Studio sull’iconografia di Aiace Telamonio con metodi di analisi esplorative dei dati

This work focuses on the images representing the myth of Ajax, son of Telamon, as represented in a corpus of finds from Greece and pre-Roman Italy. The iconography of the classical myth is studied together with other characters, such as kind of object, production, painting technique, place of finding, age. The age was fixed in intervals of 50 years, because of the wide chronological range and the uncertainty of the age of some finds. The data table crossing the finds with the characters was first submitted to Multiple Correspondence Analysis, where a strong relation was revealed. This suggested that an attempt should be made to estimate the age on the basis of the other characters. Qualitative Discriminant Analysis, applied to the objects with certain age, gave good classification functions that were used to estimate the age of the finds with uncertain age. In conclusion, the examination of the graphs shows how different meanings and functions of a Greek myth are illustrated throughout Classical Antiquity

Pionic BEC--BCS crossover at finite isospin chemical potential

We study the character change of the pionic condensation at finite isospin chemical potential \mu_\mathrm{I} by adopting the linear sigma model as a non-local interaction between quarks. At low |\mu_\mathrm{I}| the condensation is purely bosonic, then the Cooper pairing around the Fermi surface grows gradually as |\mu_\mathrm{I}| increases. This q-\bar q pairing is weakly coupled in comparison with the case of the q-q pairing that leads to color superconductivity.Comment: 17 pages, 3 figures, typos in eq.(6) and refs.[37] and [41] are corrected, published in Phys. Rev.

A dendrochronological analysis of Pinus pinea L. on the Italian mid-Tyrrhenian coast

In order to assess the response of the radial growth of Pinus pinea L. to climatic variability in Central Italy, dendrochronological and dendroclimatological analyses were carried out on five different populations scattered along the Tyrrhenian coasts of the peninsula. The aim of this study is to contribute to the understanding of the ecological demands of this species, particularly in the study area. For each site total ring, early-, and late-wood width chronologies were developed. Multidimensional analyses were performed for the three tree-ring datasets in order to analyze the relations between sites chronologies. Both Principal Component Analyses and hierarchical classifications highlighted an important difference of one site in respect to the other, probably due to site characteristics. Correlation functions were performed to infer the main climatic factors controlling the radial growth of the species. For a comparative study, we limited our attention to the common interval 1926-2003 (78 years) in which the response of the tree-ring chronologies to climate at both local and regional scale was investigated. Positive moisture balance in the late spring-summer period of the year of growth is the climatic driver of P. pinea radial growth in the study area. Moreover, this study shows how low summer temperatures strongly favor the radial growth of the species.Fil: Piraino, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto Argentino de Investigaciones de Zonas Aridas; ArgentinaFil: Camiz, Sergio. Universita degli studi di Roma "Sapienza". Dipartimento di Matematica; ItaliaFil: Di Filippo, Alfredo. Universita Degli Studi Della Tuscia. DendrologyLab; ItaliaFil: Piovesan, Gianluca. Universita Degli Studi Della Tuscia. DendrologyLab; ItaliaFil: Spada, Francesco. Universita degli studi di Roma "Sapienza". Dipartimento de biología ambientale; Itali

Statistical evaluation of cross-classifications derived from rearranged community data matrices

In order to enhance interpretation of two-way contingency tables (cross-classifications) derived from two hierarchical classifications, new indices are suggested to evaluate the relative contribution of nodes in either hierarchy to the nodes or to a partition of groups derived from the other hierarchy. Using these tools, cut-levels in both hierarchies can be found to define optimal partitions, and groups from both partitions can be associated in order to identify their mutual relationships. The method is illustrated with an actual example from vegetation ecology

Recoding and multidimensional analyses of vegetation data: a comparison

Two simulated coenoclines and a real data set were differently recoded with respect to the Braun-Blanquet coding (including presence/absence) and analysed through the most common multidimensional scaling methods. This way, we aim at contributing to the debate concerning the nature of the Braun-Blanquet coding and the consequent multidimensional scaling methods to be used. Procrustes, Pearson, and Spearman correlation matrices were computed to compare the resulting sets of coordinates and synthesized through their Principal Component Analyses (PCA). In general, both Procrustes and Pearson correlations showed high coherence of the obtained results, whereas Spearman correlation values were much lower. This proves that the main sources of variation are similarly identified by most of used methods/transformations, whereas less agreement results on the continuous variations along the detected gradients. The conclusion is that Correspondence Analysis on presence/absence data seems the most appropriate method to use. Indeed, presence/absence data are not affected by species cover estimation error and Simple Correspondence Analysis performs really well with this coding. As alternative, Multiple Correlation Analysis provides interesting information on the species distribution while showing a pattern of relevés very similar to that issued by PCA

Neutron-proton pairing in the BCS approach

We investigate the BCS treatment of neutron-proton pairing involving time-reversed orbits. We conclude that an isospin-symmetric hamiltonian, treated with the help of the generalized Bogolyubov transformation, fails to describe the ground state pairing properties correctly. In order for the np isovector pairs to coexist with the like-particle pairs, one has to break the isospin symmetry of the hamiltonian by artificially increasing the strength of np pairing interaction above its isospin symmetric value. We conjecture that the np isovector pairing represents part (or most) of the congruence energy (Wigner term) in nuclear masses.Comment: 9 pages, RevTex, submitted to Phys. Rev.

Local Density Approximation for proton-neutron pairing correlations. I. Formalism

In the present study we generalize the self-consistent Hartree-Fock-Bogoliubov (HFB) theory formulated in the coordinate space to the case which incorporates an arbitrary mixing between protons and neutrons in the particle-hole (p-h) and particle-particle (p-p or pairing) channels. We define the HFB density matrices, discuss their spin-isospin structure, and construct the most general energy density functional that is quadratic in local densities. The consequences of the local gauge invariance are discussed and the particular case of the Skyrme energy density functional is studied. By varying the total energy with respect to the density matrices the self-consistent one-body HFB Hamiltonian is obtained and the structure of the resulting mean fields is shown. The consequences of the time-reversal symmetry, charge invariance, and proton-neutron symmetry are summarized. The complete list of expressions required to calculate total energy is presented.Comment: 22 RevTeX page

The Relativistic Linear Singular Oscillator

Exactly-solvable model of the linear singular oscillator in the relativistic configurational space is considered. We have found wavefunctions and energy spectrum for the model under study. It is shown that they have correct non-relativistic limits.Comment: 14 pages, 12 figures in eps format, IOP style LaTeX file (revised taking into account referees suggestions

Algebraic approach in the study of time-dependent nonlinear integrable systems: Case of the singular oscillator

The classical and the quantal problem of a particle interacting in one-dimension with an external time-dependent quadratic potential and a constant inverse square potential is studied from the Lie-algebraic point of view. The integrability of this system is established by evaluating the exact invariant closely related to the Lewis and Riesenfeld invariant for the time-dependent harmonic oscillator. We study extensively the special and interesting case of a kicked quadratic potential from which we derive a new integrable, nonlinear, area preserving, two-dimensional map which may, for instance, be used in numerical algorithms that integrate the Calogero-Sutherland-Moser Hamiltonian. The dynamics, both classical and quantal, is studied via the time-evolution operator which we evaluate using a recent method of integrating the quantum Liouville-Bloch equations \cite{rau}. The results show the exact one-to-one correspondence between the classical and the quantal dynamics. Our analysis also sheds light on the connection between properties of the SU(1,1) algebra and that of simple dynamical systems.Comment: 17 pages, 4 figures, Accepted in PR

A Confidence Interval for the Wallace Coefficient of Concordance and Its Application to Microbial Typing Methods

Very diverse research fields frequently deal with the analysis of multiple clustering results, which should imply an objective detection of overlaps and divergences between the formed groupings. The congruence between these multiple results can be quantified by clustering comparison measures such as the Wallace coefficient (W). Since the measured congruence is dependent on the particular sample taken from the population, there is variability in the estimated values relatively to those of the true population. In the present work we propose the use of a confidence interval (CI) to account for this variability when W is used. The CI analytical formula is derived assuming a Gaussian sampling distribution and recurring to the algebraic relationship between W and the Simpson's index of diversity. This relationship also allows the estimation of the expected Wallace value under the assumption of independence of classifications. We evaluated the CI performance using simulated and published microbial typing data sets. The simulations showed that the CI has the desired 95% coverage when the W is greater than 0.5. This behaviour is robust to changes in cluster number, cluster size distributions and sample size. The analysis of the published data sets demonstrated the usefulness of the new CI by objectively validating some of the previous interpretations, while showing that other conclusions lacked statistical support