Effect of parameter calculation in direct estimation of the Lyapunov exponent in short time series

The literature about non-linear dynamics offers a few recommendations, which sometimes are divergent, about the criteria to be used in order to select the optimal calculus parameters in the estimation of Lyapunov exponents by direct methods. These few recommendations are circumscribed to the analysis of chaotic systems. We have found no recommendation for the estimation of λ starting from the time series of classic systems. The reason for this is the interest in distinguishing variability due to a chaotic behavior of determinist dynamic systems of variability caused by white noise or linear stochastic processes, and less in the identification of non-linear terms from the analysis of time series. In this study we have centered in the dependence of the Lyapunov exponent, obtained by means of direct estimation, of the initial distance and the time evolution. We have used generated series of chaotic systems and generated series of classic systems with varying complexity. To generate the series we have used the logistic map

Valorisation of glucose into biofuels and high value-added chemicals using zeolites as catalysts.

Hexose sugars can be valorised under acidic conditions to produce the platform chemical 5-hydroxymethylfurfural (HMF), which can be transformed in a broad spectrum of chemicals with applications as biofuels or monomers for polymers [1]. 5-ethoxymethylfurfural (EMF) is one of the derivatives of HMF useful as biofuel or fuel additive, produced usually from the etherification of HMF with ethanol. However, the high price of HMF is an important drawback for its use as feedstock for the production of EMF, which, together with the low yields and selectivity that are often attained by treating biomass or biomass derived compounds, are limiting its industrial application. In this work, several zeolites with different morphologies and chemical compositions have been employed as acid catalysts for the etherification reaction of HMF and ethanol to produce EMF, as well as the direct conversion of glucose into EMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Si-Al nanospheres for the valorization of galactose and agarose into 5-hydroxymethylfurfural.

5-hydroxymethylfurfural (HMF) is a compound that has gained attention to potentially substitute fossil resources in areas such as the polymer industry or the production of energy vectors. HMF is produced from the acid treatment of hexoses, such as glucose or galactose. In this sense, algae biomass has gained interest as it can be grown in both, sweet and salt water and their growth rate and CO2 fixation are several times higher than those of terrestrial plants. Red algae, which are rich in agarose, a galactose and 1,6-dehydrogalactose heteropolymer, can potentially be used as feedstock to produce HMF [1]. Hence, in this work, alumina supported nanospheres have been synthetised and employed as acid catalysts due to their high acidity and porosity that allows the selective conversion of these biomass derived compounds into valuable HMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influence of Lewis and Brønsted acid catalysts in the transformation of hexoses into 5-ethoxymethylfurfural

Several sulfonated polymers, which are typical Brønsted acid catalysts, have been employed in the production of two biofuels: 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) as main byproduct, and the catalytic results have been attributed to their different chemical and morphological properties. The Purolite CT275DR attained the best results from 5-hydroxymethylfurfural (HMF) with a 63% EMF yield after 16 h at 100 ◦C thanks to their more abundant superficial acid sites. Moreover, Purolite CT275DR was able to efficiently dehydrate and etherify fructose, with a total EMF plus EL yield of 65% after 24 h at 100 ◦C. When glucose or galactose were used as feedstock, alumina was utilized to provide Lewis acid sites, necessary for the transformation of aldoses in so- lution enabling a combined biofuel yield (EMF plus EL) of 40% from glucose after 24 h at 140 ◦C. With the study of the role of each catalyst, both Brønsted and Lewis acid catalysts (resin and alumina, respectively) were required to obtain considerable EMF yields from aldoses. The reutilization of the catalysts employed for 5 cat- alytic runs demonstrated that Purolite CT275DR suffers no appreciable loss of activity, but alumina showed progressive losses in activity in each cycle due to carbonaceous deposits and catalyst loss.Funding for open access charge: Universidad de Málaga / CBUA This research was funded by the Spanish Ministry of Innovation, Science and Universities (RTI2018-094918-B-C44), FEDER (European Union) funds (RTI2018-094918-B-C44 and UMA18-FEDERJA-171) and Malaga University. Authors thank to Universidad de M ́alaga/CBUA for funding for open access charge. C.G.S. acknowledges FEDER funds for her postdoctoral contract (UMA18-FEDERJA-171). B.T.O. acknowledges the Ministerio de Universidades for his predoctoral contract (FPU20/ 02334

Application of zeolites for the production of biofuels and furans from hexose sugars in ethanol.

The use of zeolites as catalysts in the transformation of glucose and 5-hydroxymethylfurfural (HMF) into 5-ethoxymethylfurfural (EMF) was evaluated. The behaviour of the catalysts could be explained by their morphology, composition, acid properties and chemical coordination of the active sites. The progress of the reaction was followed by High Performance Liquid Chromatography (HPLC) and 13C Nuclear Magnetic Resonance (NMR). Several intermediates were identified, and a reaction path is proposed. Different cosolvents were also employed in this study to enhance the selectivity towards different possible valuable compounds, and they were found to have a positive influence for the production of EMF and furfural.Funding for open access charge: Universidad de Málaga / CBU

Influence of marginal bone loss on peri-implantitis : systematic review of literature

The marginal bone of dental implants is subjected to slight load modifications over time, conditioning implant survival. Objective: Perform a systematic review of the literature analyzing the factors that contribute to marginal bone loss (MBL) and the subsequent development of peri-implantitis. Bibliographic research in the databases PubMed, Medline and Scopus between 2010 and 2018 was performed. The inclusion criteria were articles published in the last 10 years and that were in English or Spanish, that were carried out on humans, that were cohort studies, that included cases and controls or that used randomized clinical trials. Exclusion criteria removed articles that contained clinical cases, case series or systematic reviews. A total of 90 articles were analyzed that examined all the factors reported in the literature, such as idiosyncratic factors, toxic habits, systemic drugs and implant characteristics (diameter, length, type surface, implant connection, implant design and type of platform at the moment of the prosthetic load). Discussion: Patient characteristics and associated pathologies must be taken into account when assessing MBL. MBL in all dental implants can be considered independent of the type of prosthetic rehabilitation and the moment of load; this was emphasized. The MBL is smaller in dental implants with rough surfaces, switch platforms and infracrestal localization, as they are of multifactorial origin. All the reviewed articles maintain a common criterion regarding the concept and measurement of the MBL and highlighting the importance of radiodiagnosis for quantification. Longterm prospective studies with unified criteria are needed to reduce bias by identifying the most relevant factors in MBL

The effect of mechanochemistry on the preparation of heterogeneous catalysts: Reduction of furfural to obtain furfuryl alcohol.

In this context, mechanochemistry is receiving increasing attention for the synthesis of many chemical compounds in the solid state, considered by IUPAC as one of the 10 methodologies to change the world.Mechanochemistry is the part of chemistry that uses mechanical energy for the transformation of matter. This methodology will be used to study the effect caused by mechanochemistry in the precursor (Mg(OH)2), which is activated at 450 º C to obtain the active phase (MgO). This phase displays Lewis basic sites, which catalyzes the hydrogenation reaction of furfural to furfuryl alcohol. This catalyst will be used in the reduction of furfural to furfuryl alcohol (FFA) using isopropanol as hydrogen donor agent and dissolution medium.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Spreadsheet for the simulation of artificial neural networks (ANNs)

La utilización de Redes de Neuronas Artificiales (RNA) en problemas de predicción de series de tiempo, clasificación y reconocimiento de patrones ha aumentado considerablemente en los últimos años. Programas informáticos de matemáticas de propósito general tales como MATLAB, MATHCAD y aplicaciones estadísticas como SPSS y S-PLUS incorporan herramientas que permiten implementar RNAs. A esta oferta de software hay que añadir programas específicos como NeuralWare, EasyNN o Neuron. Desde un punto de vista educativo, el acceso de los estudiantes a estos programas puede ser difícil dado que no están pensadas como herramientas didácticas. Por otro lado, las hojas de cálculo como Excel y Gnumeric incorporan utilidades que permiten implementar RNAs y son de fácil acceso para los estudiantes. El objetivo de este trabajo es proporcionar un pequeño tutorial sobre la utilización de Excel para implementar una RNA que nos permita ajustar los valores de una serie de tiempo correspondiente a actividad cerebral alfa y que permita al alumno entender el funcionamiento de estos dispositivos de cálculo.In recent years, the use of Artificial Neural Networks or ANNs has increased considerably to solve prediction problems in time series, classification and recognition of patterns. General-purpose mathematical programs such as MATLAB, MATHCAD and mathematical and statistical programs such as SPSS and S-PLUS incorporate tools that allow the implementation of ANNs. In addition to these, specific programs such as NeuralWare, EasyNN, or Neuron, complete the software offer using ANNs. From an educational point of view, an aspect that concerns the authors of this work, student access to these programs can be expensive or, in sorne case, unadvisable given the few possibilities they provide as didactic instruments. These programs are usually easy to use but do not facilitate the understanding of the technique used. On the other hand, spreadsheets like Excel or Gnumeric incorporate tools that allow all of the necessary calculations to implement an ANN. These programs are user-friendly to the point that they are used by university laboratories, as well as psychology, economic science, and engineering students, to mention a few. This paper provides a small tutorial on the use of a spreadsheet, specifically Excel, to implement an ANN to adjust the values of a time series corresponding to cerebral alpha activity

Hidrocalumita: preparación por el método mecanoquímico y su aplicacion en la isomerización de glucosa a fructosa.

La fructosa es la llave para la formación de diversas moléculas plataformas tales como, furfural, 5-hidroximetilfurfural (HMF), acido levulinico, ácido fórmico y acido láctico. Actualmente en la industria se utilizan mayormente enzimas debido a los mejores resultados de selectividad y rendimiento del proceso de glucosa a fructosa. Es por este motivo que la búsqueda de catalizadores heterogéneos, que no necesiten condiciones de reacción tan singulares, hace que sea un amplio campo de investigación dentro de la catálisis.DEASYL SA Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Obtención de 5-hidroximetilfurfural a partir de agarosa y galactosa usando nanoesferas de sílica-alúmina.

En los últimos años, existe un gran interés en la obtención de moléculas plataforma mediante el uso de materias primas renovables. El 5-hidroximetilfurfural (HMF), una de estas moléculas plataforma, es un compuesto valioso para la producción de monómeros para polímeros y vectores energéticos y se obtiene de la deshidratación de hexosas en medio ácido. Las algas son una fuente de biomasa rica en carbohidratos que crecen, tanto en aguas dulces como marinas, mucho más rápido que las plantas terrestres, y no necesitan tierras de cultivo fértiles y limitadas, por lo que no competirían con la industria alimentaria. Uno de los polisacáridos presentes en las algas es la agarosa, cuya hidrólisis produce galactosa, una hexosa que puede usarse como precursora de HMF en presencia de un catalizador ácido. En este trabajo se han sintetizado una serie de nanoesferas mesoporosas de óxidos de aluminio y silicio para valorizar los componentes presentes en las algas hacia HMF.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech