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Ítem Indentation damage and crack repair in human enamel.(ELSEVIER SCIENCE BV, 2013-05-01) Rivera C; Arola D; Ossa A; Rivera C; Arola D; Ossa A; Universidad EAFIT. Departamento de Ingeniería de Producción; Materiales de IngenieríaTooth enamel is the hardest and most highly mineralized tissue in the human body. While there have been a number of studies aimed at understanding the hardness and crack growth resistance behavior of this tissue, no study has evaluated if cracks in this tissue undergo repair. In this investigation the crack repair characteristics of young human enamel were evaluated as a function of patient gender and as a function of the distance from the Dentin Enamel Junction (DEJ). Cracks were introduced via microindentation along the prism direction and evaluated as a function of time after the indentation. Microscopic observations indicated that the repair of cracks began immediately after crack initiation and reaches saturation after approximately 48 h. During this process he crack length decreased up to 10% of the initial length, and the largest degree of reduction occurred in the deep enamel, nearest the DEJ. In addition, it was found that the degree of repair was significantly greater in the enamel of female patients.Ítem Scale-up from shake flasks to pilot-scale production of the plant growth-promoting bacterium Azospirillum brasilense for preparing a liquid inoculant formulation(SPRINGER, 2013-11-01) Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)Azospirillum brasilense has industrial significance as a growth promoter in plants of commercial interest. However, there is no report in the literature disclosing a liquid product produced in pilot-scale bioreactors and is able to be stored at room temperature for more than 2 years. The aim of this work was to scale up a process from a shake flask to a 10-L lab-scale and 1,000-L pilot-scale bioreactor for the production of plant growth-promoting bacterium A. brasilense for a liquid inoculant formulation. Furthermore, this work aimed to determine the shelf life of the liquid formulation stored at room temperature and to increase maize crops yield in greenhouses. Under a constant oxygen mass transfer coefficient (K L a), a fermentation process was successfully scaled up from shake flasks to 10- and 1,000-L bioreactors. A concentration ranging from 3.5 to 7.5 × 108 CFU/mL was obtained in shake flasks and bioreactors, and after 2 years stored at room temperature, the liquid formulation showed one order of magnitude decrease. Applications of the cultured bacteria in maize yields resulted in increases of up to 95 % in corncobs and 70 % in aboveground biomass. © 2013 Springer-Verlag Berlin Heidelberg.Ítem Scale-up from shake flasks to pilot-scale production of the plant growth-promoting bacterium Azospirillum brasilense for preparing a liquid inoculant formulation(SPRINGER, 2013-11-01) Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Trujillo-Roldan, Mauricio A.; Valdez-Cruz, Norma A.; Gonzalez-Monterrubio, Cesar F.; Acevedo-Sanchez, Eduardo V.; Martinez-Salinas, Carlos; Garcia-Cabrera, Ramses I.; Gamboa-Suasnavart, Ramses A.; Marin-Palacio, Luz D.; Villegas, Jesus; Blancas-Cabrera, Abel; Universidad EAFIT. Departamento de Ingeniería de Procesos; Procesos Ambientales (GIPAB)Azospirillum brasilense has industrial significance as a growth promoter in plants of commercial interest. However, there is no report in the literature disclosing a liquid product produced in pilot-scale bioreactors and is able to be stored at room temperature for more than 2 years. The aim of this work was to scale up a process from a shake flask to a 10-L lab-scale and 1,000-L pilot-scale bioreactor for the production of plant growth-promoting bacterium A. brasilense for a liquid inoculant formulation. Furthermore, this work aimed to determine the shelf life of the liquid formulation stored at room temperature and to increase maize crops yield in greenhouses. Under a constant oxygen mass transfer coefficient (K L a), a fermentation process was successfully scaled up from shake flasks to 10- and 1,000-L bioreactors. A concentration ranging from 3.5 to 7.5 × 108 CFU/mL was obtained in shake flasks and bioreactors, and after 2 years stored at room temperature, the liquid formulation showed one order of magnitude decrease. Applications of the cultured bacteria in maize yields resulted in increases of up to 95 % in corncobs and 70 % in aboveground biomass. © 2013 Springer-Verlag Berlin Heidelberg.Ítem Synthesis and characterization of magnetite-maghemite nanoparticles obtained by the high-energy ball milling method(Springer Netherlands, 2018-03-13) Velásquez, A. A.; Marín, C; Urquijo, P; Universidad EAFIT. Departamento de Ciencias Básicas; Electromagnetismo Aplicado (Gema)We present the process of synthesis and characterization of magnetite-maghemite nanoparticles by the ball milling method. The particles were synthesized in a planetary ball mill equipped with vials and balls of tempered steel, employing dry and wet conditions. For dry milling, we employed microstructured analytical-grade hematite (a-Fe2O3), while for wet milling, we mixed hematite and deionized water. Milling products were characterized by X-ray diffraction, transmission electron microscopy, room temperature Mössbauer spectroscopy, vibrating sample magnetometry, and atomic absorption spectroscopy. The Mössbauer spectrum of the dry milling product was well fitted with two sextets of hematite, while the spectrum of the wet milling product was well fitted with three sextets of spinel phase. X-ray measurements confirmed the phases identified by Mössbauer spectroscopy in both milling conditions and a reduction in the crystallinity of the dry milling product. TEM measurements showed that the products of dry milling for 100 h and wet milling for 24 h consist of aggregates of nanoparticles distributed in size, with mean particle size of 10 and 15 nm, respectively. Magnetization measurements of the wet milling product showed little coercivity and a saturation magnetization around 69 emu g-1, characteristic of a nano-spinel system. Atomic absorption measurements showed that the chromium contamination in the wet milling product is approximately two orders of magnitude greater than that found in the dry milling product for 24 h, indicating that the material of the milling bodies, liberated more widely in wet conditions, plays an important role in the conversion hematite-spinel phase. © 2018, Springer Science+Business Media B.V., part of Springer Nature.