Application of the cBΩ model to the calculation of diffusion parameters of Si in silicates

AbstractMaterials and articles made of acrylonitrile–butadiene–styrene (ABS) intended for contact with food must comply with the requirements of the European Plastic Regulation (EU) 10/2011, which lays down the food simulants and the time/temperature conditions to be applied for migration testing. Previous studies indicated that high concentrations of ethanol at temperatures above ambient may lead to swelling of ABS polymers resulting in increased migration. In this study migration kinetic data for a set of model substances at different temperatures were obtained using both food simulants stipulated in EU regulations and real food (milk, cream and olive oil). At the same time, the extent of polymer swelling was gravimetrically characterized after contact with simulants and different foods tested at several conditions to cover the majority of foreseeable applications of ABS. The obtained results confirmed that the use of high concentrations of ethanol–water, especially at high temperatures, causes the swelling of ABS polymers and results in significantly higher migration values compared to the tested foods as well as Tenax®. None of the real foods studied cause significant swelling of ABS. The widely used simulant 95% (v/v) aqueous ethanol proves not be suitable for compliance testing of ABS under the recommended conditions of Regulation (EU) 10/2011. Swelling of the polymer results in artificially higher diffusion coefficients or lower activation energies of diffusion. Migration prediction using polymer-specific diffusion parameters should therefore be considered to avoid over-conservative risk assessment for food contact materials and articles made of ABS.

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Phosphorous Magnetic Resonance Spectroscopy to Detect Regional Differences of Energy and Membrane Metabolism in Naïve Glioblastoma Multiforme

Cancers ◽

10.3390/cancers13112598 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2598

Author(s):

Lisa Maria Walchhofer ◽

Ruth Steiger ◽

Andreas Rietzler ◽

Johannes Kerschbaumer ◽

Christian Franz Freyschlag ◽

...

Keyword(s):

Glioblastoma Multiforme ◽

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Healthy Volunteers ◽

Regional Differences ◽

Primary Brain Tumor ◽

Brain Parenchyma ◽

Resonance Spectroscopy ◽

31P Mrs ◽

Diffusion Parameters

Background: Glioblastoma multiforme (GBM) is a highly malignant primary brain tumor with infiltration of, on conventional imaging, normal-appearing brain parenchyma. Phosphorus magnetic resonance spectroscopy (31P-MRS) enables the investigation of different energy and membrane metabolites. The aim of this study is to investigate regional differences of 31P-metabolites in GBM brains. Methods: In this study, we investigated 32 patients (13 female and 19 male; mean age 63 years) with naïve GBM using 31P-MRS and conventional MRI. Contrast-enhancing (CE), T2-hyperintense, adjacent and distant ipsilateral areas of the contralateral brain and the brains of age- and gender-matched healthy volunteers were assessed. Moreover, the 31P-MRS results were correlated with quantitative diffusion parameters. Results: Several metabolite ratios between the energy-dependent metabolites and/or the membrane metabolites differed significantly between the CE areas, the T2-hyperintense areas, the more distant areas, and even the brains of healthy volunteers. pH values and Mg2+ concentrations were highest in visible tumor areas and decreased with distance from them. These results are in accordance with the literature and correlated with quantitative diffusion parameters. Conclusions: This pilot study shows that 31P-MRS is feasible to show regional differences of energy and membrane metabolism in brains with naïve GBM, particularly between the different “normal-appearing” regions and between the contralateral hemisphere and healthy controls. Differences between various genetic mutations or clinical applicability for follow-up monitoring have to be assessed in a larger cohort.

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Mullite Diffusion Barriers for SiC-C/C Composites Produced by Pulsed Laser Deposition

MRS Proceedings ◽

10.1557/proc-555-79 ◽

1998 ◽

Vol 555 ◽

Cited By ~ 2

Author(s):

H. Fritze ◽

A. Schnittker ◽

T. Witke ◽

C. Rüscher ◽

S. Weber ◽

...

Keyword(s):

Pulsed Laser Deposition ◽

Pulsed Laser ◽

Target Material ◽

High Energy ◽

Single Step ◽

Laser Deposition ◽

Reduced Pressure ◽

Oxidation Rates ◽

Energy Impact ◽

Diffusion Parameters

AbstractPulsed Laser Deposition (PLD) allows the ablation of nonconductive and high melting point target materials and the preparation of films with complex composition. High energy impact leads to melting and evaporation of the target material in a single step. In case of mullite ablation, the flux of the metal components is stoichiometric. Under reduced pressure the oxygen content in the layers decreases. However, after a short oxidation treatment, the formation of mullite in the coating is completed, as confirmed by IR spectroscopy and XRD investigations. For a commercial Si-SiC precoated C/C material, the effectiveness of additional PLD mullite layers as outer oxidation protection is tested in the temperature range 773 K < T < 1873 K. Mullite coatings with a thickness of 2.5 pm improve the oxidation behaviour significantly. Because of SiO2 formation at the mullite-SiC interface, all samples exhibited a mass increase upon oxidation. For oxidation durations of three days, only amorphous SiO2 is formed at the mullite-SiC interface. The inward diffusion of oxygen across the outer mullite-containing layer controls the kinetics of the reaction, as was deduced from 18O diffusivity measurements in PLD mullite layers. At temperatures close to the eutectic temperature (1860 K), mullite can seal defects. The calculated oxidation rates resulting from the diffusion parameters in SiO2 and mullite are close to the thermogravimetric data.

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Calculation of the Dimensions of Drug-Polymer Devices Based on Diffusion Parameters

Journal of Pharmaceutical Sciences ◽

10.1021/js980006a ◽

1998 ◽

Vol 87 (7) ◽

pp. 827-832 ◽

Cited By ~ 58

Author(s):

J. Siepmann ◽

A. Ainaoui ◽

J.M. Vergnaud ◽

R. Bodmeier

Keyword(s):

Diffusion Parameters ◽

Polymer Devices

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Model for Epitaxial growth of Cobalt on CU(100)

MRS Proceedings ◽

10.1557/proc-160-221 ◽

1989 ◽

Vol 160 ◽

Cited By ~ 1

Author(s):

Dimitri D. Vvedensky ◽

Shaun Clarke

Keyword(s):

Epitaxial Growth ◽

Growth Kinetics ◽

Solid Model ◽

Free Energies ◽

Diffusion Parameters ◽

The Difference ◽

Kinetics Of

AbstractThe epitaxial growth kinetics of Co on Cu(100) are investigated with a kinetic solid-on-solid model. Two effects are found to dominate the growth of this system reflecting the difference in surface free energies betweenthe two materials: the difference of diffusion parameters, and the inability of Co to wet Cu(100) at lower temperatures.

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