Non-Gaussian noise effects in the dynamics of a short overdamped Josephson junction

The role of thermal and non-Gaussian noise on the dynamics of driven short overdamped Josephson junctions is studied. The mean escape time of the junction is investigated considering Gaussian, Cauchy-Lorentz and Levy-Smirnov probability distributions of the noise signals. In these conditions we find resonant activation and the first evidence of noise enhanced stability in a metastable system in the presence of Levy noise. For Cauchy-Lorentz noise source, trapping phenomena and power law dependence on the noise intensity are observed.

Cationic SLN for siRNA and DNA plasmid delivery in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and the third leading cause of cancer-related deaths. For the treatment of HCC several drugs are under development, but the only one with proven survival benefit is sorafenib. This agent is a multikinase inhibitor that blocks Raf signaling and VEGF, PDGF and c-Kit. It has antiproliferative and antiangiogenic activity and delays tumor progression [1,2]. Moreover, systemic tumor-targeted gene delivery is attracting increasing attention as a promising alternative to conventional therapeutic strategies. At this purpose a large number of viral and non-viral vectors have been studied and applied as systems of stable transfec…

BeppoSAX discovery of a new X-ray pulsar

A Preliminary BeppoSAX Study of the (Bright) Atoll Source GX 9+1

We report the preliminary results of a 350 ks BeppoSAX observation of the bright atoll source GX 9+1. In the field of view of the MECS instrument we discovered a X-ray pulsar, designated SAX J1802.7 - 2017, at an angular distance from GX 9+1 of ∼ 22 ′ . Since the X-ray emission of SAX J1802.7 - 2017 contaminates the energy spectrum above 10 keV we studied the energy spectrum of GX 9+1 in the energy band 0.1 - 10keV. We selected four regions in the color-color diagram and extracted one spectrum from each region. A bump below 1keV is present in the spectra using a model composed by a Comptonized component absorbed by neutral matter having an equivalent hydrogen column of 1.5 x 10 22 cm -2 . T…

THE ROLE OF NON-GAUSSIAN SOURCES IN THE TRANSIENT DYNAMICS OF LONG JOSEPHSON JUNCTIONS

We analyze the effects of different non-Gaussian noise sources on the transient dynamics of an overdamped long Josephson junction. We find nonmonotonic behavior of the mean escape time as a function of the noise intensity and frequency of the external driving signal for all the noise sources investigated.

Noise stabilization effects in models of interdisciplinary physics

Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The investigation of noise-induced phenomena in far from equilibrium systems is one of the approaches used to understand the behaviour of physical and biological complex systems. The enhancement of the lifetime of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) polymer translocation dynamics; (ii) transient regime of FitzHugh-Nagumo model; (iii) market stability in a nonlinear …

Dynamics of a FitzHugh-Nagumo system subjected to autocorrelated noise

We analyze the dynamics of the FitzHugh-Nagumo (FHN) model in the presence of colored noise and a periodic signal. Two cases are considered: (i) the dynamics of the membrane potential is affected by the noise, (ii) the slow dynamics of the recovery variable is subject to noise. We investigate the role of the colored noise on the neuron dynamics by the mean response time (MRT) of the neuron. We find meaningful modifications of the resonant activation (RA) and noise enhanced stability (NES) phenomena due to the correlation time of the noise. For strongly correlated noise we observe suppression of NES effect and persistence of RA phenomenon, with an efficiency enhancement of the neuronal respo…

Enhancement of stability in systems with metastable states

The investigation of noise‐induced phenomena in far from equilibrium systems is one of the approach used to understand the behaviour of physical and biological complex systems. Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The enhancement of the life‐time of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) Ising model (ii) Josephson junction; (iii) stochastic FitzHugh‐Nagumo model; (iv) a population dynamics model, and (v) …

The new X-ray pulsar J1802.7-2017 observed by bepposax

The discovery of the serendipitous X-ray pulsar SAX J1802.7–2017 from a BeppoSAX observation of GX 9+1

Abstract We have discovered a new X-ray source, SAX J1802.7–2017, ∼22′ away from the bright X-ray source GX 9+1, during a BeppoSAX observation of this latter one on 2001 September 16-20. The count rate of SAX J1802.7–2017 is comparable to the background (∼0.04 c/s) during the first 50 ks of the observation, then the count rate shows a large variability increasing up to ∼0.28 c/s. We have performed a temporal analysis finding that SAX J1802.7–2017 has a pulse period of ∼139.61 s, a projected orbital separation a x sin i of 48±5 lt-s and an orbital period of 3.7 +0.4 −0.2 days, allowing to classify the new object as an X-ray pulsar.

Role of the colored noise in a FitzHugh-Nagumo system driven by a periodic signal

During these last years the interest in neuronal dynamics increased. The study of this kind of system has been carried out by using the FitzHugh-Nagumo (FHN) model that is a simplified modification of the Hodgkin-Huxley model. Many interesting phenomena can be observed in the presence of fluctuations: modification of detection threshold by manipulation of noisy parameters (FHN model), noise-induced activation and coeherence resonance for suitable noise amplitude (absence of periodic signal), resonant activation for high periodic signals and noise reduction, intrinsic stochastic resonance (ISR) in Hodgkin-Huxley neuron and the enhancement of a weak signal by tuning the subthreshold intrinsic…

A primary subcutaneous hydatid cyst in the thigh. A case report

Hydatid disease is a parasitic disease considered endemic in many parts of the world such as South America, Middle East, Africa, Australia and the Mediterranean regions. Liver and lung hydatid disease accounts for 90% of all echinococcal cysts. Primary hydatid disease of subcutaneous sites is rare and the subcutaneous localization of a solitary hydatid cyst accounts for 1.6%. Not enough data exist for this localization, and only many heterogeneous data are described in order to define this rare condition.We present the case of a 68-year-old-woman affected by a mass in upper-medial side of her right thigh with a 12-year-growing history. Anamnestic data were accurately collected. Many differe…

Lifetime of the superconductive state in short and long Josephson junctions

We study the transient statistical properties of short and long Josephson junctions under the influence of thermal and correlated fluctuations. In particular, we investigate the lifetime of the superconductive metastable state finding the presence of noise induced phenomena. For short Josephson junctions we investigate the lifetime as a function both of the frequency of the current driving signal and the noise intensity and we find how these noise-induced effects are modified by the presence of a correlated noise source. For long Josephson junctions we integrate numerically the sine-Gordon equation calculating the lifetime as a function of the length of the junction both for inhomogeneous a…

Noise induced effects in overdamped Josephson junction in the presence of colored noise

We analyze the role of the correlated fluctuations, with a correlation time τc, in the dynamics of an overdamped Josephson junction in the presence of a periodic driving signal.

classical and quantum systems are investigated. First, the role of multiplicative and additive noise in a classical metastable system is analyzed. The mean lifetime of the metastable state shows a nonmonotonic behavior with a maximum as a function of both the additive and multiplicative noise intensities. In the second system, the simultaneous action of thermal and non-Gaussian noise on the dynamics of an overdamped point Josephson junction is studied. The eect of a Levy noise generated by a Cauchy‐Lorentz distribution on the mean lifetime of the superconductive metastable state, in the presence of a periodic driving, is investigated. We find resonant activation and noise enhanced stability…

The New X-Ray Pulsar J1802.7-2017 Observed by BeppoSAX

We report on the serendipitous discovery of a new X-ray source, SAX J1802.7-2017, ~ 22' away from the bright X-ray source GX 9+l, during a BeppoSAX observation of the latter source on 2001 September 16-20.The source was outside the FOV of the BeppoSAX/ LECS. We have verified its presence in both the MECS2 and MECS3 images, which probably excludes that this was a ghost image of a source outside the MECS FOV. Moreover, we can be sure that the source was within the PDS FOV. because the source X-ray pulsations were detected also in the PDS data (see below). We searched for known X-ray sources in a circular region of 30' centered at GX 9+1 in the SIMBAD data base. We found no known sources with …

"The discovery of serendipitous X-ray pulsar SAX J1802.7-2017 from a BeppoSAX observation of GX 9+1"