Evaluación de las variedades de látex de caucho natural colombiano IAN 710, IAN 873 y FX 3864

RESUMEN: Se evalúa látex de caucho natural -estabilizado- de las variedades clonales IAN 710, IAN 873 y FX 3864, cultivadas en el Municipio de Tarazá- Vereda Santa Clara, Bajo Cauca Antioqueño, durante el estado fenológico de floración con el fin de identificar las diferencias que presenta cada clon en las propiedades físico-químicas del látex. A las muestras de cada variedad clonal, se les realizó una caracterización térmica, medición de la distribución de tamaño de las partículas, análisis morfológico y algunas propiedades físico-químicas. Se identificaron diferencias entre los clones debido al componente considerado no-caucho y en el tamaño de las partículas

Constraints on redshifts of blazars from extragalactic background light attenuation using Fermi-LAT data

The extragalactic high-energy $\gamma$-ray sky is dominated by blazars, which are active galactic nuclei with their jets pointing towards us. Distance measurements are of fundamental importance yet for some of these sources are challenging because any spectral signature from the host galaxy may be outshone by the non-thermal emission from the jet. In this paper, we present a method to constrain redshifts for these sources that relies only on data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This method takes advantage of the signatures that the pair-production interaction between photons with energies larger than approximately 10 GeV and the extragalactic background light leaves on $\gamma$-ray spectra. We find upper limits for the distances of 303 $\gamma$-ray blazars, classified as 157 BL Lacertae objects, 145 of uncertain class, and 1 flat-spectrum-radio quasar, whose redshifts are otherwise unknown. These derivations can be useful for planning observations with imaging atmospheric Cherenkov telescopes and also for testing theories of supermassive black hole evolution. Our results are applied to estimate the detectability of these blazars with the future Cherenkov Telescope Array, finding that at least 21 of them could be studied in a reasonable exposure of 20 h.Comment: 13 pages, 7 figures, 1 table; Accepted by MNRA

Propuestas del Foco de Tecnologías Convergentes e Industrias 4.0

La colección Colombia hacia una sociedad del conocimiento reúne las contribuciones de la Misión Internacional de Sabios 2019 sobre Educación, Ciencia, Tecnología e Innovación, convocada por el Presidente de la República. Este volumen corresponde a las contribuciones realizadas por el Foco de Tecnologías Convergentes -Nano, Bio, Info y Cogno- e Industrias 4.0, cuyas recomendaciones sobre la educación, la infraestructura digital estratégica, la inversión inteligente, la innovación para crear valor y equidad, la atracción de capital privado y talento internacional, la política pública acompañada de regulaciones modernas, entre otros pilares, conforman una arquitectura crítica para la innovación y la oportunidad global para el país.Vicepresidencia de la República de Colombia, Universidad EAFIT, Universidad del Vall

Sensitivity of the Cherenkov Telescope Array to spectral signatures of hadronic PeVatrons with application to Galactic Supernova Remnants

The local Cosmic Ray (CR) energy spectrum exhibits a spectral softening at energies around 3~PeV. Sources which are capable of accelerating hadrons to such energies are called hadronic PeVatrons. However, hadronic PeVatrons have not yet been firmly identified within the Galaxy. Several source classes, including Galactic Supernova Remnants (SNRs), have been proposed as PeVatron candidates. The potential to search for hadronic PeVatrons with the Cherenkov Telescope Array (CTA) is assessed. The focus is on the usage of very high energy $\gamma$-ray spectral signatures for the identification of PeVatrons. Assuming that SNRs can accelerate CRs up to knee energies, the number of Galactic SNRs which can be identified as PeVatrons with CTA is estimated within a model for the evolution of SNRs. Additionally, the potential of a follow-up observation strategy under moonlight conditions for PeVatron searches is investigated. Statistical methods for the identification of PeVatrons are introduced, and realistic Monte--Carlo simulations of the response of the CTA observatory to the emission spectra from hadronic PeVatrons are performed. Based on simulations of a simplified model for the evolution for SNRs, the detection of a $\gamma$-ray signal from in average 9 Galactic PeVatron SNRs is expected to result from the scan of the Galactic plane with CTA after 10 hours of exposure. CTA is also shown to have excellent potential to confirm these sources as PeVatrons in deep observations with $\mathcal{O}(100)$ hours of exposure per source.Comment: 34 pages, 16 figures, Accepted for publication in Astroparticle Physic

Water-based adhesive formulations for rubber to metal bonding developed by statistical design of experiments

Waterborne adhesives for rubber to metal bonding have been available since 1990. However, published information about their formulation has been limited, as proprietary restrictions are exercised by companies. As a consequence, the way these adhesives interact with substrates has not been studied extensively. With the aim of investigating the effect the components of a waterborne adhesive have on rubber to metal bonding, fractional factorial and surface response methodologies of design of experiments were employed in this study. Twenty six formulations were prepared with a polychloroprene latex as the adhesive polymer. Viscosity, wettability and non-volatile solids content were measured with each liquid adhesive, while the mechanical strength was evaluated by applying a tensile mechanical stress over cured solid adhesive films. Adhesion properties were evaluated by using a single lap-shear test on metal to metal joints and a pull-out test on rubber to metal joints. The results showed that the components with the largest relative influence on cohesive and adhesives forces were tackifier resin, silicon dioxide and polychloroprene latex type. In order to better understand the contributions of these variables, mathematical models correlating them with the response variables were obtained. This study is valuable in explaining how, through statistical methods, a waterborne adhesive for rubber to metal bonding can be formulated with a reasonably low number of experiments. © 2016 Elsevier Lt

Morphology Development of Immiscibe Quaternary Polyolefin and PS Blends

Study of polymer blends that fulfill the current engineering demand has been increased in the last years and multicomponent blends are still a challenge, but increasing the number of components will lead to further complications. We correlated the differences between morphology and blending sequence in quaternary blends of polyolefin with polystyrene, following the available theories that related viscosity and morphology. It was found that high viscous matrices enhance deformation and breakup processes, displaying fibrillar morphologies and finer dispersions. The blending sequence improves the mixing first, by putting all the polyolefin into a ternary blend and after that, adding the polystyrene

Tailoring the mechanical, thermal, and flammability properties of high-performance PEI/PBT blends exhibiting dual-phase continuity

Binary PEI/PBT blends are prepared using a two-step melt processing method. Miscibility study by MDSC and DMA reveals partial miscibility, and new evidence on the morphological evolution of PEI/PBT blends is presented. Two groups of blends are recognized: PBT-rich blends and PEI-rich blends, as well as phase inversion at concentrations close to 50 wt% of PEI. Mechanical, thermal, and flame resistance performance is influenced by blends morphology, and an opportunity for tailoring blends properties is recognized. Tensile modulus shows synergic contribution for 50/50 and 80/20 blends and yield strength is strongly affected by interfacial adherence between constituents. In addition, elongation at break is compromised by PBT-rich blends morphology, and by PEI-rich blends densification. The 50/50 blend exhibits the best elongational at break result due to its co-continuous morphology. Thermal stability and flammability tests reveal that PEI improves the thermal resistance and charring of PBT, particularly for 50/50 blend. © 2018 Elsevier Lt

Correlations between thermal and tensile behavior with friction coefficient in copolyamides 6/12

Although polyamide 6 (PA6) obtained from e-caprolactame (CL) is an engineering polymer with outstanding properties used in sliding applications, it exhibits low impact strength and high water absorption. Those are some of the reasons why copolymerization between CL and laurolactame (LL) is desired. In this work, copolymers from 0–100 wt% LL are prepared to evaluate crystallinity, melting behavior, tensile properties and those properties are correlated with coefficient of friction. Experimental results show that PA6 (0 wt%) crystallinity and elasticity modulus are higher than those obtained from 100 wt%LL (PA12), but friction coefficient in PA6 is lower than that of PA12. While with 60 wt% LL crystallinity and elastic modulus reach a minimum value, with 350% elongation and coefficient of friction they register a maximum value. Our results suggest that crystallinity and elastic modulus are opposed to coefficient of friction. The absence of hydrogen bonds produces irregularities in the chain, reducing the crystal formation; such behavior is a consequence of copolymerization. Our findings will help to customize copolyamide, modulate the response between mechanical properties and friction behavior, as well as evaluate when it is necessary to add lubricants in the copolymer formulations. © 2016 Elsevier B.V