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Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties

Nova, María; Arévalo, Yaritza; Murillo, Edwin A. (Journal of Applied Polymer ScienceWashintong D.C , Estados Unidos, 2018-07-18)

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl ...
Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties

Ararat, Carlos A.; Quiñonez, Winston; Murillo, Edwin A. (Macromolecular Research, 2019-03-29)

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. ...
Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature

Raba, Angela; Rincón Joya, Miryam; Barba, Jose (Indian Journal Of Pure '&' Applied PhysicsNueva Delhi , India, 2019)

In this work a study of the effect of the synthesis conditions on the vibratory and particle size properties in the cupric oxide (CuO) has been presented. The synthesis has been carried out by the polymeric precursor method ...
Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester

Murillo, Edwin A.; Caicedo, Carolina (European Polymer Journal, 2019-09)

In a previous study, we realized the functionalization of polypropylene (PP) with maleinized hyperbranched polyol polyester (MHBP) by using dicumyl peroxide (DCP) as an initiator for obtaining the PP-g-MHBPs. This process ...
Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol

Ararat, Carlos A.; Percino, M. Judith; Murillo, Edwin A. (Macromolecular Research, 2019-11-12)

Low density polyethylene (LDPE)/polyamide6 (PA) blends can lead to a synergy between the properties of these materials. These blends are employed mainly in the packing industry, especially in food factories. The problem ...
Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method

Raba, Angela; Cardenas-Flechas, L. J.; Barba-Ortega, J.; Rincón Joya, Miryam; Moreno-Aldana, Luis Carlos (Journal of Inorganic and Organometallic Polymers and MaterialsWashintong D.C , Estados Unidos, 2020-07-31)

gglomerates of Co3O4 were obtained using the sol–gel method for the synthesis with subsequent calcination of the samples up to 550 °C. Through X-rays it was observed that the samples presented the pure spinel phase with a ...
Waterborne star-shaped styrene-alkyd resins

Murillo, Edwin A. (Journal of Applied Polymer Science, 2019-08-13)

Waterborne star-shaped styrene-alkyd resins (SSARs) were synthesized from a branched alkyd resin (AR) and styrene (St) by miniemulsion polymerization. SSARs are an environmentally friendly material. The ratio of AR to St ...
Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties

Murillo, Edwin A.; Percino, M. Judith; Ceron, Margarita (Macromolecular Research, 2021-04-24)

The present study sought to obtain a hyperbranched polyester polyol derivative with fluorescent properties. Initially, a 4-((4-(9H-carbazol-9-yl)benzyl)oxy)-4-oxobut-2-enoic acid (CAV) was synthesized and esterified with ...
La ciudad como espacio habitado y fuente de socialización

Ayala Garcia, Erika Tatiana (ÁnforaColombia, 2017-06-20)

Objetivos: comprender el papel del espacio público en la construcción físico-vivencial de la ciudad y en la experiencia social del ser humano. Metodología: se aplicó revisión documental interdisciplinar que siguió las ...
Molecular characterization of two papaya ringspot virus isolates that cause devastating symptoms in Norte de Santander, Colombia

Chaves-Bedoya, Giovanni; Ortiz, Luz (European Journal of Plant PathologyAmsterdam , Paises Bajos, 2017-01-06)

Papaya ringspot virus is an RNA virus that belongs to the genus Potyvirus, family Potyviridae and affects both papaya and cucurbits, causing great economic losses. PRSV isolates are divided into biotypes P and W; both ...
Assessment of the strategies adopted by teachers in the teaching of science from the perspective of basic education students

VELOZA RINCÓN, RAMIRO ALEJANDRO; HERNANDEZ SUAREZ, CESAR AUGUSTO (ÁnforaColombia, 2018-06-25)

Objective: to characterize and assess the level of development in pedagogical competences through the strategies adopted by Basic Education teachers in the teaching of science from the students’ perspective. Methodology: ...
Caracterización Térmica de mezclas de arcillas utilizadas en la fabricación de productos de mampostería para la contrucción

García León, Ricardo Andrés; Flórez Solano, Eder; Acevedo Peñaloza, Carlos (Revista Colombiana De Tecnologías De Avanzada ISSNColombia, 2018)

Actualmente en Norte de Santander existe gran variedad de yacimientos naturales que se pueden utilizar para fabricar productos de mampostería para la construcción como lo son bloques, tejas, ladrillos, baldosas, entre ...
Valoración de las estrategias adoptadas por docentes en la enseñanza de la ciencia desde la perspectiva de los estudiantes de educación básica

HERNANDEZ SUAREZ, CESAR AUGUSTO; VELOZA RINCÓN, RAMIRO ALEJANDRO (ÁnforaColombia, 2018-06-25)

Objetivos: caracterizar y evaluar el nivel de desarrollo de las competencias pedagógicas mediante las estrategias adoptadas por docentes de Educación Básica en la enseñanza de la ciencia desde la perspectiva de los ...
Transcriptional changes involved in kumquat (Fortunella spp) defense response to Xanthomonas citri subsp. citri in early stages of infection

GIRALDO GONZALEZ, JHON JAIRO; Carvalho, flávia Maria de Souza; Hirochi Herai, Roberto; Aparecido Ferro, Jesus; Chaves Bedoya, Giovanni; Rodas Mendoza, Elkin Fernando (Physiological and Molecular Plant Pathology, 2021-12)

Xanthomonas citri subsp. citri (Xcc), the causal agent of type A canker, differentially affects all commercial varieties of citrus plants. Among them, Fortunella spp (kumquat) have higher tolerance to disease development, ...
Exergetic Evaluation of a Rankine Cycle with Regeneration: Effect of Turbine Inlet Temperature and Source Temperature

Arrieta Mondragón, Leonardo; Valencia Ochoa, Guillermo; Acevedo Peñaloza, Carlos Humberto (International Journal of Applied Engineering ResearchIndia, 2018)

The Rankine cycle is a thermodynamic cycle widely used in power plants, specifically in steam power plants, due to its great importance in the industry. It has also been studied in recent years in search of parameters that ...
Development of non-conservative mechanical models applied to the low energy impact phenomenon

Coba Salcedo, Milton Fabian; Acevedo Peñaloza, Carlos Humberto; Lopez Navas, Javier (Contemporary Engineering SciencesBulgaria, 2018-07-18)

Non-conservative mechanical models are developed to be applied to the low energy impact phenomenon. The analytical description of the proposed models is made and the numerical solution of the system of differential ...
Comparison of the Concentration Factor of Stresses on Flat Sheets with Two Holes with Low and High Speed Voltage Test

Acevedo Peñaloza, Carlos Humberto; Ramón Ramón, Sergio Andrés; Prada Botia, Gaudy Carolina (Contemporary Engineering SciencesBulgaria, 2018-07-31)

The research seeks to determine whether the stress concentration factor for flat plates with two stressed holes varies according to the application speed of the load. The research was developed using the experimental ...
Administración por valores: Estrategia de mejoramiento del clima organizacional en las empresas

Acevedo Peñaloza, Carlos Humberto; GOMEZ SANTOS, PATRICIA; VIDAL TOVAR, CARLOS RAMÓN; Ureña Villamizar, Yan Carlos (Revista EspaciosCaracas, Venezuela, 2018)

Se presentan a continuación los resultados de la investigación sobre la Administración por Valores como estrategia de mejoramiento del clima organizacional empresarial en organizaciones localizadas en la ciudad de Valledupar, ...
Bibliometric science indicators applied to environmental impacts research

Peralta-Ruiz, Yeimmy; Acevedo Peñaloza, Carlos Humberto; Valencia Ochoa, Guillermo (Contemporary Engineering SciencesBulgaria, 2018-08-01)

The growth and development of research on environmental impacts in terms of publications such as the Web of Science sample are analyzed during the period 2007-2018 using HistCite to learn about a global ranking, citations, ...
Phenomenological modeling and simulation of a textile stenter

Parra LLanos, John Wilmer; Santos, Rossane; Bastos Quadri, Marintho; Martins, Ianto Oliveira (Textile Research JournalWashintong D.C , Estados Unidos, 2020-04-28)

Mathematical modeling and simulation of cotton fabric drying in a stenter machine was performed using a finite element method. A standard κ-ɛ turbulence model was coupled with heat/mass transfer in porous media models. A ...

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Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties
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Nova, María | 2018-07-18

The functionalization of polypropylene (PP) with a maleinized hyperbranched polyester polyol (MHBP) was performed in solution to obtain PP-g-MHBPs. The degree of functionalization (FD) increased with MHBP and dicumyl peroxide (DCP) contents, but the contact angle followed an opposite behavior. The sample obtained with the proportion of 9.0 wt % MHBP and 2.0 wt % DCP and presented the highest FD value. An FD value of 2.4 wt %, produced a reduction of 19° on the contact angle. It was observed by differential scanning calorimetry (DSC) that the PP-g-MHBPs obtained by employing 3.0 wt % of MHBP, exhibited a slight reduction of the melting temperature (Tm) with the increase in the amounts of FD and DCP. Some FD values obtained in this study are higher than those obtained both commercial and noncommercial grades of PP functionalized with maleic anhydride. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46932.

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Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties
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Ararat, Carlos A. | 2019-03-29

The aim of this work is to obtain the material that, in the future, may become a better alternative, as a functionalizing agent, to maleic anhydride (MA), or a crosslinking agent with the least amount of functional groups. To achieve that goal, a hyperbranched polyester polyol (HBP) of the second generation (HBP2G) was modified with MA to obtain HBP2GMA. The effects of the proportion of MA in the structural, thermal, and rheological properties of the HBP2GMAs were evaluated. Furthermore, these properties were compared with those of the HBP2G. A reduction in the intensity of peak corresponding to the OH stretching of HBP2G was observed with the increase in the extent of HBP2G modification by the analysis of the infrared (IR). HBP2GMAs showed a peak at 3030 cm-1 in their IR spectra, which was due to the -CH=CH- stretching of MA. This was further assessed by 1H NMR analysis. The number of MA units grafted into HBP2G was between 4 and 9, indicating a high degree of functionality. All materials possessed viscosity values below 34.94 Pa·s at 110 °C, which were dependent on the grade of the modification percentage (MP) and the molar content of MA grafted into HBP2G. Mass spectrometry analysis demonstrated the formation of products by the esterification reaction between the HBP2G and MA. The thermal stability of the HBP2GMAs determined as the decomposition temperature (Td) was between 258 and 281 °C which was better than that of the HBP2G.

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Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature
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Raba, Angela | 2019

In this work a study of the effect of the synthesis conditions on the vibratory and particle size properties in the cupric oxide (CuO) has been presented. The synthesis has been carried out by the polymeric precursor method without modifying the PH in the process, this being a low cost method. The samples obtained have been subjected to several calcination temperatures, 450 °C, 550 °C, 650 °C and 800 °C. In particle analysis by X-ray, scanning electron microscopy (SEM) and statistical it has been observed that for very low or very high calcination temperatures the particle size increases, finding 650 °C as the best calcination temperature. In the Raman spectra, the Ag and Bg vibration have been presented in the samples, with the peaks being narrower for the temperature of 450 °C.

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Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester
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Murillo, Edwin A. | 2019-09

In a previous study, we realized the functionalization of polypropylene (PP) with maleinized hyperbranched polyol polyester (MHBP) by using dicumyl peroxide (DCP) as an initiator for obtaining the PP-g-MHBPs. This process was carried out in solution (it is not environmentally friendly). Therefore, in the present work was realized the synthesis in a molten state (free of organic solvent). The acid value (AV) of the PP-g-MHBP was lower than that of the MHBP and this increased with the proportions of DCP and MHBP employed. The presence of the characteristic signals of the MHBP in the infrared (IR) spectra of the PP-g-MHBPs allowed evidencing the functionalization of PP with MHBP. The higher functionalization degree (FD) presented by the samples was 9.10 wt%. Furthermore, all contact angles of the PP-g-MHBP were lower than that of the PP and inferior to 90°. The viscosity (η) values of the PP-g-MHBPs was lower than that of the PP. The Young’s modulus, the ultimate tensile strength and, the elongation at break of the PP-g-MHBPs were independent of the FD and DCP content.

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Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol
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Ararat, Carlos A. | 2019-11-12

Low density polyethylene (LDPE)/polyamide6 (PA) blends can lead to a synergy between the properties of these materials. These blends are employed mainly in the packing industry, especially in food factories. The problem of this system is that it is inmiscible, hence requires to be compatibilized. The aim of this study is to compatibilize blends of LDPE/PA6 using a LDPE modified with a maleinized hyperbranched polyol polyester (LDPE-g-MHBP) as a compatibilizing agent. Therefore blends of LDPE (50 wt%)/PA (50 wt%) were prepared by using proportions of 5 (Blend5), 10 (Blend10), 15 (Blend15) and 20 (Blend20) wt% of the LDPE-g-MHBP of the total mix. On the other hand, to determine the efficiency of the LDPE-g-MHBP as a compatibilizing agent, a Blend0 (blends of LDPE (50 wt%)/PA (50 wt%) without LDPE-g-MHBP) was used as the control sample. By infrared (IR) analysis was evidenced the interactions between PA and LDPE-g-MHBP. By differential scanning calorimetry analysis (DSC) was observed that the LDPE-g-MHBP increased the crystallinity of the LDPE phase, but the behavior was opposite to PA. The thermal stability and the viscosity of the blends obtained with LDPE-g-MHBP were higher than those of the Blend0. Scanning electron microscopy (SEM) analysis revealed that the LDPE-g-MHBP ostensibly improved the miscibility of the LDPE/PA blends.

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Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method
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Raba, Angela | 2020-07-31

gglomerates of Co3O4 were obtained using the sol–gel method for the synthesis with subsequent calcination of the samples up to 550 °C. Through X-rays it was observed that the samples presented the pure spinel phase with a crystallite size between 33.73 and 41.45 nm. In the thermogravimetric measurement from 262 °C high structural stability is presented with phase change at 917 °C. As the temperature increases, the particles increase in size, observing agglomerated nanometer particles that increase with temperature (3.5–3.8 μm). The 683 cm−1 Raman mode for 550 °C clearly presents an shifted compared to the other samples. The band gap for the samples under study varied with the temperature change of 1.77–1.81 eV. The FWHM decreases at a higher temperature, this confirms the larger crystallite size and the higher degree of sintering

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Waterborne star-shaped styrene-alkyd resins
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Murillo, Edwin A. | 2019-08-13

Waterborne star-shaped styrene-alkyd resins (SSARs) were synthesized from a branched alkyd resin (AR) and styrene (St) by miniemulsion polymerization. SSARs are an environmentally friendly material. The ratio of AR to St for obtaining SSARs was as follows: 50:50 (SSAR1), 60:40 (SSAR2), 70:30 (SSAR3), and 80:20 (SSAR4). The conversion percentage was directly proportional to St used, and was higher than 94.0 %. Infrared analysis and protonic nuclear magnetic resonance revealed the reaction between AR and St. The synthesis process also leads to the formation of polystyrene and its concentration increases with the concentration of St. The values of the reacted double-bond fractions were higher than 17.80%. The SSARs drop size was bigger than the particle size. The miniemulsion colloidal stability was good at room temperature. The SSARs zeta potential was between −55 and −90 mV. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48386.

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Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties
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Murillo, Edwin A. | 2021-04-24

The present study sought to obtain a hyperbranched polyester polyol derivative with fluorescent properties. Initially, a 4-((4-(9H-carbazol-9-yl)benzyl)oxy)-4-oxobut-2-enoic acid (CAV) was synthesized and esterified with a hyperbranched polyester polyol obtained from fourth generation (HBP) to synthesize carbazole-based hyperbranched polyester polyols (HBPCAV). The proportions employed of CAV were 5, 10, 15, and 20 wt% relative to that of HBP. The grafted CAV percentage (PgCAV) increased with the CAV content. The conversion percentages (CP) of the reactions for obtaining HBPCAV were higher than 95% and the hydroxyl values (OHV) were lower than that of HBP. The modification percentage (MP) of the HBP was between 9.33 and 27.38%. Using proton nuclear magnetic resonance (1H NMR) and infrared (IR) analyses was evidenced the formation of CAV and HBPCAV. Dynamic light scattering (DLS) analysis showed that HBPCAV exhibited aggregations. The number average molar mass (Mn), viscosity (η), and glass transition temperature (Tg) values of the HBPCAV samples were higher than those of the HBP, and also increased with the PgCAV values. The rheological behaviors of the HBP and HBPCAV samples were mainly Newtonian and shear-thinning, respectively. All HBPCAV exhibited electroluminescent properties.

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La ciudad como espacio habitado y fuente de socialización
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Ayala Garcia, Erika Tatiana | 2017-06-20

Objetivos: comprender el papel del espacio público en la construcción físico-vivencial de la ciudad y en la experiencia social del ser humano. Metodología: se aplicó revisión documental interdisciplinar que siguió las etapas de investigación, sistematización y exposición. Para recopilar información sobre la noción del espacio público, se acudió a fuentes primarias como libros, artículos, tesis y trabajos de investigación que incluyeran categorías de estudio como espacio público, ciudad, construcción social, memoria e identidad. Resultados: se encontró que el espacio público es componente esencial en la configuración de la ciudad; a través del espacio público el ser humano puede potenciar su experiencia a partir de la relación con sus pares y el entorno. Conclusiones: en el espacio público se produce el intercambio colectivo, la socialización y el anonimato; en él la persona genera lazos con sus pares y con el entorno, favoreciendo el arraigo de conceptos como el sentido de pertenencia y lugar. Por lo tanto, su planificación y desarrollo deben realizarse a partir de trabajos interdisciplinares que permitan proyectar la experiencia del ser humano.

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Molecular characterization of two papaya ringspot virus isolates that cause devastating symptoms in Norte de Santander, Colombia
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Chaves-Bedoya, Giovanni | 2017-01-06

Papaya ringspot virus is an RNA virus that belongs to the genus Potyvirus, family Potyviridae and affects both papaya and cucurbits, causing great economic losses. PRSV isolates are divided into biotypes P and W; both biotypes naturally infect plants in the family Cucurbitaceae, whereas the P type also naturally infects papaya (Carica papaya L). In the present study, we report the full-length genome sequence of two PRSV-P isolates sampled from the Campo Hermoso (PRSV-CH) and Villa del Rosario (PRSV-VR) localities in Norte de Santander, Colombia. The genomes of these PRSV isolates are 10,326 nt in length and have a predicted ORF of 3344 aa. The identity among Colombian PRSV isolates is 96.9% and 97.3% at the nucleotide and deduced amino acid levels, respectively. PRSV isolates from China had the lowest identity at 78.3% and 89.2% (nucleotide-amino acid), whereas the highest identities were detected in PRSV isolates from Mexico, Venezuela and Hawaii. At the polyprotein level, the amino acid composition surrounding the active polyprotein cleavage sites differ in the Colombian PRSV sequences. The predicted cleavage site in P1/HC-Pro is LEQY/N – LEQY/S instead of MEQY/N. Both of the Colombian PRSV isolates have a putative recombination event in the P1 coding region, which is common in all PRSV isolates from the American continent. The new full-length PRSV sequences from Colombia provide a better understanding of the dynamics of papaya ringspot virus infections in papaya in Colombia and worldwide.

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Assessment of the strategies adopted by teachers in the teaching of science from the perspective of basic education students
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VELOZA RINCÓN, RAMIRO ALEJANDRO | 2018-06-25

Objective: to characterize and assess the level of development in pedagogical competences through the strategies adopted by Basic Education teachers in the teaching of science from the students’ perspective. Methodology: A quantitative approach was applied which was of a descriptive and multifactorial nature. The data was collected among the eighth and ninth grade students of the Santiago Apóstol Educational Institution, municipality of Santiago, Norte de Santander, Colombia. A Likert scale was used for students to describe the pedagogical practice of teachers in the area of Natural Sciences including the three aspects that are assessed in the development of pedagogical competence: curricular planning, curriculum development and curriculum assessment (monitoring and improvement). Results: the statistical tests show that teachers develop reflective pedagogical practices which require reinforcement in the Research Based Instructional Strategy (RBIS) and in Information and Communication Technologies (ICT) leading to the development of more assertive scientific competences. Conclusions: strategies were identified to foster the development of scientific competences in students and the use of didactic resources and laboratory practices, however, they are not articulated to the needs of students.

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Caracterización Térmica de mezclas de arcillas utilizadas en la fabricación de productos de mampostería para la contrucción
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García León, Ricardo Andrés | 2018

Actualmente en Norte de Santander existe gran variedad de yacimientos naturales que se pueden utilizar para fabricar productos de mampostería para la construcción como lo son bloques, tejas, ladrillos, baldosas, entre otros; pero las empresas fabricantes obtienen muchos desperdicios debido a la falta de análisis tecnológicos de la materia prima para pronosticar el comportamiento de las pastas cerámicas y lograr mejorar la calidad del producto final. En el presente trabajo se realizó las caracterizaciones térmicas de dos mezclas de arcillas (m7 y m8) encontradas experimentalmente utilizando el método de moldeo de extrusión y en polvo para la fabricación de bloques H-10 tomando como muestra la materia prima (arcilla) de una empresa dedicada a la fabricación de bloques H-10 en Ocaña, Norte de Santander. El desarrollo de la investigación se llevó a cabo mediante la ejecución de ensayos térmicos a las muestras de arcillas con los que se determinaron los porcentajes pérdida de peso respecto a las temperaturas obtenidas en un diagrama con las curvas de ATD y ATG. Los resultados obtenidos demuestran que las mezcla m7 encontrada experimentalmente presenta mejores características en el proceso de cocción por lo que se estableció una curva de cocción óptima para la fabricación del bloque H-10 teniendo en cuenta las especificaciones del proceso productivo y la materia prima, con lo que se espera mejorar la calidad del producto final cumpliendo las especificaciones de las normas actuales vigentes. Es indispensable caracterizar las arcillas para optimizar la pasta de producción y evitar imperfecciones en el producto final (Bloque H-10) con lo que evidentemente se mejoraran los recursos ambientales y económicos de la empresa.

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Valoración de las estrategias adoptadas por docentes en la enseñanza de la ciencia desde la perspectiva de los estudiantes de educación básica
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HERNANDEZ SUAREZ, CESAR AUGUSTO | 2018-06-25

Objetivos: caracterizar y evaluar el nivel de desarrollo de las competencias pedagógicas mediante las estrategias adoptadas por docentes de Educación Básica en la enseñanza de la ciencia desde la perspectiva de los estudiantes. Metodología: se aplicó un enfoque metodológico cuantitativo de naturaleza descriptiva y multifactorial. Los datos se obtuvieron entre los estudiantes de octavo y noveno grado de la Institución Educativa Santiago Apóstol, Municipio de Santiago, Norte de Santander, Colombia. Se utilizó una escala Likert diseñada para que los estudiantes describieran la práctica pedagógica de los docentes del área de Ciencias Naturales desde los tres aspectos que se evalúa en el desarrollo de la competencia pedagógica: la planeación curricular, desarrollo curricular y seguimiento y mejora (evaluación curricular). Resultados: las pruebas estadísticas muestran que los docentes desarrollan prácticas pedagógicas reflexivas que requieren de refuerzo en la Estrategia Pedagógica (IEP) y en las Tecnologías de la Información y las Comunicaciones (TIC) que permitan un desarrollo de competencias científicas más asertivas. Conclusiones: se identifican estrategias que promueven el desarrollo de competencias científicas en los estudiantes y se devela la utilización de recursos didácticos y prácticas de laboratorio que, sin embargo, no están articulados con las necesidades de los estudiantes.

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Transcriptional changes involved in kumquat (Fortunella spp) defense response to Xanthomonas citri subsp. citri in early stages of infection
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GIRALDO GONZALEZ, JHON JAIRO | 2021-12

Xanthomonas citri subsp. citri (Xcc), the causal agent of type A canker, differentially affects all commercial varieties of citrus plants. Among them, Fortunella spp (kumquat) have higher tolerance to disease development, although the molecular mechanisms involved in their defense are not fully understood. In this study, using RNA-seq approach, the transcriptional responses of kumquat leaves at 24 h after water (controls) and Xcc inoculation were analyzed. A total of 1439 Differentially expressed genes (DEG) with statistical significance (p-value<0.025) were identified, with 444 being upregulated. These genes were found to be involved in pathogen recognition, cell wall remodeling and reinforcement, lignin biosynthesis, reactive oxygen species (ROS) production, pathogenesis-related proteins (PR) and biosynthesis of secondary metabolites including phenylpropanoids, terpenoids and alkaloids. Genes related to disease resistance (R genes) and salicylic acid (SA)-dependent systemic acquired resistance (SAR) were also induced. In turn, the 995 downregulated genes were mainly associated with photosynthesis, photorespiration, chlorophyll synthesis and cell growth. This suggest that, once the pathogen is detected, the plant generates a strong oxidative burst and its cellular machinery is directed towards the synthesis of secondary metabolites and defense proteins while its own growth is inhibited. Overall, these transcriptional changes provide valuable information about the molecular basis of the defense in kumquat plants, which may be useful in the design of new control methods for citrus canker.

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Exergetic Evaluation of a Rankine Cycle with Regeneration: Effect of Turbine Inlet Temperature and Source Temperature
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Arrieta Mondragón, Leonardo | 2018

The Rankine cycle is a thermodynamic cycle widely used in power plants, specifically in steam power plants, due to its great importance in the industry. It has also been studied in recent years in search of parameters that can optimize the cycle by reducing losses and thus increase efficiency, so that improvements have been made in the process such as overheating of steam at the turbine inlet, and even regeneration of water at the boiler inlet. In this work a process of optimization of a Rankine cycle was presented by complementing it with an open feed water heater which not only improves the efficiency of the cycle, but also provides a convenient means of de-aeration of the feed water to prevent corrosion in the boiler, in which it was carried out under the assumption of a stationary flow, and without significant changes in the kinetic and potential energy, that is, assuming an ideal process, all this with the aim of obtaining the highest thermal efficiency and the lowest exergetic losses in the cycle, carrying out several case studies with the assistance of Unisim with temperature variations at the turbine inlet and at the source to observe how this affects the exergetic efficiency and exergy destroyed in the turbine and it was concluded that this is reflected in the production of mechanical energy useful for creating electrical energy because a variation in these parameters could cause job losses in the turbine and decrease in the exergetic efficiency of the system which in turn would lead to a decrease in the network of the system.

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Development of non-conservative mechanical models applied to the low energy impact phenomenon
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Coba Salcedo, Milton Fabian | 2018-07-18

Non-conservative mechanical models are developed to be applied to the low energy impact phenomenon. The analytical description of the proposed models is made and the numerical solution of the system of differential equations is proposed. The impact of materials is undoubtedly the object of research, due to the dynamic condition inherent in the bodies that interact in our universe. That is why we have standardized methodologies for its study, such as Izod and Charpy impact techniques, among others. However, this work places special emphasis on the method of plate bending, which, due to its geometric configuration, interprets real impact situations to which some bodies are subjected, in addition to the low energy technique in which the energy available in the impactor is less than that absorbed in the breaking process, makes it possible to obtain information on the material in the elastic, plastic, initiation and crack propagation range.

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Comparison of the Concentration Factor of Stresses on Flat Sheets with Two Holes with Low and High Speed Voltage Test
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Acevedo Peñaloza, Carlos Humberto | 2018-07-31

The research seeks to determine whether the stress concentration factor for flat plates with two stressed holes varies according to the application speed of the load. The research was developed using the experimental method, with two types of tests, one called low-speed load application and the other called high-speed load application. The behaviour of the theoretical stress concentration factor Kt has been studied on long flat plates with two holes under tension and made of isotropic material, with axial direction for the application of the vertical load. Different values were taken from the centre distance of the holes and it was found that the value of the stress concentrator Kt; for the two tests always tends to values greater than 3.8. A comparison was made between the results obtained and it was determined that there is variation between the values of the Kt factor according to the speed with which the load of the voltage test is applied, with the highest being the Kt with high speed test.

LEER
Administración por valores: Estrategia de mejoramiento del clima organizacional en las empresas
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Acevedo Peñaloza, Carlos Humberto | 2018

Se presentan a continuación los resultados de la investigación sobre la Administración por Valores como estrategia de mejoramiento del clima organizacional empresarial en organizaciones localizadas en la ciudad de Valledupar, cuyo objetivo general fue establecer un programa de Administración por Valores como estrategia de mejoramiento del clima organizacional empresarial para lo cual se identificó la situación actual del clima organizacional que presenta la empresa; se determinó los valores que harán parte del programa de Administración por Valores y diseñan estrategias para la implementación de un programa de Administración por Valores. Para lo anterior se desarrolló un diagnóstico de la situación actual del clima organizacional; se establecen las debilidades, fortalezas, amenazas y oportunidades para el diseño e implementación del programa de Administración por Valores. De acuerdo a lo anterior, Existe la necesidad de formar y crear estrategias de compensación, distintas a las económicas, dentro de las empresas, y que se convierten en elementos motivadores y potenciadores de buen clima organizacional; la implementación del programa Administración por valores, permite generar una mejor actitud de parte de todo el personal de las empresas, desde los administrativos, operarios y comerciales, hacia el trabajo y el relacionamiento entre ellos. Además, en las organizaciones se ha generado una cultura de liderazgo y trabajo en equipo mucho más dinámica y espontánea, permitiendo el empoderamiento y la pertenencia hacia la organización.

LEER
Bibliometric science indicators applied to environmental impacts research
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Peralta-Ruiz, Yeimmy | 2018-08-01

The growth and development of research on environmental impacts in terms of publications such as the Web of Science sample are analyzed during the period 2007-2018 using HistCite to learn about a global ranking, citations, article impact, keywords and research trends in this area. The research trend increased during the years 2014 and 2017. The United States is the country with the highest number of publications. The Journal of Cleaner Production is the journal with the highest number of publications, along with Science of Total Environment and the Environmental impact assemble review.

LEER
Phenomenological modeling and simulation of a textile stenter
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Parra LLanos, John Wilmer | 2020-04-28

Mathematical modeling and simulation of cotton fabric drying in a stenter machine was performed using a finite element method. A standard κ-ɛ turbulence model was coupled with heat/mass transfer in porous media models. A novel approach to simulate all injectors enabled a new perspective of the process and the calculation of local convective coefficients. Three simulations were run: Simulation I reproduced real operational conditions; Simulations II and III estimated the effects of increasing drying air inlet velocity and decreasing translational velocity of the fabric, respectively. The highest drying air velocities occurred at the nozzles on the edges of the injectors, leading to high convective heat and mass transfer coefficients. Results indicated the drying process was not uniform along the fabric’s width. The models were acceptable in realistically predicting the drying of a cotton fabric in a stenter machine and could be useful in optimizing the stenter design considering the final product’s quality and energy consumption.

LEER

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B. Investigación: Envíos recientes

Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties ﻿

Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties ﻿

Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature ﻿

Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester ﻿

Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol ﻿

Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method ﻿

Waterborne star-shaped styrene-alkyd resins ﻿

Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties ﻿

La ciudad como espacio habitado y fuente de socialización ﻿

Molecular characterization of two papaya ringspot virus isolates that cause devastating symptoms in Norte de Santander, Colombia ﻿

Assessment of the strategies adopted by teachers in the teaching of science from the perspective of basic education students ﻿

Caracterización Térmica de mezclas de arcillas utilizadas en la fabricación de productos de mampostería para la contrucción ﻿

Valoración de las estrategias adoptadas por docentes en la enseñanza de la ciencia desde la perspectiva de los estudiantes de educación básica ﻿

Transcriptional changes involved in kumquat (Fortunella spp) defense response to Xanthomonas citri subsp. citri in early stages of infection ﻿

Exergetic Evaluation of a Rankine Cycle with Regeneration: Effect of Turbine Inlet Temperature and Source Temperature ﻿

Development of non-conservative mechanical models applied to the low energy impact phenomenon ﻿

Comparison of the Concentration Factor of Stresses on Flat Sheets with Two Holes with Low and High Speed Voltage Test ﻿

Administración por valores: Estrategia de mejoramiento del clima organizacional en las empresas ﻿

Bibliometric science indicators applied to environmental impacts research ﻿

Phenomenological modeling and simulation of a textile stenter ﻿

Envíos recientes

Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties

Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties

Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature

Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester

Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol

Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method

Waterborne star-shaped styrene-alkyd resins

Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties

La ciudad como espacio habitado y fuente de socialización

Molecular characterization of two papaya ringspot virus isolates that cause devastating symptoms in Norte de Santander, Colombia

Assessment of the strategies adopted by teachers in the teaching of science from the perspective of basic education students

Caracterización Térmica de mezclas de arcillas utilizadas en la fabricación de productos de mampostería para la contrucción

Valoración de las estrategias adoptadas por docentes en la enseñanza de la ciencia desde la perspectiva de los estudiantes de educación básica

Transcriptional changes involved in kumquat (Fortunella spp) defense response to Xanthomonas citri subsp. citri in early stages of infection

Exergetic Evaluation of a Rankine Cycle with Regeneration: Effect of Turbine Inlet Temperature and Source Temperature

Development of non-conservative mechanical models applied to the low energy impact phenomenon

Comparison of the Concentration Factor of Stresses on Flat Sheets with Two Holes with Low and High Speed Voltage Test

Administración por valores: Estrategia de mejoramiento del clima organizacional en las empresas

Bibliometric science indicators applied to environmental impacts research

Phenomenological modeling and simulation of a textile stenter

Portales Institucionales

Functionalization in solution of polypropylene with a maleinized hyperbranched polyol polyester: Structural, thermal, rheological, and mechanical properties

Maleinized Hyperbranched Polyol Polyester: Effect of the Content of Maleic Anhydride in the Structural, Thermal and Rheological Properties

Vibrational Raman modes and particle size analysis of cupric oxide with calcination temperature

Structural, thermal, rheological, morphological and mechanical properties of polypropylene functionalized in molten state with maleinized hyperbranched polyol polyester

Compatibilization of LDPE/PA6 by Using a LDPE Functionalized with a Maleinized Hyperbranched Polyester Polyol

Effect of Calcination Temperature on the Behavior of the Agglomerated Co3O4 Nanoparticles Obtained Through the Sol–Gel Method

Waterborne star-shaped styrene-alkyd resins

Carbazole-Based Hyperbranched Polyester Polyol: Structural, Rheological, Thermal and Optical Properties

La ciudad como espacio habitado y fuente de socialización

Molecular characterization of two papaya ringspot virus isolates that cause devastating symptoms in Norte de Santander, Colombia

Assessment of the strategies adopted by teachers in the teaching of science from the perspective of basic education students

Caracterización Térmica de mezclas de arcillas utilizadas en la fabricación de productos de mampostería para la contrucción

Valoración de las estrategias adoptadas por docentes en la enseñanza de la ciencia desde la perspectiva de los estudiantes de educación básica

Transcriptional changes involved in kumquat (Fortunella spp) defense response to Xanthomonas citri subsp. citri in early stages of infection

Exergetic Evaluation of a Rankine Cycle with Regeneration: Effect of Turbine Inlet Temperature and Source Temperature

Development of non-conservative mechanical models applied to the low energy impact phenomenon

Comparison of the Concentration Factor of Stresses on Flat Sheets with Two Holes with Low and High Speed Voltage Test

Administración por valores: Estrategia de mejoramiento del clima organizacional en las empresas

Bibliometric science indicators applied to environmental impacts research

Phenomenological modeling and simulation of a textile stenter