Synthesis of Highly Stable 1,3-Diaryl-1H-1,2,3-triazol-5-ylidenes and their Applications in Ruthenium-Catalyzed Olefin Metathesis

The formal cycloaddition between 1,3-diaza-2-azoniaallene salts and alkynes or alkyne equivalents provides an efficient synthesis of 1,3-diaryl-1H-1,2,3-triazolium salts, the direct precursors of 1,2,3-triazol-5-ylidenes. These N,N-diarylated mesoionic carbenes (MICs) exhibit enhanced stability in comparison to their alkylated counterparts. Experimental and computational results confirm that these MICs act as strongly electron-donating ligands. Their increased stability allows for the preparation of ruthenium olefin metathesis catalysts that are efficient in both ring-opening and ring-closing reactions.     

Solution and quasi‐bulk copolymerizations of styrene and methyl methacrylate in the presence of polybutadiene: Mathematical model

A mathematical model was developed for simulating the batch copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of polybutadiene (PB). It was adjusted to the measurements of three reactions carried out at 65°C, with initial comonomers ratio at the azeotropic condition, THF as solvent, and benzoyl peroxide as initiator. The measurements included: (a) conversions and grafting efficiencies by gravimetry; (b) molecular weight distributions (MWDs) by size exclusion chromatography; and (c) global mass fractions of St in the co‐ and terpolymer, by UV‐Vis spectroscopy. The model predicts the MWDs of the three polymeric components of MBS: free St‐MMA copolymer, St‐MMA‐g‐PB graft terpolymer (GT), and residual PB. In addition, it predicts the bivariate chain length distributions of the different GT topologies, with each topology characterized by the number of branches per molecule. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A lightweight framework for dynamic GUI data verification based on scripts

Runtime verification (RV) provides essential mechanisms to enhance software robustness and prevent malfunction. However, RV often entails complex and formal processes that could be avoided in scenarios in which only invariants or simple safety properties are verified, for example, when verifying input data in Graphical User Interfaces (GUIs). This paper describes S‐DAVER, a lightweight framework aimed at supporting separate data verification in GUIs. All the verification processes are encapsulated in an independent layer and then transparently integrated into an application. The verification rules are specified in separate files and written in interpreted languages to be changed/reloaded at runtime without recompilation. Superimposed visual feedback is used to assist developers during the testing stage and to improve the experience of users during execution. S‐DAVER provides a lightweight, easy‐to‐integrate and dynamic verification framework for GUI data. It is an integral part of the development, testing and execution stages. An implementation of S‐DAVER was successfully integrated into existing open‐source applications, with promising results. Copyright © 2015 John Wiley & Sons, Ltd.     

Beam steering with segmented annular arrays

Two-dimensional (2-D) arrays of squared matrix have maximum periodicity in their main directions; consequently, they require half wavelength (lambda/2), interelement spacing to avoid grating lobes. This condition gives rise to well-known problems derived from the huge number of array elements and from their small size. In contrast, 2-D arrays with curvilinear configuration produce lower grating lobes and, therefore, allow the element size to be increased beyond lambda/2. Using larger elements, these arrays have the advantage of reducing the number of elements and of increasing the signal-to-noise ratio (SNR). In this paper, the beamforming properties of segmented annular phased arrays are theoretically analyzed and compared with the equivalent squared matrix array. In the first part, point-like elements are considered in order to facilitate the field analysis with respect to the array structure. Afterward, the effect of the element size on the steered beam properties also is presented. In the examples, it is shown that the segmented annular array has notably lower grating lobes than the equivalent squared matrix array and that it is possible to design segmented annular arrays with interelement distance higher than lambda whose beam characteristics are perfectly valid for volumetric imaging applications.     

Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route

Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxidic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size <30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.     

TiO2 nanotubes manufactured by anodization of Ti thin films for on-chip Li-ion 2D microbatteries

The use of self-organized TiO₂ nanotube arrays electrochemically grown onto Si is investigated for the fabrication of an alternative electrode dedicated to on-chip Li-ion 2D microbatteries. Discharge/charge curves and cycling performance are studied in lithium-anode electrochemical test cells for both amorphous and crystalline titania nanotubes. At 5 μA cm⁻² amorphous TiO₂ nanotube layers onto Si deliver a maximum areal capacity of 89 μAh cm⁻² in the first reversible discharge and 56 μAh cm⁻² over 50 cycles. We demonstrate that these nanostructured thin film electrodes showing such electrochemical performances are compatible with IC technology.