Synthesis and characterization of PMMA-based superhydrophobic surfaces

Recently, superhydrophobic surfaces are gaining much interest because they may be employed in a series of applications, spanning from the realization of self-cleaning surfaces to microfluidics to special water-impermeable tissues allowing perspiration. It is well-known that superhydrophobicity strictly depends on the combination of superficial micro- and nano-structures. Then, key factors in the process of surface synthesis are the parameters which will define the surface conformation. In this work, we deal with the fabrication of polymer-based superhydrophobic surfaces. We developed a new method to have a good control of the structure of the synthesised surface. A high stability of the superhydrophobic character during time was obtained. Moreover, the synthesis process is green and easily transferable to industry for large production.     

Photoluminescence in Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript>-doped silica-titania inverse opal structures

Er³⁺ photoluminescence (PL) and Yb³⁺ → Er³⁺ energy transfer (ET) phenomena in the near infrared (NIR) have been studied in three-dimensional (3-D) inverse opal (IO) structures synthesized by a colloidal/sol–gel route, starting with the deposition of polystyrene microsphere (235 nm and 460 nm diameter) direct opal templates by convective self-assembly, followed by infiltration of the interstices with Er³⁺/Yb³⁺-doped silica, titania and silica-titania sols and heat-removal of the polymeric template material. The crystalline quality of the IOs has been optimized through suitable substrate treatments, plus the control of temperature and humidity during deposition of the templates. The structural and optical properties of the 3-D opal and IO structures have been studied by field emission scanning electron microscopy and visible-NIR reflection spectroscopy, in order to assess the relationship between microstructure and the photonic properties obtained. Photonic bandgaps have been evidenced by the corresponding stop bands in the reflection spectra. The shape and the intensity of the Er^{3+ 4}I_13/2 → ⁴I_15/2 transition at ~1.5 μm were modified in most IOs relatively to similar matrix deposits without a photonic crystal structure, particularly in the case of pure silica and titania IOs, where the PL peak narrowed and intensified. It was not possible at this stage to detect Yb³⁺ → Er³⁺ ET phenomena in the IOs structures.     

Determination of urinary tryptophan and its metabolites along the nicotinic acid pathway by high performance liquid chromatography with ultraviolet detection

A fast and sensitive method is given for analysing urinary tryptophan and six of its metabolites on the nicotinic acid pathway. Kynurenine, tryptophan, 3-hydroxykynurenine, anthranilic acid, 3-hydroxyanthranilic acid, kynurenic acid and xanthurenic acid were isocratically eluted and completely resolved with a mobile phase of acetonitrile + sodium acetate buffer, pH 4.76 (4:96, v/v). The flow rate was 0.8 mL/min at the beginning and was then linearly increased to 1.2 after 6 min; after 14 min the flow was augmented from 1.2 to 2 mL/min. The effluent was monitored with a variable UV detector set at 254 nm for the first five peaks and at 280 and 325 nm for the penultimate peak and final peak. Analytical recoveries of the compounds after deproteinization varied between 64% and 98%. The reported method should enable one to examine easily, extensively, quantitatively and routinely urinary tryptophan and the most important metabolites of the nicotinic acid pathway.     

Er3+/Yb3+-activated silica-hafnia planar waveguides for photonics fabricated by rf-sputtering

95.8SiO₂–4.2HfO₂ planar waveguide activated by 0.2 mol% Er and 0.2 mol% Yb was fabricated by multi-target rf-sputtering technique. The optical parameters were measured by an m-line apparatus operating at 543.5, 632.8, 1319 and 1542 nm. The waveguide compositions were investigated by energy dispersive spectroscopy. The waveguide exhibits a single propagation mode at 1.3 and 1.5 μm with an attenuation coefficient of 0.2 dB/cm at 1.5 μm. The emission of ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ ion, with a 42 nm bandwidth was observed upon TE₀ mode excitation at 980 and 514.5 nm. Photoluminescence excitation spectroscopy was used to obtain information about the effective excitation efficiency of Er³⁺ ions by co-doping with Yb³⁺ ions. Channel waveguide in rib configuration were fabricated by wet etching process in the active film.     

Evaluation of a single collector, double focusing sector field inductively coupled plasma mass spectrometer for the determination of U and Pu concentrations and isotopic compositions at trace level

This work explores the performance of the “Axiom”, a double focusing sector field ICP-MS (ICP-SFMS) in the determination of actinide concentration and isotopic ratio at trace level. On the actinide mass range the performances observed are characterized by high sensitivity, around 2.8·10⁶ cps·μg⁻¹·l, and low background, below 0.3 cps. Therefore, the absolute instrumental detection limit is approximately 0.05 fg for Pu isotopes. Furthermore, the ²³⁵U/²³⁸U ratio for a 0.5 μg·l⁻¹ U500 isotopic standard could now be measured using the ICP-SFMS with a relative standard deviation less than 0.1%. Moreover, the accuracy of the measured ratio was demonstrated at low concentration with the target value remaining within experimental uncertainty limits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Whispering gallery mode profiles in a coated microsphere

The properties of whispering gallery modes (WGM) of a microsphere can be tailored by coating the resonator with a thin film. If the coating has a higher refractive index than the microsphere core, the resulting structure will have a configuration which has similarities both with a classical WGM resonator and with a planar waveguide. By choosing the film thickness and refractive index we can tailor the degree of confinement of the WGMs inside the sphere core, coating and surrounding medium, which will in turn influence the WGMs contact with its surroundings. We present a study of the effect of the coating on the WGM mode profiles in particular of a silicon coating on a silica sphere.     

Adjustment of Jacobs' formulation to the case of Mercury

Summary Magnetic investigations play an important role in studies on the constitution of planetary interiors. One of these techniques (the so-calledJacobs' formulation), appropriately modified, has been applied to the case of Mercury. According to the results found, the planet, supposed divided internally as the Earth (crust-mantle-core), would have a core/planet volume ratio of 28%, much greater than the Earth's core percentage (16%). This result is in agreement with previous works which used other independent methods.     

Application of DIC to Static and Dynamic Testing of Agglomerated Cork Material

In this work, experimental compression tests have been performed on parallelepiped specimens cut from an agglomerated cork slab. The tests have been performed both using a quasi-static testing machine and a polymeric Split Hopkinson Bar, in order to assess the sensitivity of the material to the strain rate. A standard and a high-speed digital camera have been used to collect frames of the samples during the tests. 2D DIC analyses have been conducted on the pictures of lateral faces of the specimens in order to evaluate the actual strain distributions, which showed a significant heterogeneity within each sample. Moreover, the DIC analyses on the dynamic tests have been used for evaluating the local accelerations and to compute the inertia stresses. The latter may affect the global response that can be measured by following the standard Hopkinson bar procedures, and are responsible for the fluctuations in the force histories observed in the tests at highest strain rates.     

Preparation and characterization of ZnO particles embedded in organic–inorganic planar waveguide by sol–gel route

Hybrid organic–inorganic waveguides based on ZnO-(3-glycidoxypropil)trimethoxisilane (GPTS) have been fabricated by sol–gel route. A transparent sol of ZnO was added to the GPTS host and the resulting sol was deposited on silica substrates by spin coating technique. Waveguides with different molar composition (100?x)GPTS?xZnO (x = 10, 20, 30) were investigated by different diagnostic techniques. Morphological measurements were carried out by means of an AFM apparatus, and a roughness of few nanometers was estimated for all the waveguides. Optical properties such as refractive index, thickness, number of propagating modes and attenuation coefficient were measured at 632.8, 543.5, 1319 and 1542 nm by the prism coupling technique as a function of the ZnO content. Photoluminescence measurements, upon excitation at 325 nm, showed a large luminescence band in the region between 350 and 600 nm with a main peak centered at about 380 nm, due to the presence of ZnO nanoparticles.