1,221 research outputs found
Tagaeri Taromenane: popoli incontattati dell\u2019Amazzonia Ecuadoriana ed espansione della frontiera petrolifera, quali territori per l\u2019autodeterminazione e i diritti umani?
Nel 1999 l\u2019Ecuador, primo paese al mondo, istituiva una zona Intangibile riservata al diritto all\u2019autodeterminazione dei popoli incontattati Tagaeri-
Taromenane. Nel 2007 la Zona Intangibile Tagaeri-Taromenane (ZITT) veniva finalmente delimitata occupando un\u2019area di 7500 km2 della regione amazzonica
ai confini con il Peru, perpetuamente vietata ad ogni attivit\ue0 industriale.
Contemporaneamente veniva istituita anche una buffer zone di 10 km per garantire una ulteriore area di rispetto. Tuttavia trattandosi di popolazioni
nomadi che per secoli si sono mosse su un\u2019area di circa 20.000 km2 tra i fiumi Napo e Curaray (in direzione Nord sud) e tra i primi rilievi andini e la
confluenza del Nashino con il Curaray (in direzione ovest est) la Zona Intangibile non risulta adeguata alla territorialit\ue0 Tagaeri-Taromenane.
Accanto alla mobilit\ue0 dei popoli in isolamento si assiste alla mobilit\ue0 della frontiera petrolifera. Il lavoro utilizza il ruolo della scala (cartografica e
geografica) e le sue implicazioni cognitive per osservare ci\uf2 che sta accadendo attorno, vicino e all'interno della zona intangibile, da una visione continentale
al dettaglio della sua storia e della sua istituzione.
Gli strumenti cartografici e geografici ci aiutano a visualizzare l\u2019oggi e immaginare il domani, sapendo che il destino di questo angolo dell'Amazzonia
non \ue8 necessariamente definito: si tratta di una regione ad alta complessit\ue0 territoriale con la possibilit\ue0 di articolare una rete tra aree protette, territori
indigeni e corridoi ecologici culturali, alla ricerca di percorsi alternativi di sviluppo locale
AGN heating, thermal conduction and Sunyaev-Zeldovich effect in galaxy groups and clusters
(abridged) We investigate in detail the role of active galactic nuclei on the
physical state of the gas in galaxy groups and clusters, and the implications
for anisotropy in the CMB from Sunyaev-Zeldovich effect. We include the effect
of thermal conduction, and find that the resulting profiles of temperature and
entropy are consistent with observations. Unlike previously proposed models,
our model predicts that isentropic cores are not an inevitable consequence of
preheating. The model also reproduces the observational trend for the density
profiles to flatten in lower mass systems. We deduce the energy E_agn required
to explain the entropy observations as a function of mass of groups and
clusters M_cl and show that E_agn is proportional to M_cl^alpha with alpha~1.5.
We demonstrate that the entropy measurements, in conjunction with our model,
can be translated into constraints on the cluster--black hole mass relation.
The inferred relation is nonlinear and has the form M_bh\propto M_cl^alpha.
This scaling is an analog and extension of a similar relation between the black
hole mass and the galactic halo mass that holds on smaller scales. We show that
the central decrement of the CMB temperature is reduced due to the enhanced
entropy of the ICM, and that the decrement predicted from the plausible range
of energy input from the AGN is consistent with available data of SZ decrement.
We show that AGN heating, combined with the observational constraints on
entropy, leads to suppression of higher multipole moments in the angular power
spectrum and we find that this effect is stronger than previously thought.Comment: accepted for publication in The Astrophysical Journa
Dual-domain reporter approach for multiplex identification of major SARS-CoV-2 variants of concern in a microarray-based assay
: Since the emergence of the COVID-19 pandemic in December 2019, the SARS-CoV-2 virus continues to evolve into many variants emerging around the world. To enable regular surveillance and timely adjustments in public health interventions, it is of the utmost importance to accurately monitor and track the distribution of variants as rapidly as possible. Genome sequencing is the gold standard for monitoring the evolution of the virus, but it is not cost-effective, rapid and easily accessible. We have developed a microarray-based assay that can distinguish known viral variants present in clinical samples by simultaneously detecting mutations in the Spike protein gene. In this method, the viral nucleic acid, extracted from nasopharyngeal swabs, after RT-PCR, hybridizes in solution with specific dual-domain oligonucleotide reporters. The domains complementary to the Spike protein gene sequence encompassing the mutation form hybrids in solution that are directed by the second domain ("barcode" domain) at specific locations on coated silicon chips. The method utilizes characteristic fluorescence signatures to unequivocally differentiate, in a single assay, different known SARS-CoV-2 variants. In the nasopharyngeal swabs of patients, this multiplex system was able to genotype the variants which have caused waves of infections worldwide, reported by the WHO as being of concern (VOCs), namely Alpha, Beta, Gamma, Delta and Omicron variants
Dual black holes in merger remnants. I: linking accretion to dynamics
We study the orbital evolution and accretion history of massive black hole
(MBH) pairs in rotationally supported circumnuclear discs up to the point where
MBHs form binary systems. Our simulations have high resolution in mass and
space which, for the first time, makes it feasible to follow the orbital decay
of a MBH either counter- or co-rotating with respect to the circumnuclear disc.
We show that a moving MBH on an initially counter-rotating orbit experiences an
"orbital angular momentum flip" due to the gas-dynamical friction, i.e., it
starts to corotate with the disc before a MBH binary forms. We stress that this
effect can only be captured in very high resolution simulations. Given the
extremely large number of gas particles used, the dynamical range is
sufficiently large to resolve the Bondi-Hoyle-Lyttleton radii of individual
MBHs. As a consequence, we are able to link the accretion processes to the
orbital evolution of the MBH pairs. We predict that the accretion rate is
significantly suppressed and extremely variable when the MBH is moving on a
retrograde orbit. It is only after the orbital angular momentum flip has taken
place that the secondary rapidly "lights up" at which point both MBHs can
accrete near the Eddington rate for a few Myr. The separation of the double
nucleus is expected to be around ~10 pc at this stage. We show that the
accretion rate can be highly variable also when the MBH is co-rotating with the
disc (albeit to a lesser extent) provided that its orbit is eccentric. Our
results have significant consequences for the expected number of observable
double AGNs at separations of <100 pc.Comment: 8 pages, 4 figures, revised version accepted to MNRA
Non-thermal Processes in Black-Hole-Jet Magnetospheres
The environs of supermassive black holes are among the universe's most
extreme phenomena. Understanding the physical processes occurring in the
vicinity of black holes may provide the key to answer a number of fundamental
astrophysical questions including the detectability of strong gravity effects,
the formation and propagation of relativistic jets, the origin of the highest
energy gamma-rays and cosmic-rays, and the nature and evolution of the central
engine in Active Galactic Nuclei (AGN). As a step towards this direction, this
paper reviews some of the progress achieved in the field based on observations
in the very high energy domain. It particularly focuses on non-thermal particle
acceleration and emission processes that may occur in the rotating
magnetospheres originating from accreting, supermassive black hole systems.
Topics covered include direct electric field acceleration in the black hole's
magnetosphere, ultra-high energy cosmic ray production, Blandford-Znajek
mechanism, centrifugal acceleration and magnetic reconnection, along with the
relevant efficiency constraints imposed by interactions with matter, radiation
and fields. By way of application, a detailed discussion of well-known sources
(Sgr A*; Cen A; M87; NGC1399) is presented.Comment: invited review for International Journal of Modern Physics D, 49
pages, 15 figures; minor typos corrected to match published versio
Moving frames applied to shell elasticity
Exterior calculus and moving frames are used to describe curved elastic
shells. The kinematics follow from the Lie-derivative on forms whereas the
dynamics via stress-forms.Comment: 20 pages, 1 figur
Ionized gas and stellar kinematics of seventeen nearby spiral galaxies
Ionized gas and stellar kinematics have been measured along the major axes of
seventeen nearby spiral galaxies of intermediate to late morphological type. We
discuss the properties of each sample galaxy distinguishing between those
characterized by regular or peculiar kinematics. In most of the observed
galaxies ionized gas rotates more rapidly than stars and have a lower velocity
dispersion, as is to be expected if the gas is confined in the disc and
supported by rotation while the stars are mostly supported by dynamical
pressure. In a few objects, gas and stars show almost the same rotational
velocity and low velocity dispersion, suggesting that their motion is dominated
by rotation.
Incorporating the spiral galaxies studied by Bertola et al. (1996), Corsini
et al. (1999, 2003) and Vega Beltran et al. (2001) we have compiled a sample of
50 S0/a-Scd galaxies, for which the major-axis kinematics of the ionized gas
and stars have been obtained with the same spatial (~1'') and spectral
(~50km/s) resolution, and measured with the same analysis techniques. This
allowed us to address the frequency of counterrotation in spiral galaxies. It
turns out that less than 12% and less than 8% (at the 95% confidence level) of
the sample galaxies host a counterrotating gaseous and stellar disc,
respectively. The comparison with S0 galaxies suggests that the retrograde
acquisition of small amounts of external gas gives rise to counterrotating
gaseous discs only in gas-poor S0s, while in gas-rich spirals the newly
acquired gas is swept away by the pre-existing gas. Counterrotating gaseous and
stellar discs in spirals are formed only from the retrograde acquisition of
large amounts of gas exceeding that of pre-existing gas, and subsequent star
formation, respectively.Comment: 14 pages, 33 figures, A&A accepte
Correlations Between Central Massive Objects And Their Host Galaxies: From Bulgeless Spirals to Ellipticals
Recent observations by Ferrarese et al. (2006) and Wehner et al. (2006)
reveal that a majority of galaxies contain a central massive object (CMO),
either a supermassive black hole (SMBH) or a compact stellar nucleus,
regardless of the galaxy mass or morphological type, and that there is a tight
relation between the masses of CMOs and those of the host galaxies. Several
recent studies show that feedback from black holes can successfully explain the
\msigma correlation in massive elliptical galaxies that contain SMBHs.
However, puzzles remain in spirals or dwarf spheroids that do not appear to
have black holes but instead harbor a compact central stellar cluster. Here we
use three-dimensional, smoothed particle hydrodynamics simulations of isolated
galaxies to study the formation and evolution of CMOs in bulgeless disk
galaxies, and simulations of merging galaxies to study the transition of the
CMO--host mass relation from late-type bulgeless spirals to early-type
ellipticals. Our results suggest that the observed correlations may be
established primarily by the depletion of gas in the central region by
accretion and star-formation, and may hold for all galaxy types. A systematic
search for CMOs in the nuclei of bulgeless disk galaxies would offer a test of
this conclusion. (Abridged)Comment: 11 pages, 8 figures, accepted to Ap
A log-quadratic relation for predicting supermassive black hole masses from the host bulge Sersic index
We reinvestigate the correlation between black hole mass and bulge
concentration. With an increased galaxy sample, updated estimates of galaxy
distances, black hole masses, and Sersic indices `n' - a measure of
concentration - we perform a least-squares regression analysis to obtain a
relation suitable for the purpose of predicting black hole masses in other
galaxies. In addition to the linear relation, log(M_bh) = 7.81(+/-0.08) +
2.69(+/-0.28)[log(n/3)] with epsilon_(intrin)=0.31 dex, we investigated the
possibility of a higher order M_bh-n relation, finding the second order term in
the best-fitting quadratic relation to be inconsistent with a value of zero at
greater than the 99.99% confidence level. The optimal relation is given by
log(M_bh) = 7.98(+/-0.09) + 3.70(+/-0.46)[log(n/3)] -
3.10(+/-0.84)[log(n/3)]^2, with epsilon_(intrin)=0.18 dex and a total absolute
scatter of 0.31 dex. Extrapolating the quadratic relation, it predicts black
holes with masses of ~10^3 M_sun in n=0.5 dwarf elliptical galaxies, compared
to ~10^5 M_sun from the linear relation, and an upper bound on the largest
black hole masses in the local universe, equal to 1.2^{+2.6}_{-0.4}x10^9
M_sun}. In addition, we show that the nuclear star clusters at the centers of
low-luminosity elliptical galaxies follow an extrapolation of the same
quadratic relation. Moreover, we speculate that the merger of two such
nucleated galaxies, accompanied by the merger and runaway collision of their
central star clusters, may result in the late-time formation of some
supermassive black holes. Finally, we predict the existence of, and provide
equations for, a relation between M_bh and the central surface brightness of
the host bulge
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