377 research outputs found
Complex WKB Analysis of a PT Symmetric Eigenvalue Problem
The spectra of a particular class of PT symmetric eigenvalue problems has
previously been studied, and found to have an extremely rich structure. In this
paper we present an explanation for these spectral properties in terms of
quantisation conditions obtained from the complex WKB method. In particular, we
consider the relation of the quantisation conditions to the reality and
positivity properties of the eigenvalues. The methods are also used to examine
further the pattern of eigenvalue degeneracies observed by Dorey et al. in
[1,2].Comment: 22 pages, 13 figures. Added references, minor revision
The dilute A_L models and the integrable perturbations of unitary minimal CFTs
Recently, a set of thermodynamic Bethe ansatz equations is proposed by Dorey,
Pocklington and Tateo for unitary minimal models perturbed by \phi_{1,2} or
\phi_{2,1} operator. We examine their results in view of the lattice analogues,
dilute A_L models at regime 1 and 2. Taking M_{5,6}+\phi_{1,2} and
M_{3,4}+\phi_{2,1} as the simplest examples, we will explicitly show that the
conjectured TBA equations can be recovered from the lattice model in a scaling
limit.Comment: 14 pages, 2 figure
Mode and tempo of the Paleocene-Eocene thermal maximum in an expanded section from the Venetian pre-Alps.
The central part of the Piave River valley in the Venetian pre-Alps of NE Italy exposes an expanded and continuous marine sediment
succession that encompasses the Paleocene series and the Paleocene to Eocene transition.
The Paleocene through lowermost Eocenemsuccession is >100 m thick and was depositednat middle to lower bathyal depths in a
hemipelagic, near-continental setting in the central western Tethys. In the Forada section, the Paleocene succession of limestone-marl couplets is sharply interrupted by an ~3.30- m-thick unit of clays and marls (clay marl unit). The very base of this unit represents the biostratigraphic Paleocene-Eocene boundary, and the entire unit coincides with the main carbon isotope excursion of the Paleocene-Eocene thermal maximum event. Concentrations of hematite and biogenic carbonate, ÎŽ13C
measurements, and abundance of radiolarians, all oscillate in a cyclical fashion and are interpreted to represent precession cycles. The main excursion interval spans fi ve complete cycles, that is, 105 ± 10 k.y. The overlying carbon isotope recovery interval, which is composed of six distinct limestone-marl couplets, is interpreted to represent six precessional cycles with a duration of 126 ± 12 k.y. The entire carbon isotope excursion interval in Forada has a total duration of ~231 ± 22 k.y., which is 5%â10% longer than previous estimates derived from open ocean sites (210â220 k.y.).
Geochemical proxies for redox conditions
indicate oxygenated conditions before, during, and after the carbon isotope excursion event.
The Forada section exhibits a nonstepped sharp decrease in ÎŽ13C (â2.35â°) at the base of the clay marl unit. The hemipelagic, near-continental depositional setting of Forada and the sharply elevated sedimentation rates throughout the clay marl unit argue for continuous rather than interrupted deposition and show that the initial nonstepped carbon isotope shift was not caused by a hiatus. A single sample at the base of the unit lacks biogenic carbonate.
Preservation of carbonate thereafter improves progressively up-section in the clay marl unit, which is consistent with a prodigiously abrupt and rapid acidifi cation of the oceans followed
by a slower, successive deepening of the carbonate compensation depth. Increased sedimentation rates through the clay marl unit
(approximately the main interval of the carbon isotope excursion) are consistent with an intensifi ed hydrological cycle driven by supergreenhouse conditions and enhanced weathering and transport of terrigenous material to this near-continental, hemipelagic environment in the central western Tethys.
The sharp transition in lithology from the clay marl unit to the overlying limestonemarl couplets in the recovery interval and
the coincident shift toward heavier ÎŽ13C values suggest that the silicate pump and continental weathering, the cause of the enhanced terrigenous fl ux to Forada, stopped abruptly.
This implies that the source of the light CO2 ceased to be added to the ocean-atmosphere system at the top of the clay marl unit
An overview on molecular characterization of thymic tumors: Old and new targets for clinical advances
Thymic tumors are a group of rare mediastinal malignancies that include three different histological subtypes with completely different clinical behavior: the thymic carcinomas, the thymomas, and the rarest thymic neuroendocrine tumors. Nowadays, few therapeutic options are available for relapsed and refractory thymic tumors after a first-line platinum-based chemotherapy. In the last years, the deepening of knowledge on thymusâ biological characterization has opened possibilities for new treatment options. Several clinical trials have been conducted, the majority with disappointing results mainly due to inaccurate patient selection, but recently some encouraging results have been presented. In this review, we summarize the molecular alterations observed in thymic tumors, underlying the great biological differences among the different histology, and the promising targeted therapies for the future
LâidentitĂ© professionnelle des enseignants face aux changement. Analyses empiriques dans le contexte italienne
La finalitĂ© de cet article est de proposer, Ă partir dâun certain nombre des donnĂ©s empiriques rĂ©coltĂ©es dans le contexte Ă©ducatif italien, une explication psychosociale de lâĂ©laboration de lâidentitĂ© professionnelle des enseignants en situation de changement. Une telle explication sera orientĂ©e Ă mettre en Ă©vidence le rĂŽle essentiel (et lâarticulation) des Ă©lĂ©ments biographiques, des reprĂ©sentations sociales et des pratiques Ă©ducatives dans le processus dâadaptation identitaire sollicitĂ© par les changements qui caractĂ©risent le contexte Ă©ducatif au point de vue institutionnel, social et individuel (nouveaux processus de migration, introduction des nouvelles technologies Ă lâĂ©cole, plusieurs reformes de la loi scolaire et de lâorganisation de lâenseignement).
Deux recherches ont Ă©tĂ© conduites dans une rĂ©gion de lâItalie du Sud (Campanie) en utilisant un entretien narratif semi structurĂ© (Bruner, 1992; Vermersch, 1994) avec deux groupes dâenseignants (52 et 43 respectivement).
Les rĂ©sultats permettent de dĂ©crire un certain nombre dâĂ©lĂ©ments identitaires du « mĂ©tier » enseignant (reprĂ©sentations, biographies, pratiques) qui semblent jouer un rĂŽle important dans le processus dâadaptation aux changements considĂ©rĂ©s
Shannon entropy approach reveals relevant genes in Alzheimer's disease
Alzheimer's disease (AD) is the most common type of dementia and affects millions of people worldwide. Since complex diseases are often the result of combinations of gene interactions, microarray data and gene co-expression analysis can provide tools for addressing complexity. Our study aimed to find groups of interacting genes that are relevant in the development of AD. In this perspective, we implemented a method proposed in a previous work to detect gene communities linked to AD. Our strategy combined co-expression network analysis with the study of Shannon entropy of the betweenness. We analyzed the publicly available GSE1297 dataset, achieved from the GEO database in NCBI, containing hippocampal gene expression of 9 control and 22 AD human subjects. Co-expressed genes were clustered into different communities. Two communities of interest (composed by 72 and 39 genes) were found by calculating the correlation coefficient between communities and clinical features. The detected communities resulted stable, replicated on two independent datasets and mostly enriched in pathways closely associated with neuro-degenative diseases. A comparison between our findings and other module detection techniques showed that the detected communities were more related to AD phenotype. Lastly, the hub genes within the two communities of interest were identified by means of a centrality analysis and a bootstrap procedure. The communities of the hub genes presented even stronger correlation with clinical features. These findings and further explorations on the detected genes could shed light on the genetic aspects related with physiological aspects of Alzheimer's disease
Development and validation of a nomogram predicting recurrence risk in women with symptomatic urinary tract infection
Objectives: To develop and externally validate a novel nomogram predicting recurrence
risk probability at 12 months in women after an episode of urinary tract infection.
Methods: The study included 768women from Santa Maria Annunziata Hospital, Florence,
Italy, affected by urinary tract infections from January 2005 to December 2009. Another 373
women with the same criteria enrolled at Santa Chiara Hospital, Trento, Italy, from January
2010 to June 2012 were used to externally validate and calibrate the nomogram. Univariate
and multivariate Cox regression models tested the relationship between urinary tract infection
recurrence risk, and patient clinical and laboratory characteristics. The nomogram was
evaluated by calculating concordance probabilities, as well as testing calibration of predicted
urinary tract infection recurrence with observed urinary tract infections. Nomogram variables
included: number of partners, bowel function, type of pathogens isolated (Grampositive/
negative), hormonal status, number of previous urinary tract infection recurrences
and previous treatment of asymptomatic bacteriuria.
Results: Of the original development data, 261 out of 768 women presented at least one
episode of recurrence of urinary tract infection (33.9%). The nomogram had a concordance
index of 0.85. The nomogram predictions were well calibrated. This model showed high
discrimination accuracy and favorable calibration characteristics. In the validation group (373
women), the overall c-index was 0.83 (P = 0.003, 95% confidence interval 0.51â0.99), whereas
the area under the receiver operating characteristic curve was 0.85 (95% confidence interval
0.79â0.91).
Conclusions: The present nomogram accurately predicts the recurrence risk of urinary
tract infection at 12 months, and can assist in identifying women at high risk of symptomatic
recurrence that can be suitable candidates for a prophylactic strategy
Scattering in the PT-symmetric Coulomb potential
Scattering on the -symmetric Coulomb potential is studied along a
U-shaped trajectory circumventing the origin in the complex plane from
below. This trajectory reflects symmetry, sets the appropriate
boundary conditions for bound states and also allows the restoration of the
correct sign of the energy eigenvalues. Scattering states are composed from the
two linearly independent solutions valid for non-integer values of the 2L
parameter, which would correspond to the angular momentum in the usual
Hermitian setting. Transmission and reflection coefficients are written in
closed analytic form and it is shown that similarly to other -symmetric scattering systems the latter exhibit handedness effect.
Bound-state energies are recovered from the poles of the transmission
coefficients.Comment: Journal of Physics A: Mathematical and Theoretical 42 (2009) to
appea
Psi clustering for the assessment of underground infrastructure deterioration
Remote sensing images find application in several different domains, such as land cover or land usage observation, environmental monitoring, and urbanization. This latter field has recently witnessed an interesting development with the use of remote sensing for infrastructural monitoring. In this work, we present an analysis of Sentinel-1 images, which were used to monitor the Italian provinces of Bologna and Modena located at the Emilia Region Apennines foothill. The goal of this study was the development of a machine learning-based detection system to monitor the deterioration of public aqueduct infrastructures based on Persistent Scatterer Interferometry (PSI). We evaluated the land deformation over a temporal range of five years; these series feed a k-means clustering algorithm to separate the pixels of the region according to different deformation patterns. Furthermore, we defined the critical areas as those areas where different patterns collided or overlapped. The proposed approach provides an informative tool for the structural health monitoring of underground infrastructures
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