Search results for "Diffusion"

Semi-empirical defect calculations for the perovskite KNbO3

2000

A new parametrization of the classical shell model for the cubic phase of the perovskite KNbO3 has been derived and used to calculate the structural, elastic and dielectric properties of this material. Using this parametrization, the defect formation and migration energies, as well as atomic displacements, have been calculated. In parallel, the quantum mechanical method of the intermediate neglect of the differential overlap (INDO) has been applied to the same problem. The migration energies for the O vacancy obtained by these quite different methods are reasonably close (0.68 eV and 0.79 eV, respectively) and also agree with the only experimental estimate available of approximately 1 eV. A…

Linear instability of the vertical throughflow in a horizontal porous layer saturated by a power-law fluid

2016

Abstract The effects of the vertical throughflow of a non-Newtonian power-law fluid on the onset of convective instability in a horizontal porous layer are investigated. The extended Darcy’s model of momentum diffusion is employed together with the Oberbeck–Boussinesq approximation. A stationary basic solution for the vertical throughflow is determined analytically. The basic velocity and temperature fields turn out to be independent of the non-Newtonian rheology. A linear stability analysis is carried out, leading to a fourth-order eigenvalue problem. A numerical solution of the eigenvalue problem is employed to obtain the neutral stability curves and the critical Rayleigh number for the o…

Application of White Mustard Bran and Flour on Bread as Natural Preservative Agents.

2021

In this study, the antifungal activity of white mustard bran (MB), a by-product of mustard (Sinapis alba) milling, and white mustard seed flour (MF) was tested against mycotoxigenic fungi in the agar diffusion method. The results obtained were posteriorly confirmed in a quantitative test, determining the minimum concentration of extract that inhibits the fungal growth (MIC) and the minimum concentration with fungicidal activity (MFC). Since MF demonstrated no antifungal activity, the MB was stored under different temperature conditions and storage time to determine its antifungal stability. Finally, an in situ assay was carried out, applying the MB as a natural ingredient into the dough to …

Evaluation of positron-emission-tomography for visualisation of migration processes in geomaterials

2008

Abstract Positron-emission-tomography (PET) was applied for direct visualisation of solute transport in order to overcome the limitations of conventional methods for measuring advection and diffusion properties. At intervals from minutes to days the 3D-spatial distribution of the PET-tracer is determined. This spatiotemporal evolution of the tracer concentration can be used as experimental basis for clarification of the relevant transport processes, derivation of transport parameters, and model calibration. Here, 18 F and 124 I in 0.01 M carrier solution of KF and KI, respectively, have been chosen out of the limited number of available PET-tracers, primarily on account of their decay time …

New Innovation Identification Approach Development Matrix

2018

Innovations have become one of the contemporary economics key driving forces behind competitive advantages and have become socioeconomic category of their own. Diffusion of innovations, which is an integral part of the scientific and technological base of national economies, promotes structural changes in economy. Companies have to pay close attention to market trends and have to be able to identify and create new innovations, thus increasing their competitiveness and meeting consumer demands and expectations. The objective of this research is to evaluate the concept of different innovations in organizations and propose a complex approach to identifying innovations in the form of a matrix t…

Sequenze di diffusione (DWI) nello studio del carcinoma prostatico: confronto tra b700 e b1400. Nostra esperienza

2014

Materiali e metodi: e' stato analizzato retrospettivamente un campione di 24 pazienti nei quali è stato posto il sospetto RM di CaP confermato all'esame istologico in 20 pazienti. Questi, di età compresa tra 47 e 76 anni (media 64+/- 10), hanno costituito la nostra popolazione. L'esame RM è stato eseguito con un'apparecchiatura da 1.5 T mediante l'ausilio di bobina endorettale. Oltre al protocollo (T2, T1), la valutazione spettroscopica e dinamica postcontrastografica sono state acquisite sequenze DWI sul piano assiale con valori di b pari a 700 e 1400 s/mm2. Le immagini morfologiche e di diffusione sono state analizzate da due radiologi in consenso. E' stato calcolato il coefficiente di di…

PERFORMANCE OF DIFFUSION KURTOSIS IMAGING FOR CHARACTERIZATION OF PROSTATE LESIONS USING 1.5T MAGNETIC RESONANCE IMAGING SCANNER

2020

The aim of the study is to evaluate the diagnostic performance of apparent diffusion coefficient (ADC) and apparent kurtosis coefficient (Kapp) for the characterization of prostate lesions on 1.5T MRI. This retrospective study included 34 patients with at least one lesion with PI-RADS score≥ 3. Performances of ADC and Kapp were evaluated using the Mann-Whitney U test and receiver operating characteristics curve (AUROC). Lesions with Gleason score≥6 had significantly lower Kapp compared to benign lesions (p=0.025). The ADC-ratio was the only significantly different parameter between GS≥7 and GS=6 lesions (p=0.039). Kapp showed the largest AUROC for the diagnosis of GS≥6 prostate cancers (AUR…

Role of the Apparent Diffusion Coefficient (ADC) values analysis in Diffusion Weighted Imaging (DWI-MR) in the characterization of prostatic disease …

Purpose To evaluate if apparent diffusion coefficient analysis on magnetic resonance imaging can differentiate between normal and pathological prostate tissue, including prostate cancer and precancerous conditions (ASAP and PIN). Materials and Methods Prostate MRI with endorectal coil was performed in 93 patients (mean age 65.4). Regions of interest were placed over suspicious areas, detected on MRI, and over areas with normal appearance, and ADC values were recorded. Statistical differences between ADC values of suspicious and normal areas were evaluated. Histopathological diagnosis, obtained from targeted biopsy in 51 patients and from prostatectomy in 42 patients, were correlated to ADC …

Controlling the semi-permeability of protein nanocapsules influences the cellular response to macromolecular payloads.

2021

Nanocapsules are an excellent platform for the delivery of macromolecular payloads such as proteins, nucleic acids or polyprodrugs, since they can both protect the sensitive cargo and target its delivery to the desired site of action. However, the release of macromolecules from nanocapsules remains a challenge due to their restricted diffusion through the nanoshell compared to small molecule cargo. Here, we designed degradable protein nanocapsules with varying crosslinking densities of the nanoshell to control the release of model macromolecules. While the crosslinking did not influence the degradability of the capsules by natural proteases, it significantly affected the release profiles. F…

Traveling Waves Emerging in a Diffusive Moving Filament System

2014

Starting from a minimal model for the actin cytoskeleton of motile cells we derive a spatially one dimensional model describing populations of right and left moving filaments with intrinsic velocity, diffusion and mutual alignment. For this model we derive traveling wave solutions whose speed and shape depend on the model parameters and the type of alignment. We discuss possible wave profiles obtained from analytical investigations as well as waves emerging in numerical simulations. In particular, we will explicitly comment on the observed wave speeds and how they are related to the model parameters. Moreover, some particularly interesting patterns being composed of several wave profiles ar…