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Rodriguez-Marin M.L.,National Polytechnic Institute of Mexico | Bello-Perez L.A.,National Polytechnic Institute of Mexico | Yee-Madeira H.,Escuela Superior de Fisica y Matematicas IPN | Zhong Q.,University of Tennessee at Knoxville | Gonzalez-Soto R.A.,National Polytechnic Institute of Mexico
Materials Science and Engineering C | Year: 2013

Rice and banana flours are inexpensive starchy materials that can form films with more improved properties than those made with their starch because flour and starch present different hydrophobicity. Montmorillonite (MMT) can be used to further improve the properties of starch-based films, which has not received much research attention for starchy flours. The aim of this work was to evaluate the mechanical and barrier properties of nanocomposite films of banana and rice flours as matrix material with addition of MMT as a nanofiller. MMT was modified using citric acid to produce intercalated structures, as verified by the X-ray diffraction pattern. The intercalated MMT was blended with flour slurries, and films were prepared by casting. Nanocomposite films of banana and rice flours presented an increase in the tensile at break and elongation percentage, respectively, more than their respective control films without MMT. This study showed that banana and rice flours could be alternative raw materials to use in making nanocomposite films. © 2013 Elsevier B.V.

Perez-Moret Y.,University of Habana | Martinez J.A.,University of Habana | Hernandez M.P.,University of Habana | Abad J.O.,University of Habana | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

A design of a scatterometer is described for applications of Mie theory. The instrument comprises a goniometer, a lock-in amplifier, a laser, and a photomultiplier tube (PMT). An embedded control programmable hardware and Windows-based Virtual Instruments simplify the design of automation of the scatterometer. The software has been modularly designed to provide independent control of the stepper motor for the motion of goniometer arm, running and on-line displaying of angular scans, auto storage of the angular scan data. The obtained benefits include facilitation of advanced data-collection techniques and collection of higher quality data. Quasimonodisperse particle of the latex have been characterized with this set up. The measured size particles are close to the reported nominal values. This result indicated that the experimental setup warrants adequate quality measurement, which allows a reasonable solution to inverse problem. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Yee-Madeira H.,Escuela Superior de Fisica y Matematicas IPN
Journal of Agricultural and Food Chemistry | Year: 2011

Banana starch was chemically modified using single (esterification or cross-linking) and dual modification (esterification-cross-linking and cross-linking-esterification), with the objective to increase the slowly digestible starch (SDS) and resistant starch (RS) concentrations. Physicochemical properties and in vitro digestibility were analyzed. The degree of substitution of the esterified samples ranged from 0.006 to 0.020. The X-ray diffraction pattern of the modified samples did not show change; however, an increase in crystallinity level was determined (from 23.79 to 32.76%). The ungelatinized samples had low rapidly digestible starch (RDS) (4.23-9.19%), whereas the modified starches showed an increase in SDS (from 10.79 to 16.79%) and had high RS content (74.07-85.07%). In the cooked samples, the esterified starch increased the SDS content (21.32%), followed by cross-linked starch (15.13%). Dual modified starch (cross-linked-esterified) had the lowest SDS content, but the highest RS amount. The esterified and cross-linked-esterified samples had higher peak viscosity than cross-linked and esterified-cross-linked. This characteristic is due to the fact that in dual modification, the groups introduced in the first modification are replaced by the functional group of the second modification. Temperature and enthalpy of gelatinization decreased in modified starches (from 75.37 to 74.02 °C and from 10.42 to 8.68 J/g, respectively), compared with their unmodified starch (76.15 °C and 11.05 J/g). Cross-linked-esterified starch showed the lowest enthalpy of gelatinization (8.68 J/g). Retrogradation temperature decreased in modified starches compared with unmodified (59.04-57.47 °C), but no significant differences were found among the modified samples. © 2011 American Chemical Society.

Yee-Madeira H.,Escuela Superior de Fisica y Matematicas IPN
Plant Foods for Human Nutrition | Year: 2010

Fresh and stored maize (white and blue) tortillas were evaluated for physicochemical, rheological and structural characteristics assessed by calorimetry, x-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, dynamic viscoelastic tests, and high-performance sizeexclusion chromatography. Two endotherms were found in studies of fresh and stored tortillas. The low temperature endotherm (50-56 °C) was due to reorganized (retrograded) amylopectin, while the high temperature endotherm (105-123 °C) was attributed to retrograded amylose. The enthalpy value for the lower temperature transition was minor than that of the high temperature transition. Fresh tortillas showed an amorphous starch arrangement by x-ray diffraction study. Stored samples showed the presence of peaks at 2θ = 17° and 23°, indicating re-crystallization of starch components. FTIR results confirmed the development of higher levels of starch crystals during storage. Differences in the viscoelastic parameters were also observed between fresh and stored samples. At the longest storage times, white tortillas were more rigid than blue tortillas. Molar mass values for starch increased for both white and blue tortillas as storage time progressed, though relatively higher values were obtained for white tortillas. More starch reorganization occurred in white tortillas, in accordance to calorimetric, x-ray diffraction, FTIR and rheological results. These results corroborate that changes occurring in tortillas during storage are related to reorganization of starch components, and the maize variety more than the color plays an important role. © 2010 Springer Science+Business Media, LLC.

Vigil-Galan O.,Escuela Superior de Fisica y Matematicas IPN | Courel M.,Escuela Superior de Fisica y Matematicas IPN | Cruz-Gandarilla F.,Escuela Superior de Fisica y Matematicas IPN | Seuret-Jimenez D.,Autonomous University of the State of Morelos
Journal of Materials Science: Materials in Electronics | Year: 2016

In this work, the results about the properties of CdTe:Bi thin films grown by the Closed Space Vapor Transport (CSVT) method are presented. Two procedures were developed for the CdTe:Bi films deposition: (a) using powders with different Bi concentrations at a constant pressure in the CSVT chamber and (b) varying the total final Ar pressure in the CSVT chamber. The CdTe powders used in our experimental conditions were obtained by using CdTe:Bi crystals grown by the vertical Bridgman method, varying the nominal Bi-dopant concentration in the 1.0 × 1017 to 4 × 1019 at/cm3 range. Finally, the possible influence of both parameters on the existence of an intermediate band in CdTe:Bi thin films and CdS/CdTe solar cell characteristics is analyzed. © 2016 Springer Science+Business Media New York

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