211 research outputs found
X-ray analysis of the accreting supermassive black hole in the radio galaxy PKS 2251+11
We investigate the dichotomy between jetted and non-jetted Active Galactic
Nuclei (AGNs), focusing on the fundamental differences of these two classes in
the accretion physics onto the central supermassive black hole (SMBH). Our aim
is to study and constrain the structure, kinematics and physical state of the
nuclear environment in the Broad Line Radio Galaxy (BLRG) PKS 2251+11. The high
X-ray luminosity and the relative proximity make such AGN an ideal candidate
for a detailed analysis of the accretion regions in radio galaxies. We
performed a spectral and timing analysis of a 64 ks observation of PKS
2251+11 in the X-ray band with XMM-Newton. We modeled the spectrum considering
an absorbed power law superimposed to a reflection component. We performed a
time-resolved spectral analysis to search for variability of the X-ray flux and
of the individual spectral components. We found that the power law has a photon
index , absorbed by an ionized partial covering medium with
a column density cm, a ionization
parameter erg s cm and a covering factor
. Considering a density of the absorber typical of the Broad Line
Region (BLR), its distance from the central SMBH is of the order of
pc. An Fe K emission line is found at 6.4 keV, whose intensity shows
variability on time scales of hours. We derived that the reflecting material is
located at a distance , where is the Schwarzschild
radius. Concerning the X-ray properties, we found that PKS 2251+11 does not
differ significantly from the non-jetted AGNs, confirming the validity of the
unified model in describing the inner regions around the central SMBH, but the
lack of information regarding the state of the very innermost disk and SMBH
spin still leave unconstrained the origin of the jet
Surface disinfections: present and future
The propagation of antibiotic resistance increases the chances of major infections for patients during hospitalization and the spread of health related diseases. Therefore finding new and effective solutions to prevent the proliferation of pathogenic microorganisms is critical, in order to protect hospital environment, such as the surfaces of biomedical devices. Modern nanotechnology has proven to be an effective countermeasure to tackle the threat of infections. On this note, recent scientific breakthroughs have demonstrated that antimicrobial nanomaterials are effective in preventing pathogens from developing resistance. Despite the ability to destroy a great deal of bacteria and control the outbreak of infections, nanomaterials present many other advantages. Moreover, it is unlikely for nanomaterials to develop resistance due to their multiple and simultaneous bactericidal mechanisms. In recent years, science has explored more complex antimicrobial coatings and nanomaterials based on graphene have shown great potential in antibacterial treatment. The purpose of this article is to deepen the discussion on the threat of infections related to surface disinfection and to assess the state of the art and potential solutions, with specific focus on disinfection procedures using nanomaterials
Subcellular localization of the five members of the human steroid 5α-reductase family
In humans the steroid 5a-reductase (SRD5A) family comprises five integral membrane enzymes that carry out reduction of a double bond in
lipidic substrates: D4-3-keto steroids, polyprenol and trans-enoyl CoA. The best-characterized reaction is the conversion of testosterone into the
more potent dihydrotestosterone carried out by SRD5A1-2. Some controversy exists on their possible nuclear or endoplasmic reticulum
localization.
We report the cloning and transient expression in HeLa cells of the five members of the human steroid 5a-reductase family as both N- and Cterminus
green fluorescent protein tagged protein constructs. Following the intrinsic fluorescence of the tag, we have determined that the
subcellular localization of these enzymes is in the endoplasmic reticulum, upon expression in HeLa cells. The presence of the tag at either end of
the polypeptide chain can affect protein expression and, in the case of trans enoyl-CoA reductase, it induces the formation of protein aggregates
Probing the Large Faraday Rotation Measure Environment of Compact Active Galactic Nuclei
Knowing how the ambient medium in the vicinity of active galactic nuclei (AGNs) is shaped is crucial to understanding generally the evolution of such cosmic giants as well as AGN jet formation and launching. Thanks to the new broadband capability now available at the Jansky Very Large Array (JVLA), we can study changes in polarization properties, fractional polarization, and polarization angles, together with the total intensity spectra of a sample of 14 AGNs, within a frequency range from 1 to 12 GHz. Depolarization modeling has been performed by means of so-called "qu-fitting" to the polarized data, and a synchrotron self absorption model has been used for fitting to the total intensity data. We found complex behavior both in the polarization spectra and in the total intensity spectra, and several Faraday components with a large rotation measure (RM) and several synchrotron components were needed to represent these spectra. Here, results for three targets are shown. This new method of analyzing broadband polarization data through qu-fitting successfully maps the complex surroundings of unresolved objects
Lettura paesaggistica degli interventi strutturali nel settore vitivinicolo: una proposta metodologica
Searching for the radio remnants of short duration gamma-ray bursts
Neutron star mergers produce a substantial amount of fast-moving ejecta,
expanding outwardly for years after the merger. The interaction of these ejecta
with the surrounding medium may produce a weak isotropic radio remnant,
detectable in relatively nearby events. We use late-time radio observations of
short duration gamma-ray bursts (sGRBs) to constrain this model. Two samples of
events were studied: four sGRBs that are possibly in the local (<200 Mpc)
universe were selected to constrain the remnant non-thermal emission from the
sub-relativistic ejecta, whereas 17 sGRBs at cosmological distances were used
to constrain the presence of a proto-magnetar central engine, possibly
re-energezing the merger ejecta. We consider the case of GRB~170817A/GW170817,
and find that in this case the early radio emission may be quenched by the jet
blast-wave. In all cases, for ejecta mass range of M_ej \lesssim 10^{-2} (5 *
10^{-2}) M_sun, we can rule out very energetic merger ejecta E_ej \gtrsim 5 *
10^{52}(10^{53}) erg, thus excluding the presence of a powerful magnetar as a
merger remnant.Comment: 13 pages, 8 figures, 3 tables. Submitted to MNRA
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