Search results for " diffusion"
showing 10 items of 521 documents
Modeling of surface vs. bulk ionic conductivity in fixed charge membranes
2003
A two-region model for describing the conductivity of porous fixed charge membranes is proposed. In the surface region, the conductivity is due to the mobile positive ions (counterions) around the negative fixed charges. In the pore center region, the conductive properties resemble those of the external electrolyte solution because the fixed charges are assumed to be effectively neutralized by the counterions in the surface region. Activation energies and surface diffusion coefficients are estimated by assuming that the counterion jump from a fixed charge group is the rate limiting process for surface transport. The barrier energy for this jump is calculated using a simple electrostatic mod…
Novel method for determination of tritium depth profiles in metallic samples
2019
Tritium accumulation in fusion reactor materials is considered a serious radiological issue, therefore a lot of effort has been concentrated on the development of radiometric techniques. A novel method, based on gradual dissolution, for the determination of the total tritium content and its depth profiles in metallic samples is demonstrated. This method allows for the measurement of tritium in metallic samples after their exposure to a hydrogen and tritium mixture, tritium containing plasma or after irradiation with neutrons resulting in tritium formation. In this method, successive layers of metal are removed using an appropriate etching agent in the controlled regime and the amount of evo…
Adopting sustainable irrigation technologies in Italy: a study on the determinants of inter- and intra-farm diffusion
2023
This paper analyses the drivers for adopting irrigation systems with water conservation and saving technologies (WCSTs) by Italian farmers. The agricultural sector in Italy, like in other Mediterranean countries, suffers from water scarcity and water endowment variability. Water resources play a decisive role in agricultural production and in implementing large-scale WCSTs capable of improving the resilience of the whole agricultural sector. This study uses a microeconomic panel data approach to estimate farmers' decisions in adopting (inter-farm) sustainable irrigation technologies and assesses the intensity of (intra-farm) water-saving practices. Our analysis identifies the main determina…
Joves Investigadors i Difusió Arqueològica. Primer Seminari d’Arqueologia (UVEG)
2012
Report of workshop activities.
High-dimensional Big Data processing with dictionary learning and diffusion maps
2015
Algorithms for modern Big Data analysis deal with both massive amount of sam- ples and a large number of features (high-dimension). One way to cope with these challenges is to assume and discover the existence of localization in the data by uncovering its intrinsic geometry. This approach suggests that different data segments can be analyzed separately and then unified in order to gain an understanding of the whole phenomenon. Methods that utilize efficiently local- ized data are attractive for high-dimensional big data analysis, because they can be parallelized, and thus the computational resources, which are needed for their utilization, are realistic and affordable. These methods can explo…
Domain wall motion in a diffusive weak ferromagnet
2019
We study the domain wall motion in a disordered weak ferromagnet, induced by injecting a spin current from a strong ferromagnet. Starting from the spin diffusion equation describing the spin accumulation in the weak ferromagnet, we calculate the force and torque acting on the domain wall. We also study the ensuing domain wall dynamics, and suggest a possible measurement method for detecting the domain wall motion via measuring the additional resistance.
Drifting through Basic Subprocesses of Reading: A Hierarchical Diffusion Model Analysis of Age Effects on Visual Word Recognition
2016
International audience; Reading is one of the most popular leisure activities and it is routinely performed by most individuals even in old age. Successful reading enables older people to master and actively participate in everyday life and maintain functional independence. Yet, reading comprises a multitude of subprocesses and it is undoubtedly one of the most complex accomplishments of the human brain. Not surprisingly, findings of age-related effects on word recognition and reading have been partly contradictory and are often confined to only one of four central reading subprocesses, i.e., sublexical, orthographic, phonological and lexico-semantic processing. The aim of the present study…
Multiparametric 18F-FDG PET-MRI of the breast: are there differences in imaging biomarkers of contralateral healthy tissue between patients with and …
2019
The rationale was to assess whether there are differences in multiparametric 18F-FDG PET/MRI biomarkers of contralateral healthy breast tissue in patients with benign and malignant breast tumors. Methods: In this institutional review board-approved prospective single-institution study, 141 women with imaging abnormalities on mammography or sonography (BI-RADS 4/5) underwent combined 18F-FDG PET/MRI of the breast at 3T with dynamic contrast-enhanced MRI, diffusion-weighted imaging, and the radiotracer 18F-FDG. In all patients, the following imaging biomarkers were recorded for the contralateral (tumor-free) breast: breast parenchymal uptake (BPU) (from 18F-FDG PET), mean apparent diffusion c…
Comprehensive pharmacokinetic model of insulin Glargine and other insulin formulations.
2005
In this paper, a comprehensive pharmacokinetic model for different insulin formulations including insulin Glargine is developed based on the model proposed by Trajanoski et al. (1993). Current models show limitations for insulin Glargine due to the appearance of an uncharacteristic peak in the concentration-time evolution of plasma insulin that does not coincide with real experimental data. This important limitation has been solved in this paper by introducing a new virtual insulin state called the bound state, in addition to the dimeric and hexameric ones. Trying to describe the retarded action of insulin Glargine, the modeling idea behind this approach is that immediately after the subcut…
Quantitative magnetic resonance imaging for focal liver lesions: bridging the gap between research and clinical practice
2021
Magnetic resonance imaging (MRI) is highly important for the detection, characterization, and follow-up of focal liver lesions. Several quantitative MRI-based methods have been proposed in addition to qualitative imaging interpretation to improve the diagnostic work-up and prognostics in patients with focal liver lesions. This includes DWI with apparent diffusion coefficient measurements, intravoxel incoherent motion, perfusion imaging, MR elastography, and radiomics. Multiple research studies have reported promising results with quantitative MRI methods in various clinical settings. Nevertheless, applications in everyday clinical practice are limited. This review describes the basic princ…