Os elásticos ortodônticos intermaxilares são dispositivos auxiliares importantes para o tratamento ortodôntico. Os objetivos dessa pesquisa foram: comparar a intensidade de força dos elásticos informada pelos fabricantes com a força após estiramento de três vezes o diâmetro interno e avaliar o decaimento de força dos elásticos ortodônticos de várias empresas comerciais (Uniden, Morelli, Orthometric, Aditek, Rocky Mountain, TP Orthodontics e GAC Dentsply) de quatro tamanhos diferentes de diâmetro interno (1/8\"; 3/16\"; 1/4\" e 5/16\") com intensidade de força leve e média. Para esta pesquisa foi desenvolvido um dispositivo para simular os movimentos mandíbulo-maxilar durante a fala. Os elásticos foram submetidos a teste dinâmico e estático, por um período de 24 horas. Durante o teste, os elásticos, foram estirados ao comprimento de três vezes o diâmetro interno, de acordo com o índice de extensão padrão informado pelos fabricantes. Em seguida, iniciou-se o teste dinâmico, no qual, os elásticos eram alongados por mais 11mm correspondendo a distância maxilo-mandibular durante a fala, a uma frequência de 5 Hz. Esse ciclo repetiu-se por 10 minutos a cada hora durante 10 horas. Em três períodos os elásticos não participaram de nenhum teste, ou seja, foram removidos do dispositivo, simulando os horários das refeições. Completando assim o tempo de 12 horas do período diurno. Nos períodos restantes, 12 horas, os elásticos permaneceram em teste estático, ou seja, mantiveram estirados a 3 vezes o diâmetro interno, correspondendo ao período noturno do paciente no qual não apresenta movimento mandibulares significativos. As leituras das tensões-força geradas pelos elásticos foram realizadas por meio de um dispositivo de leitura de força modificada para mensurar elásticos quando estirados a distância de três vezes o lúmen. A leitura ocorreu a cada ciclo durante as primeiras 12 horas, uma inicial e a última ocorreu 24 horas após o início do teste, totalizando 14 leituras. Em função das características da amostra o teste estatístico utilizado foi o teste t de Student, ANOVA e teste Scott-Knott. A maior parte dos elásticos apresentaram diferença entre a força encontrada nesta pesquisa e a força informada pelo fabricante. Os elásticos com diâmetro interno de 1/8\" apresentaram ruptura durante os testes. Nos elásticos com diâmetro 3/16\" de intensidade de força leve, as empresas com melhores desempenhos foram: Morelli, Aditek, Uniden, GAC Dentsply, Orthometric, Rocky Mountain e TP Orthodontics. Nos elásticos com mesmo diâmetro, porém com intensidade de força média, a empresa com menor decaimento de força foi a Uniden, seguido por Morelli, GAC Dentsply, Rocky Mountain, Aditek, Orthometric, TP Orthodontics. Nos elásticos 1/4\" com intensidade de força leve, as empresas com menores decaimentos de forças formaram: Uniden, GAC Dentsply, Morelli, Rocky Mountain, TP Orthodontics, Aditek e Orthometric. Os elásticos 1/4\" com intensidade de força média, as empresas com menores decaimentos de forças foram: Uniden, seguido por Rocky Mountain, Morelli, Aditek, TP Orthodontics, GAC Dentsply e Orthometric. Os elásticos 5/16\" com intensidade de força leve, os elásticos da empresa Uniden apresentaram menores decaimentos de forças, seguido por GAC Dentsply, Aditek, Morelli, Rocky Mountain, Orthometric e TP Orthodontics. Nos elásticos 5/16\" de intensidade de força média, as empresas com menores decaimentos de forças foram: Uniden, Rocky Mountain, Morelli, GAC Dentsply, Aditek, Orthometric e TP Orthodontics. Em seguida à análise dos resultados, conclui-se que o maior decaimento de força dos elásticos ocorreram na primeira hora de teste, em média 12,78%, em seguida, a esse período, ocorre um decaimento de menor intensidade de força, em média de 6,95%, durante o período de 24 horas. Sendo indicado as trocas dos elásticos diariamente. / Intermaxillary latex orthodontic elastics are important auxiliary devices for orthodontic treatment. This study aimed to assess force decay of several commercial brands (Uniden, Morelli, Orthometric, Aditek, Rocky Mountain, TP Orthodontics, and GAC Dentsply) and four sizes (1/8\"; 3/16\"; 1/4\"; and 5/16\") with low and median force intensity. A device that simulates mandibular and maxillary speech movement of patients was developed for this research. The elastics were simultaneously subjected to dynamic and static tests for 24 hours. During the static test, the elastics were stretched three times the distance of the inner diameter, as recommended by the manufacturers. Next, the dynamic test began, where the elastics were stretched by an additional 11 mm, which corresponds to the maxillary and mandibular distance during speech, at a 5 Hz rate. This cycle was repeated for 10 minutes every 10 hours. In three periods, the elastics did not participate of any test, meaning they were removed from the device to simulate meal times; thus, the 12-hour daytime was completed. Over the 12 hours remaining, the elastics were maintained in static test, meaning they were stretched three times the inner diameter, which corresponds to the night time of the patient, who did not present significant mandibular movements. Force readings were performed at each cycle over the first 12 hours, and the last reading was performed 24 hours after the beginning of the test. Due to the characteristic of the sample, the statistical tests used were Student t test, ANOVA, and Scott-Knott test. Most of the elastics presented difference between the force found in this research and the one informed by the manufacturer. The 1/8\" (3.2 mm) elastics showed rupture during tests. In the 3/16\" (4.8 mm) elastics with low force intensity, the best-performing brands were Morelli, Aditek, Uniden, GAC Dentsply, Orthometric, Rocky Mountain, and TP Orthodontics over 24 hours of testing. In elastics with the same diameter but median force intensity, the brand with less force decay was Uniden, followed by Morelli, GAC Dentsply, Rocky Mountain, Aditek, Orthometric, and TP Orthodontics. In the 1/4\" elastics with light force intensity, the brands with less force decay were Uniden, GAC Dentsply, Morelli, Rocky Mountain, TP Orthodontics, Aditek, and Orthometric. In the 1/4\" elastics with medium force intensity, the brand with less force decay was, again, Uniden, followed by Rocky Mountain, Morelli, Aditek, TP Orthodontics, GAC Dentsply, and Orthometric. In the 5/16\" (7.9 mm) elastics with light force intensity, the brand Uniden presented better performance, followed by GAC Dentsply, Aditek, Morelli, Rocky Mountain, Orthometric, and TP Orthodontics. In the 5/16\" elastics with median force intensity, the brands with less force decay were Uniden, Rocky Mountain, Morelli, GAC Dentsply, Aditek, Orthometric, and TP Orthodontics. After the analysis of results, it was concluded that the greatest force decay of elastics occurred in the first hour of testing with 12.78% in average; after this period, there was a reduced force decay of 6.95% in average, over 24 hours. Daily changes of elastics are recommended.

O couro vegetal é obtido através do revestimento de tecido de fibras celulósicas com látex de campo ou concentrado, extraído de seringueira (Hevea spp.). A produção do couro vegetal já ocorre atualmente, possibilitando manter os seringueiros da região norte do Brasil em sua atividade com melhor valor agregado ao produto, sendo ainda submetido ao processo de vulcanização associado à defumação. Adicionalmente, dá ao produtor de seringueira possibilidade de agregar valor ao seu produto e cria alternativa de matéria-prima com padrão de qualidade para a indústria da moda que trabalha exclusivamente com couro animal. Entretanto, há pouca informação científica e tecnológica sobre os processos de produção e métodos de avaliação do couro vegetal. O presente trabalho teve como objetivo avaliar a resistência à tração de couro vegetal produzido tecido de algodão impregnado com látex de diferentes cultivars de seringueira e submetido à vulcanização lenta. Amostras de látex de cinco cultivars de seringueiras GT 1, PR 107, PB 235, IAN 873 e RRIM 600, em campo de competição de clones do Campo Experimental do Departamento de Produção Vegetal da ESALQ/USP foram preparadas para vulcanização com mistura de aditivos padrões e utilizadas para impregnação de tecido de algodão cru, seguida de vulcanização lenta. Corpos de prova desses couros vegetais foram submetidos a teste de resistência à tração. O couro vegetal feito com látex do cultivar GT 1 apresentou maior resistência à tração que aquele feito com látex de RRIM 600, e os demais apresentaram resistências intermediárias. / The vegetal leather is made by coating cotton cloth with field or concentrated latex extracted from rubber trees (Hevea spp.). Currently, the production of vegetal leather already occurs in the Northern Brazil, associated with smoking and vulcanization, making possible to retain rubber tappers in the region. In addition, it permits rubber planters to aggregate some more values to its products and to create an alternative of raw material to the fashion industry, in replacement of animal leather. However, the product is not standardized and there is a lack of scientific and technological information about the production process and evaluation procedures. The objective of the present research was to evaluate the tension resistance of vegetal leather made of cotton cloth impregnated with latex of different rubber tree clones and submitted to vulcanization. Samples of latex from the rubber tree clones GT 1, PR 107, PB 235, IAN 873 e RRIM 600, cultivated at the Experimental Field of the Crop Production Department at ESALQ/USP, were prepared for vulcanization with standard mixture of addictives and used to coat cotton clothes followed by slowly vulcanization. Proof bodies of these vegetal leathers were submitted to tests tension resistance. The vegetal leather made of GT1 latex presented a tension resistance superior to that made of RRIM 600 latex, the others presented intermediate resistances.

Problemas de consolidação óssea são um grande desafio clínico, pois geram altos custos de tratamento, morbidades e prejuízos a qualidade de vida. A técnica de regeneração óssea guiada é empregada com o intuito de promover a melhora no processo de regeneração de defeitos ósseos através da utilização de barreiras biológicas, que protegem o local da lesão e favorecem a ação de células osteogênicas. A membrana de látex natural, extraído da seringueira Hevea brasiliensis tem sido apontado como um biomaterial promotor da regeneração em diferentes tecidos, e por este motivo escolhido como objeto de estudo desta pesquisa. O objetivo foi avaliar o efeito da utilização de membrana de látex natural no processo de regeneração guiada de defeito ósseo em ossos longos de ratos, através de análises estruturais, radiológicas, microscópicas e da expressão de proteínas osteogênicas. Foram utilizados sessenta ratos Wistar divididos igualmente em quatro grupos (n=15), sendo: animais tratados com membrana de látex por uma (L1) ou quatro semanas (L4) e animais que não receberam tratamento específico por uma (C1) ou quatro semanas (C4). Um defeito ósseo de 2,5 mm de diâmetro foi realizado na região medial da tíbia esquerda de cada animal. Nos animais do grupo tratado, uma membrana de látex foi posicionada sobre os defeitos ósseos. Após os períodos experimentais de uma ou quatro semanas os animais foram submetidos a eutanásia e a tíbia esquerda de cada animal foi dissecada, limpa das partes moles e submetida às análises macroscópica, densitométrica, radiológica, mecânica, histomorfométrica, estereológica e imunohistoquímica. A influência das varáveis tempo e membrana, bem como a interação tempo*membrana sobre os dados foram avaliadas. Para os dados referentes à imunomarcação de osteocalcina foi aplicado teste de modelo linear generalizado com fatores independentes. Para o restante dos resultados foi realizada análise de ANOVA multivariada com dois fatores independentes. Todas as comparações foram realizadas com ajuste de Bonferroni e adotado nível de significância de 5%. Foram observadas diferenças estatisticamente significantes em relação a variável tempo, em que grupos avaliados quatro semanas após a cirurgia apresentaram resultados superiores para as medidas de comprimento (p<0,001), massa (p<0,001), força máxima (p<0,001) e rigidez relativa da tíbia (p<0,001), bem como para as medidas de densidade radiológica (p=0,008), densidade mineral óssea (p=0,017), volume ósseo neoformado (p<0,001) e fibras de colágeno tipo III (p<0,001). Em relação à utilização da membrana de látex, os grupos tratados apresentaram resultados estatisticamente superiores para as análises de rigidez relativa (p=0,048), fibras de colágeno tipo I (p=0,018), volume ósseo neoformado (p<0,001) e expressão de osteopontina (p=0,037). Concluímos que a utilização de membrana de látex em regeneração óssea guiada em defeitos realizados em tíbias de ratos melhorou sensivelmente a regeneração do tecido. / Problems of bone consolidation are a significant clinical challenge, as they generate high treatment costs, morbidities, and damages to the quality of life. The guided bone regeneration technique is used to improve the regeneration process of bone defects through the use of biological barriers that protect the site and favor the action of osteogenic cells. The natural latex membrane extracted from the rubber tree Hevea brasiliensis has been identified as a biomaterial promoting regeneration in different tissues, and for this reason chosen as the object of study of this research. The objective was to evaluate the effect of the use of natural latex membrane in the process of guided regeneration of bone defect in long bones of rats, through structural, radiological, microscopic analysis and the expression of osteogenic proteins. Sixty Wistar rats were equally divided into four groups (n = 15): latex membrane treated animals for one (L1) or four weeks (L4) and animals that received no specific treatment for one (C1) or four weeks (C4). A bone defect of 2.5 mm diameter was performed in the medial region of the left tibia of each animal. In the animals of the treated group, a latex membrane was positioned over the bone defects. After the experimental periods of one or four weeks, the animals were submitted to euthanasia, and the left tibia of each animal was dissected, cleaned of soft parts and submitted to macroscopic, densitometric, radiological, mechanical, histomorphometric, stereological and immunohistochemical analysis. The influence of the variable time and membrane as well as the time * membrane interaction on the data were evaluated. For the data referring to the osteocalcin immunostaining, a generalized linear model with independent factors was applied. For the rest of the results, a multivariate ANOVA analysis was performed with two independent factors. All comparisons were performed with Bonferroni adjustment and adopted a significance level of 5%. Statistically significant differences were observed in relation to the time variable, in which groups evaluated four weeks after surgery presented superior results for the measures of length (p <0.001), mass (p <0.001), maximal strength (p <0.001) and stiffness (P <0.001), as well as for measurements of radiological density (p = 0.008), bone mineral density (p = 0.017), neoformed bone volume (p <0.001) and type III collagen fibers (p <0.001) ). About the use of the latex membrane, the treated groups presented statistically superior results for analyzes of relative stiffness (p = 0.048), type I collagen fibers (p = 0.018), neoformed bone volume (p <0.001) and expression of Osteopontin (p = 0.037). We conclude that the use of latex membrane in guided bone regeneration in defects performed in rat tibiae significantly improved tissue regeneration.

Cette thèse, menée en collaboration avec Michelin dans le cadre de la fabrication de matériaux composites, porte sur la stabilité colloïdale du latex de caoutchouc naturel (NR). Ce latex est une dispersion colloïdale polydisperse d'un polymère naturel dans un sérum aqueux. Les particules sont stabilisées par une couche complexe de phospholipides et de protéines. Cette dispersion peut être coagulée de façon irréversible par voie physique (sous cisaillement) ou par voie physico-chimique (ajout de cations divalents ou de particules hydrophobes). Dans ce travail, nous avons étudié la coagulation du latex par les cations divalents. Pour cela nous avons utilisé des outils physico-chimiques : diagrammes de stabilité en présence de divers cations, suivi cinétique de l'agrégation des particules et mesures rhéologiques. Ensuite, nous avons sondé la surface de particules de NR, par électrophorèse, en présence de tensioactifs et aussi selon la taille des particules. Pour expliquer la coagulation, nous suggérons que l'augmentation de la force ionique écrante les interactions répulsives et que les cations forment des ponts ioniques entre les particules. Ces ponts les maintiennent au contact et l'irréversibilité du phénomène est assurée par l'adhésion entre les chaines de polymères proches de la surface. L'adsorption des tensioactifs modifie la surface des particules et la coagulation du latex. Une légère différence de charge de surface a été observée entre les particules de NR selon leur taille. Enfin, un phénomène de coagulation similaire a été obtenu avec un latex synthétique, ce qui ouvre la voie à l'exploitation industrielle de ce phénomène de coagulation. / This work, in collaboration with Michelin for the fabrication of composite materials, deals with the colloidal stability of the latex of natural rubber (NR). The NR latex is a polydisperse colloidal dispersion of a bio-polymer in an aqueous serum. The particles are stabilized by a complex layer of phospholipids and proteins. This dispersion can be coagulated by a physical way (under shearing), or by a physical-chemical way (addition of divalent cations or hydrophobic particles). In this thesis, we studied the coagulation of the NR latex by divalent cations with physical-chemical tools (stability diagrams with different cations, aggregation kinetic of particles, rheological measuremments). Then, the surface of NR particles has been characterized by electrophoresis, firstly in the presence surfactants and secondly depending on the particles size. From the results of the first part we suggest that the coagulation with divalent cations is due to a screening effect because of the increase of ionic strength and that divalent cations can bridge the particles together. This allows keeping them in contact. Adhesion between polymer chains near the surface ensures the irrversible cohesion. In a second time, we saw that the adsorption of surfactants changes the particles surface and the coagulation of NR latex with cations. A small difference of surface charge is observed between the biggest and the smallest NR particles. Finally, a similar behavior has been obtained with a synthetic latex in presence of divalent cations. Our results could be used to develop an industrial process based on this coagulation phenomenon.

Water-borne coatings have increased in popularity due to the recent environmental regulations being placed on coating formulation. The most readily available coatings without volatile organic compounds are thermoplastic polymer dispersions that rely on interdiffusion to form a film. These dispersions are reliant on toxic crosslinking chemistries to achieve adequate coating mechanical properties, but still have significantly inferior properties when compared with current thermosetting industrial coatings that contain volatile organic compounds. As a result, waterborne coatings made with conventional emulsion polymers cannot be considered for high-performance coatings. Polyurethane dispersions have been developed that can meet these demands, but require several lengthy coating applications and are therefore incredibly costly. A water-based acrylic emulsion polymer coating that could self-stratify and apply multiple crosslinkable layers simultaneously, has the potential to revolutionize current coating formulations. Recent advances in anisotropic polymer colloid synthesis offer a potential pathway to make such a high-performance coating. Incorporating unique functionality into each of the lobes of a bilobal particle would enable the formation of a new class of water-based, self-stratifying, high-performance, acrylic coatings. The primary goal of this thesis was to show proof of concept for a bilobal platform that could be used to form water-based self-stratifying coatings. The approach was adapted from recent advances in pigment-associating emulsion polymers used to improve coating pigment dispersion. Butyl acrylate and methyl methacrylate seed particles ~90 nm in size were formed and subsequently used to synthesize preliminary ~130 nm acrylic bilobal particles, within the target size range of water based coating dispersions. Control over the seed particle glass transition temperature, size, and morphology, and synthesis of promising preliminary bilobal particles was demonstrated; this was accomplished using a systematic analysis of various reaction conditions, namely, pre-emulsification, reaction duration, and the concentrations of the monomers. Expanding upon the chemical versatility would enable these particles to be used in a wide variety of applications, but this thesis represents a promising start for the bilobal platform within the coating industry.

Surfactants and Thickeners are both additives used in fully-formulated waterborne coatings to provide colloidal stability, thickening, and other functionality. The behavior of each ingredient in a coating must be understood and controlled to maintain colloidal stability as well as balance other desired properties of the liquid coating and the dry paint film. In this work, quaternary systems of Water-Latex-Thickener-Surfactant were investigated to further the understanding of their behavior in coatings. The thickener used was a well characterized, hydrophobically-modified, ethoxylated urethane (HEUR) with two C18 terminal hydrophobes and 795 average repeat units of ethylene oxide as the hydrophilic spacer. Two latexes, a hydrophobic butyl acrylate/styrene and a hydrophilic butyl acrylate/methyl methacrylate, each containing a small amount of methacrylic acid monomer were used. Six different surfactants, three non-ionic and three-anionic, were used. By maintaining the concentrations of latex and HEUR thickener as constants and varying the surfactant concentration, effects of the surfactant loading on rheology were determined. As concentration of surfactant increases, a characteristic shear-thickening maximum associated with bridging of latex particles by the HEUR thickener was seen to shift to higher shear rates; surfactants at all concentrations studied, except SDS, lowered the viscosities within the low shear rate region. Dynamic viscoelastic measurements shed further light into the behavior of the mixtures. The results will be explained based on surfactant and latex surface polarities and the competitive adsorption between the v surfactant and HEUR hydrophobes, and other interactions between surfactants and thickeners.

Toxoplasma gondii is a single-celled parasite that has a wide range of hosts including humans. A cross-sectional survey was conducted to investigate T. gondii seroprevalence and associated risk factors in small ruminants, pigs, poultry and cats in the Oliver Reginald Tambo District in the Eastern Cape in South Africa between June 2016 and October 2016. Household-level and animal-level data were collected using a close-ended questionnaire. One sample of each present species was collected in each household. The Toxoreagent ®, Mast Group, United Kingdom, latex agglutination test, was used for T. gondii antibody detection. Positive samples had agglutination patterns at dilutions of 1:64 or greater, except for chickens, whose cut off titre was 1:32. A household was classified as T. gondii seropositive if at least one species tested positive. The study revealed that 78 out of 121 sheep (64.46%), 69 out of 128 goats (53.91%), 36 out of 106 pigs (33.96%), 35 out of 109 cats (32.11%) and 46 out of 137 chickens (33.58%) were seropositive for the parasite. Seropositivity was assessed for association with potential risk factors. Age, location, climate, animal production system, rodent control, cat-feed access and cat faecal disposal were found to be significantly associated with seropositivity using the Chi-Squared test or odds ratio confirmed by the Fisher's exact test. The relatively high seroprevalence of T. gondii detected in this study suggests that the infection T. gondii poses a substantial public health risk through the consumption of infected raw or undercooked meat infected with T.gondii cysts as well as contact with cat faeces infected with T. gondii oocysts. / Dissertation (MSc)--University of Pretoria, 2016. / Veterinary Tropical Diseases / MSc / Unrestricted

Interior flat, white latex paint is a common coating applied to walls around the world. Development of a coating with one coat hide capability is a pinnacle achievement for paint formulators as it has the potential to save consumers both time and money. One coat paints already exist on the market, but they are limited in color, coverage, and often have many disclaimers. Work done was part of a project initiated by ChemoursTM Titanium Technologies. The goal of the project presented in this article was to create an interior flat, white latex paint that yields a spread rate of greater than 400 ft2/gal., which is advertised by many below critical pigment volume concentration (CPVC) commercial paints. In order to achieve this goal, an above CPVC paint with a high TiO2 content was created and continuously improved. Improvement of the formulation involved numerous experimental variations including adjustments to the hydroxyethylcellulose (HEC) molecular weight, dispersant chemistry, latex chemistry, TiO2 concentration, extender package, and rheology modifier type. The sheen value, relative light scattering, and spread rate were the main measurements conducted in order to judge formulation improvement. Complications with the spread rate procedure forced its adaptation in order to collect less variable data with the high density, shear thinning formulations. It was found that shorter opacity charts yielded more precise spread rate data than the longer opacity charts. An attempt at correlating rheology with sheen development resulted in the conclusion that the pigment and extender particle package is the greatest driving factor behind sheen reduction. The rheology modifier type and dispersant chemistry did not affect the flatness of the paint nearly as much. A Keyence VR-3000 series One-Shot 3D Measuring Macroscope was used to show that surface roughness does not directly correlate to the sheen value when a number of flat paints with different sheens were analyzed. This project is an ongoing effort and the information contained in this document will substantially help future development.

This master´s thesis considers implementation of a standard of bibliographic quotation BibTeX using the XML technology. This project starts with theoretical introduction into XML technology problematics. Next part contains introduction into LATEX and its subprogram BibTEX and into its function. Later, the principle of implementation and important parts of XSL transformation (from output les *.bib. *.tex, *.html) source code will be described. Verication of functionality of the implementation is demonstrated using BibTEX database of used literature generated by XML technology.

This study describes the design of an integrated tool in text editor designated for documents written in LaTeX format. It offers the ability of tracking, storing and approving changes in document as a support for team cooperation, when writing a document. Application is designed mainly for operating system Windows. It works with LaTeX distribution MikTeX and the text editor Texmaker.