Effect of fibers and whole grain content on quality attributes

Incorporation of fiber in cereals may lead to quality issues, thus decreasing consumer acceptance. This is partially due to deterioration of the microstructure, one of the primary quality attributes of cereals. The objective of this study was to better understand the mechanisms by which dietary fibers affect the quality of cereal products during extrusioncooking. The study quantified the effect of amount and type of fiber and whole grain on (i) texture, (ii) structure, and (iii) rehydration properties of extruded cereals. New innovative methods were applied and combined with traditional techniques to characterize both the structure and the rehydration properties. Extruded cereals were produced using a starch-based recipe (whole and wheat flours) and two sources of fibers (oat bran concentrate and wheat bran). The oat and wheat bran levels used in this study were 0, 10, and 20%. The different mixtures were extruded in a pilot twinscrew extruder BC21 (Clextral) and then sugar coated after drying. Mechanical properties of extruded cereals were investigated by compression test. The cellular structure was observed by X-ray tomography. The quality of coating (thickness, homogeneity) was analyzed by optical coherence tomography. The rehydration properties of such cereals in milk were evaluated by magnetic resonance imaging and optical coherence tomography. This work revealed that structure assessment of extruded cereals may lead to a better understanding of the effect of fiber addition on texture and rehydration properties. The application of innovative methods, such as optical coherence tomography and magnetic resonance imaging, was found to be useful to quantify the structural properties.

Correlation Between Processing Conditions, Microstructure and Mechanical Behavior in Regenerated Silkworm Silk Fibers

Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk.

Relationship between fibre orientation and tensile strength of natural collagen membranes for heart valve leaflets

Heart valve prostheses are used to replace native heart valves which that are damaged because of congenital diseases or due to ageing. Biological prostheses made of bovine pericardium are similar to native valves and do not require any anticoagulation treatment, but are less durable than mechanical prostheses and usually fail by tearing. Researches are oriented in improving the resistance and durability of biological heart valve prostheses in order to increase their life expectancy. To understand the mechanical behaviour of bovine pericardium and relate it to its microstructure (mainly collagen fibres concentration and orientation) uniaxial tensile tests have been performed on a model material made of collagen fibres. Small Angle Light Scattering (SALS) has been also used to characterize the microstructure without damaging the material. Results with the model material allowed us to obtain the orientation of the fibres, relating the microstructure to mechanical performance

Bandlimited Airy Pulses for Invariant Propagation in Single-Mode Fibers

By spectral analysis, and using joint time-frequency representations, we present the theoretical basis to design invariant bandlimited Airy pulses with an arbitrary degree of robustness and an arbitrary range of single-mode fiber chromatic dispersion. The numerically simulated examples confirm the theoretically predicted pulse partial invariance in the propagation of the pulse in the fiber.

Optical programmable processing element using optical fibers

The purpose of this paper is to present a new type of Optically Processing Element (OPE) based of the use of optical fibers as optical signal transmission medium.

Plaster reinforcement with fibers obtained from the recycle of construction and demolition waste

The main objective of this research is to study the feasibility of recycling fibres from construction and demolition waste (C&DW) as an alternative material to chopped glass fibres which are used today as reinforcing elements in the prefabricated plaster. To do this, sets of samples are made with rockwool and different percentages of combinations between water / plaster. These series are repeated by changing the additive E glass fibre length of 25mm to make a comparative analysis with respect to the series infused with rockwool.

Plaster reinforcement with fibers by mineral wool obtained from the recycle of construction and demolition waste

The use of mineral wool is becoming more widespread due to increased acoustic and thermal demands of Spanish Technical Building Code. This increase affects both in rehabilitation and new construction projects. Therefore, waste generation of this type of insulating material is having more importance. The main objective of this research is to study the possibility of recycling fiber obtained from mineral wool of the C&DW as an alternative material to chopped glass fibers that are currently used as reinforcing elements in the prefabricated plaster. To achieve this objective, series are made of plaster E-35 additived with rock wool residue and glass wool residue at different rates of addition. These series are repeated by changing the additive by E fiberglass (length of 25mm) to make a comparative analysis with respect to the series additived with mineral wool waste. All the series are subjected to the test to determine Shore C surface hardness and mechanical testing to determine the compressive and flexural strength. From the results it can be concluded that: with rock wool residue, increases Shore C hardness up to 15% with respect to the glass fiber and 9% with respect to the glass wool, with a percentage of addition 2%. With rock wool residue, weight is decreased by 5% with respect to the glass fiber and 4% with respect to the glass wool waste, with an addition percentage of 4%. For an addition rate of 4%, results in the flexural strength test with fiberglass are 85% higher than those obtained with glass wool residue. However, for a percentage of 1% addition, the results obtained with glass wool residue are 35% higher than those obtained with fiberglass. For an addition rate of 3% results in the compressive strength test with fiberglass are 54% lower than those obtained with rock wool waste and 70% lower than those obtained with glass wool waste. Comparing the two mineral wools, it can be concluded that up to 3% of the addition, the glass wool series results obtained are 10% higher than those additived with rock wool. However, higher percentages of addition show that the results obtained with rock wool are 35% higher than those obtained with glass wool. The general conclusion is that the series additived with mineral wool from C&DW show better results in tests than the ones used nowadays as plaster reinforcement.

Characterization of a Material Based on Short Natural Fique Fibers

El fique es una fibra natural biodegradable. En este artículo se estudia la absorción acústica y la conductividad térmica del fique.

Polarization properties of polymer-based photonic crystal fibers

Selectively filled photonic crystal fibers with polydimethylsiloxane (PDMS), a silicon-type material, have been studied. Is has been demonstrated that polarization properties of these hybrid devices and the properties of the guided light in relation with the temperature changes, finding that the state of polarization (SOP) change with the increasing temperature but remains constant for a wide spectrum of wavelengths for a determinate temperature.

Polyolefin fiber-reinforced concrete enhanced with steel-hooked fibers in low proportions

Over the past few years, polyolefin fiber reinforced self-compacting concrete has shown high performance in both fresh and hardened state. Its fracture behavior for small deformations could be enhanced with a small amount of steel-hooked fibers, obtaining a hybrid fiber-reinforced concrete well suited for structural use. Four types of conventional fiber-reinforced concrete with steel and polyolefin fibers were produced on the basis of the same self-compacting concrete also manufactured as reference. These concrete mixtures were manufactured separately with the same fiber contents being subsequently used for two more hybrid mixtures. Fracture properties, in addition to fresh and mechanical properties, were assessed. The research showed both synergies (with the two types of fibers working together in the fracture processes) and an improvement of the orientation and distribution of the fibers on the fracture surface

Nonlinear effects in optical fibers-v1

Nonlinear effects in optical fibers

Thermally tunable polarization by nanoparticle plasmonic resonance in photonic crystal fibers

A photonic crystal fiber selectively filled with silver nanoparticles dispersed in polydimethylsiloxane has been numerically studied via finite elements analysis. These nanoparticles possess a localized surface plasmon resonance in the visible region which depends on the refractive index of the surrounding medium. The refractive index of polydimethylsiloxane can be thermally tuned leading to the design of polarization tunable filters. Filters found with this setup show anisotropic attenuation of the x-polarization fundamental mode around ?x = 1200dB/cm remarkably higher than the y-polarization mode. Moreover, high fiber birefringence and birefringence reversal is observed in the spectral region of the plasmon.

Selectively filled photonic liquid crystal fibers = Fibras de cristal fotónico selectivamente llenas con cristal líquido

El presente trabajo de Tesis se ha centrado en el diseño, fabricación y caracterización de dispositivos basados en fibras de cristal fotónico infiltrado selectivamente con cristales líquidos, polímeros y una mezcla de ambos. Todos los dispositivos son sintonizables, y su área de aplicación se centra en comunicaciones ópticas y sensores. La manipulación y fusionado de fibras fotónicas, el llenado selectivo de determinadas cavidades y la alineación recíproca de fibras mantenedoras de polarización son tareas muy específicas y delicadas para las que se requieren protocolos muy estrictos. Previo a la fabricación de dispositivos ha sido necesaria por tanto una tarea de sistematización y creación de protocolos de fabricación. Una vez establecidos se ha procedido a la fabricación y caracterización de dispositivos. Los dispositivos fabricados se enumeran a continuación para posteriormente detallar una a una las singularidades de cada uno. • Interferómetros intermodales hechos a partir de una porción de fibra fotónica soldada entre dos fibras estándar, bien monomodo o PANDA (mantenedora de polarización). Estos interferómetros han sido sumergidos o bien llenados selectivamente con cristales líquidos para así sintonizar la señal interferométrica guiada a través de la fibra. • Infiltración de fibras fotónicas con cristales líquidos colestéricos con especial énfasis en la fase azul (blue phase) de estos materiales. Las moléculas de cristal líquido se autoalinean en volumen por lo que la infiltración de fibras fotónicas con estos cristales líquidos es muy interesante, pues es conocida la dificultad de alinear apropiadamente cristales líquidos dentro de cavidades micrométricas de las fibras fotónicas. • Grabación de redes holográficas de forma selectiva en las cavidades de una fibra fotónica. Estas redes holográficas, llamadas POLICRYPS (POlymer-LIquid CRYstal-Polymer Slices), son redes fabricadas a base de franjas de polímero y cristal líquido alineado perpendicularmente a dichas franjas. Las franjas son a su vez perpendiculares al eje de la fibra como lo puede ser una red de Bragg convencional. El cristal líquido, al estar alineado perpendicularmente a dichos franjas y paralelo al eje de la fibra, se puede conmutar aplicando un campo eléctrico externo, modificando así el índice efectivo de la red. Se puede fabricar por lo tanto una red de Bragg sintonizable en fibra, muy útil en comunicaciones ópticas. • Llenado selectivo de fibras fotónicas con polidimetilsiloxano (PDMS), un polímero de tipo silicona. Si se realiza un llenado selectivo asimétrico se puede inducir birrefringencia en la fibra. El índice de refracción del PDMS tiene una fuerte dependencia térmica, por lo que se puede sintonizar la birrefringencia de la fibra. • Estudio teórico de llenado selectivo de fibras fotónicas con PDMS dopado con nanopartículas de plata de 5, 40 y 80 nm. Estas nanopartículas poseen un pico de absorción en torno a los 450 nm debido a resonancias superficiales localizadas de plasmones (LSPR). La resonancia del plasmon tiene una fuerte dependencia con el índice de refracción del material colindante, y al ser éste PDMS, la variación de índice de refracción se ve amplificada, obteniendo una absorción sintonizable. Se ha propuesto la fabricación de polarizadores sintonizables usando esta técnica. Como ya se ha dicho, previamente a la fabricación ha sido necesaria la protocolización de diversos procedimientos de fabricación de alta complejidad, así como protocolizar el proceso de toma de medidas para optimizar los resultados. Los procedimientos que han requerido la formulación de protocolos específicos han sido los siguientes: • Llenado selectivo de cavidades en una fibra fotónica. Dichas fibras tienen generalmente un diámetro externo de 125 μm, y sus cavidades son de entre 5 y 10 μm de diámetro. Se han desarrollado tres técnicas diferentes para el llenado/bloqueado selectivo, pudiéndose combinar varios protocolos para la optimización del proceso. Las técnicas son las siguientes: o Llenado y bloqueado con un prepolímero. Dicho prepolímero, también llamado adhesivo óptico, está inicialmente en estado líquido y posee una cierta viscosidad. Las cavidades de la fibra fotónica que se desea llenar o bloquear poseen un diámetro diferente al resto, por lo que en el proceso de llenado aparecen dos frentes de llenado dependientes de su diámetro. A mayor diámetro, mayor velocidad de llenado. Polimerizando cuando existe dicha diferencia en los frentes se puede cortar por medio, obteniendo así una fibra parcialmente bloqueada. o Colapsamiento de las cavidades de menor diámetro mediante aplicación de calor. El calor producido por un arco voltaico de una soldadora de fibra estándar fusiona el material exterior de la fibra produciendo el colapsamiento de las cavidades de menor diámetro. En esta técnica también es necesaria una diferencia de diámetros en las cavidades de la fibra. o Bloqueo una a una de las cavidades de la fibra fotónica con adhesivo óptico. Este procedimiento es muy laborioso y requiere mucha precisión. Con este sistema se pueden bloquear las cavidades deseadas de una fibra sin importar su diámetro. • Alineación de una fuente de luz linealmente polarizada con una fibra mantenedora de polarización ya sea PANDA o fotónica. Así mismo también se han alineado entre sí fibras mantenedoras de polarización, para que sus ejes rápidos se fusionen paralelos y así el estado de polarización de la luz guiada se mantenga. • Sistematización de toma de medidas para caracterizar los interferómetros modales. Éstos son altamente sensibles a diversas variables por lo que el proceso de medida es complejo. Se deben aislar variables de forma estrictamente controlada. Aunque todos los dispositivos tienen en común el llenado selectivo de cavidades en una fibra fotónica cada dispositivo tiene sus peculiaridades, que van a ser explicadas a continuación. ABSTRACT The present Thesis has been centered in the design, fabrication and characterization of devices based on photonic crystal fibers selectively filled with liquid crystals, polymers and a mixture of both. All devices are tunable and their work field is optical communications and sensing The handling and splicing of photonic crystal fibers, the selective filling of their holes and the aligning of polarization maintaining fibers are very specific and delicate tasks for which very strict protocols are required. Before the fabrication of devices has therefore been necessary task systematization and creation of manufacturing protocols. Once established we have proceeded to the fabrication and characterization of devices. The fabricated devices are listed below and their peculiarities are detailed one by one: • Intermodal interferometers made with a portion of photonic crystal fiber spliced between two optical communication fiber pigtails, either single mode or PANDA (polarization-maintaining) fiber. These interferometers have been submerged or selectively filled with liquid crystals to tune the interferometric guided signal. • Infiltration of photonic fibers with cholesteric liquid crystals with special emphasis on their blue phase (blue phase). The liquid crystal molecules are self-aligning in volume so the infiltration of photonic fibers with these liquid crystals is very interesting. It is notoriously difficult to properly align liquid crystals within micron cavities such as photonic fibers. • Selectively recording of holographic gratings in the holes of photonic crystal fibers. These holographic gratings, called POLICRYPS (POlymer-LIquid CRYstal-Polymes Slices), are based on walls made of polymer and liquid crystal aligned perpendicular to them. These walls are perpendicular to the axis of the fiber as it can be a conventional Bragg grating. The liquid crystal is aligned perpendicular to the walls and parallel to the fiber axis, and can be switched by applying an external electric field and thus change the effective index of the grating. It is thus possible to manufacture a tunable Bragg grating fiber, useful in optical communications. •Asymmetrically selective filling of photonic crystal fibers with a silicone polymer like called polydimethylsiloxane (PDMS) to induce birefringence in the fiber. The refractive index of PDMS has temperature dependence, so that the birefringence of the fiber can be tuned. • Theoretical study of photonic crystal fibers selectively filled with PDMS doped with silver nanoparticles of 5, 40 and 80 nm. These nanoparticles have an absorption peak around 450 nm due to localized surface plasmon resonances (LSPR). Plasmon resonance has a strong dependence on the refractive index of the adjacent material, and as this is PDMS, the refractive index variation is amplified, obtaining a tunable absorption. Fabrication of tunable polarizers using this technique has been proposed. Before starting the fabrication, it has been necessary to optimize several very delicate procedures and different protocols have been designed. The most delicate procedures are as follows: • Selective filling of holes in a photonic crystal fiber. These fibers generally have an outer diameter of 125 μm, and their holes have a diameter around between 5 and 10 μm. It has been developed three different techniques for filling / selective blocking, and they can be combined for process optimization. The techniques are: o Filling and blocked with a prepolymer. This prepolymer also called optical adhesive is initially in liquid state and has a certain viscosity. The holes of the photonic crystal fiber that are desired to be filled or blocked should have a different diameter, so that in the filling process appear two different fronts depending on the hole diameter. The holes with larger diameter are filled faster. Then the adhesive is polymerized when there is such a difference on the front. A partially blocked fiber is obtained cutting between fronts. o Collapsing of holes of smaller diameter by application of heat. The heat produced by an arc of a standard fusion splicer fuses the outer fiber material producing the collapsing of the cavities of smaller diameter. In this technique also you need a difference of diameters in the fiber holes. o Blocking one by one the holes of photonic crystal fiber with optical adhesive. This procedure is very laborious and requires great precision. This system can block unwanted cavities regardless fiber diameter. • Aligning a linearly polarized light source with a polarization-maintaining fiber (either a PANDA fiber as a photonic crystal fiber). It is needed also an aligning between polarization-maintaining fibers, so that their fast axes parallel merge and that is state of polarization of light guided is maintained. • Systematization of taking measurements to characterize the modal interferometers. These are highly sensitive to several variables so the measurement process is very complicated. Variables must be fixed in a very controlled manner. Although all devices have the common characteristic of being selectively filled PCFs with some kind of material, each one has his own peculiarities, which are explained below.