scholarly journals Feeding and Small-scale Feedback in Low-Luminosity AGNs

2012 ◽  
Vol 8 (S290) ◽  
pp. 74-77
Author(s):  
Roman V. Shcherbakov ◽  
Frederick K. Baganoff ◽  
Ka-Wah Wong ◽  
Jimmy Irwin
Keyword(s):  
Event Horizon ◽  
Gas Flow ◽  
Random Motion ◽  
Small Scale ◽  
Flow Density ◽  
Stellar Winds ◽  
Density Profiles ◽  
Gravitational Influence ◽  
Sgr A

AbstractThe unmatched X-ray resolution of Chandra allows probing the gas flow near quiescent supermassive black holes (BHs). The radius of BH gravitational influence on gas, called the Bondi radius, is resolved in Sgr A* and NGC 3115. Shallow accretion flow density profiles n ∝ r−β with β=0.7–1.0 were found for Sgr A* and NGC 3115 with the help of Chandra. We construct self-consistent models with gas feeding and dynamics from near the Bondi radius to the event horizon to explain the observations. Gas is mainly supplied to the region by hot colliding stellar winds. Small-scale feedback such as conduction effectively flattens the density profile from steep β=1.5 in a Bondi flow. We further constrain density and temperature profiles using the observed radio/sub-mm radiation emitted near the event horizon. We discuss the present state of our numerical model and its qualitative features, such as the role of the galactic gravitational potential and the random motion of wind-emitting stars.

scholarly journals The surprisingly small impact of magnetic fields on the inner accretion flow of Sagittarius A* fueled by stellar winds

2019 ◽  
Vol 492 (3) ◽  
pp. 3272-3293 ◽  
Author(s):  
S M Ressler ◽  
E Quataert ◽  
J M Stone
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Event Horizon ◽  
Initial Conditions ◽  
Rotational Instability ◽  
Stellar Winds ◽  
Accretion Flow ◽  
Sagittarius A ◽  
Mhd Simulations ◽  
Sgr A

ABSTRACT We study the flow structure in 3D magnetohydrodynamic (MHD) simulations of accretion on to Sagittarius A* via the magnetized winds of the orbiting Wolf–Rayet stars. These simulations cover over 3 orders of magnitude in radius to reach ≈300 gravitational radii, with only one poorly constrained parameter (the magnetic field in the stellar winds). Even for winds with relatively weak magnetic fields (e.g. plasma β ∼ 106), flux freezing/compression in the inflowing gas amplifies the field to β ∼ few well before it reaches the event horizon. Overall, the dynamics, accretion rate, and spherically averaged flow profiles (e.g. density, velocity) in our MHD simulations are remarkably similar to analogous hydrodynamic simulations. We attribute this to the broad distribution of angular momentum provided by the stellar winds, which sources accretion even absent much angular momentum transport. We find that the magneto-rotational instability is not important because of (i) strong magnetic fields that are amplified by flux freezing/compression, and (ii) the rapid inflow/outflow times of the gas and inefficient radiative cooling preclude circularization. The primary effect of magnetic fields is that they drive a polar outflow that is absent in hydrodynamics. The dynamical state of the accretion flow found in our simulations is unlike the rotationally supported tori used as initial conditions in horizon scale simulations, which could have implications for models being used to interpret Event Horizon Telescope and GRAVITY observations of Sgr A*.

The role of collective identifications in family processes of post-trauma reconstruction: An exploratory study with Kurdish refugee families and their diasporic community

2017 ◽  
Vol 5 (2) ◽  
pp. 107-133 ◽  
Author(s):  
Ruth Kevers ◽  
Peter Rober ◽  
Lucia De Haene
Keyword(s):  
Thematic Analysis ◽  
Exploratory Study ◽  
Meaning Making ◽  
Family Processes ◽  
Small Scale ◽  
Refugee Families ◽  
Family Contexts ◽  
Diasporic Community ◽  
And Coping

While collective identifications of diasporic Kurds have attracted considerable scholarly interest, their possible role in familial processes of post-trauma reconstruction has hardly been studied. The aim of this article is therefore to develop an explorative understanding of the deployment and meaning of collective identifications in intimate family contexts by examining the interconnectedness between the transmission of cultural and political belonging and post-trauma meaning-making and coping in Kurdish refugee families. After contextualising diasporic Kurds’ collective identifications through an ethnographic depiction of the Kurdish diasporic community in Belgium, this article reports on findings from a small-scale, exploratory study with five Kurdish refugee families in Belgium. Thematic analysis of family and parent interviews indicates how cultural and political identifications may operate as sources of (1) dealing with cultural bereavement and loss; (2) commemorating trauma; and (3) reversing versus reiterating trauma. Overall, this study’s findings support an explorative understanding of collective identifications as meaningful resources in families’ post-trauma reconstruction.ABSTRACT IN KURMANJIRola nasnameyên komelî di pêvajoyên malbatî yên vesazkirina paş-trawmayê de: Xebateke raveker li ser malbatên kurd ên penaber û civakên wan ên dîasporayêTevî ku nasnameyên komelî yên kurdên dîasporayê ta radeyeke baș bûye mijara lêkolînan, rola wan a muhtemel di pêvajoyên malbatî yên vesazkirina (selihandin) paş-trawmayê qet nehatine vekolîn. Lewma armanca vê gotarê ew e têgihiştineke raveker pêş bixe li ser rol û wateya nasnameyên komelî yên di çarçoveya mehremiya malbatê de, ku vê yekê jî dê bi rêya vekolîna wê têkiliya rijd bike ya di navbera neqlkirina aidiyetên çandî-siyasî û rêyên sazkirina wateyê û serederîkirina li dû trawmayê di nav malbatên kurd ên penaber de. Piştî diyarkirina çarçoveya nasnameya komelî ya Kurdên diasporayê bi rêya teswîreke etnografîk a cemaeta diasporaya Kurd li Belçîkayê, ev gotar encamên ji xebateke biçûk a bi pênc malbatên kurd ên penaber ên li Belçîkayê pêşkêş dike. Tehlîla babetî ya hevpeyvînên ligel malbatan û dayik û bavan nîşan dide ka çawa nasnameyên çandî û siyasî dikarin bibin çavkanî ji bo (1) serederîkirina bi mehrûmiyeta çandî û windahiyên xwe; (2) bibîranîna trawmayê; û (3) kêmrengkirin an, beramber vê yekê, dubarekirina trawmayê. Bi giştî, encamên vê xebatê wê têgihiştineke raveker tesdîq dikin ku nasnameyên kolektîf çavkaniyên kêrhatî ne di vesazkirina paş-trawmayê ya malbatan de. ABSTRACT IN SORANIDewrî nasname bekomellekan le prose binemalleyîyekanî sazkirdinewey paş-trawmayîda: lêkollîneweyekî şirovekarî binemalle penabere kurdekan û civatî ewan le diyasporaLe katêkda nasname bekomellekanî kurdekanî diyaspora le layen şarezakanewe giringîyekî berçawî pê drawe û serincî ewanî bo lay xoyî rakêşawe, bellam sebaret be egerî dewrî prose binemalleyîyekanî sazkirdinewey paş-tirawma be degmen lêkollîneweyek encam drawe. Ke wate, amancî em wutare perepêdan be têgeyîştinêkî şirovekarane lemerr bekarhênan û manay nasname bekomellekan le bestênekanî têkellawîy binemalleyîdaye, ke le rêgey peywendîy nêwan rewtî gwastineweyî grêdraweyî kultûrî û siyasî, sazbûnî mana û herweha rahatin legell kêşekanî qonaẍî paş tirawma le binemalle kurde penaberekanda taqî krawetewe. Dway awirrdanewe le civakî diyasporay kurd le Belcîka, nasname bekomellekanî kurdekanî diyaspora le bestênî xoyda xwêndinewey bo krawe û bem gêreye lem wutareda lêkollîneweyekî şirovekarane bo qebareyekî biçûk le pênc binemalley kurdî penaber le Belcîka dekrê û encamekanî billaw dekrêtewe. Şîkarîyekî babetiyaney wutuwêj legell binemalle û dayk û bawkekan nîşanî dedat ke çon dekrê nasname kultûrî û siyasîyekan wek serçaweyek bo em sê mijare derbikewn: (1) gîrodebûn be ledestçûn û bizirbûnî kultûr; (2) webîrhênanewey tirawma; û (3) pêçewanebûnî tirawma leberamber dûbarebûneweyda. Beşêweyekî giştî, encamekanî em lêkollîneweye piştgîrî le têgeyîştinêkî şirovekarane le nasname bekomellekan dekat ke wekû serçaweyekî giring bo sazkirdinewey binemallekan le dway qonaẍî paş-tirawma seyr dekrêt.

GOELRO plan is 100 years old

2020 ◽  
Vol 12 (12) ◽  
pp. 4-9
Author(s):  
Pavel A. BUTYRIN ◽  
Keyword(s):  
Agricultural Production ◽  
Historical Context ◽  
Soviet Period ◽  
Small Scale ◽  
Efficient Production ◽  
Soviet Republic ◽  
Starting Conditions ◽  
Per Capita ◽  
State Plan

The historical context in which the State Plan for Electrification of Russia (GOELRO) was developed, establishment of the GOELRO Commission, the GOELRO Plan content, the specific features of its implementation, and the role of the plan in the soviet period of Russia’s history are considered. Attention is paid to the electrification plants of other countries and territories of all inhabited continents, and to the participation of states in the electrification of countries and regions with small-scale and agricultural production in the 1920 s. The specific features pertinent to the electrification of the Russian Socialist Federative Soviet Republic are pointed out, namely, low starting conditions (in 1923, the energy consumption per capita in Russia was 100 times lower than that in Norway), its being state-owned in nature and revolutionary in its purpose: to get done with the main upheavals in the country and to shift the national economy for fore efficient production. The role of V.I. Lenin and G.M. Krzhizhanovsky, who were the initiators of the electrification of Russia, is analyzed in detail. A conclusion is drawn about the need to study both the GOELRO Plan itself and the specific features and circumstances of its implementation within the framework of training modern specialists in electrical engineering.

scholarly journals Metrics and Motivations for Earth–Space VLBI: Time-resolving Sgr A* with the Event Horizon Telescope

2019 ◽  
Vol 881 (1) ◽  
pp. 62 ◽  
Author(s):  
Daniel C. M. Palumbo ◽  
Sheperd S. Doeleman ◽  
Michael D. Johnson ◽  
Katherine L. Bouman ◽  
Andrew A. Chael
Keyword(s):  
Event Horizon ◽  
Earth Space ◽  
Sgr A

scholarly journals Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

2016 ◽  
Vol 461 (1) ◽  
pp. 552-559 ◽  
Author(s):  
S. Dibi ◽  
S. Markoff ◽  
R. Belmont ◽  
J. Malzac ◽  
J. Neilsen ◽  
...  
Keyword(s):  
Event Horizon ◽  
X Ray ◽  
Sgr A

The role of gas flow distributions on CO2 mineralization within monolithic cemented composites: coupled CFD-factorial design approach

2021 ◽  
Author(s):  
Iman Mehdipour ◽  
Gabriel Falzone ◽  
Dale Prentice ◽  
Narayanan Neithalath ◽  
Dante Simonetti ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Factorial Design ◽  
Material Properties ◽  
Gas Flow ◽  
Design Approach ◽  
Processing Conditions ◽  
Gas Processing ◽  
Co2 Mineralization

Optimizing the spatial distribution of contacting gas and the gas processing conditions enhances CO2 mineralization reactions and material properties of carbonate-cementitious monoliths.

Sign in / Sign up

Export Citation Format

Share Document