Laser and thermal processing for Ti:LiNbO3 waveguide fabrication

Ti diffusion into LiNbO₃ single crystal was studied as a result of Ruby laser irradiation of a metallic Ti thin film covering the crystal surface and subsequent thermal processing in a furnace. Different regimes of irradiation and heating were used. SIMS analysis was employed for investigation of the treatment. The combined method used proved to be able to form waveguides of 3–4 m thickness.     

A note on the global structure of supermoduli spaces

We recall some deformation theory of Susy-curves and study obstructions to projectedness of supermoduli spaces, both from a general standpoint and by means of the local coordinate charts most commonly used in the physical literature. We prove that these give rise to a projected atlas for genusg=2 only.Work partially supported by the National Project Geometria e Fisica, M.P.I.     

Simultaneous liquid chromatographic analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol in human plasma. Comparison of amperometric and coulometric detection

The comparison of two HPLC methods, one with electrochemical detection and the other with coulometric detection, for the simultaneous analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol (MHPG) in human plasma is presented. The careful pre-treatment of plasma samples is based on an innovative two-step procedure by means of solid-phase extraction (SPE) which uses one single hydrophilic-lipophilic balance cartridge. The extraction yield values found were higher than 85% for epinephrine, norepinephrine and MHPG, and higher than 70% for dopamine. The assays carried out on real plasma samples with the coulometric system gave good results in terms of sensitivity (limits of quantitation: 0.10-0.15 ng ml(-1) for catecholamines, 0.6 ng ml(-1) for MHPG) and selectivity, while interference was sometimes found when using the amperometric system. Precision was also satisfactory, with relative standard deviation values for intermediate precision always lower than 6%. The HPLC method with coulometric detection coupled to a novel SPE procedure is thus suitable for the simultaneous determination of catecholamines and MHPG in plasma of volunteers subjected to experimental stress.     

Infrared and Raman spectroscopic evidence of ground state charge densities at TCNQ sites in crystalline Cs2 (TCNQ)3

The reported Raman spectrum of the Rb TCNQ salt allows, for the first time, examination of all the vibrational features of the TCNQ ^? radical anion. The knowledge of the TCNQ fundamental frequencies as well as of those for neutral TCNQ makes it possible to interpret the infrared and Raman spectra of Cs₂ (TCNQ)₃ and to conclude that in this salt both neutral and negatively charged TCNQ units are present in the crystal. The result is a first fruitful application of vibrational spectroscopy to the study of complex TCNQ salts, opening the way to an extensive investigation of TCNQ semiconducting salts.     

Enolboronates: New practical reagents for regioselective aldol condensations.

Enolboronates, new enolates directly accessible from carbonyl compounds and giving aldol products regioselectively and in good yield with aliphatic and aromatic aldehydes, are described.     

HPLC-DAD determination of plasma levels of the antipsychotic risperidone and its main metabolite for toxicological purposes

A new, rapid analytical method, based on liquid chromatography with diode array detection, has been developed and applied to the determination of risperidone and its main active metabolite 9-hydroxyrisperidone in human plasma. The chromatographic separation was obtained on a C8 (150 x 4.6 mm, 5 microm) column, using a mobile phase composed of acetonitrile (27%) and a pH 3.0 phosphate buffer (73%). A sample clean-up procedure was carried out by using C8 cartridges and eluting the analytes with methanol. The extraction yield was highly satisfactory for both analytes, with average absolute recovery values of about 95%. The experimental conditions permitted the quantitative determination of risperidone and 9-hydroxyrisperidone with high precision (RSD < 3.6%) and satisfactory sensitivity (LOQ = 4 ng mL(-1)). The method was applied to plasma samples from a patient who had tried to poison himself with 150 mg of risperidone, and was undergoing polypharmacy.     

Reactivity of the non stoichiometric Ni3O4 phase supported at the Pd(100) surface: interaction with Au and other transition metal atoms

In this work we have studied, employing ab initio periodic calculations, the interaction between the non-stoichiometric Ni(3)O(4) monolayer (a rhombic distribution of vacancies hereafter referred to as RH-Ni(3)O(4)) supported on the Pd(100) surface and several transition metal atoms (Ni, Cu, Pd, Pt, Ag, Au). The interaction produces a regular array of metal centers uniformly distributed in size and shape. According to the size of the atom and the ionization potential, the nature of the interaction ranges from an essentially electrostatic one to a polar-covalent one. The chemical reactivity versus the CO molecule of the overlayer resulting from the saturation with Au atoms of the Ni vacancies has been investigated.     

Hybrid niosome complexation in the presence of oppositely charged polyions

We have investigated the formation of complexes between negatively charged niosomal vesicles (hybrid niosomes), built up by dicethylphosphate [DCP], Tween 20 and Cholesterol, and three linear differently charged cationic polyions, such as alpha-polylysine, epsilon-polylysine, and polyethylvinylpyridinium bromide [PEVP], with two different substitution degrees. Our aim is to investigate the interaction mechanism between anionic-nonionic vesicles (hybrid niosomes) and linear polycations, characterizing the resulting aggregates in view of possible applications of these composite colloidal particles as vectors for multidrug delivery. In order to explore the aggregation behavior of the complexes and to gain information on the stability of the single niosomal vesicles within the aggregates, we employed dynamic light scattering (DLS), laser Doppler electrophoretic measurements, and fluorescence measurement techniques. The overall phenomenology is well described in terms of the re-entrant condensation and charge inversion behavior, observed in different colloidal systems. The aggregate size and overall charge depend on the charge ratio between vesicles and polyions, and the aggregates reach their maximum size at the point of charge inversion (re-entrant condensation). While the overall phenomenology is similar for all three polycations investigated, the stability and the integrity of the hybrid niosomal vesicles forming the aggregates strongly depend on the chemical structure of the polycations. The role of the polycations in the aggregation process is discussed by identifying specific interactions with the niosomal membrane, pointing out their importance for possible applications as drug delivery vectors.     

The beneficial influence of ultrasound in the polymerization of epsilon-caprolactam to polyamide-6 (Nylon 6). Part I: primary experimental results

ε-caprolactam (CL) polymerization to polyamide-6 (Nylon 6) was studied at different contents of water in CL (0.01–2 wt%), with or without ε-amino-caproic acid (ACA) as an activator, applying to the mixture an initial treatment of Ultrasound (US) (17.5–20 kHz) at low temperatures (70–110 °C) and for short times (max 10 min). It was verified that polymerization at 260 °C produces a polymer having a much higher molecular weight (MW) when US is applied with respect to silent (SIL) conditions i.e. without the use of ultrasound. This constitutes a “pre-sonication effect”. The ratio (MW)_US/(MW)_SIL is inversely proportional to the initial content of water in CL. The action of US converts CL at very low temperatures (70–110 °C) and water content, in comparison with silent conditions where CL was unconverted.

Optimized conditions are studied with respect to nature and pressure of gas inside the reactor, temperature, time and frequency of US irradiation, energy consumption and nature of activator.