idUS. Depósito de Investigación Universidad de Sevilla
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Multifunctional sustainable carbon catalyst for glucose to fructose isomerization reaction
No full textTwo series of functionalized activated carbons have been prepared and used for the glucose to fructose isomerization reaction. Alkali earth chlorides and alkali halides have been chosen for the functionalization with the final goal to study the effect of cation and anion variation on isomerization activity. A part of the samples has been subjected to an activation procedure giving rise to the formation of new active sites of a distinct type and composition. The active site nature and density greatly influenced the reaction mechanism, giving rise to combined pathways catalyst with increased activity and fructose selectivity. The functionalization with MgCl2 resulted in a very stable and performant catalyst with an optimal fructose yield of 33% at 140 °C in only 20 min reaction time and during four cycles of reutilization
Monitoring of volatile fatty acids during anaerobic digestion of olive pomace by means of a hand held near infrared spectrometer
No full textThe accumulation of volatile fatty acids (VFAs) over anaerobic digestion (AD) leads to malfunctioning of industrial reactors, hence decreasing biogas production. Real-time monitoring of VFAs is a challenge due to the complexity and high cost of current methods for their quantification. For this reason, this research evaluated the application of near infrared (NIR) spectroscopy to quantify volatile fatty acids as a tool for AD reactors monitoring. To do that, 129 samples from various AD reactors fed with olive oil pomace were taken and their NIR spectra were acquired with a hand-held spectrometer. After performing grid search, three spectral variable selection methods, namely competitive adaptive reweighted sampling, uninformative variable elimination (UVE) and successive projections algorithm, were assayed before developing PLRS models to correlate the NIR light transmittance through the samples at the wavelengths selected by those methods with their VFAs concentrations. UVE led to the best performance for all the VFAs assayed. Thus, R2 of validation of UVE-PLSR models for acetic, propionic, butyric, valeric and total VFAs were 0.895, 0.622, 0.866, 0.898 and 0.871, respectively. The predictive model for total VFAs achieved the highest accuracy (RMSEV = 539.5 mg/L), explained by the correlation between the light absorption at the wavelengths selected by UVE and the chemical characteristics of VFAs. All in all, the prediction errors achieved suggest that a portable near infrared spectrometer can be used for monitoring VFAs in AD processes.Ministry of Economy, Industry and Competitiveness PID2022-137299OB-100 and PID2020-116698RB-10
Growing up in the face of adversity: narratives of graduates with invisible disabilities from Italian and Spanish universities
No full textThis article explores, through the narratives of graduates with disabilities from Italy and Spain, the meaning of having a disability, how the perception of disability evolves during university studies and the strengths acquired as a consequence of disability. Thirty graduates with invisible disabilities from 17 Italian and Spanish universities were interviewed and the data were analysed with an inductive category and code system. The results show that disability is largely associated with an obstacle, although this perception is not static, but evolves positively throughout the university experience. Moreover, for the graduates, once the difficulties were overcome, disability enriched their lives, bringing new strengths, such as sensitivity, empathy, perseverance, resilience and self-determination. This study concludes that, in order to appreciate these strengths and capacities, it would be key to naturalise diversity, forget about labels, and remember that a person is not a diagnosi
Effectiveness of e-learning in higher education
No full textNowadays, the knowledge society demands to be prepared in the use of technology,
educational institutions cannot remain on the side-lines of this trend and are adapting their
curricula to cope with these demands. The present study explored the results of recent
research on the effectiveness of the use of e-learning in higher education, to provide a
clear synthesis on the state of research, gaps, and trends in the use of e-Learning in the
teaching-learning process at the university stage. For this purpose, a systematic literature
review (SLR) method is used. Out of 238 initial articles, 19 were selected for study
(published between 2012 and 2022). Among the results obtained, we highlight that does-
learning does not necessarily lead to better learning results but requires the involvement
of the entire educational community to obtain a positive effect. Thus, the success of this
educational model depends on how it is implemented by teacher
Influence of carbon nanotubes on the antimicrobial character of the β-lactam antibiotics Cefepime and Meropenem
No full textThe overuse of antibiotics over decades has led to a multi-resistance of bacteria that today poses a serious threat to human health. β-lactam antibiotics are one of the most prescribed drugs against bacterial infectious diseases, which has conducted to increased resistance. The short half-life of these drugs results in low bioavailability, which limits their clinical use and requires continuous administration by infusion. Encapsulation of these antibiotics in nanocarriers would improve their biopharmaceutical properties by protecting them. With this in mind, single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) were used here as nanocarriers for the antibiotics Meropenem and Cefepime.
The adsorption process of these antibiotics in the carbon nanotubes (CNTs) was optimized to obtain a high encapsulation efficiency. The complexes CNT/drug prepared were characterized by dynamic light scattering and spectroscopic measurements. The growth of Escherichia coli and Staphylococcus aureus bacteria was analyzed in the presence of the CNT/drug complexes to evaluate the pharmacological properties of the encapsulated antibiotics. Results showed lower minimum inhibitory concentration (MIC) values of the CNT/drug complexes compared to free drugs. This indicates the preservation of the pharmacological properties of the encapsulated antibiotics. In addition, the stability of the encapsulated antibiotics was observed to last at least 24 h, which was a great improvement compared to the free drugs
Minimizing energy consumption in 802.15.4 IoT devices with multilevel xRPL (MxRPL)
No full textIoT devices using IEEE 802.15.4 radio links may offer adaptable transmit power. But, since transmit power determines coverage, the problem of choosing the optimal tx power for each node is intertwined with the routing problem.
We present a new cross-layer routing approach for reducing energy consumption in IEEE 802.15.4 IoT devices with adjustable radio power level termed multilevel cross-layer RPL (MxRPL). In our scheme, each node sets its tx power level according to the RPL parent chosen in the path with the lowest additive product of ETX and nodes’ tx power. We also propose a new probing mechanism that maintains fresh link statistics for each neighbor and power level restraining the associated control messages. We have implemented our approach in Cooja’s Z1 mote and simulated a network with 15 nodes in areas of different size. The results show that MxRPL achieves energy savings in the radio of up to 34% in reception and 20% in transmission compared to a simpler cross-layer binary approach previously published by the authors (i.e., each node chooses either its maximum or minimum tx power level). Energy savings are even greater compared to default RPL (up to 40% in reception and 26% in transmission). This is mostly attributable to the generation of less control messages and a more efficient use of tx power. Our scheme exhibits better results in medium and large size scenarios (e.g.,
25 m 25 m, 42 m2 /node), whereas a simpler binary approach is slightly more advantageous in small and dense scenarios
Collision-free path planning for multiple robots using efficient turn-angle assignment
No full textThe ability to avoid collisions with moving robots is critical in many applications. Moreover, if the robots have limited battery life, the goal is not only to avoid collisions but also to design efficient trajectories in terms of energy consumption and total mission time. This paper proposes a novel strategy for assigning turn angles for collision-free path planning in scenarios where a small team of robots cooperate in a certain mission. The algorithm allows each robot to reach a predetermined destination safely. It establishes consecutive, short time intervals, and at each interval, possible conflicts are solved centrally in an optimal manner. This is done by keeping constant speeds but generating a discrete set of possible directions for each robot, and solving efficiently the turn-angle allocation for a collision-free path that minimizes the path deviation from the shortest one. Due to the discretization, the final paths are not optimal, but the system can react to possible failures during execution, as conflicts are resolved at each time interval. Computational results and Software-In-The-Loop simulations are presented in order to evaluate the proposed algorithm. A comparison with a state-of-the-art approach shows that our algorithm is more energy-efficient and achieves lower mission completion time
Enhancing digital reading comprehension through feedback messages: A large and long-term dynamic approach with secondary school students
No full textMany high school students struggle to efficiently read complex digital documents that require different self-regulating processes, such as identifying main ideas or integrating multiple documents. To foster these processes, we designed and tested a long-term dynamic approach in which 700 students from grades 7 to 10 answered adjunct comprehension questions and received immediate feedback either about the performance (corrective) or about different processes and strategies to answer the questions (elaborated). Surprisingly, the effect of feedback on comprehension scores varied across samples. Elaborated feedback had a positive impact on 7th–8th grade students' self-regulation and comprehension scores, whereas Corrective Feedback yielded greater improvements in these domains for 9th–10th grade students. The effects were partially mediated by students' reviewing time in both samples. We discuss the need to adapt dynamic assessment interventions to students' educational level
Backstepping for partial differential equations: A survey
No full textThis is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).Systems modeled by partial differential equations (PDEs) are at least as ubiquitous as those by nature finite-dimensional and modeled by ordinary differential equations (ODEs). And yet, systematic and readily usable methodologies, for such a significant portion of real systems, have been historically scarce. Around the year 2000, the backstepping approach to PDE control began to offer not only a less abstract alternative to PDE control techniques replicating optimal and spectrum assignment techniques of the 1960s, but also enabled the methodologies of adaptive and nonlinear control, matured in the 1980s and 1990s, to be extended from ODEs to PDEs, allowing feedback synthesis for systems that are uncertain, nonlinear, and infinite-dimensional. The PDE backstepping literature has since grown to hundreds of papers and nearly a dozen books. This survey aims to facilitate the entry into this thriving area of overwhelming size and topical diversity. Designs of controllers and observers, for parabolic, hyperbolic, and other classes of PDEs, in one or more dimensions, with nonlinear, adaptive, sampled-data, and event-triggered extensions, are covered in the survey. The lifeblood of control are technology and physics. The survey places a particular emphasis on applications that have motivated the development of the theory and which have benefited from the theory and designs: flows, flexible structures, materials, thermal and chemically reacting dynamics, energy (from oil drilling to batteries and magnetic confinement fusion), and vehicles
La Capilla Palatina de los Duques de Medina Sidonia y la Iglesia Mayor de Sanlúcar de Barrameda: historia de una dualidad y de una hibridación
No full textBajo el título “La Capilla Palatina de los Duques de Medina Sidonia y la Iglesia Mayor de Sanlúcar de Barrameda: historia de una dualidad y de una hibridación”, esta tesis doctoral despliega un amplio estudio histórico-artístico que indaga en cada una de esas dos fundaciones religiosas: la primera creada en 1473 en tiempos del III Duque de Medina Sidonia y la segunda construida en la década de 1440, en tiempos del I Duque.
La Capilla Ducal estaba situada en su Palacio de Sanlúcar, que era paredaño y estaba comunicado con la Iglesia Mayor del lugar a través de una Capilla-Tribuna. Se trataba de un gran balcón de unos 35 m2, al que se accedía desde el Palacio Ducal, adyacente al Templo. En aquella gran Tribuna -actualmente reducida a un pequeño balconcillo rococó-, se había instalado en el siglo XVI la parte esencial de la Capilla Palatina de los Guzmanes, que era el Altar del Crucifijo.
La presencia de la Capilla-Tribuna Ducal en el interior de la Iglesia Mayor de Sanlúcar, marcó profundamente su carácter, confiriéndole una gran singularidad. De este modo, en esta tesis se pone de relieve la imbricación que existió entre los espacios arquitectónicos de ambas fundaciones, así como la constante hibridación que históricamente se dio, tanto en sus usos litúrgicos como en sus funciones protocolarias y representativas.
Por ello, el estudio de ambas fundaciones religiosas se aborda aunando una doble perspectiva. Por un lado, considerando su propia dinámica -como fundaciones independientes-, y por otro haciendo hincapié en el constante patrocinio que la Casa Ducal de Medina Sidonia ejerció sobre la Iglesia Mayor de Sanlúcar, como prolongación natural de su Capilla Palatina. Como resultado, tenemos un estudio monográfico y diacrónico, que -además de aportar interesantes novedades histórico-artísticas-, podrá servir de modelo para otros similares, así como para la realización de futuros estudios comparativos, panorámicos y sincrónicos, sobre casos afines.
Desde el punto de vista formal, la obra está dividida en dos partes: la primera dedicada a la Capilla Palatina y la segunda a la Iglesia Mayor, presentando ambas el interés de abordar todo tipo de aspectos históricos, genealógicos, heráldicos, arquitectónicos, escultóricos, pictóricos, suntuarios y litúrgicos. El contenido de las dos partes se desarrolla en seis capítulos, todo ello precedido de un prólogo, una breve introducción y rematado con las conclusiones, redactadas a modo de compendio de aportaciones