Shrinkage control in a photopolymerizable hybrid solgel material for holographic recording

We report the correction of the shrinkage observed during UV postrecording curing in a holographic solgel material that was recently achieved by the use of various chemical formulations for the composition of the hybrid supporting matrix. We found that a chemical modification of the matrix noticeably attenuates the shrinkage (from 1.3% to 0.4% of the material's initial thickness with the inclusion of just 20% tetramethylorthosilicate), providing a material with improved stability for permanent data storage applications. The holographic properties of samples with different binders are also reported. In addition, a theoretical study has revealed the way by which to compensate for angular deviation in the Bragg condition during UV postrecording by tailoring the binder shrinkage (s), the maximum refractive-index modulation capability of the photosensitive mixture (deltan), or both.     

Assessment of Mechanical Properties of Cohesive Particulate Solids. Part 2: Powder Flow Criteria

The fundamentals of cohesive particulate solids' consolidation and flow properties using a reasonable combination of particle and continuum mechanics by means of micro/macrotransition of the "characteristic particle contact" are explained. The adhesion force models of Tomas (2001a) are used to derive the stationary, instantaneous T S1 time yield loci and consolidation loci. Next, the uniaxial compressive strength σ c ( σ 1 ), effective angle of internal friction } e ( σ 1 ), and bulk density 𝜌 b ( σ 1 ) are obtained as powder constitutive functions. The approach has been shown to be effective for the data evaluation of cohesive powder flow properties, like a very cohesive titania nanopowder (surface diameter d s = 200 nm, solid density 𝜌 s = 3870kg/m 3 ) with the fit r 2 xy > 0.95. Finally, these models in combination with accurate shear cell test results are used as constitutive functions for computer-aided silo design for reliable flow.     

Interparticle Collision of Particle Composites—Finite and Discrete Element Simulations

Three different cases of interparticle collisions were simulated to observe the fragmentation mechanisms of composite particles. It was found that the cracking mechanism in interparticle collisions is different from that observed in particle-wall collisions. By means of DEM simulations, it was observed that the primary interparticle bonds break in both tension and shear. Depending on the type of interparticle collisions, cracks and fragments are generated. In general, finer fragments are generated around the impact site of the particles and are surrounded by larger fragments. From DEM simulations, it was found for the most part that the impacting particles exhibit more damage than the stationary particles. The symmetrical loading showed almost the same amount of damage to both types of particles. The discontinuous nature of the material and the unsymmetrical loading caused unsymmetrical damages (crack patterns). In unsymmetrical loadings, the impacting particle was more damaged and had more cracks than the stationary particle.     

THE INCOMPATIBLE MYTHOLOGIES OF NATIONHOOD

The article analyses the series Disko by Lithuanian-American photographer Andrew Miksys. After moving to Lithuania, Miksys photographed discotheques in villages and small towns between the years 2000 and 2010. The series Disko sparked controversy beyond its artistic context when it was appropriated by foreign and Lithuanian mass media and was said to represent Lithuanian nationhood. The contradiction between the denotative and the connotative aspects of Disko and between the different actual and possible functions of the series in particular social, political and cultural contexts are the main issues analysed in this article. It concludes with an assertion that this contradiction can be resolved by understanding the photographs as an opportunity to prevent the common and idealized myth of nationhood from becoming established ideology in art and politics.     

Application of Bayesian Methods for Age‐Dependent Reliability Analysis

In this article, the authors present a general methodology for age‐dependent reliability analysis of degrading or ageing components, structures and systems. The methodology is based on Bayesian methods and inference—its ability to incorporate prior information and on ideas that ageing can be thought of as age‐dependent change of beliefs about reliability parameters (mainly failure rate), when change of belief occurs not only because new failure data or other information becomes available with time but also because it continuously changes due to the flow of time and the evolution of beliefs. The main objective of this article is to present a clear way of how practitioners can apply Bayesian methods to deal with risk and reliability analysis considering ageing phenomena. The methodology describes step‐by‐step failure rate analysis of ageing components: from the Bayesian model building to its verification and generalization with Bayesian model averaging, which as the authors suggest in this article, could serve as an alternative for various goodness‐of‐fit assessment tools and as a universal tool to cope with various sources of uncertainty. The proposed methodology is able to deal with sparse and rare failure events, as is the case in electrical components, piping systems and various other systems with high reliability. In a case study of electrical instrumentation and control components, the proposed methodology was applied to analyse age‐dependent failure rates together with the treatment of uncertainty due to age‐dependent model selection. Copyright © 2013 John Wiley & Sons, Ltd.     

Time-evolution of poly(3-hexylthiophene) as an energy relay dye in dye-sensitized solar cells

Energy relay dyes (ERD) and F?rster resonant energy transfer (FRET) are useful techniques for increasing absorption in dye-sensitized solar cells. We use femtosecond transient absorption spectroscopy to monitor charge generation processes in a solid-state DSC containing poly(3-hexylthiophene) (P3HT) as both the hole-transporter and the ERD with a zinc phthalocyanine dye (TT1) as the sensitizer. We observe efficient FRET occurring on picosecond time scales and subsequent hole transfer from TT1 to P3HT occurring onward from 100 ps.     

The method of fundamental solutions for a time-dependent two-dimensional Cauchy heat conduction problem

We investigate an application of the method of fundamental solutions (MFS) to the time-dependent two-dimensional Cauchy heat conduction problem, which is an inverse ill-posed problem. Data in the form of the solution and its normal derivative is given on a part of the boundary and no data is prescribed on the remaining part of the boundary of the solution domain. To generate a numerical approximation we generalize the work for the stationary case in Marin (2011) [23] to the time-dependent setting building on the MFS proposed in Johansson and Lesnic (2008) [15], for the one-dimensional heat conduction problem. We incorporate Tikhonov regularization to obtain stable results. The proposed approach is flexible and can be adjusted rather easily to various solution domains and data. An additional advantage is that the initial data does not need to be known a priori, but can be reconstructed as well.     

Adsorption of streptavidin onto single-walled carbon nanotubes: application in fluorescent supramolecular nanoassemblies

We report the solubilization of full-length single-walled carbon nanotubes into a physiological buffer by sonication in presence of streptavidin. Transmission electron microscopy showed that the resultant dispersion was enriched of individual/small ropes of nanotubes. By the analysis of the crystal structure of tetrameric streptavidin and of the tryptophan emission of adsorbed proteins we hypothesized that proteins adsorbed onto SWNT sidewalls through their amine functionalities. Our results suggested using streptavidin as an interlinker between carbon nanotubes and semiconducting nanocrystals. We fabricated a supramolecular luminescent nanoassembly composed of individual or small ropes of full-length single-walled carbon nanotubes decorated with streptavidin-conjugated quantum dots. The luminescent nanoassembly was stably dispersed under physiological conditions and was readily visible by optical fluorescent microscopies.     

Ball Impact and Crack Propagation – Simulations of Particle Compound Material

Particle compounds are the combination of various sized particles with non-uniform properties and can be considered as one of the most complicated engineering materials. The properties of the particle compounds vary in large range depending upon applications, methods of manufacturing and ratios of its compositions. Even if the method of manufacturing is same, the properties may be different because of the arrangements of ingredients. The different types of engineering agglomerates and building materials, like concretes, are some examples of the particle compounds. Similarly, the proper recycling of particle compound is very important in order to utilize the valuable aggregates from the cheaper fine matrixes. The aim of this research is to study the crack initiation and propagation in the building materials of spherically shaped concrete structures under impact loadings. A 2 Dimensional Finite Element Analysis is carried out with central impact loading condition to understand the stress pattern distributions before cracking. The Discrete Element Method (DEM) is adopted for further analysis to study the crack propagation in particle compound. Concrete spheres of diameter 150 mm with properties of B35 (35 N/mm² compressive strength) are chosen for the representation. A sphere is geometrically easier for the analysis. The assumption can be made that after some stages of loading the cube shaped concrete will be similar to sphere after losing its edges. This paper discusses the continuum and discrete approach for the analysis of crack propagation in particle compound with reference to the concrete ball. The analysis is done with central impact loading conditions in different velocities ranges between 7.7 m/s to 39 m/s. The correlations between theoretical simulations and practical experiments are also discussed.KeywordsFracture pattern, Crack propagation, Crack simulation, Air cannon, Numerical simulationThe authors would like to acknowledge German Research Foundation for the financial support.     

Customized baseline correction

Baseline correction is an important pre-processing technique used to separate true spectroscopic signals from interference effects or remove background effects, stains or traces of compounds, e.g. in 2D gel electrophoresis. In some cases parts of the spectra or images need correction using rigid baselines (limited curvature) while other parts need more flexible baselines (more curvature). Often one has to make a compromise that is not optimal over the whole spectral range, or focus on one part and let the rest be treated sub-optimally. A customizing wrapper is proposed that rescales the spectrum abscissa and therefore makes the baseline correction algorithm behave right in all parts of the spectra. Improvements are demonstrated both visually and through regression using recently reported Raman spectra on melted fat from pork adipose tissue.