Eigenvalue Approach for Computing the Reliability of Markov Systems

This paper solves the computation of the reliability of Markov systems. The solution is especially useful for systems where the number of states is large. Not only is the mean time-to-failure computed but an analytic expression is given for the probability of the system's being in a certain state as a function of time. The solution is derived by solving the eigenvalues and eigenvectors of the transitionrate matrix of the Markov system. In the solution, numerical algorithms have been chosen to keep the computer cost down. The method uses just a fraction of the time that, for example, the Runge-Kutta method uses.     

Aroma analysis of apple juice: Influence of salt addition on headspace volatile composition as measured by gas chromatography and corresponding sensory evaluations

Sensory response to the aroma of a food depends on the composition and concentrations of the volatiles of the headspace. When analyzing the headspace composition by gas chromatography, salts are often added to the sample as a means of increasing the concentration of the aroma compounds in the vapor phase (e.g. enrichment of the vapor phase). This will only give a correct impression of the original aroma when all volatile components are affected equally. In this study on apple juice aroma, it is demonstrated that the degree of headspace enrichment resulting from salt addition is different for esters, aldehydes and alcohols, In our collection system, the average degree of enrichment at 40°C (described in terms of Relative Peak Areas—RPA) was greater than 4 for alcohols, between 1·75 and 3·50 for aldehydes and less than 1·75 for esters. How these differences can be useful when trying to identify gas chromatography peaks is also discussed.Sensory evaluations showed that aroma response is changed when salt is added to the juice, resulting in an increased aroma intensity and off-aroma. Fruit aroma was not affected. A comparison of the sensory responses with headspace gas chromatographic measurements indicates that increase in off-aroma can be related to the increase in alcohol percentage in the headspace.From these results it can be noted that, when attempting to correlate sensory scores with aroma component concentrations as measured by headspace gas chromatography, it is most important that the test conditions utilized for each analysis correspond as closely as possible with each other.     

Oxidation of methionine. Effects of hydrogen peroxide alone and in combination with iodide and selenite

The oxidation of methionine by hydrogen peroxide, and the influence of iodide, pH, amino acids and selenite were studied with free methionine and with casein and fish fillet protein. The concentration levels tested ranged from 0·05 mm to 3·0 mm. Hydrogen peroxide oxidation was not influenced by pH in the range 5·0 to 8·0; at pH 8·5 the rate of oxidation was increased. When iodide was added in amounts equivalent to or less than the amounts of H₂O₂, the reaction was accelerated with free but not protein-bound methionine. At higher levels iodide inhibited the oxidation. An amino acid mixture and proteins inhibited the effect of iodide; this effect seemed to be due to tryptophan. Selenite also accelerated the effect of H₂O₂, both with free and with protein-bound methionine. Cu⁺⁺ catalysed the oxidation by H₂O₂ at low reactant concentration but not at the higher levels. The reaction between methionine and H₂O₂ seemed to be of first order with respect to both reactants.     

Visualization of solvation structures in liquid mixtures

Spatial distribution functions of atomic densities, SDFs, have been proposed as a natural starting point for analysis of local molecular structure in liquids and solutions. The local structure in these systems is often complex and this is reflected in the fact that SDFs can be difficult to visualize. Among the different methods that can be used to visualize SDFs we discuss 3D isodensity surfaces, cross-sections, and ‘comic book’ animations. We also discuss the possibility of a simultaneous visualization of SDFs and other 3D fields, such as the electron density. These techniques are all intended to emphasize and bring out aspects of SDFs that promote a further understanding of the local molecular structure. OpenGL-based software has been used under X-Windows to implement these techniques, and we argue that high-quality molecular graphics need not be expensive. Data from a molecular dynamics simulation of an equimolar binary mixture of water and acetonitrile have been used to illustrate the discussion.     

Hot Isostatically Pressed Alumina-Silicon Carbide-Whisker Composites

Alumina-silicon carbide-whisker composites were hot isostatically pressed at 1550°C and 200 MPa for 1 h. The silicon carbide whiskers were treated in different acid and gas environments before they were pressed. All samples exhibited linear elastic behavior with no ductility tendency. Improved strength and fracture toughness were obtained compared with unreinforced alumina. Mechanisms for the improved mechanical properties are discussed. These include grain growth control, whisker encapsulation of defects, and related stress relief at the defect.     

Biodegradation of Pharmaceutical Compounds and their Occurrence in the Jordan Valley

In particular in arid regions the reuse of waste water and aquifer recharge is an important issue. Elimination of persistent emerging pollutants represents a key factor in integrated water resources management, and identifying suitable treatment processes to eliminate such compounds becomes inevitably necessary. It is the objective of this study (1) to assess the occurrence of emerging pollutants in the Jordan Valley and (2) to review and examine the biodegradability of selected key compounds. Among the most frequently detected compounds during a sampling campaign in 2007 were pharmaceutical residues such as carbamazepine, diclofenac, or naproxen, and X-ray contrast agents such as diatrizoic acid and iopromide, all typically found in Europe and the USA as well. To gain further insight into elimination processes, biodegradation studies were conducted with batch tests and flow-through soil columns under unsaturated, aerobic conditions. Results demonstrated biodegradation for pharmaceutical residues such as ibuprofen, diclofenac and bezafibrate. The degradation rate was faster in treated waste water as compared to raw waste water, most probably due to competing substrate consumption in raw waste water. The antiepileptic carbamazepine showed no degradation in the batch tests and only moderate removal during soil passage, probably due to sorption. The results of this study and previously published data emphasize the need for further studies under more defined conditions to elucidate the specific conditions under which biodegradation of emerging pollutants proceeds.     

A sketching interface for feature curve recovery of free-form surfaces

In this paper, we present a semi-automatic approach to efficiently and robustly recover the characteristic feature curves of a given free-form surface where we do not have to assume that the input is a proper manifold. The technique supports a sketch-based interface where the user just has to roughly sketch the location of a feature by drawing a stroke directly on the input mesh. The system then snaps this initial curve to the correct position based on a graph-cut optimization scheme that takes various surface properties into account. Additional position constraints can be placed and modified manually which allows for an interactive feature curve editing functionality. We demonstrate the usefulness of our technique by applying it to two practical scenarios. At first, feature curves can be used as handles for surface deformation, since they describe the main characteristics of an object. Our system allows the user to manipulate a curve while the underlying non-manifold surface adopts itself to the deformed feature. Secondly, we apply our technique to a practical problem scenario in reverse engineering. Here, we consider the problem of generating a statistical (PCA) shape model for car bodies. The crucial step is to establish proper feature correspondences between a large number of input models. Due to the significant shape variation, fully automatic techniques are doomed to failure. With our simple and effective feature curve recovery tool, we can quickly sketch a set of characteristic features on each input model which establishes the correspondence to a pre-defined template mesh and thus allows us to generate the shape model. Finally, we can use the feature curves and the shape model to implement an intuitive modeling metaphor to explore the shape space spanned by the input models.