6,162 research outputs found
BeppoSAX observations of the quasar Markarian 205
We present the first BeppoSAX observation (0.1 to 220 keV) of the quasar Mrk
205. We have searched for the unusual Fe line profile claimed in the XMM-Newton
spectrum which has been widely discussed in recent literature. We find no
evidence for a broad, ionized Fe line component in our data. We detect for the
first time a Compton hump in this object. Besides, when this component is
included in the fit, the line strength diminishes, in agreement with a recent
re-analysis of the XMM-Newton data, but with better constraints on the
reflection component thanks to the PDS instrument (15-220 keV). We interpret
this fact as another indication for illumination of a distant and cold material
rather than reprocessing in the highly ionized inner parts of an accretion
disk. We cannot constrain the presence of a high energy cutoff but we confirm
the existence of a variable soft excess (one year timescale).Comment: 13 pages, 12 figures, accepted for publication in A&
Italian PhD students at the borders: the relationship between family background and international mobility
Abstract Previous literature has suggested that PhD students’ mobility has become a fundamental step during doctoral studies, both for training purposes and for creating transnational research networks. In recent years, there has been a significant increase in migration of highly educated and highly skilled Italians. Most studies concentrate on employment-related characteristics of researchers’ and scientists’ mobility, largely neglecting other topics, such as family background characteristics of those who decide to study and go abroad. Using the Istat Survey on occupational conditions of PhD holders conducted in 2014 and 2018 in Italy, along with modelling using multinomial logistic regression analyses, we aim to investigate the relationship between family background characteristics and mobility during PhD studies according to different types of international stay. Our results show that both parental education and mother’s economic activity are related to the propensity for studying abroad among PhD candidates, whereas father’s social class seems to have a lower impact on this decision. The gap in doctoral mobility among PhD students with respect to socio-economic status seems also to vary according to the different types of stay abroad. Overall, our findings intend to shed light on potential disparities related to studying abroad among PhD students and their links to family background, which may have future repercussions on students’ occupational prospects
Compton reflection in AGN with Simbol-X
AGN exhibit complex hard X-ray spectra. Our current understanding is that the
emission is dominated by inverse Compton processes which take place in the
corona above the accretion disk, and that absorption and reflection in a
distant absorber play a major role. These processes can be directly observed
through the shape of the continuum, the Compton reflection hump around 30 keV,
and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of
Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151,
NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the
simulations with recent observations on these sources by INTEGRAL, Swift and
Suzaku. Constraining reflection models for AGN with Simbol-X will help us to
get a clear view of the processes and geometry near to the central engine in
AGN, and will give insight to which sources are responsible for the Cosmic
X-ray background at energies above 20 keV.Comment: 4 pages, 1 figure, to appear in the proceedings of the second
Simbol-X Symposium "Simbol-X - Focusing on the Hard X-ray Universe", AIP
Conf. Proc. Series, P. Ferrando and J. Rodriguez ed
VITRUV - Science Cases
VITRUV is a second generation spectro-imager for the PRIMA enabled Very Large
Telescope Interferometer. By combining simultaneously up to 8 telescopes VITRUV
makes the VLTI up to 6 times more efficient. This operational gain allows two
novel scientific methodologies: 1) massive surveys of sizes; 2) routine
interferometric imaging. The science cases presented concentrate on the
qualitatively new routine interferometric imaging methodology. The science
cases are not exhaustive but complementary to the PRIMA reference mission. The
focus is on: a) the close environment of young stars probing for the initial
conditions of planet formation and disk evolution; b) the surfaces of stars
tackling dynamos, activity, pulsation, mass-loss and evolution; c) revealing
the origin of the extraordinary morphologies of Planetary Nebulae and related
stars; d) studying the accretion-ejection structures of stellar black-holes
(microquasars) in our galaxy; e) unveiling the different interacting components
(torus, jets, BLRs) of Active Galactic Nuclei; and f) probing the environment
of nearby supermassive black-holes and relativistic effects in the Galactic
Center black-hole.Comment: 15 pages. The Power of Optical/IR Interferometry: Recent Scientific
Results and 2nd Generation VLTI Instrumentation, Allemagne (2005) in pres
Exploring the photometric variability of ultra-cool dwarfs with TESS
We present a photometric characterization of 208 ultra-cool dwarfs (UCDs)
with spectral types between M4 and L4, from 20-second and 2-minute cadence TESS
light curves. We determine rotation periods for 87 objects (42 percent) and
identify 778 flare events in 103 UCDs (49.5 percent). For 777 flaring events
(corresponding to 102 objects), we derive bolometric energies between 2.1e30
and 1.1e34 erg , with 56 superflare events. No transiting planets or eclipsing
binaries were identified. We find that the fraction of UCDs with rotation and
flaring activity is, at least, 20 percent higher in M4-M6 spectral types than
in later UCDs (M7-L4). For spectral types between M4 and L0, we measure the
slope of the flare bolometric energy-duration correlation to be gamma = 0.497
+/- 0.058, which agrees with that found in previous studies for solar-type and
M dwarfs. Moreover, we determine the slope of the flare frequency distribution
to be alpha = -1.75 +/- 0.04 for M4-M5 dwarfs, alpha = -1.69 +/- 0.04 and alpha
= -1.72 +/- 0.1 for M6-M7 and M8-L0 dwarfs, respectively, which are consistent
with previous works that exclusively analysed UCDs. These results support the
idea that independently of the physical mechanisms that produce magnetic
activity, the characteristics of the rotational modulation and flares are
similar for both fully-convective UCDs and partially-convective solar-type and
early-M stars. Based on the measured UCD flare distributions, we find that UV
radiation emitted from flares does not have the potential to start prebiotic
chemistry.Comment: Accepted for publication in MNRAS, 16 pages, 12 figure
Innate immune activating ligand SUMOylation affects tumor cell recognition by NK cells
Natural Killer cells are innate lymphocytes involved in tumor immunosurveillance. They express activating receptors able to recognize self-molecules poorly expressed on healthy cells but up-regulated upon stress conditions, including transformation. Regulation of ligand expression in tumor cells mainly relays on transcriptional mechanisms, while the involvement of ubiquitin or ubiquitin-like modifiers remains largely unexplored. Here, we focused on the SUMO pathway and demonstrated that the ligand of DNAM1 activating receptor, PVR, undergoes SUMOylation in multiple myeloma. Concurrently, we found that PVR is preferentially located in intracellular compartments in human multiple myeloma cell lines and malignant plasma cells and that inhibition of the SUMO pathway promotes its translocation to the cell surface, increasing tumor cell susceptibility to NK cell-mediated cytolysis. Our findings provide the first evidence of an innate immune activating ligand regulated by SUMOylation, and confer to this modification a novel role in impairing recognition and killing of tumor cells.Natural Killer cells are innate lymphocytes involved in tumor immunosurveillance. They express activating receptors able to recognize self-molecules poorly expressed on healthy cells but up-regulated upon stress conditions, including transformation. Regulation of ligand expression in tumor cells mainly relays on transcriptional mechanisms, while the involvement of ubiquitin or ubiquitin-like modifiers remains largely unexplored. Here, we focused on the SUMO pathway and demonstrated that the ligand of DNAM1 activating receptor, PVR, undergoes SUMOylation in multiple myeloma. Concurrently, we found that PVR is preferentially located in intracellular compartments in human multiple myeloma cell lines and malignant plasma cells and that inhibition of the SUMO pathway promotes its translocation to the cell surface, increasing tumor cell susceptibility to NK cell-mediated cytolysis. Our findings provide the first evidence of an innate immune activating ligand regulated by SUMOylation, and confer to this modification a novel role in impairing recognition and killing of tumor cells
Experimental results of crystal-assisted slow extraction at the SPS
The possibility of extracting highly energetic particles from the Super
Proton Synchrotron (SPS) by means of silicon bent crystals has been explored
since the 1990's. The channelling effect of a bent crystal can be used to
strongly deflect primary protons and eject them from the synchrotron. Many
studies and experiments have been carried out to investigate crystal
channelling effects. The extraction of 120 and 270 GeV proton beams has already
been demonstrated in the SPS with dedicated experiments located in the ring.
Presently in the SPS, the UA9 experiment is performing studies to evaluate the
possibility to use bent silicon crystals to steer particle beams in high energy
accelerators. Recent studies on the feasibility of extraction from the SPS have
been made using the UA9 infrastructure with a longer-term view of using
crystals to help mitigate slow extraction induced activation of the SPS. In
this paper, the possibility to eject particles into the extraction channel in
LSS2 using the bent crystals already installed in the SPS is presented. Details
of the concept, simulations and measurements carried out with beam are
presented, before the outlook for the future is discussed.Comment: 4 pages, 7 figures, submitted to to International Particle
Accelerator Conference (IPAC) 2017 in Copenhagen, Denmar
Review of health-related quality of life data in multiple myeloma patients treated with novel agents
In multiple myeloma (MM), health-related quality of life (HRQoL) data is becoming increasingly important, owing to improved survival outcomes and the impact of treatment-related toxicity on HRQoL. Researchers are more frequently including HRQoL assessments in clinical trials, but analysis and reporting of this data has not been consistent. A systematic literature review assessed the effect of novel agents (thalidomide, bortezomib and lenalidomide) on HRQoL in MM patients, and evaluated the subsequent reporting of these HRQoL results. A relatively small body of literature addresses HRQoL data in MM patients treated with novel MM therapeutic agents: 9 manuscripts and 15 conference proceedings. The literature demonstrates the complementary value of HRQoL when assessing clinical response, progression, overall survival and toxicity. However, weaknesses and inconsistencies in analysis and presentation of HRQoL data were observed, often complicating interpretation of the impact of treatment on HRQoL in MM. Further evaluation of HRQoL in MM patients treated with novel agents is required in larger cohorts, and ideally in head-to-head comparative studies. Additionally, the development of standardised MM-specific best practice guidelines in HRQoL data collection and analysis is recommended. These would ensure that future data are more useful in guiding predictive models and clinical decisions
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