This paper describes a methodology of photopolymer mold fabrication with multi-level microstructu... more This paper describes a methodology of photopolymer mold fabrication with multi-level microstructures for polydimethylsiloxane (PDMS) microfluidic device manufacture.
Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite i... more Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite in water using a pulsed Nd:YAG laser (1064 nm) with a width of 8 ns. Structural and mesoscopic characterization of the CNPs in the supernatant by Raman spectroscopy provide evidence for the presence of mainly two ranges of particle sizes: 1-5 nm and 10-50 nm corresponding to amorphous carbon and graphite NPs, respectively. These results are corroborated by complementary characterization using atomic force microscopy (AFM) and transmission electron microscopy (TEM). In addition, large (10-100 µm) graphite particles removed from the surface are essentially unmodified (in structure and topology) by the laser as confirmed by Raman analysis.
Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magm... more Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It is typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety of shiny metallic colors on its surface ranging from blue to gold to silver. The origin of these colors has remained unknown up to now. Cinder samples from an eruptive event occurred in October 2005 have been collected in the surroundings of the Sierra Negra volcano in the Galápagos Islands. The samples’ crystallographic structure, chemical composition, and surface morphology have been analyzed using X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and a field gun emission scanning electron microscopy (SEM), respectively. Based on an extensive physical and chemical analysis, we were able to demonstrate that these colors are due to a light interference phenomenon. These resu...
In this work we have analyzed the dynamic behavior of steel reinforcing bars under low cycle forc... more In this work we have analyzed the dynamic behavior of steel reinforcing bars under low cycle force-controlled fatigue measurements. We compare the results obtained for rebars produced by three steel companies of Ecuador, which fulfill the technical requirements of the national standards specified in ASTM A706. The measurements were carried out by using an universal testing machine model MTS 810. To determine the critical factors on the dynamic response of reinforcing bars, we have characterized the fractured section by macroscopic parameters and employing the Scanning Electron Microscopy (SEM). The results obtained point out that, although the three companies produce rebars with similar static behavior exist important differences on their dynamical properties.
Revista Colombiana de Ciencias Químico-Farmacéuticas
El objetivo de esta investigación fue microencapsular aceite de sacha inchi mediantesecado por as... more El objetivo de esta investigación fue microencapsular aceite de sacha inchi mediantesecado por aspersión, con el fin de evitar las reacciones oxidativas de degradación,dado su alto contenido de ácidos grasos monoinsaturados y poliinsaturados, loscuales presentan grandes beneficios para la salud. Empleando maltodextrina y gomaarábiga en una proporción ( 1:1 ), se evaluó la temperatura de entrada y la carga deaceite, siendo 150 °C y 33% las mejores condiciones de trabajo durante el procesode secado. Se obtuvo un rendimiento y eficiencia de microencapsulación de 82,10 ±0,99% y 93,90 ± 0,56%, respectivamente. Cabe mencionar que esta investigación esla primera en emplear la técnica de secado por aspersión, y como agentes formadoresde la pared polimérica la mezcla de maltodextrina y goma arábiga en la microencapsulaciónde aceite de sacha inchi. Mediante análisis fisicoquímico, se evaluó lahumedad del aceite de sacha inchi microencapsulado, manteniendo un contenidode humedad a las 26 seman...
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Mortino (Vaccinium floribundum Kunth) is a wild shrub native to South America, whose ber... more Abstract Mortino (Vaccinium floribundum Kunth) is a wild shrub native to South America, whose berries are widely consumed in Ecuador as fresh fruit, juice and jam. We reported a green synthesis of Silver–Graphene (Ag-G) nanocomposite through the reduction of Ag+ and graphene oxide using berry extract of Mortino. Silver nanoparticles were anchored onto the graphene sheets by ultrasonication and solar light irradiation. The as-prepared Ag-G nanocomposite was characterized by Fourier transform infrared spectroscopy, UV–vis spectroscopy, Scanning transmission electron microscopy, Scanning electron microscopy with energy dispersive X-ray spectrometry, and X-ray diffraction techniques. The photocatalytic activities of the Ag-G nanocomposite were evaluated by the degradation of methylene blue (MB) and methylene orange (MO) in an aqueous medium under sunlight irradiation. The photocatalytic activity of Ag-G nanocomposite for the degradation of MB (k = 0.0163283 min−1) > MO (k = 0.0140985 min−1), due to the anchoring of Ag nanoparticles on the graphene sheets and thiazine ring of MB is more susceptible to photodegradation than the azo bond of MO. This ecofriendly and green reduction method avoids the use of toxic reagents, and it might be useful for biocompatible materials in the future engineering applications.
Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magm... more Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It is typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety of shiny metallic colors on its surface ranging from blue to gold to silver. The origin of these colors has remained unknown up to now. Cinder samples from an eruptive event occurred in October 2005 have been collected in the surroundings of the Sierra Negra volcano in the Galápagos Islands. The samples’ crystallographic structure, chemical composition, and surface morphology have been analyzed using X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and a field gun emission scanning electron microscopy (SEM), respectively. Based on an extensive physical and chemical analysis, we were able to demonstrate that these colors are due to a light interference phenomenon. These results have a great potential to be used for a wide variety of purposes such as determining the temperature and composition of magma and evaluating volcanic samples for planetary studies.
This paper describes a methodology of photopolymer mold fabrication with multi-level microstructu... more This paper describes a methodology of photopolymer mold fabrication with multi-level microstructures for polydimethylsiloxane (PDMS) microfluidic device manufacture.
Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite i... more Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite in water using a pulsed Nd:YAG laser (1064 nm) with a width of 8 ns. Structural and mesoscopic characterization of the CNPs in the supernatant by Raman spectroscopy provide evidence for the presence of mainly two ranges of particle sizes: 1-5 nm and 10-50 nm corresponding to amorphous carbon and graphite NPs, respectively. These results are corroborated by complementary characterization using atomic force microscopy (AFM) and transmission electron microscopy (TEM). In addition, large (10-100 µm) graphite particles removed from the surface are essentially unmodified (in structure and topology) by the laser as confirmed by Raman analysis.
Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magm... more Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It is typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety of shiny metallic colors on its surface ranging from blue to gold to silver. The origin of these colors has remained unknown up to now. Cinder samples from an eruptive event occurred in October 2005 have been collected in the surroundings of the Sierra Negra volcano in the Galápagos Islands. The samples’ crystallographic structure, chemical composition, and surface morphology have been analyzed using X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and a field gun emission scanning electron microscopy (SEM), respectively. Based on an extensive physical and chemical analysis, we were able to demonstrate that these colors are due to a light interference phenomenon. These resu...
In this work we have analyzed the dynamic behavior of steel reinforcing bars under low cycle forc... more In this work we have analyzed the dynamic behavior of steel reinforcing bars under low cycle force-controlled fatigue measurements. We compare the results obtained for rebars produced by three steel companies of Ecuador, which fulfill the technical requirements of the national standards specified in ASTM A706. The measurements were carried out by using an universal testing machine model MTS 810. To determine the critical factors on the dynamic response of reinforcing bars, we have characterized the fractured section by macroscopic parameters and employing the Scanning Electron Microscopy (SEM). The results obtained point out that, although the three companies produce rebars with similar static behavior exist important differences on their dynamical properties.
Revista Colombiana de Ciencias Químico-Farmacéuticas
El objetivo de esta investigación fue microencapsular aceite de sacha inchi mediantesecado por as... more El objetivo de esta investigación fue microencapsular aceite de sacha inchi mediantesecado por aspersión, con el fin de evitar las reacciones oxidativas de degradación,dado su alto contenido de ácidos grasos monoinsaturados y poliinsaturados, loscuales presentan grandes beneficios para la salud. Empleando maltodextrina y gomaarábiga en una proporción ( 1:1 ), se evaluó la temperatura de entrada y la carga deaceite, siendo 150 °C y 33% las mejores condiciones de trabajo durante el procesode secado. Se obtuvo un rendimiento y eficiencia de microencapsulación de 82,10 ±0,99% y 93,90 ± 0,56%, respectivamente. Cabe mencionar que esta investigación esla primera en emplear la técnica de secado por aspersión, y como agentes formadoresde la pared polimérica la mezcla de maltodextrina y goma arábiga en la microencapsulaciónde aceite de sacha inchi. Mediante análisis fisicoquímico, se evaluó lahumedad del aceite de sacha inchi microencapsulado, manteniendo un contenidode humedad a las 26 seman...
Journal of Photochemistry and Photobiology A: Chemistry, 2016
Abstract Mortino (Vaccinium floribundum Kunth) is a wild shrub native to South America, whose ber... more Abstract Mortino (Vaccinium floribundum Kunth) is a wild shrub native to South America, whose berries are widely consumed in Ecuador as fresh fruit, juice and jam. We reported a green synthesis of Silver–Graphene (Ag-G) nanocomposite through the reduction of Ag+ and graphene oxide using berry extract of Mortino. Silver nanoparticles were anchored onto the graphene sheets by ultrasonication and solar light irradiation. The as-prepared Ag-G nanocomposite was characterized by Fourier transform infrared spectroscopy, UV–vis spectroscopy, Scanning transmission electron microscopy, Scanning electron microscopy with energy dispersive X-ray spectrometry, and X-ray diffraction techniques. The photocatalytic activities of the Ag-G nanocomposite were evaluated by the degradation of methylene blue (MB) and methylene orange (MO) in an aqueous medium under sunlight irradiation. The photocatalytic activity of Ag-G nanocomposite for the degradation of MB (k = 0.0163283 min−1) > MO (k = 0.0140985 min−1), due to the anchoring of Ag nanoparticles on the graphene sheets and thiazine ring of MB is more susceptible to photodegradation than the azo bond of MO. This ecofriendly and green reduction method avoids the use of toxic reagents, and it might be useful for biocompatible materials in the future engineering applications.
Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magm... more Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It is typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety of shiny metallic colors on its surface ranging from blue to gold to silver. The origin of these colors has remained unknown up to now. Cinder samples from an eruptive event occurred in October 2005 have been collected in the surroundings of the Sierra Negra volcano in the Galápagos Islands. The samples’ crystallographic structure, chemical composition, and surface morphology have been analyzed using X-Ray diffractometry (XRD), energy dispersive X-Ray spectroscopy (EDS) and a field gun emission scanning electron microscopy (SEM), respectively. Based on an extensive physical and chemical analysis, we were able to demonstrate that these colors are due to a light interference phenomenon. These results have a great potential to be used for a wide variety of purposes such as determining the temperature and composition of magma and evaluating volcanic samples for planetary studies.
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