Large-Area Single-Crystal Graphene via Self-Organization at the Macroscale

In 1665 Christiaan Huygens first noticed how two pendulums, regardless of their initial state, would synchronize.  It is now known that the universe is full of complex self-organizing systems, from neural networks to correlated materials. Here, graphene flakes, nucleated over a polycrystalline graphene film, synchronize during growth so as to ultimately yield a common crystal orientation at the macroscale. Strain and diffusion gradients are argued as the probable causes for the long-range cross-talk between flakes and the formation of a single-grain graphene layer. The work demonstrates that graphene synthesis can be advanced to control the nucleated crystal shape, registry, and relative alignment between graphene crystals for large area, that is, a single-crystal bilayer, and (AB-stacked) few-layer graphene can been grown at the wafer scale.     

The influence of structural properties on the dye diffusion and dyeabilty of PA 6 fibres

The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*, b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the material's history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase of dyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.     

Influence of bifunctionality of reactive dyes on the bending rigidity of viscose printed with polysaccharide thickeners

The bending rigidity and colour depth of viscose printed with a number of reactive dyes in the presence of alginate and guar gum thickeners has been investigated. Interactions between the fabric, the dyes and the thickener were evaluated to determine the bending rigidity of the printed substrate. The results show that mono- or bi-functional reactive dyes cause undesired stiff fabric handle depending on the structure (the type of the reactive system and the reactive group), the reactivity and the concentration of the reactive dye used. These interactions differ to a greater degree when guar gum thickeners are used.     

Positional Scanning Synthesis of a Peptoid Library Yields New Inducers of Apoptosis that Target Karyopherins and Tubulin

We describe the synthesis of a library of 11 638 N‐alkylglycine peptoid trimers in a positional scanning format with adjustment of reaction conditions to account for different reactivities of the monomer building blocks. Evaluation of the library by high‐content phenotypic screening for modulators of the cytoskeleton and mitosis resulted in the identification of two apoptosis‐inducing peptoids, which, despite their structural similarity, target different proteins and cellular mechanisms. Whereas one peptoid binds to karyopherins, which mediate nuclear transport, the other N‐alkylglycine trimer binds tubulin at the vinca alkaloid binding site.     

A comparative study on the effect of some antioxidants on the lipid and pigment oxidation in dry-fermented sausages

A comparative study on the effect of antioxidants on the lipid and pigment oxidation in Bulgarian dry‐fermented sausage type lukanka is described. A commercial mix of antioxidants, called ‘grindox 1021’ (GR), restricted the development of the peroxidation processes in dry‐fermented sausages (type lukanka) to a greater extent than either rosemary (RS), rutine (RT), sodium erythrobate (SE) or l ‐ascorbic acid, when applied at the same concentration. The latter compounds did not effectively stabilize lipids in sausages against oxidation; they only slowed down the lypolysis and did not greatly change the colour of the cross‐sectional surface. However, the sausage lipids were best stabilized when 1 g kg^?1 GR, RS or RT was added. The addition of 1 g kg^?1 RS and GR most efficiently suppressed the hydroperoxides – primary derivatives of lipid peroxidation, while the secondary derivatives in the final product were most reduced when 1 g kg^?1 GR and SE were added.     

Theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes

We present theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes. A simple physical model, taking into account the basic physics of current rectification, can adequately describe the single-tube and array devices. We show that for as-grown array diodes, the rectification ratio, defined by the maximum-to-minimum-current-ratio, is low due to the presence of metallic-single-walled nanotube (SWNT) shunts. These tubes can be eliminated in a single voltage sweep resulting in a high rectification array device. Further analysis also shows that the channel resistance, and not the intrinsic nanotube diode properties, limits the rectification in devices with channel length up to 10 μm.     

Multiple aspect-ratio structural integration in single crystal silicon (MASIS) for fabrication of transmissive MOEMS modulators

A novel fabrication process, named MASIS (multiple aspect ratio structural integration in single-crystal-silicon), is introduced for the implementation of single-crystal-silicon microstructures characterized by distinct aspect ratios to be fabricated in the same device layer. The MASIS process was especially designed for fabrication of transmissive MOEMS (Micro-Opto-Electro-Mechanical-Systems) modulators incorporating large field areas, and driven by long-stroke comb-drive actuators combined with folded suspensions. The comb-drive actuators were designed to achieve large amplitude of vibration and high natural frequencies, which allow large aperture areas at high operational frequency. The MASIS process consists of selective thinning of the device thickness in the shutter area, reducing payload mass, while preserving higher thickness of the suspension springs and comb-drive transducer fingers, thereby increasing the natural frequency of the device and reducing actuation voltages. A modulator was successfully fabricated, demonstrating maximum displacement of 50 μm at 1 kHz in resonance using an actuation voltage of 15 Vpp in air. The MOEMS modulator was adapted as integral part of a solid-state photodetection system to overcome the low-frequency noise.     

Instructing in generalized knowledge structures to develop flexible problem solving skills

In contrast to routine knowledge and skills, flexible problem solving is associated with the ability to apply one’s knowledge structures in relatively new situations. In the absence of specific knowledge-based guidance, such processes could be very cognitively demanding. This paper suggests that learning flexible problem solving skills could be enhanced by explicitly instructing learners in generalized forms of schematic knowledge structures that are applicable to a greater variety of problems. The paper presents results of an experimental study that has investigated this approach in learning the operation of a technical device, and discusses implications of these results for the design of computer-based instruction.