96 research outputs found
Painting dark matter halos with galaxies in mock samples for future surveys
In this thesis we present a completely empirical workflow that produces, from the outputs of a dark matter cosmological simulation, a galaxy mock catalog which is able to reproduce with accuracy a number of physical properties of galaxies such as stellar masses, star-formation rates, observed photometry, emission lines and sizes. The main goal of this thesis is to provide to the scientific community a galaxy mock catalog useful, as mentioned above, to make predictions for future surveys, to plan future observations, to understand and minimize uncertainties and to study systematics and selection effects
Quiescent galaxies at : observations vs. models
The presence of massive quiescent galaxies at high redshifts is still a
challenge for most models of galaxy formation. The aim of this work is to
compare the observed number density and properties of these galaxies with the
predictions of state-of-the-art models. The sample of massive quiescent
galaxies has been selected from the COSMOS2015 photometric catalogue with
, and
. The photometric SEDs of the selected
galaxies have been thoroughly analyzed based on different stellar population
synthesis models. The final sample includes only those galaxies qualified as
quiescent in all SED fitting runs. The observed properties have been compared
to theoretical models: the number density of quiescent galaxies with is reproduced by some models, although there is a
large scatter in their predictions. Instead, very massive
are underpredicted by most of the current
models of galaxy formation: some of them, built on the CARNage simulation, are
consistent with data up to , while at higher redshifts the volume of
the considered simulation is too small to find such rare objects. Simulated
galaxies which match the observed properties in the plane
at have been analyzed by reconstructing their evolutionary paths:
their merger trees suggest that AGN feedback could be the key process allowing
for a rapid quenching of the star formation at and that its
treatment should be improved in models.Comment: Accepted for publication in ApJL, 9 pages, 6 figure
Aceruloplasminemia: A Severe Neurodegenerative Disorder Deserving an Early Diagnosis
Aceruloplasminemia (ACP) is a rare, adult-onset, autosomal recessive disorder, characterized by systemic iron overload due to mutations in the Ceruloplasmin gene (CP), which in turn lead to absence or strong reduction of CP activity. CP is a ferroxidase that plays a key role in iron export from various cells, especially in the brain, where it maintains the appropriate iron homeostasis with neuroprotective effects. Brain iron accumulation makes ACP unique among systemic iron overload syndromes, e.g., various types of genetic hemochromatosis. The main clinical features of fully expressed ACP include diabetes, retinopathy, liver disease, and progressive neurological symptoms reflecting iron deposition in target organs. However, biochemical signs of the disease, namely a mild anemia mimicking iron deficiency anemia because of microcytosis and low transferrin saturation, but with "paradoxical" hyperferritinemia, usually precedes the onset of clinical symptoms of many years and sometimes decades. Prompt diagnosis and therapy are crucial to prevent neurological complications of the disease, as they are usually irreversible once established. In this mini-review we discuss some major issues about this rare disorder, pointing out the early clues to the right diagnosis, instrumental to reduce significant disability burden of affected patients
Massive and old quiescent galaxies at high redshift
Massive quiescent galaxies at high redshift can shed light on the processes
of galaxy mass assembly and quenching of the star formation at early epochs. We
present observer-frame color-color diagrams designed to identify candidate
quiescent galaxies from z=2.5 up to the highest redshifts, that can be then be
selected for spectroscopic follow-up observations. The application to the
COSMOS2015 catalog shows that, after refining the selection with SED fitting,
the number of massive old quiescent galaxies exceeds the forecast of
state-of-the-art semi-analytic models, pointing out the need of an improvement
of the implemented quenching mechanisms at high redshifts.Comment: Astronomy & Astrophysics, accepted; Matching version in press; 21
pages, 13 figure
The stellar-to-halo mass relation over the past 12 Gyr
Understanding how galaxy properties are linked to the dark matter halos they
reside in, and how they co-evolve is a powerful tool to constrain the processes
related to galaxy formation. The stellar-to-halo mass relation (SHMR) and its
evolution over the history of the Universe provides insights on galaxy
formation models and allows to assign galaxy masses to halos in N-body dark
matter simulations. We use a statistical approach to link the observed galaxy
stellar mass functions on the COSMOS field to dark matter halo mass functions
from the DUSTGRAIN simulation and from a theoretical parametrization from z=0
to z=4. We also propose an empirical model to describe the evolution of the
stellar-to-halo mass relation as a function of redshift. We calculate the
star-formation efficiency (SFE) of galaxies and compare results with previous
works and semi-analytical models.Comment: accepted for publication in A&A, matching version in pres
Hyperferritinemia and diagnosis of type 1 Gaucher disease
Given the difficulties in diagnosis of type 1 GD in adults because of disease heterogeneity and lack of awareness, appropriate diagnostic algorithms or flow-charts starting from non-specific findings may help. Case reports help to establish the usefulness of our proposed flowchart in patients presenting with \u201cunexplained hyperferritinemia\u201d
Red Blood Cell Morphologic Abnormalities in Patients Hospitalized for COVID-19
Peripheral blood smear is a simple laboratory tool, which remains of invaluable help for diagnosing primary and secondary abnormalities of blood cells despite advances in automated and molecular techniques. Red blood cells (RBCs) abnormalities are known to occur in many viral infections, typically in the form of mild normo-microcytic anemia. While several hematological alterations at automated complete blood count (including neutrophilia, lymphopenia, and increased red cell distribution width—RDW) have been consistently associated with severity of COVID-19, there is scarce information on RBCs morphological abnormalities, mainly as case-reports or small series of patients, which are hardly comparable due to heterogeneity in sampling times and definition of illness severity. We report here a systematic evaluation of RBCs morphology at peripheral blood smear in COVID-19 patients within the first 72 h from hospital admission. One hundred and fifteen patients were included, with detailed collection of other clinical variables and follow-up. A certain degree of abnormalities in RBCs morphology was observed in 75 (65%) patients. Heterogenous alterations were noted, with spiculated cells being the more frequent morphology. The group with >10% RBCs abnormalities had more consistent lymphopenia and thrombocytopenia compared to those without abnormalities or <10% RBCs abnormalities (p < 0.018, and p < 0.021, respectively), thus underpinning a possible association with an overall more sustained immune-inflammatory “stress” hematopoiesis. Follow-up analysis showed a different mortality rate across groups, with the highest rate in those with more frequent RBCs morphological alterations compared to those with <10% or no abnormalities (41.9%, vs. 20.5%, vs. 12.5%, respectively, p = 0.012). Despite the inherent limitations of such simple association, our results point out towards further studies on erythropoiesis alterations in the pathophysiology of COVID-19
IL-17A impairs host tolerance during airway chronic infection by Pseudomonas aeruginosa
Resistance and tolerance mechanisms participate to the interplay between host and pathogens. IL-17-mediated response has been shown to be crucial for host resistance to respiratory infections, whereas its role in host tolerance during chronic airway colonization is still unclear. Here, we investigated whether IL-17-mediated response modulates mechanisms of host tolerance during airways chronic infection by P. aeruginosa. First, we found that IL-17A levels were sustained in mice at both early and advanced stages of P. aeruginosa chronic infection and confirmed these observations in human respiratory samples from cystic fibrosis patients infected by P. aeruginosa. Using IL-17a(-/-) or IL-17ra(-/-) mice, we found that the deficiency of IL-17A/IL-17RA axis was associated with: i) increased incidence of chronic infection and bacterial burden, indicating its role in the host resistance to P. aeruginosa; ii) reduced cytokine levels (KC), tissue innate immune cells and markers of tissue damage (pro-MMP-9, elastin degradation, TGF-β1), proving alteration of host tolerance. Blockade of IL-17A activity by a monoclonal antibody, started when chronic infection is established, did not alter host resistance but increased tolerance. In conclusion, this study identifies IL-17-mediated response as a negative regulator of host tolerance during P. aeruginosa chronic airway infection
Weakness of accelerator bounds on electron superluminality without a preferred frame
The reference laboratory bounds on superluminality of the electron are
obtained from the absence of in-vacuo Cherenkov processes and the
determinations of synchrotron radiated power for LEP electrons. It is usually
assumed that these analyses establish the validity of a standard
special-relativistic description of the electron with accuracy of at least a
few parts in , and in particular this is used to exclude electron
superluminality with such an accuracy. We observe that these bounds rely
crucially on the availability of a preferred frame. In-vacuo-Cherenkov
processes are automatically forbidden in any theory with "deformed Lorentz
symmetry", relativistic theories that, while different from Special Relativity,
preserve the relativity of inertial frames. Determinations of the synchrotron
radiated power can be used to constrain the possibility of Lorentz-symmetry
deformation, but provide rather weak bounds, which in particular for electron
superluminality we establish to afford us no more constraining power than for
an accuracy of a few parts in . We argue that this observation can have
only a limited role in the ongoing effort of analysis of the anomaly
tentatively reported by the OPERA collaboration, but we stress that it could
provide a valuable case study for assessing the limitations of "indirect" tests
of fundamental laws of physics.Comment: LaTex, 6 page
Geographical heterogeneity of clinical and serological phenotypes of systemic sclerosis observed at tertiary referral centres. The experience of the Italian SIR-SPRING registry and review of the world literature
Introduction: Systemic sclerosis (SSc) is characterized by a complex etiopathogenesis encompassing both host genetic and environmental -infectious/toxic- factors responsible for altered fibrogenesis and diffuse microangiopathy. A wide spectrum of clinical phenotypes may be observed in patients' populations from different geographical areas. We investigated the prevalence of specific clinical and serological phenotypes in patients with definite SSc enrolled at tertiary referral centres in different Italian geographical macro-areas. The observed findings were compared with those reported in the world literature.Materials and methods: The clinical features of 1538 patients (161 M, 10.5%; mean age 59.8 +/- 26.9 yrs.; mean disease duration 8.9 +/- 7.7 yrs) with definite SSc recruited in 38 tertiary referral centres of the SPRING (Systemic sclerosis Progression INvestiGation Group) registry promoted by Italian Society of Rheumatology (SIR) were obtained and clustered according to Italian geographical macroareas.Results: Patients living in Southern Italy were characterized by more severe clinical and/or serological SSc phenotypes compared to those in Northern and Central Italy; namely, they show increased percentages of diffuse cutaneous SSc, digital ulcers, sicca syndrome, muscle involvement, arthritis, cardiopulmonary symptoms, interstitial lung involvement at HRCT, as well increased prevalence of serum anti-Scl70 autoantibodies. In the same SSc population immunusppressive drugs were frequently employed. The review of the literature underlined the geographical heterogeneity of SSc phenotypes, even if the observed findings are scarcely comparable due to the variability of methodological approaches.Conclusion: The phenotypical differences among SSc patients' subgroups from Italian macro-areas might be correlated to genetic/environmental co-factors, and possibly to a not equally distributed national network of information and healthcare facilities
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