Bis‐Calix[4]arenes: From Ligand Design to the Directed Assembly of a Metal–Organic Trigonal Antiprism

Calix[4]arenes (C[4]s) are versatile platforms for the construction of polymetallic clusters containing paramagnetic metal ions. Synthetic modification at the C[4] methylene bridge allows for the design of bis‐C[4]s that, depending on the linker employed, can be used to either dictate which clusters can be formed or direct the assembly of a new metal–organic polyhedron (MOP). The assembly resulting from the latter approach displays thermal stability and uptake of N₂ or H₂ gas, confirming that this is a viable route to the synthesis of new, functional supramolecular architectures.     

Dislocation density reduction limited by inclusions in kerfless high‐performance multicrystalline silicon

Kerfless high‐performance multicrystalline silicon is an emerging material for photovoltaic applications that is characterized by having a smaller grains, and general lower average dislocation density than conventional ribbon multicrystalline silicon. Although a significant improvement over state‐of‐the‐art, dislocation reduction at the crystal growth stage is not complete. Here we employ an annealing process previously tested in conventional ingot mc‐Si to reduce dislo‐ cation clusters that remain after crystal growth. A sample is subjected to a 1390 °C annealing process for 24 h and its dislocation density reduction is evaluated. We employ infrared birefringence imaging to observe that despite achieving significant average dislocation density reduction, if inclusions are present in the sample, these may serve to nucleate new dislocations due to thermal strain. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Modeling hydration properties and temperature developments of early-age concrete pavement using calorimetry tests

This research aims to evaluate the calorimetry tests for characterizing cement hydration properties and predicting temperature developments of the early-age Portland cement concrete pavement (PCCP). Analytical models are studied to simulate hydration properties, using the measured heat evolution data from both the isothermal and semi-adiabatic tests. HIPERPAV III^® engineering software with these analytical models embedded is used to predict temperature developments of the early-age PCCP. Results show that the maximum hydration time parameter τ corresponds to the maximum activation energy E_a. Semi-adiabatic tests result in a lower hydration shape parameter β yet a higher hydration time parameter τ than isothermal tests. As results, the simulated degree of hydration based on semi-adiabatic tests is higher at the early hours, but lower at later hours compared to that based on isothermal tests. This effect is also reflected from the simulated temperature developments of the early-age PCCP. Three engineering projects in this research show that predicted temperatures of the PCCP using hydration parameters determined from semi-adiabatic tests better match actual measurements than that from isothermal tests.     

A General Fluctuation–Response Relation for Noise Variations and its Application to Driven Hydrodynamic Experiments

The effect of a change of noise amplitudes in overdamped diffusive systems is linked to their unperturbed behavior by means of a nonequilibrium fluctuation–response relation. This formula holds also for systems with state-independent nontrivial diffusivity matrices, as we show with an application to an experiment of two trapped and hydrodynamically coupled colloids, one of which is subject to an external random forcing that mimics an effective temperature. The nonequilibrium susceptibility of the energy to a variation of this driving is an example of our formulation, which improves an earlier version, as it does not depend on the time-discretization of the stochastic dynamics. This scheme holds for generic systems with additive noise and can be easily implemented numerically, thanks to matrix operations.     

Optical and structural properties of CdS thin films grown by chemical bath deposition doped with Ag by ion exchange

In this work thin CdS films using glycine as a complexing agent were fabricated by chemical bath deposition and then doped with silver (Ag), by an ion exchange process with different concentrations of AgNO₃ solutions. The CdS films were immersed in silver solutions using different concentrations during 1 min for doping and after that the films were annealed at 200 °C during 20 min for dopant diffusion after the immersion on the AgNO₃ solutions. The aim of this research was to know the effects of different concentrations of Ag on the optical and structural properties of CdS thin films. The optical band gap of the doped films was determined by transmittance measurements, with the results of transmittance varying between 35% and 70% up to 450 nm in the electromagnetic spectra and the band gap varying between 2.31 and 2.51 eV depending of the silver content. X-ray photoelectron spectroscopy was used to study the influence of silver on the CdS:Ag films, as a function of the AgNO₃ solution concentration. The crystal structure of the thin CdS:Ag films was studied by the X-ray diffraction method and the film surface morphology was studied by atomic force microscopy. Using the ion exchange process, the CdS films’ structural, optical and electric characteristics were modified according to silver nitrate concentration used.     

A serendipitous one-step conversion of 3H-1,2-dithiole-3-thione to (E)-3-[1-(alkylthio)alkylidene]-3H-1,2-dithiole: an experimental and theoretical study

In the course of our studies on 3 $H$ -1,2-dithiole-3-thione synthesis, a serendipitous reactivity with $\alpha $ -haloketones, in the presence of excess of potassium iodide, has been observed. Instead of the expected reaction of the nucleophile in a remote point of the molecule, we have obtained a product resulted from the electrophile character of the thiocarbonyl moiety on the 3-position of the 1,2-dithiole. In order to obtain an efficient protocol in terms of energy efficiency, this methodology was studied under conventional and microwave heating with similar or better results in the latter conditions. Simplicity and great efficiency in this one-step transformation are some of the advantages of this reaction. Moreover, the results can be explained according to the Pearson’s hard and soft acid base theory.     

Interaction between “dissipative solitons” stabilized by aggregation in excitable kinetics

We consider that a population of individuals governed by the Nagumo model is characterized by predisposition towards aggregation. “Dissipative solitons” interacting are solutions for such system. We changed the possibility of extinction, predicted by Nagumo model, by a uniform background of low population’s density and then we observed relevant effect on interaction between “solitons”.     

An edge-swap heuristic for generating spanning trees with minimum number of branch vertices

This paper presents a new edge-swap heuristic for generating spanning trees with a minimum number of branch vertices, i.e. vertices of degree greater than two. This problem was introduced in Gargano et al. (Lect Notes Comput Sci 2380:355–365, 2002) and has been called the minimum branch vertices problem by Cerulli et al. (Comput Optim Appl 42:353–370, 2009). The heuristic starts with a random spanning tree and iteratively reduces the number of branch vertices by swapping tree edges with edges not currently in the tree. It can be easily implemented as a multi-start heuristic. We report on extensive computational experiments comparing single-start and multi-start variants on our heuristic with other heuristics previously proposed in the literature.     

Korn’s second inequality and geometric rigidity with mixed growth conditions

Geometric rigidity states that a gradient field which is $L^p$ -close to the set of proper rotations is necessarily $L^p$ -close to a fixed rotation, and is one key estimate in nonlinear elasticity. In several applications, as for example in the theory of plasticity, energy densities with mixed growth appear. We show here that geometric rigidity holds also in $L^p+L^q$ and in $L^{p,q}$ interpolation spaces. As a first step we prove the corresponding linear inequality, which generalizes Korn’s inequality to these spaces.