Synthesis and properties of YBa2Cu3O7-δ – Y2Ba4CuWO10.8 superconducting composites

YBa₂Cu₃O_7-δ (YBCO) is a well-known high-temperature superconductor. However, its critical current density and thus maximum trapped magnetic field can be improved significantly by introducing the secondary phases (artificial pinning centers). In this contribution, we successfully prepared YBCO single-grain bulks with Y₂Ba₄CuWO_10.8 phase serving as a source of pinning centers. This phase was prepared by solid-state reaction and further refined by milling. In the next step single-grain YBCO bulks with homogeneously distributed Y₂Ba₄CuWO_10.8 were prepared by top-seeded melt growth. Precursors as well as the final product were characterized by XRD, SEM and EDS. The phase composition of YBCO bulks containing Y₂Ba₄CuWO_10.8 was analyzed using Rietveld analysis. Thermal stability of YBCO bulk was studied by STA. Furthermore, PPMS was used to study electrical resistivity and critical current density. Bulk superconducting properties such as levitation force and trapped field ability were also measured.     

Periodic steady state analysis using shooting and wave-form-newton

This paper describes a method of determining the forced periodic steady state response of non-linear circuits. the method is closely related to the work of Aprille and Trick Proc. IEEE, 60 , 108-114 (1972) and also to the finite difference method for solving a boundary value problem. The new approach is a shooting method in the sense that in every iteration an initial value problem is solved. It is, however, also a relaxation method, because in every iteration a periodic wave-form is obtained. This is achieved by solving in each step a linear time-dependent differential equation whose solution can be easily transformed into a periodic solution satisfying this linear equation. Because the iteration takes place on wave-forms rather than initial values and every solution satisfies the boundary conditions, the method is robust. It will be shown that for a causal approximation of the time derivatives the iterated wave-forms are equal to those found using the finite difference methods.     

Development of a gel spinning process for high‐strength poly(ethylene oxide) fibers

This article describes a new gel‐spinning process for making high‐strength poly(ethylene oxide) (PEO) fibers. The PEO gel‐spinning process was enabled through an oligomer/polymer blend in place of conventional organic solvents, and the gelation and solvent‐like properties were investigated. A 92/8 wt% poly(ethylene glycol)/PEO gel exhibited a melting temperature around 45°C and was highly stretchable at room temperature. Some salient features of a gel‐spun PEO fiber with a draw ratio of 60 are tensile strength at break = 0.66 ± 0.04 GPa, Young's modulus = 4.3 ± 0.1 GPa, and a toughness corresponding to 117 MJ/m³. These numbers are significantly higher than those previously reported. Wide‐angle x‐ray diffraction of the high‐strength fibers showed good molecular orientation along the fiber direction. The results also demonstrate the potential of further improvement of mechanical properties. POLYM. ENG. SCI., 54:2839–2847, 2014. © 2014 Society of Plastics Engineers     

Evaluation of the Interaction between Phosphohistidine Analogues and Phosphotyrosine Binding Domains

We have investigated the interaction of peptides containing phosphohistidine analogues and their homologues with the prototypical phosphotyrosine binding SH2 domain from the eukaryotic cell signalling protein Grb2 by using a combination of isothermal titration calorimetry and a fluorescence anisotropy competition assay. These investigations demonstrated that the triazole class of phosphohistidine analogues are capable of binding too, suggesting that phosphohistidine could potentially be detected by this class of proteins in vivo.     

Separation of Xenon and Krypton in the Metal–Organic Frameworks M2(m-dobdc) (M=Co,Ni)

The separation of Xe and Kr from air is challenging owing both to the very low atmospheric concentrations of these gases and the need for their distillation at cryogenic temperatures. Alternatively, separation processes based on adsorption could provide a less energy-intensive route to the isolation of these gases. Here, we demonstrate that the metal–organic frameworks M₂(m-dobdc) (M=Co, Ni; m-dobdc⁴⁻=4,6-dioxido-1,3-benzenedicarboxylate) effectively separate Xe and Kr at ambient temperatures based on the different adsorption enthalpies of each gas at the coordinatively-unsaturated M²⁺ sites in each material. In situ Xe- and Kr-dosed powder X-ray diffraction studies further reveal key differences in the binding of Xe and Kr within the materials. In particular, while both gases adsorb near the framework open metal sites at 200 K, much higher Xe occupancies are observed at these sites relative to Kr, corroborating a stronger interaction of the polarizing M²⁺ cations with Xe. Further, while krypton is only found located above the open metal sites, two additional adsorption sites are observed for xenon, correlating with the stronger adsorption of Xe over Kr in these materials. These results suggest the possible utility of employing M₂(m-dobdc) materials in the adsorptive separation of Xe and Kr.     

Effect of combining ethylene/methyl acrylate/glycidyl methacrylate terpolymer and an organoclay on the toughening of poly(lactic acid)

Blends of poly(lactic acid) (PLA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (EMA‐GMA) with and without the addition of an organoclay were prepared by melt mixing in a twin screw extruder. Mechanical, morphological, structural, and rheological properties of the systems have been investigated as function of its compositions. The impact strength (IS) of PLA increased with the addition of EMA‐GMA. Furthermore, the addition of 2.5 wt% of organoclay to the PLA/EMA‐GMA blend promoted improvements in the mechanical properties, such as IS, tensile strength, and strain‐at‐break. Further addition of organoclay, 5 wt%, led to a formation of a double percolated network, where the clay particles form bridges across EMA‐GMA droplets and glue them together, however, without coalescence. In addition, morphological and wide‐angle X‐ray scattering analyses evidenced that the clay presents a partially exfoliated structure and that remains inside the EMA‐GMA droplets, probably as a consequence of the approach used to produce the systems. POLYM. ENG. SCI., 54:1922–1930, 2014. © 2013 Society of Plastics Engineers     

Gram-Negative Flagella Glycosylation

Protein glycosylation had been considered as an eccentricity of a few bacteria. However, through advances in analytical methods and genome sequencing, it is now established that bacteria possess both N-linked and O-linked glycosylation pathways. Both glycosylation pathways can modify multiple proteins, flagellins from Archaea and Eubacteria being one of these. Flagella O-glycosylation has been demonstrated in many polar flagellins from Gram-negative bacteria and in only the Gram-positive genera Clostridium and Listeria. Furthermore, O-glycosylation has also been demonstrated in a limited number of lateral flagellins. In this work, we revised the current advances in flagellar glycosylation from Gram-negative bacteria, focusing on the structural diversity of glycans, the O-linked pathway and the biological function of flagella glycosylation.     

CFD Process Modeling of the Industrial Calcination of Diatomite

Calcination of diatomite is an expensive process frequently resulting in products with unpredictable structure. Alternatively, calcination in swirling flow is an energy‐saving option. Computational fluid dynamics modeling of an experimental calcination process unit is presented. Experimental results and systematic collection of process data were used to define boundary condition for steady‐state and transient simulation runs. The comparison of experimental and simulation results shows the complexity of the calcination process. The results can be used for further process optimization.