Fabrication of Dense, Shaped Barium Cerate by the Oxidation of Solid Metal-Bearing Precursors

Some rare-earth-doped alkaline-earth cerates (e.g., Nd₂O₃-doped BaCeO₃) are proton conductors that can act as solid state electrolytes in hydrogen or steam sensors, hydrogen pumps, steam electrolyzers, and fuel cells. In the present study, dense tapes of neodymia-doped barium cerate were produced by the oxidation of malleable Ba-CeH₃-Nd₂O₃precursor tapes. Precursor tapes were produced by cold-rolling either blended or milled mixtures of Ba, CeH₃, and Nd₂O₃ within a silver can. X-ray diffraction, electron microprobe analyses, and thermogravimetric analyses were used to study the phase transformations resulting from heat treatments conducted at 300° to 900°C in pure, flowing oxygen. Barium peroxide and cerium dioxide, produced during oxidation at ≤300°C, reacted at ≤500°C to form barium cerate. The rate of formation of barium cerate depended on the degree of milling of the solid metal-bearing precursor powder. Dense barium cerate tapes were obtained after heat treatment at 1080°C.     

Plasma Etching of Sialon

A new technique is presented for the etching of sialon and Si₃N₄ for microstructural control purposes. This technique, plasma etching, is rapid and delineates both β-sialon and glassy phases .     

Transport of surface-modified nanoparticles through cell monolayers

We synthesized three peptides, a D-polyarginyl peptide (r8(FITC)), a Tat peptide (Tat(FITC)), and a control peptide (Cp(FITC)) and attached each to amino-CLIO, a nanoparticle 30 nm in diameter. We then examined the effective permeability, Peff, of all six materials through CaCo-2 monolayers. The transport of peptide-nanoparticles was characterized by a lag phase (0-8 h) and a steady-state phase (9-27 h). The steady-state Peff values for peptides were in the order r8(FITC)>Tat(FITC)=Cp(FITC). When r8(FITC) and Tat(FITC) peptides were attached to the nanoparticle, they conferred their propensity to traverse cell monolayers onto the nanoparticle, whereas Cp(FITC) did not. Thus, when the r8(FITC) peptide was attached to the amino-CLIO nanoparticle, the resulting peptide-nanoparticle had a Peff similar to that of this poly-D-arginyl peptide alone. The Peff of r8(FITC)-CLIO (MW approximately 1000 kDa) was similar to that of mannitol (MW=182 Da), a poorly transported reference substance, with a far lower molecular weight. These results are the first to indicate that the modification of nanoparticles by attachment of membrane-translocating sequence-based peptides can alter nanoparticle transport through monolayers. This suggests that the surface modification of nanoparticles might be a general strategy for enhancing the permeability of drugs and that high-permeability nanoparticle-based therapeutics can be useful in selected pharmaceutical applications.     

Some observations on the polymerization of styrene in the presence of oils

Summary Data and properties of products obtained by polymerizing styrene in the presence of drying and semidrying oils have been presented. Evidence is given showing that conjugation in an oil or peroxide content are not of fundamental importance for obtaining homogeneous products. The increasing of the viscosity of the oils appears to lead to the formation of styrenated products of higher homogeneity.     

Einfluß der Segmentstruktur und der Vernetzung auf den Glasübergang Tg. Möglichkeiten der Vorausberechnung von Tg über die Kohäsionsenergie Ecoh

Linear polymers, particularly polyesters, and crosslinked epoxide systems were studied to determine the relationship between glass transition, T_g, and cohesive energy, E_coh, which was calculated from incremental values as described by Fedors. In the case of thermoplastics having no side chains and in the absence of pronounced intermolecular interactions, it was found that standardization of E_coh with reference to the number of structural elements capable of rather independent motions leads to a linear relationship between T_g, and E_coh from which T_g, can be predicted. Without modifying our equation to suit the polymer, the influence of substituents and side chains can as yet only be assessed when they form a small part of the total segment. In the case of crosslinked epoxide systems, addition of the contribution made by crosslinking to the value of T_g, for the uncured polymer calculated from E_coh results in a shift to higher T_g, values. In linear aliphatic polyamides and other polymers with analogous structure the formation of hydrogen bonds leads to an increase in T_g, comparable to the effect of chemical crosslinking. Reinforcing fillers also act as multifunctional crosslinks between the macromolecules and increase T_g. Just as E_coh can be used to calculate T_g, experimentally readily ascertainable T_g values can be used to calculate E_coh. This approach provides information on material properties like flexural strength at the yield point and torsional adhesive strength as well as on the effect of reinforcing fillers.     

The importance of dietary carbohydrates

Forty years ago carbohydrates (CHO) were regarded as a simple energy source whereas they are now recognized as important food components. The human diet contains a wide range of CHO, the vast majority of which are of plant origin. Modern techniques based on chemical classification of dietary CHO replaced the traditional "by difference" measurement. They provide a logical basis for grouping into categories of specific nutritional importance. The physiological effects of dietary CHO are highly dependent on the rate and extent of digestion and absorption in the small intestine and fermentation in the large intestine, interactions which promote human health. Current knowledge of the fate of dietary CHO means that the potentially undesirable properties of many modern foods could be altered by using processing techniques that yield foods with more intact plant cell wall structures. Such products would more closely resemble the foods in the pre-agriculture diet with respect to the rate of digestion and absorption of CHO in the small intestine. The potentially detrimental physiological consequences of eating sugars and starch that are rapidly digested and absorbed in the small intestine suggest that, as fibre, the form, as well as the amount of starch should be considered. Increasing consumer awareness of the relationship between diet and health has led to demands for more widespread nutrition labelling. The entry "carbohydrate" is required in most countries, and the value is usually obtained "by difference" and used in the calculation of energy content. However, the value provides no nutritional information per se. Food labels should provide values that aid consumers in selecting a healthy diet.     

Injection Moulding: Evaluation of Appropriate Melt Injection Points for the Gas Injection Technique

In gas assisted injection moulding the melt front advancement has a considerable effect on the gas penetration. The evaluation of an appropriate melt filling is an important step to avoid instabilities in the process sequence. Taking a sample moulded part a procedure is presented that enables the part designer to evaluate required melt and gas injection points according to the gas injection technique. Using finite element simulations, different calculations for the melt front advancement lead to the correct gate location.

Presentation of different degrees of filling for the optimised article geometry.     

The backward Monte Carlo method for semiconductor device simulation

A backward Monte Carlo method for the numerical solution of the semiconductor Boltzmann equation is presented. The method is particularly suited to simulate rare events. The general theory of the backward Monte Carlo method is described, and several estimators for the contact current are derived from that theory. The transition probabilities for the construction of the backward trajectories are chosen so as to satisfy the principle of detailed balance. This property guarantees stability of the numerical method and allows for a clear physical interpretation of the estimators. A symmetric sampling method which generates wave vectors always in pairs symmetric to the origin can be shown to yield zero current exactly as thermal equilibrium is approached. The properties of the different estimators are evaluated by simulation of an n-channel MOSFET. Quantities varying over many orders of magnitude can be resolved with ease. Such quantities are the drain current in the sub-threshold region, the high-energy tail of the carrier distribution function, and the so-called acceleration integral which varies over 30 orders in the example shown.