The dynamics of innovations and development in catalyst based technologies. Catalytic reforming,cracking, and ammonia production

It is proposed that major progress in catalysis occurs in the step-wise manner. Breakthroughs which revolutionize technology occur every five to ten years. After such a breakthrough there are extended periods during which fundamental research investigating the underlying phenomena leads to better understanding and gradual improvements of the new technology. During such periods it may appear that a field or even the whole of catalytic technology is relatively mature. This is, however, a misconception because history teaches us that fields which appear mature are suddenly revitalized by a major new discovery. This is illustrated with three case histories.     

Direct evaluation of fluorescence in single renal epithelial cells using a mitochondrial probe (DASPMI)

The study of distribution and quantitation of a fluorescent probe in living epithelia with the aid of an inverted microscope requires that individual cells can be analysed without optical interference from adjacent cells. This report describes the application of fluorescence microscopy and fluorometry to a recently developed in vitro culture system of renal epithelial cells. Epithelial cells derived from the mammalian renal cortical collecting tubule (CT) and the thick ascending loop of Henle (TAL) are cultivated as continuous monolayers in serum-free, hormone-supplemented media. A specific mitochondrial marker (DASPMI) is added to the medium and incorporated into the cytoplasm. The microscopic image reveals that the mitochondrial fluorescence distribution differs between CT and TAL cultures. The fluorometric quantitation shows a normally distributed histogram of medium-range intensity in TAL cell cultures while CT cultures exhibit a two-peak pattern of mitochondrial fluorescence distribution among epithelial cells.     

Visualizing Energy Transfer at Buried Interfaces in Layered Materials Using Picosecond X‐Rays

Understanding the fundamentals of nanoscale heat propagation is crucial for next‐generation electronics. For instance, weak van der Waals bonds of layered materials are known to limit their thermal boundary conductance (TBC), presenting a heat dissipation bottleneck. Here, a new nondestructive method is presented to probe heat transport in nanoscale crystalline materials using time‐resolved X‐ray measurements of photoinduced thermal strain. This technique directly monitors time‐dependent temperature changes in the crystal and the subsequent relaxation across buried interfaces by measuring changes in the c‐axis lattice spacing after optical excitation. Films of five different layered transition metal dichalcogenides MoX₂ [X = S, Se, and Te] and WX₂ [X = S and Se] as well as graphite and a W‐doped alloy of MoTe₂ are investigated. TBC values in the range 10–30 MW m^?2 K^?1 are found, on c‐plane sapphire substrates at room temperature. In conjunction with molecular dynamics simulations, it is shown that the high thermal resistances are a consequence of weak interfacial van der Waals bonding and low phonon irradiance. This work paves the way for an improved understanding of thermal bottlenecks in emerging 3D heterogeneously integrated technologies.     

Statistical analysis and predictions of fracture and fatigue of micro-components

A number of materials typically used in MEMS technology exhibit brittle fracture behaviour which leads to a scatter in strength and a size effect as a consequence. Furthermore, some of these materials, e.g. polycrystalline silicon, show fatigue effects which limit the lifetime under cyclic loading conditions. Probabilistic methods based on the Weibull theory have been established successfully in predicting the strength of micro-components under static loading. However, the consequence of fatigue on reliability predictions has not yet been studied extensively. We present strength as well as lifetime predictions for poly-silicon components with stress concentrations based on experimental data published in the literature. Our results show that while strength predictions for components with stress concentrations based on scaling procedures works well, lifetime prediction is a challenging task associated with large prediction uncertainties. Finally, we relate the crack propagation approach used for our lifetime predictions with micro-mechanical fatigue models that are discussed for poly-silicon.     

Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.     

Thermal conductivity measurement with a free floating molecule detector

“Zero‐pressure” elimination with Pirani principle for vacuum measurement and increase of the measurement range limit of thermal gas‐sensors and flow sensors Measurement of pressure in the medium vacuum range has been done via thermal conductivity. The literature on the Pirani principle has defined a lower range limit — the so‐called “zero pressure” until now [1]. The minimum power needed to hold a sensor up to operating temperature exceeds the useful signal, due to the conductivity of the sensor mounting and the resulting heat loss through the suspension. The author was able to eliminate the “zero pressure”, thereby expanding the measurement range of Pirani sensors significantly downwards. Measurement results confirmed an extension of the measurement range of two decades downwards with the coiled Pirani. Also with other sensors that use thermal conductivity and heatentrainment effects, e.g. gas sensors and sensors for flow measurement, the new principle can be applied and thus lower the lower range limit.     

The behaviour of styrenes p-substituted with a liquid crystalline side group under anionic polymerization conditions

Summary The synthesis of p-alkyloxymethylstyrenes and p-alkyloxystyrenes with 4,4-disubstituted-biphenyl or 2,5-disubstituted-1,3-dioxane groups as side chains are described. The phase behaviour of both the monomers and polymers obtained by free radical polymerizations is investigated.The monomers are not suitable for living anionic polymerizations because of the side reactions which occur as competitive reactions to the normal chain growth. The benzylic ether group of the alkyloxymethylstyrene was splited under the influence of the anionic centres. A metalation of the phenyl ring of the styryl group was observed for alkyloxystyrenes.