service d’addictologie et des chirurgiens dentistes sont interrogés pour entendre les dires et ressentis face aux problèmes dentaires des patients. Il en ressort que les patients sont demandeurs de soins et de paroles. Les soignants expriment certaines gênes et limites. Comment lever ces difficultés dans un cadre soignant ? Comment amorcer des processus permettant une meilleure prise en charge dentaire des patients ?
La réinfosphère brésilienne : fake news et intolérance dans la vie quotidienne numérique
Authors: Rezende Ribeiro Renata 
Published: April 2020

L’article provient d’une recherche vaste analysant l’utilisation des réseaux sociaux numériques dans la vie quotidienne. Dans cet article, nous discutons de la production de fake news à partir de la pratique de la « réinformation en ligne », indiquant comment les processus d’influence et d’opinion des utilisateurs peuvent contribuer à fomenter des discours d’intolérance par le biais d’un processus de catharsis associant politique et émotions.
La consommation nomadique des jeunes Coréens
Authors: Choi Hang-sub 
Published: April 2020

Alors que leurs conditions de vie continuent à se dégrader avec la crise économique, la jeune génération en Corée se concentre plutôt sur la valeur du présent que sur celle du futur, le plaisir d’être prend le pas sur le devoir. Leur style de consommation, très nomadique, illustre bien cette tendance. Le désir d’être vu, d’être admiré, passe par des voies immédiates avec la recherche de « mises en scène », d’images de leur vie quotidienne. En raison de la nouvelle mise en visibilité de la vie « variée » et « renouvelée », se crée un culte des nouveautés perpétuelles. La consommation basée sur le présentéisme leur permet de reléguer, même provisoirement, leur angoisse au second plan.
La place du beau dans le contemporain : un regard sur la mode
Authors: Pitombo Cidreira Renata 
Published: April 2020

Après la négation persistante du beau au XX e siècle et face à la multiplicité des interventions expressives de l’époque contemporaine, la problématique du beau a refait surface. La critique qui l’a refusée a suscité une question sur les nouvelles possibilités de reconnaissance de nouveaux standards de beauté, redéfinissant son rôle dans les processus de création et de jouissance d’aujourd’hui. Dans cette perspective, nous allons réfléchir à partir de ce questionnement sur la place du beau dans la contemporanéité, en prenant en compte ses spécificités et la possibilité d’absorption des formes dans l’actualité, à partir de son processus de création en passant par l’acte contemplatif de la réception, avec comme référence l’univers de la mode, en comprenant, selon Maffesoli (1996) que « le “beau” partagé avec d’autres est à la base de l’organisation de la techné et de la polis » (p. 156).