251 research outputs found
Evidence of Critical Behavior in the Disassembly of Nuclei with A ~ 36
A wide variety of observables indicate that maximal fluctuations in the
disassembly of hot nuclei with A ~ 36 occur at an excitation energy of 5.6 +-
0.5 MeV/u and temperature of 8.3 +- 0.5 MeV. Associated with this point of
maximal fluctuations are a number of quantitative indicators of apparent
critical behavior. The associated caloric curve does not appear to show a
flattening such as that seen for heavier systems. This suggests that, in
contrast to similar signals seen for liquid-gas transitions in heavier nuclei,
the observed behavior in these very light nuclei is associated with a
transition much closer to the critical point.Comment: v2: Major changes, new model calculations, new figure
Towards the critical behavior for the light nuclei by NIMROD detector
The critical behavior for the light nuclei with A has been
investigated experimentally by the NIMROD multi-detectors. The wide variety of
observables indicate the critical point has been reached in the disassembly of
hot nuclei at an excitation energy of 5.60.5 MeV/u.Comment: 4 pages, 2 figures; Proceeding of 18th Nuclear Physics Division
Conference of the Euro. Phys. Society (NPDC18) "Phase transitions in strongly
interacting matter", Prague, 23.8.-29.8. 2004. To be published in Nuclear
Physics
Critical Behavior in Light Nuclear Systems: Experimental Aspects
An extensive experimental survey of the features of the disassembly of a
small quasi-projectile system with 36, produced in the reactions of 47
MeV/nucleon Ar + Al, Ti and Ni, has been carried
out. Nuclei in the excitation energy range of 1-9 MeV/u have been investigated
employing a new method to reconstruct the quasi-projectile source. At an
excitation energy 5.6 MeV/nucleon many observables indicate the presence
of maximal fluctuations in the de-excitation processes. The fragment
topological structure shows that the rank sorted fragments obey Zipf's law at
the point of largest fluctuations providing another indication of a liquid gas
phase transition. The caloric curve for this system shows a monotonic increase
of temperature with excitation energy and no apparent plateau. The temperature
at the point of maximal fluctuations is MeV. Taking this
temperature as the critical temperature and employing the caloric curve
information we have extracted the critical exponents , and
from the data. Their values are also consistent with the values of the
universality class of the liquid gas phase transition. Taken together, this
body of evidence strongly suggests a phase change in an equilibrated mesoscopic
system at, or extremely close to, the critical point.Comment: Physical Review C, in press; some discussions about the validity of
excitation energy in peripheral collisions have been added; 24 pages and 32
figures; longer abstract in the preprin
Tracing the Evolution of Temperature in Near Fermi Energy Heavy Ion Collisions
The kinetic energy variation of emitted light clusters has been employed as a
clock to explore the time evolution of the temperature for thermalizing
composite systems produced in the reactions of 26A, 35A and 47A MeV Zn
with Ni, Mo and Au. For each system investigated, the
double isotope ratio temperature curve exhibits a high maximum apparent
temperature, in the range of 10-25 MeV, at high ejectile velocity. These
maximum values increase with increasing projectile energy and decrease with
increasing target mass. The time at which the maximum in the temperature curve
is reached ranges from 80 to 130 fm/c after contact. For each different target,
the subsequent cooling curves for all three projectile energies are quite
similar. Temperatures comparable to those of limiting temperature systematics
are reached 30 to 40 fm/c after the times corresponding to the maxima, at a
time when AMD-V transport model calculations predict entry into the final
evaporative or fragmentation stage of de-excitation of the hot composite
systems. Evidence for the establishment of thermal and chemical equilibrium is
discussed.Comment: 9 pages, 5 figure
A Ghoshal-like Test of Equilibration in Near-Fermi-Energy Heavy Ion Collisions
Calorimetric and coalescence techniques have been employed to probe
equilibration for hot nuclei produced in heavy ion collisions of 35 to 55 MeV/u
projectiles with medium mass targets. Entrance channel mass asymmetries and
energies were selected in order that very hot composite nuclei of similar mass
and excitation would remain after early stage pre-equilibrium particle
emission. Inter-comparison of the properties and de-excitation patterns for
these different systems provides evidence for the production of hot nuclei with
decay patterns relatively independent of the specific entrance channel.Comment: 7 pages, 2 figure
Properties of the Initial Participant Matter Interaction Zone in Near Fermi-Energy Heavy Ion Collisions
The sizes, temperatures and free neutron to proton ratios of the initial
interaction zones produced in the collisions of 40 MeV/nucleon Ar +
Sn and 55 MeV/nucleonAl + Sn are derived using total
detected neutron plus charged particle multiplicity as a measure of the impact
parameter range and number of participant nucleons. The size of the initial
interaction zone, determined from a coalescence model analysis, increases
significantly with decreasing impact parameter. The temperatures and free
neutron to proton ratios in the interaction zones are relatively similar for
different impact parameter ranges and evolve in a similar fashion.Comment: 7 pages, 8 figure
Epigenetic inactivation of the splicing RNA-binding protein CELF2 in human breast cancer
Altres ajuts: This work was co-finaced by the European Development Regional Fund, "A way to achieve Europe" ERDF; the Cellex Foundation; and "la Caixa" Banking Foundation (LCF/PR/PR15/ 11100003).Human tumors show altered patterns of protein isoforms that can be related to the dysregulation of messenger RNA alternative splicing also observed in transformed cells. Although somatic mutations in core spliceosome components and their associated factors have been described in some cases, almost nothing is known about the contribution of distorted epigenetic patterns to aberrant splicing. Herein, we show that the splicing RNA-binding protein CELF2 is targeted by promoter hypermethylation-associated transcriptional silencing in human cancer. Focusing on the context of breast cancer, we also demonstrate that CELF2 restoration has growth-inhibitory effects and that its epigenetic loss induces an aberrant downstream pattern of alternative splicing, affecting key genes in breast cancer biology such as the autophagy factor ULK1 and the apoptotic protein CARD10. Furthermore, the presence of CELF2 hypermethylation in the clinical setting is associated with shorter overall survival of the breast cancer patients carrying this epigenetic lesion
Identification and validation of common molecular targets of hydroxytyrosol
Hydroxytyrosol (HT) is involved in healthful activities and is beneficial to lipid metabolism. Many investigations focused on finding tissue-specific targets of HT through the use of different omics approaches such as transcriptomics and proteomics. However, it is not clear which (if any) of the potential molecular targets of HT reported in different studies are concurrently affected in various tissues. Following the bioinformatic analyses of publicly available data from a selection of in vivo studies involving HT-supplementation, we selected differentially expressed lipid metabolism-related genes and proteins common to more than one study, for validation in rodent liver samples from the entire selection. Four miRNAs (miR-802-5p, miR-423-3p, miR-30a-5p, and miR-146b-5p) responded to HT supplementation. Of note, miR-802-5p was commonly regulated in the liver and intestine. Our premise was that, in an organ crucial for lipid metabolism such as the liver, consistent modulation should be found for a specific target of HT even if different doses and duration of HT supplementation were used in vivo. Even though our results show inconsistency regarding differentially expressed lipid metabolism-related genes and proteins across studies, we found Fgf21 and Rora as potential novel targets of HT. Omics approaches should be fine-tuned to better exploit the available databases
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