Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 30 )

2018 ( 58 )

2017 ( 47 )

2016 ( 68 )

Custom range...

Search Results: 1 - 10 of 37741 matches for " Luis Vidal Ponce Cabrera "
All listed articles are free for downloading (OA Articles)
Page 1 /37741
Display every page Item
Laser-Induced Breakdown Spectroscopy (LIBS) Applied in the Differentiation of Arabica and Robusta Coffee  [PDF]
Abigail María Díaz Guerrero, Luis Vidal Ponce Cabrera, Teresa Flores Reyes, Rogelio Ortega Izaguirre
Optics and Photonics Journal (OPJ) , 2017, DOI: 10.4236/opj.2017.710018
Abstract: Coffee is one of the most consumed and commercialized crops in the world, which is why there is a potential risk to find arabica coffee (an expensive variety) adulterated with robusta coffee (a cheaper variety). The currently used technique for certifying coffee, High Performance Liquid Chromatography (HPLC), requires the sample to be subjected to a chemical treatment prior to analysis; in addition, the equipment is bulky and can not be moved easily. Laser Induced Breakdown Spectroscopy (LIBS) is a technique which does not require that samples be subjected to a chemical pretreatment, and equipment is small and portable, this can save valuable time in coffee trading. The purpose of this research was to demonstrate that LIBS can be applied to solve various problems related with the coffee authentication. Green coffee pills with different concentrations of arabica and robusta varieties were analyzed by LIBS, the results were used in the construction of calibration curves for the detection of the degree of simulated adulteration in coffee. It was found that the relative intensities of Ca (392.4 nm), Sr (407.1 nm), N (500.5 nm) and Na (588.7 nm), as well as the intensity ratios of Ca II (392.4 nm)/N I (500.5 nm), Sr I (407.1 nm)/N I (500.5 nm)and N I (500.5 nm)/Na I (588.7 nm) can be used for this purpose. It is concluded that the differentiation of coffee and the detection of its adulteration is possible with the use of LIBS. Further, with the use of an Artificial Neural Network (ANN) of type Multilayer Perceptron, it was possible to correctly classify the spectra of arabica and robusta roasted coffee.
Comparison on Morphological and Optical Properties of TiO2 Thin Films Grown by Single-Pulse and Multi-Pulse Laser Ablation  [PDF]
Yonic Pe?aloza-Mendoza, Luis Ponce-Cabrera
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2015, DOI: 10.4236/jsemat.2015.51002
Abstract: TiO2 thin films were prepared on glass substrates using the PLD (Pulsed Laser Deposition) technique. In order to carry out the ablation process, a Nd:YAG laser was used emitting in 1064 nm wavelength at 10 Hz repetition rate, set up for operating in both single-pulse and multi-pulse regimes. A comparison of the deposition rate, the optical and morphological properties of the layers obtained from both ablation regimes was made, which showed that the multi-pulsed ablation produced layers with a higher surface quality and better optical properties.
Krige Method Application for the Coverage Analysis of a Node-B in a WCDMA Network  [PDF]
Jazmín Ponce-Rojas, Sergio Vidal-Beltrán, José Luis López-Bonilla, Montserrat Jimenez-Licea
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2011, DOI: 10.4236/ijcns.2011.43022
Abstract: This paper shows the procedure and application of the Krige Method (or Kriging) for the analysis of the power level radiated by a Base Station (also called Node B), through a group of samples of this power level, measured at different positions and distances. These samples were obtained using an spectrum analyzer, which will allow to have georeferenced measurements, to implement the interpolation process and generate coverage maps, making possible to know the power level distribution and therefore understand the behavior and performance of the Node B.
Total and Local Quadratic Indices of the “Molecular Pseudograph’s Atom Adjacency Matrix”. Application to Prediction of Caco-2 Permeability of Drugs
Yovani Marrero Ponce,Miguel Angel Cabrera Pérez,Vicente Romero Zaldivar,Ernest Ofori,Luis A. Montero
International Journal of Molecular Sciences , 2003, DOI: 10.3390/i4080512
Abstract: The high interest in the prediction of the intestinal absorption for New Chemical Entities (NCEs) is generated by the increasing rate in the synthesis of compounds by combinatorial chemistry and the extensive cost of the traditional evaluation methods. Quantitative Structure–Permeability Relationships (QSPerR) of the intestinal permeability across the Caco-2 cells monolayer (PCaco-2) could be obtained by the application of new molecular descriptors. In this sense, quadratic indices of the “molecular pseudograph’s atom adjacency matrix” and multiple linear regression analysis were used to obtain good quantitative models to determine the PCaco-2. QSPerR models found are significant from a statistical point of view. The total and local quadratic indices were calculated with the TOMO-COMD software. A leave-one-out cross-validation procedure (internal validation) and the evaluation of external test set of 20 drugs (external validation) revealed that regression models had a good predictive power. A comparison with results derived from other theoretical studies shown a quite satisfactory behavior of the present method. The descriptors included in the prediction models permitted the interpretation in structural terms of the permeability process, evidencing the main role of H-bonding and size properties. The models found were used in virtual screening of drug intestinal permeability and a relationship between PCaco-2 calculated and percentage of human intestinal absorption for the 72 compounds was established. These results suggest that the proposed method is able to predict PCaco-2, being a good tool for screening of PCaco-2 for large sets of NCEs synthesized via combinatorial chemistry approach.
An alternative pathway for plant in vitro regeneration of chinaberry -tree Melia azedarach L. derived from the induction of somatic embryogenesis
Sharry,Sandra; Cabrera Ponce,José Luis; Herrera Estrella,Luis; Rangel Cano,Rosa María; Lede,Silvia; Abedini,Walter;
Electronic Journal of Biotechnology , 2006,
Abstract: a highly efficient somatic embryogenesis system and subsequent plant regeneration of chinaberry (melia azedarach l.) was developed. plants were regenerated from indirect somatic embryogenesis induction. novel features of this improved protocol, include: a) embryogenic callus induction with no addition of 2, 4-d in the culture media; b) somatic embryos differentiation was achieved by using high concentration of cytokinins (bap 10 mg/l) and adenine; c) 100% conversion of somatic embryos to plants was practically obtained and 100% of plants survived under greenhouse conditions; d) addition of putrescine improved somatic embryos germination. the amount of somatic embryos produced by the pathway of indirect somatic embryogenesis was 447 per gram of fresh weight callus. regenerated plants were phenotypically normal. the developed protocol established the potential to produce plantlets from cotyledon explants through somatic embryogenesis. it also presents itself as a highly efficient method for mass clonal propagation and conservation of melia azedarach.
Rese a de "La proliferación de los signos: la teoría social en tiempos de globalización" de Roberto Follari, Nilda Bistué y Claudia Yarza
Luis Ponce
Andamios , 2005,
Monitoring the Laser Ablation Process of Paint Layers by PILA Technique  [PDF]
Angel Eduardo Villarreal-Villela, L. Ponce Cabrera
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.69060
Abstract: The spectrum analysis obtained by Fast Fourier Transform of the Photoacoustic In-duced by Laser Ablation (PILA) during laser assisted paints removal process is de-scribed, in order to identify the presence of paint components on a metallic surface, optimize the ablation rate and propose the method as a cleaning process monitoring. The process was carried out using a low-cost experimental setup which includes a burst-mode Nd:YAG laser, an electret microphone, an audio amplifier device and an oscilloscope, to record the acoustic pulse and analyze it. The samples surface mor-phology was characterized by Optical Microscopy and Optical Coherence Tomography (OCT) before and after irradiation to visualize the formation of craters. As additional monitoring technique, the Laser Induced Breakdown Spectroscopy (LIBS) was used. The potential of the analysis for qualitative monitoring of coating removal was demonstrated due to the coincidence of the information provided by LIBS and PILA techniques.
The Potential of Compact Libs System with Multi-Pulse Nd:YAG Laser for Bacteria Identification  [PDF]
A. Ponce Flores, A. K. Frias Sanchez, A. Villarreal, F. G. Rendón Sauz, L. Ponce Cabrera, T. Flores Reyes
Journal of Biomedical Science and Engineering (JBiSE) , 2015, DOI: 10.4236/jbise.2015.83020
Abstract: This work shows the potential of a very compact, portable Laser Induced-Breakdown Spectroscopy (LIBS) system that includes low cost and compact Nd:YAG laser, intended for use in fieldwork identification of bacteria. This device allows for the generation of 2 - 4 pulses per laser shot, with a maximum energy of 120 mJ per pulse. Each pulse has a duration of 60 ns, and the total duration of the train of pulses is 180 μs. The device dimensions including the power supply are 50 × 20 × 140 cm, which indicates that can be utilized as a portable LIBS system in field conditions. The spectra captured on two different bacteria shows the capability of identification.
La adherencia en los morteros de alba ilería
Cabrera, Jorge Luis
Materiales de Construccion , 1995,
Abstract: The work presents a study carried out to determine the bond strength reached by bricklaying mortars at 28 days. 23 different dosages were prepared using 4 cement types, 2 sand types and 4 aggregate types. The results prove the feasibility of using the mentioned method to determine bond strength. The values at 28 days reached up to 0.7 MPa. Se hace un estudio para determinar la resistencia a la adherencia que alcanzan los morteros de alba ilería a los 28 días. Para ello se prepararon dosificaciones de morteros con 4 tipos de cementos, 2 tipos de arenas y 4 tipos de agregados, lográndose realizar 23 dosificaciones. Los resultados demuestran la factibilidad de emplear dicho método para determinar la resistencia a la adherencia. Se obtuvieron valores de hasta 0,7 MPa a los 28 días.
Ai' se ven: imagen y guadalupanismo otomí y chichimeca jonaz
Ferro Vidal, Luis Enrique;
Cuicuilco , 2009,
Abstract: what is attempted in this work is to characterize to the virgin from guadalupe like an aesthetic unit that it deciphers with more depth an íconos system that he/she explains and it expresses much more than the entirety of the work. see as an aesthetic unit and conformed by an íconos system it recreates us a world of images that you/ they leave the painting that you/ they energize and they offer a projection of a social life of the chichimeca jonaz in guanajuato, as well as the ???h? of the half-deserted queretano. to reach the fixed goal it is necessary to establish that this cultural phenomenon will be analyzed from the theory of the complexities where the history, the myth and the iconography will spill in a hearth to build a narrative of the image guadalupana in the social life of these two indigenous towns.
Page 1 /37741
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.