Javier Gonzalez Castellanos - Academia.edu (original) (raw)

Papers by Javier Gonzalez Castellanos

Revista UIS Ingenierías, 2017

Existe evidencia que asocia el dolor lumbar con la postura sedente. Para contrarrestar estos efec... more Existe evidencia que asocia el dolor lumbar con la postura sedente. Para contrarrestar estos efectos, se ha estudiado los beneficios de bascular el asiento en actividades de conducción, sin embargo se ha encontrado que no existen estudios en trabajo de oficina. Objetivo: Evaluar la influencia del asiento basculante en la percepción de dolor lumbar. Materiales y métodos: se plantearon dos tratamientos: a) asiento con basculación y b) asiento sin basculación; estudiados en cuatro tareas de oficina: leer, escribir a mano, digitar y navegar en internet. Como respuesta se midió la actividad muscular del tronco, la postura de la espalda, el tiempo y el número de errores. Resultados: En las tareas de digitar, navegar en internet y leer existe una diferencia significativa, es decir que la basculación influye en el comportamiento postural y en el tiempo productivo. Conclusiones: Estudiar variables como la presión del asiento para encontrar mayor evidencia.

Revista UIS Ingenierías, 2017

When ergonomic criteria are separately applied to the design of chairs, the feeling of comfort is... more When ergonomic criteria are separately applied to the design of chairs, the feeling of comfort is not guaranteed. In this case, the aesthetic and perceptive features of the chair provide the sensations of comfort, and several studies have determined that comfort and discomfort present some characteristics that make them different from each other. Moreover, early perceptions by the user remain invariable when there is no interaction between the person and the object. Therefore, it can be assumed that if a device is considered comfortable after an initial experience of use, it may well not be thought as such after extended use. Based on this, the present research study aimed at establishing the differences in the perceptions of comfort of two chairs before and after extended sitting posture. Six subjects participated in this study, all they were women from 20 to 45 years of age, who usually perform office work in extended sitting posture, with a body mass index (BMI) ranging between 20 and 30 Kg/m2. In the experiment, four office tasks were assigned (reading, transcribing a text, handwriting and searching on the internet) during sixty minutes. The experiment was divided into two sessions, to use the two chairs subject of the study. Each participant was assessed at the same hour but on two different days. By means of the semantic differential, evaluations of visual perception were carried out by the participants before and after using the chair. The results reveal differences in the perception evaluation of both chairs before and after their use. In the case of the chair a, the assessment of the adjectives never decreased. This study shows that the pleasure provided by a product is not static and it does evolve by product time of use and manipulation. Even though there were no statistical differences in the adjective pairs studied when only one chair was examined, it was demonstrated that its perception might improve or worsen on the basis of time. Similarly, this perceptual behavior is not indifferent to the object, finding significant differences before and after use when comparing the chairs. Finally, this analysis tool provides better evidence on product functionality by indicating whether there are failures in the proposed design.

Revista Ciência da Madeira - RCM, 2020

RESUMEN Existe evidencia empírica de que la madera laminada, comparativamente con la madera sólid... more RESUMEN Existe evidencia empírica de que la madera laminada, comparativamente con la madera sólida mejora su densidad aparente y su módulo de elasticidad. El objetivo de la investigación fue determinar la densidad, la velocidad de onda y el módulo dinámico por ondas de esfuerzo en madera sólida y laminada de Enterolobium cyclocarpum, Tabebuia rosea y Juglans pyriformis. Se elaboraron probetas de madera sólida y laminada de pequeñas dimensiones y se realizaron pruebas de ondas de esfuerzo. La densidad aparente de la madera laminada, en comparación con la de la madera sólida, se incrementa para las tres especies. En cambio, el módulo dinámico de la madera laminada aumenta para Enterolobium cyclocarpum y Tabebuia rosea, pero disminuye para Juglans pyriformis. La variabilidad de la densidad aparente, la velocidad de onda y el módulo dinámico, aumentan o disminuyen según se trate de la especie y o del parámetro en cuestión. Los resultados son válidos para el caso de laminado de pequeñas probetas de las especies estudiadas. Para su aplicación a proyectos de ingeniería, es recomendable realizar estudios ex profeso. Palabras clave: densidad aparente; velocidad de onda; módulo dinámico. Mechanical characterization by stress waves of the laminated wood of three angiosperm species ABSTRACT There is empirical evidence that laminated wood, compared to solid wood, improves its bulk density and modulus of elasticity. The objective of the research was to determine the apparent density, the wave velocity and the dynamic modulus by stress waves in solid and laminated wood of Enterolobium cyclocarpum, Tabebuia rosea and Juglans pyriformis. Solid and laminated wood specimens of small dimensions were prepared, and stress wave tests were carried out. The apparent density of laminated wood, in comparison with that of solid wood, increases for all three species. In contrast, the dynamic modulus of laminated wood increases for Enterolobium cyclocarpum and Tabebuia rosea but decreases for Juglans pyriformis. The variability of the apparent density, the wave velocity and the dynamic modulus, increases or decreases depending on the species and/or parameter in question. The results are valid for the case of laminated small specimens of the species studied. For its application to engineering projects, it is advisable to carry out ex profeso studies.

Información tecnológica, 2019

Se presenta evidencia que asocia la influencia de los asientos dinámicos con el tiempo productivo... more Se presenta evidencia que asocia la influencia de los asientos dinámicos con el tiempo productivo en trabajos de oficina. Veintiocho mujeres voluntarias participaron en el experimento que se realizó mediante el planteamiento de dos situaciones a) con basculación del asiento y b) sin basculación del asiento, en cuatro tareas de oficina: leer, escribir a mano, navegar en internet y digitar. En el estudio se midió el tiempo productivo y el número de errores. Se encontró que los asientos dinámicos no afectan significativamente el desempeño de los trabajadores. Por el contrario, los análisis descriptivos muestran mejores tiempos productivos y reducción en el número de errores. Se sugiere que la incorporación de asientos dinámicos debería ser un requerimiento importante en el diseño de sillas para oficina. Se ha demostrado que ellos disminuyen la incomodidad debida al dolor lumbar y contribuye a mejorar el rendimiento en el trabajo.

Revista UIS Ingenierías, 2019

La tecnología es responsable de la transformación del hombre y de la humanidad; es una respuesta ... more La tecnología es responsable de la transformación del hombre y de la humanidad; es una respuesta innata al empeño de los individuos por vivir en el mundo y "estar bien". No obstante, el crecimiento económico de las nacionesentendido por muchos como el mejoramiento del bienestar de sus ciudadanos y el desarrollo tecnológico-presenta una relación fuerte con el deterioro del medioambiente y las consecuencias adversas que podría acarrear para todo el planeta. Teniendo en cuenta lo anterior, se podría suponer que si una comunidad incrementa su bienestar su hábitat podría verse seriamente deteriorado, lo cual establece una clara contradicción entre "bienestar" y la calidad del "estar", esta última definida como la existencia física del ser humano en el hoy y en el ahora. Por todo lo anterior, este trabajo pretende identificar qué tipo de relación tienen la innovación tecnológica y el bienestar humano. Para ello, se reflexionó acerca de la necesidad de "bienestar" inherente del hombre, la innovación tecnológica ligada a este estado de bienestar y sus consecuencias en el "estar" mismo. Se concluye que existe una relación muy estrecha, ya que la innovación tecnológica hace parte de la esencia de la raza humana; sin embargo, mientras el desarrollo de la tecnología esté orientado por intereses particulares, ligados a poderes económicos y políticos, la relación entre "bienestar" y la calidad del "estar" tendrán una relación inversa. La evolución del concepto de "bienestar" definido por Marcuse requiere el cambio del estilo de vida, y de esta forma la innovación debería estar enfocada en el diseño de tecnología menos nociva-amigable con el medioambiente-, que les permita a todos vivir bien, que no simplemente vivir mejor. Palabras clave: desarrollo tecnológico; impacto ambiental; calidad de vida.

Work, 2017

BACKGROUND: Discomfort perceived in activities where there is a prolonged sitting posture are nor... more BACKGROUND: Discomfort perceived in activities where there is a prolonged sitting posture are normally compensated in a natural way by means of macro-repositioning movements in the seat. Nevertheless, evidence shows that such movements are not able to palliate discomfort due to lumbar pain. OBJECTIVE: This study involves research performed to demonstrate whether induced postural changes are able to mitigate this type of discomfort during a simulated driving activity. METHODS: Twenty-four subjects with lumbar pain (LBP) and without lumbar pain (WLBP) underwent 90 min of simulated driving activities while periodic variations of seat tilt (Tt) were implemented. RESULTS: Discomfort perception due to lumbar pain significantly decreased in the case of Tt compared with the case of WTt (without seat tilt), and significant differences were found (p = 0.02). However, treatments with Tt indicated that no substantial differences exist between LBP and WLBP subjects when considering discomfort perception due to lumbar pain and the erector spinae activity. CONCLUSIONS: This study revealed that periodic variations on seat tilt can help to reduce discomfort perception due to lumbar pain during driving activities, regardless of the health condition of the subject.

Ingeniare. Revista chilena de ingeniería, 2016

This work aimed to develop a mathematical model to evaluate the effect of seat inclination using ... more This work aimed to develop a mathematical model to evaluate the effect of seat inclination using as input the biomechanical characteristics of the user. The biomechanical model includes weight, posture, flexion of the pelvis and trunk and 5º and-5º seat inclinations. Using actual data collected during an experiment with 26 participants, a validation process was carried out to measure the model's ability to correctly predict load values on the ischial tuberosity. The results show a consistent model with an accuracy of 82% and a predictive quality of pred (25) = 0.77. Another outcome of the study is an equation to calculate the intradiscal pressure based on the load at the ischial tuberosity. The biomechanical model and the equations can be used to assess the effects of inclination of the seat and its backrest in chair design processes.

Nova Scientia, 2014

Las tipologías arquitecturales encontradas en el contexto del análisis estructural de construccio... more Las tipologías arquitecturales encontradas en el contexto del análisis estructural de construcciones con significado histórico y cultural son complejas. El modelado numérico es propuesto como una solución para diagnosticar la seguridad estructural de estas edificaciones. En esta investigación se realizaron pruebas de flexión estática y se calcularon los módulos de elasticidad y de ruptura en vigas antiguas de P. abies. La densidad de la madera fue de 422 kg/m3 para las vigas con un contenido de humedad de 12 %. El módulo de elasticidad promedio fue de 9,059 MPa y el módulo de ruptura fue de 29.18 Pa. Los módulos presentaron una variabilidad aceptable. Los resultados experimentales se contrastaron con las predicciones numéricas empleando el método del elemento finito. Las predicciones numéricas en los dominios lineal y no lineal mostraron buena aproximación con los resultados experimentales.

Agrociencia, 1997

The final success of a common bean (Phaseolus vulgaris L.) variety depends upon the consumer acce... more The final success of a common bean (Phaseolus vulgaris L.) variety depends upon the consumer acceptance. The objective of the present study was to determine the weight, tannin content and protein percentage of seeds in 16 genotypes of common bean; the sensory evaluation of aroma, flavor, color and general acceptability of cooked beans was also determined with the aim to study the relationship between some of these characteristics. Seed weight of Bayo Victoria (46.6 g/100 seeds) was the highest while that of lines BAT-477 and L-3-1-1-1M presented the lowest seed weight (22.8 g/100 seeds). The tannin content ranged from 131.4 mg equivalent of catequin (eq. cat.)/g of seed coat in Flor de Mayo M38 to 33.8 mg eq. cat./g of seed coat in Mayocoba; protein content ranged from 13.30 to 20.75 % in Bayocel-1 and Bayomex, respectively. The panelists could not detected differences in aroma of cooked beans among cultivars. Flor de Mayo M38 was the most accepted variety in relation to the flavor of cooked beans; nevertheless, no statistic differences were detected between hedonic values of flavor of this cultivar and the rest of genotypes. Evaluation of color of cooked beans showed that panelist detected differences (p

International Journal on Interactive Design and Manufacturing (IJIDeM), 2016

By modifying the angle of the seat pan, this research aimed to determine the ideal seated posture... more By modifying the angle of the seat pan, this research aimed to determine the ideal seated posture for drivers of trucks while having the best balance between a lower load on the lumbar spine and the perception of discomfort. Eighteen drivers underwent simulated driving tasks; they operated a video game on cruise mode with steering wheel, pedals and visual demand. Four driving tests were performed in periods of 10 min, which is enough time to make the subject familiar with the seat. After every test, participants had to stand up and walk for 1 min, then exercise for 25 s, allowing the relaxation of the back. This study suggests that a 5 • seat pan tilt, generates more kyphotic posture and more pressure on the seat, however this tilt together with the position of −5 • reported lower values in the perception of discomfort. No significant differences were found between the pressure on the seat (p = 0.88) and the perceived discomfort (p = 0.94); Pearson's coefficients revealed a weak dependence between the pressure on the seat and the perceived discomfort (r = 0.14). Further analysis concluded that some angles of seat pan, have less biomechanical demand while a high perception of discomfort, indicating that positions with less biomechanical load on the spine does not guarantee that those are really comfortable.

The American Journal of Surgery, 1976

Billroth in 1894 or Franke in 1900 is often credited with performing total pancreatectomy [I], bu... more Billroth in 1894 or Franke in 1900 is often credited with performing total pancreatectomy [I], but the first documented total pancreatic resection was reported by Rockey [2] in 1943. The patient survived only fifteen days after surgery. The first successful total pancreatectomy was performed for benign insulinoma by Priestley, Comfort, and Radcliffe [3] in 1944. The uneventful postoperative course of this patient suggested that total removal of the pancreas was both technically and physiologically feasible and stimulated interest in the use of this procedure for pancreatic carcinoma for several years. (Table I.) In 1954 Ross [9] reported four cases of total pancreatectomy for carcinoma and stated that this procedure was the operation of choice for cancer of the pancreas. Nevertheless, because of the high morbidity and mortality and poor long-term survival, total pancreatic resection soon fell into disfavor. In the last decade, hawever, surgeons have had renewed interest in total pancreatectomy in the treatment of ductal carcinoma of the head of the pancreas. At the University of Minnesota three patients have recently undergone total pancreatic resection for this disease. The results in these patients along with a review of the literature form the substance of this report. case Reports Case I. The patient (LF, UMH 1X-10-33), a sixty-six year old white man, was admitted to the University of Minnesota Hospitals on November 16, 1971 because of epigastric pain and jaundice during the preceding month. Three years before admission he had undergone chole-From the

Proceedings of the 4th ACM international workshop on Wireless mobile multimedia - WOWMOM '01, 2001

As the number of Mobile IP users grows, so will the signaling overhead associated with Internet m... more As the number of Mobile IP users grows, so will the signaling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signaling overhead and optimize the mobility management performance. Currently, Mobile

Mobile Networks and Applications, 2002

As the number of Mobile IP users grows, so will the signalling overhead associated with Internet ... more As the number of Mobile IP users grows, so will the signalling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signalling overhead and optimize the mobility management performance. Currently, Mobile

Genome biology, Jan 11, 2009

Recent evidence from global studies of gene expression indicates that transcriptomes are more com... more Recent evidence from global studies of gene expression indicates that transcriptomes are more complex than expected. Xenopus has been typically used as a model organism to study early embryonic development, particularly dorso-ventral patterning. In order to identify novel transcripts involved in dorso-ventral patterning, we compared dorsal and ventral transcriptomes of Xenopus tropicalis at the gastrula stage using serial analysis of gene expression (SAGE). Of the experimental tags, 54.5% were confidently mapped to transcripts and 125 showed a significant difference in their frequency of occurrence between dorsal and ventral libraries. We selected 20 differentially expressed tags and assigned them to specific transcripts using bioinformatics and reverse SAGE. Five mapped to transcripts with known dorso-ventral expression and the frequency of appearance for these tags in each library is in agreement with the expression described by other methods. The other 15 tags mapped to transcrip...

ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain, hosts most of ESA space bas... more ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain, hosts most of ESA space based missions' scientific archives, in planetary (Mars Express, Venus Express, Rosetta, Huygens, Giotto, Smart-1, all in ESA Planetary Science Archive), in astronomy (XMM-Newton, Herschel, ISO, Integral, Exosat, Planck) and in solar physics (Soho). All these science archives are operated by a dedicated Science Archives and Virtual

The Journal of Agricultural Science, 1996

SUMMARYThe effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L... more SUMMARYThe effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L.) genotypes was investigated in Celaya, Gto., Mexico, in 1991. Beans were grown under four moisture regimes: (1) well-irrigated, control, (2) with water stress during the vegetative stage, (3) with water stress during the reproductive stage and (4) with water stress during the whole growing cycle. Biological nitrogen fixation was measured by 15N-isotope dilution using sorghum as a reference crop. Nodulation and N2-fixation data showed genotypic differences in response to water stress. Under non-stressed conditions, cv. Bayocel fixed the most nitrogen (85 kg/ha) and cultivar Flor de Mayo Baji'o the least (33 kg/ha). Under water stress at the reproductive stage, these cultivars fixed 9 and 6 kg N/ha, respectively. Water stress during the reproductive stage reduced nodulation by an average of 43% with no recovery after rewatering. Water stress during the reproductive stage had a greate...

Soil and Tillage Research, 2005

Conservation tillage could enhance soil organic carbon (SOC) sequestration, but is rarely used in... more Conservation tillage could enhance soil organic carbon (SOC) sequestration, but is rarely used in cropping systems in Mexico, especially under irrigation. A study was conducted on a clayey, smectitic, isothermic Udic Pellustert to evaluate the use of traditional-deep and no-tillage systems on SOC dynamics for wheat (Triticum aestivum L.)-corn (Zea mays L.) and wheatbean (Phaseolus vulgaris L.) cropping systems. Experimental design was a randomized block of five tillage/crop-rotation (two crops per year) systems with four replications: (WC-CTb) wheat-corn, burning the residues of both crops, plowing and disking twice (WC-CT) wheat-corn under conventional tillage (plowing and disking twice to incorporate crop residues following the harvest of each crop), (WC-NT) wheat-corn under no-till, (WB-CT) wheat-bean under conventional tillage, and (WB-NT) wheat-bean under no-till. Each crop in the sequence received one of three fertilizer-N rates broadcast as urea: (a) 0, 150, and 300 kg N ha À1 for corn; (b) 0, 40, and 80 kg N ha À1 for bean; and (c) 0, 125, and 250 kg N ha À1 for wheat. The baseline year was 1994, and relative changes were measured from 1994 to 1999 for grain yield and residue production, crop residue C and d 13 C, SOC, soil C/N ratio, and change in soil d 13 C. Interaction of cropping system  fertilizer-N rate was highly important to grain yield and crop residue production and amount of crop-residue C produced. High N rates increased SOC sequestration and decreased soil C/N ratios. In WC systems, more negative d 13 C was associated with higher N rates, indicating increased contribution of wheat (a C 3 plant) residue C relative to corn (a C 4 plant). In WB, N-rate and tillage had no effect on SOC sequestration. Highest rate of SOC sequestration was under WC-NT and when increases in SOC from 1994 to 1999 were annualized was 1.0 and 1.9 Mg SOC yr À1 in the 0-15-and 15-30-cm depths, respectively. Corresponding SOC in 0-15-and 15-30-cm depths in the WC-CT treatment was 0.2 and 0.6 Mg yr À1 and amounts in all other treatments were equal or lower than those observed for WC-CT. There was a significant correlation between aboveground crop-residue C produced and amount of SOC sequestered. Results from this study indicate no-till on N-fertilized WC systems can potentially increase SOC sequestration on large areas of irrigated Vertisols in Central Mexico while maintaining high crop yields.

Plant and Soil, 1991

The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with ... more The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with eight rainless (November through June) and four wet months (700 mm annual precipitation). The forest reaches a mean height of 10 m. Tree density in the research area was 4700 trees per ha with a basal area at breast height of 23 m 2 per ha. The above-and below-ground biomass of trees, shrubs, and lianas was 73.6 Mg ha-and 31 Mg ha-1, respectively. A root:shoot biomass ratio of 0.42 was calculated. Nearly two thirds of all roots occur in the 0-20 cm soil layer and 29% of all roots have a diameter of less than 5 mm.

Revista UIS Ingenierías, 2017

Existe evidencia que asocia el dolor lumbar con la postura sedente. Para contrarrestar estos efec... more Existe evidencia que asocia el dolor lumbar con la postura sedente. Para contrarrestar estos efectos, se ha estudiado los beneficios de bascular el asiento en actividades de conducción, sin embargo se ha encontrado que no existen estudios en trabajo de oficina. Objetivo: Evaluar la influencia del asiento basculante en la percepción de dolor lumbar. Materiales y métodos: se plantearon dos tratamientos: a) asiento con basculación y b) asiento sin basculación; estudiados en cuatro tareas de oficina: leer, escribir a mano, digitar y navegar en internet. Como respuesta se midió la actividad muscular del tronco, la postura de la espalda, el tiempo y el número de errores. Resultados: En las tareas de digitar, navegar en internet y leer existe una diferencia significativa, es decir que la basculación influye en el comportamiento postural y en el tiempo productivo. Conclusiones: Estudiar variables como la presión del asiento para encontrar mayor evidencia.

Revista UIS Ingenierías, 2017

When ergonomic criteria are separately applied to the design of chairs, the feeling of comfort is... more When ergonomic criteria are separately applied to the design of chairs, the feeling of comfort is not guaranteed. In this case, the aesthetic and perceptive features of the chair provide the sensations of comfort, and several studies have determined that comfort and discomfort present some characteristics that make them different from each other. Moreover, early perceptions by the user remain invariable when there is no interaction between the person and the object. Therefore, it can be assumed that if a device is considered comfortable after an initial experience of use, it may well not be thought as such after extended use. Based on this, the present research study aimed at establishing the differences in the perceptions of comfort of two chairs before and after extended sitting posture. Six subjects participated in this study, all they were women from 20 to 45 years of age, who usually perform office work in extended sitting posture, with a body mass index (BMI) ranging between 20 and 30 Kg/m2. In the experiment, four office tasks were assigned (reading, transcribing a text, handwriting and searching on the internet) during sixty minutes. The experiment was divided into two sessions, to use the two chairs subject of the study. Each participant was assessed at the same hour but on two different days. By means of the semantic differential, evaluations of visual perception were carried out by the participants before and after using the chair. The results reveal differences in the perception evaluation of both chairs before and after their use. In the case of the chair a, the assessment of the adjectives never decreased. This study shows that the pleasure provided by a product is not static and it does evolve by product time of use and manipulation. Even though there were no statistical differences in the adjective pairs studied when only one chair was examined, it was demonstrated that its perception might improve or worsen on the basis of time. Similarly, this perceptual behavior is not indifferent to the object, finding significant differences before and after use when comparing the chairs. Finally, this analysis tool provides better evidence on product functionality by indicating whether there are failures in the proposed design.

Revista Ciência da Madeira - RCM, 2020

RESUMEN Existe evidencia empírica de que la madera laminada, comparativamente con la madera sólid... more RESUMEN Existe evidencia empírica de que la madera laminada, comparativamente con la madera sólida mejora su densidad aparente y su módulo de elasticidad. El objetivo de la investigación fue determinar la densidad, la velocidad de onda y el módulo dinámico por ondas de esfuerzo en madera sólida y laminada de Enterolobium cyclocarpum, Tabebuia rosea y Juglans pyriformis. Se elaboraron probetas de madera sólida y laminada de pequeñas dimensiones y se realizaron pruebas de ondas de esfuerzo. La densidad aparente de la madera laminada, en comparación con la de la madera sólida, se incrementa para las tres especies. En cambio, el módulo dinámico de la madera laminada aumenta para Enterolobium cyclocarpum y Tabebuia rosea, pero disminuye para Juglans pyriformis. La variabilidad de la densidad aparente, la velocidad de onda y el módulo dinámico, aumentan o disminuyen según se trate de la especie y o del parámetro en cuestión. Los resultados son válidos para el caso de laminado de pequeñas probetas de las especies estudiadas. Para su aplicación a proyectos de ingeniería, es recomendable realizar estudios ex profeso. Palabras clave: densidad aparente; velocidad de onda; módulo dinámico. Mechanical characterization by stress waves of the laminated wood of three angiosperm species ABSTRACT There is empirical evidence that laminated wood, compared to solid wood, improves its bulk density and modulus of elasticity. The objective of the research was to determine the apparent density, the wave velocity and the dynamic modulus by stress waves in solid and laminated wood of Enterolobium cyclocarpum, Tabebuia rosea and Juglans pyriformis. Solid and laminated wood specimens of small dimensions were prepared, and stress wave tests were carried out. The apparent density of laminated wood, in comparison with that of solid wood, increases for all three species. In contrast, the dynamic modulus of laminated wood increases for Enterolobium cyclocarpum and Tabebuia rosea but decreases for Juglans pyriformis. The variability of the apparent density, the wave velocity and the dynamic modulus, increases or decreases depending on the species and/or parameter in question. The results are valid for the case of laminated small specimens of the species studied. For its application to engineering projects, it is advisable to carry out ex profeso studies.

Información tecnológica, 2019

Se presenta evidencia que asocia la influencia de los asientos dinámicos con el tiempo productivo... more Se presenta evidencia que asocia la influencia de los asientos dinámicos con el tiempo productivo en trabajos de oficina. Veintiocho mujeres voluntarias participaron en el experimento que se realizó mediante el planteamiento de dos situaciones a) con basculación del asiento y b) sin basculación del asiento, en cuatro tareas de oficina: leer, escribir a mano, navegar en internet y digitar. En el estudio se midió el tiempo productivo y el número de errores. Se encontró que los asientos dinámicos no afectan significativamente el desempeño de los trabajadores. Por el contrario, los análisis descriptivos muestran mejores tiempos productivos y reducción en el número de errores. Se sugiere que la incorporación de asientos dinámicos debería ser un requerimiento importante en el diseño de sillas para oficina. Se ha demostrado que ellos disminuyen la incomodidad debida al dolor lumbar y contribuye a mejorar el rendimiento en el trabajo.

Revista UIS Ingenierías, 2019

La tecnología es responsable de la transformación del hombre y de la humanidad; es una respuesta ... more La tecnología es responsable de la transformación del hombre y de la humanidad; es una respuesta innata al empeño de los individuos por vivir en el mundo y "estar bien". No obstante, el crecimiento económico de las nacionesentendido por muchos como el mejoramiento del bienestar de sus ciudadanos y el desarrollo tecnológico-presenta una relación fuerte con el deterioro del medioambiente y las consecuencias adversas que podría acarrear para todo el planeta. Teniendo en cuenta lo anterior, se podría suponer que si una comunidad incrementa su bienestar su hábitat podría verse seriamente deteriorado, lo cual establece una clara contradicción entre "bienestar" y la calidad del "estar", esta última definida como la existencia física del ser humano en el hoy y en el ahora. Por todo lo anterior, este trabajo pretende identificar qué tipo de relación tienen la innovación tecnológica y el bienestar humano. Para ello, se reflexionó acerca de la necesidad de "bienestar" inherente del hombre, la innovación tecnológica ligada a este estado de bienestar y sus consecuencias en el "estar" mismo. Se concluye que existe una relación muy estrecha, ya que la innovación tecnológica hace parte de la esencia de la raza humana; sin embargo, mientras el desarrollo de la tecnología esté orientado por intereses particulares, ligados a poderes económicos y políticos, la relación entre "bienestar" y la calidad del "estar" tendrán una relación inversa. La evolución del concepto de "bienestar" definido por Marcuse requiere el cambio del estilo de vida, y de esta forma la innovación debería estar enfocada en el diseño de tecnología menos nociva-amigable con el medioambiente-, que les permita a todos vivir bien, que no simplemente vivir mejor. Palabras clave: desarrollo tecnológico; impacto ambiental; calidad de vida.

Work, 2017

BACKGROUND: Discomfort perceived in activities where there is a prolonged sitting posture are nor... more BACKGROUND: Discomfort perceived in activities where there is a prolonged sitting posture are normally compensated in a natural way by means of macro-repositioning movements in the seat. Nevertheless, evidence shows that such movements are not able to palliate discomfort due to lumbar pain. OBJECTIVE: This study involves research performed to demonstrate whether induced postural changes are able to mitigate this type of discomfort during a simulated driving activity. METHODS: Twenty-four subjects with lumbar pain (LBP) and without lumbar pain (WLBP) underwent 90 min of simulated driving activities while periodic variations of seat tilt (Tt) were implemented. RESULTS: Discomfort perception due to lumbar pain significantly decreased in the case of Tt compared with the case of WTt (without seat tilt), and significant differences were found (p = 0.02). However, treatments with Tt indicated that no substantial differences exist between LBP and WLBP subjects when considering discomfort perception due to lumbar pain and the erector spinae activity. CONCLUSIONS: This study revealed that periodic variations on seat tilt can help to reduce discomfort perception due to lumbar pain during driving activities, regardless of the health condition of the subject.

Ingeniare. Revista chilena de ingeniería, 2016

This work aimed to develop a mathematical model to evaluate the effect of seat inclination using ... more This work aimed to develop a mathematical model to evaluate the effect of seat inclination using as input the biomechanical characteristics of the user. The biomechanical model includes weight, posture, flexion of the pelvis and trunk and 5º and-5º seat inclinations. Using actual data collected during an experiment with 26 participants, a validation process was carried out to measure the model's ability to correctly predict load values on the ischial tuberosity. The results show a consistent model with an accuracy of 82% and a predictive quality of pred (25) = 0.77. Another outcome of the study is an equation to calculate the intradiscal pressure based on the load at the ischial tuberosity. The biomechanical model and the equations can be used to assess the effects of inclination of the seat and its backrest in chair design processes.

Nova Scientia, 2014

Las tipologías arquitecturales encontradas en el contexto del análisis estructural de construccio... more Las tipologías arquitecturales encontradas en el contexto del análisis estructural de construcciones con significado histórico y cultural son complejas. El modelado numérico es propuesto como una solución para diagnosticar la seguridad estructural de estas edificaciones. En esta investigación se realizaron pruebas de flexión estática y se calcularon los módulos de elasticidad y de ruptura en vigas antiguas de P. abies. La densidad de la madera fue de 422 kg/m3 para las vigas con un contenido de humedad de 12 %. El módulo de elasticidad promedio fue de 9,059 MPa y el módulo de ruptura fue de 29.18 Pa. Los módulos presentaron una variabilidad aceptable. Los resultados experimentales se contrastaron con las predicciones numéricas empleando el método del elemento finito. Las predicciones numéricas en los dominios lineal y no lineal mostraron buena aproximación con los resultados experimentales.

Agrociencia, 1997

The final success of a common bean (Phaseolus vulgaris L.) variety depends upon the consumer acce... more The final success of a common bean (Phaseolus vulgaris L.) variety depends upon the consumer acceptance. The objective of the present study was to determine the weight, tannin content and protein percentage of seeds in 16 genotypes of common bean; the sensory evaluation of aroma, flavor, color and general acceptability of cooked beans was also determined with the aim to study the relationship between some of these characteristics. Seed weight of Bayo Victoria (46.6 g/100 seeds) was the highest while that of lines BAT-477 and L-3-1-1-1M presented the lowest seed weight (22.8 g/100 seeds). The tannin content ranged from 131.4 mg equivalent of catequin (eq. cat.)/g of seed coat in Flor de Mayo M38 to 33.8 mg eq. cat./g of seed coat in Mayocoba; protein content ranged from 13.30 to 20.75 % in Bayocel-1 and Bayomex, respectively. The panelists could not detected differences in aroma of cooked beans among cultivars. Flor de Mayo M38 was the most accepted variety in relation to the flavor of cooked beans; nevertheless, no statistic differences were detected between hedonic values of flavor of this cultivar and the rest of genotypes. Evaluation of color of cooked beans showed that panelist detected differences (p

International Journal on Interactive Design and Manufacturing (IJIDeM), 2016

By modifying the angle of the seat pan, this research aimed to determine the ideal seated posture... more By modifying the angle of the seat pan, this research aimed to determine the ideal seated posture for drivers of trucks while having the best balance between a lower load on the lumbar spine and the perception of discomfort. Eighteen drivers underwent simulated driving tasks; they operated a video game on cruise mode with steering wheel, pedals and visual demand. Four driving tests were performed in periods of 10 min, which is enough time to make the subject familiar with the seat. After every test, participants had to stand up and walk for 1 min, then exercise for 25 s, allowing the relaxation of the back. This study suggests that a 5 • seat pan tilt, generates more kyphotic posture and more pressure on the seat, however this tilt together with the position of −5 • reported lower values in the perception of discomfort. No significant differences were found between the pressure on the seat (p = 0.88) and the perceived discomfort (p = 0.94); Pearson's coefficients revealed a weak dependence between the pressure on the seat and the perceived discomfort (r = 0.14). Further analysis concluded that some angles of seat pan, have less biomechanical demand while a high perception of discomfort, indicating that positions with less biomechanical load on the spine does not guarantee that those are really comfortable.

The American Journal of Surgery, 1976

Billroth in 1894 or Franke in 1900 is often credited with performing total pancreatectomy [I], bu... more Billroth in 1894 or Franke in 1900 is often credited with performing total pancreatectomy [I], but the first documented total pancreatic resection was reported by Rockey [2] in 1943. The patient survived only fifteen days after surgery. The first successful total pancreatectomy was performed for benign insulinoma by Priestley, Comfort, and Radcliffe [3] in 1944. The uneventful postoperative course of this patient suggested that total removal of the pancreas was both technically and physiologically feasible and stimulated interest in the use of this procedure for pancreatic carcinoma for several years. (Table I.) In 1954 Ross [9] reported four cases of total pancreatectomy for carcinoma and stated that this procedure was the operation of choice for cancer of the pancreas. Nevertheless, because of the high morbidity and mortality and poor long-term survival, total pancreatic resection soon fell into disfavor. In the last decade, hawever, surgeons have had renewed interest in total pancreatectomy in the treatment of ductal carcinoma of the head of the pancreas. At the University of Minnesota three patients have recently undergone total pancreatic resection for this disease. The results in these patients along with a review of the literature form the substance of this report. case Reports Case I. The patient (LF, UMH 1X-10-33), a sixty-six year old white man, was admitted to the University of Minnesota Hospitals on November 16, 1971 because of epigastric pain and jaundice during the preceding month. Three years before admission he had undergone chole-From the

Proceedings of the 4th ACM international workshop on Wireless mobile multimedia - WOWMOM '01, 2001

As the number of Mobile IP users grows, so will the signaling overhead associated with Internet m... more As the number of Mobile IP users grows, so will the signaling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signaling overhead and optimize the mobility management performance. Currently, Mobile

Mobile Networks and Applications, 2002

As the number of Mobile IP users grows, so will the signalling overhead associated with Internet ... more As the number of Mobile IP users grows, so will the signalling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signalling overhead and optimize the mobility management performance. Currently, Mobile

Genome biology, Jan 11, 2009

Recent evidence from global studies of gene expression indicates that transcriptomes are more com... more Recent evidence from global studies of gene expression indicates that transcriptomes are more complex than expected. Xenopus has been typically used as a model organism to study early embryonic development, particularly dorso-ventral patterning. In order to identify novel transcripts involved in dorso-ventral patterning, we compared dorsal and ventral transcriptomes of Xenopus tropicalis at the gastrula stage using serial analysis of gene expression (SAGE). Of the experimental tags, 54.5% were confidently mapped to transcripts and 125 showed a significant difference in their frequency of occurrence between dorsal and ventral libraries. We selected 20 differentially expressed tags and assigned them to specific transcripts using bioinformatics and reverse SAGE. Five mapped to transcripts with known dorso-ventral expression and the frequency of appearance for these tags in each library is in agreement with the expression described by other methods. The other 15 tags mapped to transcrip...

ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain, hosts most of ESA space bas... more ESA's European Space Astronomy Centre (ESAC), near Madrid, Spain, hosts most of ESA space based missions' scientific archives, in planetary (Mars Express, Venus Express, Rosetta, Huygens, Giotto, Smart-1, all in ESA Planetary Science Archive), in astronomy (XMM-Newton, Herschel, ISO, Integral, Exosat, Planck) and in solar physics (Soho). All these science archives are operated by a dedicated Science Archives and Virtual

The Journal of Agricultural Science, 1996

SUMMARYThe effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L... more SUMMARYThe effect of water stress on nitrogen fixation in seven common bean (Phaseolus vulgaris L.) genotypes was investigated in Celaya, Gto., Mexico, in 1991. Beans were grown under four moisture regimes: (1) well-irrigated, control, (2) with water stress during the vegetative stage, (3) with water stress during the reproductive stage and (4) with water stress during the whole growing cycle. Biological nitrogen fixation was measured by 15N-isotope dilution using sorghum as a reference crop. Nodulation and N2-fixation data showed genotypic differences in response to water stress. Under non-stressed conditions, cv. Bayocel fixed the most nitrogen (85 kg/ha) and cultivar Flor de Mayo Baji'o the least (33 kg/ha). Under water stress at the reproductive stage, these cultivars fixed 9 and 6 kg N/ha, respectively. Water stress during the reproductive stage reduced nodulation by an average of 43% with no recovery after rewatering. Water stress during the reproductive stage had a greate...

Soil and Tillage Research, 2005

Conservation tillage could enhance soil organic carbon (SOC) sequestration, but is rarely used in... more Conservation tillage could enhance soil organic carbon (SOC) sequestration, but is rarely used in cropping systems in Mexico, especially under irrigation. A study was conducted on a clayey, smectitic, isothermic Udic Pellustert to evaluate the use of traditional-deep and no-tillage systems on SOC dynamics for wheat (Triticum aestivum L.)-corn (Zea mays L.) and wheatbean (Phaseolus vulgaris L.) cropping systems. Experimental design was a randomized block of five tillage/crop-rotation (two crops per year) systems with four replications: (WC-CTb) wheat-corn, burning the residues of both crops, plowing and disking twice (WC-CT) wheat-corn under conventional tillage (plowing and disking twice to incorporate crop residues following the harvest of each crop), (WC-NT) wheat-corn under no-till, (WB-CT) wheat-bean under conventional tillage, and (WB-NT) wheat-bean under no-till. Each crop in the sequence received one of three fertilizer-N rates broadcast as urea: (a) 0, 150, and 300 kg N ha À1 for corn; (b) 0, 40, and 80 kg N ha À1 for bean; and (c) 0, 125, and 250 kg N ha À1 for wheat. The baseline year was 1994, and relative changes were measured from 1994 to 1999 for grain yield and residue production, crop residue C and d 13 C, SOC, soil C/N ratio, and change in soil d 13 C. Interaction of cropping system  fertilizer-N rate was highly important to grain yield and crop residue production and amount of crop-residue C produced. High N rates increased SOC sequestration and decreased soil C/N ratios. In WC systems, more negative d 13 C was associated with higher N rates, indicating increased contribution of wheat (a C 3 plant) residue C relative to corn (a C 4 plant). In WB, N-rate and tillage had no effect on SOC sequestration. Highest rate of SOC sequestration was under WC-NT and when increases in SOC from 1994 to 1999 were annualized was 1.0 and 1.9 Mg SOC yr À1 in the 0-15-and 15-30-cm depths, respectively. Corresponding SOC in 0-15-and 15-30-cm depths in the WC-CT treatment was 0.2 and 0.6 Mg yr À1 and amounts in all other treatments were equal or lower than those observed for WC-CT. There was a significant correlation between aboveground crop-residue C produced and amount of SOC sequestered. Results from this study indicate no-till on N-fertilized WC systems can potentially increase SOC sequestration on large areas of irrigated Vertisols in Central Mexico while maintaining high crop yields.

Plant and Soil, 1991

The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with ... more The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with eight rainless (November through June) and four wet months (700 mm annual precipitation). The forest reaches a mean height of 10 m. Tree density in the research area was 4700 trees per ha with a basal area at breast height of 23 m 2 per ha. The above-and below-ground biomass of trees, shrubs, and lianas was 73.6 Mg ha-and 31 Mg ha-1, respectively. A root:shoot biomass ratio of 0.42 was calculated. Nearly two thirds of all roots occur in the 0-20 cm soil layer and 29% of all roots have a diameter of less than 5 mm.