Challenges and Progress in High‐Throughput Screening of Polymer Mechanical Properties by Indentation

Depth‐sensing or instrumented indentation is an experimental characterization approach well‐suited for high‐throughput investigation of mechanical properties of polymeric materials. This is due to both the precision of force and displacement, and to the small material volumes required for quantitative analysis. Recently, considerable progress in the throughput (number of distinct material samples analyzed per unit time) of indentation experiments has been achieved, particularly for studies of elastic properties. Future challenges include improving the agreement between various macroscopic properties (elastic modulus, creep compliance, loss tangent, onset of nonlinear elasticity, energy dissipation, etc.) and their counterpart properties obtained by indentation. Sample preparation constitutes a major factor for both the accuracy of the results and the speed and efficiency of experimental throughput. It is important to appreciate how this processing step may influence the mechanical properties, in particular the onset of nonlinear elastic or plastic deformation, and how the processing may affect the agreement between the indentation results and their macroscopic analogues.     

Actual versus apparent within cell wall variability of nanoindentation results from wood cell walls related to cellulose microfibril angle

Hardness and elastic modulus of spruce wood cell walls parallel to their axial direction were investigated by means of nanoindentation. In the secondary cell wall layer S2 of individual earlywood and compression wood tracheids, a systematic pattern variability was found. Several factors potentially affecting nanoindentation results were investigated, i.e. specimen orientation related to the indenter tip, cutting direction during specimen preparation, tip geometry, specimen and fibre inclination, respectively, and finally micro fibril orientation. Mechanical property measurements were correlated with structural features measured by confocal Raman spectroscopy. It was demonstrated that very high variability in the measurement of micromechanical cell wall properties can be caused by unintentional small fibre misalignment by few degrees with regard to the indentation direction caused by sub-optimal specimen preparation.     

Iron impregnation on the amorphous shell of vapor grown carbon fibers and the catalytic growth of secondary nanofibers

Vapor grown carbon fibers (VGCFs) with diameters of several microns were synthesized and investigated by high resolution transmission electron microscopy. It was found that the shell of the VGCFs consisted of densely-packed domains embedded in loosely-packed matrix, and both were highly amorphous. Regular edge planes as observed on the surface of fishbone nanofibers do not exist on VGCFs. Hence, surface treatment is more important for the deposition of catalysts. Ammonium ferric citrate (AFC) was employed for the impregnation of iron, where the high viscosity of the aqueous solution of AFC is beneficial. Calcination was found to be a key step to improve the dispersion of the iron particles, which can be attributed to enhanced interactions between iron and carbon due to the gasification of carbon occurring at the iron–carbon interface. Quantitative analysis by X-ray photoelectron spectroscopy showed that the calcination of the supported AFC led to a higher atomic concentration of iron on the surface, indicating smaller particle size and a higher dispersion. Secondary carbon nanofibers were grown subsequently on the VGCFs from cyclohexane. The specific surface area was enhanced considerably, from less than 1 m² g^? 1 to 106 m² g^? 1 after the growth of the secondary nanofibers. The obtained composites are promising materials as structured support in heterogeneous catalysis.     

Evaluation of Performance of Diesel Particulate Filters Through Integrated Multi-Scale Computer Calculations

Wall-flow channel models and soot deposition models based on micro scale considerations are integrated into global 3D diesel particulate filter simulations. In addition, transient and steady-state simulations are combined to understand at the same time short- and long-time behaviour of the diesel particulate filter (DPF). The functionality of the simulation tool is achieved and correlations with measured data encourage the use of the model as a tool to predict DPF behaviour.     

Hydraulic linkage of a storm water tank to a karst spring (Gallusquelle)

Grundwasser - A significant proportion of the global water supply is ensured by karst aquifers. However, these are often highly vulnerable to contamination. A storm water tank...     

Species composition and plant traits: Characterization of the biogeomorphological succession within contrasting river corridors

Plant communities and dynamics can be characterized according to species composition or plant traits. Here, we used species composition and plant traits to compare their effectiveness in discriminating the biogeomorphological (involving reciprocal feedbacks between physical and biological processes) and ecological (mainly biologically driven) phases of the fluvial biogeomorphological succession (FBS) model. The comparison was done between two French rivers, the largely unchannelized lower Allier and the channelized middle Garonne. One reach representative of each river section was selected for the study. Within each river reach, we chose two contrasted study sites in terms of channel and floodplain dynamics: a reference site (least altered channel and floodplain dynamics) and an altered site (laterally stabilized by riprap and constrained). In the four study sites, we sampled vegetation in 402 plots of 4 m². The 512 species identified in the plots were characterized in terms of plant traits (20) from a literature review. When comparing reaches in unconstrained ordinations and permutational multivariate analyses of variance, both species composition and plant traits led to a similar identification of the biogeomorphological and the ecological successional trajectories. Nevertheless, the trait approach was less influenced by local and regional bioclimatic, hydrogeomorphological, and anthropogenic settings and thus produced a more comprehensive and general classification of the biogeomorphological and ecological phases of the FBS model. A lower than expected contrast between the four sites was found, because neither species composition nor plant traits could entirely characterize distinct successional trajectories occurring in our reference or altered sites. Furthermore, our results contributed to a better understanding of the multiple successional trajectories that can occur in midlatitude river corridors. It also showed that relating plant traits to their effects on fluvial landform dynamics remains a core challenge in explaining succession including feedback mechanisms between hydrology, morphodynamics, and vegetation dynamics.     

Comparison of isolation procedures for essential oils

Summary The influence of the time of distillation on the composition of the essential oils isolated from seed of ajowan, caraway, coriander, and cumin was investigated. The oils were isolated by distillation, as well as by simultaneous distillation-extraction. It was observed that the order of recovery of the oil constituents was determined by their solubility in the distillation water. Hence, the oxygenated compounds, although with higher boiling points, distilled before the hydrocarbons. In comparison, data are included for the oils obtained by solvent extraction from ground seed of the same species. In these cases the proportion of hydro carbons was higher than in the distilled oils. There was also evidence to suggest thatp-cymene in the oils of ajowan and cumin was partly an artefact of distillation.

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Vergleich von Isolierungsverfahren ätherischer ÖleII. Ajowan, Künunel, Koriander und Kreuzkümmel

Zusammenfassung Der Einfluß der Destillationsäuer auf die Zusammensetzung der ätherischen Öle von Ajowan, Kümmel, Koriander und Kreuzkümmel wurde untersucht. Die Öle wurden sowohl durch Destillation als auch durch ein Destillation-Extraktionsverfahren isoliert. Es wurde gezeigt, daß die Reihenfolge der Ölbestandteile während der Destillation bestimmt wurde von ihrer Löslichkeit im Destillationswasser, weshalb die höher siedenden sauerstoffhaltigen Komponenten schneller als die Kohlenwasserstoffe übergehen.Zum Vergleich wurden Angaben aufgenommen für Öle, die mit organischen Lösungsmitteln aus gemahlenen Früchten extrahiert worden waren. In diesen Fällen war die Menge der Kohlenwasserstoffe höher als bei den destillierten Ölen. Es gibt Hinweise dafür, daßp-Cymol in Ajowan- und Kreuzkümmelöl teilweise ein Artefakt der Destillation ist.

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Part I: Chem. Mikrobiol. Technol. Lebensm. (in press)