Special manifolds and shape fibrator properties

Our main interest in this paper is further investigation of the concept of (PL) fibrators (introduced by Daverman [R.J. Daverman, PL maps with manifold fibers, J. London Math. Soc. (2) 45 (1992) 180-192]), in a slightly different PL setting. Namely, we are interested in manifolds that can detect approximate fibrations in the new setting. The main results state that every orientable, special (a new class of manifolds that we introduce) PL n-manifold with non-trivial first homology group is a fibrator in the new category, if it is a codimension-2 fibrator (Theorem 8.2) or has a non-cyclic fundamental group (Theorem 8.4). We show that all closed, orientable surface S with χ(S)<0 are fibrators in the new category.     

Bifocal-polarization holographic lens

We present a holographic lens with novel features recorded in an azopolymer film. Two holographic modulations, bulk birefringence and surface relief, are induced in the medium at the same time. The resultant holographic element has two focal planes, and the polarization of light in the focal points depends on the polarization of the incident light. Applications of this device for writing-reading information in two planes simultaneously or separately are described.     

Thermal behavior of some aromatic copolyethers containing a propylenic spacer

The main objective of this paper is to study the thermal stability of some aromatic copolyethers containing a propylenic spacer. Some of the investigated copolyethers displayed a liquid crystalline (LC) behavior, with the presence of the mesogenic groups in the main chain, inducing high values of the thermal transition temperatures. As a consequence, a thermal stability study was necessary to establish the maximum temperature value for the LC behavior characterization. A thermal degradation mechanism is proposed, taking into consideration the azobenzenic unit as the weakest link in the polymer chain and thus, the starting point of the thermal degradation process. The degradation mechanisms were correlated with the chemical structure and the polarity and conformation of the chains. Conformational analysis was performed using molecular simulations. Freeman-Caroll and Coats-Redfern methods were used to calculate some kinetic characteristics.     

Organic Ion Exchangers. Synthesis and Their Behaviour in the Retention of Some Metal Ions

Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4-vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N⁺ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl₄]⁻ complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N⁺ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with  CH₃ as substituent on N⁺ atoms while [GaCl₄]⁻ complex anion by the resin with  C₄H₉ as substituent on N⁺ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH₂OH · HCl in the presence of C₂H₅OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups. This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NOequation/tex2gif-stack-1.gif anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10⁻² M concentration for Zn(NO₃)₂ the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO₃)₂ solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO₃)₃ solution is not retained.     

Synthesis of Polyvinylacetate‐Sodium Montmorillonite Hybrids by Emulsion Polymerization in the Presence of Anionic Surfactants

The emulsion polymerisation of vinyl acetate (VAc) in presence of sodium dodecylsulphate (SDS) and sodium montmorillonite (NaMMT) is used in order to achieve polymer‐clay hybrids. The influence of the polyvinylacetate (PVAc), SDS, and PVAc‐SDS complex on the NaMMT structure also was investigated. The VAc emulsion polymerization rate exhibits a maximum as the NaMMT concentration increases. The XRD patterns correspond to hybrids with intercalated structure. If a water soluble comonomer, ammonium sulphato ethylmethacrylate (ASEMA) is used for copolymerization with VAc, a exfoliated hybrid structure (from XRD spectra) is obtained. The solid materials were analysed by TGA, FTIR, XRD, SEM, and TEM.     

Effects of the nanoassociation of hexadecyltrimethoxysilane precursors on the sol–gel process

Modifications to the refractive indices of meso-structured organic–inorganic films caused by variations in the mole fraction of precursors in ethanolic solutions were investigated. The refractive indices were dependent on the mole fraction of C₁₆TMS (hexadecyltrimethoxysilane) and of the C₁₆TMS/TMOS (tetramethoxysilane) (1/1) mixture in ethanol. The dependency was determined to be nonlinear, and the phenomenon was attributed to self-assembly caused by the long alkyl groups (C₁₆) on the C₁₆TMS. Changes in the maximum decreasing rate of d_n/d_x values [(d_n/d_x)_max—for d_n/d_x estimation, the curves from Fig. 1 were associated with a polynomial; using a dedicated program, d_n/d_x was calculated; maximum values of d_n/d_x were taken into account and were included in Table 1)] were used to distinguish the behavior of alcoholic precursor mixtures. In the case of using pyrene as a fluorescent probe, the ratio between two peaks from the pyrene emission spectra (I₁/I₃) strongly decreased as hydrophobic micro-surroundings formed due to the self-assembly process. The UV–VIS spectra of a cationic dye solution, R6G, was studied because dilute solutions of the dye in equilibrium form measurable ratios of dimers and monomers. The absorbance was modified as micro-surroundings with different polarities were formed. These three methods demonstrated that nano-structuration was present prior to the occurrence of the sol–gel process. The combination of C₁₆TMS with other alkyltrialkoxysilane precursors having hydrocarbon chain lengths between C₁ and C₈ provided further evidence for a nonlinear dependence of the refractive indice and fluorescence spectra of pyrene. The properties of the final hybrids obtained by the sol–gel process were significantly affected by the precursor hydrocarbon chain lengths. DSC, XRD and FTIR measurements were used to show the plasticizing phenomena of C₁₆ as other alkyltrialkoxysilanes (i.e., C₁–C₈) were added.

Fuzzy sets and join spaces associated with rough sets

Let μ _X be the rough membership function. One compares μ _A with μ_A∪B and μ_A∪B, by the associated hyperoperations. One finds a condition such that a functionμ ε [0, 1] ^H may be a rough membership function.     

Transition metal complexes with thiosemicarbazide‐based ligands. XLIV. Aqua(3‐hydroxy‐5‐hydroxymethyl‐2‐methylpyridine‐4‐carboxaldehyde 3‐­methylisothiosemicarbazone‐κ3O,N1,N4)nitratocopper(II) nitrate

The title complex, [Cu(NO₃)(C₁₀H₁₄N₄O₂S)(H₂O)](NO₃), is the first metal complex with a Schiff base derived from iso­thio­semicarbazide and pyridoxal (pyridoxal is 3‐hydroxy‐5‐­hydroxy­methyl‐2‐methyl­pyridine‐4‐carbox­aldehyde). The Cu^II environment is a square pyramid, the equatorial plane of which is formed by the tridentate ONN‐coordinated iso­thio­semicarbazone and one water mol­ecule, while the nitrate ligand is in the apical position. The existence of numerous strong intermolecular hydrogen bonds, and weak C—H?O and C—H?π interactions, leads to a three‐dimensional supramolecular structure.     

Screening of antioxidant activity and volatile compounds composition of Chamerion angustifolium (L.) Holub ecotypes grown in Lithuania

Since biological activity of medicinal plants is dependent on cultivation area, climatic conditions, developmental stage, genetic modifications and other factors, it is important to study flora present in different growing sites and geographical zones. This study was focused on screening of antioxidant activity of C. angustifolium harvested in six different locations in Lithuania. The total contents of phenolic compounds, flavonoids and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity were evaluated by spectrophotometric methods. A correlation between radical scavenging activity and total phenolic compounds content was observed (correlation coefficient 0.98). HPLC with online post-column DPPH radical scavenging reaction detection was used for the separation of extracts. Oenothein B, rutin and one unidentified compound were predominant. Volatile compounds were analysed using solid-phase microextraction coupled with gas chromatography–mass spectrometry. Based on the analysis of volatiles, all samples were classified into two chemotypes: (I) with predominant α- and β-caryophyllenes and (II) with predominant anethole.     

Investigation of ICP-MS spectral interferences in the determination of Rh, Pd and Pt in road dust: Assessment of correction algorithms via uncertainty budget analysis and interference alleviation by preliminary acid leaching

A method for classification of the potential spectral interferences in inductively coupled plasma mass spectrometry (ICP-MS) was proposed based on statistical assessment of the interfering signals. The concept was applied to investigate the variety of spectral interferences over the isotopes of Rh, Pd and Pt concerning their analysis in road dust samples. For the significant interferences the applicability of mathematical corrections using two alternative algorithms were studied by uncertainty budget analysis and the approach resulting in lower combined uncertainty of the corrected signals was selected. Further the uncertainty evaluation was used for assessment of the most appropriate Pd isotope to be measured. The adequateness of the mathematical corrections for Rh and Pd was highly relevant to the number of elements causing spectral interferences and the relative analyte/interferent concentrations. This was overcome by preliminary road dust leaching with 0.35 mol l⁻¹ hydrochloric acid. Interferents present as easily soluble salts were substantially removed form the samples while the platinum group metals were not leached which allowed a relative analyte preconcentration to be obtained. For the leached samples the isotopes of Rh and Pd were still spectrally interfered from Sr, Y and Pb but at considerably lesser degree thus after mathematical correction the ICP-MS analysis of Rh, Pd and Pt was reliable and robust using the isotopes 103, 105 and 195, respectively. The method was validated via an alternative analysis based on selective separation of the platinum group metals by microwave-assisted cloud point extraction.