2,769 research outputs found
Transport properties of ybco thin films near the critical state with no applied field
Transport measurements carried out on twinned ybco films are compared to the
predictions of a previously proposed model suggesting that the vortices move
along the films twin boundaries that behave as rows of Josephson weak links
[P.Bernstein and J.F.Hamet, J.Appl.Phys.95 (2004) 2569]. The obtained results
suggest that, except if the films are very thin, the twin boundaries consist of
superimposed rows of weak links with mean height,ds, whose mean length along
the TBs is an universal function of T/Tc, the reduced temperature. This
conclusion yields a general expression for the critical surface current density
of the films as a function of T/Tc and of the number of superimposed weak links
rows, while the critical current density depends on ds. A comparison of the
measurements reported by various authors shows that the nature of the substrate
and the growth technique have both a strong effect on ds . The existence of
superimposed weak links rows is attributed to extended defects generated by
y2o3 inclusions.Comment: 33 pages, 13 figures; accepted for publication in Physica
Developmental disturbances associated with agenesis of the permanent maxillary lateral incisor
The aim of this study was to characterise the intra and extra-oral phenotype associated with agenesis of the permanent maxillary lateral incisor. We compared three groups: (1) subjects with agenesis of one or both permanent maxillary lateral incisors (n=80); (2) first and second degree relatives of group 1 with no agenesis of the permanent maxillary lateral incisor and (3) subjects with no agenesis of the maxillary lateral incisor or family history of it (n=49). For each of the 201 subjects detailed clinical information was reviewed and panoramic radiographs were analysed. Considering only the sample with unilateral agenesis, microdontia of the contralateral permanent maxillary lateral incisor was significantly more frequent in group 1 (82.4%) than in group 2 (25%) and the control group (2%). This supports the theory that microdontia is a variable expression of the same developmental disturbance that causes tooth agenesis. The absence of third molars occurred more often in group 1 (36.2%) than in groups 2 and 3 (18.6% and 18.9% respectively), confirming that agenesis of third molars was markedly associated with the agenesis of the permanent maxillary lateral incisor. Agenesis of teeth other than third molars was not significantly different among subjects with agenesis of the permanent maxillary lateral incisor and their relatives. The frequencies of supernumerary teeth, permanent maxillary canine impaction, general health condition and minor anomalies were not significantly different between the three groups
Fermi observations of TeV-selected AGN
We report on observations of TeV-selected AGN made during the first 5.5
months of observations with the Large Area Telescope (LAT) on-board the Fermi
Gamma-ray Space Telescope (Fermi). In total, 96 AGN were selected for study,
each being either (i) a source detected at TeV energies (28 sources) or (ii) an
object that has been studied with TeV instruments and for which an upper-limit
has been reported (68 objects). The Fermi observations show clear detections of
38 of these TeV-selected objects, of which 21 are joint GeV-TeV sources and 29
were not in the third EGRET catalog. For each of the 38 Fermi-detected sources,
spectra and light curves are presented. Most can be described with a power law
of spectral index harder than 2.0, with a spectral break generally required to
accommodate the TeV measurements. Based on an extrapolation of the Fermi
spectrum, we identify sources, not previously detected at TeV energies, which
are promising targets for TeV instruments. Evidence for systematic evolution of
the -ray spectrum with redshift is presented and discussed in the
context of interaction with the EBL.Comment: 51 pages, 6 figures, accepted for The Astronomical Journa
Fermi LAT Search for Photon Lines from 30 to 200 GeV and Dark Matter Implications
Dark matter (DM) particle annihilation or decay can produce monochromatic
-rays readily distinguishable from astrophysical sources. -ray
line limits from 30 GeV to 200 GeV obtained from 11 months of Fermi Large Area
Space Telescope data from 20-300 GeV are presented using a selection based on
requirements for a -ray line analysis, and integrated over most of the
sky. We obtain -ray line flux upper limits in the range , and give corresponding DM annihilation
cross-section and decay lifetime limits. Theoretical implications are briefly
discussed.Comment: 6 pages, 1 figure. Accepted for publication by The Physical Review
Letter
A Search for Jet Handedness in Hadronic Decays
We have searched for signatures of polarization in hadronic jets from decays using the ``jet handedness'' method. The polar angle
asymmetry induced by the high SLC electron-beam polarization was used to
separate quark jets from antiquark jets, expected to be left- and
right-polarized, respectively. We find no evidence for jet handedness in our
global sample or in a sample of light quark jets and we set upper limits at the
95% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing
power of the method proposed by Efremov {\it et al.}Comment: Revtex, 8 pages, 2 figure
Effects of hypodontia on craniofacial structures and mandibular growth pattern
Introduction
This study was performed to examine craniofacial structures in persons with hypodontia and to reveal any differences, that may occur, when agenetic teeth are only found in the maxilla, the mandible or in both jaws. The groups consistent of 50 children (33 girls, 17 boys) aged between 9 and 13.5 years were analyzed and assigned to three subgroups. Group 1= upper jaw hypodontia. Group 2= lower jaw hypodontia. Group 3= hypodontia in both jaws.
Material and methods
Eleven angular and three index measurements from lateral encephalographs and two linear measurements from dental blaster casts were calculated. All data was statistically analyzed, parameters with p<5% were investigated for each subgroup respectively.
Results
In comparison with standards the study group showed bimaxillary retrognathism and a reduction of the lower anterior facial height. Moreover both overbite and overjet significantly increased. Other values laid within the normal ranges. Evaluating results of the subgroups, differences in the means of SNA, SNB and overjet between the groups were observed. Analysis of the mandibular growth pattern revealed, that neither vertical nor horizontal patterns are dominant in hypodontia patients.
Conclusions
In certain dentofacial parameters differences between persons with hypodontia and such with full dentition exist. According to our findings agenetic teeth may have a negative influence on the saggital development of a jaw and the lower face and may be responsible for increased overbites. This should receive attention in orthodontic treatment of hypodontia patients
Fermi/LAT discovery of gamma-ray emission from a relativistic jet in the narrow-line quasar PMN J0948+0022
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi
Gamma-ray Space Telescope of high-energy gamma-ray emission from the peculiar
quasar PMN J0948+0022 (z=0.5846). The optical spectrum of this object exhibits
rather narrow Hbeta (FWHM(Hbeta) ~ 1500 km s^-1), weak forbidden lines and is
therefore classified as a narrow-line type I quasar. This class of objects is
thought to have relatively small black hole mass and to accrete at high
Eddington ratio. The radio loudness and variability of the compact radio core
indicates the presence of a relativistic jet. Quasi simultaneous
radio-optical-X-ray and gamma-ray observations are presented. Both radio and
gamma-ray emission (observed over 5-months) are strongly variable. The
simultaneous optical and X-ray data from Swift show a blue continuum attributed
to the accretion disk and a hard X-ray spectrum attributed to the jet. The
resulting broad band spectral energy distribution (SED) and, in particular, the
gamma-ray spectrum measured by Fermi are similar to those of more powerful
FSRQ. A comparison of the radio and gamma-ray characteristics of PMN J0948+0022
with the other blazars detected by LAT shows that this source has a relatively
low radio and gamma-ray power, with respect to other FSRQ. The physical
parameters obtained from modelling the SED also fall at the low power end of
the FSRQ parameter region discussed in Celotti & Ghisellini (2008). We suggest
that the similarity of the SED of PMN J0948+0022 to that of more massive and
more powerful quasars can be understood in a scenario in which the SED
properties depend on the Eddington ratio rather than on the absolute power.Comment: 10 pages, 5 figures, accepted for publication on ApJ Main Journal.
Corresponding author: L. Foschin
Fermi LAT Observation of Diffuse Gamma-Rays Produced Through Interactions between Local Interstellar Matter and High Energy Cosmic Rays
Observations by the Large Area Telescope (LAT) on the \textit{Fermi} mission
of diffuse -rays in a mid-latitude region in the third quadrant
(Galactic longitude from 200\arcdeg to 260\arcdeg and latitude
from 22\arcdeg to 60\arcdeg) are reported. The region contains no known
large molecular cloud and most of the atomic hydrogen is within 1 kpc of the
solar system. The contributions of -ray point sources and inverse
Compton scattering are estimated and subtracted. The residual -ray
intensity exhibits a linear correlation with the atomic gas column density in
energy from 100 MeV to 10 GeV. The measured integrated -ray emissivity
is (1.63 \pm 0.05) \times 10^{-26} {\rm photons s^{-1} sr^{-1}
H\mathchar`-atom^{-1}} and (0.66 \pm 0.02) \times 10^{-26} {\rm photons
s^{-1} sr^{-1} H\mathchar`-atom^{-1}} above 100 MeV and above 300 MeV,
respectively, with additional systematic error of . The differential
emissivity in 100 MeV--10 GeV agrees with calculations based on cosmic ray
spectra consistent with those directly measured, at the 10% level. The results
obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar
system in regions studied are close to the local interstellar spectra inferred
from direct measurements at the Earth within .Comment: accepted for publication in the Astrophysical Journal. Revised
according to the author proof.(correction of typos and minor revisions
Fermi-LAT observations of the exceptional gamma-ray outbursts of 3C 273 in September 2009
We present the light curves and spectral data of two exceptionally luminous
gamma-ray outburts observed by the Large Area Telescope (LAT) experiment on
board Fermi Gamma-ray Space Telescope from 3C 273 in September 2009. During
these flares, having a duration of a few days, the source reached its highest
gamma-ray flux ever measured. This allowed us to study in some details their
spectral and temporal structures. The rise and decay are asymmetric on
timescales of 6 hours, and the spectral index was significantly harder during
the flares than during the preceding 11 months. We also found that short, very
intense flares put out the same time-integrated energy as long, less intense
flares like that observed in August 2009.Comment: Corresponding authors: E. Massaro, [email protected]; G.
Tosti, [email protected]. 15 pages, 4 figures, published in The
Astrophysical Journal Letters, Volume 714, Issue 1, pp. L73-L78 (2010
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