Obtaining Cellulose Nanocrystals from Olive Tree Pruning Waste and Evaluation of Their Influence as a Reinforcement on Biocomposites.

The objective of this work is to improve the mechanical properties of polylactic acid (PLA) by incorporating cellulose nanocrystals (CNC) previously obtained from a cellulose pulp extracted from olive tree pruning (OTP) waste. Composites were manufactured by melt processing and injection moulding to evaluate the effect of the introduction of CNC with conventional manufacturing methods. This OTP-cellulose pulp was subjected to a further purification process by bleaching, thus bringing the cellulose content up to 86.1%wt. This highly purified cellulose was hydrolysed with sulfuric acid to obtain CNCs with an average length of 267 nm and a degradation temperature of 300 °C. The CNCs obtained were used in different percentages (1, 3, and 5%wt.) as reinforcement in the manufacture of PLA-based composites. The effect of incorporating CNC into PLA matrix on the mechanical, water absorption, thermal, structural, and morphological properties was studied. Maximum tensile stress and Young's modulus improved by 87 and 58%, respectively, by incorporating 3 and 5%wt. CNC. Charpy impact strength increased by 21% with 3%wt. These results were attributed to the good dispersion of CNCs in the matrix, which was corroborated by SEM images. Crystallinity index, glass transition, and melting temperatures were maintained.

Effect of Olive Pit Reinforcement in Polylactic Acid Biocomposites on Environmental Degradation.

Polylactic acid (PLA) is a biomaterial widely used as an alternative to petroleum-based polymeric matrices in plastic components. PLA-based biocomposites reinforced with lignocellulosic waste are currently receiving special attention owing to their mechanical properties, low toxicity, recyclability, and biodegradability. The influence of the percentage of waste on their properties and resistance to degradation are some of the points of great relevance. Therefore, a series of PLA-based biocomposites containing different percentages of olive pits (5, 15, 25 and 40% wt.) were manufactured and characterized both (a) immediately after manufacture and (b) after one year of storage under environmental conditions. The results obtained were analyzed to evaluate the influence of the incorporation of olive pits on the resistance to degradation (measured through Carbonyl Indices, CI), mechanical properties (tensile, flexural and impact strength), structure (Fourier Transform Infrared Spectroscopy, FT-IR; and, X-ray Diffraction, XRD), morphology (Scanning Electron Microscopy, SEM) and water absorption capacity of the manufactured materials. PLA degradation, corroborated by Differential Scanning Calorimetry (DSC), FT-IR, and XRD, resulted in a decrease in tensile and flexural strengths and an increase in the tensile and flexural moduli. This trend was maintained for the biocomposites, confirming that reinforcement promoted the PLA degradation.

Manufacture and Characterization of Recycled Polypropylene and Olive Pits Biocomposites.

The present work studies the use of olive pit (OP) as a reinforcement in the manufacture of composites based on a post-consumer recycled polypropylene (rPP). In this way, it is feasible to provide added value from olive pits, a by-product resulting from the olive industry operations, while promoting the circular economy and reducing the use of fossil-based polymers. For this purpose, suitable samples were manufactured using 25 wt% and 40 wt% of OP. Additionally, the effect of incorporating additives was studied: (a) a process control additive (PA), and (b) a coupling agent of maleic anhydride grafted polypropylene (MAPP). The results showed an improvement in Young's and flexural modulus with the OP addition. The incorporation of PA did not present any significant improvement in the properties of the materials, nevertheless it facilitated the biocomposite manufacturing process. As for the coupling agent, it significantly improved the mechanical properties, achieving the best results with the addition of the two types of additives and 40 wt% of OP. Moreover, the thermal properties were maintained, and there was an increase in crystallinity in all composites compared to rPP. According to the results of the fracture surface analysis, the coupling agent improves reinforcement-polymer matrix cohesion.

Do the Lower Body Strength Assessment Tests in the Spanish Navy Really Measure What They Purport to Measure?

The main objective of this research was to analyse the efficacy of lower body strength assessment tests in the Armed Forces Physical Assessment System. Secondly, it was to determine what relationship exists between the physical evaluation system of the Spanish Armed forces and standardized evaluation protocols (Gold standard). A total of 905 students enrolled in the military/civil bachelor's degree (813 male and 92 female) participated in this study. The influence of the sex of the participants was studied through the student's t-test for independent data, and the degree of association between variables was defined by Pearson's correlation coefficient. The results present moderate correlations (r = 0.67, r = 0.66; p < 0.001) between the vertical jump test used by the Army and the power or elastic force tests commonly used in practice and in research. The results obtained reflect a moderate relationship between the gold standard tests and the tests used by the Army, which suggests that the tests currently used to assess lower body strength should be adapted to more objective measurement tools which would allow a better comparison between samples from different armed forces.

Advanced Photonic Thin Films for Solar Irradiation Tuneability Oriented to Greenhouse Applications.

The world population is growing by 1 billion people every 10 years. There will come a time when there will be more people to feed but less land to grow food. Greenhouses can be the solution to this problem because they provide the highest production yield per m2 and also use less water, provide food safety, and offer high quality. Photosynthetic active radiation (PAR) favors vegetable growth with a specific blue and red light ratio. Thus, increasing the amount of red light improves chlorophyll absorption and photosynthetic efficiency. In this article, we present a hybrid system that combines luminescent materials and photonic crystals for better management of the light reaching the greenhouse. The luminescent dyes considered herein are combined ensuring a Förster resonance energy transfer (FRET) nonradiative mechanism to enhance the absorption range. The designed photonic crystal maximizes reflections in the Near-Infrared (NIR) range, and therefore, thermal losses are minimized. Thus, by converting harmful or ineffective radiation for plant growth to the PAR region, we aim to demonstrate growth-condition enhancement for the different vegetables that have been used as a model.

Physical fitness in Spanish naval cadets. A four-year study.

BACKGROUND: Military physical readiness largely depends on soldiers maintaining their general health and physical fitness at a level which enables them to perform their requisite occupational duties in garrison and deployment environments. Understanding the physical fitness of naval cadets throughout its formative stages will help us define a training programme tailored to their needs. The objective of this study was to analyse the physical fitness of cadets enrolled in military training in the academic year 2018-2019 in the Military Naval Academy in Marín, Spain. MATERIALS AND METHODS: A longitudinal correlational-descriptive design was undertaken. 167 of the 292 students who participated in the global analysis participated in the pre and post (first and second semester) physical fitness tests (153 males and 14 females, mean age 21.9 ± 3.5) and were stratified into age groups. Anthropometric measurements and data from the Spanish army physical fitness assessment system (2 min push-ups, 1000 and 50 m races, vertical jump and 50 m swimming) were used. A descriptive, inferential, and correlational analysis was carried out and the level of significance set for the study was p ≤ 0.05. RESULTS: Inferential analysis between age group markers and over the total sample shows statistical differences for the total sample in the 1000 m and 50 m race (p < 0.001) and in vertical jump test (p < 0.010). There was significant statistical correlation between all five tests undertaken. CONCLUSIONS: The level of physical fitness of cadets at the Military Naval Academy in Marín, Spain appears to be acceptable when compared to other countries' military naval corps. Coherence between training and evaluation is extremely important, and a re-evaluation of stamina and strength training is probably advisable.

Synthesis and Characterisation of Acrylic Resin-Al Powder Composites Suitable for Additive Manufacturing.

Stereolithography is an additive manufacturing technology commonly used to build either prototypes or final parts. Nevertheless, the manufacture of structural parts has been ruled out owing to the poor mechanical properties of conventional UV-curable resins. Moreover, the inventory of available commercial resins is still limited and they exhibit low thermal and electrical conductivity values. In this work, some composite materials were designed using Al microparticles dispersed within an SLA commercial resin matrix. These composites overcame the difficulties caused by the light scattering effect during the photopolymerisation process in the SLA technology. Dispersion of the filler was characterised by means of SEM/EDX and AFM. The composites exhibited improved thermal and mechanical behaviour in comparison with the pristine resin. The simplicity of the synthesis method used to prepare the composites provides a convenient starting point to explore new ways of designing composites for SLA with improved mechanical and functional properties.

Development of Surface-Coated Polylactic Acid/Polyhydroxyalkanoate (PLA/PHA) Nanocomposites.

This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (<0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates.

Role of Alternative Fuels on Particulate Matter (PM) Characteristics and Influence of the Diesel Oxidation Catalyst.

The influence of a platinum:palladium (Pt:Pd)-based diesel oxidation catalyst (DOC) on the engine-out particulate matter (PM) emissions morphology and structure from the combustion of alternative fuels (including alcohol-diesel blends and rapeseed oil methyl ester (RME) biodiesel) was studied. PM size distribution was measured using a scanning mobility particulate spectrometer (SMPS), and the PM morphology and microstructure (including size distribution, fractal geometry, and number of primary particles) was obtained using high-resolution transmission electron microscopy (TEM). It is concluded that the DOC does not modify the size or the microstructural parameters of the primary particulates that make up the soot agglomerates. The PM reduction seen in the DOC is due to the trapping effect, and oxidation of the PM's volatile components. The DOC performance in reducing gaseous (e.g., carbon monoxide (CO) and unburnt hydrocarbons (HCs)) and PM emissions at low exhaust temperatures was improved from the combustion of alternative fuels due to the reduced level of engine-out pollutants.

Los conductores re-examinados: El transcurso del tiempo deteriora significativamente los conocimientos de los conductores / Re-examined drivers: Significant deterioration on knowledge of drivers over time

Dos mil cinco conductores, 1204 hombres y 801 mujeres, una muestra representativa de la población española de conductores, fueron nuevamente examinados utilizando un cuestionario que reproducía fielmente un examen de conducir realizado por la Dirección General de Tráfico (DGT). Las preguntas fueron clasificadas en "muy importantes", "importantes" y "poco importantes". El 96.5 % de los conductores, suspendió el examen. Los resultados eran tanto peores cuanto más tiempo había transcurrido desde la obtención del permiso de conducir. Esto era independiente de la importancia de las preguntas, de la mayor o menor frecuencia de conducción y afectaba por igual a hombres y mujeres. Las mujeres obtienen mejores puntuaciones en señalización mientras que los hombres son mejores en las preguntas de seguridad vial. Los resultados también demostraban que los conductores profesionales y los de mayor nivel educativo sufren un menor deterioro. Tales resultados nos llevan a considerar la relación que estos datos puedan tener en los niveles de accidentalidad y la conveniencia de establecer pautas para la actualización del conocimiento de los conductores. Finalmente, se discute la relevancia que el examen que se utiliza para obtener el permiso de conducir tiene como indicador o predictor de una futura conducción segura.

Two thousand and five drivers, 1204 men and 801 women, a representative sample of the Spanish drivers, were re-examined using a questionnaire that faithfully reproduced a driving test conducted by the Directorate General of Traffic (DGT). Items were classified as "very important", "important" and "unimportant." 96.5% of drivers did not pass the test. The results were much worse the more time had elapsed since obtaining the driving license. These results were independent of the importance of the items, the greater or lesser frequency of driving and applied equally to men and women. Women perform better signalling while men are better at questions of road safety. Results also showed that the loss of knowledge was lower in those drivers who had higher education training and professional drivers. The results lead us to consider the relationship that these data may have on levels of accidents and the desirability of establishing guidelines for updating the knowledge of the drivers. Finally, the relevance of the test used to obtain a driver's license as an indicator or predictor of safe driving is discussed.

Geometrical determination of the lacunarity of agglomerates with integer fractal dimension.

Different agglomerates composed by a variable number of spherical primary particles corresponding to extreme and intermediate values of fractal dimension (D(f)=1, D(f)=2 and D(f)=3) are analysed in this work. In each case, the moment of inertia, diameter of gyration and prefactor of the power-law relationship are determined as a function of the number of composing primary particles. The obtained results constitute the geometrical data base for the development of a method for the determination of the fractal dimension of individual agglomerates from their planar projections, although it is not the aim of this paper to describe the method itself. As a result of these calculations, the prefactor of the power-law relationship was shown not to be a constant parameter, but to tend asymptotically to a limit value with increasing number of primary particles. This limit value is closely related with the compactness of the initial geometrical arrangement in the agglomerate, this justifying the historical association of this parameter with the lacunarity of the agglomerate. A correlation for the determination of the prefactor as a function of the fractal dimension and the number of elementary structures is proposed and compared with other methods proposed in the literature.

A method to determine the fractal dimension of diesel soot agglomerates.

Soot agglomerates emitted by diesel engines are composed of primary particle forming irregular clusters. Such irregularity can be quantified by the fractal dimension, whose determination depends on certain parameters not unanimously established, such as the prefactor of the power law relationship. Mean values of the fractal dimension of large collections of agglomerates are usually determined in literature by least-square regression fittings to the power law relationship. In this paper, an iterative method to determine the fractal dimension of individual agglomerates is proposed instead, thus making possible a better discrimination of effects. Functions depending on the fractal dimension and the number of primary particles are proposed for the prefactor and for the overlapping parameter (a measure of the overlap that the primary particles provoke among themselves when projected). Therefore, extreme cases (agglomerates forming a compact sphere and an aligned chain of primary particles) were taken as boundary conditions, for which a geometrical analysis has been performed. The method has been adjusted by comparison with cluster-cluster aggregation models taken from literature, and has proved to have good sensitivity and low loss of information. Some examples are shown from transmission electron microscopy (TEM) images of agglomerates obtained with thermophoretic sampling from the exhaust gas of a diesel engine under different operating conditions.