719 research outputs found
The Fermi blazars' divide based on the diagnostic of the SEDs peak frequencies
We have studied the quasi-simultaneous Spectral Energy Distributions (SED) of
48 LBAS blazars, detected within the three months of the LAT Bright AGN Sample
(LBAS) data taking period, combining Fermi and Swift data with radio
NIR-Optical and hard-X/gamma-ray data. Using these quasi-simultaneous SEDs,
sampling both the low and the high energy peak of the blazars broad band
emission, we were able to apply a diagnostic tool based on the estimate of the
peak frequencies of the synchrotron (S) and Inverse Compton (IC) components.
Our analysis shows a Fermi blazars' divide based on the peak frequencies of the
SED. The robust result is that the Synchrotron Self Compton (SSC) region
divides in two the plane were we plot the peak frequency of the synchrotron SED
vs the typical Lorentz factor of the electrons most contributing to the
synchrotron emission and to the inverse Compton process. Objects within or
below this region, radiating likely via the SSC process, are
high-frequency-peaked BL Lac object (HBL), or low/intermediate-frequency peaked
BL Lac object (LBL/IBL). All of the IBLs/LBLs within or below the SSC region
are not Compton dominated. The objects lying above the SSC region, radiating
likely via the External radiation Compton (ERC) process, are Flat Spectrum
Radio Quasars and IBLs/LBLs. All of the IBLs/LBLs in the ERC region show a
significant Compton dominance.Comment: Contribution to the Workshop SciNeGHe 2009/Gamma-ray Physics in the
LHC era (Assisi - Italy, Oct. 7-9 2009
Study of microwave/gamma-ray properties for Fermi-LAT bright AGNs
Blazars are a small fraction of all extragalactic sources but, unlike other
objects, they are strong emitters across the entire electromagnetic spectrum.
Recent data in the microwave region of the electromagnetic spectrum have become
available to allow for systematic studies of blazars over large cosmological
volumes. This frequency band is indeed particularly suited for the selection of
blazars since at these frequencies the contamination from radio extended
components with steep spectra is no longer present and the emission from the
accretion process is negligible. During the first 3 months of scientific
operations Fermi-LAT detected 106 bright, high-galactic latitude (| b |> 10
deg) AGNs with high significance. In this study we investigate the possible
relations between the microwave and the gamma-ray emissions for Fermi-LAT
detected AGNs belonging to WMAP 5th year bright source catalog.Comment: 3 pages, 3 ps figures, "2009 Fermi Symposium", "eConf Proceedings
C091122
Towards a new osteometric method for sexing ancient cremated human remains. Analysis of Late Bronze Age and Iron Age samples from Italy with gendered grave goods
Sex estimation of human remains is one of the most important research steps for physical anthropologists and archaeologists dealing with funerary contexts and trying to reconstruct the demographic structure of ancient societies. However, it is well known that in the case of cremations sex assessment might be complicated by the destructive/transformative effect of the fire on bones. Osteometric standards built on unburned human remains and contemporary cremated series are often inadequate for the analysis of ancient cremations, and frequently result in a significant number of misclassifications. This work is an attempt to overcome the scarcity of methods that could be applied to pre-proto-historic Italy and serve as methodological comparison for other European contexts. A set of 24 anatomical traits were measured on 124 Bronze Age and Iron Age cremated individuals with clearly engendered grave goods. Assuming gender largely correlated to sex, male and female distributions of each individual trait measured were compared to evaluate sexual dimorphism through inferential statistics and Chaktaborty and Majumder\u2019s index. The discriminatory power of each variable was evaluated by cross-validation tests. Eight variables yielded an accuracy equal to or greater than 80%. Four of these variables also show a similar degree of precision for both sexes. The most diagnostic measurements are from radius, patella, mandible, talus, femur, first metatarsal, lunate and humerus. Overall, the degree of sexual dimorphism and the reliability of estimates obtained from our series are similar to those of a modern cremated sample recorded by Gon\ue7alves and collaborators. Nevertheless, mean values of the male and female distributions in our case study are lower, and the application of the cut-off point calculated from the modern sample to our ancient individuals produces a considerable number of misclassifications. This result confirms the need to build population-specific methods for sexing the cremated remains of ancient individuals
Gamma-ray Spectral Evolution of NGC1275 Observed with Fermi-LAT
We report on a detailed investigation of the high-energy gamma-ray emission
from NGC\,1275, a well-known radio galaxy hosted by a giant elliptical located
at the center of the nearby Perseus cluster. With the increased photon
statistics, the center of the gamma-ray emitting region is now measured to be
separated by only 0.46' from the nucleus of NGC1275, well within the 95%
confidence error circle with radius ~1.5'. Early Fermi-LAT observations
revealed a significant decade-timescale brightening of NGC1275 at GeV photon
energies, with a flux about seven times higher than the one implied by the
upper limit from previous EGRET observations. With the accumulation of one-year
of Fermi-LAT all-sky-survey exposure, we now detect flux and spectral
variations of this source on month timescales, as reported in this paper. The
average >100 MeV gamma-ray spectrum of NGC1275 shows a possible deviation from
a simple power-law shape, indicating a spectral cut-off around an observed
photon energy of E = 42.2+-19.6 GeV, with an average flux of F = (2.31+-0.13) X
10^{-7} ph/cm^2/s and a power-law photon index, Gamma = 2.13+-0.02. The largest
gamma-ray flaring event was observed in April--May 2009 and was accompanied by
significant spectral variability above E > 1-2 GeV. The gamma-ray activity of
NGC1275 during this flare can be described by a hysteresis behavior in the flux
versus photon index plane. The highest energy photon associated with the
gamma-ray source was detected at the very end of the observation, with the
observed energy of E = 67.4GeV and an angular separation of about 2.4' from the
nucleus. In this paper we present the details of the Fermi-LAT data analysis,
and briefly discuss the implications of the observed gamma-ray spectral
evolution of NGC1275 in the context of gamma-ray blazar sources in general.Comment: 20 pages, 6 figures, accepted for publication in the Ap
Non-Newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm
Permission to redistribute provided by publishers.Three models of different stent designs implanted in a cerebral aneurysm, originating from the Virtual Intracranial Stenting Challenge'07, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the cfd simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified by other groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating wss, to understand dynamic flow effects, and to discriminate more effectively between stent designs. © Authors 2011
A strontium isoscape of Italy for provenance studies
We present a novel database of biological and geological 87Sr/86Sr values (n = 1920) from Italy, using literature data and newly analysed samples, for provenance purposes. We collected both bioavailable and non-bioavailable (i.e. rocks and bulk soils) data to attain a broader view of the Sr isotope variability of the Italian territory. These data were used to build isotope variability maps, namely isoscapes, through Kriging interpolations. We employed two different Kriging models, namely Ordinary Kriging and Universal Kriging, with a geolithological map of Italy categorized in isotope classes as external predictor. Model performances were evaluated through a 10-fold cross validation, yielding accurate 87Sr/86Sr predictions with root mean squared errors (RMSE) ranging between 0.0020 and 0.0024, dependent on the Kriging model and the sample class. Overall, the produced maps highlight a heterogeneous distribution of the 87Sr/86Sr across Italy, with the highest radiogenic values (>0.71) mainly localized in three areas, namely the Alps (Northern Italy), the Tuscany/Latium (Central Italy) and Calabria/Sicily (Southern Italy) magmatic/metamorphic terrains. The rest of the peninsula is characterized by values ranging between 0.707 and 0.710, mostly linked to sedimentary geological units of mixed nature. Finally, we took advantage of the case study of Fratta Polesine, to underscore the importance of choosing appropriate samples when building the local isoscape and of exploring different end-members when interpreting the local Sr isotope variability in mobility and provenance studies. Our user-friendly maps and database are freely accessible through the Geonode platform and will be updated over time to offer a state-of-the-art reference in mobility and provenance studies across the Italian landscape
Tomba celtica della fase di romanizzazione dalla località Casona di Nogara (Verona)
The present paper focuses on a Celtic grave from the Romanization phase in Casona di Nogara (Verona). The grave, partially damaged by agricultural works, represents an important funerary documentation in the Verona plain and is thought to belong to the Cenomani culture. The funeral rite is cremation. Among the gravegoods, there remain the weapons, personal tools and elements from the funeral banquet and symposium. The grave is to be dated to the end of the second century BC and the beginning of the first century BC (LT D1)
A study of childhood febrile convulsions with particular reference to HHV-6 infection: Pathogenic considerations
Most febrile convulsions (FC) in infants occur during a viral infection, particularly in children of less than 3 years of age: human herpesvirus 6 (HHV-6) has an Important pathogenic role. To evaluate the link between this and other viruses and FC, a group of 65 children (mean age 18.46 months: SD+/-9.19) with a first episode of simple FC (G1) was compared with 24 children (mean age 19.29 months, SD+/-13.17) with a febrile syndrome but without FC (G2). Virological study showed the following infections: HHV-6 in 23/65 of G1 and in 12/24 of G2, adenoviruses (ADV) in 9/65 of G1 and in 0/24, of G2, syncytial respiratory virus (SRV) in 3/28 of G1 and in 0/2 of G2. HSV-1 in 6/65 of G1 and in 1/24 of G2, cytomegalovirus (CMV in 2/65 of G1 and in 0/24 of G2 and HHV-7 in 1/42 of GI and in 1/13 of G2. Children in G1, statistically compared with G2, were significantly more Likely to have a family history of FC and circulating granulocytes, while IgM and alpha 2-globulin were less probable. Some cytokines (IL 1 beta, TNF beta and GM-CSF) were found in 24 children in G1 and 12 in G2; no differences were found between the two groups. In the light of our data and of the recent literature, the possibility that the cytokines may act on the nervous system cannot be excluded. Among the HHV-6-infected children, those suf fering from convulsions were statistically more likely to have a family history of FC and ISM, while IgA were less likely. In G1, 57 cases were followed up over 2 years: 9 of them had a second episode of FC. Virological diagnosis at the first episode of FC revealed HHV-6 infection in 3 cases, 2 of these being due to viral reactivation. We underline the important role of HHV-6 infection in FC and postulate a relation ship between family history and the immunity of the patient; this is confirmed by the loss of statistical significance in the reduction of IgM in G1 compared with G2 with no family history of FC. The reactivation of FC by HHV-6 is a possibility to be borne in mind, an increased number of cases would be needed to confirm this hypothesis
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