Plasmonic gold nanodiscs using piezoelectric substrate birefringence for liquid sensing

This article presents the simulation, fabrication, and experimental characterization of a surface plasmonic resonance (SPR) sensor integrated with an acoustic sensing compatible substrate. The SPR sensor is designed to work in the visible region with gold nanodisc arrays fabricated on LiNbO3, which is both piezoelectric and birefringent. A linear relationship between resonance wavelength and varying liquid refractive indices were observed in experiments, and a sensitivity of 165 nm/refractive index unit was obtained. Polarization effects of the birefringent property of the Y-cut LiNbO3 substrate have been investigated, which can also be applied to X-cut LiNbO3. Our study demonstrates the feasibility of an SPR sensor device utilizing a birefringent substrate, which has acoustic wave compatibility and can pave the way toward much more robust and flexible biosensing device

Habitat connectivity in reef fish communities and marine reserve design in Old Providence-Santa Catalina, Colombia

On the insular platform of Old Providence/Santa Catalina, Colombia, we compared nearshore lagoonal patch reefs to those on the northern bank distant from the islands to determine the importance of habitat connectivity to fish community structure. Nearshore patch reefs had greater proximity to mangrove, seagrass and rocky shore habitats, and they had significantly more individuals. Nearshore reefs also tended to have a greater total biomass, more species, a higher proportion of predators of mobile invertebrates and small fishes, and a lower proportion of herbivores. Biomass of snappers and grunts at nearshore sites was four times greater compared to bank sites, and was correlated with the amount of seagrass and sand/rubble habitat within 500 m of each patch reef. We also compared length-frequency distributions and abundances of grunts and snappers among all sites (deep and shallow forereefs, patch reefs and deep and shallow leeside slopes). The results were consistent with ontogenetic migrations from shallow sites, primarily seagrass and mangrove habitats, to deeper sites and to those further out on the bank. The evidence suggests that species differed in both distance and direction of dispersal, which may be affected by the abundance and distribution of preferred habitats. Marine reserves near the islands should target nearshore nursery areas and patch reefs harboring species of limited dispersal capability. Reserves on the northern bank would protect spawners of those species showing the greatest dispersal capability

Octave-spanning broadband absorption of terahertz light using metasurface fractal-cross absorbers

Synthetic fractals inherently carry spatially encoded frequency information that renders them as an ideal candidate for broadband optical structures. Nowhere is this more true than in the terahertz (THz) band where there is a lack of naturally occurring materials with valuable optical properties. One example are perfect absorbers that are a direct step toward the development of highly sought after detectors and sensing devices. Metasurface absorbers that can be used to substitute for natural materials suffer from poor broadband performance, while those with high absorption and broadband capability typically involve complex fabrication and design and are multilayered. Here, we demonstrate a polarization-insensitive ultrathin (∼λ/6) planar metasurface THz absorber composed of supercells of fractal crosses capable of spanning one optical octave in bandwidth, while still being highly efficient. A sufficiently thick polyimide interlayer produces a unique absorption mechanism based on Salisbury screen and antireflection responses, which lends to the broadband operation. Experimental peak absorption exceeds 93%, while the average absorption is 83% from 2.82 THz to 5.15 THz. This new ultrathin device architecture, achieving an absorption-bandwidth of one optical octave, demonstrates a major advance toward a synthetic metasurface blackbody absorber in the THz ban

Is there a link between autistic people being perceived unfavorably and having a mind that is difficult to read?

YesThe link between autistic people having a mind that is difficult to read (by neurotypical participants) and being perceived unfavorably was investigated. Videoed Autistic and neurotypical targets from Sheppard et al. (PLOS ONE 7(11):e49859, 2016) were scored for how readable they were when reacting to a distinctive greeting from the experimenter. These videos were presented to new groups of perceivers (neurotypical adults) who rated neurotypical targets more socially favorably than autistic targets irrespective of whether details of the experimenter’s greeting were concealed (Study 1) or disclosed (Study 2). Target readability correlated with ratings of target favorability (r = .58 and r = .63), independent of target diagnosis. Perceivers might rate targets unfavorably because they experience difficulty reading them, though other interpretations of the correlation are also possible.Saudi Government Scholarship from the Saudi Arabian Cultural Bureau (SACB)

Body water conservation through selective brain cooling by the carotid rete: a physiological feature for surviving climate change?

Some mammals have the ability to lower their hypothalamic temperature below that of carotid arterial blood temperature, a process termed selective brain cooling. Although the requisite anatomical structure that facilitates this physiological process, the carotid rete, is present in members of the Cetartiodactyla, Felidae and Canidae, the carotid rete is particularly well developed in the artiodactyls, e.g. antelopes, cattle, sheep and goats. First described in the domestic cat, the seemingly obvious function initially attributed to selective brain cooling was that of protecting the brain from thermal damage. However, hyperthermia is not a prerequisite for selective brain cooling, and selective brain cooling can be exhibited at all times of the day, even when carotid arterial blood temperature is relatively low. More recently, it has been shown that selective brain cooling functions primarily as a water-conservation mechanism, allowing artiodactyls to save more than half of their daily water requirements. Here, we argue that the evolutionary success of the artiodactyls may, in part, be attributed to the evolution of the carotid rete and the resulting ability to conserve body water during past environmental conditions, and we suggest that this group of mammals may therefore have a selective advantage in the hotter and drier conditions associated with current anthropogenic climate change. A better understanding of how selective brain cooling provides physiological plasticity to mammals in changing environments will improve our ability to predict their responses and to implement appropriate conservation measures.EM201

Ultra-narrow line width polarization-insensitive filter using a symmetry-breaking selective plasmonic metasurface

Plasmonic metasurfaces provide unprecedented control of the properties of light. By designing symmetry-breaking nanoholes in a metal sheet and engineering the optical properties of the metal using geometry, highly selective transmission and polarisation control of light is obtained. To date such plasmonic filters have exhibited broad (> 200 nm) transmission linewidths in the NIR and as such are unsuitable for applications requiring narrow passbands, e.g. multi-spectral imaging. Here we present a novel sub-wavelength elliptical and circular nanohole array in a metallic film that simultaneously exhibits high transmission efficiency, polarisation insensitivity and narrow linewidth. The experimentally obtained linewidth is 79 nm with a transmission efficiency of 44%. By examining the electric and magnetic field distributions for various incident polarisations at the transmission peak we show that the narrowband characteristics are due to a Fano resonance. Good agreement is obtained between the experimental data, simulations and analytical calculations. Our design can be modified to operate in other regions of the electromagnetic spectrum and these filters may be integrated with suitable detectors such as photodiodes and single photon avalanche diode (SPAD) arrays

Global observations of 2 day wave coupling to the diurnal tide in a high‐altitude forecast‐assimilation system

We examine wave components in a high-altitude forecast-assimilation system that arise from nonlinear interaction between the diurnal tide and the westward traveling quasi 2 day wave. The process yields a westward traveling “sum” wave with zonal wave number 4 and a period of 16 h, and an eastward traveling “difference” wave with zonal wave number 2 and a period of 2 days. While the eastward 2 day wave has been reported in satellite temperatures, the westward 16 h wave lies outside the Nyquist limits of resolution of twice daily local time satellite sampling. Hourly output from a high-altitude forecast-assimilation model is used to diagnose the nonlinear quadriad. A steady state primitive equation model forced by tide-2 day wave advection is used to intepret the nonlinear wave products. The westward 16 h wave maximizes in the midlatitude winter mesosphere and behaves like an inertia-gravity wave. The nonlinearly generated component of the eastward 2 day wave maximizes at high latitudes in the lower thermosphere, and only weakly penetrates to low latitudes. The 16 h and the eastward 2 day waves are of comparable amplitude and alias to the same apparent frequency when viewed from a satellite perspective

Solving Non-Stationary Bandit Problems by Random Sampling from Sibling Kalman Filters

The multi-armed bandit problem is a classical optimization problem where an agent sequentially pulls one of multiple arms attached to a gambling machine, with each pull resulting in a random reward. The reward distributions are unknown, and thus, one must balance between exploiting existing knowledge about the arms, and obtaining new information. Dynamically changing (non-stationary) bandit problems are particularly challenging because each change of the reward distributions may progressively degrade the performance of any fixed strategy. Although computationally intractable in many cases, Bayesian methods provide a standard for optimal decision making. This paper proposes a novel solution scheme for bandit problems with non-stationary normally distributed rewards. The scheme is inherently Bayesian in nature, yet avoids computational intractability by relying simply on updating the hyper parameters of sibling Kalman Filters, and on random sampling from these posteriors. Furthermore, it is able to track the better actions, thus supporting non-stationary bandit problems. Extensive experiments demonstrate that our scheme outperforms recently proposed bandit playing algorithms, not only in non-stationary environments, but in stationary environments also. Furthermore, our scheme is robust to inexact parameter settings. We thus believe that our methodology opens avenues for obtaining improved novel solutions