Coupled electric and magnetic dipole formulation for planar arrays of dipolar particles: metasurfaces with various electric and/or magnetic meta-atoms per unit cell

The optical properties of infinite planar array of scattering particles, metasurfaces and metagratings, are attracting special attention lately for their rich phenomenology, including both plasmonic and high-refractive-index dielectric meta-atoms with a variety of electric and magnetic resonant responses. Herein we derive a coupled electric and magnetic dipole (CEMD) analytical formulation to describe the reflection and transmission of such periodic arrays, including specular and diffractive orders, valid in the spectral regimes where only dipolar multipoles are needed. Electric and/or magnetic dipoles with all three orientations arising in turn from a single or various meta-atoms per unit cell are considered. The 2D lattice Green function is rewritten in terms of a 1D (chain) version that fully converges and can be easily calculated. Modes emerging as poles of such lattice Green function can be extracted. This formulation can be applied to investigate a wealth of plasmonic, all-dielectric, and hybrid metasurfaces/metagratings of interest throughout the electromagnetic spectrum.Comment: 8 pages, 4 figure

Tailoring accidental double bound states in the continuum in all-dielectric metasurfaces

Bound states in the continuum (BICs) have been thoroughly investigated due to their formally divergent Q-factor, especially those emerging in all-dielectric, nanostructured metasurfaces from symmetry protection at the $\Gamma$ point (in-plane wavevector $k_{||}=0$). Less attention has been paid to accidental BICs that may appear at any other $k_{||}\not =0$ in the band structure of supported modes, being in turn difficult to predict. Here we make use of a coupled electric/magnetic dipole model to determine analytical conditions for the emergence of accidental BICs, valid for any planar array of meta-atoms that can be described by dipolar resonances, which is the case of many nanostructures in the optical domain. This is explored for all-dielectric nanospheres through explicit analytical conditions that allow us in turn to predict accidental BIC positions in the parameter space $(\omega,\bf{k_{||}}$). Finally, such conditions are exploited to determine not only single, but also double (for both linear polarizations) accidental BICs occurring at the same position in the dispersion relation $\omega-\bf{k_{||}}$ for realistic semiconductor nanodisk meta-atoms. This might pave the way to a variety of BIC-enhanced light-matter interaction phenomena at the nanoscale such as lasing or non-linear conversion, that benefit from emerging at wavevectors away from the $\Gamma$ point (off-normal incidence) overlapping for both linear polarizations.Comment: 18 pages, 7 figure

Kerker Conditions Upon Lossless, Absorption, and Optical Gain Regimes

The directionality and polarization of light show peculiar properties when the scattering by a dielectric sphere can be described exclusively by electric and magnetic dipolar modes. Particularly, when these modes oscillate in-phase with equal amplitude, at the so-called first Kerker condition, the zero optical backscattering condition emerges for non-dissipating spheres. However, the role of absorption and optical gain in the first Kerker condition remains unexplored. In this work, we demonstrate that either absorption or optical gain precludes the first Kerker condition and, hence, the absence of backscattered radiation light, regardless of the size of the particle, incident wavelength, and incoming polarization. Finally, we derive the necessary prerequisites of the second Kerker condition of the zero forward light scattering, finding that optical gain is a compulsory requirement

Génesis de la atención en la relación alumno – Objeto de Aprendizaje en un entorno de aprendizaje [Genesis of the attention in the relationship student - Object of Learning in a learning environment]

Los Objetos de Aprendizaje (OA) que se utilizan actualmente en un entorno educativo se centran en el uso de herramientas tecnológicas., la interacción con dichas herramientas genera diversas respuestas en un usuario. Para analizar el tipo de interacción así como la respuesta dada por un estudiante ante la relación alumno – OA se realizó un estudio con algunos de los OA´s más usuales en un aula de clase: PowerPoint (PPT), Objetos de aprendizaje de representación estereoscópica (OAE) y revista especializada. Se detectó a través de la observación en cámara de Gesell que cada herramienta por sus cualidades sensibles y de interacción con su sistema de trabajo genera respuestas en el alumno durante el proceso de percepción que impacta en la atención del alumno en la relación alumno - OA. Con los resultados obtenidos se concluyó que aquellos OA´s que son ejecutados con autonomía, de forma no lineal y con altos niveles de interacción motora provocan altos niveles de atención en el alumno. Por lo tanto es fundamental analizar los OA utilizados en un ambiente educativo para generar una correcta transferencia de información. [Learning Objects (LO) currently used in an educational environment focus on the use of technological tools. Each technological tool for its sensitive qualities as well as interaction with its work system generates answers in the student during the process of perception of information that impacts on the attention of the student in the relation student - LO. To analyze the type of interaction on this relationship, a study was carried out with some of the most common LO's in a classroom: PowerPoint (PPT), Stereoscopic Learning Objects (SLO), a specialist magazine. It was detected in Gesell ´s camera that each tool for its sensitive qualities and interaction with its work system generates responses in the student during the perception process that impacts on the student' s attention in the student - LO relationship. With the results obtained it was concluded that those LO's that are executed with autonomy, in a non-linear way and with high levels of motor interaction, cause high levels of attention in the student. Therefore is essential to analyze the LO used in an educational environment to generate a correct transfer of information.

Silver-based terpyridine complexes as antitumor agents

Silver complexes bearing substituted terpyridine or tetra-2-pyridinylpyrazine ligands have been prepared and structurally characterised. The study of the anticancer properties of silver complexes with this type of ligands is scarce, despite the possibilities of combining the properties of the metal and the ability of the ligands for DNA binding. Here, the antiproliferative activity, stability, CT-DNA binding and mechanism of cell death of these types of derivatives are studied. High cytotoxicity against different tumour cells was observed, and, more important, a great selectivity index has been detected between tumour cells and healthy Lymphocytes T for some of these compounds. The CT-DNA interaction study has shown that these derivatives are be able to interact with CT-DNA via moderate intercalation. Furthermore, cell death studies indicate that these derivatives promote the apoptosis via mitochondrial pathway

Impact of an intradialysis virtual-reality-based exercise program on healthcare resources expenditure: a micro-costing analysis

[EN] Background Engagement in exercise by haemodialysis (HD) patients has been shown to generate benefits both in terms of improved functional capacity and in the health-related quality of life. The use of non-immersive virtual reality (VR) games represents a new format for the implementation of intradialysis exercise. Some studies have shown that engaging in exercise for 6 months reduces the consumption of antihypertensive drugs and decreases the time spent admitted to hospital among individuals receiving HD treatments. The objective of this study was to evaluate changes in the consumption of healthcare resources and micro-costing for patients on HD who completed a VR exercise program. Materials and methods Design: This study is a secondary analysis of a clinical trial. The participants performed an intradialysis exercise program with non-immersive virtual reality for 3 months. The variables were recorded in two periods: 12 months before and 12 months after the start of the exercise program. Results The micro-costing analysis showed a significant decrease in the mean cost, in euros, for the consumption of laboratory tests - 330 (95% CI:[- 533, - 126];p = 0.003), outpatient visits - 351 ([- 566, - 135];p = 0.003), and radiology tests - 111 ([- 209, - 10];p = 0.03) in the 12 months after the implementation of the exercise program relative to the 12 months prior to its start. Conclusion The implementation of intradialysis exercise programs decreased the expenditure of some healthcare resources. Future studies could help clarify if longer interventions would have a stronger impact on these cost reductions.Funding was received from a research prize awarded by the nonprofit organization 'Fundacion Renal Tomas de Osma' as well as from a research grant (IDOC 17-19), a research project (FUSP-BS-PPC14/2017) grant from the Universidad Cardenal Herrera-CEU and a research project (PID2019-108814RA-100) from the Spanish Government 'Ministerio de Ciencia e Innovacion'.García-Testal, A.; Martínez-Olmos, FJ.; Gil-Gómez, J.; Villalón-Coca, J.; Ortiz-Ramón, R.; Cana-Poyatos, A.; García-Maset, R.... (2022). Impact of an intradialysis virtual-reality-based exercise program on healthcare resources expenditure: a micro-costing analysis. BMC Nephrology. 23(1). https://doi.org/10.1186/s12882-022-02859-823

Hemodynamic Tolerance of Virtual Reality Intradialysis Exercise Performed during the Last 30 Minutes versus the Beginning of the Hemodialysis Session

[EN] Background: Exercise improves the physical function of people suffering from chronic kidney disease on hemodialysis (HD). Virtual reality is a new type of intradialysis exercise that has a positive impact on physical function. Intradialysis exercise is recommended during the first 2 h, but its safety in the last part of the dialysis session is unknown. Methods: This was a pilot sub-study of a clinical trial. Several hemodynamic control variables were recorded, including blood pressure, heart rate, and intradialytic hypotensive events. These variables were recorded during three different HD sessions, one HD session at rest, another HD session with exercise during the first two hours, and one HD session with exercise during the last 30 min of dialysis. The intradialysis virtual reality exercise was performed for a maximum of 30 min. Results: During exercise sessions, there was a significant increase in heart rate (6.65 (4.92, 8.39) bpm; p < 0.001) and systolic blood pressure (6.25 (0.04,12.47) mmHg; p < 0.05). There was no difference in hemodynamic control between the sessions with exercise during the first two hours and the sessions with exercise during the last 30 min. There was no association between intra-dialytic hypotensive events at rest (five events) or exercise at any point (two vs. one event(s), respectively). Conclusion: performing exercise with virtual reality at the end of a hemodialysis session is not associated with hemodynamic instability.Funding included a research project (PID2019-108814RA-I00) supported by the Spanish Government 'Ministerio de Ciencia e Innovacion', a research prize awarded by the nonprofit organization Fundacion Renal Tomas de Osma, as well as from a research grant (IDOC 17-19 and PPC14/2017) awarded by the Universidad Cardenal Herrera CEU.García-Testal, A.; Martínez-Olmos, FJ.; Gil-Gómez, J.; López-Tercero, V.; Lahoz-Cano, L.; Hervás-Marín, D.; Cana-Poyatos, A.... (2023). Hemodynamic Tolerance of Virtual Reality Intradialysis Exercise Performed during the Last 30 Minutes versus the Beginning of the Hemodialysis Session. Healthcare. 11(1). https://doi.org/10.3390/healthcare1101007911