Nanotubes of piezoelectric BNT–BT0.08 obtained from sol–gel precursor

The results of investigations of porous glasses (PG) and porous glasses–ammonium hydrogen sulfate ferroelectric nanocomposites (AHS–PG) are presented. On the basis of dielectric and calorimetric measurements it was shown that in the AHS–PG nanocomposites with average pore size of 44, 68, 95, and 320 nm the anomalies of dielectric permittivity and specific heat similar to those in bulk crystals AHS are observed. An influence of the mean value of pores sizes on the ferroelectric phase transition temperatures of AHS nanocrystals embedded into the porous matrices was determined. It was shown that in AHS–PG dispersion of the dielectric permittivity is observed in both para- and ferro-electric phases and above room temperature AHS–PG nanocomposites exhibit the ionic conductivity.     

Quantum-behaved particle swarm optimization with Gaussian distributed local attractor point

This paper proposes a novel variant of quantum-behaved particle swarm optimization (QPSO) algorithm with the local attractor point subject to a Gaussian probability distribution (GAQPSO). The local attractor point in QPSO plays an important in that determining the convergence behavior of an individual particle. As such, the mean value and standard deviation of the proposed Gaussian probability distribution in GAQPSO are carefully selected. The distributions and diversities of the local attractor points in GAQPSO and QPSO are evaluated and compared. For the purpose of comparison, two variants of the GAQPSO algorithm are proposed by using a mutation probability and other types of probability distribution. The GAQPSO has been comprehensively evaluated on the suite of CEC2005 benchmark functions, and the experimental results are compared with those of the PSO and QPSO algorithms based on different probability distributions. It is shown by the results that the GAQPSO algorithm is an effective approach that can improve the QPSO performance considerably, that is, the GAQPSO algorithm is less likely to be stuck in local optima and hence it can achieve better solutions in most cases.     

Existence and construction of shifted lattice rules with an arbitrary number of points and bounded weighted star discrepancy for general decreasing weights

We study the problem of constructing shifted rank-1 lattice rules for the approximation of high-dimensional integrals with a low weighted star discrepancy, for classes of functions having bounded weighted variation, where the weighted variation is defined as the weighted sum of Hardy–Krause variations over all lower-dimensional projections of the integrand. Under general conditions on the weights, we prove the existence of rank-1 lattice rules such that for any δ>0, the general weighted star discrepancy is O(n^−1+δ) for any number of points n>1 (not necessarily prime), any shift of the lattice, general (decreasing) weights, and uniformly in the dimension. We also show that these rules can be constructed by a component-by-component strategy. This implies in particular that a single infinite-dimensional generating vector can be used for integrals in any number of dimensions, and even for infinite-dimensional integrands when they have bounded weighted variation. These same lattices are also good with respect to the worst-case error in weighted Korobov spaces with the same types of general weights. Similar results were already available for various special cases, such as general weights and prime n, or arbitrary n and product weights, but not for the most general combination of n composite, general weights, arbitrary shift, and star discrepancy, considered here. Our results imply tractability or strong tractability of integration for classes of integrands with finite weighted variation when the weights satisfy the conditions we give. These classes are a strict superset of those covered by earlier sufficient tractability conditions.     

Thermogravimetric analysis of photodegraded acrylic coated lime wood

A series of experiments were carried out to investigate the photodegradation of lime wood (Tilia cordata Mill.) coated with acrylic copolymer during artificial UV/Vis light irradiation for 600 h. Photodegradation of the Paraloid B72 films and Paraloid B72 treated lime wood samples was evaluated by thermogravimetry throughout the irradiation period of 100 h. The results obtained indicate a shifting of the DTG maxima to lower temperatures, which may be related to a decrease in the stability of the copolymer and wood during photodegradation. The decrease of weight loss with increasing time of exposure was observed, while the global kinetic parameters for the main peak increases when increasing exposure time of wood to the UV light. Even when the surface of the wood was covered with a thin layer of acrylic resin, some photodegradation reactions of the wood surface occurred. The modifications in the wood structure may be influenced by the newly formed structures from acrylic resin photodegradation.     

The two-body problem with generalized Lennard-Jones potential

We consider a generalization of the famous Lennard-Jones potential. To study the two-body problem associated to this potential, we use the foliations of the phase space by the invariant sets corresponding to the first integrals of energy and angular momentum. We investigate all possible situations created by the interplay among the constants of integration and the field parameters. We obtain the global flow, and illustrate it in both 3D and 2D. This flow exhibits a great variety of orbits, a homoclinic one included. All phase portraits are interpreted in terms of physical trajectories.     

Order and disorder effects in nano-ZrO(2) investigated by micro-Raman and spectrally and temporarily resolved photoluminescence

Pure and europium (Eu(3+)) doped ZrO(2) synthesized by an oil-in-water microemulsion reaction method were investigated by in situ and ex situ X-ray diffraction (XRD), ex situ Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), steady state and time-resolved photoluminescence (PL) spectroscopies. Based on the Raman spectra excited at three different wavelengths i.e. 488, 514 and 633 nm and measured in the spectral range of 150-4000 cm(-1) the correlation between the phonon spectra of ZrO(2) and luminescence of europium is clearly evidenced. The PL investigations span a variety of steady-state and time resolved measurements recorded either after direct excitation of the Eu(3+) f-f transitions or indirect excitation into UV charge-transfer bands. After annealing at 500 °C, the overall Eu(3+) emission is dominated by Eu(3+) located in tetragonal symmetry lattice sites with a crystal-field splitting of the (5)D(0)-(7)F(1) emission of 20 cm(-1). Annealing of ZrO(2) at 1000 °C leads to a superposition of Eu(3+) emissions from tetragonal and monoclinic lattice sites with monoclinic crystal-field splitting of 200 cm(-1) for the (5)D(0)-(7)F(1) transition. At all temperatures, a non-negligible amorphous/disordered content is also measured and determined to be of monoclinic nature. It was found that the evolutions with calcination temperature of the average PL lifetimes corresponding to europium emission in the tetragonal and monoclinic sites and the monoclinic phase content of the Eu(3+) doped ZrO(2) samples follow a similar trend. By use of specific excitation conditions, the distribution of europium on the amorphous/disordered surface or ordered/crystalline sites can be identified and related to the phase content of zirconia. The role of zirconia host as a sensitizer for the europium PL is also discussed in both tetragonal and monoclinic phases.     

Non-adiabatic transitions near avoided crossings: theory and numerics

We present a review of rigorous mathematical results about non-adiabatic transitions in molecular systems that are associated with avoided crossings of electron energy level surfaces. We then present a novel numerical technique for studying these transitions that is based on expansions in semiclassical wavepackets.     

Polymer colloids and silver nanoparticles hybrid materials

The present study presents two different methods to obtain hybrid material formed by the poly [styrene (ST)–poly(ethylene glycol) methyl ether methacrylate (PEGMA) 1100] and silver (Ag⁰). The aim has been to cover the polymeric particles with Ag⁰ shell. The first method consisted of mixing Ag⁰ nanoparticles dispersion with poly (ST-PEGMA 1100) dispersion, while in the second method, the Ag⁰ nanoparticles have been generated in situ. The hybrid materials have been characterized by MO, dynamic light scattering, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray energy dispersive spectrometry, and ultraviolet–visible spectrophotometry. The results confirm the obtaining of two types of morphologies. In the first case, the nanoparticles have been arranged in the interspatial zones of the polymer particles, while in the second method, the Ag⁰ nanoparticles have covered the polymer particles. Thus, the film obtained using the second method is more suitable for the practical application, as a separation membrane, using the antiseptic properties of Ag⁰.     

Synthesis, structure, and reactivity of dinuclear nickel amino-thiophenolate complexes bearing bridging VO2(OH)2- and VO2(OR)2- coligands

A series of novel mixed ligand dinickel complexes of the type [Ni(II)(2)L(μ-L')](+), where L' is a tetrahedral oxo-alkoxo vanadate (L' = [O(2)V(V)(OR)(2)](-), R = H or alkyl) and L a macrocyclic N(6)S(2) supporting ligand, have been prepared, and their esterification reactivity has been studied. The orthovanadate complex [Ni(2)L(μ-O(2)V(OH)(2))](+) (2), prepared by reaction between [Ni(2)L(μ-Cl)]ClO(4) with Na(3)VO(4) and a phase transfer reagent in CH(3)CN, reacts smoothly with MeOH and EtOH forming the vanadate diesters [Ni(2)L(μ-O(2)V(OMe)(2))](+) (3) and [Ni(2)L(μ-O(2)V(OEt)(2))](+) (4). The dialkyl orthovanadate esters in 3 and 4 are readily transesterified with mono- and difunctional alcohols. Complex 3 can also be generated from 4 by transesterification with MeOH. Complexes 3 and 4 react with diols (ethylene glycol, propylene glycol and diethylene glycol) as well to afford the complexes [Ni(2)L(μ-O(2)V(OH)(OCH(2)CH(2)OH))](+) (5), [Ni(2)L(μ-O(2)V(OCH(2))(2)CH(2))](+) (6), and [Ni(2)L(μ-O(2)V(OCH(2)CH(2))(2)O)] (7). The crystal structures of the tetraphenylborate salts of complexes 3-7 reveal in each case four-coordinate O(2)V(V)(OR)(2)(-) groups bonded in a μ(1,3)-bridging mode to generate trinuclear complexes with a central N(3)Ni(μ-S)(2)(μ(1,3)-O(2)V(OR)(2))NiN(3) core. The stabilization of the four-coordinate V(V)O(2)(OR)(2)(-) moieties is a consequence of both the two-point coordinative fixation to and the steric protection of the bowl-shape binding pocket of the [Ni(2)L](2+) fragment. Cyclic voltammetry experiments reveal that the encapsulated vanadate esters are not reduced in a potential window of -2.0 to +2.5 V vs SCE. The spins of the nickel(II) (S(i) = 1 ions) in 3 are weakly ferromagnetically coupled (J = +23 cm(-1), (H = -2JS(1)S(2))) to produce an S = 2 ground state.     

Micellization Process in Poly(Ether Urethane) Solutions

Poly(ether urethane)s containing different hard segments were investigated by viscometry, fluorescence spectra, polarizing optical microscopy, and scanning electron microscopy. The polarity dependence of the vibrational structure of the pyrene emission spectrum indicated the formation of aggregates at concentrations that are significantly below the critical concentrations that define the separation of dilute‐semidilute domains. Unlike the sample with 4,4'‐methylene diphenylene diisocyanate, the sample with 2,4‐tolylene diisocyanate in hard segments gives a fluorescence spectra in which the pyrene excimer appears. Supermolecular structures associated with the form of spherulites or of spherical micelles were detected by scanning electron microscopy. The results are discussed in correlation with viscometric data and optical microscopy.