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We study the mean first-passage time (MFPT) for asymmetric continuous time random walks in continuous space characterised by finite mean waiting times and jump amplitudes with both finite average and finite variance. We derive an inhomogeneous Wiener-Hopf integral equation that allows the exact estimation of the MFPT, which depends on the whole distribution of the jump amplitudes, but on the average of the waiting times only. Thus, our findings hold for general non-Markovian processes, since Markovianity emerges solely with an exponential distribution of the waiting times. Through the paradigmatic case study of a general class of asymmetric distributions of the jump-amplitudes that is exponential towards the boundary and arbitrary in the opposite direction, we show, that only the average of the jump amplitudes in the opposite direction of the boundary contributes to the MFPT. Moreover, we determine a length-scale, which depends only of the distribution of jumps in the direction of the boundary, such that for initial positions close to the boundary the MFPT depends on the specific whole distribution of jump amplitudes, in opposition to the appearing universality for initial positions far away from the boundary., PRE2018-084427

The various types of generalized Cattaneo, called also telegrapher's equation, are studied. We find conditions under which solutions of the equations considered so far can be recognized as probability distributions, \textit{i.e.} are normalizable and non-negative on their domains. Analysis of the relevant mean squared displacements enables us to classify diffusion processes described by such obtained solutions and to identify them with either ordinary or anomalous super- or subdiffusion. To complete our study we analyse derivations of just considered examples the generalized Cattaneo equations using the continuous time random walk and the persistent random walk approaches.

In this chapter, we consider a randomly-scaled Gaussian process and discuss a number of applications to model fractional diffusion. Actually, this approach can be understood as a Gaussian diffusion in a medium characterized by a population of scales. This interpretation supports the idea that fractional diffusion emerges from standard diffusion occurring in a complex medium., BERC 2014-2017 (Basque Government); BCAM Severo Ochoa excellence accreditation SEV-2013-0323 (Spanish Ministry of Economy and Competitiveness MINECO)

In this work we study the role of a complex environment in the propagation of a front with curvature-dependent speed. The motion of the front is split into a drifting part and a fluctuating part. The drifting part is obtained by using the level set method, and the fluctuating part by a probability density function that gives a comprehensive statistical description of the complexity of the environment. In particular, the environment is assumed to be a diffusive environment characterized by the Erdélyi–Kober fractional diffusion. The evolution of the front is then analysed with a Polynomial Chaos surrogate model in order to perform Sensitivity Analysis on the parameters characterizing the diffusion and Uncertainty Quantification procedures on the modeled interface. Sparse techniques for Polynomial Chaos allowed a limited size for the simulation databases., PhD Grant "La Caixa 2014"

In opposition to standard probability distributions, quasi-probability distributions can have negative values which highlight nonclassical properties of the corresponding system. In quantum mechanics, such negative values allow for the description of the superposition of two quantum states. Here, we propose the same approach to model local extinction and counter-gradient in turbulent premixed combustion. In particular, the negative values of a quasi-probability correspond to the local reversibility of the progress variable, which means that a burned volume turns to be unburned and then the local extinction together with the counter-gradient interpretation follows. We derive the Michelson-Sivashinsky equation as the average of random fronts following the G-equation, and their fluctuations in position emerge to be distributed according to a quasi-probability distribution displaying the occurrence of local extinction and counter-gradient. The paper is an attempt to provide novel methods able to lead to new theoretical insights in combustion science., PhD grant "La Caixa 2014"

A considerable number of systems have recently been reported in which Brownian yet non-Gaussian dynamics was observed. These are processes characterised by a linear growth in time of the mean squared displacement, yet the probability density function of the particle displacement is distinctly non-Gaussian, and often of exponential (Laplace) shape. This apparently ubiquitous behaviour observed in very different physical systems has been interpreted as resulting from diffusion in inhomogeneous environments and mathematically represented through a variable, stochastic diffusion coefficient. Indeed different models describing a fluctuating diffusivity have been studied. Here we present a new view of the stochastic basis describing time-dependent random diffusivities within a broad spectrum of distributions. Concretely, our study is based on the very generic class of the generalised Gamma distribution. Two models for the particle spreading in such random diffusivity settings are studied. The first belongs to the class of generalised grey Brownian motion while the second follows from the idea of diffusing diffusivities. The two processes exhibit significant characteristics which reproduce experimental results from different biological and physical systems. We promote these two physical models for the description of stochastic particle motion in complex environments., the DFG within project ME 1535/6-1

The strong impact of wildfires in terms of lives and homes lost and of damage to ecosystems, calls for an urgent improvement in the risk management. The aim of the present research is the improvement of these software codes by proposing a complete physical characterization of fire-spotting within an approach that is ready to be implemented as a post-processing routine of standard outputs. The main feature of the proposed method is that the effects of random fluctuations are included in a way that preserves the existing structure of the operational and industrial codes and can be implemented directly. The operational code WRF-SFIRE have been used to test the proposed post-processing routine. Results show the suitability of the approach for simulating random effects due to turbulent convection and fire-spotting, which are cases not resolved by standard operational codes. Results of simulations including response analysis with test cases are shown and discussed., PhD grant "La Caixa 2014"

Wildfire propagation modelling is a challenging problem due to its complex multi-scale multi-physics nature. This process can be described by a reaction- diffusion equation based on the energy balance principle. Alternative technique is the so-called level-set method (LSM), used in wildfire modelling as well as in many other fields. In the present study a methodology for fire propagation modelling that reconciles these approaches is proposed. This methodology is distinguishable and significant from both academical and industrial point of view because of the inclusion of the ran- dom effects by preserving the existing algorithms and direct implementation as a post-processing numerical routine. The random behaviour of the fire front is caused, for example, by the turbulence and the fire-spotting phenomenon. A probability density function (PDF) is employed in order to describe the random process. In earlier studies it has been shown that new independent ignitions can increase the rate of spread (ROS) of fire and therefore should be carefully studied. In this respect, a physical parametrization of the fire-spotting distribution was proposed. Special attention in the present study is paid to the atmospheric stability conditions. The parametrization proposed in previous works is completed by the multiple fire-spotting modelling. Afterwards special attention is paid to the study of uniqueness of the PDF and consistency with the energy balance equation. Numerical results and discussions complete the study., PhD grant ”La Caixa 2014”

It is well known that the Michelson-Sivashinky equation describes hydrodynamic instabilities in turbulent premixed combustion. Here a formulation of the flame front propagation based on the G-equation and on stochastic fluctuations imposed to the average flame position is considered to derive the Michelson-Sivashinky equation from a modelling point of view. The same approach was shown to reproduce the G-equation along the motion of the mean flame position, when the stochastic fluctuations are removed, as well ast the Zimont & Lipatnikov model, when a plane front is assumed. The new results here presented support this promising approach as a novel and general stochastic formulation for modelling turbulent premixed combustion.

We consider a model formulation of the flame front propagation in turbulent premixed combustion based on stochastic fluctuations imposed to the mean flame position. In particular, the mean flame motion is described by a G-equation, while the fluctuations are described according to a probability density function which characterizes the underlying stochastic motion of the front. The proposed approach reproduces as special cases the G-equation along the motion of the mean flame position, when the stochastic fluctuations are removed, and the Zimont & Lipatnikov model, when a Gaussian density for fluctuations is used together with the assumption of a plane front. The potentiality of the approach is here investigated further focusing on the Darrieus-Landau (hydrodynamic) instabilities. In particular, this model formulation is set to lead to the Michelson-Sivashinsky equation. Furthermore, a formula that connects the consumption speed and the front curvature is established., PhD Grant "La Caixa 2014"

Present research concerns the physical background of a wild-fire propagation model based on the split of the front motion into two parts - drifting and fluctuating. The drifting part is solved by the level set method and the fluctuating part describes turbulence and fire-spotting. These phenomena have a random nature and can be modeled as a stochastic process with the appropriate probability density function. Thus, wildland fire propagation results to be described by a nonlinear partial differential equation (PDE) of the reaction-diffusion type. A numerical study of the effects of the atmospheric stability on wildfire propagation is performed through its effects on fire-spotting. Moreover, it is shown that the solution of the PDE as an indicator function allows to construct the energy balance equation in terms of the temperature., PhD Grant "La Caixa 2014"

A Voigt profile function emerges in several physical investigations (e.g. atmospheric radiative transfer, astrophysical spectroscopy, plasma waves and acoustics) and it turns out to be the convolution of the Gaussian and the Lorentzian densities. Its relation with a number of special functions has been widely derived in literature starting from its Fourier type integral representation. The main aim of the present paper is to introduce the Mellin-Barnes integral representation as a useful tool to obtain new analytical results. Here, starting from the Mellin-Barnes integral representation, the Voigt function is expressed in terms of the Fox H-function which includes representations in terms of the Meijer G-function and previously well-known representations with other special functions., Submitted to: J. Phys. A: Math. Gen

Lo scopo della presente ricerca è stato quello di valutare la capacità del medrossiprogesterone acetato di interferire sull'attività di alcune antracicline. I risultati hanno evidenziato che il medrossiprogesterone acetato potenzia l'attività di alcuni chemioterapici agendo sia sulla fluidità di membrana che sull'inibizione della depolarizzazione K indotta.

Le MST provocano una compromissione della capacità riproduttiva, sia nella donna che nell'uomo, è di tipo prevalentemente immunitario, ne derivano importanti conseguenze. La terapia antibiotica risulterebbe del tutto inefficace. Risulta necessario sperimentare altre forme di terapia: antinfiammatori, immunosoppressori, anticitochine (ove disponibili).

This paper has been withdrawn by the author due to a crucial error in the formulation., Comment: This paper has been withdrawn

The aim of the article is to investigate the relative dispersion properties of the Well Mixed class of Lagrangian Stochastic Models. Dimensional analysis shows that given a model in the class, its properties depend solely on a non-dimensional parameter, which measures the relative weight of Lagrangian-to-Eulerian scales. This parameter is formulated in terms of Kolmogorov constants, and model properties are then studied by modifying its value in a range that contains the experimental variability. Large variations are found for the quantity $g^*=2gC_0^{-1}$, where $g$ is the Richardson constant, and for the duration of the $t^3$ regime. Asymptotic analysis of model behaviour clarifies some inconsistencies in the literature and excludes the Ornstein-Uhlenbeck process from being considered a reliable model for relative dispersion., Comment: 15 pages, 10 figures, LaTeX source

Cellular contacts modify the way cells migrate in a cohesive group with respect to a free single cell. The resulting motion is persistent and correlated, with cells’ velocities self-aligning in time. The presence of a dense agglomerate of cells makes the application of single particle tracking techniques to define cells dynamics difficult, especially in the case of phase contrast images. Here, we propose an original pipeline for the analysis of phase contrast images of the wound healing scratch assay acquired in time-lapse, with the aim of extracting single particle trajectories describing the dynamics of the wound closure. In such an approach, the membrane of the cells at the border of the wound is taken as a unicum, i.e., the wound edge, and the dynamics is described by the stochastic motion of an ensemble of points on such a membrane, i.e., pseudo-particles. For each single frame, the pipeline of analysis includes: first, a texture classification for separating the background from the cells and for identifying the wound edge; second, the computation of the coordinates of the ensemble of pseudo-particles, chosen to be uniformly distributed along the length of the wound edge. We show the results of this method applied to a glioma cell line (T98G) performing a wound healing scratch assay without external stimuli. We discuss the efficiency of the method to assess cell motility and possible applications to other experimental layouts, such as single cell motion. The pipeline is developed in the Python language and is available upon request., Basque Government BERC 2018– 2021 Spanish Ministry of Economy and Competitiveness MINECO via the BCAM Severo Ochoa SEV-2017-0718 accreditation

BACKGROUND: Apoptosis appears to have an essential role in the control of testis germ cell number and Fas expression has been reported in apoptotic spermatocytes and spermatids. We investigated if Fas (CD95) was present on ejaculated human sperm and any relationship between Fas on sperm and the apoptotic marker Syto16. METHODS: Semen samples from 77 male partners of infertile couples were evaluated. Each sample was analysed both before and after semen preparation by conventional microscopical procedures and by flow cytometry (FC). A multiparameter FC analysis to assess simultaneously sperm concentration, sperm viability, sperm apoptosis, CD45 positive (leukocyte) and CD95 (Fas) positive cell concentration was carried out. A further 10 samples were studied by indirect immunofluorescence to confirm results. RESULTS: The mean concentration of CD95 positive cells was very low (

Objective To report a case of a patient with a severe myasthenia gravis (MG) who underwent controlled ovarian hyperstimulation for assisted conception. Design Case report and literature review. Setting Tertiary infertility center. Patient(s) A 40-year-old woman affected by severe MG. Intervention(s) Controlled ovarian hyperstimulation, oocyte retrieval, intracytoplasmic sperm injection (ICSI) procedure for severe oligoastenozoospermia. Main Outcome Measure(s) Short- and long-term effects of assisted reproduction treatment (ART) on the clinical course of MG. Result(s) A total of four ICSI cycles were performed. In the third cycle, a pregnancy was achieved, but a spontaneous abortion occurred. No changes in MG therapy were necessary, neither before nor after the treatment. All procedures were well tolerated and no exacerbations of symptoms occurred. By contrast a little, but persistent, improvement of clinical disease course was observed. Conclusion(s) This is the first report of a patient with severe MG who underwent ART cycles. Although more patients need to be evaluated, the present case suggests that MG patients should not be excluded a priori from ART.

Gonadotropin-releasing hormone (GnRH) agonist exert "in vivo" an inhibitory action on the growth of hormone-dependent canine mammary tumours (Lombardi et al. [1999] J. Vet. Pharmacol Ther. 22(1):56-61). The present experiments have been performed "in vitro" in order to investigate the mechanisms involved in this direct antiproliferative action of GnRH agonists. In particular, the aim was to study whether these compounds might exert their antiproliferative effect by interfering with the stimulatory action of epidermal growth factor (EGF). To this purpose, the effects of GnRH agonist, Goserelin (GnRH-A), on the mitogenic action of EGF, on EGF-activated intracellular signaling mechanisms (intracellular calcium and nitric oxide production) as well as on ATP induced cell proliferation and signalling, and on the binding of EGF receptors have been evaluated in primary culture of canine mammary tumour cells. The results of these "in vitro" studies show that GnRH-A counteracts the mitogenic action of EGF and ATP, decreases the EGF/ATP-induced calcium signalling and reduces EGF binding, probably by means of NO-induced [Ca2+]i downregulation. These data suggest that GnRH agonists may inhibit the proliferation of the tumour cells by interfering with the stimulatory action of EGF.

Failure of chemotherapy with anthracyclines as a result of drug resistance and toxicity is a major problem in the clinical management of neoplasia. The aim of the present study was to evaluate the activity of medroxyprogesterone acetate (MPA) as a chemosensitiser on anthracycline cytotoxicity. The study investigated whether such an effect could be related to an increase in lipid peroxidation, nitric oxide production, membrane fluidity and intracellular anthracycline concentration. The results showed that anthracyclines decreased nitric oxide production but increased membrane viscosity (polarisation constant) and lipid hydroperoxide formation in canine mammary tumour cells. Moreover, it was found that both drug-induced cytotoxicity and membrane viscosity increased in the presence of MPA. Conversely, lipid hydroperoxides decreased in MPA-supplemented cells. Medroxyprogesterone acetate did not show any effect on nitric oxide production. The two anthracyclines used (doxorubicin and idarubicin) showed differential intranuclear accumulation in canine mammary tumour cells, and MPA significantly modified intracellular concentration of anthracyclines.