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Search Results: 1 - 10 of 89861 matches for " I. Ferrari "
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Perturbative Analysis of Chern-Simons Field Theory in the Coulomb Gauge
Franco Ferrari,I. Lazzizzera
Physics , 1996, DOI: 10.1142/S0217751X98000767
Abstract: In this paper we analyse the perturbative aspects of Chern-Simons field theories in the Coulomb gauge. We show that in the perturbative expansion of the Green functions there are neither ultraviolet not infrared divergences. Moreover, all the radiative corrections are zero at any loop order. Some problems connected with the Coulomb gauge fixing, like the appearance of spurious singularities in the computation of the Feynman diagrams, are discussed and solved. The regularization used here for the spurious singularities can be easily applied also to the Yang-Mills case, which is affected by similar divergences.
Posterior probability of the Likelihood Ratio and (Fractional) Bayes Factor: new theoretical relations and practical uses
I. Smith,A. Ferrari
Physics , 2010,
Abstract: In the simple vs composite hypothesis test with a proper prior, the Bayes Factor (BF) is shown to be the posterior mean of the Likelihood Ratio (LR). Therefore, the posterior standard deviation of the LR or rather its posterior cumulative density function can be used to indicate the significativity of a detection by the BF and this detection procedure can be computed from a single Markov Chain. It is applied and compared for exoplanet detection. The previous statistics can be expressed from the Fractional BF (FBF) \cite{ohagan95} and the Probability distribution of the LR (PLR) \cite{aitkin97}. Two properties of the PLR related to the GLRT are noted and a procedure to optimize the PLR and the FBF two-parameters detectors according to their ROC curves is proposed. The performances of all tests are compared.
Toward a Field Theoretical Description of Topologically Linked Polymers
F. Ferrari,I. Lazzizzera
Physics , 1999,
Abstract: In this work a field theoretical model is constructed to describe the statistical mechanics of an arbitrary number of topologically linked polymers in the context of the analytical approach of Edwards. As an application, the effects of the topological interactions are studied in the one loop approximation. A natural way to include in the treatment also more sophisticated link invariants than the Gauss linking number is outlined.
Generalizations related to hypothesis testing with the Posterior distribution of the Likelihood Ratio
I. Smith,A. Ferrari
Statistics , 2014,
Abstract: The Posterior distribution of the Likelihood Ratio (PLR) is proposed by Dempster in 1974 for significance testing in the simple vs composite hypotheses case. In this hypotheses test case, classical frequentist and Bayesian hypotheses tests are irreconcilable, as emphasized by Lindley's paradox, Berger & Selke in 1987 and many others. However, Dempster shows that the PLR (with inner threshold 1) is equal to the frequentist p-value in the simple Gaussian case. In 1997, Aitkin extends this result by adding a nuisance parameter and showing its asymptotic validity under more general distributions. Here we extend the reconciliation between the PLR and a frequentist p-value for a finite sample, through a framework analogous to the Stein's theorem frame in which a credible (Bayesian) domain is equal to a confidence (frequentist) domain. This general reconciliation result only concerns simple vs composite hypotheses testing. The measures proposed by Aitkin in 2010 and Evans in 1997 have interesting properties and extend Dempster's PLR but only by adding a nuisance parameter. Here we propose two extensions of the PLR concept to the general composite vs composite hypotheses test. The first extension can be defined for improper priors as soon as the posterior is proper. The second extension appears from a new Bayesian-type Neyman-Pearson lemma and emphasizes, from a Bayesian perspective, the role of the LR as a discrepancy variable for hypothesis testing.
Influência da vitrifica o na incidência de ovócitos bovinos aneuplóides maturados in vitro.
H. S. Luna,I. Ferrari,R. Rumpf
Revista Brasileira de Saúde e Produ??o Animal , 2006,
Abstract: O presente estudo objetivou verificar a incidência de aneuploidias em ovócitos bovinos vitrificados em diferentes períodos de matura o. Os ovócitos foram obtidos de ovários de abatedouro e divididos em cinco grupos: controle (ovócitos n o vitrificados); grupos 0-h (vitrificados antes do come o da matura o); e grupos 8, 12 e 22-h (vitrificados respectivamente 8, 12 e 22 h após o come o da matura o). Os ovócitos permaneceram vitrificados por 24 h e ent o foram descongelados e completaram 24 horas de matura o. Em seguida os ovócitos foram desnudados, fixados em lamina e corados com orceína-acética. Nenhuma diferen a foi encontrado (P > 0,05) entre o grupo controle (6,2%, 1/16 ) e grupos 0, (22,0, 2/9) 8 h (22,0, 2/9), 12 (25,0%, 3/12), 22 h (23,5%, 4/17). Os resultados sugerem que a vitrifica o em diferentes períodos de matura o n o influencia na taxa de aneuploidia.
Calculation of Second Topological Moment of Two Entangled Polymers
F. Ferrari,H. Kleinert,I. Lazzizzera
Physics , 2000, DOI: 10.1007/s100510070013
Abstract: We set up a Chern-Simons theory for the entanglement of two polymers P_1 and P_2, and calculate the second topological moment , where m is the linking number. The result applies approximately to a polymer in an ensemble of many others, if these are considered as a single very long effective polymer.
Second Topological Moment < m^2 > of Two Closed Entangled Polymers
F. Ferrari,H. Kleinert,I. Lazzizzera
Physics , 2000, DOI: 10.1016/S0375-9601(00)00635-6
Abstract: We calculate the second topological moment < m^2 > of entanglement of two closed polymers $P_1$ and $P_2$ in a solution. The result holds approximately for a closed polymer linked to many others, which may be considered as a single very long effective polymer.
Retrospective Cohort Study on Acute Care in Obstetrics and Gynecology: Analogies and Differences When Compared to Emergency Medicine  [PDF]
Giuseppe Chiossi, Stefano Palomba, Sara Balduzzi, Maged M. Costantine, Angela I. Falbo, Anna M. Ferrari, Giovanni B. La Sala
Open Journal of Obstetrics and Gynecology (OJOG) , 2017, DOI: 10.4236/ojog.2017.74049
Abstract: Introduction: the demand for urgent obstetric and gynecology care has progressively increased: in the United States approximately 1.4 million gynecologic visits are made to the emergency department (ED) annually, while almost 75% of women make at least 1 unscheduled visit during pregnancy. Moreover, research has recently focused on setting standards in unscheduled care, and developing quality indicators to improve patients’ health. Therefore, we investigated the characteristics of women with acute gynecological or pregnancy complaints using quality indicators developed for emergency medicine, to better define the needs of this population and improve care. Methods: Retrospective cohort study on ED, and Obstetrics and Gynecology (ObGyn) triage visits, at a tertiary care hospital in Italy, during 2012. Data were analyzed with population-averaged logistic regression and Poisson regression. Results: When compared to the 33,557 ED visits, the 9245 ObGyntriage referrals were more frequently associated with pregnancy (≤12 weeks’ gestation, OR: 30.7, 95%CI; 24.5 - 38.4; >12 weeks’ gestation, OR 81.2, 95%CI; 64.8 - 101.4), vaginal bleeding (OR 156.6, 95%CI; 82.7 - 294.4), diurnal (night access OR 0.87, 95% CI; 0.78 - 0.96) and weekday access (holiday access OR 0.87, 95%CI; 0.78 - 0.95), frequent users (recurrent ED visits IRR 0.87, 95%CI; 0.83 - 0.9) and lower hospital admissions (ED admission OR 1.6, 95%CI; 1.4 - 1.8). Conclusion: ObGyn triage patients differed from ED users, and were at higher risk of “crowding”. Such diversities should be considered to improve female healthcare services and allocate resources more efficiently.
Inglés para matemáticos en la Universidad Simón Bolívar: Hacia un redise?o basado en un análisis de necesidades
Ferrari Fermín,Virna I; Torrealba M,Carlos E;
Núcleo , 2009,
Abstract: the purpose of this article is to report the application and results of a needs analysis conducted with the objective of redesigning the program ?english for mathematicians?, taught to pure and applied mathematics majors at universidad simón bolívar. the participants were individuals involved in the teaching-learning process: mathematics teachers, english teachers, and students who had already taken the program. open-question questionnaires were used to gather their opinions on several aspects and their answers were analyzed qualitatively with atlas ti. the findings show that the majority of the participants considered that the four linguistic skills need to be reinforced; most respondents also believed that more mathematical content must be included and reinforced throughout the program. several participants considered that the use of new technologies (icts) is essential. finally, all subjects feel that the course is necessary in the academic preparation of a mathematician.
Granulomatosis de Wegener y tuberculosis: Una mala combinación Wegener's granulomatosis and tuberculosis: A bad combination
Luciana Molinari,Javier I. Melamud,Luciana Ferrari,Pablo Landi
Medicina (Buenos Aires) , 2009,
Abstract: La enfermedad de Wegener es una vasculitis de peque os y medianos vasos asociada a anticuerpos anticitoplasma del neutrófilo (ANCA). Dentro de los órganos blancos, el pulmón se encuentra comprometido en el 85% de los casos. Numerosas entidades deben ser consideradas en el diagnóstico diferencial, entre ellas, la tuberculosis pulmonar. Presentamos el caso de un hombre de 54 a os de edad, con diagnóstico en el a o 1996 de enfermedad de Wegener, que comienza en agosto de 2007 con expectoración hemoptoica, disnea de esfuerzo progresiva y esputo con baciloscopia BAAR (+), por lo que inicia tratamiento antituberculoso. La baciloscopia no se constata en dos lavados broncoalveolares contemporáneos. Evoluciona con deterioro de la función renal, púrpura palpable y anticuerpos anticitoplasma del neutrófilo patrón citoplasmático (ANCA-c) positivo. Se interpreta reactivación de su enfermedad de base. Inicia tratamiento inmunosupresor y hemodiálisis y suspende tratamiento antituberculoso. Un mes después del alta se reinterna con cuadro similar al previo, con esputo seriado positivo para BAAR. Wegener's disease is a vasculitis of small and medium-sized vessels associated with anti-neutrophil cytoplasm antibodies (ANCA). Within their target organs the lungs are involved in 85% of cases. Many entities are part of the differential diagnosis, including pulmonary tuberculosis. We present the case of a 54 years old man, diagnosed as Wegener's disease in 1996 which begins in August 2007 with cough, hemoptysis, progressive dyspnea on effort and serial sputum positive for AFB and then starts TB treatment. Subsequent bronchoalveolar fluids resulted negative for AFB. The patient evolved with impaired renal function, palpable purpura and positive anti-neutrophil cytoplasm antibodies cytoplasmic pattern (c-ANCA), interpreted as Wegener's disease relapse. He started hemodialysis and immunosuppressive therapy and tuberculosis treatment was stopped. One month after discharge was readmitted with a similar picture with serial sputum positive for AFB.
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