2,433 research outputs found
ets-2 is a target for an akt (Protein kinase B)/jun N-terminal kinase signaling pathway in macrophages of motheaten-viable mutant mice
A cosmic ray cocoon along the X-ray jet of M87?
Relativistic jets propagating through an ambient medium must produce some
observational effects along their side boundaries because of interactions
across the large velocity gradient. One possible effect of such an interaction
would be a sheared magnetic field structure at the jet boundaries, leading to a
characteristic radio polarization pattern. As proposed by Ostrowski, another
effect can come from the generation of a high energy cosmic ray component at
the boundary, producing dynamic effects on the medium surrounding the jet and
forming a cocoon dominated by cosmic rays with a decreased thermal gas
emissivity. We selected this process for our first attempt to look for the
effects of this type of interaction. We analyzed the Chandra X-ray data for the
radio galaxy M87 in order to verify if the expected regions of diminished
emissivity may be present near the spectacular X-ray jet in this source. The
detailed analysis of the data, merged from 42 separate observations, shows
signatures of lower emissivity surrounding the jet. In particular we detect an
intensity dip along the part of the jet, which would be approximately 150 pc x
2 kpc in size, if situated along the jet which is inclined toward us. Due to a
highly non-uniform X-ray background in the central region we are not able to
claim the discovery of a cosmic ray cocoon around the M87 jet: we only have
demonstrated that the data show morphological structures which could be
accounted for if a cosmic ray cocoon exists.Comment: 8 pages, 8 pictures accepted for publication in MNRA
On the Interaction of the PKS B1358-113 Radio Galaxy with the Abell 1836 Cluster
[abridged] Here we present the analysis of multifrequency data gathered for
the FRII radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy of
Abell 1836. The galaxy harbors one of the most massive black holes known to
date and our analysis of the optical data reveals that this black hole is only
weakly active. Based on new Chandra and XMM-Newton X-ray observations and
archival radio data we derive the preferred range for the jet kinetic
luminosity erg s. This is above the values
implied by various scaling relations proposed for radio sources in galaxy
clusters, being instead very close to the maximum jet power allowed for the
given accretion rate. We constrain the radio source lifetime as
Myrs, and the total amount of deposited jet energy \,ergs. The detailed analysis of the X-ray data provides indication for
the presence of a bow-shock driven by the expanding radio lobes into the Abell
1836 cluster environment, with the corresponding Mach number . This,
together with the recently growing evidence that powerful FRII radio galaxies
may not be uncommon in the centers of clusters at higher redshifts, supports
the idea that jet-induced shock heating may indeed play an important role in
shaping the properties of clusters, galaxy groups, and galaxies in formation.
We speculate on a possible bias against detecting jet-driven shocks in poorer
environments, resulting from an inefficient electron heating at the shock
front, combined with a relatively long electron-ion equilibration timescale.Comment: Version accepted to Ap
Differentiation of the mononuclear phagocyte system during mouse embryogenesis:the role of transcription factor PU.1
Ras-mediated phosphorylation of a conserved threonine residue enhances the transactivation activities of c-Ets1 and c-Ets2
The Ras oncogene products regulate the expression of genes in transformed cells, and members of the Ets family of transcription factors have been implicated in this process. To determine which Ets factors are the targets of Ras signaling pathways, the abilities of several Ets factors to activate Ras-responsive enhancer (RRE) reporters in the presence of oncogenic Ras were examined. In transient transfection assay, reporters containing RREs composed of Ets-AP-1 binding sites could be activated 30-fold in NIH 3T3 fibroblasts and 80-fold in the macrophage-like line RAW264 by the combination of Ets1 or Ets2 and Ras but not by several other Ets factors that were tested in the assay. Ets2 and Ras also superactivated an RRE composed of Ets-Ets binding sites, but the Ets-responsive promoter of the c-fms gene was not superactivated. Mutation of a threonine residue to alanine in the conserved amino-terminal regions of Ets1 and Ets2 (threonine 38 and threonine 72, respectively) abrogated the ability of each of these proteins to superactivate reporter gene expression. Phosphoamino acid analysis of radiolabeled Ets2 revealed that Ras induced normally absent threonine-specific phosphorylation of the protein. The Ras-dependent increase in threonine phosphorylation was not observed in Ets2 proteins that had the conserved threonine 72 residue mutated to alanine or serine. These data indicate that Ets1 and Ets2 are specific nuclear targets of Ras signaling events and that phosphorylation of a conserved threonine residue is a necessary molecular component of Ras-mediated activation of these transcription factors
INTEGRAL observations of TeV plerions
Amongst the sources seen in very high gamma-rays several are associated with
Pulsar Wind Nebulae (``TeV plerions''). The study of hard X-ray/soft gamma-ray
emission is providing an important insight into the energetic particle
population present in these objects. The unpulsed emission from pulsar/pulsar
wind nebula systems in the energy range accessible to the INTEGRAL satellite is
mainly synchrotron emission from energetic and fast cooling electrons close to
their acceleration site. Our analyses of public INTEGRAL data of known TeV
plerions detected by ground based Cherenkov telescopes indicate a deeper link
between these TeV plerions and INTEGRAL detected pulsar wind nebulae. The newly
discovered TeV plerion in the northern wing of the Kookaburra region
(G313.3+0.6 powered by the middle aged PSR J1420-6048) is found to have a
previously unknown INTEGRAL counterpart which is besides the Vela pulsar the
only middle aged pulsar detected with INTEGRAL. We do not find an INTEGRAL
counterpart of the TeV plerion associated with the X-ray PWN ``Rabbit''
G313.3+0.1 which is possibly powered by a young pulsar.Comment: 4 pages, 6 figures, proceedings of conference "The Multi-Messenger
Approach to High-Energy Gamma-ray Sources" Barcelona/Spain (2006
Signatures of the disk-jet coupling in the Broad-line Radio Quasar 4C+74.26
Here we explore the disk-jet connection in the broad-line radio quasar
4C+74.26, utilizing the results of the multiwavelength monitoring of the
source. The target is unique in that its radiative output at radio wavelengths
is dominated by a moderately-beamed nuclear jet, at optical frequencies by the
accretion disk, and in the hard X-ray range by the disk corona. Our analysis
reveals a correlation (local and global significance of 96\% and 98\%,
respectively) between the optical and radio bands, with the disk lagging behind
the jet by days. We discuss the possible explanation for this,
speculating that the observed disk and the jet flux changes are generated by
magnetic fluctuations originating within the innermost parts of a truncated
disk, and that the lag is related to a delayed radiative response of the disk
when compared with the propagation timescale of magnetic perturbations along
relativistic outflow. This scenario is supported by the re-analysis of the
NuSTAR data, modelled in terms of a relativistic reflection from the disk
illuminated by the coronal emission, which returns the inner disk radius
. We discuss the global energetics in
the system, arguing that while the accretion proceeds at the Eddington rate,
with the accretion-related bolometric luminosity erg s , the jet total kinetic energy
erg s, inferred from the dynamical
modelling of the giant radio lobes in the source, constitutes only a small
fraction of the available accretion power.Comment: 9 pages and 6 figures, ApJ accepte
Radiation from the Relativistic Jet: a Role of the Shear Boundary Layer
Recent radio and optical large scale jets' observations suggest a
two-component jet morphology, consisting of a fast central spine surrounded
with a boundary layer with a velocity shear. We study radiation of electrons
accelerated at such boundary layers as an option for standard approaches
involving internal shocks in jets. The acceleration process in the boundary
layer yields in a natural way a two component electron distribution: a
power-law continuum with a bump at the energy, where energy gains equal
radiation losses, followed by a cut-off. For such distributions we derive the
observed spectra of synchrotron and inverse-Compton radiation, including
comptonization of synchrotron and CMB photons. Under simple assumptions of
energy equipartition between the relativistic particles and the magnetic field,
the relativistic jet velocity at large scales and a turbulent character of the
shear layer, the considered radiation can substantially contribute to the jet
radiative output. In the considered conditions the synchrotron emission is
characterized by a spectral index of the radio-to-optical continuum being
approximately constant along the jet. A characteristic feature of the obtained
broad-band synchrotron spectrum is an excess at X-ray frequencies, similar to
the one observed in some objects by Chandra. As compared to the uniform jet
models, the velocity shear across the radiating boundary region leads to
decrease and frequency dependence of the observed jet-counterjet radio
brightness asymmetry. We conclude that a careful investigation of the
observational data looking for the derived effects can allow to evaluate the
role of the boundary layer acceleration processes and/or impose constraints for
the physical parameters of such layers in large scale jets.Comment: 30 pages, 4 figures included. Modified version, accepted for
publication in Astrophysical Journa
Repetitions in infinite palindrome-rich words
Rich words are characterized by containing the maximum possible number of
distinct palindromes. Several characteristic properties of rich words have been
studied; yet the analysis of repetitions in rich words still involves some
interesting open problems. We address lower bounds on the repetition threshold
of infinite rich words over 2 and 3-letter alphabets, and construct a candidate
infinite rich word over the alphabet with a small critical
exponent of . This represents the first progress on an open
problem of Vesti from 2017.Comment: 12 page
Maximum Likelihood Estimation in Gaussian Chain Graph Models under the Alternative Markov Property
The AMP Markov property is a recently proposed alternative Markov property
for chain graphs. In the case of continuous variables with a joint multivariate
Gaussian distribution, it is the AMP rather than the earlier introduced LWF
Markov property that is coherent with data-generation by natural
block-recursive regressions. In this paper, we show that maximum likelihood
estimates in Gaussian AMP chain graph models can be obtained by combining
generalized least squares and iterative proportional fitting to an iterative
algorithm. In an appendix, we give useful convergence results for iterative
partial maximization algorithms that apply in particular to the described
algorithm.Comment: 15 pages, article will appear in Scandinavian Journal of Statistic
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