Special sets of the Hermitian surface and indicator sets

An interesting connection between special sets of the Hermitian surface of PG(3,q²), q odd, (after Shult 13 ) and indicator sets of line‐spreads of the three‐dimensional projective space is provided. Also, the CP‐type special sets are characterized. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 18–24, 2008     

A dark radiation era prior to the inflationary phase

A cosmological model dominated at the beginning by a dark radiation followed by a period of inflation is presented. This model is based on a Randall–Sundrum II type brane-world. Current observational data are used to fix the parameters associated to the dark radiation.     

Torsion theories and Galois coverings of topological groups

For any torsion theory in a homological category, one can define a categorical Galois structure and try to describe the corresponding Galois coverings. In this article we provide several characterizations of these coverings for a special class of torsion theories, which we call quasi-hereditary. We describe a new reflective factorization system that is induced by any quasi-hereditary torsion theory. These results are then applied to study various examples of torsion theories in the category of topological groups.     

Extinction coefficient of polyolefin foams

The extinction coefficient of a collection of polyolefin foams was investigated experimentally and theoretically. Transmittance spectra were measured with Fourier transform infrared spectroscopy (FTIR) for samples of various thicknesses and different chemical compositions, densities, colors and structural characteristics. The extinction coefficients were then calculated by applying Beer's law. The results showed that the extinction coefficient decreased with the mean cell size and that this was the main structural parameter influencing the extinction coefficient of the foams under study. The experimental results agreed well with the Glicksman model. Moreover, the total thermal conductivity was calculated in terms of the Rosseland equation with an accuracy of 5%. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1608–1617, 2005     

New jaspamide derivatives with antimicrofilament activity from the sponge Jaspis splendans

A reinvestigation of Jaspis splendans afforded the novel compounds jaspamide D-G plus the known compounds jaspamide and jaspamides B and C. All compounds exhibited potent cytotoxic activities and were shown to cause microfilament disruption. Biological activity and structural elucidation are reported here.     

DTG-DTA study of sewage sludge used in the sorption of Cd2+ and Co2+

The present study was carried out for evaluating the retention behavior of sanitary sewage in relation to cadmium and cobalt ions in an ascendant continuous-flow reactor. It was found that the studied sludge presented a high assimilation of the metals, probably due to the presence of anionic groups, which favors adsorption and complexation processes. Thermal analyses of the samples showed a shift in the thermal decomposition of the ‘in natura’ sludge, when compared with those of the samples spiked with the metals, confirming the possibility of interactions between the heavy metals and the anionic groups present in the sludge.     

Wide-field polarimetric analysis of photoinduced birefringence in azo-dye-doped thin films: irradiance and time dependence

We have investigated by wide field polariscopy the behaviour of photoinduced birefringence (PIB) in sol–gel hybrid disperse red 1 (DR1) doped films. This technique allows the mapping of the local values of a bell-shaped pump beam irradiance and those of the corresponding photoinduced birefringence. By means of a point-to-point correlation of these maps, we have tracked the dependence of PIB, simultaneously and continuously, on exposure times and pump irradiances. We have then applied some of the available theoretical models, representing birefringence as an analytical function of irradiance and time, to interpolate the experimental PIB data. As compared to the usual PIB measurements, which neglect the spatial distribution of the pump irradiance, our results provide a more detailed and reliable empirical basis on which models of the orientational mechanisms of the photoisomerizable molecules can be developed. PACS 78.20.Fm; 42.70.Gi; 42.70.Ln     

Solvent effects on valence tautomerism: A comparison between the interconversion in solution and solid state

A detailed comparative study of the valence tautomeric interconversion of complexes 1–3 in three different environments is reported. The three environments are solid state (both crystalline and amorphous materials), solution and embedded into a polymeric matrix. The VT behavior of the three complexes strongly differs from one to the other, though no systematization can be established. In solution, different solvatational parameters seem to affect the equilibrium. However, such solvate effect cannot be translated either into the solid state or polymeric matrix, where the equilibrium is controlled by the vibrational relaxation of the network.     

Effect of mechanochemical modification on the catalytic properties of the V2O5−TiO2 system

The mechanochemical modification of a V−Ti−O composition in ethanol and water was carried out in a planetary mill. X-ray phase analysis was used to show that the X-ray diffraction patterns of the modified samples result from overlapping of the patterns of the individual oxides, while the modification conditions affect the relative intensity of the reflections. The micro-Raman spectra indicated that homogeneity of this composition is achieved after only 30 min treatment in water and 20 min treatment in ethanol. X-ray photoelectron spectroscopy showed that the medium and duration of the treatment do not affect the valence state of the elements but do significantly alter the ratio of the elements in the surface layer. Mechanochemical treatment of mixtures of vanadium and titanium oxides permits enhancement of the activity and selectivity of the V−Ti−O compositions in the oxidation of n-pentane and o-xylene. Translated from Teoreticheskaya i éksperimental'naya Khimia, Vol. 36, No. 2, pp. 105–110, March–April, 2000.     

An algorithm for finding extremal polytope norms of matrix families

In this paper the problem of the computation of the joint spectral radius of a finite set of matrices is considered. We present an algorithm which, under some suitable assumptions, is able to check if a certain product in the multiplicative semigroup is spectrum maximizing. The algorithm proceeds by attempting to construct a suitable extremal norm for the family, namely a complex polytope norm. As examples for testing our technique, we first consider the set of two 2-dimensional matrices recently analyzed by Blondel, Nesterov and Theys to disprove the finiteness conjecture, and then a set of 3-dimensional matrices arising in the zero-stability analysis of the 4-step BDF formula for ordinary differential equations.