A palmeira Livistona chinensis, nativa do sul do Japão, é muito utilizada como planta ornamental em paisagismos em todo o território brasileiro, e além de adaptar-se bem a vários tipos de solos é de fácil reprodução. Essa palmeira produz uma bainha fibrosa na base de seu pecíolo, que é de fácil extração, plana, flexível e porosa, com características ainda pouco conhecidas e exploradas, é um material de fonte renovável que instiga a criatividade para seu uso tanto de forma artesanal quanto industrial. Neste contexto a caracterização da bainha fibrosa da palmeira Livistona chinensis se torna relevante, pois pode representar um leque de oportunidades para o desenvolvimento de novos produtos para o mercado. A caracterização da bainha fibrosa foi realizada com auxílio de microscópio eletrônico de varredura, espectrometria de energia dispersiva de raios-X, microtomografia, análise termogravimétrica, difração de raios-X, composição química e umidade, espectroscopia no infravermelho por transformada de Fourier Também foram obtidos valores para densidade, gramatura e resistência à tração, incluindo índice de absorção acústica, condutividade térmica e Termografia infravermelha. Os ensaios e análises realizados indicaram que a fibra possui propriedades e características que são comparáveis a outras fibras lignocelulósicas e os resultados estão bem próximas aos encontrados para as fibras de coco, como a composição química, densidade e índice de cristalinidade. Um dos fatores relevantes é o índice de condutividade térmica da bainha fibrosa que se manteve próximo aos valores de materiais isolantes utilizados industrialmente como a lã de rocha e lã de vidro. Quanto aos ensaios de termografia de infravermelho, que apontam seu potencial para ser usado como isolante térmico. / The Livistona chinensis palm, native to southern Japan, is widely used as an ornamental plant in landscaping throughout the Brazilian territory, and besides adapting well to various types of soils, it is easy to reproduce. It produces a fibrous sheath at the base of its petiole, which is easy to extract, flat, flexible and porous, with characteristics still little known and exploited, is a renewable source material, and which instigates creativity for its use both artisanly and industrial. In this context the characterization of the fibrous sheath of palmeira Livistona chinensis becomes relevant, since it can represent a range of opportunities for the development of new products for the market. The characterization of the fibrous sheath was performed with scanning electron microscope, X-ray dispersive energy spectrometry, microtomography, thermogravimetric analysis, X-ray diffraction, chemical composition and humidity, Fourier transform infrared spectroscopy We also obtained values for density, weight and tensile strength, including acoustic absorption index, thermal conductivity and infrared thermography. The tests and analyzes indicated that the fiber has properties and characteristics that are comparable to other lignocellulosic fibers and the results are very close to those found for coconut fibers, such as chemical composition, density and crystallinity index. One of the relevant factors is the thermal conductivity index of the fibrous sheath that remained close to the values of insulating materials used industrially as rock wool and glass wool. Regarding the infrared thermography tests, which point out its potential to be used as thermal insulation.

A incorporação de nanocargas minerais e vegetais em matriz polimérica tem sido estudada, principalmente, com o objetivo de melhorar as propriedades de desempenho mecânico dos polímeros para aplicações industriais diversas. As argilas organofilizadas e as fibras vegetais estão entre os materiais que se destacam como cargas adicionadas ao polímero para a formação de nanocompósitos. Essa área de estudo tem despertado interesse também devido à obtenção de melhorias de propriedades físicas, químicas e mecânicas desses materiais quando comparadas às dos materiais compósitos tradicionais. O objetivo da pesquisa foi estudar algumas dessas propriedades em nanocompósitos produzidos com polipropileno, argila esmectítica brasileira e fibra do ouriço da castanha-do-brasil, com ênfase na melhora das propriedades mecânicas. Inicialmente, os materiais componentes foram caracterizados por diversos ensaios, tais como, difração de raios X, granulometria, infravermelho, microscopia eletrônica de varredura, temperatura de degradação térmica, além de ensaios específicos para medir características individuais da argila, como, viscosidade Fann, inchamento de Foster, limite de plasticidade, fluorescência de raios X, entre outros. Posteriormente, o polipropileno graftizado com anidrido maleico (PP-g-MA) foi incorporado ao PP puro (PP), em extrusora dupla rosca, nas proporções de 5%, 10% e 20% em peso e injetados os corpos de prova para os ensaios de tração e impacto. A partir dos resultados das propriedades mecânicas definiu-se o uso de 5% de PP-g-MA para preparação dos nanocompósitos definitivos. Finalmente, variou-se a quantidade de fibra na composição. Foram obtidos nanocompósitos de polipropileno (PP) e 5% PPg- MA reforçado com 5% em peso da argila organofilizada e fibra do ouriço da castanha-do-brasil em três proporções 5%, 10% e 15% em peso. As amostras foram caracterizadas por diferentes técnicas (DRX, MEV, FTIR, TG/DSC) e medidas as resistências mecânicas à tração, flexão e impacto. Todos os nanocompósitos apresentaram aumento na resistência mecânica quando comparados ao polímero sem argila e fibra. / The incorporation of vegetable and mineral nanofillers in polymer matrix has been studied mainly in order to improve the mechanical performance properties of polymers for various industrial applications. The organoclays and vegetable fibers are among the materials that stand out as fillers added to polymer for the formation of nanocomposites. This study has also attracted interest owing to achieve improvements in various properties when compared to other traditional composite materials. This study aims to investigate the effects of adding organophilic clay and brazilian nut fibers on the some physical, chemical and mechanical properties of polypropylene nanocomposite. Initially, The component materials were characterized by tests, such as X-ray diffraction, particle size, infrared, scanning electron microscopy, thermal degradation, as well as specific assays for measuring individual characteristics and properties of the clay, for example, viscosity Fann, Foster swelling, plasticity limit, X-ray fluorescence, among others. In the second step, the graftizado polypropylene with maleic anhydride (PP-g-MA) was incorporated into the pure PP, extruded in proportions of 5 weight%, 10 weight% and 20 weight% and injected the samples for tensile and impact tests. From the results of mechanical properties was defined using 5 weight% of PP-g-Ma for the incorporation into pure PP. Finally, samples were prepared containing only polymer, graftizado polymer/clay, graftizado polymer/clay/ fiber. The addition of clay was 5 weight% and the fiber was added to 5 weight%, 10 weight% and 15% by weight, respectively. The nanocomposites were prepared double-screw extruder and the samples injection molded, then, they were characterized by X-ray diffraction, scanning electron microscope (SEM), thermal analysis (TG/DSC), infrared spectroscopy and mechanical strength, flexural and impact test. All the nanocomposites increased mechanical properties as compared to polymer without clay and fibers.

Crack formation under tensile forces is a major weakness of concrete. Cracks make concrete vulnerable to the extreme environment due to the ingress of water and harmful compounds from the surrounding environment. Conventional methods of crack repairing are expensive and time consuming. It is estimated that in Europe, cost related to repair works is half of the annual construction budget and the US has average annual maintenance cost for existing bridges through the year is estimated to $5.2 billion. To overcome this problem, a self-healing concrete is produced based on the application of mineral producing alkaliphilic Bacillus Subtilis (strain 168) bacteria. Metabolic activities of these bacteria on calcium-based nutrients results in precipitation of calcium carbonate, which helps to repair concrete cracks. In bacteria based self-healing concrete, the bacteria are protected in the dense cementitious matrix by encapsulating them in “bacteria-carriers”. However, the presently available bacteria-carriers are not always suitable for concrete because of their complex manufacturing procedures or high cost. With the aim to develop a more suitable bacteria-carrier, in this study feasibility of cellulose fiber as a novel bacteria-carrier for self-healing mortar is investigated. Cellulose fibers compared to other bacteria-carriers can serve the dual purpose of arresting cracks and at the same time be a bacteria-carrier in large scale concrete construction. Two types of bacterial mortar by using cellulose fiber as a carrier was prepared. For one type, nutrients were added inside the mortar mix, while for the other, nutrients were added into the curing water. The two types of composites; control and cellulose fiber reinforced concrete (CeFRC) have also been investigated for autogenous healing of concrete. The crack healing efficiency of bacterial mortars was investigated using image analysis and ultrasonic pulse velocity (UPV) test and compared with unreinforced and control cellulose fiber mortars. Variation in compressive strength for all mixes compared to control mortar is also presented in this thesis. Research shows that self-sealing mortar using cellulose fiber as a bacteria-carrier result in maximum self-healing as compared to other mixes. This study also aims to evaluate the self-healing potential and water permeability of CeFRC. Compressive strength and flexural tests were also performed to evaluate the mechanical properties of the composites. Water permeability test was used to evaluate the coefficient of permeability and the self-healing performance was investigated by using UPV and a patented self-healing test. The results indicate that the water permeability coefficient decreased by 42% (+15% or -21%) whereas the healing ratio increased at a higher rate for the initial days of healing when cellulose fibers were added in the concrete. CeFRC also results in a 7.8% increase in flexural strength. / Graduate / 2020-09-13

The design, processing, and sequential testing of a novel cylindrical diffusing optical fiber tip for ultraviolet light delivery is described. This device has been shown to uniformly(+/- 15%) illuminate angioplasty balloons, 20 mm in length, that are used in an experimental photochemotherapeutic treatment of swine intimal hyperplasia. Our experiments show that uniform diffusing tips of < 400 micron diameter can be reliably constructed for this and other interstitial applications. Modeling results indicate that this design is scalable to smaller diameters. The diffusing tips are made by stripping the protective buffer and etching away the cladding over a length of 20 mm from the fiber tip and replacing it with a thin layer of optical epoxy mixed with A/203 powder. To improve the uniformity and ease of fabrication, we have evaluated a new device configuration where the tip is etched into a modified conical shape, and the distal end face is polished and then coated with an optically opaque epoxy. This is shown to uniformly scatter - 70% of the light launched into the fiber without forward transmission. To our knowledge, we are the first to use this device configuration, and we have achieved a uniform cylindrical pattern of laser energy with uniformity < ± 15% of the average value. A simple computational model suitable for the interpretation of laser energy irradiance along the bare core surface of multimode optical fiber tips is proposed and experimentally verified. The model used is based on geometrical optics and Gaussian approximation. Good agreement is obtained between the calculation and experiment. We have measured the optical properties of the tips through all the sequences of the fabrication. The performances of the diffusing tips for illuminating angioplasty balloons are then evaluated by Ultraviolet Light at 365 nm. A Ti:Sapphire Ring Laser System with a doubling crystal pumped by an argon ion laser is used to generate the wavelength in this study.

The overall thrust of this dissertation is to gain a fundamental understanding of the synergistic effects between surface topography and chemical functionality of poorly adhesive materials on enhancing the adhesion of mouse embryonic fibroblasts. Cellular response to surface topography and chemical functionality have been extensively studied on their own providing valuable information that helps in the design of new and improved biomaterials for tissue engineering applications. However, there is a lack of understanding of the synergistic effect of microscale and nanoscale topography with chemical functionality and the relative impact and contribution of each in modulating cellular behavior. By understanding the relationship between these cues, in particular using materials that are poorly adhesive, this study will provide new clues as to how cells adapt to their environment and also suggest new dimensions of biomaterial design for fine-tuning cellular control. A microstructure that combined non adhesive materials with defined surface topography and surface chemistry is presented, to assess and correlate the enhancement of mouse embryonic fibroblasts cell adhesion and spreading. Poly (N-isopropylacrylamide) or PNIPAAm electrospun fibers were overlaid on PNIPAAm thin films (100 nm) at various time points to investigate the role of topography on such coatings by keeping the chemical functionality the same. After doing this, several topographical patterns were developed, spanning from sparse to dense fiber mats, and cell adhesion strongly depended on the relative available areas for attachment on either the fibers or the supporting surface. To gain a better understanding of this finding, two surface chemistries, non-adhesive (self-assembled monolayer of polyethylene glycol (PEGSAM) alkanethiol on gold) or an adhesive coating (3-aminopropyltriethoxysilane (APTES) on glass) with well characterized adhesive properties were included in this study to assess the effect of topographical cues provided by the PNIPAAm electrospun fibers on cellular responses. With the deposition of the PNIPAAm fibers onto a PEGSAM surface, cell adhesion increased to almost 100%, and unlike the PNIPAAm surface, cell spreading was significantly enhanced. With the deposition of PNIPAAm fibers onto APTES, both cell adhesion and spreading were unaffected up to 60% fiber coverage. For both surfaces, PNIPAAm fiber densities above 60% coverage lead to adhesion and spreading independent of the underlying surface. These findings indicate the presence of a sparse topographical feature can stimulate cell adhesion on a typically non-adhesive material, and that a chemical dissimilarity between the topographic features and the background enhances this effect through greater cell-surface interaction. In addition to the aforementioned studies, cell response was also assessed on PNIPAAm thin films coatings with thicknesses ranging from 100 nm to 7 nm. Cell adhesion and spreading was enhanced as the thickness of the thin film decreased. This change was more noticeable below 30 nm, wherein 7 nm shows the highest cell adhesion and spreading enhancement. The results reported are preliminary results and further experiments will be conducted, to support the data. It is believed that cellular response was enhanced due to a change in surface topography at the nanoscale level.

The axilla is a major source of human body odour from which the characteristic musky, urinous or acidic odours emanate, and are predominantly due to bacterial metabolism of the protein-rich fluid secreted by the apocrine and sebaceous glands located in this area (Senol and Fireman, 1999). Clothing has been implicated in contributing to body odour intensity, possibly even increasing the intensity (Dravnieks, et al., 1968; Shelley, et al., 1953) by the transfer of secretions, skin debris and bacteria from the body to the fabric substrate. Despite much anecdotal evidence indicating that some fibres and fabrics are better at limiting odour intensity than others, there appears to be no published research confirming this. The purpose of this study therefore, was to determine whether fabrics varying in fibre content (cotton, wool, polyester) and fabric knit structure (interlock, single jersey, 1x1 rib) differed in the extent to which they retained and emanated axillary odour following wear, and whether the intensity of odour was linked to the number of bacteria transferred to the fabrics. A procedure for collecting odour on fabrics was developed as was a method for evaluating odour through use of a sensory panel. Total aerobic bacteria and aerobic coryneform bacteria extracted from the fabrics were counted to determine if an association between bacterial counts and fabrics existed. Sensory analysis recognises the unique capability of humans as odour-detecting instruments whereas, instrumental analysis has the potential to offer information on the concentration and identification of axillary compounds, which a human assessor cannot. To investigate a new method for detecting axillary odour on apparel fabrics, proton transfer reaction mass spectrometry (PTR-MS) was used to analyse volatiles emitted from fabrics differing in fibre type. After removal of garments from the human body, axillary odour can be detected on fabrics, with the intensity of odour being strongly influenced by the fibre type from which the fabrics had been made. Polyester fabrics emanated odour of high intensity, cotton that of mid-low odour intensity, and wool fabrics were low odour. Fabric structural properties such as thickness, mass per unit area and openness of knit structure also had an effect on odour intensity. However, as the principal factor influencing odour intensity was fibre, only fabrics characterised by a high intensity (i.e. polyester) were influenced by structural properties. Differences in odour intensity among fabrics were not necessarily related to bacterial numbers, and no �inherent antimicrobial� properties were evident for any of the fabrics. Bacterial populations persisted in all fabrics up to 28 days. A decline in numbers was apparent for high-odour polyester fabrics, while numbers in low-odour wool fabrics remained relatively stable. PTR-MS detected compounds likely to be short-chain carboxylic acids which increased in the headspace above the polyester fabrics after 7 days. However, this increase was not evident for either the wool or cotton fabrics. Therefore, bacterial numbers per se cannot be a predictor of the odour intensity emanating from fabrics at least on the basis of these fabrics and fibres. The intensity of axillary odour emanating from fabrics was found inversely related to fibre hygroscopicity. Keywords:fibre content, fabric structure, axillary odour, sensory analysis, bacteria, corynebacteria, instrumental analysis, PTR-MS

Thesis (Ph. D. in Chemistry)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

<p>This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated.</p><p>The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied.</p><p>In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated.</p><p>The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.</p>

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 140-144).

This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated. The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied. In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated. The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.