699 research outputs found
H.E.S.S. deeper observations on SNR RX J0852.0-4622
Supernova Remnants (SNRs) are believed to be acceleration sites of Galactic
cosmic rays. Therefore, deep studies of these objects are instrumental for an
understanding of the high energy processes in our Galaxy. RX J0852.0-4622, also
known as Vela Junior, is one of the few (4) shell-type SNRs resolved at Very
High Energies (VHE; E > 100 GeV). It is one of the largest known VHE sources (~
1.0 deg radius) and its flux level is comparable to the flux level of the Crab
Nebula in the same energy band. These characteristics allow for a detailed
analysis, shedding further light on the high-energy processes taking place in
the remnant. In this document we present further details on the spatial and
spectral morphology derived with an extended data set. The analysis of the
spectral morphology of the remnant is compatible with a constant power-law
photon index of 2.11 +/- 0.05_stat +/- 0.20_syst from the whole SNR in the
energy range from 0.5 TeV to 7 TeV. The analysis of the spatial morphology
shows an enhanced emission towards the direction of the pulsar PSR J0855-4644,
however as the pulsar is lying on the rim of the SNR, it is difficult to
disentangle both contributions. Therefore, assuming a point source, the upper
limit on the flux of the pulsar wind nebula (PWN) between 1 TeV and 10 TeV, is
estimated to be ~ 2% of the Crab Nebula flux in the same energy range
HESS J1507-622: an unique unidentified source off the Galactic Plane
Galactic very high energy (VHE, > 100 GeV) gamma ray sources in the inner
Galaxy H.E.S.S. survey tend to cluster within 1 degree in latitude around the
Galactic plane. HESS J1507-622 instead is unique, since it is located at
latitude of ~3.5 degrees. HESS J1507-622 is slightly extended over the PSF of
the instrument and hence its Galactic origin is clear. The search for
counterparts in other wavelength regimes (radio, infrared and X-rays) failed to
show any plausible counterparts; and given its position off the Galactic plane
and hence the absorption almost one order of magnitude lower, it is very
surprising to not see any counterparts especially at X-rays wavelengths (by
ROSAT, XMM Newton and Chandra). Its latitude implies that it is either rather
close, within about 1 kpc, or is located well off the Galactic plane. And also
the models reflect the uniqueness of this object: a leptonic PWN scenario would
place this source due to its quite small extension to multi-kpc distance
whereas a hadronic scenario would preferentially locate this object at
distances of < 1 kpc where the density of target material is higher
Self-propelled particles with fluctuating speed and direction of motion
We study general aspects of active motion with fluctuations in the speed and
the direction of motion in two dimensions. We consider the case in which
fluctuations in the speed are not correlated to fluctuations in the direction
of motion, and assume that both processes can be described by independent
characteristic time-scales. We show the occurrence of a complex transient that
can exhibit a series of alternating regimes of motion, for two different
angular dynamics which correspond to persistent and directed random walks. We
also show additive corrections to the diffusion coefficient. The characteristic
time-scales are also exposed in the velocity autocorrelation, which is a sum of
exponential forms.Comment: to appear in Phys. Rev. Let
H.E.S.S. observations of the Large Magellanic Cloud
The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way at a
distance of approximately 48 kpc. Despite its distance it harbours several
interesting targets for TeV gamma-ray observations. The composite supernova
remnant N 157B/PSR J05367-6910 was discovered by H.E.S.S. being an emitter of
very high energy (VHE) gamma-rays. It is the most distant pulsar wind nebula
ever detected in VHE gamma-rays. Another very exciting target is SN 1987A, the
remnant of the most recent supernova explosion that occurred in the
neighbourhood of the Milky Way. Models for Cosmic Ray acceleration in this
remnant predict gamma-ray emission at a level detectable by H.E.S.S. but this
has not been detected so far. Fermi/LAT discovered diffuse high energy (HE)
gamma-ray emission from the general direction of the massive star forming
region 30 Doradus but no clear evidence for emission from either N 157B or SN
1987A has been published. The part of the LMC containing these objects has been
observed regularly with the H.E.S.S. telescopes since 2003. With deep
observations carried out in 2010 a very good exposure of this part of the sky
has been obtained. The current status of the H.E.S.S. LMC observations is
reported along with new results on N 157B and SN 1987A.Comment: 4 pages, 3 figures, proceedings of the 32nd Internatioal Cosmic Ray
Conference, Beijing 201
Immunohistochemical Markers in the Assessment of Tumor Response
The examination of the possibility of using immunohistochemical and molecular (NCRT) and prognostic factors of the disease state. The study included 21 patients with locally advanced gastric cancer. All patients underwent the NCRT followed by gastrectomy D2. We analyzed the expression of HER2 / neu marker, Ki-67, p53, Cyklin D1, E-cadherin in biopsy (before therapy) and the operating material (after chemoradiotherapy and the treatment gap). We have found statistically significant decrease in the expression of Ki-67 markers and Cyklin D1, a trend towards to a decrease of p53 expression after the NCRT. The dynamics of expression of immunohistochemical markers examination is a promising approach in search for predictors of NCRT effectiveness for patients with locally advanced gastric cancer.
Keywords: neoadjuvant chemoradiotherapy, immunohistochemical markers, molecular genetic markers, therapeutic pathomorphism, gastric cancer
Pulsar Wind Nebula candidates recently discovered by H.E.S.S
H.E.S.S. is currently the most sensitive instrument in the very-high-energy
gamma-ray domain and has revealed many new sources along the Galactic Plane, a
significant fraction of which seems to be associated with energetic pulsars.
HESS J1825-137 and Vela X are considered to be the prototypes of such sources
in which the large VHE nebula results from the whole history of the pulsar wind
and the supernova remnant host, both evolving in a complex interstellar medium.
These nebulae are seen to be offset from the pulsar position and, for HESS
J1825-137, a spectral steepening at increasing distance from the pulsar has
been measured. In this context, updated H.E.S.S. results on two previously
published sources, namely HESS J1809-193 and HESS J1912+101, and preliminary
results on the newly discovered HESS J1356-645, are presented. These extended
VHE sources are thought to be associated with the energetic pulsars PSR
J1809-1917, PSR J1913+1011 and PSR J1357-6429, respectively. Properties of each
source in the VHE regime, together with those measured in the radio and X-ray
domains, are discussed.Comment: 4 pages, 6 figures, Submitted to Proceedings of "4th Heidelberg
International Symposium on High Energy Gamma-Ray Astronomy 2008
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