Artículos (Física de la Materia Condensada)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10869

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What preset time schedule will it be? Rethinking daylight saving time
(Sage Journals, 2025-03-26) Martín Olalla, José María; Jorge Mira; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. FQM130: Propiedades Térmicas y Dieléctricas de Solidos
We discuss the foundations of the seasonal clock policy in view of a recent review article.
Assessing the best hour to start the day: an appraisal of seasonal Daylight Saving Time
(The Royal Society, 2025-03-19) Martín Olalla, José María; Mira, Jorge; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. FQM130: Propiedades Térmicas y Dieléctricas de Solidos
We provide an evidence-based position on the seasonal regulation of clocks (Daylight Saving Time, DST) that challenges position papers by sleep associations against the practice. We review the acute, short-term impact and the chronic, long-term impact of DST in the context of the changing ambient light conditions that characterize seasons at Extratropical latitudes. We highlight the association between DST, human physiology (photoreceptive mechanisms), and human daily life. We offer a perspective on the possible scenarios should clock regulations be abandoned.
Trapping of Gas Bubbles in Water at a Finite Distance below a Water-Solid Interface
(American Chemical Society, 2019-03-01) Esteso Carrizo, Victoria; Carretero-Palacios, S.; Thiyam, P.; Míguez, H.; Parsons, D. F.; Brevik, I.; Boström, M.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Research Council. Norway; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España
Gas bubbles in a water-filled cavity move upward because of buoyancy. Near the roof, additional forces come into play, such as Lifshitz, double layer, and hydrodynamic forces. Below uncharged metallic surfaces, repulsive Lifshitz forces combined with buoyancy forces provide a way to trap micrometer-sized bubbles. We demonstrate how bubbles of this size can be stably trapped at experimentally accessible distances, the distances being tunable with the surface material. By contrast, large bubbles (≥100 μm) are usually pushed toward the roof by buoyancy forces and adhere to the surface. Gas bubbles with radii ranging from 1 to 10 μm can be trapped at equilibrium distances from 190 to 35 nm. As a model for rock, sand grains, and biosurfaces, we consider dielectric materials such as silica and polystyrene, whereas aluminium, gold, and silver are the examples of metal surfaces. Finally, we demonstrate that the presence of surface charges further strengthens the trapping by inducing ion adsorption forces.
Natural abundance 17 O MAS NMR and DFT simulations: New insights into the atomic structure of designed micas
(Elsevier, 2019-08) Pavón González, Esperanza; Osuna, Francisco J.; Alba Carranza, María Dolores; Delevoye, Laurent; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Université de Lille; Junta de Andalucía; Agencia Estatal de Investigación. España
Combining 17 O Magic-Angle Spinning (MAS) NMR at natural abundance with DFT calculations is a promising methodology to shed light on the structure and disorder in tetrahedral sheets of designed micas with enhanced properties. Among brittle micas, synthetic mica is an important alternative to natural ones with a swelling sheet-like structure that results in many applications, by exploiting unique characteristics. Lowenstein's rule is one of the main chemical factor that determines the atomic structure of aluminosilicates and furthermore their properties. In the present article, 17 O MAS NMR spectroscopy is used to validate (or not) the agreement of the Lowenstein's rule with the distribution of Si and Al sites in the tetrahedral sheets of synthetic micas. 17 O MAS spectra of synthetic high-charged micas exhibit two regions of signals that revealed two distinguishable oxygen environments, namely Si-O-X (with X = Si, Al tet , Mg) and Al tet -O-Y (Y=Mg or Al tet ). DFT calculations were also conducted to obtain the 17 O chemical shift and other NMR features like the quadrupolar coupling constant, C Q , for all of the oxygen environments encountered in the two model structures, one respecting the Lowenstein's rule and the other involving Al tet -O-Al tet and Si-O-Si environments. Our DFT calculations support the 17 O assignment, by confirming that Al tet -O-3Mg and Al tet -O-Al tet oxygen environments show chemical shifts under 30 ppm and more important, with quadrupolar coupling constants of about 1 MHz, in line with the spectral observation. By quantifying the 17 O MAS NMR spectra at natural abundance, we demonstrate that one of the synthetic mica compositions does not meet the Lowenstein's rule.
Perspectives and Energy Applications of Magnetocaloric, Pyromagnetic, Electrocaloric, and Pyroelectric Materials
(Wiley, 2024-08-30) Klinar, K; Law, Jia Yan; Franco García, Victorino; Moya, X; Kitanovski, A; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Agencia de Investigación e Innovación de Eslovenia; Oficina de Investigación Científica de la Fuerza Aérea; European Union (UE)
This perspective provides an overview of the state of research and innovation in the areas of magnetocaloric and pyromagnetic materials, and electrocaloric and pyroelectric materials, including the overlapping sub-areas of multicaloric and multipyro materials that can operate simultaneously under the application of magnetic and electric fields. These materials are critically examined for their potential to revolutionize cooling, heating, and energy-harvesting applications. This perspective first summarizes the state-of-the-art advancements and highlights recent significant developments. Then, it is identified and discussed that the prevailing challenges hindering the widespread adoption of technologies based on these materials. In this context, after consulting with members of the caloric and pyro communities, a technology roadmap is outlined to guide research efforts in overcoming current barriers to applications, with the goal of achieving impactful results by 2040. This roadmap emphasizes the importance of focusing on under-researched materials, novel devices, and application spaces, paving the way for interdisciplinary efforts that can lead to significant reductions in carbon dioxide emissions.
Long-Term Impacts of Intense Pulsed Light Therapy on Ocular Surface Health and Tear Film Dynamics in Patients with Dry Eye Disease: Detailed Analysis and Observations Over a 1-Year Follow-Up Period
(Springer, 2024-08-16) Pac, Cristina Patricia; Munteanu, Mihnea; Sánchez González, José María; Rocha de Lossada, Carlos; Mercea, Nadina; Ferrari, Francis; Blidisel, Alexandru; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Cirugía
To evaluate the long‑term effects of intense pulsed light (IPL) therapy on patients with dry eye disease (DED) associated with mei‑ bomian gland dysfunction (MGD). Methods: A retrospective case series was per‑ formed with 110 participants undergoing IPL therapy. Assessments included the eye fitness test (EFT) to gauge subjective symptoms, along with objective measures using the Tearcheck ® device (ESW Vision, Houdan, France) noninva‑ sive first breakup time (NIFBUT), noninvasive average breakup time (NIABUT), central tear meniscus height (CTMH), thinnest tear menis‑ cus height (TTMH), and ocular surface inflam‑ matory risk evaluation (OSIE) assessed using the SCHWIND SIRIUS device (SCHWIND eye‑tech‑ solutions GmbH, Kleinostheim, Germany). Results: This study documented significant improvements in subjective and objective
Influence of the atmosphere on the formation of high-entropy oxides within the Co–Cu–Fe–Mg–Mn–Ni–O system via reactive flash sintering
(Elsevier, 2024-08-05) Manchón Gordon, Alejandro Fernando; Lobo-Llamas, C.; Molina Molina, Sandra; Perejón Pazo, Antonio; Sánchez-Jiménez, P. E.; Pérez-Maqueda, L. A.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Química Inorgánica; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
In this study, the feasibility of preparing quinary equimolar high-entropy oxides within the Co–Cu–Fe–Mg–Mn–Ni–O system was explored using the reactive flash sintering (RFS) technique. Various compositions were tested using this technique under atmosphere pressure, leading to the formation of two primary phases: rock-salt and spinel. Conversely, a new high-entropy oxide was produced as a single-phase material with the composition (Co0.2,Cu0.2,Mg0.2,Mn0.2,Ni0.2)O when RFS experiments were conducted in nitrogen atmosphere. The reducing conditions achieved in nitrogen enabled the incorporation of cations with oxidation states different from +2 into the rock-salt lattice, emphasizing the critical role of the processing atmosphere, whether inert or oxidizing, in the formation of high-entropy oxides. The electrical characterization of this material was obtained via impedance spectroscopy, exhibiting a homogeneous response attributed to electronic conduction with a temperature dependence characteristic of disordered systems.
A zirconia/tantalum biocermet: in vitro and in vivo evaluation for biomedical implant applications
(Royal Society of Chemistry, 2024-08-05) Smirnov, A. I.; Guitián, F; Ramírez Rico, Joaquín; Bartolomé, J. F.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Russian Science Foundation
A biocermet made of zirconia/20 vol% tantalum (3Y-TZP/Ta) is a new composite with exceptional capabilities due to a combination of properties that are rarely achieved in conventional materials (high strength and toughness, cyclic fatigue resistance and flaw tolerance, wear resistance, corrosion resistance, electrical conductivity, etc.). In this study, for the first time, the biomedical performance of a 3Y-TZP/Ta biocermet was evaluated in detail. Its in vitro biocompatibility was assessed using mesenchymal stem cell culture. The effectiveness of in vivo osteointegration of the biocermet was confirmed 6 months after implantation into the proximal tibiae of New Zealand white rabbits. In addition, the possibility of using magnetic resonance imaging (MRI) for medical analysis of the considered biocermet material was studied. The 3Y-TZP/Ta composite showed no injurious effect on cell morphology, extracellular matrix production or cell proliferation. Moreover, the implanted biocermet appeared to be capable of promoting bone growth without adverse reactions. On the other hand, this biocermet demonstrates artefact-free performance in MRI biomedical image analysis studies, making it more suitable for implant applications. These findings open up possibilities for a wide range of applications of these materials in orthopedics, dentistry and other areas such as replacement of hard tissues.
Self-reported preferences for seasonal daylight saving time meet fundamentals of human physiology: Correlations in the 2018 public consultation by the European Commission
(Taylor & Francis, 2025-01-27) Martín Olalla, José María; Mira, Jorge; Universidad de Sevilla. Departamento de Física de la Materia Condensada
We analyze the results to question 2 (individual preferences for cancelling or keeping the current clock regulations) from the 2018 Public Consultation on summertime arrangements (DST) conducted by the European Commission. We reveal correlations in the shares of population for cancelling the regulations and the winter sunrise time (SRW) [R2 = 0.177; p = 0.03; N = 25] and the onset of human activity [R2 = 0.677; p = 5 × 10−5; N = 17]. The results are in line with the rationale behind the regulations in the range of latitude 35 to 63: larger values of SRW (larger latitude) brought larger shares against the regulations; and earlier onset of human activity relative to SRW brought larger shares against the regulations. The shares for cancelling the regulation did not show correlations with time offset (position in time zone), thus challenging the current view within the circadian community.
Phase dependence of the thermal memory effect in polycrystalline ribbon and bulk Ni55Fe19Ga26 Heusler alloys
(Elsevier, 2025-02-09) Vidal Crespo, Antonio; Manchón-Gordón, Alejandro F.; Martín Olalla, José María; Romero Landa, Francisco Javier; Ipus Bados, Jhon Jairo; Gallardo Cruz, María del Carmen; Blázquez Gámez, Javier Sebastián; Conde Amiano, Clara Francisca; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Junta de Andalucía
The thermal memory effect, TME, has been studied in Ni55Fe19Ga26 shape memory alloys, fabricated as ribbons via melt-spinning and as pellets via arc-melting, to evaluate its dependence on the martensitic structure and the macrostructure of the samples. When the reverse martensitic transformation is interrupted, a kinetic delay in the subsequent complete transformation is only evident in the ribbon samples, where the 14M modulated structure is the dominant phase. In contrast, degradation of the modulated structure or the presence of the phase significantly reduces the observed TME. In such cases, the magnitude of the TME approaches the detection limits of commercial calorimeters, and only high-resolution calorimeter at very low heating rate (40 mK h−1) can show the effect. Following the kinetic arrest and subsequent cooling, the reverse martensitic transformation was completed at several heating rates to confirm the athermal nature of the phenomenon.
Efficacy assessment of liposome crosslinked hyaluronic acid and standard hyaluronic acid eye drops for dry eye disease management: a comparative study employing the ocular surface analyzer and subjective questionnaires
(Frontiers Media S.A., 2024-06-26) Sánchez González, José María; Hita Cantalejo, María Concepción de; González Rodríguez, María Luisa; Fernández-Trueba-Fagúndez, Ana; Ballesteros-Sánchez, Antonio; Martínez-Pérez, Clara; Caro-Díaz, Romina; Montiel Guzmán, Carla; González-Oyarce, María Fernanda; Sánchez González, María del Carmen; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica
Introduction: Dry eye disease (DED) is a prevalent condition causing ocular discomfort and visual disturbances, often managed with artificial tears. This study aimed to assess and compare the efficacy of eye drops containing Crosslinked Hyaluronic Acid (CHA) with liposomes and crocin and standard Hyaluronic Acid (HA) for DED management. Methods: A single-blind, longitudinal study was conducted on 24 participants (48 eyes), randomized to receive one of the two treatments. Ocular health measures, including the ocular surface disease index (OSDI) and the standard patient evaluation of eye dryness (SPEED) scores, were assessed at baseline and 6 weeks post-treatment using the Ocular Surface Analyzer. Results: CHA achieved a lipid layer thickness increase of 1.29 ± 1.08 Guillon pattern degree (p < 0.01), FNIBUT increase 0.64 ± 0.77 s (p < 0.01), MNIBUT increase1.28 ± 4.74 s (p = 0.19), OSDI decrease 11.72 ± 6.73 score points (p < 0.01) and SPEED decrease 1.16 ± 5.05 score points (p = 0.27). Significant reductions in the OSDI and SPEED scores post-treatment were observed with both treatments, indicating their effectiveness. Conclusion: CHA with liposomes exhibits superior efficacy compared to standard HA eye drops in the management of DED. These findings highlight the potential for personalized treatment strategies incorporating CHA, indicating a more effective approach to DED management. However, further research is required to validate these results and investigate the long-term effects, which may pave the way for a data-driven and optimized approach to managing DED.
Processability and Properties of Cubic-BaTiO 3/poly(vinylidene fluoride) Composites for Additivemanufacturing: From Powder Compoundingto 3D-printed Parts
(John Wiley & Sons, 2024) Moriche Tirado, Rocío; Donate, R.; Otero Pino, Andrea; Santiago Andrades, L.; Monzón, E.; Sayagués, M. J.; Monzón, M.; Paz, R.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
Poly(vinylidene fluoride) (PVDF) is a piezoelectric and thermoplastic material with great potential for additive manufacturing (AM) applications. Using barium titanate (BaTiO3) as filler, PVDF-based composite materials were developed, characterized, and processed by AM material extrusion (MEX). The morphological features and phase transformations occurring throughout the processing of BaTiO3-filled PVDF, from the compounding to the printed part, were analyzed. The morphology of the powder feedstock after dispersion in a high-energy ball mill changed from spheroidal to laminar and β-phase formation was favored. Microhardness gradually increased with the BaTiO3 content, obtaining an enhancement of ~60% for a content of 25 vol%, and supported the good dispersion of the filler. A ~48% increase of the dielectric permittivity was also achieved. After extrusion, filaments with a filler content of 15 vol% showed a more stable diameter, as well as higher crystallinity and surface roughness, compared with those with lower BaTiO3 contents. Material extrusion of filament and direct printing of pellets based on MEX were successfully used to obtain AM parts. Composite parts showed enhanced surface roughness, hydrophilicity, and flexural modulus (up to ~33% for the 7 vol% composite compared with the PVDF), thus leading to superior mechanical characteristics and potential biomedical applications. Highlights: Dry high-energy ball milling was a suitable greener dispersion approach. MEX processes were successfully used to obtain 3D-printed parts. The use of direct printing of pellets/powder improved the 3D printability. The surface roughness and hydrophilicity increased with the filler content. The permittivity and elastic modulus increased with the filler content.
Space colonization by branching trachea explains the morphospace of a simple respiratory organ
(Elsevier, 2020-06-01) Ruiz-Sobrino, A.; Martín-Blanco, C. A.; Navarro, T.; Almudí, I.; Masiero, G.; Jiménez-Caballero, M.; Buchwalter, D. B.; Funk, D. H.; Gattolliat, J. L.; Lemos Fernández, María del Carmen; Jiménez-Morales, Francisco de Paula; Casares, F.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; National Science Foundation (NSF). United States; European Union (UE); Agencia Estatal de Investigación. España
Branching morphogenesis helps increase the efficiency of gas and liquid transport in many animal organs. Studies in several model organisms have highlighted the molecular and cellular complexity behind branching morphogenesis. To understand this complexity, computational models have been developed with the goal of identifying the “major rules” that globally explain the branching patterns. These models also guide further experimental exploration of the biological processes that execute and maintain these rules. In this paper we introduce the tracheal gills of mayfly (Ephemeroptera) larvae as a model system to study the generation of branched respiratory patterns. First, we describe the gills of the mayfly Cloeon dipterum, and quantitatively characterize the geometry of its branching trachea. We next extend this characterization to those of related species to generate the morphospace of branching patterns. Then, we show how an algorithm based on the “space colonization” concept (SCA) can generate this branching morphospace via growth towards a hypothetical attractor molecule (M). SCA differs from other branch-generating algorithms in that the geometry generated depends to a great extent on its perception of the “external” space available for branching, uses few rules and, importantly, can be easily translated into a realistic “biological patterning algorithm”. We identified a gene in the C. dipterum genome (Cd-bnl) that is orthologous to the fibroblast growth factor branchless (bnl), which stimulates growth and branching of embryonic trachea in Drosophila. In C. dipterum, this gene is expressed in the gill margins and areas of finer tracheolar branching from thicker trachea. Thus, Cd-bnl may perform the function of M in our model. Finally, we discuss this general mechanism in the context of other branching pattern-generating algorithms.
Oscillatory behavior in a system of swarmalators with a short-range repulsive interaction
(American Physical Society, 2020-06-01) Jiménez-Morales, Francisco de Paula; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Economia, Industria y Competitividad (MINECO). España
One of the computational models proposed to study emerging phenomena in decentralized systems is the swarmalator model [Nat. Commun. 8, 1504 (2017)2041-172310.1038/s41467-017-01190-3], where only long-range interactions are considered. But in living systems many of the collective behaviors observed arise from the combined effect of long- and short-range interactions. In this work we present an extension to the swarmalator model which includes a Gaussian short-range repulsive term of the type 1σe-|x|2/σ along with the results of numerical simulations. Using several order parameters we can distinguish between static and dynamic aggregations and between synchronous and asynchronous states. We have found six long-term collective states, some of them not previously reported and the most remarkable one showing oscillatory collective behavior. The results obtained show a multiplicity of complex behaviors that extend the applicability of the swarmalator model.
A cellular automata model of a laser reproducing laser passive and active Q-Switching
(Elsevier, 2025-01) Jiménez-Morales, Francisco de Paula; Guisado Lizar, José Luis; Guerra, José Manuel; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Arquitectura y Tecnología de Computadores; Ministerio de Ciencia, Innovación y Universidades (MICINN). España
The Q-switching (QS) phenomenon in lasers refers to the production of high intensity pulses by means of a saturable absorber (passive method) or by modifying the reflectivity or losses of the intracavity optics or mirrors (active method). Theoretically, the QS is studied through the laser rate equations which are useful to predict, at least qualitatively and roughly, the fundamental aspects of laser dynamics. However, specific details such as the spatial distribution of the intensity of the laser emission escape the simplicity of the rate equations. In this work we present a two dimensional cellular automata model (CA) to study the QS phenomenology for both the passive and the active method. To simulate the passive method we consider a spatial distribution of cells whose physical properties emulate those of the saturable adsorbers. And for the active method we introduce a periodic modulation of the lifetime of the photons inside the cavity. We have done numerous numerical simulations that show that despite the simplicity of the evolution rules, the AC model is capable of obtaining the main dynamics of operation of the laser by modifying the system parameters such as the pumping probability and the properties of the absorber.
Effect of Exposure to Blue Light from Electronic Devices and the Mediterranean Diet on Macular Pigment
(MDPI, 2024) García Romera, Marta de la Concepción; Ponce García, Víctor; Torres Parejo, Úrsula; López Muñoz, Alfredo; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Objective: To explore the effect of time exposure to flat screen electronic devices with LED lighting and the Mediterranean diet on macular pigment optical density (MPOD). Methods: In this cross-sectional observational study, the MPOD was measured by heterochromatic flicker photometry in 164 eyes (47 of younger women aged 20–31 and 35 of older women aged 42–70). Exclusion criteria: evidence of macular degeneration and eyes with cataracts. Data on the use of electronic devices and Mediterranean diet adherence were collected through a survey. Nonparametric analysis of variance and independent sample t-tests were used to compare subjects. Results: Significant differences (p < 0.01) were found in total time of exposure to LEDs (hours per day) between both groups (9.31 ± 3.74 younger women vs. 6.33 ± 3.64 older women). The MPOD values for the younger and adult populations were significantly different: 0.38 ± 0.16 and 0.47 ± 0.15 (p < 0.01), respectively. When comparing both groups for the same time of exposure to LEDs, differences were obtained between MPOD values of both populations: For total exposures greater than 6 h per day, the MPOD values were lower in younger women than in adult ones (0.37 ± 0.14 vs. 0.50 ± 0.14, p < 0.01). On the other hand, a significantly higher adherence was found in the older women in comparison with the younger women (OW 9.23 ± 2.50 vs. YW 7.70 ± 2.08, p < 0.01), with higher MPOD values (OW (0.52 ± 0.14) vs. (YW (0.34 ± 0.18). Conclusions: Higher MPOD values are observed with decreasing exposure time to electronic devices with LED lighting screens and higher adherence to the Mediterranean diet.
Microhardness and wear behavior of nanodiamond-reinforced nanocomposites for dental applications
(Wiley, 2024-10-04) Moriche Tirado, Rocío; Chetwani, Bhanu; Artigas-Arnaudas, Joaquín; Sánchez, María; Campo, Mónica; Prolongo, Margarita G.; Rams, Joaquín; Prolongo, Silvia G.; Ureña, Alejandro; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Agencia Estatal de Investigación. España
In polymer-based dental composites, wear is a three-body wear system mainly abrasive, because of the food particles and wear products suspended in the oral cavity, which are transferred to the microcavities of the surface of the replacements. Due to this fact, the incorporation of nanodiamond as reinforcement in these polymer–matrix composites, which promotes the creation of a solid lubricant tribofilm surface could be advantageous. With the reinforcement of nanodiamonds, BisGMA/TEGDMA-based composites increase their microhardness by 95%–420%. A maximum hardness exceeding 65 HV is achieved with a reinforcement of 3.2 wt%. The specific wear rate of neat BisGMA/TEGDMA is near 10−4 mm3/Nm and the Archard's coefficient is 2.6 × 105. The incorporation of a content of 1.6 wt% ND is enough to cause a diminution of ~78% in the friction coefficient and a reduction of the specific wear rate and Archard's coefficient of ~50%. Nevertheless, the addition of relatively high contents reduces the effectiveness of photoinitiation and photocuring, which is related to the scattering and absorption of light radiation by ND. This causes a significant decline in elastic properties starting at 50 μm from the surface.
Fine-grained BCZT piezoelectric ceramics by combining high-energy mechanochemical synthesis and hot-press sintering
(Elsevier, 2024-12-05) Sayagués de Vega, María Jesús ; Otero Pino, Andrea; Santiago Andrades, Lucía; Poyato, R.; Monzón, M.; Paz, R.; Gotor Martínez, Francisco José; Moriche Tirado, Rocío; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Agencia Estatal de Investigación. España; European Union (UE)
Different stoichiometries of lead-free BaZr0.2Ti0.8O3–Ba0.7Ca0.3TiO3 (BCZT) prepared by mechanosynthesis and sintered by either conventional sintering (CS) or hot pressing (HP) techniques were studied to establish the dependence of piezoelectric and dielectric properties on sintering parameters and microstructure. All synthesized stoichiometries showed a pseudocubic perovskite phase with homogeneously distributed A- and B-cations in the structure. The BCZT retained the pseudocubic symmetry after sintering and an average grain size <1.8 µm was obtained in all cases. HP sintering hindered the secondary phase segregation observed in the CS ceramics and increased the relative density. Piezoelectric coefficients (d33) ranging from 5.1 to 21 pC/N and from 10.0 to 88.0 pC/N were obtained for CS and HP ceramics, respectively, despite the pseudocubic symmetry and the fine grain size. The higher d33 values for the HP ceramics are a consequence of the higher density, better chemical homogeneity and lower sintering temperature and time required for the mechanosynthesized BCZT powders with high sintering activity.
Seasonal Daylight Saving Time in UK: A long-standing, successful record with few reasons to change
(Wiley, 2024-11-29) Martín Olalla, José María; Mira, Jorge; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Prevalence of sleep disturbance among Chinese healthcare professionals increases Eastward—caution with position in time zone
(Elsevier, 2024-11-19) Martín Olalla, José María; Mira, Jorge; Universidad de Sevilla. Departamento de Física de la Materia Condensada
We analyze data of the prevalence of sleep disturbance among Chinese healthcare professionals and maintain that they increase Eastward, refining previous results. We suggest that position in time zone is a valid explanatory metric only after daily rhythms have been uniformed. On a more general note, this finding suggest that daylight saving time might help reduce sleep disturbance.

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