Nejayote is a nixtamalization waste by-product, and for this reason, in this study, filtration cakes as well as filtrate nejayote were evaluated to select the filter medium and also to establish the operation conditions. The different media used as filters at constant pressure filtrations were polyester-cotton canvas, paper, and nylon. The filtrations showed that polyester-cotton canvas presents lower specific resistance of the cake at all pressure levels and dosages. Calcium content was less in filter medium nylon at pressure 98.10 kPa and dosage 1:0.25 nejayote/ diatomaceous earth. Regarding particle diameter, the nylon and paper filter media have the highest quality filtering at pressure of 63.77 kPa and dosage 1:0.25 nejayote/diatomaceous earth. Therefore, the filtration depends not only on the particle diameter of the solids, dosage and nejayote cake morphology, but that the filter media is also important in the selection of the operation conditions. Keywords: nejayote; filtration; dosage; filter media El nejayote es un subproducto contaminante de la nixtamalización, por lo que en este estudio se obtuvieron tortas de filtración y filtrados que fueron evaluados para seleccionar el medio filtrante y establecer condiciones de filtración. Los medios filtrantes empleados en la filtración a presión constante fueron: lona poliéster algodón, papel y nylon. Las filtraciones evidenciaron que la lona poliéster algodón presenta menor resistencia específica de la torta en todos los niveles de presión y dosificación. El contenido de calcio fue menor en el medio filtrante nylon a la presión 98,10 kPa y dosificación 1:0,25 nejayote/tierra diatomea. Respecto al diámetro de partícula los medios filtrantes nylon y papel dan una mayor calidad de filtrado a la presión 63,77 kPa y dosificación 1:0,25 nejayote/tierra diatomea. En consecuencia, la filtración no sólo depende del diámetro de partícula de los sólidos, dosificación y morfología de la torta de nejayote, también el medio filtrante es determinante en la selección de las condiciones de operación.
Usually, the maize cob is formed by grains of medium size. However, the extremes have larger or smaller size grains. The objective of this study was to investigate the influence of grain size from the same hybrid on the physicochemical properties of isolated starch, crude maize flours and nixtamalized maize flours. Two hybrids, one from CIMMyT-Mexico called IMIC-254 and one commercial sample from Monsanto (Puma) were studied. The isolated starch granules from small, medium, and large grains exhibit the same size and distribution. The grain size has influence in the determination of cooking and steeping times; small grains reach these parameters faster than medium and large ones. The hardness of the grain size for both hybrids does not showed statistic-*
Durante la preparación biomecánica del conducto radicular se forma una capa llamada lodo dentinario, se han utilizado varias sustancias químicas para su remoción. En nuestro estudio se utilizaron conductos amplios y rectos de sesenta y cinco dientes extraídos. Se dividieron tres grupos experimentales aleatoriamente de 20 conductos y un grupo control positivo de 5 conductos. El grupo control se irrigó con NaOCl al 5.25% como irrigación final. A los grupos restantes se les irrigó con acondicionador «A» a base de EDTA al 17%; acondicionador «B» EDTA al 17% y cetrimida; acondicionador «C» EDTA al 17% y un surfactante y como irrigación final NaOCl al 5.25% y se observaron en el microscopio electrónico de barrido. Los resultados mostraron que el acondicionador «B» logró eliminar el lodo dentinario casi en su totalidad y en donde se utilizaron los acondicionadores «A» y «C» los resultados mostraron una eliminación parcial del lodo dentinario. Estas diferencias encontradas fueron estadísticamente significativas en el grupo del acondicionador «B», cuando fueron analizadas mediante la prueba de χ2 (P < 0.05). Estos resultados fueron similares en el tercio apical y el tercio medio de los conductos radiculares.
Size and external and internal morphologies of nanoparticles and microparticles are very important on the design of drug devices for controlled release. Random enteric copolymers such as poly (methacrylic acid-coethyl acrylate) and poly (methacrylic acid-co-methyl methacrylate) were used to produce nanoparticles, which contain a model drug and could be employed as drug carriers for proteins. The solvent effect on re-dispersion of such nanoparticles was studied by Scanning Electron Microscopy (SEM) and revealed not only differences in size, but also several shapes, depending on the chemical nature of the polymer matrix and the non-solvent used. Acrylate containing copolymers in acidic aqueous dispersions lead to spheroidal particles. However for the copolymer containing methyl methacrylate, spheroidal particles collapsed in a "grenade" type morphology and besides some cubic structures are also formed.Dynamic Light Scattering (DLS) studies of the re-dispersed nanoparticles showed the strong tendency to form agglomerates not only in acidic water but also in hexane and the presence of bimodal size distributions.
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