Exercise-Based Rehabilitation in Patients with Lung Cancer

Spruit, Martijn A.; Mansour, Khaled A; Wouters, Emiel F.M.; Hochstenbag, Monique

doi:10.1007/978-1-4419-1173-5_10

Cited by 13 publications

(30 citation statements)

References 61 publications

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“…We conclude that our simple estimates support the hypothesis that accretion can provide at least some level of turbulence in circumstellar T Tauri disks. Even if it can sustain a significant amount of turbulence, the question as to whether this turbulence could transport angular momentum efficiently is entirely open (although see Spruit 1987). BecauseṀ varies with M as illustrated in Fig.…”

Section: Expected Velocity Dispersion In Accretion Disksmentioning

confidence: 99%

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Klessen¹,

Hennebelle²

2010

A&A

318

353

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Context. Even though turbulent motions are found everywhere in astrophysical systems, the origin of this turbulence is poorly understood. When cosmic structures form, they grow in mass via accretion from their surrounding environment. Aims. We propose that accretion is able to drive internal turbulent motions in a wide range of astrophysical objects and study this process in the case of galaxies, molecular clouds, and protoplanetary disks. Methods. We use a combination of numerical simulations and analytical arguments to predict the level of turbulence as a function of the accretion rate, the dissipation scale, and the density contrast, and compare our models with observational data. Results. We find that in Milky Way type galaxies the observed level of turbulence in the interstellar medium can be explained by accretion, provided that the galaxies gain mass at a rate comparable to the rate at which they form stars. This process is particularly relevant in the extended outer disks beyond the star-forming radius. For it to drive turbulence in dwarf galaxies, the accretion rate needs to exceed the star formation rate by a large factor, so we expect other sources to dominate. We also calculate the rate at which molecular clouds grow in mass when they build up from the atomic component of the galactic gas and find that their internal turbulence is likely to be driven by accretion as well. It is the very process of cloud formation that excites turbulent motions on small scales by establishing the turbulent cascade. In the case of T Tauri disks, we show that accretion can drive subsonic turbulence if the rate at which gas falls onto the disk is comparable to the rate at which disk material accretes onto the central star. This also explains the observed relation of accretion rate and stellar mass,Ṁ ∝ M 1.8 . The efficiency required to convert infall motion into turbulence is a few percent in all three cases. Conclusions. We conclude that accretion-driven turbulence is a universal concept with far-reaching implications for a wide range of astrophysical objects.

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Section: Expected Velocity Dispersion In Accretion Disksmentioning

confidence: 99%

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Klessen¹,

Hennebelle²

2010

A&A

318

353

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“…On the theoretical side, properties of spiral shocks in accretion disks were first considered under the assumption of self-similarity, starting with the work of Spruit (1987), Spruit et al (1987), and Larson (1990). More recently, self-similar shock solutions in disks were constructed by Hennebelle et al (2016) with the goal of explaining spiral waves observed in simulations of disks with the envelope infall (Lesur et al 2015).…”

mentioning

confidence: 99%

Disk Accretion Driven by Spiral Shocks

Arzamasskiy¹,

Rafikov²

2018

ApJ

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Spiral density waves are known to exist in many astrophysical disks, potentially affecting disk structure and evolution. We conduct a numerical study of the effects produced by a density wave, evolving into a shock, on the characteristics of the underlying disk. We measure the deposition of angular momentum in the disk by spiral shocks of different strength and verify the analytical prediction of Rafikov (2016) for the behavior of this quantity, using shock amplitude (which is potentially observable) as the input variable. Good agreement between the theory and numerics is found as we vary shock amplitude (including highly nonlinear shocks), disk aspect ratio, equation of state, radial profiles of the background density and temperature, and pattern speed of the wave. We show that high numerical resolution is required to properly capture shock-driven transport, especially at low wave amplitudes. We also demonstrate that relating local mass accretion rate to shock dissipation in rapidly evolving disks requires accounting for the time-dependent contribution to the angular momentum budget, caused by the time dependence of the radial pressure support. We provide a simple analytical prescription for the behavior of this contribution and demonstrate its excellent agreement with the simulation results. Using these findings we formulate a theoretical framework for studying one-dimensional (in radius) evolution of the shock-mediated accretion disks, which can be applied to a variety of astrophysical systems.

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“…This is to be expected however, as shocks can result from the accretion disk of the AGN (e.g. Spruit 1987;Molteni et al 1994;Sponholz & Molteni 1994).…”

Section: Resultsmentioning

confidence: 99%

A new diagnostic to separate line emission from star formation, shocks, and AGNs simultaneously in IFU data

D'Agostino

Kewley

Groves

et al. 2019

Monthly Notices of the Royal Astronomical Society: Letters

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In the optical spectra of galaxies, methods for the separation of line emission arising from star formation and an additional hard component, such as shocks or AGN, is wellunderstood and possible with current diagnostics. However, such diagnostics fail when attempting to separate and define line emission which arises from shocked gas, and that arising from AGN. We present a new three-dimensional diagnostic diagram for IFU data which can simultaneously separate the line emission amongst star formation, shocks, and AGN within a galaxy. We show that regions we define as AGN-dominated correlate well with the hard X-ray distribution in our test case NGC 1068, as well as with known regions of AGN activity in NGC 1068. Similarly, spaxels defined as shock-dominated correlate strongly with regions of high velocity dispersion within the galaxy.

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Exercise-Based Rehabilitation in Patients with Lung Cancer

Cited by 13 publications

References 61 publications

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Disk Accretion Driven by Spiral Shocks

A new diagnostic to separate line emission from star formation, shocks, and AGNs simultaneously in IFU data

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