A study of selected phytoestrogens retention by reverse osmosis and nanofiltration membranes - the role of fouling and scaling

Fouling and scaling are common phenomena that accompany membrane filtration and are caused by the presence of organic and inorganic matter in water, which may affect the removal of low-molecular mass organic micropollutants. Comparative filtration of deionized water containing selected phytoestrogens (biochanin A, daidzein, genistein, and coumestrol) was carried out using one new membrane and one contaminated with organic or inorganic matter. Two commercial Osmonics DS membranes were selected for the research, reverse osmosis DS3SE and nanofiltration DS5DK. Filtration was carried out in the dead-end mode. Higher removal of phytoestrogens was caused by reverse osmosis and retention depended on the molar mass of the compound. The decrease in membrane efficiency associated with fouling or scaling brings about an increase in the retention coefficient of phytoestrogens during both reverse osmosis and nanofiltration. The highest increase in phytoestrogen retention was found for the nanofiltraton membrane which was more susceptible to fouling than the osmotic one. This confirms the effect of membrane porosity on the phenomenon studied. The increase in micropollutants removal observed after fouling or scaling was caused by the modification of the membrane surface, hindered diffusion of the compound, and intensified or limited adsorption of micropollutants on the membrane surface.     

A mechanistic study on the fragmentation of peptide‐derived Amadori products

Gas phase fragmentation of peptide‐derived Amadori products was investigated using synthetic compounds regioselectively deuterated as well as labeled with ¹⁸O at aminofructose moiety. The eliminated molecule CH₂O contains exclusively protons attached to carbon C6 of the aminofructose moiety. The hydrogen atoms connected with the carbon C1 of the aminofructose moiety are partially eliminated as a component of water molecules during the dehydration process and partially dislocated within the fragmented peptide molecule. The labeled oxygen atom attached to the carbon C2 is eliminated in 100% along with the first loss of water. The MS³ experiments revealed that the product ion formed by triple dehydration of the Amadori product does not eliminate the formaldehyde molecule. On the basis of these observations we proposed a hypothetical mechanism of Amadori products' fragmentation. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct products of automorphism groups of graphs

In this article we study the product action of the direct product of automorphism groups of graphs. We generalize the results of Watkins [J. Combin Theory 11 (1971), 95–104], Nowitz and Watkins [Monatsh. Math. 76 (1972), 168–171] and W. Imrich [Israel J. Math. 11 (1972), 258–264], and we show that except for an infinite family of groups S_n × S_n, n≥2 and three other groups D₄ × S₂, D₄ × D₄ and S₄ × S₂ × S₂, the direct product of automorphism groups of two graphs is itself the automorphism group of a graph. © 2009 Wiley Periodicals, Inc. J Graph Theory 62: 26–36, 2009     

A tabu search algorithm for the minmax regret minimum spanning tree problem with interval data

This paper deals with the strongly NP-hard minmax regret version of the minimum spanning tree problem with interval costs. The best known exact algorithms solve the problem in reasonable time for rather small graphs. In this paper an algorithm based on the idea of tabu search is constructed. Some properties of the local minima are shown. Exhaustive computational tests for various classes of graphs are performed. The obtained results suggest that the proposed tabu search algorithm quickly outputs optimal solutions for the smaller instances, previously discussed in the existing literature. Furthermore, some arguments that this algorithm performs well also for larger instances are provided.     

Recent achievements in AMMONO-bulk method

In this paper we present progress made recently in the development of the growth of truly bulk GaN crystals by the ammonothermal method in basic environment. High quality 2-in c-plane GaN seeds are shown. Non-polar wafers can also be cut out from thick GaN crystals grown by ammonothermal method. Perfect crystallinity manifests in very narrow peaks in X-ray rocking curves (the full width at half maximum equals about 15 arcsec). GaN epilayers deposited on these substrates exhibit intrinsic narrow exciton lines, which are very sensitive to the optical selection rules typical for hexagonal symmetry, proving the truly non-polar character of such AMMONO-GaN substrates. Other challenges like homogenous insulating properties or high p-type conductivity have been also accomplished by means of ammonothermal method. Semi-insulating crystals of resistivity up to 10¹¹ Ω cm and p-type conductivity within hole concentration up to 10¹⁸ cm⁻³ are already available in diameters up to 1.5-in.     

Electron-ion recombination rate constant in dense gaseous Kr/CH4 mixtures

The rate constant of bulk electron-ion recombination is calculated for dense gaseous krypton doped with methane. In the calculations, the electron scattering is modeled by experimental, energy-dependent collision cross-sections. The recombination rate constant is found to increase with increasing methane concentration, due to efficient dissipation of electron energy in vibrationally inelastic e-CH₄ collisions.     

Integer solution of a set of bilinear equations

An efficient method for a design of transmultiplexer filters is suggested. The perfect reconstruction conditions lead to the bilinear equations for FIR filters coefficients. The method of solving these equations results from the presented theorem. Usefulness of the algorithm in fixed-point arithmetic is the crucial issue. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microspheres by dispersion polymerization of lactides and ϵ-caprolactone

Polyester microspheres were synthesized by the ring-opening polymerization of lactides (racemate or optically active L,L-isomer) and ϵ-caprolactone. Polymerizations were carried out in the 1,4-dioxane-heptane mixed solvents in the presence of poly(dodecyl acrylate)-g-poly(ϵ-caprolactone) (poly(DA-CL)) used as surface-active agent. Polymerizations were initiated with tin(II) 2-ethylhexanoate (lactides), diethylaluminum ethoxide or sodium trimethylsilanolate (ϵ-caprolactone). In the studies of the polymerization of lactides, relations were determined between diameters, the distribution of diameters of synthesized microspheres, and the structure of poly(DA-CL). It was found that it is possible, depending on thermal treatment of microspheres after synthesis, to obtain polylactide microspheres differing in the degree of crystallinity. Kinetics of the dispersion pseudoanionic and anionic polymerizations of ϵ-caprolactone were also investigated and the results of these studies were compared with the data for the corresponding polymerizations of ϵ-caprolactone in solution.     

Multicomponent lb films containing pre-formed poly(3-n-Alkylthiophenes)

The paper reports on the deposition of two-component Langmuir-Blodgett films containing poly(3-n-alkylthiophenes) with “film-builders” —low-molecular-weight amphiphilic molecules facilitating film formation. Fatty acids and 3-n-octadecylpyrrole were used as builders. The thicknesses and electric permittivities of the films were determined by measurements of the surface plasmon resonance; it was found that the former parameter is controlled by the length of the builder molecules. The electrical conductivities of the deposited films were of the order of 1 μS/m. The contact with oxides gives rise to an abrupt increase of conductivity by several orders of magnitude, followed by a decrease due to an irreversible destruction of the π-electron system of the polymer.