Cyclodextrin-based self-assembled nanotubes at the water/air interface

Native alpha-cyclodextrin (alpha-CD) is found to spontaneously form films at aqueous solution/air interfaces. Shape-response measurements to volume perturbations on drops hanging from a capillary indicate that temperature and sodium dodecyl sulfate (SDS) concentration strongly modify the viscoelastic properties of such films. By using isothermal titration calorimetry (ITC), Brewster angle microscopy (BAM), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, it is shown that the films consist of self-assembled nanotubes whose building blocks are cyclodextrin dimers (alpha-CD2) and alpha-CD2-SDS1 complexes.     

In-situ monitoring of optical near-field material processing by electron microscopes

A GaN-to-InGaN interface modification by predeposition of an ultrathin In-rich InGaN incomplete layer followed by a thin triangular InGaN well layer was employed to overcome the negative effects of polarization field on light emission efficiency of InGaN/GaN quantum wells as well as to improve the crystalline quality by avoidance of a significant strain generation and enhanced surfactant effect. Further, the interface modification induced energy band structure engineering reduces the spatial separation of electrons and holes, and thus increases the carrier recombination rate. The improvement in crystalline quality, localized potential fluctuation, and energy band engineering contribute to the significant increase of green emission of the InGaN/GaN quantum wells.     

Chemical control of stem cell fate and developmental potential

Potential applications of stem cells in medicine range from their inclusion in disease modeling and drug discovery to cell transplantation and regenerative therapies. However, before this promise can be realized several obstacles must be overcome, including the control of stem cell differentiation, allogeneic rejection and limited cell availability. This will require an improved understanding of the mechanisms that govern stem cell potential and the development of robust methods to efficiently control their fate. Recently, a number of small molecules have been identified that can be used both in vitro and in vivo as tools to expand stem cells, direct their differentiation, or reprogram somatic cells to a more naive state. These molecules have provided a wealth of insights into the signaling and epigenetic mechanisms that regulate stem cell biology, and are already beginning to contribute to the development of effective treatments for tissue repair and regeneration.     

Synthesis and complete assignment of the 1H and 13C NMR spectra of 6-substituted and 2,6-disubstituted pyridazin-3(2H)-ones

Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed.     

Nanostructured Heteroarm Star Block Terpolymers via an Extension of the “In–Out” Polymerization Route

In this communication an extended “in–out” polymerization method is presented, which leads to the synthesis of novel heteroarm star block terpolymers of the type A_n(B‐b‐C)_n. A four step/one‐pot synthetic procedure is pursued using anionic polymerization under an inert atmosphere. The resulted star‐shaped terpolymer consists of a divinyl benzene nodule bearing pure polystyrene and poly(hexyl methacrylate)‐block‐poly(methyl methacrylate) diblock copolymer arms. It is shown that this kind of star terpolymers can self‐assemble in the bulk forming lamellae mesophase by arm and block segregation. The mechanical properties of the terpolymer have been examined in detail. Finally, the proposed synthetic procedure can be easily employed in other controlled polymerization methods.

     

Ultrasonic Extraction–Ozonation Sequential Sample Treatment for the Determination of Arsenic in Environmental Certified Reference Materials by Hydride Generation–Atomic Fluorescence Spectrometry

Abstract

A sample pretreatment method based on ultrasound‐assisted extraction followed by ozonation is developed for sensitive determination of total As in biological and environmental certified reference materials and an unknown plant sample (Acacia dealbata) by flow injection and continuous‐flow hydride generation–atomic fluorescence spectrometry. The method is meant to minimize the use of corrosive and oxidizing acids for sample decomposition and common errors in trace analysis. Problems derived from introduction of sonicated extracts in continuous flow and flow injection manifolds in combination with an atomic fluorescence detector, such as excessive foaming and flame instability, are addressed. The following certified reference materials (CRMs) were employed for method assessment: BCR CRM 482 lichen; BCR CRM 60 and 61 aquatic plants; BCR CRM 279 sea lettuce; NIST 1633b fly ash; BCR 320 river sediment; RTC CRM 024‐050 soil. Effect of variables such as extraction time, ultrasound amplitude, concentration of extractant acid, sample mass, drying mode, and particle size was investigated. Leaves of Acacia dealbata were also employed for method development. Limits of detection ranged from 0.03 to 0.15 µg/g As depending on the sample. Between‐batch precision values ranged from 2% to 11%. Sample throughput was 40 hr^?1 with flow injection.     

A feasibility study of dynamic stress analysis inside a running internal combustion engine using synchrotron X‐ray beams

The present investigation establishes the feasibility of using synchrotron‐generated X‐ray beams for time‐resolved in situ imaging and diffraction of the interior components of an internal combustion engine during its operation. The demonstration experiment was carried out on beamline I12 (JEEP) at Diamond Light Source, UK. The external hutch of the JEEP instrument is a large‐scale engineering test bed for complex in situ processing and simulation experiments. The hutch incorporates a large capacity translation and rotation table and a selection of detectors for monochromatic and white‐beam diffraction and imaging. These capabilities were used to record X‐ray movies of a motorcycle internal combustion engine running at 1850 r.p.m. and to measure strain inside the connecting rod via stroboscopic X‐ray diffraction measurement. The high penetrating ability and high flux of the X‐ray beam at JEEP allowed the observation of inlet and outlet valve motion, as well as that of the piston, connecting rod and the timing chain within the engine. Finally, the dynamic internal strain within the moving connecting rod was evaluated with an accuracy of ～50 × 10^?6.     

3D microoptical elements formed in a photostructurable germanium silicate by direct laser writing

We present our investigations into the fabrication of three-dimensional microoptical elements by the direct femtosecond laser writing of a germanium–silicon photosensitive hybrid material. Germanium glass composites are very interesting for optical applications as they are photosensitive, and maintain high optical transparency in the visible and near-infrared bands of the spectrum. Here, we have used a germanium containing hybrid material to make nanophotonic structures and microoptical elements such as photonic crystal templates, prisms and spatial polarization plates, both on flat surfaces and fiber tips. Our results show that this germanium silicate composite is an excellent material for microoptics fabrication.