Control of the Light Interaction in a Semiconductor Nanoparticle Dimer Through Scattering Directionality

11 págs.; 4 figs.; 1 tab.Dimers of nanoparticles are very interesting for several devices due to the possibility of obtaining intense light concentrations in the gap between them. A dynamic control of this interaction to obtain either the maximum or minimum light through interferential effects could be also relevant for a multitude of devices such as chemical sensors or all-optical devices for interchip/intrachip communications. Semiconductor nanoparticles satisfying Kerker conditions present an anisotropic scattering distribution with a minimum in either the forward or the backward direction and prominent scattering in the contrary direction. The reduction or enhancement of the electromagnetic field in a certain direction can minimize or maximize the interaction with neighboring nanoparticles. In this paper, we consider a dimer of nanoparticles such that each component satisfies each one of the Kerker conditions. Depending on the arrangement of the nanoparticles with respect to the impinging light direction, we can produce a minimum or a maximum of the electric field between them, reducing or maximizing the interferential effects. The strong dependence of the directional conditions with external conditions, such as the incident wavelength, can be used to dynamically control the light concentration in the gap. Ó 2016 IEEEThis work was supported in part by the Ministerio de Economía y Competitividad of Spain under Grant TEC2013—50138—EXP and Grant TEC2013-47342-C2-2-R, by the RD Program of the Comunidad de Madrid under Grant SINFOTON S2013/MIT—2790, and by COST Action IC1208.Peer Reviewe

Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

International audienceWe report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company) covering the range from 300?1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain) of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study

An electrochromic ionic liquid: design, characterisation and performance in a solid state platform

This work describes the synthesis and characteristics of a novel electrochromic ionic liquid (IL) based on a phosphonium core tethered to a viologen moiety. When integrated into a solid-state electrochromic platform, the viologen modified IL behaved as both the electrolyte and the electrochromic material. Platform fabrication was achieved through in situ photo-polymerisation and encapsulation of this novel IL within a hybrid sol-gel. Important parameters of the platform performance, including its coloration efficiency, switching kinetics and optical properties were characterised using UV/Vis spectroscopy and cyclic voltammetry in tandem. The electrochromic platform exhibits a coloration efficiency of 10.72 cm2C-1, and a varied optical output as a function of the incident current. Despite the rather viscous nature of the material, the platform exhibited approximately two orders of magnitude faster switching kinetics (221 seconds to reach 95 % absorbance) when compared to previously reported electrochromic ILs (18,000 seconds)

Adopting a high-polyphenolic diet is associated with an improved glucose profile: prospective analysis within the PREDIMED-plus trial

Previous studies suggested that dietary polyphenols could reduce the incidence and complications of type-2 diabetes (T2D); although the evidence is still limited and inconsistent. This work analyzes whether changing to a diet with a higher polyphenolic content is associated with an improved glucose profile. At baseline, and at 1 year of follow-up visits, 5921 participants (mean age 65.0 ± 4.9, 48.2% women) who had overweight/obesity and metabolic syndrome filled out a validated 143-item semi-quantitative food frequency questionnaire (FFQ), from which polyphenol intakes were calculated. Energy-adjusted total polyphenols and subclasses were categorized in tertiles of changes. Linear mixed-effect models with random intercepts (the recruitment centers) were used to assess associations between changes in polyphenol subclasses intake and 1-year plasma glucose or glycosylated hemoglobin (HbA1c) levels. Increments in total polyphenol intake and some classes were inversely associated with better glucose levels and HbA1c after one year of follow-up. These associations were modified when the analyses were run considering diabetes status separately. To our knowledge, this is the first study to assess the relationship between changes in the intake of all polyphenolic groups and T2D-related parameters in a senior population with T2D or at high-risk of developing T2D

A new feeding concept offering speciesappropriate animal enrichment and visitor attraction at the same time

Zoological gardens are considered important institutions for human-animal interactions. Facilitating human-animal contacts and the simultaneous protection of the animals from possible distress by visitors represent an important task of zoological gardens. We investigated the effects of a new roughage feeding setup for zoo-kept domestic herbivores on both, animals and visitors. In the setup, visitors are provided with roughages to put into feeding troughs for the animals. Data collection via video monitoring of domestic cattle (Bos primigenius taurus, B. p. indicus) enclosures and associated visitors’ areas took place over a 30-day period for two consecutive years at three different zoological gardens. In one zoo the setup was in place in both years, and in the two others it was introduced in the second year prior to data recording. At the two zoos where the feeding regime was introduced, the average daily number of visitors and the overall time they spent together with animals (but not the average time per visitor) increased, as did the number of times that an animal approached a visitor. While there was no differencebetween the years in overall feeding time, feeding was more evenly distributed across the day after the introduction of visitor feeding, with a higher number of feeding bouts per animal. The setup offers possibilities for enhancing welfare of certain animals and simultaneously offering an individual visitor feeding experience

Study of desert dust events over the southwestern Iberian Peninsula in year 2000: two case studies

Strong desert dust events occurring in 2000 over the southwestern Atlantic coast of the Iberian Peninsula are detected and evaluated by means of the TOMS Aerosol Index (A.I.) at three different sites, Funchal (Madeira Island, Portugal), Lisboa (Portugal) and El Arenosillo (Huelva, Spain). At the El Arenosillo station, measurements from an AERONET Cimel sunphotometer allow a more precise retrieval of the spectral AOD and the derived alpha Ångström coefficient. After using different threshold values of these parameters, we conclude that it is difficult to establish reliable and robust criteria for an automatic estimation of the number of dust episodes and the total number of dusty days per year. As a result, additional information, such as airmass trajectories, were used to improve the estimation, from which reasonable results were obtained (although some manual editting was still needed). A detailed characterization of two selected desert dust episodes, a strong event in winter and another of less intensity in summer, was carried out using AOD derived from Brewer spectrometer measurements. Size distribution parameters and radiative properties, such as arefractive index and the aerosol single scattering albedo derived from Cimel data, were analyzed in detail for one of these two case studies. Although specific to this dust episode, the retrieved range of values of these parameters clearly reflect the characteristics of desert aerosols. Back-trajectory analysis, synoptic weather maps and satellite images were also considered together, as supporting data to assess the aerosol desert characterization in this region of study

Estudio de la influencia de los aerosoles sobre la reflectancia de los canales 1 y 2 del sensor AVHRR-NOAA y el NDVI.

En este trabajo se presenta un estudio sobre el efec. to de la atmósfera en la radiancia de los canales 1 y 2 del sensor AVHRR-NOAA, así como sobre el índice de vegetación NDVI derivado de ellas. Para ello se ha puesto a punto un modelo de transferencia radiativa que permite evalúar la radiancia o la reflectancia en el límite superior de la atmósfera a partir de las medidas experimentales del albedo de la superficie y de los parámetros atmosféricos necesarios. Se han establecido las diferencias entre el NDVI calculado en el nivel de observación del sensor del satélite con el medido en el nivel de suelo, así como las dependencias del mismo y de las señales de los canales 1 y 2 del sensor referido con los parámetros que definen las caracte. rísticas de los aerosoles atmosféricos. Estos se destacan como el factor más importante debido a su varia. bilidad tanto temporal como espacial. Se concluye la importancia de la corrección atmosférica en el estudio y comparación de las diversas cubiertas vegetales en las imágenes de este sensor, así como la necesidad de medir, a tal efecto, el espesor óptico de aerosoles en la atmósfer

Tunable Impedance Properties of Bismuth Nanoparticles

Boston, Massachusetts (USA), November 29-December 4, 2015; http://www.mrs.org/fall2015/Since several years ago, light is considered as a new way for futuristic computation, overcoming current limitations of electronics [1]. Researchers are currently working in the development and implementation of photonic devices that behave as a counterpart of electronic devices, in the so-called field of Metatronics [2]. One of the main challenges of this field is the implementation of optical circuitry. In this sense, photonic equivalent resistors, capacitors and inductors are needed. Engheta and coworkers [3] showed that nanostructures with convenient effective optical properties present impedance properties similar to that of these lumped elements. However, the main handicap of these devices lies on their complex implementation as well as their passive properties. Current research on semiconductor and semimetal nanostructures is showing new impressive properties, such as optical magnetism [4]. In this work, we focus our attention on the impedance properties of bismuth (Bi) nanospheres. By a simulation tool implementing the finite elements method (COMSOL ©), we observe that these nanoparticles have a remarkable capacitive impedance in the near-infrared part of the spectrum. Changing the particle size, the value of the impedance can be tuned through a wide spectral range. The simplicity of the structure and its fabrication makes it a good candidate as integrated nanocapacitor in potential optical circuits. In addition, by heating the nanoparticle over its melting point (T=2710C), its impedance changes fastly from purely capacitive to a purely inductive. [1] D.A.B. Miller. Are optical transistors the logical next step? Nature Photon. 4, 3-5 (2010). [2] H. Caglayan, S.-H. Hong, B. Edwards, C. R. Kagan, and N. Engheta. Near-Infrared Metatronic Nanocircuits by Design. Phys. Rev. Lett. 111, 073904 (2013). [3] Y. Sun, B. Edwards, A. Alù and N. Engheta. Experimental realization of optical lumped nanocircuits at infrared wavelengths. Nature Mater.11, 208-212 (2012). [4] J.M. Geffrin, B. García.Cámara, R. Gómez- Medina, P. Albella, L.S. Froufe-Pérez, C. Eyraud, A. Litman, R. Vaillon, F. González, M. Nieto-Vesperinas, J.J. Sáenz, F. Moreno. Magnetic and electric coherence in forward-and back-scattered electromagnetic waves by a single dielectric subwavelength sphere. Nature Commum. 3, 1171 (2012).Peer Reviewe