95 research outputs found
Genetic differentiation among populations of the threatened Bellevalia webbiana (Asparagaceae) and its consequence on conservation
The narrow central Italian endemic and threatened Webb's hyacinth (Bellevalia webbiana), a perennial herb, is a clear example of a species that has disappeared from several localities due to the de..
Human gastro-intestinal organoid engineering: a state of the art
Gastrointestinal organ failure, from congenital or postnatally acquired pathologies, is a major cause of death across countries of all income levels. Organoids and engineered tissues have been widely investigated as tools to model organ functions and treat pathologies. In this review we aim to describe the progress in human organoid engineering applied to the gastrointestinal tract (namely esophagus, stomach, and intestine). Starting from the onset of the organoid culture technique, we illustrate genetic engineering, stem cell niche engineering, bioprinting, and microfluidics approaches used to integrate mechano-physiological parameters with human organoids. Thanks to these improvements, organoid technology allows disease modelling of patient-specific pathologies, and personalized treatment screening, also offering a cell source for autologous transplantation. We further present an overview of the advances of tissue engineering in animal systems, concerning novel materials and scaffolds to be combined with a variety of cell types to reconstitute a viable surrogate for implantation. The effort in this field sets organoids as an important tool in personalized and regenerative medicine. Their application combined with the advances in tissue engineering holds great potential for translational application
Magnetic Field Amplification and Flat Spectrum Radio Quasars
We perform time-dependent, spatially-resolved simulations of blazar emission
to evaluate several flaring scenarios related to magnetic-field amplification
and enhanced particle acceleration. The code explicitly accounts for
light-travel-time effects and is applied to flares observed in the flat
spectrum radio quasar (FSRQ) PKS 0208-512, which show optical/{\gamma}-ray
correlation at some times, but orphan optical flares at other times. Changes in
both the magnetic field and the particle acceleration efficiency are explored
as causes of flares. Generally, external Compton emission appears to describe
the available data better than a synchrotron self-Compton scenario, and in
particular orphan optical flares are difficult to produce in the SSC framework.
X-ray soft-excesses, {\gamma}-ray spectral hardening, and the detections at
very high energies of certain FSRQs during flares find natural explanations in
the EC scenario with particle acceleration change. Likewise, optical flares
with/without {\gamma}-ray counterparts can be explained by different
allocations of energy between the magnetization and particle acceleration,
which may be related to the orientation of the magnetic field relative to the
jet flow. We also calculate the degree of linear polarization and polarization
angle as a function of time for a jet with helical magnetic field. Tightening
of the magnetic helix immediately downstream of the jet perturbations, where
flares occur, can be sufficient to explain the increases in the degree of
polarization and a rotation by >= 180 degree of the observed polarization
angle, if light-travel-time effects are properly considered.Comment: 12 pages, 9 figures. Accepted for publication in MNRA
SMARTS OPTICAL AND INFRARED MONITORING OF 12 GAMMA-RAY BRIGHT BLAZARS
We present multiwavelength data for 12 blazars observed from 2008 to 2010 as part of an ongoing optical–infrared
photometric monitoring project. Sources were selected to be bright, southern (δ < 20◦) blazars observed by the
Fermi Gamma-Ray Space Telescope. Light curves are presented for the 12 blazars in BVRJK at near-daily cadence.
We find that optical and infrared fluxes are well correlated in all sources. Gamma-ray bright flat spectrum radio
quasars (FSRQs) in our sample have optical/infrared emission correlated with gamma-rays consistent with inverse
Compton-scattering models. In FSRQs, variability amplitude increases toward IR wavelengths, consistent with the
presence of a thermal accretion disk varying on significantly longer timescales than the jet. In BL Lac objects,
variability is mainly constant, or increases toward shorter wavelength. FSRQs have redder optical–infrared colors
when they are brighter,whileBLLac objects showno such trend. Several objects showcomplicated color–magnitude
behavior: AO 0235+164 appears in two different states depending on its gamma-ray intensity. OJ 287 and 3C 279
show some hysteresis tracks in their color–magnitude diagrams. Individual flares may be achromatic or otherwise
depart from the trend, suggesting different jet components becoming important at different times. We present a
time-dependent spectral energy distribution of the bright FSRQ 3C 454.3 during its 2009 December flare, which is
well fit by an external Compton model in the bright state, although day-to-day changes pose challenges to a simple
one-zone model. All data from the SMARTS monitoring program are publicly available on our Web site
Space-time quantum solves three experimental paradoxes
I show that a Planck-scale deformation of the relativistic dispersion
relation, which has been independently considered in the quantum-gravity
literature, can explain the surprising results of three classes of experiments:
(1) observations of cosmic rays above the expected GZK limit, (2) observations
of multi-TeV photons from the BL Lac object Markarian 501, (3) studies of the
longitudinal development of the air showers produced by ultra-high-energy
hadronic particles. Experiments now in preparation, such as the ones planned
for the GLAST space telescope, will provide an independent test of this
solution of the three experimental paradoxes.Comment: LaTex, 9 pages. Typos corrected (in the version submitted yesterday
there was one type in equation and a couple of spelling typos). All aspects
of the analysis remain unchange
Inconsistency in the Standard Model for Thin Accretion Disks
We analyze the configuration of a thin rotating accretion disk, which is
embedded in a magnetic field inducing a backreaction in the gravitating plasma.
The aim of this study is to determine the conditions under which the gaseous
accretion model of Shakura can be reconciled with the magneto-hydrodynamical
picture requested to trigger the underlying turbulent behavior. We focus our
attention to the generalized Ohm equation in order to understand if the plasma
backreaction is able to provide the proper toroidal current, allowing a
non-zero infalling velocity. In the limit of linear plasma backreaction, this
analysis shows how the Shakura profile of accretion turns out to be
inconsistent. In particular, comparing the azimuthal and the generalized Ohm
equilibrium equations, we argue that it is not possible to maintain a constant
rate of accretion. A non-stationary scenario for the disk configuration is then
outlined and it results into a transient process which is however associated to
a vanishing accretion rate.Comment: 7 pages, no figur
Fiasco: a multidetector optimized for semiperipheral heavy ion collisions at Fermi energies
The Fiasco multidetector is a low-threshold apparatus, optimized for the investigation of peripheral to semi-central collisions in heavy ion reactions at Fermi energies. It consists of three types of detectors. The first detector layer is a shell of 24 position-sensitive Parallel Plate Avalanche Detectors (PPADs), covering about 70% of the forward hemisphere, which measure the velocity vectors of the heavy ðZ\10Þ reaction products. Below and around the grazing angle, behind the most forward PPADs, there are 96 DE–E silicon telescopes (with thickness of 200 and 500 mm; respectively); they are mainly used to measure the energy of the projectile-like fragment and to identify its charge and, via the time-of-flight of the PPADs, also its mass. Finally, behind most of the PPADs there are 158 (or 182, depending on the configuration) scintillation detectors, mostly of the phoswich type, which cover 25–30% of the forward hemisphere; they identify both light charged particles ðZ ¼ 1; 2Þ and intermediate mass fragments ð3pZt20Þ; measuring also their time-of-flight. r 2003 Elsevier B.V. All rights reserved
Prognostic immune markers identifying patients with severe COVID-19 who respond to tocilizumab
Introduction: A growing number of evidences suggest that the combination of hyperinflammation, dysregulated T and B cell response and cytokine storm play a major role in the immunopathogenesis of severe COVID-19. IL-6 is one of the main pro-inflammatory cytokines and its levels are increased during SARS-CoV-2 infection. Several observational and randomized studies demonstrated that tocilizumab, an IL-6R blocker, improves survival in critically ill patients both in infectious disease and intensive care units. However, despite transforming the treatment options for COVID-19, IL-6R inhibition is still ineffective in a fraction of patients.
Methods: In the present study, we investigated the impact of two doses of tocilizumab in patients with severe COVID-19 who responded or not to the treatment by analyzing a panel of cytokines, chemokines and other soluble factors, along with the composition of peripheral immune cells, paying a particular attention to T and B lymphocytes.
Results: We observed that, in comparison with non-responders, those who responded to tocilizumab had different levels of several cytokines and different T and B cells proportions before starting therapy. Moreover, in these patients, tocilizumab was further able to modify the landscape of the aforementioned soluble molecules and cellular markers.
Conclusions: We found that tocilizumab has pleiotropic effects and that clinical response to this drug remain heterogenous. Our data suggest that it is possible to identify patients who will respond to treatment and that the administration of tocilizumab is able to restore the immune balance through the re-establishment of different cell populations affected by SARS-COV-2 infection, highlighting the importance of temporal examination of the pathological features from the diagnosis
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