Vacuum Polarization Effects in the Lorentz and PCT Violating Electrodynamics

In this work we report new results concerning the question of dynamical mass generation in the Lorentz and PCT violating quantum electrodynamics. A one loop calculation for the vacuum polarization tensor is presented. The electron propagator, "dressed" by a Lorentz breaking extra term in the fermion Lagrangian density, is approximated by its first order: this scheme is shown to break gauge invariance. Then we rather consider a full calculation to second order in the Lorentz breaking parameter: we recover gauge invariance and use the Schwinger-Dyson equation to discuss the full photon propagator. This allows a discussion on a possible photon mass shift as well as measurable, observable physical consequences, such as the Lamb-shift.Comment: Latex file, 19 pages, no figures, includes PACS number

GRUND 2008 nella sub area geografica 16 (GSA 16, Stretto di Sicilia): relazione finale

Il progetto Grund, finanziato a partire dal 1985 dapprima dalla D.G. Pesca e Acquacolura del Ministero per le politiche agricole, alimentari e forestali (MIPAAF) con i fondi della legge 41, in seguito dal MIPAAF e dalla DG IV della Commissione Europea, ha l’obiettivo generale di valutare la distribuzione, l’abbondanza e la composizione per taglia delle specie oggetto di pesca presenti nei mari Italiani. L’Istituto di ricerche sulle Risorse Marine e l’Ambiente, Sezione di Mazara del Vallo di IAMC-CNR, effettua campagne di ricerca in mare nella GSA 16 (FAO, 2001) dello Stretto di Sicilia, tramite rete a strascico (trawl survey), sin dalla primavera del 1985, con l’obiettivo generale di studiare l’abbondanza ed i cicli vitali delle risorse demersali e di stimarne lo stato di sfruttamento

MEDITS 2008 nella sub area geografica 16 (GSA 16, Stretto di Sicilia): relazione biologica

La campagna scientifica Medits, nell’ambito del Programma nazionale Italiano per la raccolta dei dati alieutici (Reg. CE n°199/2008 e n°665/2008), ha l’obiettivo generale di valutare la distribuzione, l’abbondanza e la composizione per taglia delle specie oggetto di pesca presenti nei mari Italiani. L’Istituto di ricerche per l’Ambiente Marino Costiero (IAMC), sede di Mazara del Vallo, del Consiglio nazionale delle Ricerche (CNR), effettua campagne di ricerca in mare nella GSA 16 (FAO, 2001) dello Stretto di Sicilia, tramite rete a strascico (trawl survey), sin dalla primavera del 1985, con l’obiettivo generale di studiare l’abbondanza ed i cicli vitali delle risorse demersali e di stimarne lo stato di sfruttamento

Aberration measurement and correction on a large field of view in fluorescence microscopy

The aberrations induced by the sample and/or by the sample holder limit the resolution of optical microscopes. Wavefront correction can be achieved using a deformable mirror with wavefront sensorless optimization algorithms but, despite the complexity of these systems, the level of correction is often limited to a small area in the field of view of the microscope. In this work, we present a plug and play module for aberration measurement and correction. The wavefront correction is performed through direct wavefront reconstruction using the spinning-pupil aberration measurement and controlling a deformable lens in closed loop. The lens corrects the aberrations in the center of the field of view, leaving residual aberrations at the margins, that are removed by anisoplanatic deconvolution. We present experimental results obtained in fluorescence microscopy, with a wide field and a light sheet fluorescence microscope. These results indicate that detection and correction over the full field of view can be achieved with a compact transmissive module placed in the detection path of the fluorescence microscope

Gauss-Seidel estimation of generalized linear mixed models with application to poisson modeling of spatially varying disease rates

Generalized linear mixed models (GLMMs) are often fit by computational procedures such as penalized quasi-likelihood (PQL). Special cases of GLMMs are generalized linear models (GLMs), which are often fit using algorithms like iterative weighted least squares (IWLS). High computational costs and memory space constraints make it difficult to apply these iterative procedures to datasets having a very large number of records. We propose a computationally efficient strategy based on the Gauss-Seidel algorithm that iteratively fits submodels of the GLMM to collapsed versions of the data. The strategy is applied to investigate the relationship between ischemic heart disease, socioeconomic status, and age/gender category in New South Wales, Australia, based on outcome data consisting of approximately 33 million records. For Poisson and binomial regression models, the Gauss-Seidel approach is found to substantially outperform existing methods in terms of maximum analyzable sample size. Remarkably, for both models, the average time per iteration and the total time until convergence of the Gauss-Seidel procedure are less than 0.3% of the corresponding times for the IWLS algorithm. Platform-independent pseudo-code for fitting GLMS, as well as the source code used to generate and analyze the datasets in the simulation studies, are available online as supplemental materials. © 2009 American Statistical Association, Institute of Mathematical Statistics, and Interface Foundation of North America

Gli intermediari finanziari

Dopo un'esposizione della teoria contemporanea dell'intermediazione finanziaria, viene analizzata la struttura dei circuiti di intermediazione nel nostro paese (diretto e intermediato) e come questa stia cambiando anche in seguito alle recenti modifiche legislative e regolamentari. In particolare si analizzano: gli intermediari finanziari bancari e quelli non bancari (societ\ue0 di leasing e factoring; investitori istituzionali nel capitale di rischio - venture capitalist e merchant banks; societ\ue0 di gestione del risparmio)

An evaluation of factors affecting the robustness of colour measurement and its potential to predict the grade of flotation concentrate

Recent developments in machine vision, applied to froth flotation, show the potential for the use of the measurement of froth surface descriptors to provide an improvement to the operation of flotation cells and banks. One such descriptor, froth colour, has been traditionally assumed to relate to the grade of the concentrate recovered. This work sets out to test this assumption, and was performed using a machine vision system, SmartFroth. This system included a camera hood with built in LED lighting, a colour calibration patch and a CIE ‘Lab’ colour space conversion algorithm, which all served to reduce the effect of ambient lighting on the colour measurements. The effectiveness of these techniques was evaluated by comparing colour measurements of dry synthetic ore under various lighting conditions. It was found that the influence of ambient lighting had not been completely eliminated. Batch flotation tests were conducted on a sulphide ore, from the Kennecott Utah Copperton Concentrator, and established that froth colour does not account for entrained gangue, which is barely visible on the froth surface. Thus, froth colour alone cannot be used to accurately predict concentrate grade