Cesar Velazquez

Learn More
The insecticidal effects of nortriterpene quinone methides (pristimerin, tingenonee, and 20-alpha-hydroxytingenone) are reported for the first time. The natural products were isolated from Maytenus sp. (Celastraceae) and their effects tested on larvae of codling moth (Cydia pomonella, Lepidoptera: Tortricidae). The three metabolites produce the same effects(More)
15alpha-Hydroxy-21-keto-pristimerine (1), a new nortriterpene quinone methide was isolated from the root bark of Maytenus catingarum along with other well-known related compounds, including pristimerine (2), tingenone, and 20alpha-hydroxy-tingenone. The structure of 1 was determined by means of 1H and 13C NMR spectroscopy, including homonuclear and(More)
Simulations provide us with physically correct motions and believable features for effects elements. However, when creating more stylized and unique effects animation, we frequently need more art-directible and manageable tool sets. This session presents a detailed overview of specific non-simulation based approaches we developed for the ice cream effects(More)
Fumonisins are produced by several fungal species that are common contaminants of maize. The most abundant naturally occurring fumonisin, fumonisin B1 (FB1), has been shown to induce several animal disease syndromes. The development of analytical methods is therefore important. A new method is described that integrates extraction and purification of maize(More)
Contamination studies by ochratoxin A on pork kidney and chicken liver has been carried out in Catalonia (Spain). 73% of the pork kidney samples analyzed did not contain an amount of ochratoxin A over our detection limit (0.5 ng/g) whereas only 7% had contamination higher than 1 ng/g. None of the chicken samples analyzed were contaminated by this toxin(More)
The prolamins (zeins) are the main storage proteins in the maize grain. There are limited investigations related to their participation on tortilla texture. For determining their effect, normal (6) and Quality Protein Maize (QPM) (6) genotypes were used. The chemical variables comprised prolamins, amylose and starch in whole grain and endosperm. Viscosity(More)
A sensitive and reliable method is described for the determination of ochratoxin A (OTA) in maize. An extraction and clean-up procedure was used, with chloroform-phosphoric acid as the extractant, and liquid-liquid partition and anion-exchange chromatography (SAX columns) for the clean-up. Quantification of toxin is achieved by high performance liquid(More)
The effect of several solvent systems on the chromatographic response of fumonisin B1 and B2 derived with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AccQ.Fluor) is described. Naturally contaminated corn samples were extracted and purified by a standard method. Then, samples were dissolved in different solvents, derived with AccQ.Fluor reagent and(More)
— There are few documented experiences on the massive development of learning objects using well-defined quality standards, this article presents a case of study for the development of 184 learning objects produced to support 13 undergraduate courses, each of the learning objects has in its development well defined quality parameters and was created in the(More)
This article presents a quality management process which integrates a service approach for the learning objects development. First we present the basic concepts of quality management and service theory. Also the paper presents a quality management process which integrates a services approach for the learning objects development, explaining how to determine(More)
  • 1