Broadband and energy-concentrating terahertz coherent perfect absorber based on a self-complementary metasurface

We demonstrate that a self-complementary checkerboard-like metasurface works as a broadband coherent perfect absorber (CPA) when symmetrically illuminated by two counter-propagating incident waves. A theoretical analysis based on wave interference and results of numerical simulations of the proposed metasurface are provided. In addition, we experimentally demonstrate the proposed CPA in the terahertz regime by using a time-domain spectroscopy technique. We observe that the metasurface can work as a CPA below its lowest diffraction frequency. The size of the absorptive areas of the proposed CPA can be much smaller than the incident wavelength. Unlike conventional CPAs, the presented one simultaneously achieves the broadband operation and energy concentration of electromagnetic waves at the deep-subwavelength scale.Comment: 5 pages, 4 figure

Plane-wave scattering by self-complementary metasurfaces in terms of electromagnetic duality and Babinet's principle

We investigate theoretically electromagnetic plane-wave scattering by self-complementary metasurfaces. By using Babinet's principle extended to metasurfaces with resistive elements, we show that the frequency-independent transmission and reflection are realized for normal incidence of a circularly polarized plane wave onto a self-complementary metasurface, even if there is diffraction. Next, we consider two special classes of self-complementary metasurfaces. We show that self-complementary metasurfaces with rotational symmetry can act as coherent perfect absorbers, and those with translational symmetry compatible with their self-complementarity can split the incident power equally, even for oblique incidences

Frequency-Independent Response of Self-Complementary Checkerboard Screens

This research resolves a long-standing problem on the electromagnetic response of self-complementary metallic screens with checkerboardlike geometry. Although Babinet's principle implies that they show a frequency-independent response, this unusual characteristic has not been observed yet due to the singularities of the metallic point contacts in the checkerboard geometry. We overcome this difficulty by replacing the point contacts with resistive sheets. The proposed structure is prepared and characterized by terahertz time-domain spectroscopy. It is experimentally confirmed that the resistive checkerboard structures exhibit a flat transmission spectrum over 0.1--1.1 THz. It is also demonstrated that self-complementarity can eliminate even the frequency-dependent transmission characteristics of resonant metamaterials.Comment: 6 pages, 5 figures + Supplemental Material (6 pages, 7 figures

Neuronal and glial prostaglandin D synthase isozymes in chick dorsal root ganglia: a light and electron microscopic immunocytochemical study.

Homogenates of chick dorsal root ganglia (DRG) and in vitro cultures of DRG neurons are known to synthesize prostaglandin (PG) D2. To specify the PGD synthase isozymes controlling PGD2 synthesis in DRG and to identify the DRG cells responsible for this synthesis, we applied polyclonal antibodies raised against rat brain or rat spleen PGD synthase isozymes to vibratome or cryostat slices of DRG previously fixed with a formaldehyde-lysine-periodate mixture and permeabilized with Triton X-100. The immunoreactivity indicating rat spleen PGD synthase, a glutathione (GSH)-requiring enzyme, was located in satellite cells encompassing particular large neurons of class A and in Schwann cells myelinating and enwrapping their initial axonal segments. In contrast, the immunoreactivity of rat brain PGD synthase, a GSH-independent enzyme, was restricted to particular ganglion cell perikarya: 33% of the DRG neurons were immunostained for rat brain PGD synthase, including 2% of large class A neurons and 40% of small class B neurons. Only 3.3% of rat brain PGD synthase-immunoreactive small B neurons coexpressed substance P, indicating that the immunoreactive neurons belong to the B1 subclass. By electron microscopy, 71 of 72 immunoreactive DRG cells were identified as small B neurons of the B1 subclass, and 71 of 77 B1 neurons were immunoreactive for rat brain PGD synthase. These results demonstrate that PGD2 formation in DRG is regulated by two isozymes: the GSH-requiring isozyme located in satellite and Schwann cells and the GSH-independent isozyme-confined to small B1 neurons

Dietary Zinc Acts as a Sleep Modulator

While zinc is known to be important for many biological processes in animals at a molecular and physiological level, new evidence indicates that it may also be involved in the regulation of sleep. Recent research has concluded that zinc serum concentration varies with the amount of sleep, while orally administered zinc increases the amount and the quality of sleep in mice and humans. In this review, we provide an exhaustive study of the literature connecting zinc and sleep, and try to evaluate which molecular mechanism is likely to be involved in this phenomenon. A better understanding should provide critical information not only about the way zinc is related to sleep but also about how sleep itself works and what its real function is

The Role of Nucleus Accumbens Core/Shell in Sleep-Wake Regulation and their Involvement in Modafinil-Induced Arousal

Background: We have previously shown that modafinil promotes wakefulness via dopamine receptor D1 and D2 receptors; however, the locus where dopamine acts has not been identified. We proposed that the nucleus accumbens (NAc) that receives the ventral tegmental area dopamine inputs play an important role not only in reward and addiction but also in sleep-wake cycle and in mediating modafinil-induced arousal. Methodology/Principal Findings: In the present study, we further explored the role of NAc in sleep-wake cycle and sleep homeostasis by ablating the NAc core and shell, respectively, and examined arousal response following modafinil administration. We found that discrete NAc core and shell lesions produced 26.5% and 17.4% increase in total wakefulness per day, respectively, with sleep fragmentation and a reduced sleep rebound after a 6-hr sleep deprivation compared to control. Finally, NAc core but not shell lesions eliminated arousal effects of modafinil. Conclusions/Significance: These results indicate that the NAc regulates sleep-wake behavior and mediates arousal effects of the midbrain dopamine system and stimulant modafinil