Search results for "Fiber"
showing 10 items of 2343 documents
Characterization of a new natural fiber from Arundo donax L. as potential reinforcement of polymer composites.
2013
Abstract The aim of this paper is to study the possibility of using of Arundo donax L. fibers as reinforcement in polymer composites. The fibers are extracted from the outer part of the stem of the plant, which widely grows in Mediterranean area and is diffused all around the world. To use these lignocellulosic fibers as reinforcement in polymer composites, it is necessary to investigate their microstructure, chemical composition and mechanical properties. Therefore, the morphology of A. donax L. fibers was investigated through electron microscopy, the thermal behavior through thermogravimetric analysis and the real density through a helium pycnometer. The chemical composition of the natura…
Effect of Supplementation with Wheat Bran Aqueous Extracts Obtained by Ultrasound-Assisted Technologies on the Sensory Properties and the Antioxidant…
2015
Phenolic compounds have antioxidant properties and activate endogenous detoxification defense systems able to scavenge the reactive species of oxygen. The external layers of wheat caryopsis, largely constituting by-products of the milling industry such as bran and various middlings, contain relevant amounts of phenolic compounds. The aim of the research has been to evaluate the effect of supplementation with wheat bran aqueous extracts, obtained by ultrasound-assisted technologies, on the sensory properties and antioxidant activity of dry pasta. The HPLC-DAD characterization of the extract evidenced the presence of ferulic and p-coumaric acids. The supplemented pasta showed significantly h…
Influence of different soluble dietary fibers on the bioaccessibility of the minor Fusarium mycotoxin beauvericin.
2011
Abstract Beauvericin (BEA) is a bioactive compound produced by the secondary metabolism of several Fusarium strains and is known to have various biological activities. This study investigated the bioaccessibility of the BEA tested in concentrations of 5 and 25 mg/L, in a model solution and in wheat crispy breads elaborated with different natural binding compounds as the soluble alimentary dietary fibers β-1,3 glucan, chitosan low molecular weight (L.M.W.), chitosan medium molecular weight (M.M.W.), fructooligosaccharides (FOS), galattomannan, inulin and pectin, added at concentrations of 1% and 5%. The bioaccessibility was determinated by employing a simulated gastrointestinal digestion tha…
Nutraceuticals in Lipid-Lowering Treatment
2014
Lipid-lowering drugs may cause adverse effects and, although lipid targets may be achieved, a substantial residual cardiovascular (CV) risk remains. Treatment with agents mimicking proteins present in the body, such as incretin-based therapies, provided promising results. However, in order to improve lipids and CV risk, lifestyle measures remain important. Some researchers focused on nutraceuticals that may beneficially affect metabolic parameters and minimize CV risk. Chitosan, a dietary fiber, can regulate lipids with benefit on anthropometric parameters. The beneficial properties of dietary supplements (such as green tea extract, prebiotics, plant sterols, and stanols) on plasma lipids,…
Addition of Secondary Amines to α,β-Unsaturated Carbonyl Compounds and Nitriles by Using Microstructured Reactors
2006
Several additions of amines to a,ß-unsaturated carbonyl compounds (Michael additions) were performed in a continuous-flow microstructured reactor rig and compared to the respective batch reaction. Dimethylamine/diethylamine/piperidine and acrylic acid ethyl ester/acrylonitrile were employed as two sets of reactants, giving six reactions. Some of these reactions are highly exothermal. Using the traditional batch procedure the olefin must be added quite slowly to the diluted amine to ensure temperature control and safe operation; especially this is necessary for the addition of dimethylamine (40 mass % aqueous solution) to acrylonitrile. Good yields (>85%) are achieved in this way; however…
Thermodynamic approach of supercontinuum generation
2009
International audience; This paper is aimed at providing an overview on recent theoretical and experimental works in which a thermodynamic description of the incoherent regime of supercontinuum generation has been formulated. On the basis of the wave turbulence theory, we show that this highly nonlinear and quasi-continuous-wave regime of supercontinuum generation is characterized by two different phenomena. (i) A process of optical wave thermalization ruled by the four-wave mixing effects: The spectral broadening inherent to supercontinuum generation is shown to result from the natural tendency of the optical field to reach its thermodynamic equilibrium state, i. e., the state of maximum n…
Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers
2015
Abstract We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and afte…
Ultraviolet holographic recording in photopolymers
2011
Norland Optical Adhesive (NOA) acrylate based photopolymers were studied as a medium for Bragg grating fabrication. NOA photopolymers have absorption maximum in near UV region, but they are transparent in visible light region. Photopolymers were irradiated by He-Cd laser 325 nm line interference patterns during holographic recording. In light irradiated regions photopolymerization takes place and volume grating can be recorded. Diffraction efficiency in dependence on sample thickness, recording beams polarization state and intensity was investigated on transmission mode. Enlargement of sample thickness allows to achieve better angular selectivity of diffracted beam, therefore thickness of p…
Spatial soliton formation in photonic crystal fibers
2003
We demonstrate the existence of spatial soliton solutions in photonic crystal fibers (PCF's). These guided localized nonlinear waves appear as a result of the balance between the linear and nonlinear diffraction properties of the inhomogeneous photonic crystal cladding. The spatial soliton is realized self-consistently as the fundamental mode of the effective fiber defined simultaneously by the PCF linear and the self-induced nonlinear refractive indices. It is also shown that the photonic crystal cladding is able to stabilize these solutions, which would be unstable otherwise if the medium was entirely homogeneous.
Experimental observation of temporal dispersion gratings in fiber optics
2017
We experimentally demonstrate a temporal analog to the diffraction optical grating in the Fraunhofer formalism. Using amplitude and phase temporal periodic modulations, we show that the accumulation of dispersion in fiber optics induces the development of temporally well-separated sidebands similar to the spatial orders of diffraction that are commonly observed in an optical grating operating in the far field.