Browsing by Subject "Viscosity"

Now showing 1 - 5 of 5
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    Analysis of the porosity and microhardness of glass ionomer cements
    (Kaunas University of Technology (Lithuania), 2022-02-18) Cabello Malagón, Inmaculada; Cánovas Hernández, Basilio; Martínez Hernández, Elisa; Serna Muñoz, Clara; Pérez Silva, Amparo; Ortiz Ruiz, Antonio José; Dermatología, Estomatología, Radiología y Medicina Física
    Glass ionomer cements (GICs) are currently the first-choice materials in minimally invasive dentistry and are widely used in paediatric dentistry. The objective of this study was to evaluate the influence of viscosity and mixing on porosity and the relationship between the porosity and microhardness of GICs. Nine GICs were used: EQUIA® Forte Fil, Ionostar®Plus, 3MTMKetacTM Universal AplicapTM, Riva Light Cure HV®, Riva Silver®, Riva Protect®, VitremerTM, VitrebondTM Plus and Activa BioActive RestorativeTM. Samples were prepared from each material and images were obtained by scanning electron microscopy (SEM). Using software, the number and diameter of pores, area, and percentage of area they occupied were measured. After SEM analysis, the samples were used to make surface microhardness (SMH) measurements. Ionostar® Plus, EQUIA® Forte Fil and Riva Light Cure HV® had the highest number of pores. Riva Protect® had the largest pores and the highest percentage of pore-occupied area, while Activa BioActive RestorativeTM and VitrebondTM Plus had a smaller pore size and a smaller percentage by area. Riva Silver® and EQUIA® Forte Fil showed the highest microhardness values and VitrebondTM Plus and VitremerTM the lowest. In conclusion, when the cement viscosity is low, the type of mixture determines the degree of porosity, but has less influence when viscosity is high. There was no correlation between microhardness and the porosity of GICs.
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    Description and comparative study of physico-chemical parameters of the teleost fish skin mucus.
    (SAGE Publications, 2015-07-01) Guardiola Abellán, Francisco Antonio; Cuartero, María; Collado-González, Mar; Arizcún, Marta; Díaz Baños, F. Guillermo; Meseguer, José; Esteban Abad, María de los Ángeles; Biología Celular e Histología
    The study of mucosal surfaces, and in particular the fish skin and its secreted mucus, has been of great interest recently among immunologists. Measurement of the viscosity and other physico-chemical parameters (protein concentration, pH, conductivity, redox potential, osmolality and density) of the skin mucus can help to understand its biological functions. We have used five marine species of teleost: gilthead seabream (Sparus aurata L.), European sea bass (Dicentrarchus labrax L.), shi drum (Umbrina cirrosa L.), common dentex (Dentex dentex L.) and dusky grouper (Epinephelus marginatus L.), all of them with commercial interest in the aquaculture of the Mediterranean area. Mucus showed a direct shear- and temperature-dependent viscosity, with a non-Newtonian behavior, which differed however between two groups: one with higher viscosity (D. labrax, U. cirrosa, D. dentex) and the other with lower viscosity (S. aurata, E. marginatus). In addition, there was a clear interrelation between density and osmolality, as well as between density and temperature. Taking into account that high values of viscosity should improve the barrier effect against pathogens but low values of viscosity are needed for good locomotion characteristics, our results may help elucidate the relationship between physico-chemical and biological parameters of skin mucus, and disease susceptibility.
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    Effect of adding different thickening agents on the viscosity properties and in vitro mineral availability of infant formula
    (Elsevier, 2014-03-12) González Bermúdez, Carlos Alberto; Frontela Saseta, María del Carmen; López Nicolás, Rubén; Ros Berruezo, Gaspar; Martínez Gracia, Carmen; Tecnología de Alimentos, Nutrición y Bromatología
    The effect of adding different thickening agents (locust bean gum (LBG), modified corn and rice starches (MCS, MRS)) to an infant formula on both in vitro mineral availability (Ca, Fe and Zn), quantified by atomic absorption spectrophotometry (AAS), and formula viscosity, after in vitro gastrointestinal digestion, was investigated. LBG was the most effective agent to increase formula thickness. However, it showed a negative effect on Ca, Fe and Zn in vitro solubility and dialysability. MCS and MRS only affected calcium solubility and dialysability when they were used at P50% of the maximum legal limit. No negative effect was observed for Fe and Zn when modified starches were added at the different concentrations assessed. The phytate content in the thickening ingredients was also analysed. Despite finding a considerable amount of phytic acid in the raw ingredients, its final concentration in the infant formula was insufficient to decrease in vitro mineral availability.
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    Non-Newtonian viscosity of dilute polymer solutions
    (2005-01-20) Pamies, Ramón; López Martínez, M. Carmen; Hernández Cifre, José Ginés; García de la Torre, José; Química Física
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    Physicochemical properties of different thickeners used in infant foods and their relationship with mineral availability during in vitro digestion process
    (Elsevier, 2015) Castro, Alejandra; Perez-Rea, Daysi; González Bermúdez, Carlos Alberto; Frontela Saseta, María del Carmen; Nilsson, Lars; Martínez Gracia, Carmen; Tecnología de Alimentos, Nutrición y Bromatología
    Locust bean gum (LBG) and modified starches are commonly used as thickeners in food products for infants. However, there is no consensus on their possible effects on infant nutrition, especially on mineral availability. The aimof the present work was to characterize the effect of LBG, cross-linked, hydroxypropylated maize starch (Mhdp) and pre-gelatinized rice starch (gRS) on Ca, Fe and Zn availability during a gastric and intestinal in vitro digestion assay in relation to their physicochemical properties in solution (apparent viscosity, solubility, molar mass (M) and conformational properties) through the simulated digestion process. LBG gave the highest decrease in Ca and Fe gastric (17.96% and 17.6% respectively) and intestinal (19.5% and 13.5%) solubility with respect to the referencewithout thickeners. Ca (11.1%±1.1), Fe (2.77%±0.3) and Zn (7.78%±0.6) dialyzability was also lower than for the reference (23.4%±2.9; 19.65%±3.53 and 27.74%±3.3 respectively). LBG solubility remained stable during gastric digestion, decreasing significantly from a range of 65–69% to 61.1% after intestinal digestion. LBG viscosity remained stable during the digestion process, being these findings attributable to its resistance to enzymes. On the other hand, the addition to Mhdp or gRS slightly affected Ca and Fe solubility or Ca dialyzability, decreasing after gastric digestion and then increasing after intestinal digestion with respect to the reference. These results correlated to the changes in their viscosity enhancing properties, which increased during gastric digestion and decreased after intestinal digestion, being attributable to their digestion by pancreatic enzymes. Gastric digestion resulted in an increase inMfor themodified starches (more pronounced for gRS). The increase inmineral solubility and dialyzability after intestinal digestion with respect to the gastric stage was explained by the degradation of starches by intestinal enzymes, which resulted in a decrease in apparent shear viscosity (from 1.2 to 1 Pa s, measured in a shear rate range 0.00–50 s−1) and an increase in solubility (from 3 to 6% to approximately 70%) after intestinal digestion. In conclusion, LBG could be more effective than Mhdp and gRS as thickener, providing higher viscosity and resistance to digestive process. However, its negative effect on mineral solubility and dialyzability should be taken into account. On the contrary,Mhdp and gRS showed to be degraded after intestinal digestion.