146 research outputs found
Mechanical and chemical spinodal instabilities in finite quantum systems
Self consistent quantum approaches are used to study the instabilities of
finite nuclear systems. The frequencies of multipole density fluctuations are
determined as a function of dilution and temperature, for several isotopes. The
spinodal region of the phase diagrams is determined and it appears that
instabilities are reduced by finite size effects. The role of surface and
volume instabilities is discussed. It is indicated that the important chemical
effects associated with mechanical disruption may lead to isospin
fractionation.Comment: 4 pages, 4 figure
Evidence for Spinodal Decomposition in Nuclear Multifragmentation
Multifragmentation of a ``fused system'' was observed for central collisions
between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products
were well identified thanks to the high performances of the INDRA 4pi array.
Experimental higher-order charge correlations for fragments show a weak but non
ambiguous enhancement of events with nearly equal-sized fragments. Supported by
dynamical calculations in which spinodal decomposition is simulated, this
observed enhancement is interpreted as a ``fossil'' signal of spinodal
instabilities in finite nuclear systems.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Letter
Multifragmentation of a very heavy nuclear system (II): bulk properties and spinodal decomposition
The properties of fragments and light charged particles emitted in
multifragmentation of single sources formed in central 36AMeV Gd+U collisions
are reviewed. Most of the products are isotropically distributed in the
reaction c.m. Fragment kinetic energies reveal the onset of radial collective
energy. A bulk effect is experimentally evidenced from the similarity of the
charge distribution with that from the lighter 32AMeV Xe+Sn system. Spinodal
decomposition of finite nuclear matter exhibits the same property in simulated
central collisions for the two systems, and appears therefore as a possible
mechanism at the origin of multifragmentation in this incident energy domain.Comment: 28 pages including 14 figures; submitted to Nucl. Phys.
Limitaciones de la tomografia axial computada en la localizacion de quistes hidatidicos abdominales en pacientes con confirmacion inmunodiagnostica
Multifragmentation threshold in ^{93}Nb+{nat}Mg collisions at 30 MeV/nucleon
We analyzed the on reaction at 30 MeV/nucleon in the aim
of disentangling binary sequential decay and multifragmentation decay close to
the energy threshold, i.e. MeV/nucleon. Using the backtracing
technique applied to the statistical models GEMINI and SMM we reconstruct
simulated charge, mass and excitation energy distributions and compare them to
the experimental ones. We show that data are better described by SMM than by
GEMINI in agreement with the fact that multifragmentation is responsible for
fragment production at excitation energies around 3 MeV/nucleon.Comment: 16 pages, 12 figures, 5 tables Soumis \`a Nuclear Physics
Fragment size correlations in finite systems - application to nuclear multifragmentation
We present a new method for the calculation of fragment size correlations in
a discrete finite system in which correlations explicitly due to the finite
extent of the system are suppressed. To this end, we introduce a combinatorial
model, which describes the fragmentation of a finite system as a sequence of
independent random emissions of fragments. The sequence is accepted when the
sum of the sizes is equal to the total size. The parameters of the model, which
may be used to calculate all partition probabilities, are the intrinsic
probabilities associated with the fragments. Any fragment size correlation
function can be built by calculating the ratio between the partition
probabilities in the data sample (resulting from an experiment or from a Monte
Carlo simulation) and the 'independent emission' model partition probabilities.
This technique is applied to charge correlations introduced by Moretto and
collaborators. It is shown that the percolation and the nuclear statistical
multifragmentaion model ({\sc smm}) are almost independent emission models
whereas the nuclear spinodal decomposition model ({\sc bob}) shows strong
correlations corresponding to the break-up of the hot dilute nucleus into
nearly equal size fragments
Static and free-vibration analyses of dental prosthesis and atherosclerotic human artery by refined finite element models
Early Diagnosis, Treatment and Follow-Up of Cystic Echinococcosis in Remote Rural Areas in Patagonia: Impact of Ultrasound Training of Non-Specialists
Cystic echinococcosis (CE) is an important and widespread disease that affects sheep, cattle, and humans living in areas where sheep and cattle are raised. CE is highly endemic in rural sections of Rio Negro, Argentina, where our group is based. However, it requires continuous monitoring of both populations with human disease best assessed by means of ultrasound (US) screening. This is challenging in remote rural areas due to the shortage of imaging specialists. To overcome this hurdle, we set up a two-day training program of Focused Assessment with Sonography for Echinococcosis (FASE) on CE for family medicine practitioners with no previous experience in US. After the course, they were equipped with portable US scanners and dispatched to remote rural areas in Rio Negro where they screened patients, located and staged the cysts and decided on the treatment with the help of surgeons and radiologists in local tertiary care centers
Genetic susceptibility to hepatocellular carcinoma in chromosome 22q13.31, findings of a genome-wide association study.
Background and Aim: Chronic hepatitis C virus (HCV) infection, long-term alcohol use, cigarette smoking, and obesity are the major risk factors for hepatocellular carcinoma (HCC) in the United States, but the disease risk varies substantially among individuals with these factors, suggesting host susceptibility to and gene-environment interactions in HCC. To address genetic susceptibility to HCC, we conducted a genome-wide association study (GWAS).
Methods: Two case-control studies on HCC were conducted in the United States. DNA samples were genotyped using the Illumian microarray chip with over 710â000 single nucleotide polymorphisms (SNPs). We compared these SNPs between 705 HCC cases and 1455 population controls for their associations with HCC and verified our findings in additional studies.
Results: In this GWAS, we found that two SNPs were associated with HCC at
Conclusions: SNPs i
Charge correlations and dynamical instabilities in the multifragment emission process
A new, sensitive method allows one to search for the enhancement of events
with nearly equal-sized fragments as predicted by theoretical calculations
based on volume or surface instabilities. Simulations have been performed to
investigate the sensitivity of the procedure. Experimentally, charge
correlations of intermediate mass fragments emitted from heavy ion reactions at
intermediate energies have been studied. No evidence for a preferred breakup
into equal-sized fragments has been found.Comment: 12 pages, TeX type, psfig, submitted to Phys. Rev. Lett, also
available at http://csa5.lbl.gov/moretto/ps/zcor_pp.p
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