2,162 research outputs found
Fluctuations of fragment observables
This contribution presents a review of our present theoretical as well as
experimental knowledge of different fluctuation observables relevant to nuclear
multifragmentation. The possible connection between the presence of a
fluctuation peak and the occurrence of a phase transition or a critical
phenomenon is critically analyzed. Many different phenomena can lead both to
the creation and to the suppression of a fluctuation peak. In particular, the
role of constraints due to conservation laws and to data sorting is shown to be
essential. From the experimental point of view, a comparison of the available
fragmentation data reveals that there is a good agreement between different
data sets of basic fluctuation observables, if the fragmenting source is of
comparable size. This compatibility suggests that the fragmentation process is
largely independent of the reaction mechanism (central versus peripheral
collisions, symmetric versus asymmetric systems, light ions versus heavy ion
induced reactions). Configurational energy fluctuations, that may give
important information on the heat capacity of the fragmenting system at the
freeze out stage, are not fully compatible among different data sets and
require further analysis to properly account for Coulomb effects and secondary
decays. Some basic theoretical questions, concerning the interplay between the
dynamics of the collision and the fragmentation process, and the cluster
definition in dense and hot media, are still open and are addressed at the end
of the paper. A comparison with realistic models and/or a quantitative analysis
of the fluctuation properties will be needed to clarify in the next future the
nature of the transition observed from compound nucleus evaporation to
multi-fragment production.Comment: Contribution to WCI (World Consensus Initiative) Book " "Dynamics and
Thermodynamics with Nuclear Degrees of Freedom", to appear on Euorpean
Physics Journal A as part of the Topical Volume. 9 pages, 12 figure
Tracking energy fluctuations from fragment partitions in the Lattice Gas model
Partial energy fluctuations are known tools to reconstruct microcanonical
heat capacities. For experimental applications, approximations have been
developed to infer fluctuations at freeze out from the observed fragment
partitions. The accuracy of this procedure as well as the underlying
independent fragment approximation is under debate already at the level of
equilibrated systems. Using a well controlled computer experiment, the Lattice
Gas model, we critically discuss the thermodynamic conditions under which
fragment partitions can be used to reconstruct the thermodynamics of an
equilibrated system.Comment: version accepted for publication in Phys.Rev.
Comment on "Partial energies fluctuations and negative heat capacities" by X. Campi et al
Studying the energy partioning published in nucl-th/0406056v2 we show that
the presented results do not fulfill the sum rule due to energy conservation.
The observed fluctuations of the energy conservation test point to a numerical
problem. Moreover, analysis of the binding energies show that the fragment
recognition algorithm adopted by Campi et al. leads with a sizeable probability
to fragments containing up to the total mass even for excitation energies as
large as 3/4 of the total binding. This surprising result points to another
problem since the published inter-fragment energy is not zero while a unique
fragment is present. This problem may be due to either the fragment recognition
algorithm or to the definition of the inter and intra-fragment energy. These
numerical inconsistencies should be settled before any conclusion on the
physics can be drawn
Experimental Signals of Phase Transition
The connection between the thermodynamics of charged finite nuclear systems
and the asymptotically measured partitions is presented. Some open questions,
concerning in particular equilibrium partitions are discussed. We show a
detailed comparison of the decay patterns in Au+ C,Cu,Au central collisions and
in Au quasi-projectile events. Observation of abnormally large fluctuations in
carefully selected samples of data is reported as an indication of a first
order phase transition (negative heat capacity) in the nuclear equation of
state.Comment: 8 pages, 8th International Conference on Nucleus-Nucleus Collisions,
Moscow 200
Negative heat capacity in the critical region of nuclear fragmentation: an experimental evidence of the liquid-gas phase transition
An experimental indication of negative heat capacity in excited nuclear
systems is inferred from the event by event study of energy fluctuations in
quasi-projectile sources formed in collisions at 35 A.MeV. The
excited source configuration is reconstructed through a calorimetric analysis
of its de-excitation products. Fragment partitions show signs of a critical
behavior at about 5 A.MeV excitation energy. In the same energy range the heat
capacity shows a negative branch providing a direct evidence of a first order
liquid gas phase transition.Comment: 4 Postscript figures, submitted to Phys. Rev. Lett. on 14-apr-199
Risk Stratification Before and During Treatment in Newly Diagnosed Multiple Myeloma: From Clinical Trials to the Real-World Setting
Multiple Myeloma (MM) is a hematologic malignancy characterized by a wide clinical and biological heterogeneity leading to different patient outcomes. Various prognostic tools to stratify newly diagnosed (ND)MM patients into different risk groups have been proposed. At baseline, the standard-of-care prognostic score is the Revised International Staging System (R-ISS), which stratifies patients according to widely available serum markers (i.e., albumin, β 2-microglobulin, lactate dehydrogenase) and high-risk cytogenetic abnormalities detected by fluorescence in situ hybridization. Though this score clearly identifies a low-risk and a high-risk population, the majority of patients are categorized as at “intermediate risk”. Although new prognostic factors identified through molecular assays (e.g., gene expression profiling, next-generation sequencing) are now available and may improve risk stratification, the majority of them need specialized centers and bioinformatic expertise that may preclude their broad application in the real-world setting. In the last years, new tools to monitor response and measurable residual disease (MRD) with very high sensitivity after the start of treatment have been developed. MRD analyses both inside and outside the bone marrow have a strong prognostic impact, and the achievement of MRD negativity may counterbalance the high-risk behavior identified at baseline. All these techniques have been developed in clinical trials. However, their efficient application in real-world clinical practice and their potential role to guide treatment-decision making are still open issues. This mini review will cover currently known prognostic factors identified before and during first-line treatment, with a particular focus on their potential applications in real-world clinical practice
Advancing the Boundaries of Formal Argumentation: Reflections on the AI3 2021 Special Issue
This article reflects on the Special Issue based on invited papers from the 5th Workshop on Advances in Argumentation in Artificial Intelligence (AI3 2021), showcasing the latest advancements in the field made by the Italian community on argumentation, as well as other researchers worldwide. This Special Issue highlights the importance of advancing logical-based AI approaches, such as formal argumentation, in the continuously expanding landscape of Artificial In- telligence. Papers in this Special Issue cover a diverse range of topics, including argument game-based proof theories, analysis of legal cases, decomposability in abstract argumentation, meta-argumentation approaches, explanations for model outputs using causal models, representation of natural argumentative discourse, and Paraconsistent Weak Kleene logic-based belief revision. By em- phasizing these innovative research contributions, this article underscores the need for continued progress in the field of Formal Argumentation to complement and enhance the ongoing developments in AI
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