Aggregation of experiments for estimation of hydrogen permeability parameters

The study of the hydrogen permeability of materials employs a variety of methods with their own specific features, advantages and drawbacks. The penetration method allows determining the diffusion coefficient from so-called lag time. The accuracy of the estimation depends on the degree of proximity to the DLR (diffusion limited regime) mode. The method of ‘communicating vessels’ is more sensitive to surface processes. ‘Separate’ application of these methods leads to a situation where the materials studied are in fact somewhat different (for example, due to different impacts on the surface), and significant differences in parameter estimates ensue. This paper suggests and implements a cascade experiment technique and the corresponding mathematical toolkit. The informative capacity of experimental studies and the accuracy of the estimation of hydrogen permeability parameters (diffusion, absorption, desorption) are thus enhanced.     

Determination of size and concentration of gold nanoparticles from extinction spectra

Extinction spectra of colloidal gold can be used for a simple and fast determination of the size and concentration of nanoparticles. It is generally accepted that experimental correlations of the particle size and concentration with the plasmon resonance properties are in agreement with Mie theory simulations. Here, we discuss this point in the context of a long-term collection of published experimental data and our T-matrix simulations, which account for deviations of the particle size from ideal monodisperse spheres. These deviations result in small but quite evident disagreements between the Mie calculations and the experimental calibration curves "particle size vs resonance wavelength". We present a long-term-averaged analytical particle-size calibration and also discuss the effects of the particle dielectric functions, shape and size polydispersity on simulated correlations between the extinction spectra and the average particle size, and concentration.     

Phase transitions and thermodynamic properties of dense assemblies of truncated nanocubes and cuboctahedra

Inspired by recent advances on the self-assembly of non-spherical nanoparticles, Monte Carlo simulations of the packing and thermodynamic properties of truncated nanocubes and cuboctahedra have been performed. The ergodicity problem was overcome by a modified Wang-Landau entropic sampling algorithm and equilibrium structural and thermodynamic properties were computed over a wide density range for both non-interacting and interacting particles. We found a structural transition from a simple cubic to a rhombohedral order when the degree of truncation exceeds a value of 0.9.     

Advances in reflective oxygen saturation monitoring with a novel in-ear sensor system: results of a human hypoxia study

Pulse oximetry is a well-established, noninvasive photoplethysmographic method to monitor vital signs. It allows us to measure cardiovascular parameters, such as heart rate and arterial oxygen saturation, and is considered an essential monitoring tool in clinical routine. However, since many of the conventional systems work in transmission mode, they can only be applied to the thinner or peripheral parts of the body, such as a finger tip. This has the major disadvantage that, in case of shock-induced centralization and a resulting drop in perfusion, such systems cannot ensure valid measurements. Therefore, we developed a reflective in-ear sensor system that can be worn in the ear channel like a headphone. Because the sensor is integrated in an ear mold and positioned very close to the trunk, reliable measurement is expected even in case of centralization. An additional advantage is that the sensor is comfortable to wear and has considerable resistance to motion artifacts. In this paper, we report on hypoxia studies with ten healthy participants which were performed to analyze the system with regard to the detection of heart rate and arterial oxygen saturation. It was shown earlier that, due to the high signal quality, heart rate can easily be detected. Using the conventional calculation principle, based on Beer-Lambert's law combined with a single-point calibration method, we now demonstrate that the detection of arterial oxygen saturation in the human ear canal is possible using reflective saturation sensors.     

Kondensation von Xylose mit Methylammoniumacetat

Zusammenfassung Erhitzt man Xylose mit Methylammoniumacetat in wäßriger Lösung, so entsteht ein komplexes Reaktionsgemisch, das niedermolekulare und höhermolekulare Verbindungen enthalt. Nach Oxydation mit Perjodat sind 1-Methyl-2,3,4- and 1-Methyl-2,3,5-tris-formylpyrrol (4 und 6) isolierbar. Zur Erklärung der Bildung wird angenommen, daß 2 Moleküle des Zuckers mit einem Molekül Methylamin kondensieren.

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Condensation of xylose with methylainmoniumacetate 6. Studies on Maillard reaction

Summary When xylose is heated with methylammoniumacetate in an aqueous solution, a complex mixture containing low molecular and high molecular compounds is formed. After oxidation with periodate, 1-methyl-2,3,4- and 1-methyl-2,3,5-tris-formyl-pyrrol (4 and 6) could be isolated. The formation is probably due to the condensation of two molecules of sugar and one molecule of methylamine.

     

Pseudotransient Continuation-Based Steady State Solver: Extension to Zero Flow Rates

This paper presents and discusses an extension of the pseudotransient continuation-based steady state solver for hydraulic networks proposed previously to the case of zero flow rates. The original solver, which reduces the solution of the governing nonlinear algebraic equations to the numerical integration of an initial-value problem, has problems in situations in which the head derivative of the flow rate tends to infinity, as is the case with zero flow rates. The extension is on the basis of the use of a model headloss-flow relationship that coincides with the true one at zero and has a finite head derivative at that point. This modified steady state solver is free from some convergence problems that occur in Newton-Raphson method-based solvers when analyzing a pipe network with control devices. The paper includes the results of the numerical analysis of test networks, which demonstrate the convergence of the modified steady state solver for cases in which existing steady state solvers have troubles.     

Replication of single macromolecules with graphene

The electronic properties of graphenes depend sensitively on their deformation, and therefore strain engineered graphene electronics is envisioned. In order to deform graphenes locally, we have mechanically exfoliated single and few layer graphenes onto atomically flat mica surfaces covered with isolated double stranded plasmid DNA rings. Using scanning force microscopy in both contact and intermittent contact modes, we find that the graphenes replicate the topography of the underlying DNA with high precision. The availability of macromolecules of different topologies, e.g., programmable DNA patterns, render this approach promising for new graphene based device designs. On the other hand, the encapsulation of single macromolecules offers new prospects for analytical scanning probe microscopy techniques.     

Initial stages of high-temperature CaF2/Si(001) epitaxial growth studied by surface X-ray diffraction

Surface X-ray diffraction was applied to study structure of the fluorite-silicon interface forming upon epitaxial growth of CaF2 on Si(001) surface kept at 750 degrees C. Samples with CaF2 coverage of 1.5-4 (110)-monolayers were grown and in-situ characterized using synchrotron radiation. The 3 x 1-like surface reconstruction was observed in agreement with the previous studies by electron diffraction. Interestingly, a well pronounced splitting of the fractional x 1/3 reflections was revealed. This splitting was ascribed to the effect of antiphase domain boundaries in the row-like structure of the interface layer. The in-plane integrated intensities were used to reconstruct two-dimensional atomic structure of the high-temperature CaF2/Si(001) interface.