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Estadística descriptiva para trabajos de investigación: presentación e interpretación de los resultados
No full textBusca acercar a las personas que se inician en el desarrollo de una investigación a los principales elementos del análisis estadístico descriptivo. Menciona que la estadística es una herramienta indispensable para el análisis de datos de una investigación, por ello, el investigador debe comprender los conceptos estadísticos básicos y seleccionar de manera adecuada aquellos que le servirán para presentar y analizar sus resultados. Asimismo, explica términos estadísticos de forma sencilla complementados con ejemplos básicos, pero importantes para reforzar los conceptos y su aplicación pertinente dentro del tratamiento estadístico de acuerdo con el objetivo de un trabajo de investigación
Rotational molding parameters of wood-plastic composite materials made of recycled high density polyethylene and wood particles
No full textRecent investigations have demonstrated that it is possible to incorporate different natural fibers in the rotational molding process. In this perspective, the main purpose of this work is to study the influence of rotational molding parameters on the sintering process of composite materials made of recycled high density polyethylene and wood particles. To achieve this, an experimental procedure of three molding stages was elaborated to make wood-plastic composite materials. At each stage, it was studied the effect of a certain molding parameter on mechanical properties, while the other parameters remain constant during the molding process. The composite materials made during each stage were tensile tested to identify which of them have suitable mechanical properties and to find the most convenient molding parameters for making them. Using a stereoscope, pictures of composite materials' morphologies were taken to study the degree of sintering and determine its influence on mechanical properties. Results show that there is a very close relationship among composite materials’ morphologies, degree of sintering, rotational molding parameters and mechanical properties. In addition, it has been found that composite materials that reached the most convenient properties have a tensile strength which decreases up to 17% and an elastic modulus which increases up to 16%, in regard to a material made of neat recycled polyethylene that was molded under the same conditions. © 2021 Elsevier LtdFondo Nacional de Desarrollo Científico y Tecnológico - Fondecy
Total attenuation compensation for backscatter coefficient estimation using full angular spatial compounding
No full textThe backscatter coefficient (BSC) quantifies the frequency-dependent reflectivity of tissues. Accurate estimation of the BSC is only possible with the knowledge of the attenuation coefficient slope (ACS) of the tissues under examination. In this study, the use of attenuation maps constructed using full angular spatial compounding (FASC) is proposed for attenuation compensation when imaging integrated BSCs. Experimental validation of the proposed approach was obtained using two cylindrical physical phantoms with off-centered inclusions having different ACS and BSC values than the background, and in a phantom containing an ex vivo chicken breast sample embedded in an agar matrix. With the phantom data, three different ACS maps were employed for attenuation compensation: (1) a ground truth ACS map constructed using insertion loss techniques, (2) the estimated ACS map using FASC attenuation imaging, and (3) a uniform ACS map with a value of 0.5 dBcm\protect \relax \special {t4ht=?}1MHz\protect \relax \special {t4ht=?}1, which is commonly used to represent attenuation in soft tissues. Comparable results were obtained when using the ground truth and FASC-estimated ACS maps in term of inclusion detectability and estimation accuracy, with averaged fractional error below 2.8 dB in both phantoms. Conversely, the use of the homogeneous ACS map resulted in higher levels of fractional error (>10 dB), which demonstrates the importance of an accurate attenuation compensation. The results with the ex vivo tissue sample were consistent with the observations using the physical phantoms, with the FASC-derived ACS map providing comparable BSC images to those formed using the ground truth ACS map and more accurate than those BSC images formed using a uniform ACS. These results suggest that BSCs can be reliably estimated using FASC when a self-consistent attenuation compensation stemming from prior estimation of an accurate ACS map is used. © 2021 Elsevier B.V.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
Type 3 secretion system as an anti-Pseudomonal target
No full textType 3 secretion systems (T3SSs) are a series of mechanisms involved in bacterial pathogenesis. While Pseudomonas aeruginosa only possess one T3SS, it plays a key role in the virulence of P. aeruginosa virulence. This finding suggests that T3SS impairment may be an alternative for antimicrobial agents, allowing P. aeruginosa infections to be directly combated avoiding antimicrobial pressure on this and other microorganisms. To date, different approaches have been proposed, including T3SS inhibition, vaccination strategies, development of anti-T3SS antibodies and gene silencing. © 2021 Elsevier LtdConsejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
Surface molecularly imprinted core-shell nanoparticles and reflectance spectroscopy for direct determination of tartrazine in soft drinks
No full textThe present work shows the synergistic application of reflectance spectroscopy and core-shell molecularly imprinted polymer (MIP) for rapid quantification of tartrazine in soft drinks. Studies evaluated the performance of the MIPs synthesized in the presence of silica nanoparticles unfunctionalized and functionalized with [3-(methacryloyloxy)propyl]trimethoxysilane. Although the use of functionalized silica nanoparticles promoted the highest adsorption capability of tartrazine, the material was found to be less selective when it was applied in real samples. Interestingly, the most accurate results were obtained via the application of the MIP synthesized in the presence of unfunctionalized silica nanoparticles (SiO2@MIP). The optimized core-shell MIP was also characterized by Raman spectroscopy and scanning electron microscopy. The use of direct reflectance spectroscopy in the analyte detection strategy after the template extraction from the MIPs resulted in faster and more accurate results than conventional UV–Visible spectroscopy. With regard to the analysis of the soft drink samples, no significant differences were found between the results obtained from the proposed reflectance spectroscopy-based technique and those obtained from the comparative high-performance liquid chromatography technique. Under optimized conditions, this method displayed a linear range of 1.0–12.5 ?mol L?1 with LOD and LOQ values of 0.303 and 1.0 ?mol L?1, respectively. The selectivity factor (?) ranged between 1.4 up to 264 showed better recognition of tartrazine in front of other dyes. Based on the results obtained, the proposed method is found to be suitable for rapid determination of tartrazine in food samples with complex matrices without the need of applying tedious sample preparation and cost-demanding instruments. © 2021 Elsevier B.V.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
The Peruvian Amazon forestry dataset: A leaf image classification corpus
No full textForest census allows getting precise data for logging planning and elaboration of the forest management plan. Species identification blunders carry inadequate forest management plans and high risks inside forest concessions. Hence, an identification protocol prevents the exploitation of non-commercial or endangered timber species. The current Peruvian legislation allows the incorporation of non-technical experts, called “materos”, during the identification. Materos use common names given by the folklore and traditions of their communities instead of formal ones, which generally lead to misclassifications. In the real world, logging companies hire materos instead of botanists due to cost/time limitations. Given such a motivation, we explore an end-to-end software solution to automatize the species identification. This paper introduces the Peruvian Amazon Forestry Dataset, which includes 59,441 leaves samples from ten of the most profitable and endangered timber-tree species. The proposal contemplates a background removal algorithm to feed a pre-trained CNN by the ImageNet dataset. We evaluate the quantitative (accuracy metric) and qualitative (visual interpretation) impacts of each stage by ablation experiments. The results show a 96.64% training accuracy and 96.52% testing accuracy on the VGG-19 model. Furthermore, the visual interpretation of the model evidences that leaf venations have the highest correlation in the plant recognition task. © 2021Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
Characterization and antimicrobial activity of microencapsulated citral with dextrin by spray drying
No full textThis work was supported by Fondo Nacional de Desarrollo Científico, Tecnologico y de Innovación Tecnológica (PE) [179-2015-FONDECYT].Aim of this work was to evaluate the antimicrobial activity and physical characteristics of citral microencapsulated with dextrin (Dx) by spray drying. The encapsulation was optimized using response surface methodology (RSM), maximizing yield and efficiency, considering as independent variables the citral:Dx ratio (1:5 and 1:20) and the inlet air temperature (120 and 200 °C). Yield and efficiency under optimal conditions were 71.9% and 99.9%, respectively. Antimicrobial activity against Escherichia coli, Salmonella enterica, Staphylococcus aureus and Bacillus cereus of the citral microparticles obtained under optimal conditions and of free citral was evaluated using the disk diffusion methodology. Both compounds showed a broad spectrum inhibitory effect, being Escherichia coli and Bacillus cereus the most sensitive microorganisms. The inhibition ratio varied between 55 and 75%, and the antibacterial activity was maintained after microencapsulation. The minimum inhibitory concentrations of free citral were above 0.8 mg/mL. The optimal citral microparticles showed acceptable physicochemical characteristics and broad-spectrum antimicrobial activity. Polymer and emulsifier used in microencapsulation protected the functional activity of citral, thus suggesting that these microparticles could be used in the design of antimicrobial food systems to extend the shelf life of perishable foods. © 2021Fondo Nacional de Desarrollo Científico y Tecnológico - Fondecy
Leaf nutrients in Prosopis pallida are determined by soil chemical attributes under eutric conditions in a dryland forest
No full textKey message: Soil pH, EC, and salinity explain the leaf nutrient concentrations of Prosopis pallida despite the high amount of soil nutrients near the trees. Abstract: Dryland forests constantly face extreme abiotic conditions, and this affects plant growth and nutrition. We have determined the effects of soil chemical attributes and soil nutrients on the leaf nutrient concentrations of eight Prosopis pallida populations located along a climatic gradient in the North-Peruvian dryland forests. We analyzed the leaf chemical composition (N, P, K, Ca, Mg, Fe, Mn, Cu, and Zn), as well as soil chemical attributes [texture, pH, salinity (electrical conductivity; EC), and the sodium adsorption ratio (SAR)] and soil nutrient concentrations (the same elements as in the leaves) at 2 m from the base of each tree. The soil and leaf nutrient concentrations were not associated with the climatic gradient and were highly variable within populations. Despite the dry conditions, the soil nutrients were not a limiting resource (eutric conditions), and thus the soil chemical attributes were the main driver of the variation in leaf nutrient concentrations. Interestingly, leaf Mn was correlated with soil and leaf nutrients, as well as with soil chemical attributes, suggesting it can be used as an early indicator of plant nutrition. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
Development and validation of a parameter estimation methodology for two different lithium-ion batteries to optimize their performance and life cycle
No full textThis paper presents four procedures developed to analyse the dependence of the discharge curve of a lithium battery on discharge current and working temperature. For this work, two models of lithium batteries have been used, whose discharge curves have different shapes. The first one, the shape of the curve describes an almost horizontal line in most of it (type 1), while in the other one, the shape of the curve describes a negative slope in most of it (type 2). Two of the developed procedures are used for discharge curves with different currents but constant temperature and the other two developed procedures are used for discharge curves with different temperatures but constant current. The information for the development of the simulations is obtained from the datasheet of the analysed lithium batteries. © 2021 Published under licence by IOP Publishing Ltd.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte
Tuning the magnetic properties of Sn1?x?yCe4+xCe3+yO2nanoparticles: an experimental and theoretical approach
No full textDuring the last decade, there was a substantial increase in the research on metal-doped oxide semiconductor nanoparticles due to advances in the engineering of nanomaterials and their potential application in spintronics, biomedicine and photocatalysis fields. In this regard, doping a nanomaterial is a powerful tool to tune its physicochemical properties. The aim of this work is to shine a new light on the role of the neighbouring elements on the oxidation state of the Ce-impurity, from both experimental and theoretical points of view. Herein, we present an accurate study of the mechanisms involved in the oxidation states of the Ce-ions during the doping process of SnO2nanoparticles (NPs) prepared by the polymeric precursor method. X-ray diffraction measurements have displayed the tetragonal rutile-type SnO2phase in all samples. However, the Bragg’s peak (111) and (220) located at 2??29° and ?47° evidence the formation of a secondary CeO2phase for samples with Ce content up to 10%. X-ray absorption near-edge structure (XANES) measurements, at Ce L3 edge, were performed on the NPs as a function of Ce content. The results show, on one side, the coexistence of Ce3+and Ce4+states in all samples; and on the other side, a clear reduction in the Ce3+population driven by the increase of Ce content. It is shown that this is induced by the neighboring cation, and confirmed by magnetic measurements. The monotonic damping of the Ce3+/Ce4+ratio experimentally, was connected with theoretical calculationsviadensity functional theory by simulating a variety of point defects composed of Ce impurities and surrounding oxygen vacancies. We found that the number of oxygen vacancies around the Ce-ions is the main ingredient to change the Ce oxidation state, and hence the magnetic properties of Ce-doped SnO2NPs. The presented results pave the way for handling the magnetic properties of oxides through the control of the oxidation state of impurities. © The Royal Society of Chemistry 2021.Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica - Concyte