Papers by Erick Rodriguez
Revista UIS Ingenierías, 2022
Una desventaja del uso de biodiésel es su precio, debido a los altos costos de la materia prima y... more Una desventaja del uso de biodiésel es su precio, debido a los altos costos de la materia prima y al acondicionamiento del aceite requerido para obtenerlo por medio de una transesterificación tradicional, lo que le impide alcanzar precios más accesibles y dificulta su competitividad con el diésel de petróleo. Por esta razón, se investigó una alternativa para la obtención de biodiésel mediante transesterificación in situ o extracción reactiva (ER) a partir de semillas de Jatropha curcas L. Con esta alternativa en auge, que no compite con el mercado alimenticio, se busca reducir etapas en el proceso de producción y así disminuir costos de operación respecto al método y aceites convencionales. Se determinó la influencia de la temperatura, concentración másica de catalizador (g NaOH/g aceite) y relación molar metanol:aceite, con el fin de maximizar el rendimiento y la concentración de FAME del biodiésel obtenido, mediante un diseño experimental central compuesto (DCC) con método de supe...
La ensenanza de diferentes disciplinas tecnicas y cientificas requiere de la realizacion de exper... more La ensenanza de diferentes disciplinas tecnicas y cientificas requiere de la realizacion de experimentos para consolidar los conceptos teoricos vistos en las aulas. El entorno tecnologico que ofrece Internet, en conjunto con el ambito educativo, se han combinado en las instituciones educativas para brindarles a los estudiantes nuevas formas de aprender y acceso a infraestructuras remotas para realizar experimentos. En este documento se presenta la propuesta de un ambiente de experimentacion remota para mejorar el aprendizaje de materias experimentales, como es el caso de la robotica movil. Los experimentos que se pueden realizar con esta herramienta consisten en probar diferentes estrategias para realizar el recorrido de un laberinto desde un punto inicial a uno final con la ayuda de los sensores infrarrojos del robot y mediante un algoritmo de control hecho en Java. El sistema le brinda al usuario informacion del ambiente remoto por medio de imagenes y datos con los que se puede ob...
Quantitative Evaluation of Enhanced Multi-plane Clinical Fetal Diffusion MRI with a Crossing-Fiber Phantom
Computational Diffusion MRI, 2021
Frontiers in Neuroscience, 2019
Statistical analysis of brain tissue images in the wavelet domain: Wavelet-based morphometry
NeuroImage, 2013
Wavelet-based methods have been developed for statistical analysis of functional MRI and PET data... more Wavelet-based methods have been developed for statistical analysis of functional MRI and PET data, where the wavelet transformation is employed as a tool for efficient signal representation. A number of studies using these approaches have reported better estimation capabilities, in terms of increased sensitivity and specificity, than the standard statistical analyses in the spatial domain. In line with these previous studies, the present report proposes a statistical analysis in the wavelet domain for the estimation of inter-group differences from structural MRI data. The procedure, called wavelet-based morphometry (WBM), was implemented under a voxel-based morphometry (VBM) style analysis. It was evaluated by comparing the gray-matter images of a group of 32 healthy subjects whose images were artificially altered to induce thinning of the cortex, with a different group of 32 healthy subjects whose images were unaltered. In order to quantify the performance of the reconstruction from a practical perspective, the same comparison was also conducted with standard VBM using SPM's Gaussian random fields and FSL's cluster-based statistics, family-wise error corrected, for datasets spatially-normalized via two different registration methods (i.e., SyN and FNIRT). The effect of using different amounts of smoothing, Battle-Lemarié filters and resolution levels in the wavelet transform was also investigated. Results support the proposed approach as a different and promising methodology to assess the structural morphometric differences between different populations of subjects.
Epilepsy Research, 2014
The aim of this study was to identify differential global and local brain structural patterns in ... more The aim of this study was to identify differential global and local brain structural patterns in Dravet Syndrome (DS) patients as compared with a control subject group, using brain morphometry techniques which provide a quantitative whole-brain structural analysis that allows for specific patterns to be generalized across series of individuals. Nine patients with the diagnosis of DS that tested positive for mutation in the SCN1A gene and nine well-matched healthy controls were investigated using voxel brain morphometry (VBM), cortical thickness and cortical gyrification measurements. Global volume reductions of gray matter (GM) and white matter (WM) were related to DS. Local volume reductions corresponding to several white matter regions in brainstem, cerebellum, corpus callosum, corticospinal tracts and association fibers (left inferior fronto-occipital fasciculus and left uncinate fasciculus) were also found. Furthermore, DS showed a reduced cortical folding in the right precentral gyrus. The present findings describe DS-related brain structure abnormalities probably linked to the expression of the SCN1A mutation.
2012 26th International Conference on Advanced Information Networking and Applications Workshops, 2012
This paper studies QoE (Quality of Experience) in Multi-View Video and Audio (MVV-A) transmission... more This paper studies QoE (Quality of Experience) in Multi-View Video and Audio (MVV-A) transmission over IP networks where the users change the viewpoint by request. It jointly analyzes the effects of user interfaces for viewpoint change and contents in conjunction with network performance in a multidimensional way. In order to assess the QoE, we perform a subjective experiment which employs two user interfaces and two contents (a dog doll and a toy train). The assessors are instructed to follow the movement of the object in the content and evaluate the MVV-A system. As a result, we have found that even if the user feels comfortable with the user interface, QoE deteriorates when the load traffic is very high and the playout buffering time cannot absorb the delay jitter properly. The speed of the movement of the object in the content, and the similarity of the views of the cameras can affect users' perception of the viewpoint change response. We realized that in order to achieve high QoE, we need to employ a user interface that enables the users to change the viewpoint easily according to the object's movement.
2009 15th Asia-Pacific Conference on Communications, 2009
This paper investigates QoE (Quality of Experience) of MVV (Multi-View Video) and audio transmiss... more This paper investigates QoE (Quality of Experience) of MVV (Multi-View Video) and audio transmission over IP networks. Unlike previous works that mainly discuss MVV transmission from aspects of video codecs, we study MVV and audio transmission under various IP traffic and delay conditions by experiment. We compare two schemes: a scheme that the user watches a single viewpoint, and the one that he/she can choose one viewpoint from many viewpoints. At the same time, we perform a user study which helps us to understand the user behavior in the MVV system under those conditions. As a result, we show that high QoE can be achieved when the user can change the viewpoint with low load traffic and delay.
PLoS ONE, 2011
Neuroimaging classification procedures between normal and pathological subjects are sparse and hi... more Neuroimaging classification procedures between normal and pathological subjects are sparse and highly dependent of an expert's clinical criterion. Here, we aimed to investigate whether possible brain structural network differences in the shiverer mouse mutant, a relevant animal model of myelin related diseases, can reflect intrinsic individual brain properties that allow the automatic discrimination between the shiverer and normal subjects. Common structural networks properties between shiverer (C3Fe.SWV Mbp shi /Mbp shi , n = 6) and background control (C3HeB.FeJ, n = 6) mice are estimated and compared by means of three diffusion weighted MRI (DW-MRI) fiber tractography algorithms and a graph framework. Firstly, we found that brain networks of control group are significantly more clustered, modularized, efficient and optimized than those of the shiverer group, which presented significantly increased characteristic path length. These results are in line with previous structural/functional complex brain networks analysis that have revealed topologic differences and brain network randomization associated to specific states of human brain pathology. In addition, by means of network measures spatial representations and discrimination analysis, we show that it is possible to classify with high accuracy to which group each subject belongs, providing also a probability value of being a normal or shiverer subject as an individual anatomical classifier. The obtained correct predictions (e.g., around 91.6-100%) and clear spatial subdivisions between control and shiverer mice, suggest that there might exist specific network subspaces corresponding to specific brain disorders, supporting also the point of view that complex brain network analyses constitutes promising tools in the future creation of interpretable imaging biomarkers.
NeuroImage, 2008
Our goal is to study the human brain anatomical network. For this, the anatomical connection prob... more Our goal is to study the human brain anatomical network. For this, the anatomical connection probabilities (ACP) between 90 cortical and subcortical brain gray matter areas are estimated from diffusionweighted Magnetic Resonance Imaging (DW-MRI) techniques. The ACP between any two areas gives the probability that those areas are connected at least by a single nervous fiber. Then, the brain is modeled as a non-directed weighted graph with continuous arc weights given by the ACP matrix. Based on this approach, complex networks properties such as small-world attributes, efficiency, degree distribution, vulnerability, betweenness centrality and motifs composition are studied. The analysis was carried out for 20 right-handed healthy subjects (mean age: 31.10, S.D.: 7.43). According to the results, all networks have small-world and broad-scale characteristics. Additionally, human brain anatomical networks present bigger local efficiency and smaller global efficiency than the corresponding random networks. In a vulnerability and betweenness centrality analysis, the most indispensable and critical anatomical areas were identified: putamens, precuneus, insulas, superior parietals and superior frontals. Interestingly, some areas have a negative vulnerability (e.g. superior temporal poles, pallidums, supramarginals and hechls), which suggest that even at the cost of losing in global anatomical efficiency, these structures were maintained through the evolutionary processes due to their important functions. Finally, symmetrical characteristic building blocks (motifs) of size 3 and 4 were calculated, obtaining that motifs of size 4 are the expanded version of motif of size 3. These results are in agreement with previous anatomical studies in the cat and macaque cerebral cortex.
QoE Assessment of Multi-View Video and Audio IP Transmission
IEICE Transactions on Communications, 2010
Page 1. IEICE TRANS. COMMUN., VOL.E93B, NO.6 JUNE 2010 1373 PAPER Special Section on Quality of ... more Page 1. IEICE TRANS. COMMUN., VOL.E93B, NO.6 JUNE 2010 1373 PAPER Special Section on Quality of Communication Networks and Services QoE Assessment of Multi-View Video and Audio IP Transmission Erick JIMENEZ ...
Cerebral Cortex, 2010
Evidence for interregional structural asymmetries has been previously reported for brain anatomic... more Evidence for interregional structural asymmetries has been previously reported for brain anatomic regions supporting welldescribed functional lateralization. Here, we aimed to investigate whether the two brain hemispheres demonstrate dissimilar general structural attributes implying different principles on information flow management. Common left hemisphere/right hemisphere structural network properties are estimated and compared for right-handed healthy human subjects and a nonhuman primate, by means of 3 different diffusion-weighted magnetic resonance imaging fiber tractography algorithms and a graph theory framework. In both the human and the nonhuman primate, the data support the conclusion that, in terms of the graph framework, the right hemisphere is significantly more efficient and interconnected than the left hemisphere, whereas the left hemisphere presents more central or indispensable regions for the whole-brain structural network than the right hemisphere. From our point of view, in terms of functional principles, this pattern could be related with the fact that the left hemisphere has a leading role for highly demanding specific process, such as language and motor actions, which may require dedicated specialized networks, whereas the right hemisphere has a leading role for more general process, such as integration tasks, which may require a more general level of interconnection.
Molecular phylogenetics and evolution, Aug 21, 2017
Current hypotheses of relationship among the species of the fruit fly genera Anastrepha and Toxot... more Current hypotheses of relationship among the species of the fruit fly genera Anastrepha and Toxotrypana are tested using sequence data from six DNA regions: the mitochondrial regions 16S, CAD, and COI, and the nuclear regions EF1a, PER, and PGD. DNA sequences were obtained from 146 species of Anastrepha, representing 19 of the 21 species groups as well as five of the six clades of the robusta group, and four species of Toxotrypana in addition to species of Hexachaeta, Pseudophorellia, Alujamyia, and 13 other tephritid genera used as outgroups. The results indicate that Hexachaeta is more closely related to the Molynocoelia group than to Toxotrypana and Anastrepha, and it is removed from the tribe Toxotrypanini. The group Anastrepha+Toxotrypana and the genus Toxotrypana are strongly supported as monophyletic, consistent with previous studies, but Toxotrypana arises within Anastrepha, confirming that Anastrepha as currently defined is paraphyletic. The placement of Toxotrypana within ...
Uploads
Papers by Erick Rodriguez