Guillermo Alatorre - Academia.edu (original) (raw)

Papers by Guillermo Alatorre

Se han estudiado cineticamente las reacciones de nitrosacion de la metil, etil, propil, butil y a... more Se han estudiado cineticamente las reacciones de nitrosacion de la metil, etil, propil, butil y alilurea. Los resultados experimentales y parametros calculados han conducido a unas ecuaciones cuya etapa cinetica lenta es la transferencia protonica de la nitrosourea protonada al disolvente agua. El estudio del efecto cinetico isotopico del disolvente ha conducido a valores de kh2o/kd2o comprendidos entre 4,1 y 5,5, concordantes con los calculados sobre la base del mecanismo propuesto. Se han calculado por via cinetica los valores del pk del acido nitroso, h2o y d2o que concuerdan bien con los medidos directamente. Se ha realizado un estudio cinetico sistematico de la influencia de la fuerza basica de diferentes aniones sobre las reacciones de nitrosacion. La catalisis basica observada es tambien coherente con el mecanismo que se propone. Las medidas del parametro de bronsted, ademas de confirmar el mecanismo de transferencia protonica, sugieren un estado de transicion simetrico entre...

World Journal of Microbiology and Biotechnology, 2010

Gibberellic acid has been known since 1954 but its effect on rice still remains very important in... more Gibberellic acid has been known since 1954 but its effect on rice still remains very important in the agricultural world. Gibberellic acid (GA 3) is the main secondary metabolite produced by the Gibberella fujikuroi fungus. This hormone is of great importance in agriculture and the brewing industry, due to its fast and strong effects at low concentrations (lg) on the processes of growth stimulation, flowering, stem elongation, and germination of seeds, among others. Plant promoters of growth production such as the gibberellins, especially the GA 3 are a priority in obtaining better harvests in the agricultural area and by extension, improving the food industry. Three routes to obtaining GA 3 have been reported: extraction from plants, chemical synthesis and microbial fermentation. The latter being the most common method used to produce GA 3. In this investigation, glucose-corn oil mixture was used as a carbon source on the basis of 40 g of carbon in a 7 L stirred tank bioreactor. A pH of 3.5, 29°C, 600 min-1 agitation and 1 vvm aeration were maintained and controlled with a biocontroller connected to the bioreactor, throughout the entire culture time. The carbon source mixture affected the fermentation time as well as the production of the GAs. The production of 380 mg GA 3 L-1 after 288 h of fermentation was obtained when the glucose-corn oil mixture was employed contrasting the 136 mg GA 3 L-1 at 264 h of culture when only glucose was used.

World Journal of Microbiology and Biotechnology, 2006

2. Case I. Hydrodynamics, mass transfer and rheological studies of gibberellic acid production in... more 2. Case I. Hydrodynamics, mass transfer and rheological studies of gibberellic acid production in an airlift bioreactor 2.1 Introduction Gibberellic acid is an endogenous hormone in higher plants, belonging to the group of gibberellins, and also a product of the secondary metabolism in certain fungi. Approximately 126 gibberellins have been characterized (Tudzynski 1999; Shukla et al. 2003) but only a few are commercially available. Gibberellic acid is the most important and its effects on higher plants are: marked stem elongation, reversal of dwarfism, promotion of fruit setting, breaking of dormancy, acceleration of seed fermentation, among others (Bru¨ ckner and Blechschmidt 1991; Tudzynski 1999). Currently, gibberellic acid is microbiologically produced in a submerged culture (SmF) fashion but another fermentation techniques such as solid sate fermentation or with immobilized mycelium are also reported (

World Journal of Microbiology & Biotechnology, 1999

Strain H-984 of G. fujikuroi grown for 38?h in a shake flask with medium containing 20?g glucose ... more Strain H-984 of G. fujikuroi grown for 38?h in a shake flask with medium containing 20?g glucose l-1, 3?g yeast extract l-1, 2.5?g NH4NO3 l-1, 0.5?g KH2PO4 l-1, 0.1?g MgSO4 l-1, 1?g CaCO3 l-1, and inoculated into a bioreactor with medium containing 60?g glucose l-1; 1?g NH4Cl l-1; 3?g KH2PO4 l-1 and 1.5?g MgSO4 l-1 produced 1100?mg gibberellic acid l-1.

A series of kinetic experiments for the nitrosation of dimethylurea is presented. The required re... more A series of kinetic experiments for the nitrosation of dimethylurea is presented. The required reagents are inexpensive and reaction progress is followed using a double-beam recording spectrophotometer. The objective of the experiments is for students to obtain the reaction order and the rate constant using both a differential and an integral procedure, examine the effect of proton concentration on the reaction rate constant, deduce the theoretical rate equation from the proposed reaction mechanism, and analyze the effect of temperature on the reaction rate constant. The experimental results fit, with high linear correlation factors, the equations deduced for both differential and integral methods, presenting an excellent opportunity to learn the principles of chemical kinetics and analysis of the reaction mechanism. This paper presents a series of experiments that enable students to compare results obtained using two common methods for analyzing chemical kinetics, the integral meth...

Journal of Food Measurement and Characterization

Materials Chemistry and Physics

Journal of Applied Polymer Science

Food and Bioproducts Processing

Food and Bioproducts Processing, 2016

Zeitschrift Fur Physikalische Chemie, 2001

A fuel-rich, non-sooting (C/O = 0.773) 1-pentene/oxygen/argon flame is studied experimentally at ... more A fuel-rich, non-sooting (C/O = 0.773) 1-pentene/oxygen/argon flame is studied experimentally at 50 mbar. The results are compared to computations. The calculations show satisfactory agreement with the data obtained from the measurements. The main channels for 1-pentene decomposition are presented and discussed in view of previous data for a propene flame at similar experimental conditions. Special emphasis is directed towards the formation of the first aromatic ring and the further growth of small aromatic hydrocarbons. By reaction flow analysis, it is found that the major reaction channel for benzene formation results from the recombination of propargyl radicals. Furthermore, the major reaction channels for naphthalene formation are presented.

Computers & Chemical Engineering, 2015

Food Chemistry, 2015

N-nitrosamines (NAms) are highly active carcinogens that have been detected in food and beverages... more N-nitrosamines (NAms) are highly active carcinogens that have been detected in food and beverages. Currently certain studies report their presence in red wine, while others fail to detect their presence. In this study the head space solid phase micro-extraction technique coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) was applied to quantify four NAms in different types of red wine. The technique was found to be a simple, precise, fast and environmentally friendly alternative for the quantification of volatile NAms. A factorial analysis was carried out to evaluate the influence of the parameters on the HS-SPME technique. This is the first study that such analysis has been reported and where NAms in red wine have been quantified using HS-SPME-GC-MS. The method was validated by calculating the linearity, limit of detection and quantification. Two of the four NAms analyzed were found to be present in red wine samples.

Soot formation is still one of the most pressing problems in combustion. Chemical mechanisms have... more Soot formation is still one of the most pressing problems in combustion. Chemical mechanisms have been established which need to be examined in detail under laboratory conditions. Some of the main pathways concerning the formation of soot precursors are still under debate. While it seems commonly accepted that some of the dominant routes may be fuel-specific, experimental data and their comparison with kinetic models for fuels with more than 3 C atoms are scarce. This article will present an overview of the work pursued in Bielefeld on the characterisation of fuel-rich flames by a combination of laser spectroscopy and mass spectrometry.

Food and Bioproducts Processing, 2015

Surface and Coatings Technology, 2015

ABSTRACT The protective effect of a hydrophobic surface against acid erosion was validated in the... more ABSTRACT The protective effect of a hydrophobic surface against acid erosion was validated in the present work using octadecyltrichlorosilane (OTS) on hydroxyapatite films (HA) and on dental samples. The acid erosion was firstly evaluated on films made of HA and fluorapatite (HAF), and subsequently on films of HA coated by OTS. Our results have shown that the two first films were completely eroded during this evaluation and that no significant erosion was observed for the last film. Indeed, teeth coated with OTS showed no erosion at all after seven days of exposure to citric acid. The evaluation was based on QCM-D measurements, SEM images and water contact angle characterization. The results validate that a hydrophobic surface may be an effective tooth protector against acid erosion.

Computer Aided Chemical Engineering, 2010

ABSTRACT Mathematical modeling as a tool for the treatment of a pathogenic disease has been widel... more ABSTRACT Mathematical modeling as a tool for the treatment of a pathogenic disease has been widely proposed in the literature. Most of the modeling approaches represent the immune system dynamics as deterministic optimal control problems. Deterministic approaches, however, do not consider uncertainties in model parameters and variability among different individuals. To include uncertainties in the formulation, the aim of this paper has been using stochastic optimal control theory to develop protocols for the treatment of human diseases. We model time dependent uncertainties as Ito processes. That results in an optimal control problem where the constraints are stochastic differential equations and the objective function is an integral equation. The optimality conditions of the problem are obtained through the stochastic maximum principle, which results in a boundary value problem. The boundary value problem is solved iteratively by using a combination of the gradient method and a stochastic version of the Runge-Kutta method derived in this work. As an illustration of the proposed approach, we solve a mathematical model to determine the evolution of a generic disease and obtain regimens for applying therapeutic agents in a manner that maximizes efficacy while minimizing side effects. We show that stochastic optimal control theory can indeed help develop clinical insight in treating illness under uncertainties in model parameters.

World Journal of Microbiology and Biotechnology, 2009

Some process has been proposed for azo dye degradation and anaerobic bioreactors are one of them,... more Some process has been proposed for azo dye degradation and anaerobic bioreactors are one of them, since for their reduction, the dye has to be the electron acceptor. An anaerobic fixed bed bioreactor packed with activated carbon (AC) is proposed to degradate the Reactive Red 272 azo dye. In the present paper a dye degradation mechanism in an anaerobic environment is explained. It is very important to consider the interaction dye-microorganism-AC, because the groups in the AC surface take part in the reaction besides being an excellent carrier for microorganism and an adsorbent for the dye. The aromatic compounds produced in the dye reduction are partially degraded as a function of inlet dye concentration and reactor residence time. In anaerobic environment the aromatic compounds are decomposed through hydroxylation, carboxylation and redox reactions, due to enzymatic reactions.