Magnetic-field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters

We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semiconductors become ideal hyperbolic near-field emitters. More importantly, by changing the magnetic field, the system can be continuously tuned from a situation where the surface waves dominate the heat transfer to a situation where hyperbolic modes completely govern the near-field thermal radiation. We show that this high tunability can be achieved with accessible magnetic fields and very common materials like n-doped InSb or Si. Our study paves the way for an active control of NFRHT and it opens the possibility to study unique hyperbolic thermal emitters without the need to resort to complicated metamaterials.Comment: 21 pages, 10 figure

Extracting dimer structures from simulations of organic-based materials using QM/MM methods

The functionality of weakly bound organic materials, either in Nanoelectronics or in Materials Science, is known to be strongly affected by their morphology. Theoretical predictions of the underlying structure–property relationships are frequently based on calculations performed on isolated dimers, but the optimized structure of the latter may significantly differ from experimental data even when dispersion-corrected methods are used for it. Here, we address this problem on two organic crystals, namely coronene and 5,6,11,12-tetrachlorotetracene, concluding that it is caused by the absence of the surrounding monomers present in the crystal, and that it can be efficiently cured when the dimer is embedded into a general Quantum Mechanics/Molecular Mechanics (QM/MM) geometry optimization scheme. We also investigate how the size of the MM region affects the results. These findings may be helpful for the simulation of the morphology of active materials in crystalline or glassy samples.This work is supported by the “Ministerio de Economía y Competitividad” of Spain and the “European Regional Development Fund” through project CTQ2014–55073-P

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

We have carefully investigated the structural and electronic properties of coronene and some of its fluorinated and chlorinated derivatives, including full periphery substitution, as well as the preferred orientation of the non-covalent dimer structures subsequently formed. We have paid particular attention to a set of methodological details, to first obtain single-molecule magnitudes as accurately as possible, including next the use of modern dispersion-corrected methods to tackle the corresponding non-covalently bound dimers. Generally speaking, this class of compounds is expected to self-assembly in neighboring π-stacks with dimer stabilization energies ranging from –20 to –30 kcal mol−1 at close distances around 3.0–3.3 Å. Then, in a further step, we have also calculated hole and electron transfer rates of some suitable candidates for ambipolar materials, and corresponding charge mobility values, which are known to critically depend on the supramolecular organization of the samples. For coronene and per-fluorinated coronene, we have found high values for their hopping rates, although slightly smaller for the latter due to an increase (decrease) of the reorganization energies (electronic couplings).This work is supported by the “Ministerio de Educación y Ciencia” of Spain and the “European Regional Development Fund” through Project No. CTQ2011-27253

Theoretical Insights for Materials Properties of Cyclic Organic Nanorings

The synthesis of new carbon nanoforms with remarkable and fine‐tuned bulk properties still represents a formidable challenge, with cyclic organic nanorings emerging in recent years for the template‐driven design of this kind of systems. The design and engineering of these materials can be first controlled at the molecular scale, to further induce their specific self‐assembly toward tailored properties at the nanoscale. Theoretical studies have lately contributed to the understanding of the underlying physical effects, the development of synthetic strategies, and the rationalization of novel materials properties, employing a variety of methods ranging from accurate calculations of isolated molecules to atomistic molecular dynamics simulations of a large sample of molecules in realistic conditions, which will be reviewed here with a focus on the transition from single‐molecule to supramolecular properties.Computational resources were provided along the years by projects CTQ2014-55073-P and PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”) and AICO/2018/175 (“Generalitat Valenciana”)

Determining the cohesive energy of coronene by dispersion-corrected DFT methods: Periodic boundary conditions vs. molecular pairs

We investigate the cohesive energy of crystalline coronene by the dispersion-corrected methods DFT-D2, DFT-D3, and DFT-NL. For that purpose, we first employ bulk periodic boundary conditions and carefully analyze next all the interacting pairs of molecules within the crystalline structure. Our calculations reveal the nature and importance of the binding forces in every molecular pair tackled and provide revised estimates of the effects of two- and three-body terms, leading to accurate results in close agreement with experimental (sublimation enthalpies) reference values.Financial support by the “Ministerio de Economía y Competitividad” of Spain and the “European Regional Development Fund” through Project No. CTQ2011-27253. The work in Mons was supported by the “Programme d’Excellence de la Région Wallonne” (OPTI2MAT project) and FNRS-FRFC

Subphenotyping of Mexican Patients With COVID-19 at Preadmission To Anticipate Severity Stratification: Age-Sex Unbiased Meta-Clustering Technique

[EN] Background: The COVID-19 pandemic has led to an unprecedented global health care challenge for both medical institutions and researchers. Recognizing different COVID-19 subphenotypes-the division of populations of patients into more meaningful subgroups driven by clinical features-and their severity characterization may assist clinicians during the clinical course, the vaccination process, research efforts, the surveillance system, and the allocation of limited resources. Objective: We aimed to discover age-sex unbiased COVID-19 patient subphenotypes based on easily available phenotypical data before admission, such as pre-existing comorbidities, lifestyle habits, and demographic features, to study the potential early severity stratification capabilities of the discovered subgroups through characterizing their severity patterns, including prognostic, intensive care unit (ICU), and morbimortality outcomes. Methods: We used the Mexican Government COVID-19 open data, including 778,692 SARS-CoV-2 population-based patient-level data as of September 2020. We applied a meta-clustering technique that consists of a 2-stage clustering approach combining dimensionality reduction (ie, principal components analysis and multiple correspondence analysis) and hierarchical clustering using the Ward minimum variance method with Euclidean squared distance. Results: In the independent age-sex clustering analyses, 56 clusters supported 11 clinically distinguishable meta-clusters (MCs). MCs 1-3 showed high recovery rates (90.27%-95.22%), including healthy patients of all ages, children with comorbidities and priority in receiving medical resources (ie, higher rates of hospitalization, intubation, and ICU admission) compared with other adult subgroups that have similar conditions, and young obese smokers. MCs 4-5 showed moderate recovery rates (81.30%-82.81%), including patients with hypertension or diabetes of all ages and obese patients with pneumonia, hypertension, and diabetes. MCs 6-11 showed low recovery rates (53.96%-66.94%), including immunosuppressed patients with high comorbidity rates, patients with chronic kidney disease with a poor survival length and probability of recovery, older smokers with chronic obstructive pulmonary disease, older adults with severe diabetes and hypertension, and the oldest obese smokers with chronic obstructive pulmonary disease and mild cardiovascular disease. Group outcomes conformed to the recent literature on dedicated age-sex groups. Mexican states and several types of clinical institutions showed relevant heterogeneity regarding severity, potentially linked to socioeconomic or health inequalities. Conclusions: The proposed 2-stage cluster analysis methodology produced a discriminative characterization of the sample and explainability over age and sex. These results can potentially help in understanding the clinical patient and their stratification for automated early triage before further tests and laboratory results are available and even in locations where additional tests are not available or to help decide resource allocation among vulnerable subgroups such as to prioritize vaccination or treatments.We sincerely thank the different types of clinical institutions and the Mexican government, which made a huge effort to make these data publicly available. We also thank the clinicians and epidemiologists from the Servicios de Salud de Nayarit for the useful discussions on specific aspects of the medical attention to hospitalized patients and the reporting of epidemiological data processes related to COVID-19. Furthermore, we would also like to thank Francisco Tomas Garcia Ruiz for his valuable help in data visualization design. This work was supported by Universitat Politecnica de Valencia contract no. UPV-SUB.2-1302 and FONDO SUPERA COVID-19 by CRUE-Santander Bank grant: "Severity Subgroup Discovery and Classification on COVID-19 Real World Data through Machine Learning and Data Quality assessment (SUBCOVERWD-19) ." The authors thank the Institute for Information and Communication Technologies (ITACA) at the Universitat Politecnica de Valencia for its support in the publication of this manuscript.Zhou, L.; Romero-Garcia, N.; Martínez-Miranda, J.; Conejero, JA.; Garcia-Gomez, JM.; Sáez Silvestre, C. (2022). Subphenotyping of Mexican Patients With COVID-19 at Preadmission To Anticipate Severity Stratification: Age-Sex Unbiased Meta-Clustering Technique. JMIR Public Health and Surveillance. 8(3):1-21. https://doi.org/10.2196/300321218

A counterfactual Rydberg gate for photons

Quantum computation with photons requires efficient two photon gates. We put forward a two photon entangling gate which uses an intermediate atomic system. The system includes a single Rydberg atom which can switch on and off photon absorption in an ensemble using the dipole blockade. The gate is based in a counterfactual protocol. The mere possibility of an absorption that can only occur with a vanishing probability steers the photons to the desired final state.Comment: 4 Figures. 6 pages of tex

Universal quantum computation with the Orbital Angular Momentum of a single photon

We prove that a single photon with quantum data encoded in its orbital angular momentum can be manipulated with simple optical elements to provide any desired quantum computation. We will show how to build any quantum unitary operator using beamsplitters, phase shifters, holograms and an extraction gate based on quantum interrogation. The advantages and challenges of these approach are then discussed, in particular the problem of the readout of the results.Comment: First version. Comments welcom

Integration of a Canine Agent in a Wireless Sensor Network for Information Gathering in Search and Rescue Missions

Search and rescue operations in the context of emergency response to human or natural disasters have the major goal of finding potential victims in the shortest possible time. Multi-agent teams, which can include specialized human respondents, robots and canine units, complement the strengths and weaknesses of each agent, like all-terrain mobility or capability to locate human beings. However, efficient coordination of heterogeneous agents requires specific means to locate the agents, and to provide them with the information they require to complete their mission. The major contribution of this work is an application of Wireless Sensor Networks (WSN) to gather information from a multi-agent team and to make it available to the rest of the agents while keeping coverage. In particular, a canine agent has been equipped with a mobile node installed on a harness, providing information about the dog’s location as well as gas levels. The configuration of the mobile node allows for flexible arrangement of the system, being able to integrate static as well as mobile nodes. The gathered information is available at an external database, so that the rest of the agents and the control center can use it in real time. The proposed scheme has been tested in realistic scenarios during search and rescue exercises

Diseño de la trama urbana y cobertura de las redes de transporte público

Una de las claves en su uso del transporte público es la accesibilidad de la población a las paradas o estaciones. Los planificadores del transporte han buscado siempre localizaciones de paradas y estaciones en espacios con un volumen importante de población residente y/o empleo en su entorno inmediato. En los últimos años, se conjugan también políticas urbanísticas para generar nuevos desarrollos urbanos orientados al uso del transporte público. Se busca potenciar las llamadas 3D: densidad, diversidad de usos y diseño urbano. En esta comunicación el objetivo es analizar cómo influye el diseño de la trama urbana en la cobertura de las redes de transporte público (cantidad de población y el empleo en el entorno próximo de las estaciones). La metodología se apoya en el uso de Sistemas de Información Geográfica, sobre los que se han diseñado varios tipos de viarios, y para los que miden las superficies cubiertas y las distancias recorridas a estaciones localizadas en el centro de cada uno de ellos. Posteriormente, se hace un ejercicio de simulación donde se ha tomado el Metro de la ciudad de Madrid, y se han superpuesto sobre todas las estaciones de la red cada uno de los viarios tipo. Así, es posible calcular la población y el empleo cubiertos para cada uno de los escenarios tipo y compararla con la cobertura y la calidad de acceso a las estaciones a través del viario real de la ciudad. Al mantenerse fija las distribuciones de población y empleo, las diferencias se explican exclusivamente por el diseño de la trama urbana. Los resultados muestran como viarios orientados las estaciones incrementan notablemente la población y el empleo cubiertos