Electrolytic cells for plastic waste recycling

The current project assesses potential molten alloy anodes for Solid Oxide Fuel Cells (SOFC) running on solid waste. A detailed phase diagram study was performed to locate probable anode systems. The molten metal oxide system PbO-Sb2O3 was selected as a possible molten alloy anode for this application. A detailed vapour pressure study of this system was performed. Several cells were fabricated to experimentally assess the electrochemical properties of this system. The work reveals several unexpected limiting features such as the incompatibility between the platinum and the chosen alloy. A second cell was built, this time using rhenium wires instead, preventing such reaction. However, the rhenium wire sublimes under oxidizing conditions (air) and the sealing glass and the chosen alloy system react with each other under long term use. Considering all these issues, a third cell design was conceived, surpassing some obstacles and providing some initial information regarding the electrochemical behaviour. The current project shows that many parameters need to be taken into account to ensure materials compatibility. For the PbOSb2O3 system, the high volatility of Sb2O3 was a serious limitation that can only be addressed through the application of new contact wires or sealing materials and conditions. Nonetheless, the project highlights several other potential systems that can be considered, such as Pb11Ge3O17, Pb3GeO5, Pb5Ge3O11, Bi2CuO4, Bi2PdO4, Bi12GeO20.

Development of ultra-high-performance concrete (UHPC) using waste glass materials ─ towards innovative eco-friendly concrete

Le béton conventionnel (BC) a de nombreux problèmes tels que la corrosion de l’acier d'armature et les faibles résistances des constructions en béton. Par conséquent, la plupart des structures fabriquées avec du BC exigent une maintenance fréquent. Le béton fibré à ultra-hautes performances (BFUP) peut être conçu pour éliminer certaines des faiblesses caractéristiques du BC. Le BFUP est défini à travers le monde comme un béton ayant des propriétés mécaniques, de ductilité et de durabilité supérieures. Le BFUP classique comprend entre 800 kg/m³ et 1000 kg/m³ de ciment, de 25 à 35% massique (%m) de fumée de silice (FS), de 0 à 40%m de poudre de quartz (PQ) et 110-140%m de sable de quartz (SQ) (les pourcentages massiques sont basés sur la masse totale en ciment des mélanges). Le BFUP contient des fibres d'acier pour améliorer sa ductilité et sa résistance aux efforts de traction. Les quantités importantes de ciment utilisées pour produire un BFUP affectent non seulement les coûts de production et la consommation de ressources naturelles comme le calcaire, l'argile, le charbon et l'énergie électrique, mais affectent également négativement les dommages sur l'environnement en raison de la production substantielle de gaz à effet de serre dont le gas carbonique (CO[indice inférieur 2]). Par ailleurs, la distribution granulométrique du ciment présente des vides microscopiques qui peuvent être remplis avec des matières plus fines telles que la FS. Par contre, une grande quantité de FS est nécessaire pour combler ces vides uniquement avec de la FS (25 à 30%m du ciment) ce qui engendre des coûts élevés puisqu’il s’agit d’une ressource limitée. Aussi, la FS diminue de manière significative l’ouvrabilité des BFUP en raison de sa surface spécifique Blaine élevée. L’utilisation du PQ et du SQ est également coûteuse et consomme des ressources naturelles importantes. D’ailleurs, les PQ et SQ sont considérés comme des obstacles pour l’utilisation des BFUP à grande échelle dans le marché du béton, car ils ne parviennent pas à satisfaire les exigences environnementales. D’ailleurs, un rapport d'Environnement Canada stipule que le quartz provoque des dommages environnementaux immédiats et à long terme en raison de son effet biologique. Le BFUP est généralement vendu sur le marché comme un produit préemballé, ce qui limite les modifications de conception par l'utilisateur. Il est normalement transporté sur de longues distances, contrairement aux composantes des BC. Ceci contribue également à la génération de gaz à effet de serre et conduit à un coût plus élevé du produit final. Par conséquent, il existe le besoin de développer d’autres matériaux disponibles localement ayant des fonctions similaires pour remplacer partiellement ou totalement la fumée de silice, le sable de quartz ou la poudre de quartz, et donc de réduire la teneur en ciment dans BFUP, tout en ayant des propriétés comparables ou meilleures. De grandes quantités de déchets verre ne peuvent pas être recyclées en raison de leur fragilité, de leur couleur, ou des coûts élevés de recyclage. La plupart des déchets de verre vont dans les sites d'enfouissement, ce qui est indésirable puisqu’il s’agit d’un matériau non biodégradable et donc moins respectueux de l'environnement. Au cours des dernières années, des études ont été réalisées afin d’utiliser des déchets de verre comme ajout cimentaire alternatif (ACA) ou comme granulats ultrafins dans le béton, en fonction de la distribution granulométrique et de la composition chimique de ceux-ci. Cette thèse présente un nouveau type de béton écologique à base de déchets de verre à ultra-hautes performances (BEVUP) développé à l'Université de Sherbrooke. Les bétons ont été conçus à l’aide de déchets verre de particules de tailles variées et de l’optimisation granulaire de la des matrices granulaires et cimentaires. Les BEVUP peuvent être conçus avec une quantité réduite de ciment (400 à 800 kg/m³), de FS (50 à 220 kg/m³), de PQ (0 à 400 kg/m³), et de SQ (0-1200 kg/m³), tout en intégrant divers produits de déchets de verre: du sable de verre (SV) (0-1200 kg/m³) ayant un diamètre moyen (d[indice inférieur 50]) de 275 µm, une grande quantité de poudre de verre (PV) (200-700 kg/m³) ayant un d50 de 11 µm, une teneur modérée de poudre de verre fine (PVF) (50-200 kg/m³) avec d[indice inférieur] 50 de 3,8 µm. Le BEVUP contient également des fibres d'acier (pour augmenter la résistance à la traction et améliorer la ductilité), du superplastifiants (10-60 kg/m³) ainsi qu’un rapport eau-liant (E/L) aussi bas que celui de BFUP. Le remplacement du ciment et des particules de FS avec des particules de verre non-absorbantes et lisse améliore la rhéologie des BEVUP. De plus, l’utilisation de la PVF en remplacement de la FS réduit la surface spécifique totale nette d’un mélange de FS et de PVF. Puisque la surface spécifique nette des particules diminue, la quantité d’eau nécessaire pour lubrifier les surfaces des particules est moindre, ce qui permet d’obtenir un affaissement supérieur pour un même E/L. Aussi, l'utilisation de déchets de verre dans le béton abaisse la chaleur cumulative d'hydratation, ce qui contribue à minimiser le retrait de fissuration potentiel. En fonction de la composition des BEVUP et de la température de cure, ce type de béton peut atteindre des résistances à la compression allant de 130 à 230 MPa, des résistances à la flexion supérieures à 20 MPa, des résistances à la traction supérieure à 10 MPa et un module d'élasticité supérieur à 40 GPa. Les performances mécaniques de BEVUP sont améliorées grâce à la réactivité du verre amorphe, à l'optimisation granulométrique et la densification des mélanges. Les produits de déchets de verre dans les BEVUP ont un comportement pouzzolanique et réagissent avec la portlandite générée par l'hydratation du ciment. Cependant, ceci n’est pas le cas avec le sable de quartz ni la poudre de quartz dans le BFUP classique, qui réagissent à la température élevée de 400 °C. L'addition des déchets de verre améliore la densification de l'interface entre les particules. Les particules de déchets de verre ont une grande rigidité, ce qui augmente le module d'élasticité du béton. Le BEVUP a également une très bonne durabilité. Sa porosité capillaire est très faible, et le matériau est extrêmement résistant à la pénétration d’ions chlorure (≈ 8 coulombs). Sa résistance à l'abrasion (indice de pertes volumiques) est inférieure à 1,3. Le BEVUP ne subit pratiquement aucune détérioration aux cycles de gel-dégel, même après 1000 cycles. Après une évaluation des BEVUP en laboratoire, une mise à l'échelle a été réalisée avec un malaxeur de béton industriel et une validation en chantier avec de la construction de deux passerelles. Les propriétés mécaniques supérieures des BEVUP a permis de concevoir les passerelles avec des sections réduites d’environ de 60% par rapport aux sections faites de BC. Le BEVUP offre plusieurs avantages économiques et environnementaux. Il réduit le coût de production et l’empreinte carbone des structures construites de béton fibré à ultra-hautes performances (BFUP) classique, en utilisant des matériaux disponibles localement. Il réduit les émissions de CO[indice inférieur 2] associées à la production de clinkers de ciment (50% de remplacement du ciment) et utilise efficacement les ressources naturelles. De plus, la production de BEVUP permet de réduire les quantités de déchets de verre stockés ou mis en décharge qui causent des problèmes environnementaux et pourrait permettre de sauver des millions de dollars qui pourraient être dépensés dans le traitement de ces déchets. Enfin, il offre une solution alternative aux entreprises de construction dans la production de BFUP à moindre coût.

Construction and demolition waste as a source of PVC for recycling

Construction and demolition waste can contain considerable amounts of polyvinyl chloride (PVC). This paper describes a study of the recycling of PVC pipes collected from such waste materials. In a sorting facility for the specific disposal of construction and demolition waste, PVC was found to represent one-third of the plastics separated by workers. Pipes were sorted carefully to preclude any possible contamination by poly(ethylene terephthalate) (PET) found in the waste. The material was ground into two distinct particle sizes (final mesh of 12.7 and 8 mm), washed, dried and recycled. The average formulation of the pipes was determined based on ash content tests and used in the fabrication of a similar compound made mainly of virgin PVC. Samples of recycled pipes and of compound based on virgin material were subjected to tensile and impact tests and provided very similar results. These results are a good indication of the application potential of the recycled material and of the fact that longer grinding to obtain finer particles is not necessarily beneficial.

Aplicación de residuos en la fabricación de morteros industriales

La presente Tesis Doctoral estudia el uso de la fracción fina de los residuos de construcción y demolición (RCD) en la fabricación de morteros de albañilería. El principal uso de los áridos reciclados de RCD es la construcción de rellenos o firmes de carreteras, aunque su uso como áridos para la fabricación de hormigones o morteros le daría un mayor valor añadido. A nivel internacional existen numerosos estudios sobre la utilización de la fracción gruesa de los áridos reciclados de RCD en la fabricación de hormigones. Sin embargo son escasos los trabajos llevados a cabo para valorizar la fracción fina. Actualmente en España la fracción fina de los áridos reciclados de RCD está infrautilizada y en la mayoría de los casos depositada sin uso en los vertederos de las Plantas de reciclaje. En este trabajo se han utilizado dos tipos de áridos reciclados, uno procedente de residuos de hormigón (FRCA) y otro de residuos mixtos de tabiquería con un alto porcentaje de ladrillo rojo cerámico (FMRA). Todos los materiales han sido caracterizados desde un punto de vista físico, químico y mineralógico para justificar el efecto de su incorporación a la fabricación de morteros industriales de albañilería. En una primera fase se estudiaron las propiedades del mortero fresco y endurecido fabricado con FRCA y cinco niveles de sustitución volumétrica de arena natural y FRCA: 0%, 5%, 10%, 20% y 40%.Se utilizó un cemento puzolánico tipo CEM-IV y se evaluaron las propiedades a corto y largo plazo de morteros de baja resistencia (M5) En una segunda fase, se utilizó un cemento tipo CEM-II y se fabricaron morteros de mayor resistencia (M-10) utilizando FRMA. En esta etapa se llevaron a cabo sustituciones de arena natural por arena reciclada de 0%, 25%, 50%, 75% y 100%. El residuo fue evaluado medioambientalmente mediante el test de conformidad antes y después de ser ligado con cemento (lixiviación). Los resultados fueron completados con estudios de durabilidad. Con el objetivo de completar los estudios anteriores, se llevó a cabo una tercera fase, donde se sustituyó hasta un 100% de arena natural por FRCA, utilizando un cemento tipo CEM-II para fabricar un mortero tipo M-10, dosificado de manera similar al empleado en la segunda fase de este trabajo. Como conclusión general de esta tesis, se puede decir que pueden admitirse tasas de sustitución de hasta un 50% de arena natural por árido reciclado en morteros industriales de albañilería para usos de interior sin que sus propiedades puedan verse afectadas significativamente. Los resultados obtenidos contribuyen a reducir la extracción de arena natural de canteras y ríos, minimizar el consumo de energía y emisiones de CO2, mitigar el calentamiento global y evitar el depósito en vertedero de la fracción fina de RCD.

More than Metadata: Where the Rubber Meets the Road in DLS Migration

This panel presentation provided several use cases that detail the complexity of large-scale digital library system (DLS) migration from the perspective of three university libraries and a statewide academic library services consortium. Each described the methodologies developed at the beginning of their migration process, the unique challenges that arose along the way, how issues were managed, and the outcomes of their work. Florida Atlantic University, Florida International University, and the University of Central Florida are members of the state's academic library services consortium, the Florida Virtual Campus (FLVC). In 2011, the Digital Services Committee members began exploring alternatives to DigiTool, their shared FLVC hosted DLS. After completing a review of functional requirements and existing systems, the universities and FLVC began the implementation process of their chosen platforms. Migrations began in 2013 with limited sets of materials. As functionalities were enhanced to support additional categories of materials from the legacy system, migration paths were created for the remaining materials. Some of the challenges experienced with the institutional and statewide collaborative legacy collections were due to gradual changes in standards, technology, policies, and personnel. This was manifested in the quality of original digital files and metadata, as well as collection and record structures. Additionally, the complexities involved with multiple institutions collaborating and compromising throughout the migration process, as well as the move from a consortial support structure with a vendor solution to open source systems (both locally and consortially supported), presented their own sets of unique challenges. Following the presentation, the speakers discussed commonalities in their migration experience, including learning opportunities for future migrations.

The influence of particles recycling on the geochemistry of sediments in a large tropical dam lake in the Amazonian region, Brazil

The influence of particles recycling on the geochemistry of sediments in a large tropical dam lake in the Amazonian region, Brazil. Article in Journal of South American Earth Sciences 72 · December 2016 DOI: 10.1016/j.jsames.2016.09.012 1st Rita Fonseca 16.85 · Universidade de Évora 2nd Catarina Pinho 3rd Manuela Oliveira 22.6 · Universidade de Évora Abstract As a result of over-erosion of soils, the fine particles, which contain the majority of nutrients, are easily washed away from soils, which become deficient in a host of components, accumulating in lakes. On one hand, the accumulation of nutrients-rich sediments are a problem, as they affect the quality of the overlying water and decrease the water storage capacity of the system; on the other hand, sediments may constitute an important resource, as they are often extremely rich in organic and inorganic nutrients in readily available forms. In the framework of an extensive work on the use of rock related materials to enhance the fertility of impoverish soils, this study aimed to evaluate the role on the nutrients cycle, of particles recycling processes from the watershed to the bottom of a large dam reservoir, at a wet tropical region under high weathering conditions. The study focus on the mineralogical transformations that clay particles undergo from the soils of the drainage basin to their final deposition within the reservoir and their influence in terms of the geochemical characteristics of sediments. We studied the bottom sediments that accumulate in two distinct seasonal periods in Tucuruí reservoir, located in the Amazonian Basin, Brazil, and soils from its drainage basin. The surface layers of sediments in twenty sampling points with variable depths, are representative of the different morphological sections of the reservoir. Nineteen soil samples, representing the main soil classes, were collected near the margins of the reservoir. Sediments and soils were subjected to the same array of physical, mineralogical and geochemical analyses: (1) texture, (2) characterization and semi-quantification of the clay fraction mineralogy and (3) geochemical analysis of the total concentration of major elements, organic compounds (organic C and nitrogen), soluble fractions of nutrients (P and K), exchangeable fractions (cation exchange capacity, exchangeable bases and acidity) and pH(H2O).

Waste Mineral Filler Recycling in New Pavement Solutions

Società Azionaria Prodotti Asfaltico Bituminosi Affini (S.A.P.A.B.A. s.r.l.) is an asphalt/aggregate production plant located in Bologna, Italy. The resulting dirt and mud from the washing process is stored at specific sedimentation lakes close to the plant and are referred to as waste silt. The initiative and motivation of the current research follows the 12th objective of the sustainable development goals proposed by the United Nations. As a result, the overall aim of the current study was to reduce the impact of waste mineral fillers through recycling in new paving solutions. Considering three paving types of cement-bound, geopolymer-bound and asphalt pavements the following objectives were set: 1) To investigate the possibility of recycling waste silt in cement-bound paving solution; 2) To explore the feasibility of producing geopolymer-bound paving solutions containing waste silt; 3) To study the potential of using waste silt as fillers in different asphalt pavements. The first objective was achieved by utilizing waste silt into cement-bound materials. For this purpose, the by-product was introduced to cement mortars and was partially replaced (20%) with the natural sand. Moreover, statistical models were used to produce concrete paving blocks. The second objective was pursued by studying the feasibility of using the waste silt as a filler in geopolymer cement products. Following a comprehensive review, the silt was thermally calcined and used as filler in geopolymer cement and paving blocks. The third objective was achieved by evaluating the rheological and mechanical performance of hot mix, porous and semi-flexible asphalt containing waste silt. The limestone filler of a hot mix asphalt was replaced with thermally and untreated waste silt. To sum up, different paving blocks and asphalt pavements mixtures containing waste silt were proposed that presented acceptable performance when compared to different national and European standards.

High friction and acoustic surface for pavements: development of artificial engineered aggregates from recycled powders

There is a constant need to improve the infrastructure's quality and build new infrastructure with better designs. The risk of accidents and noise can be reduced by improving the surface properties of the pavement. The amount of raw material used in road construction is worrisome, as it is finite and due the waste produced. Environmentally-friendly roads construction, recycling might be the main way. Projects must be more environmentally-friendly, safer, and quieter. Is it possible to develop a safer, quieter and environmentally-friendly pavement surfaces? The hypothesis is: is it possible to create an Artificial Engineered Aggregate (AEA) using waste materials and providing it with a specific shape that can help to reduce the noise and increase the friction? The thesis presents the development of an AEA and its application as a partial replacement in microsurfacing samples. The 1st introduces the topic and provides the aim and objectives of the thesis. The 2nd chapter – presents a pavement solution to noise and friction review. The 3rd chapter - developing a mix design for a geopolymer mortar that used basalt powder. The 4th chapter is presented the physical-mechanical evaluation of the AEA. The 5th chapter evaluates the use of this aggregate in microsurfacing regarding the texture parameters. The 6th chapter, those parameter are used as an input to SPERoN® model, simulating their noise behavior of these solutions. The findings from this thesis are presented as partial conclusions in each chapter, to be closed in a final chapter. The main findings are: the DoE provided the tool to select the appropriate geopolymer mortar mix design; AEA had interesting results regarding the physical-mechanical tests; AEA in partial replacement of the natural aggregates in microsurfacing mixture proved feasible. The texture parameters and noise levels obtained in AEA samples demonstrate that it can serve as a HIFASP

Sustainable pavements for rural scenarios: laboratory and in-situ characterization of recycled materials and innovative construction solutions

Growing need for infrastructure has led to expanding research on advances in road pavement materials. Finding solutions that are sustainable, environmentally friendly and cost-efficient is a priority. Focusing such efforts on low-traffic and rural roads can contribute with a significant progress in the vital circulatory system of transport for rural and agricultural areas. An important alternative material for pavement construction is recycled aggregates from solid wastes, including waste from civil engineering activities, mainly construction and demolition. A literature review on studies is made; it is performed a planned set of laboratory testing procedures aimed to fully characterize and assess the potential in-situ mechanical performance and chemical impact. Furthermore, monitoring the full-scale response of the selected materials in a real field construction site, including the production, laying and compaction operations. Moreover, a novel single-phase solution for the construction of semi-flexible paving layers to be used as alternative material to common concrete and bituminous layers is experimented and introduced, aiming the production and laying of a single-phase laid material instead of a traditional two phases grouted macadam. Finally, on a parallel research work for farming pavements, the possible use of common geotechnical anti-erosive products for the improvement of soil bearing capacity of paddock areas in cattle husbandries of bio-farms is evaluated. this thesis has clearly demonstrated the feasibility of using the sustainable recycled aggregates for low-traffic rural roads and the pavements of farming and agriculture areas. The pavement layers constructed with recycled aggregates provided satisfying performance under heavy traffic conditions in experimental pavements. This, together with the fact that these aggregates can be available in most areas and in large quantities, provides great impetus towards shifting from traditional materials to more sustainable alternatives. The chemical and environmental stability of these materials proves their soundness to be utilized in farming environments.

Valorization and recycling of waste biomass and bioplastics into molecules, polymers and catalysts

The enormous amount of goods that world societies consume every day, derives from an immense consumption of energy and raw materials, and leads to an unthinkable amount of wastes. The abuse of fossil-based resources and the mismanaged waste is leading to big environmental pollution and climate change, with consequences on all living beings. To solve this issue and start living in equilibrium with nature, modern societies must stop using fossil fuels massively in favor to clean renewable energies, recycling, and biomass and waste utilization for materials and chemical production. Moreover, bioplastic recycling must be prioritized over their biodegrading and composting. This work is dedicated to the study of new synthetic strategies that fall into these fields.

Study of recycled Rap and Ra as alternative aggregates for pavements' sub-base and base

Nowadays, an important world’s population growth forecast establish that an increase of 2 billion people is expected by 2050. (UN,2019). This increment of people worldwide involves more humans, as well as growth of the demand for the construction of new residential, institutional, industrial, and infrastructural areas, prompting to a higher consumption of natural resources as required for construction materials. In addition, an effect of this population growth is the production and accumulation of waste causing a serious environmental and economic issue around the world. As an alternative to just producing more waste at the final stage of a building, house, road, among other concrete-based structures, adequate techniques must be applied for recycling and reusing these potential materials. The main priority of the thesis is to foment and evaluate the sustainable construction work leading to environmental-friendly actions that promote the reuse and recycling of construction waste, focusing on the use of construction recycled construction materials as an alternative for sub-base and base of road structure application. This thesis is committed to the analysis of the several laboratory tests carried out for achieving the physical-mechanical properties of the studied materials (recycled concrete aggregates + reclaimed asphalt pavement (RCA+RAP) and stabilized crushed sleepers). All these tests have been carried out in the Laboratory of Roads from the University of Bologna and in the experimental site in CAR srl., at Imola. The results are reported in tables, graphs, and are discussed. The mechanical properties values obtained from the laboratory tests are analysed and compared with standard values declared in the Italian and European normative for roads construction and to the results obtained from in-situ tests in the experimentation field (CAR srl in Imola) with the same materials. This to analyse the performance of them under natural conditions.

Dietary Supplement Usage And Motivation In Brazilian Road Runners.

The consumption of dietary supplements is highest among athletes and it can represent potential a health risk for consumers. The aim of this study was to determine the prevalence of consumption of dietary supplements by road runners. We interviewed 817 volunteers from four road races in the Brazilian running calendar. The sample consisted of 671 male and 146 female runners with a mean age of 37.9 ± 12.4 years. Of the sample, 28.33% reported having used some type of dietary supplement. The main motivation for this consumption is to increase in stamina and improve performance. The probability of consuming dietary supplements increased 4.67 times when the runners were guided by coaches. The consumption of supplements was strongly correlated (r = 0.97) with weekly running distance, and also highly correlated (r = 0.86) with the number of years the sport had been practiced. The longer the runner had practiced the sport, the higher the training volume and the greater the intake of supplements. The five most frequently cited reasons for consumption were: energy enhancement (29.5%), performance improvement (17.1%), increased level of endurance (10.3%), nutrient replacement (11.1%), and avoidance of fatigue (10.3%). About 30% of the consumers declared more than one reason for taking dietary supplements. The most consumed supplements were: carbohydrates (52.17%), vitamins (28.70%), and proteins (13.48%). Supplement consumption by road runners in Brazil appeared to be guided by the energy boosting properties of the supplement, the influence of coaches, and the experience of the user. The amount of supplement intake seemed to be lower among road runners than for athletes of other sports. We recommend that coaches and nutritionists emphasise that a balanced diet can meet the needs of physically active people.

Immobilization Of Papain On Chitin And Chitosan And Recycling Of Soluble Enzyme For Deflocculation Of Saccharomyces Cerevisiae From Bioethanol Distilleries.

Yeast flocculation (Saccharomyces cerevisiae) is one of the most important problems in fuel ethanol production. Yeast flocculation causes operational difficulties and increase in the ethanol cost. Proteolytic enzymes can solve this problem since it does not depend on these changes. The recycling of soluble papain and the immobilization of this enzyme on chitin or chitosan were studied. Some cross-linking agents were evaluated in the action of proteolytic activity of papain. The glutaraldehyde (0.1-10% w·v(-1)), polyethyleneimine (0.5% v·v(-1)), and tripolyphosphate (1-10% w·v(-1)) inactivated the enzyme in this range, respectively. Glutaraldehyde inhibited all treatments of papain immobilization. The chitosan cross-linked with TPP in 5 h of reaction showed the yield of active immobilized enzyme of 15.7% and 6.07% in chitosan treated with 0.1% PEI. Although these immobilizations have been possible, these levels have not been enough to cause deflocculation of yeast cells. Free enzyme was efficient for yeast deflocculation in dosages of 3 to 4 g·L(-1). Recycling of soluble papain by centrifugation was effective for 14 cycles with yeast suspension in time perfectly compatible to industrial conditions. The reuse of proteases applied after yeast suspension by additional yeast centrifugation could be an alternative to cost reduction of these enzymes.

Linear dimensional changes in plaster die models using different elastomeric materials

Dental impression is an important step in the preparation of prostheses since it provides the reproduction of anatomic and surface details of teeth and adjacent structures. The objective of this study was to evaluate the linear dimensional alterations in gypsum dies obtained with different elastomeric materials, using a resin coping impression technique with individual shells. A master cast made of stainless steel with fixed prosthesis characteristics with two prepared abutment teeth was used to obtain the impressions. References points (A, B, C, D, E and F) were recorded on the occlusal and buccal surfaces of abutments to register the distances. The impressions were obtained using the following materials: polyether, mercaptan-polysulfide, addition silicone, and condensation silicone. The transfer impressions were made with custom trays and an irreversible hydrocolloid material and were poured with type IV gypsum. The distances between identified points in gypsum dies were measured using an optical microscope and the results were statistically analyzed by ANOVA (p < 0.05) and Tukey's test. The mean of the distances were registered as follows: addition silicone (AB = 13.6 µm, CD=15.0 µm, EF = 14.6 µm, GH=15.2 µm), mercaptan-polysulfide (AB = 36.0 µm, CD = 36.0 µm, EF = 39.6 µm, GH = 40.6 µm), polyether (AB = 35.2 µm, CD = 35.6 µm, EF = 39.4 µm, GH = 41.4 µm) and condensation silicone (AB = 69.2 µm, CD = 71.0 µm, EF = 80.6 µm, GH = 81.2 µm). All of the measurements found in gypsum dies were compared to those of a master cast. The results demonstrated that the addition silicone provides the best stability of the compounds tested, followed by polyether, polysulfide and condensation silicone. No statistical differences were obtained between polyether and mercaptan-polysulfide materials.

Subcutaneous connective tissue response to primary root canal filling materials

This study evaluated the response of the subcutaneous connective tissue of BALB/c mice to root filling materials indicated for primary teeth: zinc oxide/eugenol cement (ZOE), Calen paste thickened with zinc oxide (Calen/ZO) and Sealapex sealer. The mice (n=102) received polyethylene tube implants with the materials, thereby forming 11 groups, as follows: I, II, III: Calen/ZO for 7, 21 and 63 days, respectively; IV, V, VI: Sealapex for 7, 21 and 63 days, respectively; VII, VIII, IX: ZOE for 7, 21 and 63 days, respectively; X and XI: empty tube for 7 and 21 days, respectively. The biopsied tissues were submitted to histological analysis (descriptive analysis and semi-quantitative analysis using a scoring system for collagen fiber formation, tissue thickness and inflammatory infiltrate). A quantitative analysis was performed by measuring the area and thickness of the granulomatous reactionary tissue (GRT). Data were analyzed by Kruskal-Wallis, ANOVA and Tukey's post-hoc tests (?=0.05). There was no significant difference (p>0.05) among the materials with respect to collagen fiber formation or GRT thickness. However, Calen/ZO produced the least severe inflammatory infiltrate (p<0.05). The area of the GRT was significantly smaller (p<0.05) for Calen/ZO and Sealapex. In conclusion, Calen/ZO presented the best tissue reaction, followed by Sealapex and ZOE.