35 research outputs found
Magnetized Accretion-Ejection Structures: 2.5D MHD simulations of continuous Ideal Jet launching from resistive accretion disks
We present numerical magnetohydrodynamic (MHD) simulations of a magnetized
accretion disk launching trans-Alfvenic jets. These simulations, performed in a
2.5 dimensional time-dependent polytropic resistive MHD framework, model a
resistive accretion disk threaded by an initial vertical magnetic field. The
resistivity is only important inside the disk, and is prescribed as eta =
alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk
scale height and the coefficient alpha_m is smaller than unity. By performing
the simulations over several tens of dynamical disk timescales, we show that
the launching of a collimated outflow occurs self-consistently and the ejection
of matter is continuous and quasi-stationary. These are the first ever
simulations of resistive accretion disks launching non-transient ideal MHD
jets. Roughly 15% of accreted mass is persistently ejected. This outflow is
safely characterized as a jet since the flow becomes super-fastmagnetosonic,
well-collimated and reaches a quasi-stationary state. We present a complete
illustration and explanation of the `accretion-ejection' mechanism that leads
to jet formation from a magnetized accretion disk. In particular, the magnetic
torque inside the disk brakes the matter azimuthally and allows for accretion,
while it is responsible for an effective magneto-centrifugal acceleration in
the jet. As such, the magnetic field channels the disk angular momentum and
powers the jet acceleration and collimation. The jet originates from the inner
disk region where equipartition between thermal and magnetic forces is
achieved. A hollow, super-fastmagnetosonic shell of dense material is the
natural outcome of the inwards advection of a primordial field.Comment: ApJ (in press), 32 pages, Higher quality version available at
http://www-laog.obs.ujf-grenoble.fr/~fcass
Simulations of core convection in rotating A-type stars: Differential rotation and overshooting
We present the results of 3--D simulations of core convection within A-type
stars of 2 solar masses, at a range of rotation rates. We consider the inner
30% by radius of such stars, thereby encompassing the convective core and some
of the surrounding radiative envelope. We utilize our anelastic spherical
harmonic (ASH) code, which solves the compressible Navier-Stokes equations in
the anelastic approximation, to examine highly nonlinear flows that can span
multiple scale heights. The cores of these stars are found to rotate
differentially, with central cylindrical regions of strikingly slow rotation
achieved in our simulations of stars whose convective Rossby number (R_{oc}) is
less than unity. Such differential rotation results from the redistribution of
angular momentum by the nonlinear convection that strongly senses the overall
rotation of the star. Penetrative convective motions extend into the overlying
radiative zone, yielding a prolate shape (aligned with the rotation axis) to
the central region in which nearly adiabatic stratification is achieved. This
is further surrounded by a region of overshooting motions, the extent of which
is greater at the equator than at the poles, yielding an overall spherical
shape to the domain experiencing at least some convective mixing. We assess the
overshooting achieved as the stability of the radiative exterior is varied, and
the weak circulations that result in that exterior. The convective plumes serve
to excite gravity waves in the radiative envelope, ranging from localized
ripples of many scales to some remarkable global resonances.Comment: 48 pages, 16 figures, some color. Accepted to Astrophys. J. Color
figures compressed with appreciable loss of quality; a PDF of the paper with
better figures is available at
http://lcd-www.colorado.edu/~brownim/core_convectsep24.pd
Turbulent Convection Under the Influence of Rotation: Sustaining a Strong Differential Rotation
The intense turbulence present in the solar convection zone is a major
challenge to both theory and simulation as one tries to understand the origins
of the striking differential rotation profile with radius and latitude that has
been revealed by helioseismology. The differential rotation must be an
essential element in the operation of the solar magnetic dynamo and its cycles
of activity, yet there are many aspects of the interplay between convection,
rotation and magnetic fields that are still unclear. We have here carried out a
series of 3--D numerical simulations of turbulent convection within deep
spherical shells using our anelastic spherical harmonic (ASH) code on massively
parallel supercomputers. These studies of the global dynamics of the solar
convection zone concentrate on how the differential rotation and meridional
circulation are established. We have analyzed the transport of angular momentum
in establishing such differential rotation, and clarified the roles played by
Reynolds stresses and the meridional circulation in this process. We have found
that the Reynolds stresses are crucial in transporting angular momentum toward
the equator. The effects of baroclinicity (thermal wind) have been found to
have a modest role in the resulting mean zonal flows. The simulations have
produced differential rotation profiles within the bulk of the convection zone
that make reasonable contact with ones inferred from helioseismic inversions,
namely possessing a fast equator, an angular velocity difference of about 30%
from equator to pole, and some constancy along radial lines at mid-latitudes.Comment: 25 pages, 14 very low resolution figures, shortened abstract,
published by ApJ. High resolution/complete version can be found at
http://lcd-www.colorado.edu/sabrun/index_cv.html then Scientific Publication
Accretion Disks and Dynamos: Toward a Unified Mean Field Theory
Conversion of gravitational energy into radiation in accretion discs and the
origin of large scale magnetic fields in astrophysical rotators have often been
distinct topics of research. In semi-analytic work on both problems it has been
useful to presume large scale symmetries, necessarily resulting in mean field
theories. MHD turbulence makes the underlying systems locally asymmetric and
nonlinear. Synergy between theory and simulations should aim for the
development of practical mean field models that capture essential physics and
can be used for observational modeling. Mean field dynamo (MFD) theory and
alpha-viscosity accretion theory exemplify such ongoing pursuits. 21st century
MFD theory has more nonlinear predictive power compared to 20th century MFD
theory, whereas accretion theory is still in a 20th century state. In fact,
insights from MFD theory are applicable to accretion theory and the two are
artificially separated pieces of what should be a single theory. I discuss
pieces of progress that provide clues toward a unified theory. A key concept is
that large scale magnetic fields can be sustained via local or global magnetic
helicity fluxes or via relaxation of small scale magnetic fluctuations, without
the kinetic helicity driver of 20th century textbooks. These concepts may help
explain the formation of large scale fields that supply non-local angular
momentum transport via coronae and jets in a unified theory of accretion and
dynamos. In diagnosing the role of helicities and helicity fluxes in disk
simulations, each disk hemisphere should be studied separately to avoid being
misled by cancelation that occurs as a result of reflection asymmetry. The
fraction of helical field energy in disks is expected to be small compared to
the total field in each hemisphere as a result of shear, but can still be
essential for large scale dynamo action.Comment: For the Proceedings of the Third International Conference and
Advanced School "Turbulent Mixing and Beyond," TMB-2011 held on 21 - 28
August 2011 at the Abdus Salam International Centre for Theoretical Physics,
Trieste, http://users.ictp.it/~tmb/index2011.html Italy, To Appear in Physica
Scripta (corrected small items to match version in print
Launching of Conical Winds and Axial Jets from the Disk-Magnetosphere Boundary: Axisymmetric and 3D Simulations
We investigate the launching of outflows from the disk-magnetosphere boundary
of slowly and rapidly rotating magnetized stars using axisymmetric and
exploratory 3D magnetohydrodynamic (MHD) simulations. We find long-lasting
outflows in both cases. (1) In the case of slowly rotating stars, a new type of
outflow, a conical wind, is found and studied in simulations. The conical winds
appear in cases where the magnetic flux of the star is bunched up by the disk
into an X-type configuration. The winds have the shape of a thin conical shell
with a half-opening angle 30-40 degrees. The conical winds may be responsible
for episodic as well as long-lasting outflows in different types of stars. (2)
In the case of rapidly rotating stars (the "propeller regime"), a two-component
outflow is observed. One component is similar to the conical winds. A
significant fraction of the disk matter may be ejected into the winds. A second
component is a high-velocity, low-density magnetically dominated axial jet
where matter flows along the opened polar field lines of the star. The jet has
a mass flux about 10% that of the conical wind, but its energy flux (dominantly
magnetic) can be larger than the energy flux of the conical wind. The jet's
angular momentum flux (also dominantly magnetic) causes the star to spin-down
rapidly. Propeller-driven outflows may be responsible for the jets in
protostars and for their rapid spin-down. The jet is collimated by the magnetic
force while the conical winds are only weakly collimated in the simulation
region.Comment: 29 pages and 29 figures. This version has a major expansion after
comments by a referee. The 1-st version is correct but mainly describes the
conical wind. This version describes in greater detail both the conical winds
and the propeller regime. Accepted to the MNRA
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
Immune Biomarkers in Metastatic Castration-resistant Prostate Cancer.
BACKGROUND: Metastatic castration-resistant prostate cancer (mCRPC) is a heterogeneous disease in which molecular stratification is needed to improve clinical outcomes. The identification of predictive biomarkers can have a major impact on the care of these patients, but the availability of metastatic tissue samples for research in this setting is limited. OBJECTIVE: To study the prevalence of immune biomarkers of potential clinical utility to immunotherapy in mCRPC and to determine their association with overall survival (OS). DESIGN, SETTING, AND PARTICIPANTS: From 100 patients, mCRPC biopsies were assayed by whole exome sequencing, targeted next-generation sequencing, RNA sequencing, tumor mutational burden, T-cell-inflamed gene expression profile (TcellinfGEP) score (Nanostring), and immunohistochemistry for programmed cell death 1 ligand 1 (PD-L1), ataxia-telangiectasia mutated (ATM), phosphatase and tensin homolog (PTEN), SRY homology box 2 (SOX2), and the presence of neuroendocrine features. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The phi coefficient determined correlations between biomarkers of interest. OS was assessed using Kaplan-Meier curves and adjusted hazard ratios (aHRs) from Cox regression. RESULTS AND LIMITATIONS: PD-L1 and SOX2 protein expression was detected by immunohistochemistry (combined positive score ≥1 and >5% cells, respectively) in 24 (33%) and 27 (27%) mCRPC biopsies, respectively; 23 (26%) mCRPC biopsies had high TcellinfGEP scores (>-0.318). PD-L1 protein expression and TcellinfGEP scores were positively correlated (phi 0.63 [0.45; 0.76]). PD-L1 protein expression (aHR: 1.90 [1.05; 3.45]), high TcellinfGEP score (aHR: 1.86 [1.04; 3.31]), and SOX2 expression (aHR: 2.09 [1.20; 3.64]) were associated with worse OS. CONCLUSIONS: PD-L1, TcellinfGEP score, and SOX2 are prognostic of outcome from the mCRPC setting. If validated, predictive biomarker studies incorporating survival endpoints need to take these findings into consideration. PATIENT SUMMARY: This study presents an analysis of immune biomarkers in biopsies from patients with metastatic prostate cancer. We describe tumor alterations that predict prognosis that can impact future studies
HER3 Is an Actionable Target in Advanced Prostate Cancer.
It has been recognized for decades that ERBB signaling is important in prostate cancer, but targeting ERBB receptors as a therapeutic strategy for prostate cancer has been ineffective clinically. However, we show here that membranous HER3 protein is commonly highly expressed in lethal prostate cancer, associating with reduced time to castration resistance (CR) and survival. Multiplex immunofluorescence indicated that the HER3 ligand NRG1 is detectable primarily in tumor-infiltrating myelomonocytic cells in human prostate cancer; this observation was confirmed using single-cell RNA sequencing of human prostate cancer biopsies and murine transgenic prostate cancer models. In castration-resistant prostate cancer (CRPC) patient-derived xenograft organoids with high HER3 expression as well as mouse prostate cancer organoids, recombinant NRG1 enhanced proliferation and survival. Supernatant from murine bone marrow-derived macrophages and myeloid-derived suppressor cells promoted murine prostate cancer organoid growth in vitro, which could be reversed by a neutralizing anti-NRG1 antibody and ERBB inhibition. Targeting HER3, especially with the HER3-directed antibody-drug conjugate U3-1402, exhibited antitumor activity against HER3-expressing prostate cancer. Overall, these data indicate that HER3 is commonly overexpressed in lethal prostate cancer and can be activated by NRG1 secreted by myelomonocytic cells in the tumor microenvironment, supporting HER3-targeted therapeutic strategies for treating HER3-expressing advanced CRPC. SIGNIFICANCE: HER3 is an actionable target in prostate cancer, especially with anti-HER3 immunoconjugates, and targeting HER3 warrants clinical evaluation in prospective trials
Diagnostics of surface geometric structure state with developed sculpture
W niniejszym opracowaniu przedstawiono pewien sposób oceny powierzchni, w którym wykorzystano metodę pomiaru geometrycznych cech wgłębień występujących w strukturze geometrycznej powierzchni roboczych łożysk tocznych. Wykorzystując specjalistyczną aparaturę pomiarową Talyscan, dla wgłębień i pików określono: powierzchnię objętość, maksymalną oraz średnią wartość głębokości lub wysokości. Wyniki przeprowadzonych badań doświadczalnych świadczą o tym, że możliwe jest opisanie za pomocą proponowanej metody zmian, jakie zaszły w strukturze geometrycznej badanych powierzchni podczas procesu zużywania.In this paper some method of surface estimation was shown. To this aim measures geometric features of holes and pikes exist in geometric structure of tested surfaces of rolling bearings were used. Appilicating specialistic measuring Talyscan apparatus, for the holes and the pikes following quantities were obtained: area, volume, maximum and average values of depth or height, respectively. The results of worked out experimental investigations confirm ability of description by mentioned method of the changes in geometric structure of tested surfaces which occur during wear processes. Thus, there are possibilities applications of these results in diagnostic processes