Search results for "DISPERSION"

Layered-Expanded Mesostructured Silicas: Generalized Synthesis and Functionalization

2018

Mesostructured layered silicas have been prepared through a surfactant-assisted procedure using neutral alkylamines as templates and starting from atrane complexes as hydrolytic inorganic precursors. By adjusting the synthetic parameters, this kinetically controlled reproducible one-pot method allows for obtaining both pure and functionalized (inorganic or organically) lamellar silica frameworks. These are easily deconstructed and built up again, which provides a simple way for expanding the interlamellar space. The materials present high dispersibility, which results in stable colloidal suspensions.

Engineering of Nanofibrous Amorphous and Crystalline Solid Dispersions for Oral Drug Delivery

2018

Poor aqueous solubility (<0.1 mg/mL) affects a significant number of drugs currently on the market or under development. Several formulation strategies including salt formation, particle size reduction, and solid dispersion approaches have been employed with varied success. In this review, we focus primarily on the emerging trends in the generation of amorphous and micro/nano-crystalline solid dispersions using electrospinning to improve the dissolution rate and in turn the bioavailability of poorly water-soluble drugs. Electrospinning is a simple but versatile process that utilizes electrostatic forces to generate polymeric fibers and has been used for over 100 years to generate synthet…

Identification of overglaze and underglaze cobalt decoration of ceramics from Valencia(Spain) by portable EDXRF spectrometry

2004

The purpose of this work is the application of non-destructive analysis to differentiate underglaze and overglaze techniques used in the decoration of glazed ceramics from Valencia (Spain). This study was carried out by portable EDXRF spectrometry using an X-ray tube and a thermoelectrically cooled semiconductor detector. From the EDXRF spectra we have identified the main elements present in the tin-opacified lead glaze and in the cobalt pigments. The identification of the underglaze and overglaze decoration is based on the different ratios between the fluorescence line of the main component of the glaze (Pb-La line) and the fluorescence lines of the main components of the pigment (Co-Ka, M…

Stability of Halloysite, Imogolite, and Boron Nitride Nanotubes in Solvent Media

2018

Inorganic nanotubes are attracting the interest of many scientists and researchers, due to their excellent application potential in different fields. Among them, halloysite and imogolite, two naturally-occurring aluminosilicate mineral clays, as well as boron nitride nanotubes have gained attention for their proper shapes and features. Above all, it is important to reach highly stable dispersion in water or organic media, in order to exploit the features of this kind of nanoparticles and to expand their applications. This review is focused on the structural and morphological features, performances, and ratios of inorganic nanotubes, considering the main strategies to prepare homogeneous col…

Parabolic pulse generation with active or passive dispersion decreasing optical fibers

2007

International audience; We experimentally demonstrate the possibility to generate parabolic pulses via a single dispersion decreasing optical fiber with normal dispersion. We numerically and experimentally investigate the influence of the dispersion profile, and we show that a hybrid configuration combining dispersion decrease and gain has several benefits on the parabolic generated pulses.

Tuning four-wave mixing through temperature in ethanol-filled photonic crystal fiber

2016

In this paper, continuous tuning of four-wave mixing bands in an ethanol-filled photonic crystal fiber is investigated. A wide tuning range of the parametric bands, from 745 nm to 920 nm (signal) and from 1260 nm to 1710 nm (idler), is achieved through the thermo-optic effect. This corresponds to a frequency tuning range higher than 2000 cm−1; such wide range can be particularly useful in applications that require broadband wavelength conversion, e.g., CARS microscopy. Numerical calculations are in good agreement with experimental measurements.

Sloped-wall thin-film photonic crystal waveguides

2005

The effect of the slope of the groove walls in the behavior of thin-film one-dimensional photonic crystal waveguides is extensively studied. In this respect, we point out its influence on the modal dispersion relations and then on the bandgap structure in general. Likewise, we also prove the lack of accuracy in the evaluation of the bandgap edges when material dispersion is ignored. The extreme importance of both facts, the wall slope and the material dispersion, in the analysis and design of realistic photonic crystal devices is emphasized. In particular, we exploit the wall slope as a new design parameter. By suitably choosing the value of the above parameter, sloped-wall photonic crystal…

Transmission anisotropy in triple-film opal photonic crystals

2006

Summary form only given: For photonic crystals (PhCs) to have successful impact on advancement of optical circuits and realisation of various functionalities, the incorporation of artificial defects into 3D PhCs is necessary. Opal films represent a convenient approach to the realisation of 3D PhCs. Taking into account the limited flexibility of the self-assembly, the first steps can be studies of planar defects in opals and hetero-opals. Characterisation of heteroPhCs should include the investigation of the dispersion of photonic bandgaps (PBG). While the dispersion of low-order PBGs in opal films is well known, the high order PBGs were hardly studied so far owing to high requirements to th…

Dispersion properties and spatial solitons in photonic crystal fibres

2005

Phase-matching measurements and Sellmeier equations over the complete transparency range of KTiOAsO_4, RbTiOAsO_4, and CsTiOAsO_4

2000

The sphere method is used for the direct measurement of sum- and difference-frequency generation phase matched in the principal planes of KTiOAsO4, RbTiOAsO4, and CsTiOAsO4, including the tuning curves of 1.064-µm-pumped OPO’s emitting between 3 and 5 µm. The nonlinear least-squares fitting of our experimental data leads to refined dispersion equations of the principal refractive indices; the resulting dual-oscillator form equations are valid over the complete transparency range of the three studied materials.