Determining radii of meromorphy via orthogonal polynomials on the unit circle

Using a convergence theorem for Fourier–Padé approximants constructed from orthogonal polynomials on the unit circle, we prove an analogue of Hadamard's theorem for determining the radius of m-meromorphy of a function analytic on the unit disk and apply this to the location of poles of the reciprocal of Szeg functions.     

Incorporating zosteric acid into silicone coatings to achieve its slow release while reducing fresh water bacterial attachment

Biofouling has posed serious problems in maritime industry including increased fuel consumptions, economic loss from ship-hull maintenances, contamination of drinking water, and serious corrosion for mechanical instruments. Minimizing the attachment of bacteria and formation of biofilm could be advantageous in reducing the early stages of biofouling. Zosteric acid, a natural product present in eelgrass, was found to have ability for preventing the attachment of some bacteria and barnacles. In this study, the antifouling ability of zosteric acid during the early stages of fouling was evaluated using attachment studies of fresh water bacteria. Simultaneously, various methods were sought for incorporating zosteric acid into silicone to prolong the release of the compound. The main results from this study were that zosteric acid exhibited anti-bacterial attachment regardless of whether it dispersed in water or incorporated into a coating. In addition, the release rate of zosteric acid from the incorporated coatings, particularly those where zosteric acid was uniformly dispersed with aggregates size of 4 microm or less, was orders of magnitude slower than those of previous reports. The release results indicate that the service life of our coatings could be far extended even with a small amount of zosteric acid incorporated.     

Selective hydrogenation of butadiene-styrene copolymers using a Ziegler-Natta type catalyst 2. Thermal properties

Three types of butadiene-styrene copolymers, diblock, triblock and random, were partially hydrogenated in their elastomeric units in order to determine the influence of hydrogenation extent on their thermal properties. The hydrogenation reactions were carried out using a Ziegler-Natta type catalyst and the extent of hydrogenation was evaluated by FTIR spectroscopic technique. The percentage of crystallinity was determined by differential scanning calorimetry (DSC), considering the low density polyethylene (LDPE) as reference since the saturation of elastomeric units with low content of 1,2-vinyl bonds gives a structure which resembles to LDPE, thus semi-crystalline polymers were obtained. On the other hand, the glass transition temperature (T_g) for the hydrogenated and non-hydrogenated copolymers as well as their heat of fusion, were also determined by DSC. An equation to evaluate the T_g of partially hydrogenated random copolymers is proposed considering both the saturated and unsaturated fractions. The thermo-oxidative behaviour of certain hydrogenated and non-hydrogenated copolymers was evaluated by thermogravimetric analyses (TGA). The results obtained by TGA suggest that a minimum saturation level is necessary in order to improve the thermo-oxidative resistance of the polymers.     

Solvent effects on substitution reactions at complexes of the [Fe(CN)5L]3- type in binary aqueous mixtures

Summary The kinetics of replacement of 4,4-bipyridine, (4,4-bipy), and 4-cyanopyridine, (4-CNpy), by cyanide in [Fe(CN)₅-(4,4-bipy)]^3-. at 298 K have been studied in binary aqueous mixtures containing different amounts of t-butanol, methanol, glycerol, ethyleneglycol and sucrose. The plots of logarithms of the limiting rate constantsversus the mole fraction of water are linear over the entire composition range studied, showing the importance of solvation phenomena. A different straight line of log (k_L/s^–1)versus X_H2O is obtained for each mixture, indicating the influence of other solvent parameters on the reaction rate. A multiparameter regression of G _exp with A (acidity vector), B (basicity vector) and G^E is used for both reactions; plots of G _calc versus G _exp are linear with slopes of near unity.     

The Use of Heteronuclear Shift Correlation 19F-1H. The Chemical Shift Assignment of Fluorinated (mono,Bis, and tris Gem Difluoro) Cyclopropane Derivatives of Sesquiterpene Lactones.

The ¹⁹ F-¹ H heterocorrelated NMR experiments enable the final assignments of structures of six difluorocyclopropane (mono, bis and tris gem) sesquiterpene lactones of helenalin and parthenin series.     

Pyracene‐Linked Bis‐Imidazolylidene Complexes of Palladium and Some Catalytic Benefits Produced by Bimetallic Catalysts

Two new palladium complexes with a pyracene‐linked bis‐imidazolylidene (pyrabim) group have been obtained and fully characterized. The related monometallic analogues were obtained from the coordination of an acetanaphthene‐supported N‐heterocyclic carbene (NHC). The catalytic properties of all complexes were studied in the acylation of aryl halides with hydrocinnamaldehyde, and in the Suzuki–Miyaura coupling of aryl halides and aryl boronic acids. The results show that the presence of a second metal in the dimetallic complexes induces some benefits in the catalytic behavior of the complexes. This effect is more pronounced in the Suzuki–Miyaura coupling, for which the dimetallic complexes exhibit significantly higher activity than their monometallic counterparts.     

Synthesis of axinohydantoins

A short synthesis of the hydantoin-containing marine sponge metabolites axinohydantoins is described. A key feature of the synthesis is a putative biomimetic, intramolecular cyclization of alpha-functionalized imidazolone 5, which affords the tricyclic pyrroloazepinone framework comprising 6. In addition, the conversion of imidazolones to alpha,beta-unsaturated hydantoins is outlined and represents a new approach to these heterocyclic systems.     

A New Porphyrin for the Preparation of Functionalized Water-Soluble Gold Nanoparticles with Low Intrinsic Toxicity

A potential new photosensitizer based on a dissymmetric porphyrin derivative bearing a thiol group was synthesized. 5-[4-(11-Mercaptoundecyloxy)-phenyl-10,15,20-triphenylporphyrin (PR-SH) was used to functionalize gold nanoparticles in order to obtain a potential drug delivery system. Water-soluble multifunctional gold nanoparticles GNP-PR/PEG were prepared using the Brust–Schiffrin methodology, by immobilization of both a thiolated polyethylene glycol (PEG) and the porphyrin thiol compound (PR-SH). The nanoparticles were fully characterized by transmission electron microscopy and ¹H nuclear magnetic resonance spectroscopy, UV/Vis absorption spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the ability of GNP-PR/PEGs to induce singlet oxygen production was analyzed to demonstrate the activity of the photosensitizer. Cytotoxicity experiments showed the nanoparticles are nontoxic. Finally, cellular uptake experiments demonstrated that the functionalized gold nanoparticles are internalized. Therefore, this colloid can be considered to be a novel nanosystem that could potentially be suitable as an intracellular drug delivery system of photosensitizers for photodynamic therapy.