Artículos (Física de la Materia Condensada)

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

Examinar

Mostrando 1 - 20 de 686

Pyroelectric Potassium Hydrogen Malate with Polarized Hydrogen Bond Chains and Aligned Dipole Moments
(American Institute of Physics, 2008) de Matos Gomes, E.; Belsley, M. S.; Criado Vega, Alberto; Rodrigues, V. H.; Costa, M. M.R.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Fundação para a Ciência e a Tecnologia. Portugal
A spontaneous polarization of 16 μC/ cm2 at room temperature has been found in the semiorganic crystal potassium hydrogen malate (KHC 4H4O5 · H2O). This high polarization results from a structural arrangement of oriented dipoles formed by the potassium cations and the COO- group from the malate anion, and long hydrogen bonded polarized chains created by the hydrogen L-malate anion via O-H⋯O interactions, directed along the polar sixfold axis. The material shows a second harmonic generation with a rotationally averaged effective second order susceptibility equal to 0.70 of potassium dihydrogen phosphate at an incident wavelength of 1064 nm.
Space- and Time-resolved Emission Features of Micro- and Nano-sized Perylene-based Zr Metal-Organic Frameworks
(2024-10-15) Romero-Muñiz, Ignacio; García Calvo, José; Romero-Muñiz, Carlos; Rodríguez San Miguel, David; Torres, Tomás; Zamora, Félix; Bottari, Giovanni; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Agencia Estatal de Investigación. España; Ministerio de Ciencia e Innovación (MICIN). España; Comunidad Autónoma de Madrid
While many photoresponsive metal‒organic frameworks (MOFs) have been reported to date, finding applications in several technologically relevant fields such as photocatalysis, sensors, and light-emitting devices, significantly scarcer are the reports addressing the relationship between the MOFs emissive features and their crystalline domain size (i.e., micro- and nano-sized materials). Herein, a valuable contribution is offered to this issue which consists of the use of reticular chemistry to prepare a Zr-MOF featuring spatially separated tetracarboxylated-functionalized perylenes as ligand. Single crystal X-ray analysis of such Zr-MOF revealed the formation of micro- and meso-porous channels. The perylene-based Zr-MOF exhibited notable optoelectronic features, including a relatively small optical bandgap of 1.82 eV and emission features different from that of the constituting perylene ligand in the solid state. Additionally, local probe techniques are used to unveil the emission properties of isolated Zr-MOF crystals. Space- and time-resolved fluorescence studies revealed a strong dependence of the emissive features of the Zr-MOF, both in terms of its intensity and lifetime, to the crystalline domain size.
Fabrication of Al2O3-Y3Al5O12-ZrO2 composites by single-step spark plasma sintering
(Elsevier, 2025-03-12) Vakhshouri, Maryam; Talimian, Ali; Najafzadehkhoee, Aliasghar; Gallardo López, Ángela María; Poyato, Rosalía; Gutiérrez Mora, Felipe; Galusek, Dušan; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Union (UE)
Fabricating Al2O3-Y3Al5O12-ZrO2 ceramic composites with a eutectic microstructure is challenging and costly, as it requires high-temperature melting of precursor materials. Here, we report on the successful production of Al2O3-Y3Al5O12- 5 mol% ZrO2 composites with lamellar eutectic microstructure through single-step spark plasma sintering (SPS) of sol-gel synthesized powder. The release of volatile species from partially calcined powders, due to limited calcination at 1000°C for 2 h, as well as their fine particle size, were used to create the conditions for local electric discharge and plasma formation during SPS; this resulted in the local formation of eutectic liquids, enabling the formation of lamellar microstructures. The microstructural features can be tailored by modifying the calcination process.
Diversity and composition of ocular microbiota in contact lens wearers: Efficacy of liposomal ozonated oil
(Elsevier, 2025-06) Sánchez González, María del Carmen; Gallardo Real, Inmaculada; Gutiérrez Sánchez, Estanislao; Hita Cantalejo, María Concepción de; Capote Puente, Raúl; Sánchez González, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Cirugía
Purpose: To characterize the ocular surface microbiota in regular contact lens wearers with dry eyes and assess the effectiveness of reducing bacterial load using a liposomal ozonated oil solution. Methods: This prospective, longitudinal, controlled study randomized subjects into two groups. Group A (45 subjects) received hydroxypropylmethylcellulose (HPMC, Artific®), while Group B (41 subjects) received ozonated sunflower seed oil with soybean phospholipids (OSSO, Ozonest®). Microbial communities were analyzed via DNA metabarcoding of the 16S rRNA gene, and statistical analyses (alpha and beta diversity) were performed in R. Results: Both groups predominantly harbored Staphylococcus caprae, Streptococcus oralis, and Corynebacterium spp., with OSSO and HPMC users showing distinct bacterial profiles. Alpha diversity showed no significant differences, but beta diversity revealed differences in bacterial composition between the groups. Conclusions: The results seem to indicate that the use of ozonized oil reduces the bacterial load compared to the solution used as a control.
Efficacy of eyelid warming devices as first-step treatment in meibomian gland dysfunction: A systematic review with meta-analysis
(Elsevier, 2025-07) Ballesteros Sánchez, Antonio; Rocha de Lossada, Carlos; Sánchez González, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Universidad de Sevilla. Departamento de Cirugía
Purpose: To investigate the efficacy of eyelid warming devices as first-step treatment in patients with meibomian gland dysfunction (MGD). Methods: A systematic review with meta-analysis of RCTs, reporting the effects eyelid warming devices in 3 databases, PubMed, Scopus and Web of Science, was performed according to the PRISMA statement. Results: Seven studies including 367 patients, and 440 eyes were analysed. The overall efficacy did not significantly favor either group when comparing eyelid warming devices to the control groups or warm towel compresses, nor between moisture chamber devices and warm compress devices. However, the change in OSDI questionnaire (SMD 0.91; 95 % CI: 0.44 to 1.39; P = 0.0002) and NIBUT (SMD 1.10; 95 % CI: 0.61 to 1.59; P < 0.0001) were significantly favorable for eyelid warming devices compared to the control groups. Similar results were obtained for tear film stability (SMD 0.97; 95 % CI: 0.32 to 1.61; P = 0.003) when comparing eyelid warming devices to warm towel compresses. Specifically, the sensitivity analysis of these groups revealed that changes in OSDI questionnaire (MD 9.41; 95 % CI: 1.70 to 17.13; P = 0.02; I2 = 49 %) and NIBUT (MD 2.24; 95 % CI: 1.20 to 3.28; P < 0.0001; I2 = 71 %) were significantly favorable for eyelid warming devices. When comparing moisture chamber devices and warm compress devices, only the change in TBUT (SMD 0.75; 95 % CI: 0.23 to 1.28; P = 0.005; I2 = 30 %) were significantly favorable for moisture chamber goggles. Conclusions: Despite their limited overall efficacy, eyelid warming devices significantly reduce OSDI questionnaire and improve NIBUT compared to controls or warm towel compress groups. Evidence remains insufficient to confirm whether moisture chamber devices provide better outcomes than warm compress devices. Further well-designed RCTs are needed to confirm these findings.
Outcomes of Corneal Compound Hyperopic Astigmatism With Presbyopia by Zeiss PRESBYOND Laser Blended Vision LASIK Using Default Custom Refractive Software Master Target Refractions for Reduced Anisometropia
(Slack Incorporated, 2024) Hernández Lucena, Julia; Alonso Aliste, Federico; Amián Cordero, Jonatan; Sánchez González, José María; Universidad de Sevilla. Departamento de Física de la Materia Condensada
PURPOSE: To evaluate the effectiveness, safety, and stability of a modified PRESBYOND Laser Blended Vision protocol (Carl Zeiss Meditec AG) for correcting hyperopic astigmatism and presbyopia, using Custom Refractive Software Master (CRSM) targeting over a 6-month period. METHODS: A total of 636 eyes of 318 patients with a mean age of 51.05 ± 4.71 years (range: 40 to 60 years) met the inclusion and exclusion criteria. All patients completed a 6-month follow-up. CRSM software was used to generate ablation profiles for the MEL90 excimer laser (Carl Zeiss Meditec AG). The target refraction was emmetropic for the dominant eyes and between -0.75 and -1.12 diopters (D) for the near eyes. RESULTS: Visual and refractive results were studied separately by the dominant and non-dominant eyes. The mean attempt to correct for spherical equivalent refraction was +2.17 ± 1.16 D (range: -1.00 to +5.37 D). The mean attempted cylinder was -0.60 ± 0.75 D (range: -4.00 to 0.00 D). All eyes monocularly achieved uncorrected distance visual acuity (UDVA) of 20/25 or better after refractive treatment and 88% achieved 20/20. Binocularly all eyes achieved UDVA of 20/25 or better and 96.54% achieved 20/20. Ninety-eight percent of the patients maintained their corrected distance visual acuity before surgery and UDVA 6 months after surgery. CONCLUSIONS: This hyperopic micro-anisometropia protocol with PRESBYOND Laser Blended Vision was an effective, safe, and well-tolerated refractive treatment. It was an effective procedure with excellent results for UDVA and uncorrected near visual acuity and demonstrates that binocular summation exists.
Phase transition behavior in ferroelectric BaTi0.8Zr0.2O3: Evidence of polar cluster reorientation above Curie temperature
(AIP Publishing, 2025-05-27) Aktas, Oktay; Romero Landa, Francisco Javier; He, Zhengwang; Linyu, Gan; Ding, Xiangdong; Martín Olalla, José María; Gallardo Cruz, María del Carmen; Lookman, Turab; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Natural National Science Foundation of China (NSFC); Scientific and Technological Research Council of Turkey (TÜBİTAK)
We study the phase transition behavior of the ferroelectric BaTi0.8Zr0.2O3 in the paraelectric region above the Curie temperature. The investigation of the phase transition using caloric, dielectric, and elastic measurements indicates that the ferroelectric transition at Tc = 292 K is continuous and displays weakly relaxor characteristics. The nonlinear scaling of entropy and polarization, as well as the temperature dependencies of dielectric and elastic properties, indicates the presence of local structures in the paraelectric phase. The non-zero remnant polarization is measured up to a characteristic temperature T* ∼ 350 K. This temperature coincides with the temperature where the dielectric constant deviates from the Curie–Weiss law and is identified as the coherence temperature T*, associated with the formation of static polar nanostructures. Finally, direct current field cooling in the paraelectric phase using fields smaller than the coercive field leads to an elastic response and remnant piezoelectricity below T*, attributed to the re-orientation of polar nanostructures. The observed remnant effect, along with the temperature dependence of the piezoelectric effect and its time dependence below and above T*, is consistent with increased coherence and slower dynamics of these structures on cooling, leading to symmetry-disallowed remnant piezoelectricity due to glassy behavior below T*.
Tuning the Curie Temperature in γ-FeNi Nanoparticles for Magnetocaloric Applications by Controlling the Oxidation Kinetics
(AIP Publishing, 2013) Ucar, Huseyin; Ipus Bados, Jhon Jairo; Laughlin, D. E.; McHenry, M. E.; Universidad de Sevilla. Departamento de Física de la Materia Condensada
Mechanically alloyed Fe70Ni30 and Fe 72Ni28 alloys were characterized in terms of their structural and magnetic properties. Previous studies showed that single phase FCC γ-FeNi alloys with ∼26-30 at. Ni have Curie temperatures, T c, near room temperature. Having Tc near room temperatures along with large magnetization makes γ-FeNi alloys attractive for room temperature magnetocaloric cooling technologies. To obtain a single γ-phase, particles were solution annealed in the γ-phase field and water quenched. The preferential oxidation of Fe during ball milling was used as a means to tune the Curie temperature, Tc, of the alloy. Refrigeration capacities, RCFWHM, of the Fe70Ni 30 and the Fe72Ni28 alloys were calculated to be ≈470 J/kg and 250 J/kg at 5 T, with peak temperatures ≈363 K and ≈333 K, respectively. The RCFWHM for the Fe70Ni 30 is higher than the previously reported Nanoperm (Fe 70Ni30)89Zr7B4 type alloy and on the same order of magnitude with other Fe-based alloys. The maximum magnetic entropy change values observed for the Fe70Ni30 and the Fe72Ni28 are 0.65 and 0.5 J kg-1 K -1, respectively, at a field of 5 T. These are smaller than those of rare earth magnetic refrigerants showing first order transformation behavior. The larger RCFWHM value results mainly from the width of the magnetic entropy curve in these types of materials. We discuss the economic advantage of these rare earth free refrigerants.
The Role of Artificial Intelligence in Optometric Diagnostics and Research: Deep Learning and Time-Series Forecasting Applications
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Santos, Luis F.F.M.; Sánchez Tena, Miguel Ángel; Álvarez Peregrina, Cristina; Sánchez González, José María; Martínez Pérez, Clara; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Fundação para a Ciência e a Tecnologia. Portugal
This study introduces an Artificial Intelligence framework based on the Deep Learning model Bidirectional Encoder Representations from Transformers framework trained on a dataset from 2000–2023. The AI tool categorizes articles into six classes: Contactology, Low Vision, Refractive Surgery, Pediatrics, Myopia, and Dry Eye, with supervised learning enhancing classification accuracy, achieving F1-Scores averaging 86.4%, AUC at 0.98, Precision at 87%, and Accuracy at 86.8% via one-shot training, while Epoch training showed 85.9% Accuracy and 92.8% Precision. Utilizing the Artificial Intelligence model outputs, the Autoregressive Integrated Moving Average model provides forecasts from all classes through 2030, predicting decreases in research interest for Contactology, Low Vision, and Refractive Surgery but increases for Myopia and Dry Eye due to rising prevalence and lifestyle changes. Stability is expected in pediatric research, highlighting its focus on early detection and intervention. This study demonstrates the effectiveness of AI in enhancing diagnostic precision and strategic planning in optometry, with potential implications for broader clinical applications and improved accessibility to eye care.
The impact of interfacial quality and nanoscale performance disorder on the stability of alloyed perovskite solar cells
(Nature Research, 2024-10-30) Frohna, Kyle; Chosy, Cullen; Al-Ashouri, Amral; Scheler, Florian; Chiang, Yu-Hsien; Dubajic, Milos; Anaya Martín, Miguel; Stranks, Samuel D.; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Union (UE). H2020; Engineering Physical Sciences Research Council (EPSCR) U. K.
Microscopy provides a proxy for assessing the operation of perovskite solar cells, yet most works in the literature have focused on bare perovskite thin flms, missing charge transport and recombination losses present in full devices. Here we demonstrate a multimodal operando microscopy toolkit to measure and spatially correlate nanoscale charge transport losses, recombination losses and chemical composition. By applying this toolkit to the same scan areas of state-of-the-art, alloyed perovskite cells before and after extended operation, we show that devices with the highest macroscopic performance have the lowest initial performance spatial heterogeneity—a crucial link that is missed in conventional microscopy. We show that engineering stable interfaces is critical to achieving robust devices. Once the interfaces are stabilized, we show that compositional engineering to homogenize charge extraction and to minimize variations in local power conversion efciency is critical to improve performance and stability. We fnd that in our device space, perovskites can tolerate spatial disorder in chemistry, but not charge extraction.
Revisiting Stability Criteria in Ball-Milled High-Entropy Alloys: Do Hume–Rothery and Thermodynamic Rules Equally Apply?
(Willey, 2024-10-07) Blázquez Gámez, Javier Sebastián; Manchón Gordón, Alejandro F.; Vidal Crespo, Antonio; Caballero Flores, Rafael; Ipus Bados, Jhon Jairo; Conde Amiano, Clara Francisca; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Junta de Andalucía; Universidad de Sevilla
Stability descriptors for the formation of solid solutions can be divided into two categories: inspired by Hume–Rothery rules (HRR) and derived from thermodynamic approaches. Herein, HRRs are extended from binary to high-entropy alloys (HEAs) focusing on compositions prepared by ball milling. Parameters describing stability criteria are interrelated and implicitly account for the microstrains’ storage energy, more determinant than entropy increase in stabilization of HEAs and more effective in bcc structures than close-packed ones (fcc and hcp). An effective temperature, Teff, is defined as the ratio between increase in metallic bonding energy of solid solutions with respect to segregated pure constituents and configurational entropy. This versatile parameter is used as a threshold for stabilization of HEAs at equilibrium and out of equilibrium. When Teff is below room temperature, HEA would be stable at equilibrium. When Teff is below melting temperature, HEA would be obtained by rapid quenching. Limitations related to electronegativity differences remain valid in mechanically alloyed solid solutions. However, ball milling broadens the allowed differences in atomic size to form HEA. Moreover, thermodynamic criteria can be surpassed in these systems, allowing the formation of single-phase solid solutions beyond the compositional range predicted by those criteria.
Magnetostructural transformation and magnetocaloric response in Mn(Fe)NiSi(Al) alloys
(Elsevier, 2024-09-30) Khan, Aun N.; Moreno Ramírez, Luis Miguel; Law, Jia Yan; Franco García, Victorino; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Oficina de Investigación Científica de la Fuerza Aérea. EE. UU.; European Innovation Council. E. U,
An efficient magnetocaloric refrigerant must have certain characteristics such as a sharp transition near the desired working temperature, a large cyclic magnetocaloric response, and the use of raw materials with reduced costs and low environmental consequences. In this sense, this work focuses on a series of rare-earth- and Co-free Mn0.5Fe0.5NiSi1-xAlx alloys (x = 0.0525, 0.060, 0.0685) with promising magnetocaloric properties. The alloys were synthesized using combined arc melting and induction melting techniques, as this synthesis route provides improved control on the sample composition and homogeneity. We investigated how the heat treatment temperature and Al content affect the magnetostructural and magnetocaloric properties of the alloys. On the one hand, it is found that annealing at 1173 K for 7 days leads to a sharp magnetostructural transformation with no traces of impurities for the alloy with x = 0.0525. Under these conditions, a large isothermal entropy change of –11.5 J kg−1 K−1 for 1 T is obtained near room temperature, significantly improving the value of the as-cast sample. On the other hand, following this optimal heat treatment, the influence of Al content is studied: upon increasing the Al concentration the magnetostructural transformation shifts to lower temperatures, ranging from 320 K for x = 0.0525 to 220 K for x = 0.0685 (measured upon heating).
Interplay between connectivity and passivating agents in perovskite quantum dot networks
(Royal Society of Chemistry, 2024-10-02) Morán Pedroso, María; Tiede, David O.; Romero-Pérez, Carlos; Calvo, Mauricio E.; Galisteo López, Juan F.; Míguez, Hernán; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; Unión Europea NextGeneration; Junta de Andalucía
Introducing quantum dots (QDs) as the active element of an optoelectronic device demands its incorporation in the shape of interconnected arrays that allow for some degree of electronic coupling in order to inject/extract charge carriers. In doing so, beyond reducing the degree of quantum confinement, carriers are exposed to an enhanced defect landscape as they can access adjacent QDs, which is at the origin of the strong reduction of photoluminescence observed in QD solids when compared to that of the isolated QDs. In this work we demonstrate how a proper defect passivating strategy or atmospheric treatment can greatly enhance charge diffusion in a QD film, needed for an optimal carrier injection/extraction demanded for optoelectronic applications, and also improved its stability against external radiation. From a fundamental perspective, we provide evidence showing that trap density distribution, rather than QD size distribution, is mostly responsible for the observed variations in emission decay rates present in the QD networks under analysis.
Influence of the chemical activation with KOH/KNO3 on the CO2 adsorption capacity of activated carbons from pyrolysis of cellulose
(Elsevier, 2024-10-07) Lamata Bermejo, Irene; Alba, María D.; Ramírez Rico, Joaquín; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Junta de Andalucía; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
Plant biomass is an attractive precursor to prepare activated carbons with high surface area for CO2 adsorption due to its low-cost and easy regeneration. Despite this interest, there are still remaining questions regarding the optimal processing conditions and the choice of activating agent. Moreover, since plant biomass shows a highly variable proportion of different biopolymers (cellulose, hemicellulose, lignin), it is important to understand the activation effect on each constituent. In this work, carbons obtained from pyrolysis of cellulose were activated using two potassium salts, using two different activation temperatures. The samples were characterized to elucidate the influence of the activation conditions on their CO2 adsorption capacity. In general, all the carbons activated at higher temperature showed higher adsorption capacity. These results are comparable with other carbons derived from biomass described in the bibliography. Among the activated carbons studied, the carbon activated only with KOH exhibits the highest CO2 adsorption capacity at 1 bar meanwhile the highest adsorption capacity at saturation pressure belongs to the carbon activated with larger ratio of KNO3.
Compositional Gradient of Mixed Halide 2D Perovskite Interface Boosts Outdoor Stability of Highly Efficient Perovskite Solar Cells
(Willey, 2023-12-23) Degani, Matteo; Pallotta, Riccardo; Pica, Giovanni; Karimipour, Masoud; Mirabelli, Alessandro; Frohna, Kyle; Anaya Martín, Miguel; Grancini, Giulia; Universidad de Sevilla. Departamento de Física de la Materia Condensada; European Research Council (ERC); European Union (UE). H2020; Engineering and Physical Sciences Research Council (UK)
Interface engineering using self-assembled 2D perovskite interfaces is a consolidated route to efficient and durable perovskite solar cells. Whether the 2D perovskite forms a homogeneous conformal layer or is heterogeneously distributed on the surface, interface defects are passivated, leading to a general improvement in the device's open circuit voltage (VOC) and stability. Here, an innovative strategy is developed for manipulating the composition of the 2D/3D perovskite interface that results in the formation of a gradient halide distribution, which extends from the surface to the bulk. The use of a bromide-based 2D perovskite triggers a progressive Br/I exchange, affecting not only the surface but also the perovskite underneath. As a result, not only the device VOC improve, as expected, but also the photogenerated current is boosted, leading to a device efficiency of up to 24.4%. Such mixed halide gradient effectively passivates surface and bulk defects making the perovskite active layer more efficient and robust, as demonstrated by the superior device stability showing zero losses in performances upon 36 days (more than 800 h) test in outdoor conditions, those ones relevant for a marketable product.
Better together: Monolithic halide perovskite@metal-organic framework composites
(Cell Press, 2024-12-04) Ávila, Elena; Salway, Hayden; Ruggeri, Edoardo; Çamur, Ceren; Rampal, Nakul; Doherty, Tiarnan A. S.; Moseley, Oliver D. I.; Stranks, Samuel D.; Fairen Jiménez, David; Anaya Martín, Miguel; Universidad de Sevilla. Departamento de Física de la Materia Condensada; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España
A few years ago, we theoretically studied the production of a stellar neutron spectrum at kT 30 keV using a shaped proton beam impinging on a thick lithium target. Here, we first measure the proton distribution to better control the produced neutron spectrum. Then, we measure the forward-emitted angle-integrated neutron spectrum of the 7Li(p,n)7Be reaction via time-of-flight neutron spectrometry with such proton distribution. The result resembles a stellar neutron spectrum at kT 30 keV. This method avoids in activation experiments the need for spectrum correction. In the case of spherical samples, no knowledge of the crosssection of the isotope being measured by activation would be necessary. Therefore, the present method is of interest for isotopes with unknown or poorly known cross-sections, such as branching points in astrophysics. The key point of our method is the experimental control of the proton distribution that impinges on the lithium target.
Thermomagnetic liquid metal switches with fast bidirectional response
(Springer Nature, 2025-03-17) Chen, Haodong; Xie, Yuyu; Qiao, Kaiming; Xie, Longlong; Yu, Ziyuan; Xu, Chenyu; Liu, Jingyi; Liu, Mingze; Lu, Yongyu; Law, Jia Yan; Franco García, Victorino; Zhang, Hu; Universidad de Sevilla. Departamento de Física de la Materia Condensada; National Natural Science Foundation of China; National Key Research and Development Program of China; State Key Laboratory for Advanced Metals and Materials; Agencia Estatal de Investigación. España; Junta de Andalucía
Traditional thermal switches usually suffer from long-time and unidirectional response. Herein, we combined liquid metals with magnetic Ni2Mn1.4In0.6 particles and developed a thermomagnetic liquid metal. These materials not only show excellent fluidity and electrical conductivity, but also exhibit fast response at a tuneable temperature that traditional magnetic liquid metals do not have. The ultimate application is designed as micro-channel thermal switch. Particularly, our thermal switch features bidirectional response through the droplet displacement, thus simultaneously cutting off the working circuit while turning on the fire extinguishing. Its response time of 1.2 s is 3.3 − 5.6 times faster than typical commercial thermal switches under the same hot source temperature of 75 °C, and it can be further reduced to 660 ms under the optimal environment. Moreover, this fast-response thermal switch offers the fastest recovery time, low cost, and long-cycle stability, showing a huge potential as a generation of thermal switches for diverse applications.
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.

Examinar

Envíos recientes