Controlled formation and mixing of two-dimensional fluids

We introduce a novel technique for the controlled spreading and mixing of lipid monolayers from multilamellar precursors on surfaces covered by the hydrophobic epoxy resin SU-8. The lipid spreads as a monolayer as a result of the high surface tension between SU-8 and the aqueous environment. A micropatterned device with SU-8 lanes, injection pads, and mixing regions, surrounded by hydrophilic Au, was constructed to allow handling of lipid films and to achieve their mixing at controlled stoichiometry. Our findings offer a new approach to dynamic surface functionalization and decoration as well as surface-based catalysis and self-assembly.     

Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified Phosphonic Acid Self‐Assembled Monolayers

Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers.     

Development and evaluation of chitosan and chitosan derivative nanoparticles containing insulin for oral administration

Abstract

Chitosan and chitosan derivative-based nanoparticles loaded with insulin were prepared by self-assembly, via electrostatic interactions between the negatively charged drug and the positively charged polymers. In the investigated chitosan derivatives, the amine groups were substituted to different extents (33, 52 or 99%) by 2-hydroxypropyl-3-trimethyl ammonium groups, rendering the polymers permanently positively charged, irrespective of the pH. This is an important property for this type of advanced drug delivery system, since the pH value changes throughout the gastrointestinal tract and electrostatic interactions are of crucial importance for the stability of the nanoparticles. Permanent positive charges are also in favor of mucoadhesion. In contrast, the electric charges of chitosan molecules depend on the pH of the surrounding medium. Since the solubility of the chitosan derivatives increased due to the introduction of quaternary ammonium groups, sodium tripolyphosphate (TPP) was added to the systems to create supplementary cross-links and stabilize the nanoparticles. The presence of TPP influenced both the dissolution of the polymer matrix as well as the resulting release kinetics. The underlying drug release mechanisms were found to be more complex than simple diffusion under constant conditions, likely involving also ionic interactions and matrix dissolution. The most promising formulation was based on a chitosan derivative with 33% substitution degree and characterized by a Z-average of 142?±?10?nm, a zeta potential of 29?±?1?mV, an encapsulation efficacy of 52?±?3% and, most importantly, the release of insulin was sustained for more than 210?min.     

Systematische vergleichende Kostenanalyse von destillativen und extraktiven Stofftrennverfahren

Systematic Comparative Cost Analysis of Separation Processes Based on Distillation and Extraction . Rectification is the most commonly used but not always the most economical method of thermal separation. Above all in the case of closely boiling mixtures it becomes very demanding with regard to both equipment and energy. It is often possible to replace rectification by another energetically more favourable separation process such as liquid-liquid distillation, decantation, or absorption. Owing to the resulting wealth of possibilities for the separation of a mixture it is desirable to gain further knowledge about the economics of individual processes and about the selection of suitable entrainers under given conditions.     

Peas starch‐based film coatings for site‐specific drug delivery to the colon

Peas starch : ethylcellulose‐based film coatings are proposed allowing for site‐specific drug delivery to the colon of inflammatory bowel disease patients. The film coatings are poorly permeable for 5‐aminosalicylic acid in media simulating the contents of the stomach and small intestine. Thus, they can minimize premature drug release in the upper gastrointestinal tract and subsequent absorption into the blood stream. However, once the colon is reached, drug release sets on and is time controlled. This can be attributed to the partial degradation of the peas starch by enzymes secreted by bacteria, which are preferentially present in the colon. Thus, the drug is released at the site of action, which is likely to minimize undesired side effects in the healthy part of the human body and to optimize the therapeutic efficacy of the treatment. A blend ratio of 1 : 4 peas starch : ethylcellulose and a coating level of 15% (w/w) seem to be optimal for pellet coating. Importantly, the polymeric films can be expected to withstand the mechanical stress encountered in vivo because of the motility of the stomach and small intestine. Furthermore, the systems are long‐term stable: drug release from coated pellets remains unaltered during 1‐year open storage. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Application of simulation-based decision making in product development of an RF module

This paper presents results of simulation-based design evaluation for thermal and thermo-mechanical performance and cost of packaging technology of a RF module for automotive application. Combination of thermal, thermo-mechanical and cost analysis within the multi-attribute decision making enabled design ranking and revealed two MCM-L/D and MCM-D designs with wire bonding assembly preferred for use in automotive applications for different temperature environments. Simulation-based design guidelines were developed for designing electronic modules exhibiting good thermal and thermo-mechanical performance. By application-based partitioning of the importance weights assigned to the reliability and cost criteria, the guidelines were extended to cover other application areas.     

Phenotypical Conversions of Dermal Adipocytes as Pathophysiological Steps in Inflammatory Cutaneous Disorders

Adipocytes from the superficial layer of subcutaneous adipose tissue undergo cyclic de- and re-differentiation, which can significantly influence the development of skin inflammation under different cutaneous conditions. This inflammation can be connected with local loading of the reticular dermis with lipids released due to de-differentiation of adipocytes during the catagen phase of the hair follicle cycle. Alternatively, the inflammation parallels a widespread release of cathelicidin, which typically takes place in the anagen phase (especially in the presence of pathogens). Additionally, trans-differentiation of dermal adipocytes into myofibroblasts, which can occur under some pathological conditions, can be responsible for the development of collateral scarring in acne. Here, we provide an overview of such cellular conversions in the skin and discuss their possible involvement in the pathophysiology of inflammatory skin conditions, such as acne and psoriasis.     

A new model for the propagation of jets in dilute gas‐solid crossflows

The three‐dimensional propagation of a horizontal gas jet injected into a gas‐solid crossflow is described by a model based on the mass and momentum balances for both phases. The potential core close to the nozzle, the kidney‐shaped cross‐section of the jet and the region of rapidly increasing jet volume are taken into account. Viscous and turbulent stresses within the gas phase as well as the momentum exchange with the solid phase are considered. Several parameters are determined empirically by experimental data obtained by measurements in a dilute circulating fluidized bed. The comparison of calculated with experimental data shows good agreement concerning the shape of the jet axis and the solid phase concentration.