Periodic reactive flow simulation: Proof of concept for steam cracking coils

Streamwise periodic boundary conditions (SPBCs) have been successful in reducing the computational cost of simulating high aspect ratio processes. Extending beyond the classic assumptions of constant property flows, a novel approach incorporating non‐equilibrium kinetics was developed and implemented for the simulation of an industrial propane steam cracker. Comparison with non‐periodic benchmarks provided validation as relative errors on the main product yields were consistently below 1% for different reactor configurations. A further order‐of‐magnitude reduction of the radial errors on product concentrations was obtained via an intuitive correction method based on the concept of local fluid age. The computational speedup achieved through application of SPBCs was a factor 16–250 compared to the non‐periodic simulations. The presented methodology thus serves as a quick screening tool for the development of novel reactor designs and unlocks the potential for using more elaborate kinetic models or a more fundamental approach toward turbulence modeling. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1715–1726, 2017     

Square Foot Manufacturing: a new production concept for micro manufacturing

Today a large number of microstructures are already employed as separate components or as constituents of larger modules in a broad spectrum of production in medical technology, optics, biotechnology, mechatronics, fluidics, (micro)-forming and tool construction. Current research activities are directed towards the downscaling of manufacturing procedures or the formation of complex process chains for the manufacture of micro workpieces. The Square Foot Manufacturing concept represents one approach aimed at achieving significant technical, economic and ecological developments in the production of microstructures by means of machining techniques that can be applied to a spectrum of materials as broad as possible. This fabrication concept representing a refinement of existing desktop manufacturing concepts is currently being developed at the Institute of Production Engineering of Helmut-Schmidt-University/University of the Federal Armed Forces Hamburg. This paper is intended to provide an overview of the theoretical concept and the current state of its technical implementation.     

Continuous generating grinding—Tooth root machining and use of CBN-tools

Profile accuracy, no burning and residual compressive stresses at the tooth root fillet are required for the durability of highly stressed gears. This paper reveals the challenges for continuous generating grinding with corundum and CBN. For this purpose, material removal simulations and experimental investigations were carried out to gain knowledge of the tool–workpiece contact conditions. The potential of CBN tools was analysed due to the fact that the mechanical loads at the grinding worm tip result in high profile wear of the corundum tools. In this context, especially the interrelationship between the dressing strategy and the workpiece quality was investigated in detail.     

Lipozyme IM‐catalyzed interesterification for the production of margarine fats in a 1 kg scale stirred tank reactor

Lipozyme IM‐catalyzed interesterification of the oil blend between palm stearin and coconut oil (75/25 w/w) was studied for the production of margarine fats in a 1 kg scale batch stirred tank reactor. Parameters such as lipase load, water content, temperature, and reaction time were investigated. The reusability of Lipozyme IM was also studied under optimized conditions. The interesterification products were monitored by analysis of triacylglycerol profiles, the contents of diacylglycerols, free fatty acids (FFA), and solid fat contents. The contents of some triacylglycerol species, which were categorized by equivalent carbon number (ECN), namely ECN34, 36, 48, and 50, decreased by 6.0, 5.9, 5.8, and 13.7%, respectively, after enzymatic interesterification, similar to the reduction of those species after chemical interesterification, 6.6, 6.0, 7.1, and 12.9%, respectively. On the other hand, those of ECN38, 40, 42, 44, and 46 increased by 1.1, 1.6, 6.8, 16.7, and 6.5%, respectively, in comparison with the increase of those species after chemical interesterification, 0.2, 1.5, 6.5, 17.0, and 9.2%, respectively. Lipase load and reaction time had great influence on the degree of interesterification. A Lipozyme IM load of 6% was required for a reaction of 6 h and at 60 °C, to reach a stable degree of interesterification. Temperature variation in the range of 50—75 °C did not affect the reaction degree as well as the contents of diacylglycerols, but the content of FFA slightly increased with higher temperature. Addition of water to the enzyme increased the contents of diacylglycerols and FFA in the products linearly. However, it had no effect on the degree of interesterification for the first batch when the enzyme was reused. Lipozyme IM was stable in the 10‐batch test after adjusting the water content in the system. The relationship between the content of water in the system and that of FFAs in the products was evaluated and discussed.     

Synthesis and structural studies of “branched” 2-linked trisaccharides related to h-type 2 blood group determinants

A series of fucosylated trisaccharides l-Fuc-(1→2)-ß-d-Gal-(1→4)-ß-X-OMe (1-6, X = d-GlcNAc, d-Qui (6-deoxy-Glc), d-Xyl) related to H type 2 blood group determinant have been synthesized both as their α- and ß- L-Fuc anomers together with the component disaccharide starting compounds (7-11). The conformational properties of the trisaccharides together with their parent disaccharides have been investigated by NMR spectroscopy (proton and carbon chemical shifts and proton NOEs) in combination with computer modeling using the Monte Carlo approach and the HSEA force field using the GEGOP program with the main focus on the α-linked fucose series. The series of compounds allow for the investigation of interaction between the sugar units in the—in principle—linear structures, which in practice behave as branched trisaccharides. The interaction between the terminal fucose unit and the unit at the reducing end has been probed by substitution of the bulky CH₂OH group with CH₃ and H substituents, respectively. Compounds with severe steric interactions can be identified by the non-additivity of their carbon chemical shifts and subsequently confirmed by the detailed conformational assessment by NOEs and computer modeling. The most severe contacts arise in the GlcNAc and Qui trisaccharide series, whereas the Xyl-containing trisaccharide derivatives only exhibit weak steric interaction as probed by the NMR parameters.     

Sintering Mechanisms of Zirconium and Hafnium Carbides Doped with MoSi2

The microstructure of two pressureless-sintered ultra-high-temperature ceramics, namely ZrC+20 vol% MoSi₂ and HfC+20 vol% MoSi₂, was characterized by scanning and transmission electron microscopy. With regard to the ZrC–MoSi₂ system, Zr _x Si _y compounds and SiC were detected. In the HfC–MoSi₂ system, a mixed phase was detected at the triple points and identified as (Mo,Hf)₅Si₃. For both the systems investigated, the high wettability of the silicide-based phases on the matrix grains suggests that sintering is assisted by a liquid phase. This contribution reports for the first time on the sintering mechanisms of early transition metal carbides doped with MoSi₂ as a sinter additive, on the basis of the microstructural evolution observed upon sintering and in the light of phase diagrams and thermodynamical calculations.     

Small‐Molecule Targeting of the Mitochondrial Compartment with an Endogenously Cleaved Reversible Tag

Reversible mitochondrial shuttle : A novel concept in mitochondrial pharmacology allows the transport of bioactive compounds into the mitochondrial compartment and their subsequent release. A lipoic acid derivative containing a cleavable (“reversible”) triphenylphosphonium tag is endogenously cleaved by the mitochondrial aldehyde dehydrogenase (ALDH‐2) after mitochondrial accumulation.

     

Pharmacological Promiscuity: Dependence on Compound Properties and Target Specificity in a Set of Recent Roche Compounds

What parameters determine promiscuity? A compound's potential for promiscuity (pharmacological activity at multiple targets) may be influenced by molecular parameters such as ionization state, lipophilicity, and molecular weight. In an analysis of recent Roche compounds we found that a positive charge is an important determinant for potential promiscuity; aminergic activity was found to be the main reason for overt promiscuity.