&lt;b&gt;Valor prognóstico de marcadores imunohistoquímicos em mastocitomas cutâneos caninos&lt;/b&gt;

Freytag, Jennifer

doi:10.11606/d.10.2017.tde-24042017-153940

Cited by 6 publications

(17 citation statements)

References 71 publications

(195 reference statements)

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“…Interestingly, much larger values of the mixing length parameter are required for an MLT model to match the peak fluxes of the nonlocal model, while the quantitative agreement of the latter with 2D numerical simulations of Freytag (1995) is comparable to that one found for A-stars. Limitations of the current nonlocal model become clear when computations for deep convection zones (similar to the case discussed by Trampedach 2005) are performed.…”

Section: Modelling Convection In A-star Envelopessupporting

confidence: 63%

“…That discrepancy is even more evident when considering the velocity fields. A comparison for the vertical root mean square convective velocity for the same nonlocal model, the MLT model, and the numerical simulations by Freytag (1995) has already been shown by Kupka (2003). For the MLT model the flow remains localised to the middle of the partial ionisation zones, predicts too small velocities for the lower lying convection zone, and neglects overshooting.…”

Section: Modelling Convection In A-star Envelopessupporting

confidence: 52%

“…Compared to that a modification of the original model of Canuto et al (2001) transport as done by Kupka & Montgomery (2002) results only in a small change. The simulations shown by Freytag (2005) at this conference improve over their predecessors in Freytag (1995) also by replacing the 2D geometry with a 3D one and by using updated microphysics. Still, the MLT model remains to be by far the one most discrepant from the others.…”

Section: Modelling Convection In A-star Envelopesmentioning

confidence: 93%

“…An improvement of that model of nonlocal transport was suggested by Canuto et al (2001) and in this form the convection model was adopted by Kupka & Montgomery (2002) to compute envelope models for A-stars. These computations ranged from the mid-photosphere down into layers where T ∼ 100000 K. Figure 1 shows a comparison of the convective enthalpy (heat) flux for a mid A-type Main Sequence star with a numerical simulation by Freytag (1995) and with an MLT model tuned to match the peak flux of the nonlocal model. The MLT model would require a mixing length four times as large to obtain the convective flux found in both the nonlocal model and the numerical simulation for the lower lying (He ii) convection zone.…”

Section: Modelling Convection In A-star Envelopesmentioning

confidence: 99%

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Convection in stars

Kupka¹

2004

Proc. IAU

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Abstract. Convection is one of the most intricate processes studied in stellar astrophysics and has challenged both theorists and observers since the beginnings of astrophysics. But during the last two decades observational data of unprecedented resolution and accuracy have been collected in solar and stellar research which permit a new look at the field. An enormous increase of computer speed now permits solving more complete model equations with more accurate numerical approximations. Modelling and theoretical understanding of convection, however, are lagging behind observational progress and are still wanting.As a background to the contributions to this session on convection, I first provide an overview on its basic physics and its observational evidence. I point out why astrophysicists have a general interest in improvements of our understanding of stellar convection and then focus on convection in A-stars with their unique combination of convection zones. I summarise how this richness of different manifestations can arise in A-stars, such as convection zones near the surface and in the core, several on top of each other, or some of them depleted by diffusion processes, suppressed by or even creating magnetic fields, suspected to create a chromosphere in some of them, or influenced by binaries, to name just a few. In the last part I will present a few recent results on modelling of convection in A-stars.

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Section: Modelling Convection In A-star Envelopessupporting

confidence: 63%

Section: Modelling Convection In A-star Envelopessupporting

confidence: 52%

Section: Modelling Convection In A-star Envelopesmentioning

confidence: 93%

Section: Modelling Convection In A-star Envelopesmentioning

confidence: 99%

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Convection in stars

Kupka¹

2004

Proc. IAU

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“…Thus, we find that the mass of material 'stirred' by the convection zone is an order of magnitude larger than that which is formally unstable according to a local stability criterion. Among other things, this can have consequences for the diffusion of elements in white dwarf envelopes, as was pointed out by Freytag (1995) and Freytag, Ludwig & Steffen (1996), who, in addition, found an even larger amount of material stirred below the convection zone in their numerical simulations of DA envelopes (see also Section 5).…”

Section: Da Modelsmentioning

confidence: 88%

White dwarf envelopes: further results of a non-local model of convection

Montgomery¹,

Kupka²

2004

Monthly Notices of the Royal Astronomical Society

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We present results of a fully non‐local model of convection for white dwarf envelopes. We show that this model is able to reproduce the results of numerical simulations for convective efficiencies ranging from very inefficient to moderately efficient; this agreement is made more impressive given that no closure parameters have been adjusted in going from the previously reported case of A‐stars to the present case of white dwarfs. For comparison, in order to match the peak convective flux found in numerical simulations for both the white dwarf envelopes discussed in this paper and the A‐star envelopes discussed in our previous work requires changing the mixing length parameter of commonly used local models by a factor of 4. We also examine in detail the overshooting at the base of the convection zone, both in terms of the convective flux and in terms of the velocity field; we find that the flux overshoots by ∼1.25 HP and the velocity by ∼2.5 HP. Because of the large amount of overshooting found at the base of the convection zone, the new model predicts the mixed region of white dwarf envelopes to contain at least 10 times more mass than local mixing length theory (MLT) models having similar photospheric temperature structures. This result is consistent with the upper limit given by numerical simulations which predict an even larger amount of mass to be mixed by convective overshooting. Finally, we attempt to parametrize some of our results in terms of local MLT‐based models, insofar as is possible given the limitations of MLT.

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Radiative hydrodynamics models of stellar convection

Steffen¹

2006

Proc. IAU

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In the quest for a better theoretical understanding of the dynamical processes operating in stellar envelopes, increasingly more realistic hydrodynamical models of stellar convection have been developed over the last 25 years. Based on 3D state-of-the-art simulations performed recently with the radiation hydrodynamics code CO5BOLD, we review the present status of hydrodynamical modeling of stellar surface convection and demonstrate the basic differences between 3D hydrodynamical models and 1D ‘classical’ hydrostatic atmospheres where convection is treated by the mixing-length theory. We briefly discuss some of the many possible applications across the Hertzsprung-Russell diagram, including spectroscopic abundance determinations using 3D stellar atmospheres, particularly with regard to the much debated question of the solar oxygen abundance.

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<b>Valor prognóstico de marcadores imunohistoquímicos em mastocitomas cutâneos caninos</b>

Abstract: FREYTAG, J. O. Prognostic value of immunohistochemical markers in canine cutaneous mast cell tumors. [Valor prognóstico de marcadores imunohistoquímicos em mastocitomas cutâneo canino] 2017. 76 f. Dissertação (Mestrado

Cited by 6 publications

References 71 publications

Convection in stars

Convection in stars

White dwarf envelopes: further results of a non-local model of convection

Radiative hydrodynamics models of stellar convection

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