Imaging visible light with Medipix2

A need exists for high-speed single-photon counting optical imaging detectors. Single-photon counting high-speed detection of x rays is possible by using Medipix2 with pixelated silicon photodiodes. In this article, we report on a device that exploits the Medipix2 chip for optical imaging. The fabricated device is capable of imaging at >3000 frames/s over a 256×256 pixel matrix. The imaging performance of the detector device via the modulation transfer function is measured, and the presence of ion feedback and its degradation of the imaging properties are discussed.     

The contribution of β-carotene to vitamin A supply of humans

Populations that administer highly restrictive diets using a strong dietary regime, excluding certain types of food, might be at risk of vitamin A insufficiency, even in developed countries. Thus, provitamin A carotenoids from plants represent an additional major dietary source of vitamin A for most of the world's population. Our aim was to estimate the contribution of β-carotene to vitamin A supply in industrialized countries using available data from the literature. A total of 11 studies from 8 countries were used, representing data of 121,256 participants. Intakes of total vitamin A, provitamin A carotenoids, including β-carotene were retrieved and used to calculate the retinol activity equivalents (RAE) utilizing current conversion factors. Mean total daily dietary intake of RAE was 1083±175. The mean β-carotene intake was 3.9 mg/day. Preformed vitamin A accounts for nearly 65% of total vitamin A intake, carotenoids make up 35%. No statistical differences between men and women in total intake of retinol were observed. We conclude that a safe vitamin A intake in general cannot be reached by consuming only one component (vitamin A or β-carotene) alone, even in Western countries where animal products are commonly available.     

Shape‐Memory Properties of Polyetherurethane Foams Prepared by Thermally Induced Phase Separation

In this study, we report the preparation of two structurally different shape‐memory polymer foams by thermally induced phase separation (TIPS) from amorphous polyetherurethanes. Foams with either a homogeneous, monomodal, or with a hierarchically structured, bimodal, pore size distribution are obtained by adoption of the cooling protocol. The shape‐memory properties have been investigated for both foam structures by cyclic, thermomechanical experiments, while the morphological changes on the micro scale (pore level) have been compared to the macro scale by an in situ micro compression device experiment. The results show that the hierarchically structured foam achieves higher shape‐recovery rates and a higher total recovery as compared to the homogeneous foam, which is due to an increased energy storage capability by micro scale bending of the hierarchically structured foam compared to pure compression of the homogeneous foam.     

Interactions of human endothelial cells with gold nanoparticles of different morphologies

The interactions between noncancerous, primary endothelial cells and gold nanoparticles with different morphologies but the same ligand capping are investigated. The endothelial cells are incubated with gold nanospheres, nanorods, hollow gold spheres, and core/shell silica/gold nanocrystals, which are coated with monocarboxy (1-mercaptoundec-11-yl) hexaethylene glycol (OEG). Cell viability studies show that all types of gold particles are noncytotoxic. The number of particles taken up by the cells is estimated using inductively coupled plasma (ICP), and are found to differ depending on particle morphology. The above results are discussed with respect to heating efficiency. Using experimental data reported earlier and theoretical model calculations which take into account the physical properties and distribution of particles in the cellular microenvironment, it is found that collective heating effects of several cells loaded with nanoparticles must be included to explain the observed viability of the endothelial cells.     

Sparse matrix operations on several multi-core architectures

This paper compares various contemporary multicore-based microprocessor architectures from different vendors with different memory interconnects regarding performance, speedup, and parallel efficiency. Sparse matrix decomposition is used as a benchmark application. The example matrix used in the experiments comes from an electrical engineering application, where numerical simulation of physical processes plays an important role in the design of industrial products.     

Proton beam writing of microstructures in Agar gel for patterned cell growth

A rather useful prerequisite for many biological and biophysical studies, e.g., for cell-cell communication or neuronal networks, is confined cell growth on micro-structured surfaces. Solidified Agar layers have smooth surfaces which are electrically neutral and thus inhibit receptor binding and cell adhesion. For the first time, Agar microstructures have been manufactured using proton beam writing (PBW). In the irradiated Agar material the polysaccharides are split into oligosaccharides which can easily be washed off leaving Agar-free areas for cell adhesion. The beam diameter of 1 μm allows the fabrication of compartments accommodating single cells which are connected by micrometer-sized channels. Using the external beam the production process is very fast. Up to 50 Petri dishes can be produced per day which makes this technique very suitable for biological investigations which require large throughputs.     

Capillary zone electrophoresis for gliadin separation: applications in a spelt breeding program

Gliadins of 27 European spelt [Triticum aestivum ssp. spelta (L.) Thell.] cultivars (cvs) were separated by capillary zone electrophoresis (CZE). A great amount of diversity was found within the CZE gliadin patterns of these cvs; however, only 15 had unique patterns, whereas 2 triples and 3 pairs were identical, i.e., differences were within the uncertainty of the method and environmental effects. Two of these identical pairs were attributed to mislabeling: affected were one of the two Swiss spelt cvs 'Ostar' and 'Sertel', and the German spelt cv 'Steiners Roter Tiroler'. The German cv 'Franckenkorn' showed considerable similarity with the Belgian cv 'Rouquin'. CZE gliadin patterns of 12 modern German bread wheat cvs were distinctly different from those of spelt cvs selected from old land varieties like the Swiss cv 'Oberkulmer Rotkorn'. In the gliadin patterns of 11 spelt cvs, bread wheat elements were found. 7 of the 24 cvs not mislabeled are known to be progeny of wheat/spelt crosses, 4 cvs are described as pure spelt, and the pedigrees of 13 are unknown. Wheat elements were spotted in only 4 of the 7 wheat/spelt crosses and in none of the 4 pure spelt cvs. The results suggest that crossing spelt with modern wheat may be, but is not necessarily, reflected in the gliadin pattern.

Quantitative high-resolution mapping of phenanthrene sorption to black carbon particles

Sorption of hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) to black carbon (BC) particles has been the focus of numerous studies. Conclusions on sorption mechanisms of PAH on BC were mostly derived from studies of sorption isotherms and sorption kinetics, which are based on batch experiments. However, mechanistic modeling approaches consider processes at the subparticle scale, some including transport within the pore-space or different spatial pore-domains. Direct evidence based on analytical techniques operating at the submicrometer scale for the location of sorption sites and the adsorbed species is lacking. In this work, we identified, quantified, and mapped the sorption of PAHs on different BC particles (activated carbon, charcoal and diesel soot) on a 25-100 nm scale using scanning transmission X-ray microscopy (STXM). In addition, we visualized the pore structure of the particles by transmission electron microscopy (TEM) on the 1-10 nm-scale. The combination of the chemical information from STXM with the physical information from TEM revealed that phenanthrene accumulates in the interconnected pore-system along primary "cracks" in the particles, confirming an adsorption mechanism.