470 research outputs found
Mediterranean Crossbills Loxia curvirostra sensu lato (Aves, Passeriformes): new data and directions for future research
Mediterranean Crossbills are as much differentiated as L. scotica and L. pytyopsittacus. They are sedentary, linked to pine trees
and have evolved a thicker bill to extract the seeds from Pine cones.
Their decolorization could be due to dietary causes. The authors studied
biometrics, breeding phenology, and primary food of Italian popula tions living in Calabria and Etna (Sicily) and compared them with the
other Mediterranean populations. A coevolutive radiation between the
different populations of Mediterranean Crossbills presently living in
the three main peninsulas, adiacent islands and North Africa occurred
separately and this may be demonstrated by their morphometrics, their
sedentariness, as well as by songs and some genetic results recently
published. They conclude that the same criteria followed to raise L.
curvirostra scotica to the species rank as scotica occur also for the dif ferent Mediterranean population
Evidence for a Novel Reaction Mechanism of a Prompt Shock-Induced Fission Following the Fusion of 78Kr and 40Ca Nuclei at E/A =10 MeV
An analysis of experimental data from the inverse-kinematics ISODEC
experiment on 78Kr+40Ca reaction at a bombarding energy of 10 AMeV has revealed
signatures of a hitherto unknown reaction mechanism, intermediate between the
classical damped binary collisions and fusion-fission, but also substantially
different from what is being termed in the literature as fast fission or quasi
fission. These signatures point to a scenario where the system fuses
transiently while virtually equilibrating mass asymmetry and energy and, yet,
keeping part of the energy stored in a collective shock-imparted and, possibly,
angular momentum bearing form of excitation. Subsequently the system fissions
dynamically along the collision or shock axis with the emerging fragments
featuring a broad mass spectrum centered around symmetric fission, relative
velocities somewhat higher along the fission axis than in transverse direction,
and virtually no intrinsic spin. The class of massasymmetric fission events
shows a distinct preference for the more massive fragments to proceed along the
beam direction, a characteristic reminiscent of that reported earlier for
dynamic fragmentation of projectile-like fragments alone and pointing to the
memory of the initial mass and velocity distribution.Comment: 5 PAGES, 6 FIGURE
Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
We report experimental signals of Bose-Einstein condensation in the decay of
hot Ca projectile-like sources produced in mid-peripheral collisions at
sub-Fermi energies. The experimental setup, constituted by the coupling of the
INDRA 4 detector array to the forward angle VAMOS magnetic spectrometer,
allowed us to reconstruct the mass, charge and excitation energy of the
decaying hot projectile-like sources. Furthermore, by means of quantum
fluctuation analysis techniques, temperatures and mean volumes per particle "as
seen by" bosons and fermions separately are correlated to the excitation energy
of the reconstructed system. The obtained results are consistent with the
production of dilute mixed (bosons/fermions) systems, where bosons experience a
smaller volume as compared to the surrounding fermionic gas. Our findings
recall similar phenomena observed in the study of boson condensates in atomic
traps.Comment: Submitted to Phys. Rev. Lett. (december 2014
Correlations between isospin dynamics and Intermediate Mass Fragments emission time scales: a probe for the symmetry energy in asymmetric nuclear matter
We show new data from the Ni+Sn and Ni+Sn
reactions studied in direct kinematics with the CHIMERA detector at INFN-LNS
and compared with the reverse kinematics reactions at the same incident beam
energy (35 A MeV). Analyzing the data with the method of relative velocity
correlations, fragments coming from statistical decay of an excited
projectile-like (PLF) or target-like (TLF) fragments are discriminated from the
ones coming from dynamical emission in the early stages of the reaction. By
comparing data of the reverse kinematics experiment with a stochastic mean
field (SMF) + GEMINI calculations our results show that observables from neck
fragmentation mechanism add valuable constraints on the density dependence of
symmetry energy. An indication is found for a moderately stiff symmetry energy
potential term of EOS.Comment: Talk given by E. De Filippo at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Kinematical coincidence method in transfer reactions
A new method to extract high resolution angular distributions from
kinematical coincidence measurements in binary reactions is presented.
Kinematic is used to extract the center of mass angular distribution from the
measured energy spectrum of light particles. Results obtained in the case of
10Be+p-->9Be+d reaction measured with the CHIMERA detector are shown. An
angular resolution of few degrees in the center of mass is obtained.Comment: 6 Page 10 Figures submitted to Nuclear Instruments and Methods
Dipolar degrees of freedom and Isospin equilibration processes in Heavy Ion collisions
Background: In heavy ion collision at the Fermi energies Isospin
equilibration processes occur- ring when nuclei with different charge/mass
asymmetries interacts have been investigated to get information on the
nucleon-nucleon Iso-vectorial effective interaction. Purpose: In this paper,
for the system 48Ca +27 Al at 40 MeV/nucleon, we investigate on this process by
means of an observable tightly linked to isospin equilibration processes and
sensitive in exclusive way to the dynamical stage of the collision. From the
comparison with dynamical model calculations we want also to obtain information
on the Iso-vectorial effective microscopic interaction. Method: The average
time derivative of the total dipole associated to the relative motion of all
emitted charged particles and fragments has been determined from the measured
charges and velocities by using the 4? multi-detector CHIMERA. The average has
been determined for semi- peripheral collisions and for different charges Zb of
the biggest produced fragment. Experimental evidences collected for the systems
27Al+48Ca and 27Al+40Ca at 40 MeV/nucleon used to support this novel method of
investigation are also discussed.Comment: Submitted for publication on Phys. Rev. C. 0n 24-oct-201
Robust Neutrino Constraints by Combining Low Redshift Observations with the CMB
We illustrate how recently improved low-redshift cosmological measurements
can tighten constraints on neutrino properties. In particular we examine the
impact of the assumed cosmological model on the constraints. We first consider
the new HST H0 = 74.2 +/- 3.6 measurement by Riess et al. (2009) and the
sigma8*(Omegam/0.25)^0.41 = 0.832 +/- 0.033 constraint from Rozo et al. (2009)
derived from the SDSS maxBCG Cluster Catalog. In a Lambda CDM model and when
combined with WMAP5 constraints, these low-redshift measurements constrain sum
mnu<0.4 eV at the 95% confidence level. This bound does not relax when allowing
for the running of the spectral index or for primordial tensor perturbations.
When adding also Supernovae and BAO constraints, we obtain a 95% upper limit of
sum mnu<0.3 eV. We test the sensitivity of the neutrino mass constraint to the
assumed expansion history by both allowing a dark energy equation of state
parameter w to vary, and by studying a model with coupling between dark energy
and dark matter, which allows for variation in w, Omegak, and dark coupling
strength xi. When combining CMB, H0, and the SDSS LRG halo power spectrum from
Reid et al. 2009, we find that in this very general model, sum mnu < 0.51 eV
with 95% confidence. If we allow the number of relativistic species Nrel to
vary in a Lambda CDM model with sum mnu = 0, we find Nrel =
3.76^{+0.63}_{-0.68} (^{+1.38}_{-1.21}) for the 68% and 95% confidence
intervals. We also report prior-independent constraints, which are in excellent
agreement with the Bayesian constraints.Comment: 19 pages, 6 figures, submitted to JCAP; v2: accepted version. Added
section on profile likelihood for Nrel, improved plot
The Parkes Galactic Meridian Survey (PGMS): observations and CMB polarization foreground analysis
We present observations and CMB foreground analysis of the Parkes Galactic
Meridian Survey (PGMS), an investigation of the Galactic latitude behaviour of
the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope.
The survey consists of a 5-deg wide strip along the Galactic meridian l=254-deg
extending from Galactic plane to South Galactic pole. We identify three zones
distinguished by polarized emission properties: the disc, the halo, and a
transition region connecting them. The halo section lies at latitudes |b| >
40-deg and has weak and smooth polarized emission mostly at large scale with
steep angular power spectra of median slope . The
disc region covers the latitudes |b|<20-deg and has a brighter, more complex
emission dominated by the small scales with flatter spectra of median slope
. The transition region has steep spectra as in the
halo, but the emission increases toward the Galactic plane from halo to disc
levels. The change of slope and emission structure at b \sim -20\degr is
sudden, indicating a sharp disc-halo transition. The whole halo section is just
one environment extended over 50-deg with very low emission which, once scaled
to 70GHz, is equivalent to the CMB B-Mode emission for a tensor-to-scalar
perturbation power ratio r_halo = 3.3 +/- 0.4 x 10^{-3}. Applying a
conservative cleaning procedure, we estimate an r detection limit of at 70~GHz (3-sigma C.L.) and, assuming a dust polariztion
fraction <12%, at 150~GHz. The 150-GHz limit
matches the goals of planned sub-orbital experiments, which can therefore be
conducted at this high frequency. The 70-GHz limit is close to the goal of
proposed next generation space missions, which thus might not strictly require
space-based platforms.Comment: 23 pages, 22 Figures. Accepted for publication on MNRAS. Some figures
have been reduced in resolution. Replaced with the accepted version, 3
figures, more details on instrument performances, and map of polarization
spectral index adde
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