Determination of the amino acid tryptophan in protein fibres

Tryptophan can be used as an indicator amino acid for the photostability of proteins. The analysis of tryptophan and its degradation products is hampered by their instability in oxidative or strongly acidic media, or light. Various methods were employed to quantify tryptophan in wool and other protein fibres such as silk and human hair. Acid, alkaline and enzymatic methods were used to hydrolyse protein fibres. The amino acid tryptophan in wool and other protein fibres was determined by a colorimetric method, by amino acid analysis and by reversed-phase HPLC. The different analytical methods were compared with regard to their results. The colorimetric method (p-dimethylamino-benzaldehyde) proved to give reliable results for the tryptophan content in wool and unpigmented protein fibres. This method can be used also for wool dyed with acid, metal complex or reactive dyes or for pigmented keratin fibres after correction for a blank sample. Interference between dye and colorimetric reagent also have to be evaluated.     

Generation of optimal artificial neural networks using a pattern search algorithm: application to approximation of chemical systems

A pattern search optimization method is applied to the generation of optimal artificial neural networks (ANNs). Optimization is performed using a mixed variable extension to the generalized pattern search method. This method offers the advantage that categorical variables, such as neural transfer functions and nodal connectivities, can be used as parameters in optimization. When used together with a surrogate, the resulting algorithm is highly efficient for expensive objective functions. Results demonstrate the effectiveness of this method in optimizing an ANN for the number of neurons, the type of transfer function, and the connectivity among neurons. The optimization method is applied to a chemistry approximation of practical relevance. In this application, temperature and a chemical source term are approximated as functions of two independent parameters using optimal ANNs. Comparison of the performance of optimal ANNs with conventional tabulation methods demonstrates equivalent accuracy by considerable savings in memory storage. The architecture of the optimal ANN for the approximation of the chemical source term consists of a fully connected feedforward network having four nonlinear hidden layers and 117 synaptic weights. An equivalent representation of the chemical source term using tabulation techniques would require a 500 x 500 grid point discretization of the parameter space.     

Safety Assessment of Fresh and Processed Seafood Products by MALDI-TOF Mass Fingerprinting

Foodborne intoxications caused by the consumption of fish and other products of marine origin contaminated with bacterial pathogens are an ever-present threat, either due to bacteria and/or its metabolites. In addition, the rapid spoilage of seafood due to microbial activity, results in high economic losses. The development of the microbiota in seafood products depends on the microbiological ambience of capture, processing and storage, and the applied preservation method. Thus, pathogenic and spoilage bacterial species in seafood may come from the indigenous microbiota of the aquatic ambience or are introduced by contamination during processing. Rapid and accurate bacterial species identification is essential for an effective control program to ensure safety and quality of either processed or minimally processed seafood. In the present work, matrix-assisted laser desorption ionization-time of flight mass spectrometry was successfully applied to identify 26 bacterial strains isolated from fresh fish and processed seafood samples. The approach was based on the comparison of unknown spectra to a reference spectral library and demonstrated to be a fast and accurate technique for bacterial species differentiation, which can be used for the rapid identification of foodborne pathogens and spoilage bacteria potentially present in products of marine origin.     

Chemical kinetic study of a novel lignocellulosic biofuel: Di-n-butyl ether oxidation in a laminar flow reactor and flames

The combustion characteristics of promising alternative fuels have been studied extensively in the recent years. Nevertheless, the pyrolysis and oxidation kinetics for many oxygenated fuels are not well characterized compared to those of hydrocarbons. In the present investigation, the first chemical kinetic study of a long-chain linear symmetric ether, di-n-butyl ether (DBE), is presented and a detailed reaction model is developed. DBE has been identified recently as a candidate biofuel produced from lignocellulosic biomass. The model includes both high temperature and low temperature reaction pathways with reaction rates generated using appropriate rate rules. In addition, experimental studies on fundamental combustion characteristics, such as ignition delay times and laminar flame speeds have been performed. A laminar flow reactor was used to determine the ignition delay times of lean and stoichiometric DBE/air mixtures. The laminar flame speeds of DBE/air mixtures were measured in the stagnation flame configuration for a wide rage of equivalence ratios at atmospheric pressure and an unburned reactant temperature of 373 K. All experimental data were modeled using the present kinetic model. The agreement between measured and computed results is satisfactory, and the model was used to elucidate the oxidation pathways of DBE. The dissociation of keto-hydroperoxides, leading to radical chain branching was found to dominate the ignition of DBE in the low temperature regime. The results of the present numerical and experimental study of the oxidation of di-n-butyl ether provide a good basis for further investigation of long chain linear and branched ethers.     

Towards an aggregate architecture: designed granular systems as programmable matter in architecture

Aggregate architectures are full-scale spatial formations made from loose granular matter. Especially if the individual grain is custom-designed, the range of behaviours can be calibrated to match a wide range of architectural and structural performance criteria. The aggregate becomes programmable matter. The relevance of loose granular systems for architecture is on the one hand their rapid re-configurability, allowing for a system not to be destroyed but rather to be recycled. On the other hand aggregates per se can be functionally graded either within one and the same particle type or through mixing different particle geometries. This enables the variation of architectural properties throughout one and the same material system, which is one of the core postulates of current architectural design research. However, very few examples of designed granular matter in architecture exist. The results presented here are thus one of the first coherent bodies of comprehensive research in this field compiled over a period of five years. Methodologically aggregate systems challenge conventional architectural design principles: whereas an architect generally precisely defines local and global geometry of a structure, in a designed granular system he can only calibrate the particle geometry in order to tune the overall behaviour of the aggregate formation. Thus new design methods have been developed throughout the research projects, which are informed by the related fields of granular physics and behaviour-based robotics. In this context the article provides an introduction to both designed particle systems and suitable fabrication approaches in an architectural context. Case study projects serve to verify the applicability of the concepts introduced. The research findings are discussed with regards to their practical, methodological and design theoretical contributions. To conclude, further directions of research are highlighted.     

Monte-Carlo study of short-range order reactions with activated diffusion

By Monte Carlo simulations of short-range order reactions in a rigid f.c.c. A₇₅B₂₅ computer crystal, applying two diffusion mechanisms either in- or excluding an activation barrier against the vacancy migration, it is found that in both cases the same final states are approached which are the thermodynamic equilibrium states. The reaction kinetics in dependence on the number of performed vacancy steps, however, are different. – The morphology of the vacancy path is the same for both mechanisms: this path is uniformly distributed in the crystal steadily filling up the crystal volume during the reaction, thus this path does not form separated compact regions. The explanation of this behaviour is deduced from the observation that for both diffusion mechanisms the vacancy visits preferentially those lattice sites the local short-range order of which is lower than at the average whereas those sites with larger short-range order are left unvisited. Since sites with a certain degree of local short-range order are uniformly distributed over the crystal the vacancy path, following these sites, is spread in the same way.     

Zur Erniedrigung der Martensittemperatur durch inkohärente Teilchen im Austenit

Einfluß inkohärenter Phosphidteilchen in einem austenitischen Stahl mit 32,3% Ni und 0,7% P auf die M_s-Temperatur. Deutungsmöglichkeit der gefundenen M_s-Temperaturerniedrigung durch Berücksichtigung der elastischen Verzerrung an den Teilchen bei der Martensitumwandlung.     

Die kristallographischen Eigenschaften der Eisenphosphidausscheidung (Fe3P) im Ferrit

Elektronenmikroskopische und lichtmikroskopische Ermittlung des Orientierungszusammenhanges und des Habitus der Eisenphosphidteilchen (Fe₃P), die sich im Ferrit einer Eisen-Phosphor-Legierung bei 550 bis 750 °C ausgeschieden haben. Vergleich mit Ergebnissen aus dem Schrifttum.     

LL(k)-PARSING OF COUPLED-CONTEXT-FREE GRAMMARS

Coupled-context-free grammars are a natural generalization of context-free grammars obtained by combining nonterminals to corresponding parentheses which can only be substituted simultaneously. Refering to the generative capacity of the grammars we obtain an infinite hierarchy of languages that comprises the context-free languages as the first and all the languages generated by TAGs as the second element. Here, we present a generalization of the context-free LL(k) -notion onto coupled-context-free grammars, which leads to a characterization of subclasses of coupled-context-free grammars–and in this way of TAGs as well–which can be parsed in linear time. The parsing procedure described works incrementally so that it can be used for on-line parsing of natural language. Examples show that important elements of the tree-adjoining languages can be generated by LL(k )-coupled-context-free grammars.