34 research outputs found
What Can be Learned Studying the Distribution of the Biggest Fragment ?
In the canonical formalism of statistical physics, a signature of a first
order phase transition for finite systems is the bimodal distribution of an
order parameter. Previous thermodynamical studies of nuclear sources produced
in heavy-ion collisions provide information which support the existence of a
phase transition in those finite nuclear systems. Some results suggest that the
observable Z1 (charge of the biggest fragment) can be considered as a reliable
order parameter of the transition. This talk will show how from peripheral
collisions studied with the INDRA detector at GSI we can obtain this bimodal
behaviour of Z1. Getting rid of the entrance channel effects and under the
constraint of an equiprobable distribution of excitation energy (E*), we use
the canonical description of a phase transition to link this bimodal behaviour
with the residual convexity of the entropy. Theoretical (with and without phase
transition) and experimental Z1-E* correlations are compared. This comparison
allows us to rule out the case without transition. Moreover that quantitative
comparison provides us with information about the coexistence region in the
Z1-E* plane which is in good agreement with that obtained with the signal of
abnormal uctuations of configurational energy (microcanonical negative heat
capacity).Comment: 8 page
Vuorovaikutteisen suunnittelun haasteet ja mahdollisuudet metsÀtalouden vesiensuojelussa
Rapport de l'expertise scientifique collectiveLes animaux peuvent-ils Ă©prouver des Ă©motions, peuvent-ils penser, ont-ils une histoire de vie ? Depuis lâAntiquitĂ©, les philosophes ont proposĂ© des rĂ©ponses contrastĂ©es Ă ces questions. Du XIXĂšme siĂšcle Ă nos jours, la rĂ©flexion sur ce que sont les animaux sâest enrichie dâapports scientifiques : thĂ©orie de lâĂ©volution, Ă©thologie, neurophysiologie, sciences cognitives. Mais la conscience animale reste toujours lâobjet de dĂ©bats importants dans la communautĂ© scientifique. Ainsi en 2012 un groupe de scientifiques de premier plan a Ă©prouvĂ© la nĂ©cessitĂ© de publier un manifeste intitulĂ© « DĂ©claration de Cambridge sur la Conscience », qui Ă©nonce quâ«âŠune convergence de preuves indique que les animaux non humains disposent des substrats neuro-anatomiques, neurochimiques et neurophysiologiques des Ă©tats conscients ainsi que la capacitĂ© dâexprimer des comportements intentionnels...».Les connaissances actuelles, dont cette expertise collective propose une synthĂšse, montrent que les animaux possĂšdent un large Ă©ventail de capacitĂ©s cognitives associĂ©es Ă des comportements plus ou moins complexes. Les formes de conscience Ă©tudiĂ©es chez les humains supposent des capacitĂ©s cognitives distinctes que lâon retrouve chez certains animaux. Peut-on en postuler que ceux-ci ont des formes de consciences Ă©quivalentes Ă celles de lâhomme, sans ĂȘtre forcĂ©ment identiques ?LâĂ©tude des niveaux et des contenus de la conscience chez les animaux est en passe de devenir un enjeu scientifique important en raison de la complexitĂ© du sujet et des controverses quâil ne manquera pas de susciter. Enfin, les acquis scientifiques dans ce domaine invitent Ă reprendre les rĂ©flexions morales concernant les relations que les hommes entretiennent avec les animaux (et particuliĂšrement avec les animaux domestiques
FAZIA and INDRA at GANIL: Status and First Results
International audienceFAZIA and INDRA at GANIL: Status and First Result
Phase transition dynamics in hot nuclei and N/Z influence
An abnormal production of events with almost equal-sized fragments was theoretically proposed as a signature of spinodal instabilities responsible for nuclear multifragmentation in the Fermi energy domain. On the other hand finite size effects are predicted to strongly reduce this extra production. High statistics quasifusion hot nuclei produced in central collisions between Xe and Sn isotopes at 32 and 45 MeV per nucleon incident energies have been used to definitively establish, through the experimental measurement of charge correlations, the presence of spinodal instabilities. N/Z influence was also studied. The nature of the phase transition dynamics i.e. the fragment formation was the last missing piece of the puzzle concerning the liquidgas transition in nuclei
Phase transition dynamics in hot nuclei and N/Z influence
International audienceAn abnormal production of events with almost equal-sized fragments was theoretically proposed as a signature of spinodal instabilities responsible for nuclear multifragmentation in the Fermi energy domain. On the other hand finite size effects are predicted to strongly reduce this extra production. High statistics quasifusion hot nuclei produced in central collisions between Xe and Sn isotopes at 32 and 45 MeV per nucleon incident energies have been used to definitively establish, through the experimental measurement of charge correlations, the presence of spinodal instabilities. N/Z influence was also studied. The nature of the phase transition dynamics i.e. the fragment formation was the last missing piece of the puzzle concerning the liquidgas transition in nuclei
Supplemental Data from "Contribution of MALDI-TOF Mass Spectrometry and Machine Learning Including Deep Learning Techniques for the Detection of Virulence Factors of Clostridioides difficile Strains"
Supplemental Data from "Contribution of MALDI-TOF Mass Spectrometry and Machine Learning Including Deep Learning Techniques for the Detection of Virulence Factors of Clostridioides difficile Strains"
This includes :
Table S1: Caracteristics of the Clostridioides difficile strains used in this study according to PCR-ribotypes (PR)
Table S2: Performances of the Machine Learning(ML)-based pipelines (each pipline has been evaluatd 10 times)
Table S3: statistical comparison of the Kappa coefficient metrics according to the Machine Learning algorithms used in this studyby using the unilateral Wilcoxon signed rank test, with Benjamini-Hochberg correction
Table S4: Performances of the Machine-Learning based classifiers on the âTest datasetâ for the detection ToxA-B-, ToxA+B+CDT, ToxA+B+CDT+ and ToxA+B+CDT+Hv strains
Table S5: statistical comparison of the Kappa coefficient metric according to the resampling methods used in this study by using the unilateral Wilcoxon signed rank test, with Benjamini-Hochberg correctio
Temperature and Density Conditions for Alpha Clustering in Excited Self-Conjugate Nuclei
International audienceStarting from experimental studies on alpha-clustering in excited self-conjugate nuclei (from 16O to 28Si), temperature and density conditions for such a clustering are determined. Measured temperatures have been found in the range of 5.5â6.0 MeV, whereas density values of 0.3â0.4 times the saturation density are deduced, i.e., 0.046 to 0.062 fmâ3. Such a density domain is also predicted by constrained self-consistent mean field calculations. These results constitute a benchmark for alpha clustering from self-conjugate nuclei in relation to descriptions of stellar evolution and supernovae
Low-density in-medium effects on light clusters from heavy-ion data
International audienceThe modification of the ground state properties of light atomic nuclei in the nuclear and stellar medium is addressed, using chemical equilibrium constants evaluated from a new analysis of the intermediate energy heavy-ion (Xe+Sn) collision data measured by the INDRA Collaboration. Three different reactions are considered, mainly differing by the isotopic content of the emission source. The thermodynamic conditions of the data samples are extracted from the measured multiplicities allowing for a parametrization of the in-medium modification, determined with the single hypothesis that the different nuclear species in a given sample correspond to a unique common value for the density of the expanding source. We show that this correction, which was not considered in previous analyses of chemical constants from heavy-ion collisions, is necessary, since the observables of the analyzed systems show strong deviations from the expected results for an ideal gas of free clusters. This dataset is further compared to a relativistic mean-field model, and seen to be reasonably compatible with a universal correction of the attractive Ï-meson coupling
Improved method for the experimental determination of in-medium effects from heavy-ion collisions
International audienceThe equation of state with light clusters for nuclear and stellar matter is determined using chemical equilibrium constants evaluated from the analysis of the recently published (Xe + Sn) heavy ion data, corresponding to three reactions with different isotopic contents of the emission source. The measured multiplicities are used to extract the thermodynamic properties, and an in-medium correction to the ideal gas internal partition function of the clusters is included in the analysis. This in-medium correction and its respective uncertainty are calculated via a Bayesian analysis, with the unique hypothesis that the different nuclear species in a given sample must correspond to a unique common value for the density of the expanding source. Different parameter sets for the correction are tested, and the effect of the radius of the clusters on the thermodynamics and on the chemical equilibrium constants is also addressed. It is shown that the equilibrium constants obtained are almost independent of the isospin content of the analysed systems. Finally, a comparison with a relativistic mean field model proves that data are consistent with a universal in-medium correction of the scalar Ï-meson coupling for nucleons bound in clusters. The obtained value, , is larger than that obtained in a previous study not including in-medium effects in the data analysis. This result implies a smaller effect on the binding energy of the clusters and, as a consequence, larger melting densities, and an increased cluster contribution in supernova matter
Isoscaling in Dilute Warm Nuclear Systems
International audienceHeavy-ion collisions are a good tool to explore hot nuclear matter below saturation density. It has been established that if a nuclear system reaches the thermal and chemical equilibrium, this leads to scaling properties in the isotope production when comparing two systems which differ in proton fraction. This article presents a study of the isoscaling properties of an expanding gas source exploring different thermodynamic states (density, temperature, proton fraction). This experimental work highlights the existence of an isoscaling relationship for hydrogen and 3He, 4He helium isotopes which agrees with the hypothesis of thermal and chemical equilibrium. Moreover, this work reveals the limitations of isoscaling when the two systems differ slightly in total mass and temperature. Also, a discrepancy has been observed for the 6He isotope, which could be explained by finite size effects or by the specific halo nature of this cluster