High-resolution direct patterning of gold nanoparticles by the microfluidic molding process

A novel microfluidic molding process was used to form microscale features of gold nanoparticles on polyimide, glass, and silicon substrates. This technique uses permeation pumping to pattern and concentrate a nanoparticle ink inside microfluidic channels created in a porous polymer template in contact with a substrate. The nanoparticle ink is self-concentrated in the microchannels, resulting in dense, close-packed nanoparticle features. The method allows for better control over the structure of printed features at a resolution that is comparable to inkjet printing, and is purely additive with no residual layers or etching required. The process uses low temperatures and pressures and takes place in an ambient environment. After patterning, the gold nanoparticles were sintered into continuous and conductive gold traces.     

Insights into the Dynamics and Molecular Recognition Features of Glycopeptides by Protein Receptors: The 3D Solution Structure of Hevein Bound to the Trisaccharide Core of N‐Glycoproteins

Protein‐carbohydrate interactions are at the heart of a variety of essential molecular recognition events. Hevein, a model lectin related to the superantigen family, recognizes the trisaccharide core of N‐glycoproteins ( 1 ). A combined approach of NMR spectroscopy and molecular modeling has permitted us to demonstrate that an Asn‐linked Man(GlcNAc)₂ ( 2 ) is bound with even higher affinity than (GlcNAc)₃. The molecular recognition process entails conformational selection of only one of the possibilities existing for chitooligosaccharides. The deduced 3D structure of the hevein/ 2 complex permits the extension of polypeptide chains from the Asn moiety of 2 , as well as glycosylation at Man O‐3 and Man O‐6 of the terminal sugar. Given the ubiquity of the Man(GlcNAc)₂ core in all mammalian N‐glycoproteins, the basic recognition mode presented herein might be extended to a variety of systems with biomedical importance.     

Evaluation of the performance of single‐walled carbon nanohorns in capillary electrophoresis

This paper describes for the first time the use of single‐walled carbon nanohorns (SWNHs) as pseudostationary and stationary phases for EKC and CEC, respectively, taking advantage of their characteristic features, such as conical‐end termination, formation of spherical assemblies dahlia‐flower like superstructure and easy functionalization. The use of SWNHs as pseudostationary phase for EKC required the study of their dispersion in different surfactants as well as their compatibility with the electrophoretic system. The carboxylation and subsequent immobilization of carboxylated SWNHs in fused‐silica capillary to obtain useful, reproducible and stable stationary phases for CEC has also been investigated, with promising results. The electrophoretic separations obtained for water‐soluble vitamins in both modalities (EKC and CEC) have been systematically compared with those obtained with single‐walled carbon nanotubes.     

Controlled accessibility Lewis acid catalysed thermal reactions of regenerated cellulosic fibres

A combination of techniques have been used to characterise lyocell regenerated cellulose fibre subjected to low-moisture thermal-catalytic reactions with zinc chloride Lewis acid. Application from non-swelling ethanol reduces catalyst accessibility, but at high temperatures migration takes place through the internal fibre morphology. The extent of chain scission is reduced at lower temperatures, leading to a higher leveling-off degree of polymerisation (LODP). In contrast, application of zinc chloride from water results in a lower LODP, due to the more even distribution of catalyst. The weights of extractable polymer material increase according to two separate rate constants, following established semicrystalline models. A higher Arrhenius activation energy for chain scission is seen for zinc chloride application from ethanol, which may be due to the physical mobilisation of the cellulose polymer at high temperature, associated with a cellulose T_g. This may also aid recrystallisation. Cellulose dehydration endotherms and pyrolysis exotherms are shifted to lower temperature for application of zinc chloride from ethanol compared to water, which may be the result of a higher local concentration of catalyst and a faster reaction onset.     

Transport properties of Pr0.7Ca0.3MnO3/Nb:SrTiO3 heterojunctions

Current–voltage (J–V) characteristics of epitaxial hetero-junctions composed of Pr_0.7Ca_0.3MnO₃ and Nb:SrTiO₃ were studied under forward and reversed bias conditions. Detailed analysis showed that the J–V characteristics of these heterojunctions can be well-fitted by the thermally-assisted tunnelling model. While the dielectric constant of Nb:SrTiO₃ extracted under the forward bias was about one order of magnitude smaller than that of bulk SrTiO₃, the value obtained under reverse bias was very close to that of the bulk SrTiO₃. The result can be explained by the existence of an interface layer on the Nb:SrTiO₃ substrate with a smaller effective dielectric constant. The current finding suggested that the properties of interface layer should be taken into account in order to accurately simulate the J–V characteristics of such heterojunctions.     

Picosecond pulses from a cryogenically cooled, composite amplifier using Yb:YAG and Yb:GSAG

A cryogenic Yb amplifier using two laser materials, Gd3Sc2Al3O12 and Y3Al5O12 (YAG), has been used to obtain 70 W average power at 5 kHz pulse repetition frequency; the output was compressed to 1.6 ps, compared with an input compressible to 1.4 ps. The gain broadening obtained by combining two media enables shorter pulses than using Yb:YAG alone but retains the power-scaling advantages of cryogenic Yb:YAG.     

Diameter graphs of polygons and the proof of a conjecture of Graham

We show that for an n-gon with unit diameter to have maximum area, its diameter graph must contain a cycle, and we derive an isodiametric theorem for such n-gons in terms of the length of the cycle. We then apply this theorem to prove Graham's 1975 conjecture that the diameter graph of a maximal 2m-gon (m?3) must be a cycle of length 2m−1 with one additional edge attached to it.     

Determination of penicillins in milk using LC‐UV,LC‐MS and LC‐MS/MS

The aim of this work is to establish a method for the simultaneous determination of eight penicillins in milk samples by LC‐UV, LC‐MS and LC‐MS/MS. The procedure involves a step for clean‐up and to preconcentrate the analytes by SPE and a subsequent chromatographic analysis. LC‐UV, LC‐MS and LC‐MS/MS have been used for the simultaneous quantification of penicillins in milk. The proposed methods have been validated according to the EU guideline and present LOQ below the maximum limits of residues (MRLs) established by the European Union for penicillins in milk. The developed methods were applied to different milk samples obtained from cows medicated with penicillins.     

The Effect of Preparation Method and Calcination Temperature on the Crystallite Size and Surface Area of Perovskite-Type SrFeO x

We have investigated the synthesis of perovskite-type SrFeO_x (2.5 x 3.0) using three preparative methods: sol-gel, mechanochemical processing and solid state reactions at high temperature of the corresponding oxides. The sample obtained after calcination of the gel from sol-gel method, contained the least amount of strontium carbonate impurity. The amount of strontium carbonate impurity decreased with the increase in calcination temperature. Perovskites obtained have been characterized by X-ray diffraction (XRD) and nitrogen adsorption isotherms. Samples obtained from three methods have been compared with respect to calcination temperature, crystallite size and specific surface area.Issued as NRCC No. 46479.