Abstract This study investigates the disposition effect with regard to Brazilian investors, with focus on the year 2020. The database is composed by more than 12,000 trades by 274 investors. We follow the method of Odean (1998) to estimate the proportions of gains and losses realized and test the null hypothesis of equality of these proportions in each portfolio. The results suggest that Brazilian investors behave in line with the disposition effect. They sell winning stocks too early and hold losing stocks too long. A stock that is gaining value is more likely to be sold from day to day compared to a stock that is losing value. The disposition effect was not found in March, which suggests that investors employed a loss-limit during periods of market stress, no matter if the stock went up or down.

Resumo Este trabalho investiga a presença do efeito disposição em investidores brasileiros no ano de 2020. A base de dados compreende 274 investidores distintos que, em conjunto, realizaram mais de 12 mil transações. Aplica-se a metodologia utilizada por Odean (1998). A partir das carteiras de investimento de cada indivíduo, estima-se a proporção de ganhos e de perdas realizadas e testa-se a hipótese de igualdade dessas proporções. O estudo identificou que os investidores brasileiros estão propícios à influência dessa anomalia comportamental nas suas decisões, ou seja, vendem seus investimentos com ganhos mais rapidamente e mantêm seus investimentos perdedores por mais tempo e que uma posição com lucro possui mais chance de ser vendida do que uma posição com prejuízo. Os resultados não indicam efeito disposição no mês de março, e isso sugere que, em momentos de maior incerteza, investidores buscam limitar perdas, independentemente do lucro ou prejuízo auferido com o ativo.

Resumo O objetivo deste trabalho foi determinar as condições ideais para o processamento da farinha e a extração de antocianinas de mirtilos (Vaccinium corymbosum). Utilizou-se um delineamento composto central (DCC) com superfícies de resposta. Para o processamento da farinha de mirtilo, utilizaram-se diferentes temperaturas (53ºC-67ºC) e tempos (43,18-48,82 horas) de desidratação. A extração de antocianinas foi feita com soluções de etanol (15-85% v/v) com diferentes valores de pH (1,0-4,0). O teor de antocianinas monoméricas totais foi de 1.538,39±25,63 mg 100 g-1 (valor de desejabilidade de 0,89) para mirtilos frescos, na condição ótima de extração (53,5% etanol, pH 2,5), e de 3.101,04±11,57 mg 100 g-1 (valor de desejabilidade de 0,96) para farinha de mirtilo, na condição ótima de processamento (53ºC, 46 horas). A extração e a desidratação otimizadas dos mirtilos proporcionam a obtenção de altos teores de antocianinas nas amostras.

Abstract The objective of this work was to determine the ideal conditions for the processing of flour and extraction of anthocyanins from blueberries (Vaccinium corymbosum). A central composite design (CCD) with response surfaces was used. For the processing of blueberry flour, different dehydration temperatures (53ºC-67ºC) and times (43.18-48.82 hours) were used. The extraction of anthocyanins was performed with ethanol solutions (15-85% v/v) at different pH values (1.0-4.0). ). The total monomeric anthocyanin content was 1,538.39±25.63 mg 100 g-1 (0.89 desirability value) for fresh blueberries in the optimal extraction condition (53.5% ethanol, 2.5 pH) and 3,101.04±11.57 mg 100 g-1 (0.96 desirability value) for blueberry flour in the optimum processing condition (53ºC, 46 hours). The optimized extraction and dehydration of blueberries provide high levels of anthocyanins in the samples.

The brewing waste, also known as trub, is an abundant by-product of the brewing industry. Such material presents high levels of phenolic compounds, which promote antioxidant, antimicrobial and antifungal effects, turning the trub economically attractive. In this study, the trub’s phenolic compounds were extracted by ultrasound-assisted extraction technology. Such experiments were conducted according to a central composite rotatable design (CCRD), with the evaluated parameters being ethanol concentration, solid-liquid ratio and extraction temperature. Response surface methodology (RSM) described the effect of process’ variables through second order polynomial models, adjusted appropriately for such analysis, and optimized the operating conditions, aiming to obtain the maximum extraction of phenolic compounds through the proposed technique. The extraction’s optimal conditions for the evaluated variables were ethanol concentration of 58%, solid-liquid ratio of 1 g per 32 mL, and extraction temperature of 36 ºC, during a 30 minute process. Considering such experimental conditions, the total amount of phenolic compounds was equal to 7.23 mg of gallic acid g-1 trub, indicating that a great concentration of phenolic compounds can be extracted from this material through the proposed technique. Thus, this indicates that trub might be a promising by-product that can be used in different industrial fields.

Abstract Nanoparticles demonstrate an important role in the protection of bioactive compounds from external factors such as temperature, oxygen and light. In this study, poly-ε-caprolactone (PCL) nanoparticles entrapped β-carotene was produced using the nanoprecipitation method. Firstly, was evaluated the lipophilic surfactant effect and carrier agent of the active compound in the nanocapsules formulation. After choosing the most stable formulation, the nanocapsules production was optimized using β-carotene, caprylic/capric triglycerides (CCT) and soybean lecithin. Response surface methodology (RSM) was adopted to evaluate the influence of soy lecithin concentration, volume of CCT and β-carotene concentration in the particle size, zeta potential, polydispersity index (PDI), encapsulation efficiency and recovery. Formulations containing soy lecithin and CCT demonstrated better stability comparing to the other formulations tested. The nanoparticle formulations presented an optimized particle size below 200 nm, PDI lower than 0.1 and encapsulation efficiency above 95%. Based on the results obtained, the optimum conditions to prepare PCL nanocapsules were 0.2160 mg/mL of β-carotene, 232.42 μL of CCT and 2.59 mg/mL of soy lecithin, suggesting an applicability to promote controlled released of β-carotene in food system.

Resumo Objetivo: Determinar a prevalência de fatores predisponentes de baixa acuidade visual entre os alunos do Colégio Universitário Geraldo Reis em Niterói-RJ. Métodos: Trata-se de um estudo observacional transversal realizados em duas etapas. A primeira realizou-se a medida da acuidade visual dos alunos voluntários que aderiram ao termo de assentimento. Na segunda etapa foram selecionados aqueles alunos cuja acuidade visual não ultrapassaram 0,8 em pelo menos um dos olhos ou que apresentaram diferença de acuidade visual entre os olhos de duas linhas ou mais na tabela de Snellen, sendo encaminhados para avaliação oftalmológica completa no Serviço de Oftalmologia do Hospital Universitário Antônio Pedro / Universidade Federal Fluminense. Resultados: Do total de 325 alunos matriculados, 134 (41,2%) participaram da primeira etapa do estudo e, destes, apenas 39 (29%) apresentaram baixa visão. Dos 39 alunos selecionados para a segunda etapa do estudo, apenas 14 (36%) se voluntariaram a prosseguir para avaliação oftalmológica completa, tendo as ametropias (57,14%), a ambliopia (21,42%) e o estrabismo (14,28%) como as principais causas de baixa visual identificadas. Conclusão: A prevalência de baixa visão(low vision=baixa visão tem definição, não se chama baixa visual) para essa comunidade foi de 29% e as principais causas identificadas foram as ametropias, as ambliopias e o estrabismo. Campanhas de conscientização e os problemas de adesão aos programas de triagem devem ser considerados em novos estudos.

Abstract Purpose: To determine the prevalence of predisposing factors of low visual acuity among the students of the Geraldo Reis University College in Niterói-RJ. Methods: This was a cross-sectional observational study during which the visual acuity of the volunteer students who adhered to the assent term was measured. Those students whose visual acuity did not exceed 0.8 in at least one eye or who presented a difference between the eyes of two lines or more in the Snellen table were selected for the next stage of the study and were referred for complete ophthalmologic evaluation in the Service of Ophthalmology of the Antônio Pedro University Hospital / Fluminense Federal University. Results: Of the total of 325 students enrolled, 134 (41.2%) participated in the first stage of the study and of these, only 39 (29%) presented visual impairment. Of the 39 students selected for the second phase of the study, only 14 (36%) volunteered to proceed for a complete ophthalmologic evaluation, with ametropias (57.14%), amblyopia (21.42%) and strabismus (14, 28%) as the main causes of visual impairment identified. Conclusion: The prevalence of visual impairment for this community was 29% and the main causes identified were ametropias, amblyopia and strabismus. Awareness campaigns and problems of adherence to screening programs should be considered in new studies.

Suspensions of poly ε-caprolactone (PCL) nanoparticles loaded with thyme essential oil were prepared as a natural antioxidant in mayonnaise. Mean particle size was 204.9 ± 2.7 and 240.0 ± 5.5 nm respectively for nanoparticles prepared with PCL alone (NP-C) and for those loaded with thyme essential oil (NP-T). The polydispersity index indicated a homogeneous distribution of all particles, with no significant difference between NP-C and NP-T samples. The nanoparticles showed a large negative charge evidenced by zeta potential rates, indicating high physical stability. The use of PCL as a polymer provided high encapsulation efficiency for thyme essential oil (91.15 ± 2.12 %). DPPH (2,2-diphenyl-1-picrylhydrazyl) method determined IC50 rates were 476.4 ± 33.6 and 483.5 ± 20.4 µg mL-1respectively for unencapsulated oil and for NP-T, evidencing pronounced antioxidant activity. NP-C, NP-T and synthetic antioxidant butylhydroxytoluene (BHT) were applied to samples of mayonnaise and their oxidative stability evaluated for eight days in an oven at 63 ± 3ºC. Results of hydroperoxide value (HP) and thiobarbituric acid reactive substances (TBARS) showed that NP-T had a similar performance as synthetic antioxidant BHT in the prevention of mayonnaise lipid oxidation.

RESUMEN Antecedentes: los β-glucanos (1-3: 1-4) son fibras solubles aplicadas a los alimentos debido a sus propiedades tecnológicas (capacidad de retención de agua, viscosidad, emulsificación y estabilización) y a sus efectos beneficiosos en la salud. Las propiedades funcionales de los β-glucanos pueden perderse durante los procesos de extracción y purificación. La alta viscosidad de los β-glucanos está relacionada con un alto peso molecular y con sus propiedades fisiológicas en el intestino. Por lo tanto, caracterizar la fibra después de su extracción y purificación es fundamental para comprender sus posibles aplicaciones en alimentos. Objetivos: caracterizar β-glucanos extraídos (EβG) y compararlos con tres marcas comerciales (CβG-A, CβG-B y CβG-C) para identificar su futura aplicación en alimentos y evaluar si la purificación enzimática afecta molecular y estructuralmente los β-glucanos. Métodos: se extrajeron β-glucanos de cebada (EβG), caracterizados por análisis químicos, comportamiento reológico y color, y se compararon con tres muestras comerciales. Posteriormente, el extracto (EβG) se purificó y se identificaron sus características estructurales y su peso molecular. Resultados: EβG contenía 64.38 ± 3.54% de β-glucanos, alta contaminación con almidón (12.70 ± 1.73%), alto contenido de calcio (8894 mg / kg), comportamiento pseudoplástico y color oscuro (L* = 52.77 ± 0.7). Todas las muestras comerciales mostraron una baja contaminación con almidón, color más claro y comportamiento newtoniano. Después de la purificación de EβG, la contaminación con almidón y proteína disminuyó (0.85 ± 0.46% y 5.50 ± 0.12%, respectivamente), aumentó el contenido de βG (69.45 ± 0.81%) y aumentó su luminosidad (L* = 92.60 ± 1.70). Los β-glucanos purificados (PβG) mostraron un peso molar de 690 ± 1,6 kDa y se identificaron en la estructura especies con grado de polimerización desde 3 (GP3) hasta 11 (GP11). Conclusiones: los EβG antes de la purificación presentaron alta viscosidad y contaminación. El proceso de purificación enzimática fue efectivo y permitió mantener una alta masa molar de la fibra y sus estructuras moleculares características (especies con GP3 y GP4). Las muestras comerciales CβG-A y CβG-B mostraron un bajo contenido de β-glucanos. Finalmente, la CβG-C presentó las mejores propiedades fisicoquímicas y reológicas para su posterior aplicación en alimentos.

ABSTRACT Background: β-glucans (1-3: 1-4) are soluble fibers applied to foods due to their technological properties (water binding capacity, viscosity, emulsification and stabilization) and their beneficial effects on health. The functional properties of β-glucans can be lost during the extraction and purification processes. The high viscosity of β-glucans is related to a high molecular weight and its physiological properties in the intestine. Therefore, to characterize the fiber after its extraction and purification is fundamental to understand its possible applications in foods. Objectives: characterize β-glucans extracted (EβG) and compare them with three commercial β-glucans (CβG-A, CβG-B and CβG-C) to identify its possible applications in foods and to evaluate if enzymatic purification affects molecular and structurally the β-glucans. Methods: barley β-glucans were extracted (EβG), characterized by chemical analyzes, rheological behavior, and color, and compared to three commercial β-glucans samples. Then, the extract was purified and its structural and molecular characteristics were calculated. Results: EβG contained 64.38 ± 3.54% of β-glucans, high starch contamination (12.70 ± 1.73%), high content of calcium (8894 mg/kg), pseudoplastic behavior, and dark color (L* = 52.77 ± 0.7). All commercial samples showed low starch contamination, lighter color, and Newtonian behavior. After purification starch and protein contamination decreased (0.85 ± 0.46% and 5.50 ± 0.12% respectively), increased the content of βG (69.45 ± 0.81%) and increased brightness (L* = 92.60 ± 1.70). Purified β-glucans (PβG) showed a molar weight of 690 ± 1.6 kDa and species with degree polymerization 3 (DP3) to 11 (DP11) were identified on the structure. Conclusions: EβG extracts before the purification presented a high viscosity and contamination. The enzymatic purification process was effective and allowed to maintain a high molar mass of PβG and its distinctive molecular structures (species with DP3 and DP4). The commercial samples CβG-A and CβG-B showed a low content of β-glucans. Finally, CβG-C presented the best physicochemical and rheological properties for its subsequent application in food.

Resumo Objetivo: wake-up stroke (WUS) define o acidente vascular cerebral (AVC) que ocorre sem horário preciso de início, pois os sintomas manifestam-se ao despertar. Alterações do sono associam-se a maior risco de AVC e doenças cardíacas. Este estudo avalia as características dos pacientes com e sem WUS, a presença de sonolência diurna e os fatores de risco associados. Método: pacientes com AVC isquêmico foram identificados quanto à presença de WUS. Foram avaliadas as características clínico-demográficas, a gravidade do AVC pela National Institutes of Health Stroke Scale (NIHSS) e pela Modified Rankin Scale (MRS) e o grau de sonolência pela Epworth Sleepiness Scale (ESS). Resultados: setenta pacientes (57,1% homens) com idade entre 32 e 80 anos (58,5±13,3) foram estudados. Wake-up stroke foi observado em 24,3% dos casos. Hipertensão arterial sistêmica (67,1%), diabetes (27,1%) e distúrbio do metabolismo lipídico (22,8%) foram frequentes. Diabetes e hábitos sedentários foram mais comuns nos casos com WUS (p<0,05). Na amostra total, 62,3% dos casos apresentavam AVC leve, moderado ou com poucos sintomas (NIHSS<5). Sonolência excessiva diurna (SED) (ESS>10) foi identificada em 20% dos pacientes. Não houve diferença entre os grupos com e sem WUS quanto à gravidade do AVC e o grau de sonolência. Pacientes com SED eram mais jovens e mais sedentários (p<0,05). Os indivíduos com etilismo tinham maior grau de sonolência (p=0,03). Conclusão: wake-up stroke manifesta-se em 25% dos casos de AVC isquêmico. Neste estudo, os pacientes com WUS apresentaram mais diabetes e sedentarismo. Sonolência diurna é frequente e associa-se a hábitos sedentários e etilismo.

Summary Objective: Wake-up stroke (WUS) is defined when the exact time of the beginning of the symptoms cannot be determined, for the deficits are perceived upon awakening. Sleep alterations are important risk factors for stroke and cardiovascular diseases. This study evaluates the characteristics of patients with and without WUS, the presence of daytime sleepiness, and associated risk factors. Method: Patients with ischemic stroke were investigated about the presence of WUS. Clinical and demographic characteristics were evaluated. Stroke severity was studied by the National Institutes of Health Stroke Scale (NIHSS) and the Modified Rankin Scale (MRS), and daytime sleepiness severity was studied by the Epworth Sleepiness Scale (ESS). Results: Seventy patients (57.1% men) aged from 32 to 80 years (58.5±13.3) were studied. WUS was observed in 24.3%. Arterial hypertension (67.1%), type 2 diabetes (27.1%), and hyperlipidemia (22.8%) were frequent. Type 2 diabetes and sedentary lifestyle were more common in patients with WUS (p<0.05). Overall, mild, moderate or very few symptoms of stroke (NIHSS<5) were predominant (62.3%). Among all cases, 20% had excessive daytime sleepiness (ESS>10). No differences were found between patients with and without WUS as regards stroke severity or excessive daytime sleepiness. Patients with excessive daytime sleepiness were younger and had more sedentary lifestyle (p<0.05). Individuals with previous history of heavy drinking had more daytime sleepiness (p=0.03). Conclusion: Wake-up stroke occurs in approximately 25% of stroke cases. In this study, patients with WUS had more diabetes and sedentary lifestyle. Daytime sleepiness is frequent and is associated with sedentary lifestyle and heavy drinking.

RESUMO: O polvilho azedo é um amido naturalmente modificado, produzido por fermentação e seco ao sol, atingindo a propriedade de expansão. Produtos de panificação a partir do polvilho azedo podem ser preparados sem a adição de leveduras e são livres de glúten. O processo fermentativo tem sido exaustivamente estudado, mas as águas residuais com elevada acidez e ricas em compostos orgânicos derivados da degradação do amido, requerem futuros trabalhos. Neste estudo, a estrutura dos sólidos presentes nesse efluente foi estudada vislumbrando futuras aplicações para estes novos materiais. Os sólidos contidos na água residual foram secos em spray dryer com maltodextrina (MD), com equivalente de dextrose (DE) de 5 e 15. A estrutura das partículas foi observada por microscopia eletrônica de varredura. Uma estrutura regular com arranjo em rede foi observada para o material seco com MD DE 5, em características que diferem das estruturas do amido nativo e do amido fermentado, o que sugere uma nova e regular organização estrutural com futuras aplicações a serem determinadas.

ABSTRACT: Sour cassava starch is a naturally modified starch produced by fermentation and sun drying, achieving the property of expansion upon baking. Sour cassava starch' bakery products can be prepared without the addition of yeast and it is gluten free. The fermentation process associated with this product has been well studied, but the wastewater, with high acidity and richness in other organic compounds derived from starch degradation, requires further investigation. In this study, the structure of solids present in this residue was studied, seeking to future applications for new materials. The solids of the wastewater were spray dried with maltodextrin (MD) with dextrose equivalent (DE) of 5 and 15 and the structure of the powder was evaluated by scanning electron microscopy. A regular structure with a network arrangement was observed for the dried material with MD of 5 DE, in contrast to the original and fermented starches structure, which suggests a regular organization of this new material, to be studied in future applications.

A composição química da farinha de trigo e a presença de fibras afeta as características dos pães. Uma forma de contribuir com a prevenção de doenças crônicas não transmissíveis é através de alimentação saudável, incluindo grãos integrais na dieta alimentar e reduzindo as calorias de determinado alimento, substituindo a gordura. Assim, este trabalho tem como objetivo determinar a composição centesimal das amostras de farinha de trigo integral, refinada e as misturas entre elas; bem como os parâmetros farinográficos (absorção de água, tempo de desenvolvimento e estabilidade) das mesmas. Além disso, verificar volume específico, perfil de textura do miolo e análise de imagem de pães elaborados com 60% de farinha de trigo integral e com 3% de gordura ou com substituto de gordura. Os dados foram submetidos à análise de variância. À medida que aumenta o percentual de farinha integral, os teores de proteína, cinzas e fibra insolúvel alcançam valores significativamente maiores e a absorção de água fica maior na farinografia, bem como o tempo de desenvolvimento e a estabilidade. O amido modificado enzimaticamente utilizado na elaboração de pão com 60% de farinha de trigo integral funcionou como um efetivo substituto de gordura. O pão integral elaborado com substituto de gordura apresentou volume específico significativamente igual ao pão integral elaborado com gordura, porém com diferenças em relação a parâmetros do perfil de textura, maior firmeza e menor elasticidade além de maior densidade celular do que o pão elaborado com gordura.

Bread characteristics are dependent upon the chemical composition and fiber content of the wheat flour used. A healthy diet can help prevent chronic diseases, where whole grains and fewer calories from fat are components of a healthy diet. The aims of this study were to determine the centesimal composition of wheat flour samples (whole, refined, and flour blends) along with their farinographic parameters (water absorption, development time and stability) and also to verify the specific volume, crumb texture profile and digital imaging of bread loaves made with 60% whole wheat flour and 3% fat or fat replacer. Increasing the whole wheat flour percentage in the blends also increased levels of protein, ash and insoluble fiber. All the farinographic parameters were also increased. Enzymatically modified starch was found to be an effective fat replacer in whole wheat loaves. The loaves made using fat replacer had the same specific volume and higher cell density as those made with fat, but exhibited different texture profile parameters such as higher hardness value and lower springiness value.

Micropartículas de poli(3-hidroxibutirato) (PHB) contendo cetoprofeno (KET) como fármaco modelo foram preparadas através da técnica de emulsão-evaporação do solvente O/W. Com o intuito de atribuir uma barreira adicional à liberação do cetoprofeno, micropartículas de KET/PHB foram revestidas por um filme de quitosana através da técnica spray drying. O filme de quitosana foi reticulado com glutaraldeído ou genipin. A eficiência de encapsulação, 60%, foi da mesma ordem de grandeza para todas as formulações de micropartículas estudadas. A influência das concentrações de quitosana e do agente reticulante (glutaraldeído e genipin) na quantidade de cetoprofeno liberado após 1 h, e sobre o prolongamento de liberação em 72 h, foi avaliada através de análises estatísticas, indicando que ambas as variáveis influenciaram as respostas. A liberação do cetoprofeno a partir de micropartículas compostas recobertas com quitosana reticulada foi lenta e sustentável, sendo um transportador polimérico muito promissor para a libertação de fármacos.

The purpose of this study was to prepare composite microparticles of poly(3-hydroxybutyrate) (PHB) containing the drug ketoprofen (KET) coated with a layer of crosslinked chitosan (CHI) for application as a controlled drug-release system. Microparticles of PHB containing KET as a model drug were prepared using the emulsion-solvent evaporation technique, and coated with a film of chitosan by spray drying to obtain the composite microparticles. The surface film was modified using glutaraldehyde or genipin as the crosslinking agent. The KET encapsulation efficiency of the PHB microparticle was 60%, and the same value was obtained after inclusion of the CHI film by the spray drying process. The influence of the concentration of chitosan used to obtain the composite microparticles and the crosslinking agent on the amount of drug released after 1 and 72 h was evaluated by statistical analysis, and both variables were found to affect the responses. The drug release from the composite microparticles coated with crosslinked chitosan was slow and sustainable, indicating that this represents a very promising polymeric carrier for drug delivery.

Neste artigo, as propriedades emulsificantes da proteína isolada de soja (SPI) foram evidenciadas mostrando que estas macromoléculas sofrem mudanças conformacionais quando adsorvidas em interfaces. Investigou-se a conformação das cadeias proteicas ancoradas nas regiões interfaciais de emulsões de óleo em água (o/a) através de técnicas de espalhamento de raios X (SAXS) e de imagem (microscopia eletrônica de varredura (SEM)). O valor médio do raio de giro (Rg) da SPI (aq) é 20 nm e aumenta para 30 nm em emulsões o/a; as proteínas atuam como moléculas anfifílicas expondo seus núcleos hidrofóbicos ao óleo e os resíduos hidrofílicos à fase aquosa. Este valor ainda é maior após o spray drying das emulsões, na interface o/ar das respectivas microcápsulas. As paredes das microcápsulas são fractais de objetos agregados com superfícies rugosas, que são alisadas pela presença de um agente de reticulação.

Herein, the emulsifying properties of soy protein isolate (SPI) were highlighted by showing that the macromolecules undergo conformational changes when adsorbed at interfaces. The conformation of protein chains nested at the interfacial region of oil in water (o/w) emulsions by means of X-ray scattering (SAXS) and direct imaging (scanning electron microscopy (SEM)) techniques was investigated. The mean radius of gyration (Rg) for SPI (aq) is 20 nm and increases up to 30 nm in o/w emulsions; the proteins act as amphiphilic molecules by exposing their hydrophobic core to the oil and their hydrophilic amino acid residues to the water phase. By spray drying the emulsions, it was also possible to measure the size (Rg = 40 nm) and to evaluate the morphology of these proteins at the oil/air interface of the respective microcapsules. The walls of microcapsules are fractals of clustered objects with rough surfaces, which are smoothed by the presence of a cross-linking agent.

The dispersion of carbon nanotubes in water for their utilization in nanoscale devices is a challenging task. Comparative studies on interaction and dispersion of multi-wall carbon nanotubes (MWNT) using two different surfactants (sodium dodecyl sulfate, SDS, and polyoxyethylenesorbitanmonooleate, Tween 80) are presented. The interaction between carbon nanotubes and surfactants was studied by tensiometry, conductivimetry, and fluorimetry. The dispersions of MWNT in surfactants were characterized using a UV-vis spectrophotometer. For effective dispersion, the minimum weight ratio of MWNT to surfactant was 1:41 and 1:3 for SDS and Tween 80, respectively.

Este estudo tem como objetivo otimizar um método alternativo para extração de carragenana sem tratamento alcalino prévio e sem precipitação com etanol através da Metodologia de Superfície de Resposta (RSM). A fim de inovar a etapa de isolamento, a secagem por atomização foi adaptada, o que reduziu o tempo para a obtenção do pó seco. Os efeitos da temperatura e do tempo de extração sobre o rendimento, força do gel e de viscosidade foram avaliados. Além disso, o material extraído foi submetido a análises estruturais por espectroscopia de infravermelho e de ressonância magnética nuclear, e composição química. Os resultados mostraram que os modelos de regressão gerados explicam adequadamente a variação de dados. Apenas a temperatura de extração afetou o rendimento e a viscosidade do gel. Entretanto, a força do gel foi influenciada tanto pelo tempo como pela temperatura de extração. As condições ótimas de extração foram 74 ºC durante 4 horas. Nessas condições, as propriedades da carragenana bruta determinadas pelo modelo polinomial foram 31,17%, 158,27 g.cm-2 e 29,5 cP, para rendimento, força do gel e viscosidade, respectivamente, enquanto que em condições experimentais foram 35,8 ± 4,68%, 112,50 ± 4,96 g.cm-2 e 16,01 ± 1,03 cP. A composição química e as análises estruturais mostraram que a carragenana extraída é principalmente κ-carragenana.

This study aims to optimize an alternative method of extraction of carrageenan without previous alkaline treatment and ethanol precipitation using Response Surface Methodology (RSM). In order to introduce an innovation in the isolation step, atomization drying was used reducing the time for obtaining dry carrageenan powder. The effects of extraction time and temperature on yield, gel strength, and viscosity were evaluated. Furthermore, the extracted material was submitted to structural analysis, by infrared spectroscopy and nuclear magnetic resonance spectroscopy (¹H-NMR), and chemical composition analysis. Results showed that the generated regression models adequately explained the data variation. Carrageenan yield and gel viscosity were influenced only by the extraction temperature. However, gel strength was influenced by both, extraction time and extraction temperature. Optimal extraction conditions were 74 ºC and 4 hours. In these conditions, the carrageenan extract properties determined by the polynomial model were 31.17%, 158.27 g.cm-2, and 29.5 cP for yield, gel strength, and viscosity, respectively, while under the experimental conditions they were 35.8 ± 4.68%, 112.50 ± 4.96 g.cm-2, and 16.01 ± 1.03 cP, respectively. The chemical composition, nuclear magnetic resonance spectroscopy, and infrared spectroscopy analyses showed that the crude carrageenan extracted is composed mainly of κ-carrageenan.

O ácido hialurônico (AH) é uma importante macromolécula nas áreas médica e farmacêutica. O cordão umbilical e a crista de frango constituem uns dos tecidos mais ricos nesse polissacarídeo. O aproveitamento das cristas dos animais abatidos para a obtenção de HA é particularmente atraente. O presente trabalho teve como objetivo a extração, purificação e caracterização do AH. A concentração de glicosaminoglicanos encontrada na crista de frango foi ao redor de 15µg de ácido hexurônico mg-1 de peso seco. O fracionamento por cromatografia de troca iônica e a subsequente identificação das frações por eletroforese de gel de agarose mostrou que o AH corresponde a 90% do total de glicosaminoglicanos extraídos.

Hyaluronic acid (HA) is an important macromolecule in medical and pharmaceutical fields. The umbilical cord and the chicken comb are some of the tissues richest in this polysaccharide. The profit from obtaining HA from the combs of slaughtered animals is particularly attractive. This work aimed to extract, purify, and characterize HA. The glycosaminoglycan concentration in the chicken comb was found to be about 15µg of hexuronic acid mg-1 of dry tissue. Fractionation using ion exchange chromatography and subsequent identification of the fractions by agarose gel electrophoresis showed that HA corresponded to 90% of the total amount of extracted glycosaminoglycans.