Search results for "Diffusion"

La diffusion des sites internet en .fr dans l'espace périurbain et rural français

2000

ACL; International audience; II existe à l'heure actuelle très peu d'études sur la localisation et la diffusion des sites Internet compte tenu de la rareté des sources qui n'intègrent pas pour la plupart la dimension géographique (échelle nationale). A partir des fichiers de l'AFNIC, il est possible de spatialiser l'implantation des sites Internet uniquement à l'échelle des codes postaux. Pour évaluer la situation de la diffusion des sites Internet en milieu rural, le zonage en aire urbaine (ZAU) fournit une grille spatiale d'analyse pertinente.En août 1999, seulement 10 % des 40 000 sites recensés sont localisés en zone rurale et autant en milieu périurbain. Le réseau des petites villes (d…

Sviluppo di un software per l’analisi di immagini di Diffusion Kurtosis Imaging

2013

L’analisi mediante RM del tensore di diffusione (Diffusion Tensor Imaging, DTI) consente di valutare anche in vivo e con modalità non invasive il processo di diffusione delle molecole d’acqua nei tessuti biologici. La peculiare organizzazione di alcuni tessuti biologici (es: muscoli, sostanza bianca del sistema nervoso centrale e tessuti ad alta cellularità) influenza tale fenomeno rendendolo anisotropo e quindi ben valutabile con tali tecniche di studio. Nonostante i grandi vantaggi di tale tecnica, il DTI è basato su un modello molto semplificato che assume che lo spostamento per diffusione segua un profilo gaussiano il che è molto raro in un ambiente variegato come i tessuti biologic…

Protein diffusion in ovo

2014

Autocatalytic reaction-diffusion processes in restricted geometries

2008

We study the dynamics of a system made up of particles of two different species undergoing irreversible quadratic autocatalytic reactions: $A + B \to 2A$. We especially focus on the reaction velocity and on the average time at which the system achieves its inert state. By means of both analytical and numerical methods, we are also able to highlight the role of topology in the temporal evolution of the system.

Effects of Pressure, Temperature, and Particles Size on O2 Diffusion Dynamics in Silica Nanoparticles

2013

The O2 diffusion process in silica nanoparticles is experimentally studied in samples of average radius of primary particles ranging from 3.5 to 20 nm and specific surface ranging from 50 to 380 (m2/g). The investigation is done in the temperature range from 98 to 177 °C at O2 pressure ranging from 0.2 to 66 bar by measuring the interstitial O2 concentration by Raman and photoluminescence techniques. The kinetics of diffusion can be described by the Fick’s equation with an effective diffusion coefficient depending on the temperature, O2 pressure, and particles size. In particular, the dependence of the diffusion coefficient on the pressure and nanoparticles size is more pronounced at lower …

Utility of 3 Tesla diffusion-weighted magnetic resonance (DWMR) imaging for the characterisation of small solid renal tumours

2012

Purpose: To determine the utility of apparent diffusion coefficients (ADCs) for the characterisation of small solid renal lesions. Methods and Materials: 26 patients (GFR 30-60 mL/min) with 39 small (1-3 cm) solid renal masses [16 RCCs (10 clear cell types; 6 other types); 18 AMLs (10 fat-containing; 8 minimal-fat) and 5 oncocytomas] were examined on a 3 T system using DW-SS-EPI (b-values 0, 1000 s/mm2). The ADC of the lesions and the ADC of kidney were evaluated. Receiver operator characteristic analysis was performed to evaluate the diagnostic value of ADC for differentiating clear cell RCCs from other type RCCs, AMLs and oncocytomas. Results: The mean ADC of the lesions [1.22± 0.27 28 mm…

Diffusione del virus della “Tristeza” degli agrumi (CTV) in aree agrumicole italiane

2006

Computational modeling of protein diffusion in the cell nucleus using the lattice-Boltzmann method

2012

The number of fluorescence applications and methods of analysis is growing in the biological and related sciences. The aim of this work was to accurately determine the diffusion coefficient in nucleus, diffusion in the cytoplasm and nucleo-cytoplasmic translocation should be considered as well. Fluorescence recovery after photobleaching (FRAP) experiments were used in order to study protein diffusion. A numerical model for FRAP was used to determine the diffusion properties of proteins. The present method removed the difficulties of the conventional analysis, could produce, interesting results for protein diffusion in the cell.

Dimensionality reduction framework for detecting anomalies from network logs

2012

Dynamic web services are vulnerable to multitude of intrusions that could be previously unknown. Server logs contain vast amounts of information about network traffic, and finding attacks from these logs improves the security of the services. In this research features are extracted from HTTP query parameters using 2-grams. We propose a framework that uses dimensionality reduction and clustering to identify anomalous behavior. The framework detects intrusions from log data gathered from a real network service. This approach is adaptive, works on the application layer and reduces the number of log lines that needs to be inspected. Furthermore, the traffic can be visualized. peerReviewed

Using affinity perturbations to detect web traffic anomalies

2013

The initial training phase of machine learning algorithms is usually computationally expensive as it involves the processing of huge matrices. Evolving datasets are challenging from this point of view because changing behavior requires updating the training. We propose a method for updating the training profile efficiently and a sliding window algorithm for online processing of the data in smaller fractions. This assumes the data is modeled by a kernel method that includes spectral decomposition. We demonstrate the algorithm with a web server request log where an actual intrusion attack is known to happen. Updating the kernel dynamically using a sliding window technique, prevents the proble…