Geometry-induced enhancement factor improvement in covered-gold-nanorod-dimer antennas

Illuminated gapped-gold-nanorod dimers hold surface plasmon polaritons (SPPs) that can be engineered, by an appropriate choice of geometrical parameters, to enhance the electromagnetic field at the gap, allowing applications in molecular detection via surface-enhanced Raman spectroscopy (SERS). Envisioning hybrid devices in which the SERS spectroscopy of molecules in the gap is complemented by electrical measurements, it arises the question of designing efficient geometries to contact the nanorods without decreasing the enhancement factor (EF) of the nanoantenna, i.e., the figure of merit for SERS spectroscopy. Within this framework we theoretically study the feasibility to fabricate designs based on covering with gold the far-from-the-gap areas of the dimer. We show that by tuning the geometrical parameters of the designs these systems can reach enhancement factors larger than the best achieved in the uncovered dimer: this supremacy survives even in the presence of dimer asymmetries and vacancies at the interfaces between the nanorods and the covering layers. Our results show that geometrical modifications away from the gap can improve the optical response at the gap, thus enabling the use of these devices both for hybrid and optical applications.Comment: 10 pages, 8 figure

Effect of the excitation setup in the improved enhancement factor of covered-gold-nanorod-dimer antennas

Devices possessing the ability to sense both electrically and optically molecular targets are of fundamental and technological interest. Towards this end, it has been shown that covering the ends of gapped gold-nanorod-dimer nanoantennas can improve the enhancement factor (EF) that quantifies the nanoantenna efficiency for surface-enhancement Raman spectroscopy (SERS) for an incident wave coming from the top of the sample. Here, as the covering breaks the top-bottom symmetry, we investigate the behaviour of the EF for excitation coming from the bottom of the sample. This is relevant in presence of a reflecting substrate or due to the placement of the device in a cavity field. We also study the case of a superposition of waves coming from both directions in the limit cases in which a node or an antinode of the total incident field lies at the center of the gold nanorods. In all these situations we find that the EF of the covered device can continue to be higher than for the uncovered case when the geometrical parameters are tuned to the peak values of the calculated enhancement factor

Propiedades de los suelos cafetaleros en zonas productivas de Colon y Panamá Oeste

La siembra de café robusta adquiere mayor interés entre productores panameños como alternativa de conservación de suelos. El objetivo fue caracterizar las propiedades de los suelos de fincas productoras de café en las provincias de Colón y Panamá Oeste para la elaboración de cartillas de fertilización regionalizadas de acuerdo con las características edafoclimáticas de cada zona. En 15 fincas de la provincia de Colón y 20 de Panamá Oeste, se tomaron muestras en dos profundidades (0-20 y 20-40 cm) para conocer sus propiedades e iniciar un programa de fertilización sostenible que coadyuve en el mejoramiento de la productividad. Se elaboraron mapas digitales utilizando el programa Q-Gis v.2.2. y cartillas de fertilizacion regionalizada para cada zona. Los suelos de la provincia de Colón 47% presentaron alto porcentaje de saturación de aluminio, pH promedio de 4.6, bajos niveles de materia orgánica y de fósforo, 53% bajos en potasio. El 80% están altos en magnesio, 40% en calcio. Se encontraron desbalances en las relaciones Ca/Mg y Ca + Mg/K, lo que ocasiona problemas nutricionales. En Panamá Oeste 30% presentaron alto porcentaje de saturación de aluminio, pH promedio de 5.3 y 1.4% de materia orgánica, 100% están bajos en fósforo, 90% bajos en potasio, niveles medios y altos de magnesio y calcio. Se encontró correlación positiva y estadísticamente significativa entre % de arcilla, materia orgánica, pH y calcio. Se espera con esta caracterización y las cartillas de fertilización regionalizadas lograr mejorar las propiedades de los suelos en forma sostenible

Extensión de la afectación pulmonar por tomografía en pacientes con neumonía por SARS-CoV-2

Objective. To determine the extent of pulmonary involvement in patients with SARS-CoV-2 pneumonia usingtomography. Method. Retrospective evaluation in patients with evidence of COVID-19 at the Guillermo Almenara Irigoyen National Hospital, Lima - Peru, at the beginning of the COVID-19 pandemic, between March 15 and May 14, 2020. The extent of pneumonia was determined by means of tomography based on the Classification of the French Society of Thoracic Imaging. Results. 485 patients were included in the study. The extent of pneumonia was: 1.2% absent, 4.9% minimal, 20.6% moderate, 27.4% extensive, 30.7% severe, and 15.1% critical. Lung involvement was associated with age older than 60 years (p = 0.014) andambient oxygen saturation below 90% (n = 372, p = 0.000). Conclusions. Due to its extension, the SARSCoV-2 pneumonia in the first two months of the COVID-19 epidemic at Hospital Almenara were severe, extensive and mostly moderate. The extent of pneumonia was associated with age and ambient oxygen saturation at admission.Objetivo. Determinar la extensión de la afectación pulmonar en pacientes con neumonía por SARS-CoV-2 mediante tomografía. Método. Evaluación retrospectiva en pacientes con evidencia de COVID-19 del Hospital Nacional Guillermo Almenara Irigoyen, Lima - Perú, al inicio de la pandemia COVID-19, entre el 15 de marzo y el 14 de mayo de 2020. La extensión de la neumonía se determinó mediante tomografía con base en la Clasificación de la Sociedad Francesa de Imagen Torácica. Resultados. Se incluyeron en el estudio 485 pacientes. La extensión de la neumonía fue: ausente 1,2%, mínima 4,9%, moderada 20,6%, extensa 27,4%, grave 30,7% y crítica 15,1%. La afectación pulmonar se asoció con edad mayor de 60 años (p=0,014) y saturación de oxígeno ambiental por debajo de 90% (n=372, p=0,000). Conclusiones. Por su extensión, las neumonías por SARS-CoV-2 en los primeros dos meses de la epidemia de COVID-19 en el Hospital Almenara fueron graves, extensas y moderadas en su gran mayoría. La extensión de la neumonía se asoció con edad y saturación de oxígeno ambiental al ingreso

Control repetitivo impar de alto orden de un rectificador monofásico: operación a frecuencia variable

Controlled rectifiers are electronic power devices aimed at reducing the harmonic pollution in electrical networks caused by the power conversion process. The main goal is to obtain a sinusoidal shape current in phase with the voltage network. Although Proportional Integral controllers are widely used for the current control loop, they do not provide high performance results. On the contrary, Resonant and Repetitive Control are techniques with remarkable results on this area. However, their main drawback is the lost of performance due to frequency changes in the exogenous signal. In this work, the implementation of an Odd Harmonic High Order Repetitive Controller is proposed for the rectifier current loop. The odd harmonic characteristic of this compensator makes possible to obtain a computational burden that is very similar to the one obtained by conventional repetitive controllers with the advantage of increase the robustness against frequency variations. Experimental results show the high performance obtained even when the network frequency does not match the designed nominal frequency.Los rectificadores de potencia controlados son dispositivos utilizados con el fin de minimizar la contaminación armónica producida en las redes eléctricas durante el proceso de conversión de la potencia. El objetivo es obtener una corriente de entrada sinusoidal en fase con el voltaje de la red. Aunque es extenso el uso del control Proporcional Integral en el lazo de corriente, no es posible lograr altos desempeños con estos compensadores. Por otro lado, el Control Repetitivo y el Control Resonante son técnicas mediante las cuales se logran resultados excepcionales. La desventaja de estas estrategias de control es la gran pérdida de desempeño en el sistema cuando la frecuencia de lared se desvía de su valor nominal. En este artículo, se propone el uso de un Controlador Repetitivo Impar de Alto Orden para el lazo de corriente del rectificador. Este controlador se diseña para obtener una señal sinusoidal de corriente y rechazar los armónicos impares introducidos en el sistema. Al atacar sólo los armónicos impares, el costo computacional de su implementación resulta muy similar al del controlador repetitivo convencional, con la ventaja de proporcionar robustez ante cambios en la frecuencia de la red. Los resultados experimentales muestran el alto desempeño del compensador aún cuando la frecuencia de la red se desvía del valor nominal de diseño

Registering the evolutionary history in individual-based models of speciation

Understanding the emergence of biodiversity patterns in nature is a central problem in biology. Theoretical models of speciation have addressed this question in the macroecological scale, but little has been done to connect microevolutionary processes with macroevolutionary patterns. Knowledge of the evolutionary history allows the study of patterns underlying the processes being modeled, revealing their signatures and the role of speciation and extinction in shaping macroevolutionary patterns. In this paper we introduce two algorithms to record the evolutionary history of populations and species in individual-based models of speciation, from which genealogies and phylogenies can be constructed. The first algorithm relies on saving ancestor–descendant relationships, generating a matrix that contains the times to the most recent common ancestor between all pairs of individuals at every generation (the Most Recent Common Ancestor Time matrix, MRCAT). The second algorithm directly records all speciation and extinction events throughout the evolutionary process, generating a matrix with the true phylogeny of species (the Sequential Speciation and Extinction Events, SSEE). We illustrate the use of these algorithms in a spatially explicit individual-based model of speciation. We compare the trees generated via MRCAT and SSEE algorithms with trees inferred by methods that use only genetic distance between individuals of extant species, commonly used in empirical studies and applied here to simulated genetic data. Comparisons between trees are performed with metrics describing the overall topology, branch length distribution and imbalance degree. We observe that both MRCAT and distance-based trees differ from the true phylogeny, with the first being closer to the true tree than the second.Facultad de Ciencias Naturales y Muse

It is the time for oceanic seabirds: Tracking year-round distribution of gadfly petrels across the Atlantic Ocean

Main conclusions: Tracking movements of highly mobile vertebrates such as gadfly petrels can provide a powerful tool to evaluate and assess the potential need for and location of protected oceanic areas. As more multispecies, year-round data sets are collected from wide-ranging vertebrates, researchers and managers will have greater insight into the location of biodiversity hotspots. These can subsequently inform and guide marine spatial planning efforts that account for both conservation and sustainable use of resources such as commercial fisheries

Global spatial ecology of three closely-related gadfly petrels

The conservation status and taxonomy of the three gadfly petrels that breed in Macaronesia is still discussed partly due to the scarce information on their spatial ecology. Using geolocator and capture-mark-recapture data, we examined phenology, natal philopatry and breeding-site fidelity, year-round distribution, habitat usage and at-sea activity of the three closely-related gadfly petrels that breed in Macaronesia: Zino's petrel Pterodroma madeira, Desertas petrel P. deserta and Cape Verde petrel P. feae. All P. feae remained around the breeding area during their non-breeding season, whereas P. madeira and P. deserta dispersed far from their colony, migrating either to the Cape Verde region, further south to equatorial waters in the central Atlantic, or to the Brazil Current. The three taxa displayed a clear allochrony in timing of breeding. Habitat modelling and at-sea activity patterns highlighted similar environmental preferences and foraging behaviours of the three taxa. Finally, no chick or adult was recaptured away from its natal site and survival estimates were relatively high at all study sites, indicating strong philopatry and breeding-site fidelity for the three taxa. The combination of high philopatry, marked breeding asynchrony and substantial spatio-temporal segregation of their year-round distribution suggest very limited gene flow among the three taxa

Synthesis and characterization of a Bio-MOF based on mixed adeninate/tricarboxylate ligands and zinc ions

Artículo científicoIn this work, we present a new metal organic framework Zn7(Ad)4(BTC)4(DMF)O·4DMA·3DMF·4H2O which was synthesized under hydrothermal conditions with adenine and trimesic acid (BTC) linkers. The structure was determined by single-crystal (XRD) and the compound was further characterized by Scanning electron microscopy (SEM), infrared spectroscopy (IR), and thermogravimetric analysis. The 3D anionic framework includes adenine present in two-different coordination modes, with dimethylammonium balancing the framework charg