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Search Results: 1 - 10 of 207541 matches for " Nú?ez-Santiago "
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Caracterización morfológica, molecular y fisicoquímica del almidón de plátano oxidado y lintnerizado
Rivas-González, Mayra;Méndez-Montealvo, M. Guadalupe C.;Sánchez-Rivera, Mirna M.;Nú?ez-Santiago, M. Carmen;Bello- Pérez, Luis A.;
Agrociencia , 2008,
Abstract: a morphological, molecular and physicochemical characterization was made of the starch extracted from the banana (musa paradisiaca l.), chemically modified by oxidation and by lintnerization. native banana starch was used as reference. the modification level was evaluated through polarized light microscopy, x-ray diffraction, infrared spectroscopy and the viscoamylographic profile. the oxidized starch presented a substitution degree of 0.13 and 0.03% of carbonyl and carboxyl groups. the native and modified starches presented the maltese cross (birefringence) indicating a crystalline organization. the three starches presented diffraction pattern between a- and b-types. infrared spectroscopy revealed the presence of a high level of organization within the granules: 1.678, 1.689 and 1.883 for the native, oxidized and lintnerized starches. there were no differences (p>0.05) in the viscosity profile of the native and oxidized starches, whereas the lintnerized starch presented lower values due to a probable hydrolysis provoked during the modification. the lintnerized starch also presented the least changes in its enthalpies (δh) of gelatinization and retrogradation, suggesting the formation of smaller and more imperfect crystals. the characterization made on the modified banana starches could suggest their possible industrial applications.
Some intrinsic and extrinsic factors of acetylated starches: morphological, physicochemical and structural characteristics
Nú?ez-Santiago, M.C.;García-Suárez, F.J.;Gutierrez-Meraz, F.;Sánchez-Rivera, M.M.;Bello-Pérez, L.A.;
Revista mexicana de ingeniería química , 2011,
Abstract: degree substitution (ds), morphological characteristics, x-ray diffraction (xrd), pasting properties, thermal properties and amylopectin chain length distribution were used to study the effect of botanical source (potato starch, ps; and maize starch, ms) and reagent type (acetic anhydride and vinyl acetate) on starch acetyration. the reagent type produced a different effect depending on the botanical source: for ms, the reaction with acetic anhydride produced higher ds than ps, whereas that in the reaction with vinyl acetate resulted in an inverse pattern. in general, modified starches had a maltase cross, except for ps when acetylated with acetic anhydride. native ps had the highest crystallinity level and trie acetylated starches had a decreased amount of crystallinity (between 10% and 12 %) compared to the native starches. acetylation produced a decrease in pasting temperature, and changes in the pasting characteristics were more evident wish higher ds. structural changes in starch components due to the acetylation reaction produced a decrease in the temperature and enthalpy of gelatinization. in general, acetylated starches had minor retrogradation. regardless of reagent used, acetylated ms had higher retrogradation than acetylated ps. higher ds values resulted in greater amounts of short chains in both starches.
Overview of Multidrug-Resistant Pseudomonas aeruginosa and Novel Therapeutic Approaches  [PDF]
Marilyn Porras-Gómez, José Vega-Baudrit, Santiago Nú?ez-Corrales
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2012, DOI: 10.4236/jbnb.2012.324053
Abstract: Gram-negative bacilli Pseudomonas aeruginosa is an important pathogen in hospitalized patients, contributing to their morbidity and mortality due to its multiple resistance mechanisms. Therefore, as therapeutic options become restricted, the search for new agents is a priority. Latterly an accelerated increase in frequency of multidrug-resistant clinical strains has severely limited the availability of therapeutic options. Several in vitro and in vitro studies evaluating the efficacy of different antimicrobials agents and development of vaccines against P. aeruginosa have been reported as novel approaches, such as inhibition of virulence factor expression or inhibition of their metabolic pathways.
Complexation of Eugenol (EG), as Main Component of Clove Oil and as Pure Compound, with β- and HP-β-CDs  [PDF]
Pilar Hernández-Sánchez, Santiago López-Miranda, Carmen Lucas-Abellán, Estrella Nú?ez-Delicado
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.36097
Abstract: Eugenol, both in its pure form (EG) and included in essential clove oil (CO) was successfully solubilized in aqueous solution by forming inclusion complexes with β-cyclodextrins (β-CDs) and its modified hydroxy-propyl-β-CDs (HP-β-CDs). To investigate the molecular association between β-CDs/HP-β-CDs with pure EG and essential CO, phase solubility studies were undertaken. Essential CO formed insoluble complexes with β-CDs, but not with HP-β-CDs. The work clearly demonstrates complexes formation follow an order higher than 1:1 when high essential CO and β-CDs concentrations were used, however it was 1:1 in the case of essential CO-HP-β-CDs complexes. When pure EG was studied the results indicated that EG could form 1:1 inclusion complexes with β-CDs and HP-β-CDs. Based on the studies, the Kc values for pure EG were 4555 ± 225 M-1 and 10,633 ± 614 M-1 for β-CDs and HP-β-CDs, respectively, and 2005 ± 199 M-1 for essential CO-HP-β-CDs. These finding indicate that CDs are suitable for encapsulating EG.
Evaluation of the Synergistic Effect of EDTA-Functionalized Chitosan Nanoparticles on Imipenem Delivery in Pseudomonas aeruginosa Carbapenem-Resistant Strain AG1  [PDF]
Marilyn Porras-Gómez, José Vega-Baudrit, Fernando García, Santiago Nú?ez-Corrales, Sergio Madrigal-Carballo
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2018, DOI: 10.4236/jbnb.2018.91006
Abstract: Metallo-β-lactamases are bacterial zinc-dependent enzymes involved in the hydrolysis of β-lactamic antibiotics representing the main cause of bacterial resistance to carbapenems, drugs of last resort for treating infections caused by multiresistant bacteria. We elaborated the hypothesis that it is possible to inhibit the enzymatic activity of metallo-β-lactamases by lowering the availability of zinc in the extracellular medium using metal chelating agents such as EDTA carried on nanoparticles. Chitosan, as linear cationic polysaccharide is frequently used in biomedical and pharmaceutical applications, has been studied as a biocompatible encapsulating agent in drug delivery systems and is an ideal transport agent for bioactive molecular complexes in antibiotic applications due to its ability to associate with negatively charged substances. We developed novel nanoparticles using chitosan as a transport matrix for β-lactamic antibiotics. Nanoparticles were synthesized according to the ion gelation method using tripolyphosphate as crosslinking agent. Nanoparticles were functionalized by the adsorption of EDTA, which acts as complexifying agent for Zn2+ ions causing inhibition of metallo-β-lactamases activity. We evaluate the antimicrobial effects of EDTA-functionalized nanoparticles with an imipenem cargo on the clinical isolate P. aeruginosa AG1, a carbapenem-resistant high-risk clone ST-111 carrying both blaIMP-18 and blaVIM-2
Memorias Asociativas Basadas en Relaciones de Orden y Operaciones Binarias
Yá?ez Márquez, Cornelio;Díaz de León Santiago, Juan Luis;
Computación y Sistemas , 2003,
Abstract: a new model for associative memories is proposed in this paper. the mathematical tools used in this new model, include two binary operators designed specifically for the memories developed here. these operators were arbitrarily named as the first two letters from the greek alphabet: α and β. the new associative memories (αβ) are of two kinds and are able to operate in two different modes. the operator α is useful at the learning phase, and the operator β is the basis for the pattern recall phase. the properties within the algebraic operators α and β, allow the αβ memories to exhibit similar characteristics to the ones inherent to the binary version of the morphological associative memories, in the sense of: learning capacity, type and amount of noise against which the memory is robust, and the sufficient conditions for perfect recall. moreover, it is important to point out that the arithmetic density of the proposed memories is smaller than the arithmetic density exhibited by the morphological ones. the main reason for taking the morphological associative memories as the reference point for the genesis of the proposed ones, consist in that the authors of the first ones have already shown that the morphological associative memories are superior in some aspects to the known models of associative memories, up to the beginning of the third millenium.
Controlling the Strongly Damping Inertia Wheel Pendulum via Nested Saturation Functions
Aguilar Ibá?ez, Carlos;Gutiérrez Frías, óscar Octavio;Suárez Casta?ón, Miguel Santiago;
Computación y Sistemas , 2009,
Abstract: in this paper we solve the stabilization problem of the strongly damping inertia wheel pendulum around its unstable equilibrium. the stabilization is accomplished by using nested saturation functions. the use of nested saturation function is possible because this system can be rewritten approximately as a chain of integrators with and nonlinear perturbation. the proposed control strategy makes the closed-loop system globally asymptotically and locally exponentially stable around the unstable inverted vertical position, even when the physical damping is presented in the model.
Estudio de las vías de difusión de la lesión de mancha blanca del esmalte
Domínguez Medina,Nuria; González López,Santiago; Menéndez Nú?ez,Mario;
RCOE , 2002, DOI: 10.4321/S1138-123X2002000600002
Abstract: the aim of this article is to present and relate the different ways of diffusion of the white spot lesion, its deepness, geometry and peaks of progression. materials and method: in the study we used 27 human teeth containing white spot lesions on their free surfaces; the specimens were prepared for visualization under a polarized light microscopy. results: the histological lesions of enamel caries are wider than deep, with a predomination of triangular shapes presenting more than one peak of progression. the main ways of diffusion are retzius striae and prism sheaths.
Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales: Bacillariophyceae)
Vouilloud,Amelia A; Sala,Silvia E; Nú?ez Avellaneda,Marcela; Duque,Santiago R;
Revista de Biología Tropical , 2010,
Abstract: diatoms from the colombian and peruvian amazon: the genera encyonema, encyonopsis and gomphonema (cymbellales, bacillariophyceae). the diatom flora of the colombian and peruvian amazon is far less studied than the flora of the brazilian sector of the basin. here we present results related to the genera encyonema, encyonopsis and gomphonema. plankton and periphyton samples were collected in lotic and lentic waterbodies from the amazonian-andean region, the amazon river, japurá river and porvenir river basins during 1993, 1994, 2001 and 2003. at each sampling station ph, temperature, water transparency and conductivity were registered. samples were analyzed with phase contrast microscope (lm) and scanning electron microscope (sem). ten taxa are new records for the area; encyonema for the peruvian and colombian amazon and encyonopsis for the colombian sector. encyonema neogracile var. tenuipunctatum, e. vulgare, encyonopsis frequentis, gomphonema augur var. sphaerophorum and g. contraturris are recorded for the first time in colombia; encyonema venezolanum and g. neoapiculatum in colombia and peru and the latter also for amazonia. e. angustecapitatum was mentioned in colombia before at a pond located at 3000m asl. we describe a new species from porvenir river, amazonas, colombia: encyonema amazonianum. rev. biol. trop. 58 (1): 45-62. epub 2010 march 01.
Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales: Bacillariophyceae)
Amelia A Vouilloud,Silvia E Sala,Marcela Nú?ez Avellaneda,Santiago R Duque
Revista de Biología Tropical , 2010,
Abstract: Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales, Bacillariophyceae). The diatom flora of the Colombian and Peruvian Amazon is far less studied than the flora of the Brazilian sector of the basin. Here we present results related to the genera Encyonema, Encyonopsis and Gomphonema. Plankton and periphyton samples were collected in lotic and lentic waterbodies from the Amazonian-Andean region, the Amazon River, Japurá River and Porvenir River basins during 1993, 1994, 2001 and 2003. At each sampling station pH, temperature, water transparency and conductivity were registered. Samples were analyzed with phase contrast microscope (LM) and scanning electron microscope (SEM). Ten taxa are new records for the area; Encyonema for the Peruvian and Colombian Amazon and Encyonopsis for the Colombian Sector. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum and G. contraturris are recorded for the first time in Colombia; Encyonema venezolanum and G. neoapiculatum in Colombia and Peru and the latter also for Amazonia. E. angustecapitatum was mentioned in Colombia before at a pond located at 3000m asl. We describe a new species from Porvenir River, Amazonas, Colombia: Encyonema amazonianum. Rev. Biol. Trop. 58 (1): 45-62. Epub 2010 March 01. La flora diatomológica de la Amazonia Colombiana y Peruana está mucho menos estudiada que la flora del sector brasilero. Se presentan los resultados de los géneros Encyonema, Encyonopsis y Gomphonema. Muestras de plancton y perifiton fueron colectadas en ambientes lóticos y lénticos de la región amazónica-andina, en los ríos Amazonas, Japurá y Porvenir durante 1993, 1994, 2001 y 2003. En cada estación de muestreo se realizaron mediciones de pH, temperatura, transparencia del agua y conductividad. Las muestras fueron analizadas con microscopio óptico con contraste de fases y microscopio electrónico de barrido. Diez taxones son nuevos registros para el área; Encyonema en la Amazonia peruano-colombiana y Encyonopsis en el sector colombiano. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum y G. contraturris se reportan por primera vez en Colombia; Encyonema venezolanum y Gomphonema neoapiculatum en Colombia y Perú y la última también en la Amazonia. E. angustecapitatum fue previamente registrada en una laguna de altura en Colombia localizada a 3.000 msnm. Se describe una nueva especie, Encyonema amazonianum, colectada en el Río Porvenir, Amazonas,
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