992 resultados para CELLULOSIC MATERIALS


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Amongst alternative energy sources, photovoltaics hold a considerable promise for it is a plentiful, easily accessible and renewable source of power. Yet, the overall cost of generating electricity using the most advanced silicon based solar cells remains high compared to both traditional and other renewable power generation approaches. Organic thin film photovoltaics are an emerging economically competitive photovoltaic technology that combines manufacturing adaptability, low-cost processing and a lightweight, flexible device end-product. At present, however, commercial use of organic photovoltaics is hindered by low conversion efficiency and poor overall stability of the devices. Encapsulation with high barrier performance materials and structures is one of the key ways to address these issues and improve device lifetime. This paper will briefly outline the current understanding of the major degradation mechanisms, their interrelation and the internal and external factors that initiate these processes. Then, the paper will provide an overview of currently available encapsulant materials, their utility in limiting chemical (water vapor and oxygen penetration) and mechanical degradation within individual layers and device as a whole, and potential drawbacks to their application in organic photovoltaic devices.

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Synthetic, natural, or composite, biomaterials occupy a key position in the management of disease and support continuous advancement of health care. Clinical utility of many permanent and biodegradable implants can be significantly improved via surface modification. Here, we discuss a novel polymer material developed from essential oil-based monoterpene alcohol using plasma polymerisation. The developed coatings are cytocompatible and limit adhesion and proliferation of a variety of pathogens. The coating can also be used to control degradation behaviour of resorbable materials, such as magnesium.

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This RIRDC publication reports the findings and recommendations of the RIRDC funded study, "Fabrication of Electronic Materials from Australian Essential Oils". This project was undertaken to facilitate an expansion of the Australian Essential Oils Industry through the development of novel applications in the Electronic and Bio-Materials Industries. The findings presented in this report will provide value broadly across the Australian Essential Oils Industry, and more particularly to the growers involved in the production of tea tree, lavender and other essential oils. Several essential oils, namely tea tree oil, sandalwood oil, eucalyptus oil, alpha-pinene, d-limonene, lavender oil (a separate PhD project) and five major components of tea tree oil were tested. With the exception of sandalwood oil, all oils investigated were successfully polymerised. Importantly, this project determined that it is possible to use an environmentally friendly, inexpensive process of polymerisation to fabricate materials from essential oils in a reproducible manner with properties required by the optics, electronics, protective coatings, and bio-material industries.

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The rising demand for medical implants for ageing populations and ongoing advancements in medical technology continue to drive the use of implantable devices. Higher implant usage has a consequent increased incidence of implant-related infections, and associated prolonged patient care, pain and loss of limb and other organ function. Numerous antibacterial surfaces have been designed that prevent the onset of biofilm formation, thus reducing or preventing implant-associated infections through inhibiting bacterial adhesion or by killing the organisms that successfully attach to the surface of the implant. Other surfaces have been designed to stimulate a local immune response, promoting the natural clearing of the invading pathogen. The desired antibacterial effects are typically achieved by modulating the surface chemistry and morphology of the implant material, by means of the controlled release of pharmacological agents and bioactive compounds from the surface of the material, or by a combination of both processes. An important issue for any type of antibacterial surface modification lies in balancing the non-fouling, bacteriostatic or bactericidal effects against local and systemic biocompatibility. In this chapter, we will first describe the concept of biocompatibility and its evolution, from devices that do not evoke a negative host response to those that actively drive host regeneration. We will then review the challenges associated with merging the need for an implant material to withstand a bacterial load with those associated with supporting function restoration and tissue healing.

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Adsorption has been considered as an efficient method for the treatment of dye effluents, but properdisposal of the spent adsorbents is still a challenge. This work attempts to provide a facile methodto reutilize the spent Mg/Al layered double hydroxide (Mg/Al-LDH) after the adsorption of orange II(OII). Herein, the spent hybrid was carbonized under the protection of nitrogen, and then washedwith acid to obtain porous carbon materials. Thermogravimetric analysis results suggested that thecarbonization could be well achieved above 600◦C, as mass loss of the spent hybrid gradually stabilized. Therefore, the carbonization process was carried out at 600, 800, and 1000 ◦C, respectively. Scanning electron microscope showed that the obtained carbon materials possessed a crooked flaky morphology. Nitrogen adsorption–desorption results showed that the carbon materials had large BET surface area and pore volume, e.g., 1426 m2/g and 1.67 cm3/g for the sample carbonized at 800 ◦C. Moreover, the pore structure and surface chemistry compositions were tunable, as they were sensitive to the temperature. Toluene adsorption results demonstrated that the carbon materials had high efficiency in toluene removal. This work provided a facile approach for synthesizing porous carbon materials using spent Mg/Al-LDH.

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Lemon myrtle, anise myrtle, and Tasmanian pepper leaf are commercial Australian native herbs with a high volatile or essential oil content. Packaging of the herbs in high- or low-density polyethylene (HDPE and LDPE) has proven to be ineffective in preventing a significant loss of volatile components on storage. This study investigates and compares the effectiveness of alternate high-barrier property packaging materials, namely, polyvinylidene chloride coated polyethylene terephthalate/casted polypropylene (PVDC coated PET/CPP) and polyethylene terephthalate/polyethylene terephthalate/aluminum foil/linear low-density polyethylene (PET/PET/Foil/LLDPE), in prevention of volatile compound loss from the three native herbs stored at ambient temperature for 6 months. Concentrations of major volatiles were monitored using gas chromatography?mass spectrometry (GC-MS) techniques. After 6 months of storage, the greatest loss of volatiles from lemon myrtle was observed in traditional LDPE packaging (87% loss) followed by storage in PVDC coated PET/CPP (58% loss) and PET/PET/Foil/LLDPE (loss of 23%). The volatile loss from anise myrtle and Tasmanian pepper leaf stored in PVDC coated PET/CPP and PET/PET/Foil/LLDPE packaging was <30%. This study clearly indicates the importance of selecting the correct packaging material to retain the quality of herbs with high volatile content.

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Flax and hemp have traditionally been used mainly for textiles, but recently interest has also been focused on non-textile applications. Microbial quality throughout the whole processing chain of bast fibres has not previously been studied. This study concentrates on the microbial quality and possible microbial risks in the production chain of hemp and flax fibres and fibrous thermal insulations. In order to be able to utilize hemp and flax fibres, the bast fibres must be separated from the rest of the plant. Non-cellulosic components can be removed with various pretreatment processes, which are associated with a certain risk of microbial contamination. In this study enzymatic retting and steam explosion (STEX) were examined as pretreatment processes. On the basis of the results obtained in this study, the microbial contents on stalks of both plants studied increased at the end of the growing season and during the winter. However, by processing and mechanical separation it is possible to produce fibres containing less moulds and bacteria than the whole stem. Enzymatic treatment encouraged the growth of moulds in fibres. Steam explosion reduced the amount of moulds in fibres. Dry thermal treatment used in this study did not markedly reduce the amount of microbes. In this project an emission measurement chamber was developed which was suitable for measurements of emissions from both mat type and loose fill type insulations, and capable of interdisciplinary sampling. In this study, the highest amounts of fungal emissions were in the range of 10^3 10^5 cfu/m^3 from the flax and hemp insulations at 90% RH of air. The fungal emissions from stone wool, glass wool and recycled paper insulations were below 10^2 cfu/m^3 even at 90% RH. Equally low values were obtained from bast fibrous materials in lower humidities (at 30% and 80% RH of air). After drying of moulded insulations at 30% RH, the amounts of emitted moulds were in all cases higher compared to the emissions at 90% RH before drying. The most common fungi in bast fibres were Penicillium and Rhizopus. The widest variety of different fungi was in the untreated hemp and linseed fibres and in the commercial loose-fill flax insulation. Penicillium, Rhizopus and Paecilomyces were the most tolerant to steam explosion. According to the literature, the most common fungi in building materials and indoor air are Penicillium, Aspergillus and Cladosporium, which were all found in some of the bast fibre materials in this study. As organic materials, hemp and flax fibres contain high levels of nutrients for microbial growth. The amount of microbes can be controlled and somewhat decreased by the processing methods presented.

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Modifications of surface materials and their effects on cleanability have important impacts in many fields of activity. In this study the primary aim was to develop radiochemical methods suitable for evaluating cleanability in material research for different environments. Another aim was to investigate the effects of surface modifications on cleanabilitity and surface properties of plastics, ceramics, concrete materials and also their coatings in conditions simulating their typical environments. Several new 51Cr and 14C labelled soils were developed for testing situations. The new radiochemical methods developed were suitable for examining different surface materials and different soil types, providing quantitative information about the amount of soil on surfaces. They also take into account soil soaked into surfaces. The supporting methods colorimetric determination and ATP bioluminescence provided semi-quantitative results. The results from the radiochemical and supporting methods partly correlated with each other. From a material research point of view numerous new materials were evaluated. These included both laboratory-made model materials and commercial products. Increasing the amount of plasticizer decreased the cleanability of poly(vinyl chloride) (PVC) materials. Microstructured surfaces of plastics improved the cleanability of PVC from particle soils, whereas for oil soil microstructuring reduced the cleanability. In the case of glazed ceramic materials, coatings affected the cleanability. The roughness of surfaces correlated with cleanability from particle soils and the cleanability from oil soil correlated with the contact angles. Organic particle soil was removed more efficiently from TiO2-coated ceramic surfaces after UV-radiation than without UV treatment, whereas no effect was observed on the cleanability of oil soil. Coatings improved the cleanability of concrete flooring materials intended for use in animal houses.

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The antioxidant activity of natural plant materials rich in phenolic compounds is being widely investigated for protection of food products sensitive to oxidative reactions. In this thesis plant materials rich in phenolic compounds were studied as possible antioxidants to prevent protein and lipid oxidation reactions in different food matrixes such as pork meat patties and corn oil-in water emulsions. Loss of anthocyanins was also measured during oxidation in corn oil-in-water emulsions. In addition, the impact of plant phenolics on amino acid level was studied using tryptophan as a model compound to elucidate their role in preventing the formation of tryptophan oxidation products. A high-performance liquid chromatography (HPLC) method with ultraviolet and fluorescence detection (UV-FL) was developed that enabled fast investigation of formation of tryptophan derived oxidation products. Byproducts of oilseed processes such as rapeseed (Brassica rapa L.), camelina (Camelina sativa) and soy meal (Glycine max L.) as well as Scots pine bark (Pinus sylvestris) and several reference compounds were shown to act as antioxidants toward both protein and lipid oxidation in cooked pork meat patties. In meat, the antioxidant activity of camelina, rapeseed and soy meal were more pronounced when used in combination with a commercial rosemary extract (Rosmarinus officinalis). Berry phenolics such as black currant (Ribes nigrum) anthocyanins and raspberry (Rubus idaeus) ellagitannins showed potent antioxidant activity in corn oil-in-water emulsions toward lipid oxidation with and without β-lactoglobulin. The antioxidant effect was more pronounced in the presence of β-lactoglobulin. The berry phenolics also inhibited the oxidation of tryptophan and cysteine side chains of β-lactoglobulin. The results show that the amino acid side chains were oxidized prior the propagation of lipid oxidation, thereby inhibiting fatty acid scission. In addition, the concentration and color of black currant anthocyanins decreased during the oxidation. Oxidation of tryptophan was investigated in two different oxidation models with hydrogen peroxide (H2O2) and hexanal/FeCl2. Oxidation of tryptophan in both models resulted in oxidation products such as 3a-hydroxypyrroloindole-2-carboxylic acid, dioxindolylalanine, 5-hydroxy-tryptophan, kynurenine, N-formylkynurenine and β-oxindolylalanine. However, formation of tryptamine was only observed in tryptophan oxidized in the presence of H2O2. Pine bark phenolics, black currant anthocyanins, camelina meal phenolics as well as cranberry proanthocyanidins (Vaccinium oxycoccus) provided the best antioxidant effect toward tryptophan and its oxidation products when oxidized with H2O2. The tryptophan modifications formed upon hexanal/FeCl2 treatment were efficiently inhibited by camelina meal followed by rapeseed and soy meal. In contrast, phenolics from raspberry, black currant, and rowanberry (Sorbus aucuparia) acted as weak prooxidants. This thesis contributes to elucidating the effects of natural phenolic compounds as potential antioxidants in order to control and prevent protein and lipid oxidation reactions. Understanding the relationship between phenolic compounds and proteins as well as lipids could lead to the development of new, effective, and multifunctional antioxidant strategies that could be used in food, cosmetic and pharmaceutical applications.

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Wood is an important biological resource which contributes to nutrient and hydrology cycles through ecosystems, and provides structural support at the plant level. Thousands of genes are involved in wood development, yet their effects on phenotype are not well understood. We have exploited the low genomic linkage disequilibrium (LD) and abundant phenotypic variation of forest trees to explore allelic diversity underlying wood traits in an association study. Candidate gene allelic diversity was modelled against quantitative variation to identify SNPs influencing wood properties, growth and disease resistance across three populations of Corymbia citriodora subsp. variegata, a forest tree of eastern Australia. Nine single nucleotide polymorphism (SNP) associations from six genes were identified in a discovery population (833 individuals). Associations were subsequently tested in two smaller populations (130160 individuals), validating our findings in three cases for actin 7 (ACT7) and COP1 interacting protein 7 (CIP7). The results imply a functional role for these genes in mediating wood chemical composition and growth, respectively. A flip in the effect of ACT7 on pulp yield between populations suggests gene by environment interactions are at play. Existing evidence of gene function lends strength to the observed associations, and in the case of CIP7 supports a role in cortical photosynthesis.

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Multicultural social policies were formulated in Australia during the 1970s in response to challenges that had arisen the wake of a large-scale immigration program. Given recent intensification and diversification of immigrant intakes, however, understandings of multiculturalism have been contested repeatedly while new social demands have been made of the policy. In this context, questions have been raised about the adequacy of multicultural ethical education in Australian schools. These concern not only the type of ethics taught, but also the emphasis placed on ethics per se. This study emerges out of this context to look at the utility of using purpose-written philosophical materials– specifically, immigration-themed materials written by advocates of philosophy for children – for development of ethical understanding in multicultural Australia.

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Silicon has demonstrated great potential as anode materials for next-generation high-energy density rechargeable lithium ion batteries. However, its poor mechanical integrity needs to be improved to achieve the required cycling stability. Nano-structured silicon has been used to prevent the mechanical failure caused by large volume expansion of silicon. Unfortunately, pristine silicon nanostructures still suffer from quick capacity decay due to several reasons, such as formation of solid electrolyte interphase, poor electrical contact and agglomeration of nanostructures. Recently, increasing attention has been paid to exploring the possibilities of hybridization with carbonaceous nanostructures to solve these problems. In this review, the recent advances in the design of carbon-silicon nanohybrid anodes and existing challenges for the development of high-performance lithium battery anodes are briefly discussed.