Improvement of luminescent materials composed of Tb(III) ions,WO3 nanoparticles and silica xerogel as a matrix

Nanoparticles of tungsten trioxide, WO₃, are used to enhance the luminescence emission intensity of terbium(III) ions embedded in a silica matrix. Optically active components have been incorporated into silica xerogel by impregnation of silica xerogel immersed firstly in WO₃ sol and subsequently in a solution with Tb(III). Photoluminescence studies make it possible to describe a plausible mechanism of the Tb(III) enhanced luminescence that could be attributed to energy transfer via excited WO₃ nanoparticles to Tb(III) ions in the system: Tb(III) ions–WO₃ nanocrystals–SiO₂. The effect related to WO₃ nanoparticles of various sizes influences not only changes in the emission intensity and band shifting of WO₃ nanostructures but also the same spectral parameters of the emitting Tb(III) ions.     

Preparation and characterization of lithium niobate as a novel photocatalyst in hydrogen generation

Several chemical compounds based lithium niobate have been tested in the reaction for the photocatalytic hydrogen generation. The photocatalysts have been prepared by impregnation of Nb₂O₅ in the aqueous solution of lithium hydroxide and then the calcination at the temperature range of 400-650 °C. In this report, we present the interesting study showing that the most active catalyst for the photocatalytic generation of hydrogen is the one containing two lithium niobate phases such as LiNbO₃ and LiNb₃O₈. It means that the lithium niobates based catalyst without any further modification or doping can be applied as a novel material for this process.     

On residualities in the set of Markov operators on

We show that the set of those Markov operators on the Schatten class such that , where is one-dimensional projection, is norm open and dense. If we require that the limit projections must be on strictly positive states, then such operators form a norm dense . Surprisingly, for the strong operator topology operators the situation is quite the opposite.

     

The process of 4‐hydroxybiphenyl synthesis from 4‐isopropylbiphenyl

The kinetics of the oxidation of 4‐isopropylbiphenyl ( 1 ) in the liquid phase by oxygen to 1‐(1,1′‐biphenyl‐4‐yl)‐1‐methylethyl hydroperoxide ( 2 ) was investigated. The oxidizability of 1 in the temperature range from 60°C to 120°C and the overall energy activation of oxidation were determined. Long‐term oxidation of 1 to 2 in the temperature range of 80–120°C was investigated, and the yield and selectivity of the process were determined. Pure 2 was obtained, and its properties were defined. 4‐Hydroxybiphenyl was obtained as a result of the acidic decomposition of 2 . © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 527–532, 2008     

An acoustic scattering problem for periodic,inhomogeneous media

We study the problem of the scattering by a periodic, inhomogeneous, penetrable medium. Using the Dirichlet-to-Neumann operator from the classical formulation of the problem we derive a variational equation and give regularity result to show the equivalence of both formulations. We present certain uniqueness results, which by the Fredholm alternative yield existence of the solution and its continuous dependence on the incoming wave. We prove existence of a solution for special incident waves even if there is no uniqueness. A result about analytical dependence of the solution on the wave number and the incident angle is given. © 1998 B. G. Teubner Stuttgart—John Wiley & Sons, Ltd.     

A comparison of asymptotic analytical formulae with finite-difference approximations for pricing zero coupon bond

In this paper we solve numerically a degenerate parabolic equation with dynamical boundary condition for pricing zero coupon bond and compare numerical solution with asymptotic analytical solution. First, we discuss an approximate analytical solution of the model and its order of accuracy. Then, starting from the divergent form of the equation we implement the finite-volume method of Song Wang (IMA J Numer Anal 24:699–720, 2004) to discretize the differential problem. We show that the system matrix of the discretization scheme is a M-matrix, so that the discretization is monotone. This provides the non-negativity of the price with respect to time if the initial distribution is nonnegative. Numerical experiments demonstrate second order of convergence for difference scheme when the node is not too close to the point of degeneration.     

Uniqueness in the inverse transmission scattering problem for periodic media

We study the problem of the scattering by a periodic, penetrable medium. We present certain uniqueness results and give the integral equation formulation of the transmission problem which is of Fredholm type and provides the existence and continuous dependence result. Next we investigate the question of the uniqueness for the inverse transmission problem, i.e. we concentrate on the amount of information that is necessary to completely determine the profile and constitutive parameters of the scattering grating. Copyright © 1999 John Wiley & Sons, Ltd.     

Chemiluminogenic features of 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates alkyl substituted at the benzene ring in aqueous media

10-Methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates bearing alkyl substituents at the benzene ring were synthesized, purified, and identified. In the reaction with OOH(-) in basic aqueous media, the cations of the compounds investigated were converted to electronically excited 10-methyl-9-acridinone, whose relaxation was accompanied by chemiluminescence (CL). The kinetic constants of CL decay, relative efficiencies of light emission, chemiluminescence quantum yields, and resistance toward alkaline hydrolysis were determined experimentally under various conditions. The mechanism of CL generation is considered on the basis of thermodynamic and kinetic parameters of the reaction steps predicted at the DFT level of theory. The chemiluminescence efficiency is the result of competition of the electrophilic center at C(9) between nucleophilic substitution by OOH(-) or OH(-) and the ability of the intermediates thus formed to decompose to electronically excited 10-methyl-9-acridinone. Identification of stable and intermediate reaction products corroborated the suggested reaction scheme. The results obtained, particularly the dependency of the "usefulness" parameter, which takes into account the CL quantum yield and the susceptibility to hydrolysis, on the cavity volume of the entity removed during oxidation, form a convenient framework within which to rationally design chemiluminescent 10-methyl-9-(phenoxycarbonyl)acridinium cations.     

Addition–elimination versus Tishchenko reaction in the gas phase

Gas phase reactions of the substituted phenide ions with methyl formate have been studied. It was found that the results of these reactions depend mainly on the basicity of the phenide ion, which is related to the presence of the electron‐accepting or electron‐donating substituents in the benzene ring. It was shown that the phenide ions substituted with electron‐withdrawing groups react with methyl formate in the gas phase in a two‐step reaction. The first step that proceeds according to the typical addition–elimination mechanism results in the formation of the anion of the respective benzaldehyde derivative with the negative charge located either in the aldehyde group (acyl anion) or in the benzene ring (phenide anion) in position ortho to an aldehyde moiety. In the second step, the preliminary‐formed anion reacts with the second molecule of methyl formate yielding formally product of the second addition–elimination reaction. Theoretical calculations as well as collision induced dissociation spectra of the model compounds suggest that this reaction proceeds according to the Tishchenko reaction mechanism yielding the respective phthalide anion. According to our knowledge, this is the first example of the Tishchenko‐type reaction in the gas phase. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification of proteins interacting with ammodytoxins in Vipera ammodytes ammodytes venom by immuno-affinity chromatography

In order to perform their function, proteins frequently interact with other proteins. Various methods are used to reveal protein interacting partners, and affinity chromatography is one of them. Snake venom is composed mostly of proteins, and various protein complexes in the venom have been found to exhibit higher toxicity levels than respective components separately. Complexes can modulate envenomation activity of a venom and/or potentiate its effect. Our previous data indicate that the most toxic components of the Vipera ammodytes ammodytes (Vaa) venom isolated so far—ammodytoxins (Atxs)—are contributing to the venom’s toxicity only moderately; therefore, we aimed to explore whether they have some interacting partner(s) potentiating toxicity. For screening of possible interactions, immuno-affinity chromatography combined with identification by mass spectrometry was used. Various chemistries (epoxy, carbonyldiimidazole, ethylenediamine) as well as protein G functionality were used to immobilize antibodies on monolith support, a Convective Interaction Media disk. Monoliths have been demonstrated to better suit the separation of large biomolecules. Using such approach, several proteins were indicated as potential Atx-binding proteins. Among these, the interaction of Atxs with a Kunitz-type inhibitor was confirmed by far-Western dot-blot and surface plasmon resonance measurement. It can be concluded that affinity chromatography on monolithic columns combined with mass spectrometry identification is a successful approach for screening of protein interactions and it resulted with detection of the interaction of Atx with Kunitz-type inhibitor in Vaa venom for the first time.