Strain-induced internal fibrillation in looped aramid filaments

By mapping the small-angle X-ray scattering (SAXS) from a looped poly-(para-phenylene terephtalamide) (aramid, PPTA) filament using a synchrotron X-ray microbeam, we investigate the effects of axially compressive and tensile strain on internal fibrillar structures. Unique observations of oscillations in the highly anisotropic SAXS patterns indicate a regular internal structure. Upon increase of the applied compressive strain, a significant decrease in oscillation frequency is observed in the scattering pattern. With an increase in imposed tensile strain an increase in oscillation frequency in the scattering pattern is observed. One model capable of describing the intensity is a model of stacked cylinders. These cylinders could be part of the fibrillar structure present in the PPTA fibres, which consist of cylinder- to tape-like objects, the presence of which is supported by SEM images. One hypothetical physical interpretation presented here for the appearance of a regular internal structure is the occurrence of fibrillar separation in regions undergoing axially compressive strain, and the appearance of strain relief/slip planes between packs of fibrils in regions undergoing tensile strain. Compaction of these packs upon increase of tensile strain could increase the repetition distance in the structure as multiple packs combine to form a single pack.     

Hydro reservoir handling in Norway before and after deregulation

The Norwegian Energy Act that came into force in 1991 deregulated the electricity market and removed the former obligation power companies had to supply electricity to the geographical area they were responsible for. Hence producers can supply electricity on the basis of profitability. In 2007 the Energy Act was evaluated by the Government. As a part of this, a study concerning hydro reservoir handling before and after deregulation was carried out by SINTEF. Public statistics show that average hydro reservoir levels measured in per cent of reservoir capacity have been reduced after 1990. We have used the power-market model EMPS¹ (EFI's Multi-area Power-market Simulator) to analyze if this reduction can be explained by natural variation in climatic variables or by structural changes that have occurred after 1990. Simulation results show that the reduced reservoir levels cannot be explained by natural variation in climatic variables. Structural changes such as increased transmission capacities can, however, explain some of the reduction. Our study does not indicate that the present reservoir handling gives reservoir levels that are too low. In this paper we also describe the stochastic dynamic optimization problem for long-term hydropower scheduling, and we explain how this problem actually is solved by the EMPS model.     

<Superscript>31</Superscript>P NMR quantification and monophasic solvent purification of human and bovine lens phospholipids

Most lipid extraction procedures [Folch, J., Lees, M., and Sloane-Stanley, G.H., (1957) A Simple Method for the Isolation and Purification of Total Lipids from Animal Tissues, J. Biol. Chem. 226, 497–509; Bligh, E.G., and Dyer, W.J. (1959) A Rapid Method of Total Lipid Extraction and Purification, Can. J. Biochem. Physiol. 37, 911–917] employ biphasic solvent mixtures designed to dissolve the lipids in an organic phase and remove impurities in an aqueous phase. However, when applying these protocols to biological matrices such as that of the ocular lens, the formation of an emulsion layer between the organic and aqueous phases causes poor reproducibility in extraction yields and gives only a small amount of the lipid-containing chloroform phase. In this study, we quantified phospholipids at each step of the Folch et al. extraction protocol and compared the yield of human and bovine lens phospholipids obtained by the Folch-based approach and a novel monophasic methanol extraction method designed to circumvent the problems associated with biphasic extraction protocols. A monophasic methanol extraction coupled with ³¹P NMR spectroscopy was found to be the simplest, quickest, and most effective method for quantifying the phospholipid content of the lens.     

FEM Study of Fatigue Response of 3‐Sheet Spot Welded Joints

The commercial software used for predicting fatigue strength for load‐carrying spot welds in sheet structures, like car bodies, is mainly developed for two‐sheet joints. The purpose of this work was to study the fatigue properties of three‐sheet spot welded joints with a dimensioning method used in the automotive industry and to compare such computational results to those obtained from a more accurate method and to experimental data. Eleven three‐sheet, single spot welded specimens were studied using a structural stress approach, followed by shell element simulations, similar to those used in commercial software. These results were compared to calculations based on fine meshed solid element models. Fracture mechanics was used to evaluate the loading conditions at the spot welds. Comparison between the results from the different methods and experimental results for three shear loaded specimens, consisting of triple sheets, found in literature showed good correlation. The shell element method in shear loaded cases gives stress intensities within +35% to ‐5% of the solid element method results. In peel loaded cases the results differ up to ‐60%, an under‐estimation that leads to an increase of estimated fatigue life up to 65 times.     

Graph Searching, Elimination Trees, and a Generalization of Bandwidth

The bandwidth minimization problem has a long history and a number of practical applications. In this paper we introduce a natural extension of bandwidth to partially ordered layouts. We consider this extension from three main viewpoints: graph searching, tree decompositions, and elimination orderings. The three graph parameters pathwidth, profile, and bandwidth related to linear layouts can be defined by variants of graph searching using a standard fugitive. Switching to an inert fugitive, the two former parameters are extended to treewidth and fill-in, and our first viewpoint considers the analogous tree-like extension that arises from the bandwidth variant. Bandwidth also has a definition in terms of ordered path decompositions, and our second viewpoint extends this in a natural way to ordered tree decompositions. In showing that both extensions are equivalent we employ the third viewpoint of elimination trees, as used in the field of sparse matrix computations. We call the resulting parameter the treespan of a graph and prove some of its combinatorial and algorithmic properties.     

Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts

Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the ammoxidation of propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers. Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions. The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective, cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original, fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C₃H₈ + NH₃ reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved in the catalytic ammoxidation process. Therefore, the ammoxidation of paraffins is a redox process, as is of course the well-known olefin ammoxidation process.     

The presence of Penicillium and Penicillium mycotoxins in food wastes

A total of 97 samples (48 summer and 49 winter) of food waste from private households were investigated for Penicillium and for mycotoxins. Twenty-five Penicillium species were isolated and Penicillium crustosum, Penicillium brevicompactum, Penicillium chrysogenum, Penicillium expansum, Penicillium roqueforti, Penicillium spinulosum, Penicillium viridicatum, Penicillium commune, Penicillium citrinum and Penicillium solitum were, in decreasing order, the most frequently identified species. Mycotoxins produced by several of these species, including mycophenolic acid, roquefortine C, penitrems A-F and thomitrems A and E, were detected. Of the 48 summer samples, 36 were severely infected and contained more than 10(5) colony forming units (CFU) Penicillium/g sample. The levels of mycotoxins in these samples were in the range 75-19000 microg/kg mycophenolic acid, 40-920 microg/kg roquefortine C, 35-7500 microg/kg penitrem A, 20-2100 microg/kg thomitrem A and 20-3300 microg/kg thomitrem E. Of the 49 winter samples, only one was found to contain mycophenolic acid (4800 microg/kg) and roquefortine C (190 microg/kg), and this sample was severely infected with P. roqueforti. Thirty samples of food waste collected from the food manufacturing industry were also investigated. The number of Penicillium in these samples was between 10(5) and 10(6) colony forming units (CFU)/g sample. Seven of these samples contained mycophenolic acid ranging from 50 to 600 microg/kg and three of these samples also contained roquefortine C in the range 100-250 microg/kg.