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Role of cerium as a chemical vector for the design of new generation of ammonia synthesis catalysts
Full text linkThe industrial production of ammonia has been carried out by the Haber−Bosch
process for more than a century. However, a small-scale decentralized process is on high
demand, either for the use of ammonia as raw material in fertilizers industry or for its
growing interest as an energy vector for hydrogen storage. Particularly, the rising interest
of green ammonia (i.e., ammonia produced from renewables), has motivated a massive
research effort during the last two decades concerning new materials which lead to
circumvent the main handicap of the iron-based catalysts used in the Haber−Bosch
process: the current requirements of high temperatures and pressures that hinder the
coupling of ammonia reaction systems with renewable resources (mainly, water
electrolysis).
As discussed in the Chapter 1 from the Section II of this document, there is a
wide variety of materials suitable for boosting the traditional ammonia synthesis process,
thus leading to a successful operation at mild conditions. However, most of these
catalysts are on an incipient research state or present some drawbacks (e.g., complex
synthesis methods) which hinder their scalability. Thus, the search of more suitable,
attainable and stable catalysts is required for an effective transition towards a green
ammonia thermocatalytic synthesis scenario.
This doctoral Thesis is focused on the role of cerium (Ce) as a support for 3rd
generation ammonia synthesis materials, since its versatile properties allow this metal to
be a chemical platform for the design of efficient catalysts.
In the Chapter 1 of this Thesis, a review of the state-of-the-art is done, in which
the historical evolution of the most relevant 1st, 2nd and 3rd generation catalysts for
ammonia synthesis is presented. Furthermore, the fundamentals of this reaction are
unveiled with a particular focus on the metal-support interactions. The results from this
work led to the rational design of the catalysts presented in the following Chapters.
In the Chapter 2, the experimental results of the activity of CeNix alloys are
shown. This work, carried out in the MDX research Center for Element Strategy,
International Research Frontiers Initiative, Tokyo Institute of Technology, Japan,
highlighted the versatility of cerium by the good performance of the CeNi2 alloy, whose
fundamental key relies on the formation of a CeN surface layer over the original alloy,
acting as a second active center for the N2 dissociation and activation steps. Despite the
use of a non-noble metal like Ni, an activation energy as low as 55.3 kJ mol-1 was
achieved for CeNi2 bulk particles. In the Chapter 3, an experimental work of catalysts made of Ru/CeO2 and
Ru/CeO2-Al2O3 is presented. It was demonstrated that a very simple impregnationcalcination method led to the synthesis of a high surface cerium oxide support for
Ruthenium (Ru), creating a catalyst with low crystallinity and good electronic promotion
between metal and support, derived from the formation of surface oxygen vacancies,
typical from the reduction of cerium oxide (Ce4
+→Ce3
+). Further enhancement in the kinetic
mechanism can be found by the structural promotion of alumina. Activation energies as
low as 44.8 kJ mol-1 were obtained.
In the Chapter 4, the activity of Ru/CeO2-La2O3 catalysts is shown. In this case,
it was demonstrated that the activity of the original Ru/CeO2 catalyst can be enhanced by
the addition of La to the oxide lattice, since the crystal structure of ceria can be disrupted
by the formation of Ce-La solid solutions. As a result, there is a decrease in the crystallinity
of the oxydes and a higher number of structural defects is obtained. Thus, it was observed
that a superior generation of surface oxygen defects boosts the electron promotion of the
support towards the metal. The optimum catalyst was made of a 50% of Ce in molar
bases and its apparent activation energy was as low as 34.1 kJ mol-1.
The results presented in the present Thesis demonstrate that cerium can be a
key element for the design of catalysts for green ammonia thermocatalytic synthesis,
either in the form of cerium nitride in metallic alloy complexes with Ni or in the form of
ceria as a support for Ru. Furthermore, the performance of the latter can be further
enhanced by structural promotion with Al2O3 or by functional promotion by enhanced
formation of oxygen vacancies using La2O3, which resulted in a better electron transfer
towards Ru.
Certainly, the versatility of cerium and its wide margin to design better performing
catalysts can play a key role in the transition of ammonia synthesis towards the industrial
application as both green hydrogen storage energy carrier and raw material for
decentralized small plants of green fertilizers.En abierto se puede consultar la parte no embargada de la Tesis Doctoral
Enseñar y elaborar hoy una Teología católica. Breve reflexión desde la Teología Fundamental
Full text linkEn las últimas décadas, la sociedad occidental se ha caracterizado por un creciente avance de la secularización, lo cual significa que la religión juega en nuestros días un papel cada vez menos destacado. Un proceso que no solo afecta a sociedades y cultura, sino que también se ha instalado en las conciencias humanas, que interpretan el mundo y sus vidas sin acogerse a ideas religiosas. El objetivo de este breve documento es el de reflexionar acerca de cómo enseñar y elaborar una Teología católica en un contexto en el que esta es ignorada o, en el mejor de los casos, relegada a espacios marginales
Space-time mesh adaptation for the VMS-Smagorinsky modeling of high Reynolds number flows
Full text linkTraditional methods, such as Reynolds-Averaged Navier-Stokes (RANS) equations and Large Eddy Simulations (LES), provide consolidated tools for the numerical approximation of high Reynolds number flows in a wide range of applications - from green energy to industrial design. In general, RANS modeling is practical when the main interest is the time-averaged flow behavior. LES equations offer detailed insights into flow dynamics and a more accurate solution, but the high computational demand necessitates innovative strategies to reduce costs while maintaining precision. In this study, we enhance the Variational MultiScale (VMS)-Smagorinsky LES model by relying on an adaptive discretization strategy in both space and time, driven by a recovery-based a posteriori error analysis. We assess the effectiveness of the approach in capturing flow characteristics across a wide range of Reynolds numbers through benchmark tests
Una reflexión interdisciplinar abierta al futuro
No full textEn este artículo trataremos de presentar las claves del proyecto interdisdiplinar de Teilhard como fuente de inspiración para un pensamiento que se abra al futuro en clave de esperanza. Teilhard situó en la agenda intelectual debates muy relevantes sobre la realidad, y suscitó grandes cuestiones que no debemos soslayar. Hombre de ciencia y un hombre de fe, intentó reconciliar el Cristianismo y el mundo que nos desvelaba la ciencia. En su cosmovisión la ciencia, la teología y la filosofía establecen un diálogo fructífero en la búsqueda de la verdad que permita contemplar el significado profundo del cosmos
Calidad visual y sintomatología tras la implantación de una lente intraocular no difractiva de profundidad de foco extendida
No full textBackground/Objectives: This study aimed to evaluate the visual quality and symptomatol
ogy of a non-diffractive extended depth-of-focus (EDoF) intraocular lens (IOL), the Elon
877PEY (Medicontur, Zsámbék, Hungary), three months after implantation. Methods: A
cross-sectional case series study was conducted, with measurements taken three months post-implantation of the Elon IOL. A total of 56 implanted eyes from 28 patients (mean
age: 64.5 ± 9.5 years) were included in the statistical analysis. The variables analyzed
to assess the effectiveness of the Elon IOL included high-contrast visual acuity, contrast
sensitivity, the defocus curve, and visual symptoms. Results: Three months after implanta
tion, the mean residual sphere was 0.00 ± 0.33 D, while the mean residual cylinder was
−0.25 ± 0.41 D. Without correction, patients achieved monocular decimal visual acuity
values of 0.94 ± 0.26 for distance, 0.79 ± 0.17 for intermediate, and 0.58 ± 0.15 for near
vision. The mean uncorrected contrast sensitivity was 1.61 ± 0.15 log. The defocus curve
showed visual acuity exceeding 0.80 decimal (0.10 logMAR) over a 2.00 D range and above
0.63 decimal (0.20 logMAR) over a 2.50 D range. The most frequently reported symp
toms, with mild severity and bothersomeness, were glare, starbursts, halos, and focusing
difficulties. Conclusions: Patients implanted with the Elon IOL achieved satisfactory
visual quality at all distances, comparable to outcomes reported for other EDoF IOLs in the
scientific literature.Antecedentes/Objetivos : Este estudio tuvo como objetivo evaluar la calidad visual y la sintomatología de una lente intraocular (LIO) no difractiva de profundidad de foco extendida (EDoF), la Elon 877PEY (Medicontur, Zsámbék, Hungría), tres meses después de su implantación. Métodos : Se realizó un estudio transversal de serie de casos, con mediciones tomadas tres meses después de la implantación de la LIO Elon. Se incluyeron en el análisis estadístico un total de 56 ojos implantados de 28 pacientes (edad media: 64,5 ± 9,5 años). Las variables analizadas para evaluar la eficacia de la LIO Elon incluyeron la agudeza visual con alto contraste, la sensibilidad al contraste, la curva de desenfoque y los síntomas visuales. Resultados : Tres meses después del implante, la esfera residual media fue de 0,00 ± 0,33 D, mientras que el cilindro residual medio fue de −0,25 ± 0,41 D. Sin corrección, los pacientes alcanzaron valores de agudeza visual monocular decimal de 0,94 ± 0,26 para visión lejana, 0,79 ± 0,17 para visión intermedia y 0,58 ± 0,15 para visión cercana. La sensibilidad al contraste media sin corrección fue de 1,61 ± 0,15 log. La curva de desenfoque mostró una agudeza visual superior a 0,80 decimal (0,10 logMAR) en un rango de 2,00 D y superior a 0,63 decimal (0,20 logMAR) en un rango de 2,50 D. Los síntomas más frecuentes, de intensidad y molestia leves, fueron deslumbramiento, halos, destellos y dificultades de enfoque. Conclusiones : Los pacientes a los que se les implantó la LIO Elon lograron una calidad visual satisfactoria a todas las distancias, comparable a los resultados reportados para otras LIO EDoF en la literatura científica
Amistad social en el Papa Francisco
No full textLos Tras una sucinta aproximación a todo el pensamiento social de papa Francisco, el artículo se detiene en la encíclica sobre la fraternidad y la mistad social, Fratelli tutti (2020). Situada en su contexto, se comprende que la encíclica no contribuye tanto a la innovación, como hizo papa Francisco en Laudato si’ (2015), cuanto a subraya algunos elementos nucleares de la enseñanza social cristiana más relevantes en ese tiempo
Impact of Teleworking on Work-Related and Home-Related Stress at During the First Global Lockdown–The International COVISTRESS Study
No full textBackground: The initial lockdown during the pandemic of COVID-19 led to adjustments in working conditions, including extensive use of telecommuting whenever possible, putatively influencing both work-related and home-related stress.
Objectives: Our aim was to measure the impact of teleworking on work-related and home-related during the COVID-19 pandemic.
Methods: The international study was conducted using an online questionnaire to collect demographic and stress-related data from individuals worldwide during the 2020 pandemic year. Work-related and home- related stress levels were evaluated using an uncalibrated visual analog scale, with a range from 0 (none) to 100 (maximum).
Results: A total of 13,537 individuals from 44 countries completed the survey between January and June 2020. A total of 7356 individuals were engaged in professional activities. Of these, 6639 continued to work, of which 2573 carried on as usual and 4066 teleworked. The teleworkers demonstrated a considerably (p 80) was multiplied by 1.76 in women (1.54 to 2.01; p 80), and by 1.46 (1.22 to 1.76; p < 0.001) for those from continents outside Europe. Home-related stress is also a risk factor for work-related stress, and vice versa. Sociodemographic risk factors for higher levels of home-related stress were age < 50 years old, women, working < 50 h per week, continents outside Europe, and not teleworking were no longer risk factors.
Conclusion: Telework emerged as a viable option during the initial phase of the global pandemic. This mode of work was associated with lower levels of work-related stress compared to workers who were required to work in a conventional manner.
In terms of home-related stress, telecommuters experienced more stress than those who continued to work as usual
Application and assessment of model-based leak localization methods in an irrigation network
No full textThe availability of water resources in agriculture is under significant pressure due to climate change and global warming. In some regions, such as the south of Spain, rainfall has become increasingly scarce and concentrated over shorter periods, reducing the available water allocations and forcing the maximization of the irrigation system's efficiency. This situation highlights the importance of leaks within irrigation networks, which exacerbate the issue by decreasing the amount of water available for crops. These leaks not only represent a loss of water but also lead to increased operational costs due to the energy consumption required to maintain the network under pressure and in operation. Detecting and locating leaks is particularly challenging in buried irrigation networks, where root systems and depth complicate interventions, or in highly permeable or rocky soils, where the water loss caused by the leak can quickly move underground.
In this context, there is a pressing need to adapt and improve current leak detection techniques, which have traditionally been designed for water distribution networks (WDN), to the unique characteristics of irrigation systems. Unlike standard mesh WDN, irrigation networks exhibit a hierarchical, tree-like structure, with branches feeding drip lines, and with pressure regulating valves to control downstream pressure.
This work addresses the application of model-based methods designed for WDN for leak localization in irrigation networks. The evaluated methodologies rely on sensitivity matrices for leak management, considering pressure or flow variables as tools to determine measurement nodes. These include techniques such as binarization, vector angle, correlation comparison, Euclidean distance, and least squares; linear programming problem-solving; and the residual projection strategy, which monitors virtual leak flow values based on a dual model. These methods are analyzed against various magnitudes and interference sources, including additive and multiplicative noise, leak size, sensor placement, and more. Hydraulic simulations are performed on standardized WDN widely tested in the literature, such as Hanoi, Net3, and Quebra, as well as on a real irrigation network spanning 125 hectares of citrus orchards located in southwestern Spain. This work establishes an initial analysis and assessment of the state-of-the-art leak detection methods in a real irrigation network, highlighting the need for specific solutions for this type of infrastructure