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Search Results: 1 - 10 of 461428 matches for " A. Orlandi "
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Quantum Harmonic Black Holes
R. Casadio,A. Orlandi
Physics , 2013, DOI: 10.1007/JHEP08(2013)025
Abstract: Inspired by the recent conjecture that black holes are condensates of gravitons, we investigate a simple model for the black hole degrees of freedom that is consistent both from the point of view of Quantum mechanics and of General Relativity. Since the two perspectives should "converge" into a unified picture for small, Planck size, objects, we expect our construction is a useful step for understanding the physics of microscopic, quantum black holes. In particular, we show that a harmonically trapped condensate gives rise to two horizons, whereas the extremal case (corresponding to a remnant with vanishing Hawking temperature) naturally falls out of its spectrum.
Bubble dynamics: (nucleating) radiation inside dust
R. Casadio,A. Orlandi
Physics , 2011, DOI: 10.1103/PhysRevD.84.024006
Abstract: We consider two spatially flat Friedmann-Robertson-Walker spacetimes divided by a time-like thin shell in the nontrivial case in which the inner region of finite extension contains radiation and the outer region is filled with dust. We will then show that, while the evolution is determined by a large set of constraints, an analytical description for the evolution of the bubble radius can be obtained by formally expanding for short times after the shell attains its minimum size. In particular, we will find that a bubble of radiation, starting out with vanishing expansion speed, can be matched with an expanding dust exterior, but not with a collapsing dust exterior, regardless of the dust energy density. The former case can then be used to describe the nucleation of a bubble of radiation inside an expanding dust cloud, although the final configuration contains more energy than the initial dust, and the reverse process, with collapsing radiation transforming into collapsing dust, is therefore energetically favored. We however speculate a (small) decaying vacuum energy or cosmological constant inside dust could still trigger nucleation. Finally, our perturbative (yet analytical) approach can be easily adapted to different combinations of matter inside and outside the shell, as well as to more general surface density, of relevance for cosmology and studies of defect formation during phase transitions.
Stability of planar fronts for a non--local phase kinetics equation with a conservation law in $D \le 3$
Eric A. Carlen,Enza Orlandi
Mathematics , 2011, DOI: 10.1142/S0129055X12500092
Abstract: We consider, in a $D-$dimensional cylinder, a non--local evolution equation that describes the evolution of the local magnetization in a continuum limit of an Ising spin system with Kawasaki dynamics and Kac potentials. We consider sub--critical temperatures, for which there are two local spatially homogeneous equilibria, and show a local nonlinear stability result for the minimum free energy profiles for the magnetization at the interface between regions of these two different local equilibrium; i.e., the planar fronts: We show that an initial perturbation of a front that is sufficiently small in $L^2$ norm, and sufficiently localized yields a solution that relaxes to another front, selected by a conservation law, in the $L^1$ norm at an algebraic rate that we explicitly estimate. We also obtain rates for the relaxation in the $L^2$ norm and the rate of decrease of the excess free energy.
Oblivious Neural Network Computing via Homomorphic Encryption
C. Orlandi,A. Piva,M. Barni
EURASIP Journal on Information Security , 2007, DOI: 10.1155/2007/37343
Abstract: The problem of secure data processing by means of a neural network (NN) is addressed. Secure processing refers to the possibility that the NN owner does not get any knowledge about the processed data since they are provided to him in encrypted format. At the same time, the NN itself is protected, given that its owner may not be willing to disclose the knowledge embedded within it. The considered level of protection ensures that the data provided to the network and the network weights and activation functions are kept secret. Particular attention is given to prevent any disclosure of information that could bring a malevolent user to get access to the NN secrets by properly inputting fake data to any point of the proposed protocol. With respect to previous works in this field, the interaction between the user and the NN owner is kept to a minimum with no resort to multiparty computation protocols.
Oblivious Neural Network Computing via Homomorphic Encryption
Orlandi C,Piva A,Barni M
EURASIP Journal on Information Security , 2007,
Abstract: The problem of secure data processing by means of a neural network (NN) is addressed. Secure processing refers to the possibility that the NN owner does not get any knowledge about the processed data since they are provided to him in encrypted format. At the same time, the NN itself is protected, given that its owner may not be willing to disclose the knowledge embedded within it. The considered level of protection ensures that the data provided to the network and the network weights and activation functions are kept secret. Particular attention is given to prevent any disclosure of information that could bring a malevolent user to get access to the NN secrets by properly inputting fake data to any point of the proposed protocol. With respect to previous works in this field, the interaction between the user and the NN owner is kept to a minimum with no resort to multiparty computation protocols.
Minimum black hole mass from colliding Gaussian packets
R. Casadio,O. Micu,A. Orlandi
Physics , 2012, DOI: 10.1140/epjc/s10052-012-2146-3
Abstract: We study the formation of a black hole in the collision of two Gaussian packets. Rather than following their dynamical evolution in details, we assume a horizon forms when the mass function for the two packets becomes larger than half the flat areal radius, as it would occur in a spherically symmetric geometry. This simple approximation allows us to determine the existence of a minimum black hole mass solely related to the width of the packets. We then comment on the possible physical implications, both in classical and quantum physics, and models with extra spatial dimensions.
Utilidad de la Tiroglobulina sérica preablación como predictor de evolución en los pacientes con carcinoma diferenciado de tiroides Usefulness of preablation serum thyroglobulin as a predictor of the evolution of patients with differentiated thyroid carcinoma
C Cabezón,A L?wenstein,A Orlandi,G Sartorio
Revista Argentina de Endocrinología y Metabolismo , 2011,
Abstract: El presente es un trabajo retrospectivo y multicéntrico para evaluar el valor de la Tiroglobulina (Tg) medida preablación como predictor de evolución en 274 pacientes con Carcinoma Diferenciado de Tiroides (CDT). Se incluyeron pacientes con anticuerpos a Tg (TgAb) negativos, tratados con tiroidectomía total, ablación del remanente, con una evolución mayor a 2 a os y a los cuales se les midió la Tg bajo estímulo de TSH. Se correlacionó la Tg preablación con el primer control de Tg bajo estímulo de TSH, con el estadio de TNM y con el estado de la enfermedad a Tiempo Final (TF) de seguimiento. Según el TNM, 205 pacientes estuvieron en Estadio 1, 19 en 2, 34 en 3 y 16 en 4. A T F, 172 pacientes estuvieron Libres de Enfermedad (LE), 43 con Enfermedad Dudosa (ED) y 59 con Enfermedad Persistente/Recurrente (EP). Agrupamos la población en rangos de Tg de 0.5-2.0; 2.1-10.0; 10.1-40.0, 40.1-100 y > 100 ng/mL. No hubo asociación significativa entre la Tg preablación y el estadio del TNM en tanto que la correlación con la Tg estimulada se observó solo en los pacientes con Tg < 2.0 ng/mL ya que el 86.7 % se mantuvo en ese rango. El resto de los grupos mostró, en respuesta a la ablación, una disminución de la Tg en porcentajes variables mientras que otros la aumentaron. Relacionando la Tg preablación con el estado de enfermedad a TF observamos que los pacientes con valores =10 ng/mL llegaban en mayor proporción LE al T F. El estadio de TNM mostró correlación con el estado de enfermedad a TF estando LE los de menor riesgo. En pacientes con CDT, los niveles de Tg preablación menores a 10 ng/mL son un marcador de buen pronóstico. Consideramos que la Tg preablación es útil para inferir la probable evolución de los paciente y una herramienta auxiliar para cálculo de riesgo del paciente. Los autores declaran no tener conflictos de interés. We present a retrospective and multicentric study to evaluate the measurement of preablation Thyroglobulin (Tg) as a predictor of the evolution of 274 patients with DTC. All the patients included in the study had negative TgAb, were treated with total thyroidectomy, ablation of the remnant tissue and an evolution period of more than 2 years. We measured preablation Tg under stimulation with endogenous TSH. We correlated the preablation Tg with that at the first control at LT4 withdrawal, with TNM stratification and the final statement of the disease at Final Time (FT). At the end of the evolution period, patients were classified as: free of disease (n=172), with doubtful disease (n=43) and with persistent disease (n=50). According to thei
A study of the 1 and 2 January 2010 sea-storm in the Ligurian Sea
F. Pasi, A. Orlandi, L. F. Onorato,S. Gallino
Advances in Science and Research (ASR) , 2011, DOI: 10.5194/asr-6-109-2011
Abstract: During the last days of 2009 and the first days of 2010, a wide and deep low pressure system over Western Europe generated a very extended and strong southerly pressure gradient on the whole Western Mediterranean Sea with a resulting very rough to high sea state. Over the Ligurian Sea (North Western Mediterranean) the resulting sea state was a combination of a very tuned (in both frequency and direction) swell coming from the south-west, with nearly oceanic peak wave period, and a broader north-westerly wind sea with shorter period. This kind of sea state, not extreme in terms of significant wave height, caused unusual widespread damages to Ligurian coastal structures. In this study, authors investigated the structure of such a combined sea state by analysing numerical weather prediction outputs coming from atmospheric and wave models and comparing them with data coming from ondametric buoys and meteorological stations located in the Ligurian Sea area. As a result, it was found that the forecasting model chain almost correctly predicted the wave height in a first phase, when the sea state was only due to the first south-westerly swell peak, while significantly underestimated the combined sea state, when also the second north-westerly wind sea developed and interacted with the first one. By analysing the structure of directional wave spectra forecasted by the operational wave model and measured by the buoys, authors have attempted to find out the reasons for model deficiencies in forecasting the time evolution of significant parameters characterising the sea state.
An observational and numerical case study of a flash sea storm over the Gulf of Genoa
A. Orlandi, F. Pasi, L. F. Onorato,S. Gallino
Advances in Science and Research (ASR) , 2008, DOI: 10.5194/asr-2-107-2008
Abstract: During the night between the 8 and 9 December 2006 the seawall of the Savona harbour (Liguria Region in north west of Italy) was overtopped by waves. In this work the "Savona flash sea storm" has been studied by analyzing the data recorded by meteo-marine observing stations and the data produced by high resolution meteo-marine numerical models. The data show that, due to the presence of a fast moving low pressure system, the event was characterized by a rapid transition and interaction between two different regimes of winds and related sea states. The results of the study suggest that the most damaging dynamics of the event could be correlated to a bi-modal structure of the wave spectrum. Based on this the authors suggest that a deeper study of the spectral structure of sea storms could lead to define new operational forecasting tools for the preventive evaluation of sea storms damaging potential.
A ESPERAN A NA VIDA DE MULHERES COM HIV/AIDS: AVALIA O PELA ESCALA DE HERTH
Fabiana de Souza Orlandi,Neide de Souza Pra a
Texto & Contexto - Enfermagem , 2013,
Abstract: Estúdio transversal-descriptivo que tuvo como objetivo evaluar el nível de esperanza de vida para las mujeres mayores de 50 a os com VIH/SIDA por la Escala de Esperanza de Herth. Se entrevistaron a 200 mujeres VIH-positivas en el grupo de edad de interés, asistidas en tres Servicios de Atención Especializada de ETS/SIDA en S o Paulo. Se cumplió la Resolución 196/96 y el estudio fue aprobado por el Comité de ética en Investigación. Los datos fueron recolectados en el a o2010 con la aplicación de dos instrumentos: caracterización de los sujetos y Escala de Esperanza de Herth. Los resultados mostraron una puntuación media de la aplicación de la Escala de Esperanza de Herth de 36.75 (±4,52), dentro de los 12 a 48. Esta puntuación está por debajo de los obtenidos con la misma escala para diversas patologías, lo que indica la percepción de la esperanza de vida reducida por la muestra. El enfermero debe proponer acciones que busquen la mejoría de la esperanza de la persona asistida, estableciendo metas realistas y fortaleciendo el suporte social.
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