13,426 research outputs found

    Effective action in DSR1 quantum field theory

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    We present the one-loop effective action of a quantum scalar field with DSR1 space-time symmetry as a sum over field modes. The effective action has real and imaginary parts and manifest charge conjugation asymmetry, which provides an alternative theoretical setting to the study of the particle-antiparticle asymmetry in nature.Comment: 8 page

    Rejection Properties of Stochastic-Resonance-Based Detectors of Weak Harmonic Signals

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    In (V. Galdi et al., Phys. Rev. E57, 6470, 1998) a thorough characterization in terms of receiver operating characteristics (ROCs) of stochastic-resonance (SR) detectors of weak harmonic signals of known frequency in additive gaussian noise was given. It was shown that strobed sign-counting based strategies can be used to achieve a nice trade-off between performance and cost, by comparison with non-coherent correlators. Here we discuss the more realistic case where besides the sought signal (whose frequency is assumed known) further unwanted spectrally nearby signals with comparable amplitude are present. Rejection properties are discussed in terms of suitably defined false-alarm and false-dismissal probabilities for various values of interfering signal(s) strength and spectral separation.Comment: 4 pages, 5 figures. Misprints corrected. PACS numbers added. RevTeX

    Frequency and damping evolution during experimental seismic response of civil engineering structures

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    The results of the seismic tests on several reinforced-concrete shear walls and a four-storey frame are analysed in this paper. Each specimen was submitted to the action of a horizontal accelerogram, with successive growing amplitudes, using the pseudodynamic method. An analysis of the results allows knowing the evolution of the eigen frequency and damping ratio during the earthquakes thanks to an identification method working in the time domain. The method is formulated as a spatial model in which the stiffness and damping matrices are directly identified from the experimental displacements, velocities and restoring forces. The obtained matrices are then combined with the theoretical mass in order to obtain the eigen frequencies, damping ratios and modes. Those parameters have a great relevance for the design of this type of structures

    Quantum Cosmology in Scalar-Tensor Theories With Non Minimal Coupling

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    Quantization in the minisuperspace of non minimal scalar-tensor theories leads to a partial differential equation which is non separable. Through a conformal transformation we can recast the Wheeler-DeWitt equation in an integrable form, which corresponds to the minimal coupling case, whose general solution is known. Performing the inverse conformal transformation in the solution so found, we can construct the corresponding one in the original frame. This procedure can also be employed with the bohmian trajectories. In this way, we can study the classical limit of some solutions of this quantum model. While the classical limit of these solutions occurs for small scale factors in the Einstein's frame, it happens for small values of the scalar field non minimally coupled to gravity in the Jordan's frame, which includes large scale factors.Comment: latex, 18 page

    Guardando al «Siculorum» del 1948

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    Riflettere sulla prima annata del «Siculorum», datata 1948, vuol dire anzitutto per noi riconnetterci simbolicamente al principio, alle pagine da cui tutto ha avuto inizio, ma significa anche specchiarci in una temperie sociale, culturale e politica molto diversa. Si tratta, in altre parole, di un'occasione per comprendere noi stessi a partire da un passato recente ma lontanissimo, vista la velocità estrema dei cambiamenti succedutisi lungo questi settant'anni. Cominciamo insomma la nostra sezione di reprint non da un dibattito intorno ad un tema specifico, sollecitato dalla ristampa digitale di un grande libro, bensì da un tentativo di conversazione e di pensiero sul nostro ieri e sul nostro oggi, in vista di un domani incerto, difficilmente prevedibile ma (altrettanto) ineludibile. In questa riflessione, i primi due numeri del «Siculorum Gymnasium» ci fanno da falsariga e da apripista, in quanto pongono implicitamente alcune questioni decisive, anche in ordine al senso della cultura umanistica, al suo ruolo e ai suoi spazi nella società, ai suoi orizzonti di ricerca e ai suoi atteggiamenti etici, ai suoi saperi e alle sue forme. Abbiamo inviato i due numeri della prima annata in digitale a quattro studiosi, rappresentanti di diverse aree della ricerca umanistica. Abbiamo richiesto loro di rispondere ad alcune questioni poste dalla redazione

    Acidente Vascular Cerebral Isquémico Perinatal: Estudo Retrospectivo de 5 Anos em Maternidade Nível III

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    Objective To study the incidence, clinical presentation, risk factors, imaging diagnosis, and clinical outcome of perinatal stroke. Methods Data was retrospectively collected from full-term newborns admitted to the neonatal unit of a level III maternity in Lisbon with cerebral stroke, from January 2007 to December 2011. Results There were 11 cases of stroke: nine were arterial ischemic stroke and two were cerebral venous sinus thrombosis. We estimated an incidence of arterial ischemic stroke of 1.6/5,000 births and of cerebral venous sinus thrombosis of 7.2/100,000 births. There were two cases of recurrent stroke. Eight patients presented with symptoms while the remaining three were asymptomatic and incidentally diagnosed. The most frequently registered symptoms (8/11) were seizures; in that, generalized clonic (3/8) and focal clonic (5/8). Strokes were more commonly left-sided (9/11), and the most affected artery was the left middle cerebral artery (8/11). Transfontanelle ultrasound was positive in most of the patients (10/11), and stroke was confirmed by cerebral magnetic resonance in all patients. Electroencephalographic recordings were carried out in five patients and were abnormal in three (focal abnormalities n=2, burst-suppression pattern n=1). Eight patients had previously identified risk factors for neonatal stroke which included obstetric and neonatal causes. Ten patients were followed up at outpatients setting; four patients developed motor deficits and one presented with epilepsy. Conclusions Although a modest and heterogeneous sample, this study emphasizes the need for a high level of suspicion when it comes to neonatal stroke, primarily in the presence of risk factors. The prevalence of neurological sequelae in our series supports the need of long-term follow-up and early intervention strategies

    Quantitative and Qualitative Evaluation of Legume Forage Species in Southern Italy

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    Legume herbage quality and quantity depend on genetic background to be able to sustain metabolic activity under increasingly harsh environmental conditions. Field experiments were carried out in Foggia, a southern Italian town (a typical Mediterranean location) on varieties and ecotypes of two perennial legume (sainfoin and sulla) mostly widespread in Mediterranean environments. The experiment compared irrigated and non-irrigated conditions and two different seed rates. The aim of the study was to evaluate the effect of agronomic factors on herbage production and the nutritive value of the forage. Irrigation and higher seed rate treatment increased dry matter yield in both species. The genotypes of both species differed for agronomic adaptation and in nutritive characteristics which were influenced by irrigation treatment. Crude protein (CP) contents under irrigated treatment was lower than non irrigated only in sulla. Percentages of neutral detergent fibre (NDF) and acid detergent fiber (ADF) were influenced by lower seed rate. The genotypes exploit their genetic potentiality mainly under irrigated condition in sainfoin and sulla. Lower seed rate was more suitable under non irrigated conditions. The nutritive value, in both species, was related to the dry matter production and leaf stem proportion of genotypes
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