Stabilisation Effect of Calcium Ions on Polymer Network in Hydrogels Derived from a Lyotropic Phase of Hydroxypropylcellulose

The process of crosslinking of the hydrogel, derived from lyotropic liquid crystalline (LLC) phases of hydroxypropylcellulose/acrylic acid-water, by calcium ions was studied by means of Raman and dielectric spectroscopy. Formation of salt by poly(acrylic acid) and calcium ions, resulting in hydrogel crosslinking, induces differences in Raman spectra of the hydrogel before and after the crosslinking. The crosslinking results in significant increase in the activation energy of β-relaxation of poly(acrylic acid). This is a direct consequence of restriction in motions of carboxylic groups of poly(acrylic acid) due to calcium salt formation. Thus, the crosslinking improves polymer network stability in the hydrogel in the swollen state.     

On Trajectories of Analytic Gradient Vector Fields

Let f:Rⁿ,0→R,0 be an analytic function defined in a neighbourhood of the origin, having a critical point at 0. We show that the set of non-trivial trajectories of the equation xdot;=∇f(x) attracted by the origin has the same ?ech-Alexander cohomology groups as the real Milnor fibre of f.     

Synthesis and characterization of thiophene/3-alkylthiophene random cooligomers

Several random cooligomers based on thiophene and β-substituted alkyl derivatives, i.e. 3-methyl- and 3-octylthiophene, have been chemically synthesized by an oxidative coupling reaction in the presence of iron(III) chloride. The powdered samples were characterized by TGA, FTIR, UV and cyclic voltammetry measurements. The influence of the alkyl substituent on the homo/cooligomer stability, conjugation length, degree of polymerization and presence of defects is discussed. Electronic Publication     

Power controlled soliton stability and steering in lattices with saturable nonlinearity

Dynamical properties of discrete solitons in nonlinear Schr?dinger lattices with saturable nonlinearity are studied in the framework of the one-dimensional discrete Vinetskii-Kukhtarev model. Two stationary strongly localized modes, centered on site (A) and between two neighboring sites (B), are obtained. The associated Peierls-Nabarro potential is bounded and has multiple zeros indicating strong implications on the stability and dynamics of the localized modes. Besides a stable propagation of mode A, a stable propagation of mode B is also possible. The enhanced ability of the large power solitons to move across the lattice is pointed out and numerically verified.     

Quantum sum formulae for the collision-induced spectroscopies: Molecular systems as H2-H2

Quantum expressions for the second moment of collision-induced spectra are developed in the low-density limit. Previous work by Moraldi is extended to account for the rotational structure of colliding linear molecules; isotropic interaction is assumed. Computations of the lowest three moments are presented for the case of infrared absorption and Raman scattering of molecular hydrogen pairs at temperatures from 77 to 300 K. The radial distribution functions of pairs, mean energy and angular momentum, which are required for that purpose, are obtained for the case of H₂ molecules interacting with H₂, and compared with their classical counterparts. The simple classical approximations with lowest-order Wigner-Kirkwood quantum corrections serve as an accurate representation of the quantum expressions at large separations and may be sufficient for massive systems at high temperatures.     

Mikrobestimmung von Spuren von Saponinglykosiden in ”nicht-saponinführendem“ Pflanzenmaterial

Zusammenfassung Eine Methode zur densitometrischen Mikrobestimmung von Standardsaponinen (Digitonin und Aescin) nach dem HämolySciest auf Dünnschichtplatten wurde beschrieben. Diese Methode wurde zum Nachweis und zur Bestimmung unbekannter Saponine in Pflanzenextrakten herangezogen. Eichkurven für den HämolySciest und auch für die HClO_4– und Anisaldehydteste wurden angegeben. Im Bereich von 6 bis 25g Saponin im Chromatogrammfleck wurde ein Umrechnungsfaktor für 10g Saponin benutzt. Wegen der Spezifität und der hohen Empfindlichkeit des HämolySciestes nach der chromatographischen Trennung von Begleitstoffen eignet sich das densitometrische Verfahren vorzüglich zur eindeutigen Feststellung und serienmäßigen Bestimmung von Saponinen in Extrakten von Pflanzenmaterial, das in der Fachliteratur als nichtsaponinfuhrend gilt.

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Microdetermination of traces of saponin glycosides in plant material not containing saponin

Summary A method of densitometric microdetermination of standard saponins (digitonin and aescin) according to the hemolysis test on thin-layer plates was described. This method was used to demonstrate and determine unknown saponins in plant extracts. Calibration curves were given for the hemolysis test and also for the HClO_4– and anisaldehyde tests. In the region from 6 to 25g saponin in the chromatogram spot, a conversion factor for 10g saponin was used. Because of the specificity and the high sensitivity of the hemolysis test, after the chromatographic separation of concomitant substances the densitometric method is eminently suitable for unequivocal detection and determination of saponins in series of extracts of plant material which as previously been regarded in the specialist literature as not containing saponin.

     

Nature of versatile chemisorption on TiC(111) and TiN(111) surfaces

Density-functional calculations on the polar TiX(111) (X = C, N) surfaces show (i) for clean surfaces, strong Ti3d-derived surface resonances (SR’s) at the Fermi level and X2p-derived SR’s deep in the upper valence band and (ii) for adatoms in periods 1-3, pyramidic trends in atomic adsorption energies, peaking at oxygen (9 eV). A concerted-coupling model, where adatom states couple to both kinds of SR’s in a concerted way, describes the adsorption. The chemisorption versatility and the general nature of the model indicate ramifications and predictive abilities in, e.g., growth and catalysis.     

Effects of Orange Leaves Extraction Conditions on Antioxidant and Phenolic Content: Optimization Using Response Surface Methodology

In the last few years, bioactive components or their extraction techniques are gaining special interest in scientific areas. In this framework, orange leaves were used for preparation of extracts with high content of biologically active compounds. To optimize the extraction process, three levels and three variables of Box–Behnken design with response surface methodology were applied. Investigated responses were the total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, cupric ion reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP). Independent variables were methanol concentration (10–90%), temperature (20–60°C), and extraction time (60–180?min). Experimentally obtained results were fit into a second-order polynomial model with multiple regression. Analysis of variance was used to estimate model fitness and determine optimal conditions for processing. Estimated optimal conditions were 90% methanolic solution, 60°C and 180?min using these parameters; the predicted values of investigated responses were 43.19?mg GAE/g (GAE: gallic acid equivalents), 43.04?mg TE/g (TE: trolox equivalents), 139.34 and 93.76?mg TE/g for TPC, DPPH, CUPRAC, and FRAP, respectively. The obtained optimal conditions could be considered as an alternative strategy for developing novel functional products.     

Adsorption of lead(II), cadmium(II) and dysprosium(III) from aqueous solutions using mesoporous silica modified with phosphonic acid groups

The mesoporous silica samples with different concentrations of phosphonic acid groups on the surface were obtained by direct template synthesis. The block-copolymer Pluronic P123 was used as a template, and sodium meta-silicate with diethylphosphatoethyltriethoxysilane as precursors. According to the SAXS diffractograms, mesoporous silica samples have a p6mm hexagonal symmetry. In addition, we used sol–gel method to synthesize xerogel with the same groups for comparison. All samples possess high values of specific surface area 615–730?m²/g and sorption pore volume. FTIR and potentiometric titration methods were used to investigate the surface layer of these samples. Sorption properties of the samples with phosphonic acid groups were studied in respect to a row of metal cations, among which we focused on lead(II), cadmium(II), and dysprosium(III) cations.

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