Clay Minerals For Nanocomposites and Biotechnology: Surface Modification, Dynamics and Responses to Stimuli

Clay minerals find a wide range of application in composites, paints, drilling liquids, cosmetics, and medicine. This article reviews chemical and physical properties of natural and organically modified clay minerals to understand the nanometre-scale structure, surface characteristics, and application in functional materials. The relation between fundamental properties and materials design is emphasized and illustrated by examples. The discussion comprises the following: an overview; surface structure and cation density; solubility and solubility reversal by surface modification; the degree of covalent and ionic bonding represented by atomic charges; the distribution of metal substitution sites; measurements and simulations of interfacial properties at the nanometre scale; self-assembly, packing density, and orientation of alkylammonium surfactants on the clay mineral surface; the density and chain conformation of surfactants in organic interlayer spaces; the free energy of exfoliation in polymer matrices and modifications by tuning the cleavage energy; thermal transitions, diffusion, and optical responses of surfactants on the mineral surface; elastic moduli and bending stability of clay layers; and the adsorption mechanism of peptides onto clay mineral surfaces in aqueous solution. Potential applications in biotechnology and other future uses are described

Structure and Phase Transitions of Alkyl Chains on Mica

We use molecular dynamics as a tool to understand the structure and phase transitions [Osman et. al. J. Phys. Chem. B 2000, 104, 4433; 2002, 106, 653] in alkylammonium micas. The consistent force field 91 is extended for accurate simulation of mica and related minerals. We investigate mica sheets with 12 octadecyltrimethylammonium (C18) ions or 12 dioctadecyldimethylammonium (2C18) ions, respectively, as single and layered structures at different temperatures with periodicity in the xy plane by NVT dynamics. The alkylammonium ions reside preferably above the cavities in the mica surface with an aluminum-rich boundary. The nitrogen atoms are 380 to 390 pm distant to the superficial silicon-aluminum plane. With increasing temperature, rearrangements of C18 ions on the mica surface are found, while 2C18 ions remain tethered due to geometric restraints. We present basal-plane spacings in the duplicate structures, tilt angles of the alkyl chains, and gauche-trans ratios to analyze the chain conformation. Also, the individual phase transitions of the two systems on heating are explained. Where experimental data are available, the agreement is very good. We propose a geometric parameter lamba for the saturation of the surface with alkyl chains, which determines the preferred self-assembly pattern, i.e., islands, intermediate, or continuous. Lambda also determines the tilt angles in continuous layers on mica or other surfaces. The thermal decomposition appears to be a Hofmann elimination with mica as a base-template.Comment: 45 pages with 6 tables and 5 figure

Die Familienversicherung für Ehepaare in der Gesetzlichen Krankenversicherung: Problemanalyse und Lösungsvorschläge

Die 'Familienversicherung' nach § 10 SGB V ist ein zentrales Element des solidarischen Ausgleichs der Gesetzlichen Krankenversicherung (GKV). Sie beinhaltet sowohl die beitragsfreie Mitversicherung von Kindern als auch die von bestimmten Ehegatten. In diesem Beitrag wird nur die Mitversicherung von Ehegatten behandelt. Nach einer Beschreibung der Ausgangslage und verschiedener Reformvorschläge werden Bewertungskriterien erarbeitet und zur Beurteilung der derzeitigen Lage herangezogen. Dabei zeigt sich, dass an der Ausgestaltung der Ehegattenmitversicherung in mehrfacher Hinsicht Kritik zu üben ist: Ehepaare werden hinsichtlich einer horizontalen und vertikalen Gerechtigkeit ungleich behandelt, der für eine Beitragsbefreiung von Ehepartner von Mitgliedern verwendete Einkommensbegriff bezieht sich nicht auf die Einkommenssituation der ehelichen Wirtschaftsgemeinschaft und korrespondiert zudem nicht mit der Bemessungsgrundlage für eine mögliche freiwillige Mitgliedschaft in der GKV. Auch in Verbindung mit der fiskalischen Dimension der Familienversicherung für Ehepartner - ca. 9 Mrd. € an Leistungsausgaben im Jahr 2000 - ist eine Reformierung daher angezeigt. Aus der Zusammenstellung der verschiedenen Reformvorschläge zur beitragsfreien Versicherung von Ehepartnern wurden vier Optionen an Hand ökonomischer und verfassungsrechtlicher Kriterien beurteilt und mit Hilfe des Sozio-Oekonomischen Panels auch empirisch untersucht. Nur eine fünfte und partiell selber entwickelte Reformoption - ein GKV-Ehegattensplitting - genügt allen Bewertungskriterien und kann GKV-versicherte Ehepaare hinsichtlich ihrer beitragsrelevanten Einnahmen horizontal und vertikal gleich behandeln und gleichzeitig das Nicht-Diskriminierungsverbot von Ehepaaren gegenüber zwei Unverheirateten einhalten. --

Certification of the Mass Fractions of Vitamins in Whole Milk Powder - Certified Reference Material ERM®-BD600

This report describes the production of the reference material ERM-BD600, a whole milk powder certified for the mass fractions of water- and fat-soluble vitamins. All the required steps during the production were conducted according to ISO Guides 34 and 35 [1,2] to ensure the high quality of the final product, including matrix material processing, homogeneity and stability studies and value assignment. The matrix material, a spray dried whole milk powder, was packed into sachets containing approximately 100 g of powder, and stored at -30 ºC. Dedicated studies confirmed the homogeneity and stability of the vitamins in the milk powder under the conditions evaluated. The characterisation of the material, organised and coordinated by IRMM, was done by an inter-laboratory comparison. The certified and indicative values were obtained as the unweighted mean of the laboratory means of the accepted sets of results for each analyte, and the expanded uncertainty associated (k = 2) includes contributions from the homogeneity, the long term stability and the characterisation of the material.JRC.D.2-Reference material

The Certification of the Mass Fraction of Chloramphenicol in Pork Meat - Certified Reference Material ERM®-BB130

This report describes the preparation of the pork meat matrix reference material ERM-BB130 and the certification of the content (mass fraction) of chloramphenicol. The preparation and processing of the material, homogeneity and stability studies, and the characterisation are described hereafter and the results are discussed. Uncertainties were calculated in compliance with ISO Guide 98-3, Guide to the Expression of Uncertainty in Measurement (GUM) [1] and include uncertainties due to possible heterogeneity, instability, and characterisation.JRC.DG.D.2-Reference material

The Certification of the Mass Fraction of Oxytetracycline in Partially Skimmed Milk - Certified Reference Materials ERM®-BB492 and ERM®-BB493

This report describes the preparation of two milk powder matrix reference materials (ERM-BB492 and ERM-BB493) and the certification of their content (mass fraction) of oxytetracycline. The preparation and processing of the material, homogeneity and stability studies, and the characterisation are described hereafter and the results are discussed. Uncertainties were estimated in compliance with ISO Guide 98-3, Guide to the Expression of Uncertainty in Measurement (GUM) [1]. For ERM-BB492, the uncertainty contains contributions from possible heterogeneity, instability, characterisation, and purity of the common calibrant.JRC.DG.D.2-Reference material

Guidance Document on the Use of Reference Materials in Genetic Testing

The aim of this guidance document is to provide a short and user-friendly support to genetic testing laboratories. It is based on internationally harmonised basic concepts and terminology for quality assurance and control (QA/QC). Relevant terms of the International Organization for Standardization (ISO) and the International Vocabulary of Metrology (VIM) are explained and references to other expert texts are provided. The document includes discussion and clarification of several often misunderstood issues. It takes into account the current scientific knowledge and the existing technological capabilities. This document may be revised and constitutes a deliverable of th NoE EuroGentest.JRC.D.2-Reference material