Discontinuously propagating waves in the bathoferroin-catalyzed Belousov-Zhabotinsky reaction incorporated into a microemulsion

Three new types of discontinuously propagating waves are reported in the bathoferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction dispersed in water-in-oil Aerosol OT microemulsion. Jumping waves (JWs) are typically observed at or above room temperature and develop from the familiar trigger waves. Bubble waves (BWs) typically emerge from trigger or JWs at similar temperatures, while rotating waves (RWs) evolve from JW at higher temperatures (>40 degrees C). All these waves propagate discontinuously in a saltatory fashion. Other characteristic features include a discontinuous front for BW consisting of small concentric waves (bubbles) and lateral rotation of annular RWs. All three types of waves, as well as segmented but continuously propagating waves, can coexist. A simple model that is able to describe both jumping and segmented waves is described.     

Explicit solutions for depressed masonry arches loaded until collapse—Part I: a one-dimensional nonlinear elastic model

In this paper the equilibrium problem for masonry arches is formulated in terms of a suitable set of nonlinear ordinary differential equations. We show that by making a small number of simple hypotheses it is possible to find the explicit expressions for the displacements and rotations of the cross-sections of an in-plane loaded masonry arch. To this end, the masonry arch is schematised as a curved, one-dimensional nonlinear elastic beam made of a material that is by hypothesis incapable of withstanding significant tensile stresses. In this first part of the two-part paper, the one-dimensional model and the explicit expressions for the displacements and rotations, obtained by integrating the set of differential equations, are presented. In particular, the formal expressions for displacement, stress and strain fields are illustrated in full detail for an explicit, albeit approximate, solution for a statically determinate depressed arch subjected to a uniform vertical load.     

Evaluation of Activation Energies for Pairwise and Non-Pairwise Hydrogen Addition to Propyne Over Pd/Aluminosilicate Fiberglass Catalyst by Parahydrogen-Induced Polarization (PHIP)

Hydrogenation of propyne to propene over Pd/aluminosilicate fiberglass catalyst in the temperature range 175–350 °C was investigated with the use of parahydrogen-induced polarization (PHIP) technique. Activation energies for both pairwise and non-pairwise H₂ addition routes were estimated. It was found that at 175–275 °C the activation energies for hydrogen addition to the triple bond of propyne have similar values (about 60–70 kJ/mol) for both routes of hydrogen addition. At higher temperatures (275–350 °C), the rate constant for pairwise hydrogen addition reaches a maximum value while the rate constant for non-pairwise hydrogen addition continues to increase with increasing temperature.     

Monolithic white LEDs: Approaches, technology, design

The results of investigations of monolithic white InGaAlN LEDs with an active region containing several thin InGaN layers, emitting in the range from blue to yellow-green, and separated by short-period InGaN/GaN superlattices, are presented. The influence of the growth conditions and layer sequence in the active region on the optical properties of monolithic white LEDs was studied with the aim of controlling their color parameters.     

Synthesis of 2-(polyfluoromethyl)pyrimido-[1,2-a]benzimidazole-4-carbaldehyde derivatives

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Solving a classification task by spiking neural network with STDP based on rate and temporal input encoding

This paper develops local learning algorithms to solve a classification task with the help of biologically inspired mathematical models of spiking neural networks involving the mechanism of spike-timing-dependent plasticity (STDP). The advantages of the models are their simplicity and, hence, the potential ability to be hardware-implemented in low-energy-consuming biomorphic computing devices. The methods developed are based on two key effects observed in neurons with STDP: mean firing rate stabilization and memorizing repeating spike patterns. As the result, two algorithms to solve a classification task with a spiking neural network are proposed: the first based on rate encoding of the input data and the second based on temporal encoding. The accuracy of the algorithms is tested on the benchmark classification tasks of Fisher's Iris and Wisconsin breast cancer, with several combinations of input data normalization and preprocessing. The respective accuracies are 99% and 94% by F1-score.     

Conformational properties of cyanomethoxy calix[4]arenes

O-Alkylation of the dinitro calix[4]arene 2, easily available by selective ipso-nitration of the di-cyanomethyl ether 1, with allylbromide (DMF/Cs2CO3) gave tetraethers 3 and 4 with anti- and syn-orientations of the two allyl ether residues. The two possible stereoisomers of in the partial cone and 1,2-alternate conformation exist as an equilibrium mixture which could be quantitatively analysed by 1H NMR spectroscopy. The temperature dependence of this equilibrium leads to deltaH0 = -7.6 to -9.7 kJ mol(-1) in different solvents (tetrachloroethane, benzene, dimethylsulfoxide). Since 3(1,2-alt) could be obtained in pure form, its isomerisation to the equilibrium mixture with 3(paco) could be followed also kinetically. An activation energy of E(a) = 110.5 kJ mol(-1) was found for this reaction in DMSO-d6. The results were confirmed by similar studies with tetraethers 5 and 6 obtained by O-allylation of 1, although exact thermodynamic and kinetic studies were not possible in this case, since the NMR signals of the respective isomers were strongly overlapping. Single crystal X-ray structures were obtained for 2, 3(1,2-alt), 4(paco) and 5(1,2-alt).