Reactions of thioquinanthrene with sodium alkanethiolates. The smiles rearrangement of diquinolinyl sulfides

Reactions of thioquinanthrene 1 with sodium alkanethiolates or S-alkylisothiouronium salts (in the presence of sodium hydroxide) at 70° in DMSO or DMF yielded 4,4′-dialkylthio-3,3′-diquinolinyl sulfides 3 , which were results of the S-S type of the Smiles rearrangement of primary reaction products - sodium 3-quinoline-thiolates 6. When the reactions were carried out at 20° the products were 3′,4-dialkylthio-3,4′-diquinolinyl sulfides 2.     

Anion radical formation in the reaction of chloranilic acid with n-methylpiperidine in acetonitrile

Reaction of chloranilic acid with N-methylpiperidine in acetonitrile has been studied. The product of the reaction is an unusually stable anion radical of quinone. The presence of radicals has been confirmed by EPR measurements. Stability constant, extinction coefficients and thermodynamic reaction parameters are reported. Mechanism of the reaction is proposed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phase structure and viscoelastic properties

The phase structure and dynamic mechanical properties of three polypropylene/polystyrene (PP/PS) systems of similar composition but various dispersion of the minor PS component have been examined. Two different PP/PS systems were prepared by polymerization of styrene (ST) molecularly dispersed in PP matrices (with the same initial structure) under the conditions leading to a linear or crosslinked PS component. The third PP/PS system has been prepared blending the homopolymers in the molten state. Studies of materials containingin situ polymerized PS revealed nanoscale phase separation of PS (atomic force microscopy) and pointed to the presence of physical entanglements between PS and non-crystalline phase of PP (DSC, dynamic mechanical analysis). The PS component in material prepared by melt mixing appeared to be completely phase-separated into micron-sized domains. Dynamic mechanical analysis revealed also the dependence of viscoelastic behavior of the PP/PS systems on dispersion of the PS inclusions and on the nature of the interface.     

Self-exciting vibrations and Hopf's bifurcation in non-linear stability analysis of rail vehicles in a curved track

The main objective of this article is to present the authors' view of and results on non-linear lateral stability of rail vehicles in a curved track. Three elements are exploited in order to secure this objective. Firstly, physical genesis of the problem is discussed, and its similarity to straight track analysis is emphasised. Results of the theories of self-exciting vibrations and bifurcation are the key elements here. Secondly, the method suitable for analysis in a curved track is presented. New necessary elements, extending the better established methods for straight track are clearly mentioned and described. The methodology of building original stability maps, being the basis for the analysis and valid for whole range of curve radii and straight track is represented. Thirdly, a sample of the analysis is shown in order to give the idea how the method can be utilised. The case study refers to the influence of wheel/rail profiles on the stability in circularly curved track and straight track as well. Two different pairs of wheel/rail profiles are used and the corresponding results compared. The main contributions of the article are: a discussion of the physical nature of phenomena related to the stability in a curved tracks, and the method (procedure) established for the reasons of the analysis. Another and more general contribution is our say in the hot polemics on the advisability of stability analysis in curves and the advantages of the non-linear critical speed over the linear one.     

A New Crystal Phase Molybdate Yb2Mo4O15: The Synthesis and Upconversion Properties

A new upconversion nanocrystal phase Yb₂Mo₄O₁₅:Er is developed by using a facile aqueous‐precipitation procedure combined with thermal annealing. Nanocrystals of Yb₂Mo₄O₁₅ are exclusively synthesized, with particle sizes ranging from 1 to 20 nm. The optical properties are characterized and a high upconversion quantum yield is determined to be ≈1.3% at room temperature, under excitation of ≈500 mW cm^?2 IR (975 nm). To the best of our knowledge, this is the first work concerning the synthesis of nanocrystalline Yb₂Mo₄O₁₅ and the characterization of its upconversion properties, which possesses the potential to be utilized in bio‐probing and thin‐film optoelectronic device applications.     

Electric-field-induced steering in soliton direction of propagation in chiral nematic liquid crystals

In this work we demonstrate the properties of spatial solitary waves in chiral nematic liquid crystals with an external electric field. Such self-trapped beams, called nematicons, were created due to the optical reorientation nonlinearity for a light power of a few tens of milliwatts. We show that the direction of propagation of such nematicons can be changed by applying an external electric field. Additionally, this effect can be modified by changing the input polarization of the light beam. The experimental results were obtained in four independent guiding layers created by a chiral nematic structure.     

Semigroups for Generalized Birth-and-Death Equations in lp Spaces

We prove the existence of C₀ semigroups related to some birth-and-death type infinite systems of ODEs with possibly unbounded coefficients, in the scale of spaces l^p, For some particular cases we also provide a characterization of the spectra of their generators. For the proof of the generation theorem in the case p > 1 we extend the Chernoff perturbation result ([9]) on relatively bounded perturbations of generators. The results presented here have been used in [5] and they play important role for analysing chaoticity of dynamical systems considered there. As a by-product of our approach we obtain a result related to the classical Shubin theorem [20]. We show that this theorem, saying that for a class of bounded infinite matrices the spectrum of the corresponding maximal operator in l^p is independent on cannot be extended to unbounded matrices.     

Oligomeric Branched Polyethers with Multiple Hydroxyl Groups by Cationic Ring-Opening Polymerization for Inorganic Surface Modification

Summary: Cationic ring-opening polymerization of cyclic ethers (also esters and acetals) substituted with hydroxyl groups leads to branched multihydroxyl polymers. When 4-membered hydroxysubstituted oxetanes or 5-membered hydroxysubstuituted oxolanes (or lactone and 1,3-dioxolane) are used as monomers the polymerization products have limited molecular weights (about 1000). Polymerization of these monomers leading in situ to oligomeric products was used for inorganic surface modification. Successful polymerizations of oxetane as well as considered as difficult to polymerize 5-membered hydroxysubstituted cyclic monomers initiated from montmorillonite clay and silica nanoparticles surfaces were performed.     

X-ray structure and NMR assignment of 4,4′-[3-oxa-1,5-pentanedi(ylthio)]-3,3′-diquinolinyl sulfide

The title compound (C₂₂H₁₈N₂OS₃) is monoclinic, with a=20.7446(5), b=8.332(1), c=24.393(7)°, β=112.12(1)° and space group P2₁/n. There are two independent molecules in the unit cell. Two quinoline moieties are nearly perpendicular to each other (76.9(1)°) and (72.0(2)°). Both S-methylene fragments are trans-orientated with respect to the C(3)−S(1)−C(13) plane. Two pairs of sulfur atoms in ortho-positions are in very close contact with sulfide preserving a skew conformation. The central 12-membered ring adopts an unusual conformation. Part XLIII in the series of Azinyl Sulfides. Part XLII: Maślankiewicz, M.J.; Maślankiewicz, A.J. Heterocycl. Chem. 1996,33, 1989.