Microwave-assisted extraction and content determination of astilbin in Lysiphyllum strychnifolium stems

Abstract Lysiphyllum strychnifolium (Craib) A. Schmitz. (in Thai name, Ya nang daeng) has been traditionally used to treat fever, alcohol intoxication, cancer, allergies, and blood toxins. It can be used as a health-promoting herbal tea and contains hydroalcoholic extracts. The purpose of the present study was to develop a microwave-assisted extraction method for astilbin in L. strychnifolium stems. HPLC was used to determine astilbin content. Three extraction conditions were optimized: types of solvent, microwave power levels, and the number of extraction cycles. Water:methanol (40:60) was the best solvent for astilbin extraction from L. strychnifolium stems using 450 watts and six microwave-assisted extraction cycles. This technique offers important advantages over conventional methods, such as shorter extraction times, substantial energy savings, and a reduced environmental burden.

Rapid hemostasis: a novel and effective outpatient procedure using microwave ablation to control epistaxis of isolated mucosal bulge lesions / Hemostasia rápida: um procedimento ambulatorial novo e eficaz utilizando ablação por micro-ondas para controlar a epistaxe de lesões isoladas protuberantes da mucosa

Abstract Introduction Recurrent epistaxis is commonly encountered in the rhinology outpatient clinic. Under endoscopic guidance, both bipolar cautery and monopolar forceps (combined with suction) have been employed to control the bleeding. However, the use of monopolar forceps requires the placement of grounding pads. Most procedures are currently performed in operating rooms. Objective We investigated outcomes after the use of Microwave Ablation (MWA) to control epistaxis in adults with isolated mucosal bulge lesions. All procedures were performed with patients under local anesthesia in our outpatient clinic. Methods This is a retrospective cohort study. We included 83 adults with epistaxis of isolated mucosal bulge lesions. Microwave ablation was performed in the outpatient clinic to control bleeding, after induction of local anesthesia. The primary outcome was successful hemostasis. The secondary outcomes were the rebleeding rates at weeks 1 and 4 and month 6, and complications (crust or synechiae formation, septal perforation, and/or orbit or brain complications). Results All bleeding points were successfully ablated; hemostasis was achieved within 1-2 min. The mean pain score was 1.83 intra-operatively and 0.95 1 h postoperatively. No patient re-bled, and no severe MWA-related complication (septal perforation, synechiae formation, or orbit or brain complication) was recorded to 6 months of follow-up. Conclusions Endoscopic microwave ablation with patients under local anesthesia is a novel, safe, effective, rapid, well-tolerated, outpatient treatment for adults with epistaxis of isolated mucosal bulge lesions, especially those for whom general anesthesia might be risky, those with electrical implants, and those exhibiting contraindications for arterial embolization.

Resumo Introdução Epistaxe recorrente é comumente encontrada no ambulatório de rinologia. Sob orientação endoscópica, foram empregados tanto o cautério bipolar quanto a pinça monopolar (combinados à sucção) para controlar a condição. No entanto, o uso de pinças monopolares requer a colocação de placas de aterramento. Atualmente, a maioria dos procedimentos é feita em salas de cirurgia. Objetivo Investigamos os resultados após o uso da ablação por micro-ondas (MWA, do inglês Microwave Ablation) no controle da epistaxe em adultos com lesões isoladas protuberantes da mucosa. Todos os procedimentos foram feitos em nosso ambulatório com os pacientes sob anestesia local. Métodos Estudo de coorte retrospectivo. Foram incluídos 83 adultos com epistaxe de lesões isoladas protuberantes da mucosa. A ablação por micro-ondas foi feita no ambulatório para controlar o sangramento, após a administração de anestesia local. O desfecho primário foi uma hemostasia bem-sucedida. Os desfechos secundários foram as taxas de ressangramento, nas semanas 1 e 4 e no mês 6, e complicações (formação de crostas ou sinéquias, perfuração septal e/ou complicações orbitais ou cerebrais). Resultados Todos os pontos de sangramento foram contidos com sucesso; a hemostasia foi alcançada em 1-2 minutos. O escore médio de dor foi de 1,83 no intraoperatório e de 0,95 1 h no pós-operatório. Nenhum paciente apresentou ressangramento e nenhuma complicação grave relacionada à MWA (perfuração septal, formação de sinéquias ou complicações orbitais ou cerebrais) foi registrada em 6 meses de seguimento. Conclusões A ablação endoscópica por micro-ondas com pacientes sob anestesia local é um tratamento ambulatorial novo, seguro, eficaz, rápido e bem tolerado para adultos com epistaxe de lesões isoladas protuberantes da mucosa, especialmente aqueles para os quais a anestesia geral pode ser arriscada, indivíduos com implantes elétricos e aqueles com contraindicações para embolização arterial.

Strategies for potential toughening of acrylic denture bases polymerized with microwave energy

Abstract Thiourethane additives have been shown to improve properties in several dental polymer applications. The aim of this study was to verify the effect of the addition of thiourethane oligomers and acrylamide or isobornyl-based plasticizers on the physical properties of the denture base acrylic resin polymerized with microwaves. Thiourethane oligomer (TU) was synthetized and added to microwaved acrylic resin in proportions varying between 3 and 14 wt%. Separate experimental groups included the addition of dimethyl acrylamide (DMAM) and isobornyl methacrylate as plasticizers, at concentrations varying from 5 to 20 wt%. Samples were polymerized using microwave energy at 500 Watts for 3 min, deflasked at room temperature, stored in water at 37 °C for 24 h, and evaluated for: linear dimensional change, gloss, Knoop hardness, surface roughness, impact strength, yield strength, elastic modulus, toughness, yield strength, viscosity, glass transition temperature and network heterogeneity, and water sorption/solubility. Data were analyzed with ANOVA/Tukey's post-hoc test (a=5%). The addition of TU led to properties that were similar or worse than the materials to which it was not added, except for dimensional stability. The impact on properties was statistically significant for all materials above 20% addition of TU. The addition of DMAM at 5 wt% or isobornyl methacrylate at 10 wt% improved yield strength and modulus, but increased water sorption and solubility. Except for dimensional stability, the addition of thiourethane oligomers to acrylic denture base materials compromised most tested properties. The use of DMAM and isobornyl methacrylate improved properties for selected compositions.

Resumo Aditivos de tiouretano demonstraram melhorar propriedades de polímeros em diversas aplicações. O objetivo deste estudo foi verificar o efeito da adição de oligômeros de tiouretano, monômeros de acrilamida ou baseados em funcionalidade isobornil na propriedades físicas de bases de dentadura de acrílico polimerizadas em micro-ondas. O oligômero de tiouretano (TU) foi sintetizado e adicionado à resina acrílica em proporções variando de 3 a 14% em peso. Dimetil acrilamida (DMAM) e isobornil metacrilato (IBMA) foram adicionados em formulações separadas como plastificantes em concentrações variando de 5 a 20% em peso. As amostras foram polimerizadas usando energia de micro-ondas (500 Watts oor 3 min), desincluídas da mufla a temperature ambiente, armazenadas em água a 37°C por 24 h, e submetidas aos testes de: alteração dimensional linear, brilho, dureza Knoop, rugosidade superficial, resistência ao impacto, tensão normal de escoamento, módulo de elasticidade, tenacidade, viscosidade, temperatura de transição vítrea e heterogeneidade da rede polimérica, além de sorção de água e solubilidade. Os dados foram analisados com ANOVA e teste de Tukey (a=5%). A adição de TU não afetou ou diminuiu todas as propriedades, exceto pela estabilidade dimensional. O impacto nas propriedades foi estatisticamente significante para todos os materiais em concentrações acima de 20% de TU. Isso pode ser explicado por um encurtamento das cadeias e diminuição do empacotamento das cadeias lineares do PMMA. A adição de 5% de DMAM ou 10% de isobornil metacrilato melhoraram a tensão de escoamento e o módulo, mas aumentaram a sorção de água e solubilidade. Exceto pela estabilidade dimensional, a adição de oligômeros de tiouretano à bases de dentatura compostas por resina acrílica prejudicou todas a propriedades testadas. O uso de DMAM e isobornil metacrilato melhorou as propriedades para composições selecionadas.

Efeito da polimerização adicional com micro-ondas na rugosidade superficial de duas resinas compostas / Effect of additional microwave polymerization on the surface rugosity of two compound resins

Introdução: a resina composta é um dos materiais restauradores mais pesquisados na Odontologia, visando melhorias nas suas propriedades e aperfeiçoamento da técnica. Este trabalho tem o objetivo de avaliar a rugosidade superficial de duas resinas compostas, micro-híbrida e nanoparticulada, após a polimerização adicional com micro-ondas. Materiais e métodos: para cada resina composta, foram confeccionados 24 corpos de prova, medindo 0,8 cm de diâmetro interno por 0,2 cm de espessura, dos quais, 12 receberam polimerização adicional com micro-ondas e 12, apenas a polimerização com luz azul visível. Foram estabelecidos quatro grupos: G1 - resina micro-híbrida submetida à polimerização convencional; G2 - resina nanoparticulada submetida à polimerização convencional; G3 - resina micro-híbrida exposta à polimerização adicional em forno de micro-ondas caseiro; e G4 - nanoparticulada exposta à polimerização adicional em forno de micro-ondas caseiro. Os corpos de prova foram lixados em politriz, com o intuito de uniformizar as superfícies, seguindo com leitura no rugosímetro digital Mitutoyo SJ 301. O teste não paramétrico Exato de Mann-Whitney (significância de 5%) foi realizado utilizando a média aritmética (Ra, µm). Conclusão: não houve significância estatística entre os tipos de polimerização e nem entre as diferentes resinas compostas estudadas.(AU)

Introduction: composite resin is one of the most researched restorative materials in dentistry, aiming to improve its properties and improve the technique. This work aims to evaluate the superficial rugosity of two composite resins, microhybrid and nanoparticulate, after additional polymerization with microwaves. Materials and methods: for each composite resin, 24 specimens were made, measuring 0.8cm internal diameter by 0.2cm thick, of which 12 received additional microwave polymerization and 12 visible-blue-light polymerization only. Four groups were established: G1 - microhybrid resin subjected to conventional polymerization; G2 - nanoparticulate resin subjected to conventional polymerization; G3 - microhybrid resin exposed to additional polymerization in a home microwave oven; and G4 - nanoparticulate exposed to additional polymerization in a home microwave oven. The specimens were sanded in a polishing machine in order to standardize the surfaces, followed by reading on the Mitutoyo SJ 301 digital roughness meter. The Mann-Whitney Exact nonparametric test (5% significance) was performed using the arithmetic mean (Ra, µm). Conclusion: there was no statistical significance between the polymerization types and neither among the different composite resins studied.(AU)

Efecto de cocción en horno convencional y microondas sobre rancidez, pérdida por cocción y diferencia sensorial de hamburguesas / Effect of conventional oven versus microwave cooking on rancidity, cooking loss and sensory difference of hamburger patties

El uso de microondas está muy extendido a nivel doméstico gracias a su rapidez y facilidad de uso. El objetivo del presente trabajo es comparar el efecto de cocción de hamburguesas de distintos tipos de carne, en microondas y en horno convencional, sobre la pérdida de peso y estabilidad oxidativa. Además, determinar si existen diferencias desde el punto de vista sensorial aplicando una prueba triangular, comparando 2 productos presentados en tríos, uno que corresponde a hamburguesa cocida en microondas y otro a hamburguesa cocida en horno convencional. Se adquirieron hamburguesas de pollo, pavo, cerdo y vacuno en el comercio, se cocinaron en horno convencional y en microondas. Se calculó pérdida por cocción, se evaluó la rancidez y diferencias sensoriales entre hamburguesas del mismo tipo de carne, cocidas en distinto tipo de horno. La pérdida por cocción fue menor en hamburguesas cocidas en microondas. La acidez e índice de peróxido aumentaron en las muestras cocidas en ambos tipos de hornos respecto a hamburguesas crudas. La acidez fue mayor en hamburguesas cocidas en horno convencional, y el índice de peróxido fue mayor en hamburguesas cocidas en microondas, llegando a 10,6 meq O2/kg. En el análisis sensorial se encontraron diferencias significativas (p<0,05) entre las hamburguesas cocidas en horno convencional y en microondas. Resulta mejor opción cocinar hamburguesas en horno convencional, ya que el índice de peróxidos es menor que al cocinar en microondas; dentro del tipo de hamburguesas, son más estables las de vacuno y cerdo frente a la oxidación.

The use of microwaves is very widespread at the domestic level thanks to its speed and ease of use. The aim of this study was to compare cooking loss, rancidity and sensory differences for hamburger patties cooked in conventional versus microwave ovens. We also determined sensorial differences with the triangular test, comparing two products presented in threesomes, one that corresponded to a patty cooked in the microwave and the other in a conventional oven. Chicken, turkey, pork and beef patties were purchased commercially, cooked in a conventional oven and in microwaves. Cooking loss was calculated, rancidity and sensory differences were evaluated between patties of the same type of meat and cooked in the different oven types. Cooking loss was lower in patties cooked in microwaves compared to those cooked in conventional ovens. For both oven types, acidity and peroxide index increased with respect to raw ones. Acidity was higher in hamburgers cooked in conventional ovens and the peroxide index was higher in burgers cooked in microwaves, reaching 10.6 meq O2/kg. In sensory analysis, significant differences were found (p<0.05) between patties cooked in a conventional oven and in microwaves. It is a better option to cook patties in a conventional oven, because the peroxide index is smaller than in microwaves; and within types of patties, beef and pork are more stable against oxidation.

Resistência à flexão de duas resinas compostas diretas após diferentes métodos de polimerização / Flexural strength of two direct composite resins after different polymerization methods

Objetivo: avaliar a influência de diferentes modos de polimerização sobre a resistência à flexão de três pontos de duas resinas compostas. Métodos: foram confeccionadas 88 amostras, sendo divididas em dois grupos, conforme a resina composta utilizada: Filtek Z350 XT e Forma. Os grupos foram subdivididos, de acordo com diferentes modos de polimerização, em: G1- Z350 por 20s a 1.000 mw/cm²; G2- Forma por 20s a 1.000 mw/cm²; G3- Z350 por 20s a 1.000 mw/cm² e micro-ondas por 3 minutos em 450w; G4- Forma por 20s a 1.000 mw/cm² e micro-ondas por 3 minutos em 450w; G5- Z350 por 2 vezes de 3s a 3.200 mw/cm²; G6- Forma por 2 vezes de 3s a 3.200 mw/cm²; G7- Z350 por 2 vezes de 3s a 3.200 mw/cm² e micro-ondas por 3 minutos em 450w; G8- Forma por 2 vezes de 3s a 3.200 mw/cm² e micro-ondas por 3 minutos em 450w. As amostras foram submetidas ao teste de resistência à flexão de 3 pontos, sob taxa de carregamento de 50 N/min, até a falha completa. Os dados foram analisados estatisticamente por análise de variância com dois fatores (two-way ANOVA) e teste de Tukey. Resultados: não houve diferenças estatísticas entre as resinas compostas e os modos de polimerização utilizados. Conclusão: de acordo com os resultados do estudo, e dentre suas limitações, os modos de polimerização não influenciaram a resistência à flexão, independentemente da resina composta testada. (AU)

Objective: to evaluate the influence of different polymerization modes on the three-point flexural strength of two composite resins. Methods: 88 samples were produced and divided into two groups according to the composite resin used: Filtek Z350 XT and Forma. The groups were subdivided according to different polymerization modes into: G1- Z350 for 20 s at 1000 mw/cm²; G2- Forma for 20 s at 1000 mw/cm²; G3- Z350 for 20 s at 1000 mw/cm² and microwave for 3 min at 450w; G4- Forma for 20 s at 1000 mw/cm² and microwave for 3 min at 450w; G5- Z350 2x for 3 s at 3200 mw/cm²; G6- Forma 2x for 3 s at 3200 mw/cm²; G7- Z350 2x for 3 s at 3200 mw/cm² and microwave for 3 min at 450w; and G8- Forma 2x for 3 s at 3200 mw/cm² and microwave for 3 min at 450w. The samples were subjected to the three-point flexural strength test under a 50 N/min loading rate until complete failure. The data were statistically analyzed using two-way analysis of variance (two-way ANOVA) and Tukey's test. Results: there were no statistical differences between the composite resins and the polymerization modes used. Conclusion: according to the study results and within its limitations, the polymerization modes did not affect flexural strength, regardless of the composite resin tested. (AU)

Determinação de protocolo para descristalização de mel em micro-ondas / Standard to melt honey with microwaves

O presente estudo teve como objetivo obter um protocolo para descristalização do mel de forma a não alterar os parâmetros físico-químicos. Para o estudo, foram utilizadas amostras de mel que estavam cristalizadas nos locais de compra, sendo estas submetidas em micro-ondas a diferentes níveis de potência (Mínima, Média e Alta) e tempos (5, 10, 15 e 20 segundos). As amostras de mel apresentaram valores de 2,57 a 3,58 mg.kg de hidroximetilfurfural (HMF). Além da análise de HMF, foram avaliados também o teor de umidade, Teste de Fiehe, Prova de Lugol e Lund, sendo obtidos resultados dentro do preconizado na legislação brasileira. Um protocolo adequado para descristalizaçao de mel em micro-ondas foi obtido com uso de potência média e com tempo de 15 segundos.

Efeito da forma de aquecimento em parâmetros de qualidade e identidade de óleos vegetais / Effect of the heating means in quality and identity parameters of vegetable oils

Objetivou-se com este trabalho avaliar parâmetros de identidade e qualidade de óleo de abacate produzido nacionalmente, comparativamente a azeite de oliva e óleo de arroz, após aquecimento em bloco digestor ou micro-ondas. Avaliaram-se amostras sem aquecimento (controle) e aquecidas por 1:30 h em bloco digestor ou 3 min em micro-ondas. Determinaram-se a acidez e os índices iodo e refração. Os resultados indicaram que houve aumento de acidez, redução no índice de iodo e índice de refração após o aquecimento. Apesar do maior valor de acidez após o aquecimento, o óleo de abacate sofreu menor elevação em relação ao controle (cerca de 4 vezes) do que as demais amostras. O impacto do aquecimento foi maior no óleo de arroz, seguido do azeite de oliva. O aquecimento por micro-ondas afetou mais a qualidade das amostras que o aquecimento em bloco digestor.

Estabilidade térmica de pigmentos em óleo de abacate, arroz e azeite de oliva / Thermal stability of pigments in avocado, rice and olive oil

Sabe-se que o aquecimento do óleo pode alterar sua composição, degradando ácidos graxos e compostos minoritários. Assim, objetivou-se avaliar a estabilidade térmica dos pigmentos carotenoides e clorofilas no óleo de abacate produzido nacionalmente, em comparação com óleo de arroz e azeite de oliva após aquecimento a 180 ºC em micro-ondas, por 3, 6, 9 e 12 minutos. Observaram-se diferenças significativas entre as amostras em todos os tempos de análise, tanto para clorofilas quanto para carotenoides. Na avaliação ao longo do tempo de aquecimento somente foi verificada alteração significativa no teor de clorofilas do azeite de oliva, ainda que no óleo de abacate os percentuais de perda tenham sido maiores. Verificou-se que os teores dos pigmentos avaliados foram significativamente maiores no óleo de abacate em relação ao azeite de oliva e o óleo de arroz, mesmo após o aquecimento por 12 minutos. Destaca-se a importância destas informações para estimular o consumo do óleo de abacate.

Guarda oclusal gnatológica: técnica de elaboración, procesado y polimerizado por microondas / Gnathological occlusal guard: technique of elaboration, processing and polymerization by microwaves

Los trastornos temporomandibulares (TTM) constituyen un problema en la población en general cuyos signos y síntomas tienen un carácter multifactorial que debe ser abordado de manera interdisciplinaria para poder brindar una mejor oportunidad de éxito y estética en los tratamientos. Las guardas oclusales forman parte del tratamiento en los TTM, se deben conocer sus indicaciones, contraindicaciones, ventajas y desventajas, debido a que las guardas oclusales cumplen ciertas funciones y objetivos. La guarda oclusal elaborada por la técnica de polimerización en microondas (GOTMI) reduce signifi cativamente el tiempo de elaboración en el laboratorio, proporciona un aparato de alta calidad y baja porosidad. La GOTMI es un aparato que proporciona un método indirecto y no invasivo modifi cando la oclusión, recuperando el tejido u órganos dentales perdidos, reorganiza la actividad refl eja neuromuscular, relaja la musculatura, promueve el reposicionamiento del disco articular, protege los dientes, oclusión y estructuras de sostén periodontal, además de mejorar la estética y la autoestima del paciente. La GOTMI disminuye el dolor en la ATM y la neuromusculatura, proporciona alivio a las cefaleas tensionales, elimina las interferencias oclusales, es un distribuidor de fuerzas oclusales, además de provocar un mayor número de contactos de igual intensidad de fuerza contra la superfi cie oclusal en todos los dientes. Existen varios métodos para la confección de las guardas oclusales, en el presente trabajo se describe la elaboración de una guarda oclusal programada con los principios de oclusión orgánica. La técnica de polimerización por microondas es innovadora debido a que este proceso consiste en la generación de calor dentro de la resina mediante ondas electromagnéticas producidas por un generador llamado magnetrón. Las moléculas de metilmetacrilato son capaces de orientarse por el campo electromagnético a una frecuencia de 2,450 MHz, y cambian su dirección cinco billones de veces por segundo aproximadamente, lo que implica numerosas colisiones intermoleculares y causa una rápida polimerización (AU)

Temporomandibular disorders (TMD) are a problem in the general population whose signs and symptoms have a multifactorial character that must be addressed by an interdisciplinary team to provide a better chance of success and aesthetic treatments. Occlusal guards are part of TMD treatment, you should know the indications, contraindications, advantages, and disadvantages, because the occlusal guards perform certain functions and objectives. The occlusal guard by Iztacala modifi cation provides an indirect and noninvasive method modifying occlusion, recovering the lost dental tissue or organs, reorganizes the neuromuscular refl ex activity, relaxes the muscles, promotes articular disc repositioning, protecting the teeth and supporting occlusion structures, it also improves aesthetics and self-esteem. The occlusal guard Iztacala modifi cation has the advantage of decreasing TMJ pain, provides relief to tension headaches, elimination of occlusal interferences, is a distributor of occlusal forces as well as causing a greater number of contacts equal intensity of force against the occlusal surface of all teeth. There are several methods for the fabrication of occlusal guards, in this paper the development of an occlusal guard programmed with the principles of organic occlusion is described, using as a basis a rigid acetate and acrylic for programming, in addition to providing your cosmetic use and function. The acquisition or denial of treatment with an occlusal splint depends on the choice, preparation, occlusal guard adjustment and patient cooperation (AU)

Larvicidal effect of Clinopodium macrostemum essential oil extracted by microwave-assisted hydrodistillation against Culex quinquefasciatus (Diptera: Culicidae)

Abstract INTRODUCTION: In the present study, we determined the chemical composition of Clinopodium macrostemum essential oil obtained by microwave-assisted hydrodistillation and its effect on the growth and development of Culex quinquefasciatus mosquito larvae. METHODS: The essential oil compounds were identified by gas chromatography-mass spectrometry analysis, and bioassays were conducted to evaluate the influence on the developmental stages of early second instar larvae of Cx. quinquefasciatus until the emergence of adults, using essential oil concentrations of 50, 100, 200, 400, and 800mg/L. RESULTS: The gas chromatography-mass spectrometry analyses revealed that the leaf essential oil of C. macrostemum contained 32 compounds and the major chemical compounds identified were linalool (55.4%), nerol (6.4%), caryophyllene (6.25%), menthone (5.8%), geraniol acetate (4.1%), terpineol (3.7%), and pulegone (2.8%). The essential oil yield obtained by microwave-assisted hydrodistillation was 0.8% at 20 min. The treatments showed lethal concentrations (LC50 and LC90) of 22.49 and 833.35mg/L, respectively, after the final measurement of the total number of dead larvae (second, third, and fourth instars), and LC50 and LC90 of 6.62 and 693.35mg/L, respectively, at the end of the experimental period. The essential oil inhibited the growth and development of the mosquito larvae by 32% (relative growth index = 0.68) at 50mg/L, and up to 47% (relative growth index = 0.53) at 800mg/L. CONCLUSION: The present study demonstrated the larvicidal effect of C. macrostemum essential oil on Cx. quinquefasciatus, which can be attributed to the oxygenate compounds obtained by the extraction method.

O efeito do envelhecimento por fadiga na microestrutura de cerâmicas y-tzp sinterizadas por energia de micro-ondas / The effect of fatigue aging on the microstructure of y-tzp ceramics sintered by microwave energy

O objetivo deste trabalho foi avaliar o efeito da fadiga na microestrutura de uma cerâmica odontológica (Y-TZP) sinterizada pelo método convencional ou por energia de micro-ondas. A hipótese nula foi que a fadiga não irá gerar alterações na microestrutura deste material. Para isto, foram confeccionados, por meio de um sistema CAD/CAM, 84 discos de zircônia (VIPI block zircon) com características finais de 12 mm de diâmetro e 1,2 mm de espessura conforme a norma ISO 6872. Os espécimes foram separados em dois grupos: Grupo I ­ Sinterização convencional: ciclo estabelecido pelo fabricante (2 horas a 1530 °C) e Grupo II ­ sinterização por energia de micro-ondas (15 min a 1450 °C). Dez amostras por grupo foram submetidas ao teste monotônico (1000 KgF ­ 1mm/min) para a determinação da carga para fratura, utilizada como parâmetro para os testes de fadiga (método step-stress e fadiga dinâmica). O teste de fadiga step-stress foi realizado utilizando 4 perfis de carga, ultra-suave, suave, moderado e agressivo, até que ocorresse a fratura. A fadiga dinâmica foi realizada com o ensaio dos discos até fratura sob cinco taxas de tensão (1, 0,1, 0,01, 0,001 e 0,0001 MPa/s), e a partir disso foram calculados o coeficiente de crescimento de trincas e módulo de Weibull (confiabilidade) para cada grupo. Foram realizadas análises complementares de densidade, translucidez, microscopia eletrônica de varredura (MEV) e difratometria de Raios-X (DRX) de ambos os grupos para a caracterização dos materiais. Os resultados da fadiga step-stress não mostraram diferenças no comportamento dos espécimes de cada grupo. Na fadiga dinâmica, os métodos de fadiga também não mostraram diferenças no comportamento e tiveram coeficientes de crescimento de trinca similares. O modulo de Weibull mostrou maiores valores de confiabilidade para o grupo micro-ondas (m = 7,9) do que para o grupo de sinterização convencional (m = 6,7). Os valores de densidade também foram semelhantes para os grupos estudados, já a translucidez foi menor para o grupo micro-ondas. As imagens de MEV mostraram microestruturas similares entre grupos, apenas uma diferença no tamanho dos grãos foi observada, 0,53 µm para os grãos de microondas e 0,89 µm para os grãos dos espécimes sinterizados convencionalmente. Conclui-se que o processo de sinterização por microondas pode ser aplicado como alternativa de sinterização de zirconia ao dia-a dia laboratorial(AU)

The objective of this work was to evaluate the microstructure and fatigue behavior of a dental ceramic (Y-TZP) sintered by conventional method or by microwave energy. The null hypothesis was that the fatigue will not effect the microstructure of this material. 84 zirconia discs (VIPI block zircon) with final characteristics of 12 mm in diameter and 1.2 mm in thickness according to ISO 6872 were made using a CAD/CAM system. The specimens were divided in two groups: Group I - Conventional sintering: cycle established by the manufacturer (2 hours at 1530 °C) and Group II - sintering by microwave energy (15 min at 1450 °C). Ten samples per group were submitted to monotonic test (1000 KgF - 1mm/min) to determine the load to fracture, used as a parameter for fatigue tests (step-stress and dynamic fatigue). The step-stress fatigue test was performed using 4 load profiles, ultramild, mild, moderate and aggressive, until the fracture. The dynamic fatigue was performed by testing the disks to fracture under five constant stress rates (1, 0.1, 0.01, 0.001 and 0.0001 MPa/s), and from this the crack growth coefficient and Weibull module (reliability) were measured for each group. Additional analyzes of density, translucency, scanning electron microscopy (SEM) and X-ray diffractometry (XRD) for both groups were carried out to characterize the materials. The results of stepstress fatigue test did not show differences in the specimens behavior of each group. Dynamic fatigue also showed no differences in behavior and had similar crack growth coefficients. The Weibull modulus showed higher reliability values for the microwave group (m = 7.9) than for the conventional sintering group (m = 6.7). The density values were also similar for the studied groups, since the translucency was lower for the microwave group. SEM images showed similar microstructures between groups, only a difference in grain size was observed, 0.53 µm for microwave grains and 0.89 µm for the conventionally-sintered grains. It is concluded that the microwave sintering process can be applied as an alternative to zirconia sintering to daily laboratory work(AU)

Influence of preheating and post-curing on a novel fiber-reinforced composite post material

Abstract The aim of this study was to investigate the influence of preheating and post-curing methods on diametral tensile strength (DTS), flexural strength (FS), knoop microhardness (KHN), and degree of conversion (DC) of an experimental fiber-reinforced composite (FRC). Specimens (30 wt% of 3-mm-short E-glass fiber, 22.5 wt% of methacrylated-based resin and 47.5 wt% of filler particles) were subjected to: P - photocuring at 1500 mW/cm2 for 40 s (control); P/M - photocuring and microwave post-curing (540W/5 minutes); P/A - photocuring and autoclave post-curing (120°C/15 minutes); PH-P - preheating (60°C) and photocuring; PH-P/M - preheating, photocuring and microwave post-curing; and PH-P/A - preheating, photocuring and autoclave post-curing. Specimens for DTS (Ø 3 x 6 mm) and FS (25 x 2 x 2 mm) were tested at Instron 5965. KHN employed a 50g load for 30s. DC was measured using FTIR spectroscopy. Statistical analysis employed: factorial analysis, normality test, one-way ANOVA and Tukey's HSD test, independent T-test and the Dunnett test. Interaction between factors was not significant (P>0.05). Preheating promoted significantly higher values of FS and KHN (p = 0.0001). Post-curing promoted significantly higher values for KHN (p = 0.0001). For DTS (p = 0.066) and DC (p= 0.724) no statistical difference was found between groups. SEM images showed that preheating promoted better interaction between glass fibers and resin matrix. Preheating increased FS, KHN and DTS, and post-curing increased KHN. DC was not affected by both methods. Preheating and post-curing methods can be used to improve some mechanical properties of FRCs' but degree of conversion remains unaffected.

Long-term microwaving of denture base materials: effects on dimensional, color and translucency stability

Abstract While the combined effect of microwave irradiation with cleansing solutions on denture base materials has been investigated, the effects of only using microwave irradiation and, more importantly, in a long-term basis, was not studied yet. Objective The purpose of this study was to evaluate the effect of a long-term repeated microwaving on the dimensional, color and translucency stability of acrylic and polyamide denture base materials. Material and Methods Thirty two specimens (32 mm x 10 mm x 2.5 mm) from polyamide (Valplast) and PMMA (Vertex Rapid Simplified) denture base materials were made. Eight specimens from each material were immersed in distilled water (control) and 8 were subjected to microwave exposure at 450 W for 3 minutes for a period simulating 224 days of daily disinfection. Linear dimension, color change (ΔE*) and translucency parameter (TP) were measured at baseline and after certain intervals up to 224 cycles of immersion, using a digital calliper and a portable colorimeter. The results were analysed using two-way repeated measures ANOVA to estimate possible differences among predetermined cycles and material type. Regression analysis was also performed to estimate the trend of changes with time. Statistical evaluations performed at a significance level of 5%. Results Data analysis showed significant changes in length at baseline with an increasing number of cycles (p<0.05) and a significant interaction of cycle-material (p<0.001). The ΔΕ* parameter was significantly higher with a higher number of cycles (p<0.001), but it did not vary between materials (p>0.05). TP decreased similarly in both materials following microwave action but in a significantly higher level for Valplast (p<0.001). Conclusions The results indicated that long-term repeated microwaving affects linear dimensional, color and translucency changes of both materials. Differences between PMMA and polyamide material were noted only in dimension and translucency changes.

Porosity, water sorption and solubility of denture base acrylic resins polymerized conventionally or in microwave

Abstract The proper selection of polymerization cycle is important to prevent overheating of the monomer that could cause degradation, porosity and, consequently, deleterious effects on the denture base properties. Objective This study evaluated the porosity, water sorption and solubility of acrylic resins (Vipi Cril-VC and Vipi Wave-VW) after conventional or microwave polymerization cycles. Material and Methods Specimens (n = 10) were made and cured: 1-WB = 65°C during 90 min + boiling during 90 min (VC cycle - control group); 2-M25 = 10 min at 270 W + 5 min at 0 W + 10 min at 360 W (VW cycle); 3-M3 = 3 min at 550 W; and 4-M5 = 5 min at 650 W. Afterward, they were polished and dried in a dessicator until a constant mass was reached. Specimens were then immersed in distilled water at 37°C and weighed regularly until a constant mass was achieved. For porosity, an additional weight was made with the specimen immediately immersed in distilled water. For water sorption and solubility, the specimens were dried again until equilibrium was reached. Data were submitted to 2 way-ANOVA and Tukey HSD (α=0.05). Results Porosity mean values below 1.52% with no significant difference among groups for both materials were observed. Resins showed water sorption and solubility values without a significant difference. However, there was a significant difference among groups for these both properties (P<0.013). The highest sorption (2.43%) and solubility (0.13%) values were obtained for WB and M3, respectively. Conclusions The conventional acrylic resin could be polymerized in a microwave since both the materials showed similar performance in the evaluated properties. Shorter microwave cycles could be used for both the materials without any detectable increase in volume porosity.

Crystal Modification on Lithium Disilicate Glass Ceramics Sintered Using Microwaves / Modificación de Cristales de Cerémicas de Vidrio de Disilicato de Litio Sinterizadas con Microondas

ABSTRACT: Microwaves are an interesting alternative to process dental ceramics. It is well documented that Microwave Hybrid Sintering (MHS) allows important savings in time and energy consumption. However, little is known about its effect on lithium disilicate glass ceramics, a popular material in dentistry today. We analyzed the microstructure of lithium disilicate glass ceramics sintered with MHS compared with conventional sintering. We sintered lithium disilicate glass ceramics using MHS and conventional furnaces, and we analyzed the samples using X-Ray diffraction and SEM. Samples sintered with MHS showed an increased crystalline phase, with an increased number of crystals. These crystals have larger perimeters compared with samples sintered in conventional furnaces. MHS produced a different crystallization pattern and crystal/ matrix ration in lithium disilicate glass ceramics when compared to conventional sintering. This can be associated with the improved mechanical properties of these materials reported previously.

RESUMEN: Las microondas son una interesante alternativa para procesar cerámicas dentales. Está bien documentado que el Sinterizado Híbrido por Microondas (MHS) permite ahorros importantes de tiempo y energía. Sin embargo, poco se ha publicado respecto a sus efectos en cerámicas de disilicato de litio, un material bastante popular en odontología en estos días. En este artículo analizamos la micro estructura de cerámicas de disilicato de litio sinterizada con MHS comparada con el sinterizado convencional. Sinterizamos muestras de cerámicas de disilicato de litio usando MHS y hornos convencionales, y analizamos las muestras usando difracción de rayos X y SEM. Las muestras sintetizadas usando MHS tienen una mayor fase cristalina, con mayor número de cristales. Estos cristales tienen además perímetros mayores, comparados con las muestras sinterizadas en hornos convencionales. MHS produce patrones de cristalización y proporción de cristal/matrix diferentes a las producidos por sinterizado convencional. Esto puede asociarse a las mejoras en propiedades mecánicas reportadas previamente.

Tirosina, substrato em reações de acoplamento cruzado: síntese de dipeptídeos Tyr-Tyr, heterociclos e investigação da atividade biollógica contra células cancerígenas e parasitárias / Tyrosine, a building block in cross-coupling reactions: synthesis of dipeptides Tyr-Tyr, heterocycles and biological activity investigations against cancer cells and parasidic cells

Tirosina, um aminoácido proteinogênico, de fundamental importância para nossa sobrevivência, foi objeto de estudo para a confecção da presente tese. Investigado frente às três reações de acoplamento cruzado mais exploradas nos últimos anos, Suzuki-Miyaura, Heck e Sonogashira, a 3-iodotirosina comportou-se como um excelente substrato na formação de unidades biarílicas, derivados estilbeno, formação de heterociclos do tipo 1,2,3-triazóis, quinolinas, benzofuranos e flavonas, bem como a formação de dipeptídeos Tyr-Tyr. A reação entre a 3-iodotirosina com diferentes nucleófilos de boro via reação de Suzuki- Miyaura, além de dar origem às unidades biarílicas, forneceu derivados do estilbeno, usados como substratos na construção de quinolinas, alcançadas por meio da reação multicomponente de Povarov, com catálise de prata em apenas 40 minutos sob irradiação de micro-ondas. Alguns desses derivados estilbeno, apresentaram ainda uma acentuada fluorescência, a qual foi medida em diferentes polaridades. Ao explorarmos a reação entre a 3-iodotirosina e acetilenos, derivados alquinílicos puderam ser convenientemente preparados, permitindo seu uso como materiais de partida na reação de cicloadição de Huisgen, no preparo de anéis triazólicos. Produtos provenientes da adição estereosseletiva de oxa-Michael, entre o anel fenólico da tirosina e aldeídos propargílicos, forneceram compostos carbonílicos α,ß-insaturados capazes de reagirem via acoplamento intramolecular de Heck, levando a derivados 2-aril-3- formil-5-alanilbenzofuranos ou ainda, apenas alterando a atmosfera inerte de nitrogênio por monóxido de carbono, a formação de 2-aril-6-alanilflavonas via acilação intramolecular redutiva. Além da metodologia de síntese explorada na tese, alguns dos compostos obtidos apresentaram atividade biológica seletiva contra células de melanoma e leucemia, bem como atividade antiparasitária frente ao Plasmodium falciparum, não afetando a proliferação de células sadias. Dessa forma, os resultados apresentados, agregam ainda mais valor sintético e biológico ao aminoácido tirosina, explorados de forma inédita

Tyrosine, a proteinogenic amino acid of fundamental importance for life, was the object of study for the research that is presented in this thesis. When 3-iodotyrosine was used in the three different types of cross-coupling reactions that have been exploited the most in recent years, namely the Suzuki-Miyaura, Heck and Sonogashira coupling reactions, 3-iodotyrosine as an excellent substrate for the formation of biaryl units, stilbene derivatives, 1,2,3-triazoletype heterocycles, quinolines, benzofurans and flavones, and Tyr-Tyr dipeptides. This work is organized into sections in order to facilitate ease of reading. The reaction between 3-iodotyrosine and different boron nucleophiles via the Suzuki- Miyaura coupling reaction, in addition to giving the biaryl units, also provided stilbene derivatives, which were used as substrates for the construction of quinolines via multicomponent Povarov reactions. The Povarov was performed with silver catalysis under 40 minutes of microwave irradiation. Some of these stilbene derivatives showed a marked fluorescence, which was measured in solvents with different polarities. By exploring the Sonogashira coupling reaction between 3-iodotyrosine and acetylenes, alkynyl derivatives could be conveniently prepared, which in turn could be used as starting materials in Huisgen cycloaddition reactions to synthesize1,2,3-triazole rings. Products from the stereoselective addition of oxa-Michael, between the phenolic ring of tyrosine and propargyl aldehydes, provided 945;,946;-unsaturated carbonyl compounds capable of reacting via Heck intramolecular coupling, leading to 2-aryl-3-formyl-5-alanylbenzofurans or by simply changing the inert atmosphere of nitrogen by carbon monoxide, the formation of 2- aryl-6-alanylflavones via reductive intramolecular acylation. In addition to the synthesis methodology explored in the thesis, some of the compounds showed selective biological activity against melanoma and leukemia cells, as well as antiparasitic activity against Plasmodium falciparum, without affecting the proliferation of healthy cells. In this way, the presented results add even more synthetic and biological value to the amino acid tyrosine, explored in an unprecedented way

Efeito da radiação por micro-ondas na inativação de cepas de escherichia coli / Effect of microwave radiation on the inactivation of strains of Escherichia coli

Entre as bactérias patogênicas vinculadas a doenças transmitidas por alimentos destaca-se a Escherichia coli, sendo a espécie predominante na microbiota do trato intestinal dos humanos e animais de sangue quente e que está associada diretamente com a má higienização dos manipuladores. Com a necessidade de aplicar processos inovadores sem a geração de resíduos, o desenvolvimento de novas tecnologias para o controle e redução de carga microbiana nos alimentos vem sendo estudado, destacando-se a irradiação por micro-ondas. Com a intenção de testar o efeito bactericida de um forno micro-ondas (2450 MHz) sob cepas de E. coli, diferentes tempos de irradiação foram utilizados, sendo estes 5, 10, 15, 20, 30, 40 e 60s tendo como controle, uma amostra não irradiada. Ainda, imagens termográficas e mapeamento do forno foram realizados para verificar a distribuição da temperatura das amostras irradiadas, demonstrando a heterogeneidade da incidência das ondas no interior da cavidade do mesmo. Após a realização dos testes, verificou-se que em 20s de irradiação, as cepas de Escherichia coli foram inativadas, demonstrando a relevância do método para a ciência e tecnologia dos alimentos uma vez que o processo mostrou-se eficaz no controle microbiano, de fácil operação, sem a geração de resíduos, rápido e econômico, quando comparado aos métodos convencionais de inativação e destruição microbiana.

Among the pathogenic bacteria transmitted to foodborne illness there is the Escherichia coli, being the predominant species in the microflora of the intestinal tract of humans and warm-blooded animals and is directly associated with poor hygiene of food handlers. With the need to apply innovative processes without waste generation, the development of new technologies for the control and reduction of microbial load in food has been studied, highlighting irradiation by microwave. With the intention of testing the bactericidal effect of a microwave oven (2450 MHz) as strains of E. coli different irradiation times were used, these being 5, 10, 15, 20, 30, 40 and 60 as having s control, a sample not irradiated. Further, thermographic images and oven mapping were performed to verify the temperature distribution of the irradiated samples, demonstrating the heterogeneity of incidence of the waves within the cavity thereof. After the tests, it was found that in 20 seconds irradiation, strains of Escherichia coli were inactivated, demonstrating the relevance of the method for science and technology of food once the process has been shown to be effective in microbial control, easy operation with no waste generation, quickly and cost when compared to conventional methods of microbial inactivation and destruction.

Fatty acid composition, antioxidant and antibacterial properties of the microwave aqueous extract of three varieties of Labisia pumila Benth

BACKGROUND: The present study was conducted in order to evaluate the fatty acid profile, anti-oxidant and anti-bacterial activities from the microwave aqueous extract of the leaves of three different varieties of Labisia pumila Benth. RESULTS: The chemical analysis of the extract showed that fatty acids (palmitic, palmitoleic, stearic, oleic, linoleic and α-linolenic) acid as the main components in three varieties of L. pumila leaves. Furthermore, the obtained results of the anti-oxidant revealed that L. pumila var. alata contained higher anti-oxidative activities compared to var. pumila and var. lanceolata. However, these values were lower than the tested anti-oxidant standards. On the other hand, the aqueous leaf extracts in all three varieties of L. pumila were also found to inhibit a variable degree of antibacterial activities against eight bacteria (four Gram-positive and four Gram-negative bacteria). CONCLUSIONS: In this study, it was observed the leaves of three varieties of L. pumila exhibited variable patterns of fatty acids and the microwave aqueous extraction possess anti-oxidant and anti-bacterial activities.

Determinación de humedad en harina precocida de maíz blanco utilizando un horno de microondas doméstico / Determination of moisture in flour precooked white corn using a domestic microwave oven

El contenido de humedad es un parámetro de principal interés entre los índices que regulan la calidad de granos, cereales y sus derivados. Los métodos oficiales para determinar la humedad (AOAC 32.1.03, ISO 6540:1980, NTC 2227:86 y COVENIN 2135:96) tienen la desventaja de consumir mucho tiempo en la determinación porque  requieren la desecación de la muestra en estufa. En este trabajo se compara el método propuesto de secado de la muestra de maíz blanco en un horno doméstico de microondas contra el método rápido convencional de termobalanza infrarrojo y los métodos de referencia oficiales AOAC (32.1.03) y COVENIN (2135:96). Se determinaron las condiciones de análisis: tamaño de muestra, tipo de recipiente, distribución de la muestra, condiciones de operación usando un microondas doméstico de 700 W de potencia, así como el secado en uno o varios pasos. Entre el método propuesto y el método de referencia no se encontraron diferencias estadísticamente significativas a p<0,05; el tiempo de secado se redujo de varias horas a pocos minutos: 4 min con 90% de potencia. Como se puede  concluir que es factible la determinación de humedad por volatilización en una matriz de harina precocida de maíz blanco usando un horno de microondas doméstico.

The moisture content is a primary parameter between indices governing the quality of grains, cereals and cereal products. The official methods for determining moisture (AOAC 32.1.03, ISO 6540: 1980, NTC 2227: 86 COVENIN 2135: 96) have the disadvantage of to be time consuming that require drying oven method. The aim in this paper was compare the proposed method of drying sample of white corn with domestic microwave oven against conventional rapid method of infrared thermobalance and official reference methods AOAC 32.1.03 method and COVENIN 2135:96. Sample size, vessel kind, sample container distribution,   operations conditions using domestic 700 W microwave and also analysis employed to one or more drying steps were determined. Between the proposed and the reference method not statistically significant differences were found at P <0.05; drying time was reduced from several hours to a few minutes: 4 min at 90% power. It can be concluded that the determination of moisture by volatilization in a matrix of precooked white corn flour using a domestic microwave oven is feasible.