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A novel active frequency selective surface (AFSS) is proposed in this communication which not only can achieve electromagnetic (EM) switching between the transmission and absorption modes but also has the capability of dynamically modulating the amplitudes for the above two modes. The designed AFSS consists of a periodic metallic structure layer and a graphene capacitor layer. The periodic metallic structure plays the role of the EM switching for the mode selection of transmission/absorption by regulating the bias states of the loaded p-i-n diodes, while the corresponding amplitudes of the transmission/absorption can be further tuned by changing the effective sheet resistance of graphene through an electrostatic field bias. An equivalent circuit model is introduced to explain the EM switching and amplitude tuning behaviors of transmission/absorption. In addition, the designed AFSS is also demonstrated to perform well under circumstances of oblique incidence and different polarizations. The AFSS prototype is fabricated and measured. In the transmission mode, the transmission loss can be tuned from −4.8 to −1.1 dB at the band of 6–7 GHz, while in the absorption mode, the average value of absorptivity can be controlled between 0.65 and 0.95 at the band of 5–8.4 GHz. The measurement results agree well with the simulation ones, which demonstrate the great performance of our AFSS.

In this communication, we propose a tunable radar absorber based on the combination of a graphene capacitor with a varactor-loaded active frequency-selective surface (FSS). The absorbing amplitude and frequency can be independently controlled by changing the effective sheet resistance of graphene and the capacitance of the varactor through different bias voltages, respectively. We fabricated the designed absorber and measured its tunable reflectivity. The measured results indicate that the absorber can tune its absorbing frequency ranging from 3.53 to 7.05 GHz under normal incidence when changing bias voltages applied to the varactors from 0.5 to 10 V. By further varying the graphene resistance through the bias voltage, the absorbing amplitude at each absorbing frequency can be dynamically modulated. In addition, it is found that the absorber achieves polarization-insensitive characteristics due to the symmetrical design of the active FSS. The physical mechanism of this absorber is discussed by providing the equivalent transmission-line (TL) model.

In this letter, a broadband polarization-independent tunable absorber is proposed based on active frequency selective surface (AFSS). The AFSS consists of periodic patterns of four-patch array with four p-i-n diodes loaded among them, and a simple bias network is designed behind the ground plane through metalized via holes, which can effectively reduce the influence on the absorbing performance. By changing the bias voltage applied on the p-i-n diodes, the reflectivity of our absorber can be dynamically adjusted from near-unity reflection to less than −10 dB absorptivity under normal incidence over a wide frequency band ranging from 8.5 to 18.2 GHz. Due to the symmetrical structure of the AFSS, our absorber still has polarization insensitivity. We fabricated this AFSS absorber sample, and its measured results agree well with the simulated ones.

In this communication, a broadband and tunable radar absorber is proposed by integrating graphene capacitor with resistive frequency-selective surfaces (RFSS). The microwave reflectivity can be dynamically controlled by changing the effective sheet resistance of graphene through an electrostatic field bias. The simulated results indicate that this structure can tune its reflectivity over a wide frequency band ranging from 2.9 to 15.9 GHz under the normal incidence, when the graphene resistance is varied from 120 to $700~\Omega $ /sq. The tuning range of the average reflectivity is from −4.6 to −15.3 dB. The physical mechanism of this tunable absorber is discussed by studying the electric field distribution and power loss density. We fabricated this absorber and measured its tunable reflectivity by applying different biasing voltages. The experimental results are in a good agreement with those of the simulation results. In addition, this absorber is also verified to have a good angular stability and polarization insensitivity, which will have broad prospects in the application of stealth technology.

Jiakun Song, Yurong Lu Emergency Department, Sandun District of Zhejiang Hospital, Hangzhou, Zhejiang, People’s Republic of ChinaCorrespondence: Yurong LuEmergency Department, Sandun District of Zhejiang Hospital, 1229 Gudun Road, Xihu District, Hangzhou, Zhejiang 310030, People’s Republic of ChinaTel +86-137-0581-4277Email luyurong120@163.comObjective: To identify rapid and accurate early diagnostic indicators for intra-abdominal infection (IAI) after general surgery.Methods: We conducted a retrospective analysis of 3,810 general surgical patients in our hospital from August 2017 to July 2018. The predictive value of PCT, CRP, TNFα, and IL6 on postoperative days (PODs) 1 and 3 and composite indicators for complicated IAIs among surgical patients was clarified.Results: There were 271 patients in the infected group and 614 patients in the uninfected group using IAI diagnostic criteria in this study. CRP, PCT, TNFα, and IL6 in the infected group were significantly higher than the uninfected group on POD1 and POD3. In the infected group, the composition of the four indicators on POD1 (AUC 0.819) and POD3 (AUC 0.848) showed higher predictive efficiency than the individual indicators (AUC 0.670– 0.805).Conclusion: The composite of CRP, PCT, TNFα, and IL6 can be used as a predictor of postoperative abdominal infectious complications with high sensitivity and specificity on POD1 and POD3, which can provide a basis for early diagnosis of postoperative abdominal infectious complications.Keywords: procalcitonin, C-reactive protein, TNFα, IL6, intra-abdominal infection

In this paper, leveraging the resonant phase and the geometry phase simultaneously, we demonstrated a low scattering lens antenna, which can work at both transmission and reflection mode. Different from the traditional microwave lens which only realizes wavefront shaping in half-space, the proposed metasurface lens not only squeezes the transmitted divergent beam to improve the gain of the conventional circular-polarized antenna, but also scatters the electromagnetic wave to maintain a low reflection property in broadband. The proposed lens antenna working in full space may provide a new approach for an integrated communication system.

In this article, an electrically controlled resistive layer (ECRL) is proposed to construct tunable absorbers. This ECRL is composed of VO2 film and resistive layer without lithography pattern. The effective resistance of ECRL is numerically verified to be tuned from 18 to 300 Ω/sq as the VO2 conductivity is changed based on electro-thermally induced insulator-to-metal transition. With such a large tuning range of the effective resistance, the ECRL is utilized to realize a planar tunable bidirectional absorber with absorption efficiency dynamically tuned between 98 and 18% through controlling the conductivity of VO2. In addition, we demonstrate that the ECRL is also suitable for the design of non-planar tunable absorber. It is still found that the ECRL-based tunable absorbers have the wide angle and polarization-insensitive absorbing properties. These results may be of great interest for tunable absorbing, detecting, smart window, and thermo-solar cell applications.

In this communication, we propose a method to achieve high-efficiency transmission and wideband scattering reduction at two distinctive frequency bands by combining frequency-selective surface (FSS) and electromagnetic bandgap (EBG) surface. Such FSS-EBG surface is composed of two-layered metallic patterns. The bottom FSS layer works as a filter for allowing in-band signal to pass and reflecting out-of-band signal, while the top EBG layer adopts 0 and $\pi $ reflection phase cells with a chessboard distribution to reduce the backward scattering wave. As a proof-of-concept demonstration, the planar and cylindrical surfaces are, respectively, designed to verify such two functionalities. Our FSS-EBG surface can make the antenna signal transmit at S-band with small insertion loss and simultaneously provide wideband low-scattering property at X–Ku band, which is suitable to be used as the stealth antenna radome. In addition, the possibility of integrating polarization conversion function into the passing band is numerically demonstrated.

Considerable attentions have been focused on the realization of carpet cloaks in the past decade. Most of the current carpet cloaks can perform only one electromagnetic (EM) shape for concealing inside objects, and dynamical control of arbitrary EM virtual shapes remains a significant challenge. Here, a desirable method is proposed to construct a reconfigurable carpet cloak using tunable metasurface technology. By controlling the active elements loaded on the metasurface, the surface phase distribution can be dynamically changed to make the cloak generate the predesigned scattering field. This reconfigurable metasurface cloak is experimentally realized at the microwave frequency, which demonstrates that it can not only reduce unwanted scattering for imitating the reflection of a flat metallic plane, but also mimic other different EM virtual shapes by reconfiguring the phase distribution. To the best of our knowledge, this is the first carpet cloak that achieves dynamical illusions by switching the EM shap...

In this article, a dual-band wide-angle metamaterial perfect absorber is proposed to achieve absorption at the wavelength where laser radar operates. It is composed of gold ring array and a Helmholtz resonance cavity spaced by a Si dielectric layer. Numerical simulation results reveal that the designed absorber displays two absorption peaks at the target wavelength of 10.6 μm and 1.064 μm with the large frequency ratio and near-unity absorptivity under the normal incidence. The wide-angle absorbing property and the polarization-insensitive feature are also demonstrated. Localized surface plasmons resonance and Helmholtz resonance are introduced to analyze and interpret the absorbing mechanism. The designed perfect absorber can be developed for potential applications in infrared stealth field.

As an adaptation to their environment, fishes and some aquatic amphibians have developed a hydrodynamic receptor system, the lateral line mechanosensory system, which enables them to detect minute water motion, and provide information that can apply for feeding, avoidance, schooling, navigation, and intraspecific communication. This system consists of individual sensory receptors, neuromasts, that either lie within lateral line canals along the body (canal neuromasts, CNM) or occur freestanding on the surface of the skin (superficial neuromasts, SNM). These CNM and SNM act as acceleration (higher frequency response, 60–120 Hz) or velocity receptors (lower frequency response, 20–60 Hz), respectively, which can also provide the signal location and fluidic direction to the central nervous system (CNS). The neuromast consists of discrete clusters of sensory hair cells, support cells and mantle cells. On the apical of hair cell, a bundle of several stereocilia and one kinocilium that protrudes from of the hair cell into a gelatinous cupula. The cupula covers entire neuromast apical and connects the ciliary bundles with surrounding water. Deflection of the cupula induces the directional movement of the hair bundles that results in opening or closing of the transduction channels on the kinocilium, affecting the release of neurotransmitter that conveys the hair cell’s relative excitation to the afferent neuron (in the lateral line ganglion), then, travels to the target areas in the CNS. Between CNM and SNM, there are several morphological differences such as diameter of sensory epithelium, number of hair cells, orientation of axis, and peripheral innervation pattern. They also demonstrate with different biomechanical properties in detecting different types of hydrodynamic signals and play different roles in responding to the various water motion patterns (including micro fluid). All the peripheral information that is integrated at different levels of the CNS centers before guiding the proper behavior of fish. The CNM appears to provide information about fine spatial details that lead to the ability of fish to segregate the fine turbulence signal in near field while towards discrete sources or under rapidly changing water motions surrounding. SNM appears to provide peripheral spatial information of large-scale stimuli, such as rheotaxis to slow motion currents. As a delicate hydrodynamic detector system, a well functioned lateral line system that only consists of two types of peripheral receptor plus their architectural design of arrangement and canal pattern modifications that is far advanced than, up to date, any of the man-made underwater detector in the world. Even more, the system provides a high efficient computing model that is from the peripheral innervation pattern designed for major collection of temporal and spatial hydrodynamic information, the integration of data processing structure, and to the action assignment in the CNS. The mechanosensory lateral line system in fish is starting attracted by research approaches in biomimetic, mathematics, physical and computing sciences, in addition to the biology and neurosciences. The participating of integrative study on the lateral line system, that is not only help developing of new applications but also enhanced biological understand of the system. The biologists have been speculated the function of the CNM, the co-relationship of the canal morphology and fish habits over decades. Until recently, the mathematic model and the device of artificial lateral line receptor established by Klein and Bleckmann (2015), demonstrate that “it is possible to change the transfer function of an artificial line by changing its canal shape, dimensions and pore pattern”. Moreover, their research evident indicate that the lateral line is able to “detect and localize vibrating sources, detect and monitor vortices, localize upstream objects, discriminate between upsteam objects (size and shape), estimate bulk flow velocity in turbulent environment, and measure small amounts of liquid” (Klein, 2016 personal communication). This review paper intends to introduce the fish mechanosensory lateral line system from several aspects that include the studies of morphological characteristics, biological origin of the system, development of the pattern formation, functional properties, behavioral neurophysiology and neural control mechanisms, finally, the biomimetic application and perspectives. We combine both of our knowledge in lateral line and recent research results in the non-canal lateral line system with broad collections of the references in the lateral line studies, especially, the new publications. We hope to provide information to readers across different disciplines, not only for theoretical consideration but also for the application in biomimetic, civic engineering, and the aquatic animal protection /biodiversity program.

Altered behaviors have been reported in many marine fish following exposure to high CO2 concentrations. However, the mechanistic link between elevated CO2 and activation of brain regions in fish is unknown. Herein, we examined the relative quantification and location of c-Fos expression in marine medaka following acute (360 min) and short-term (7 d) exposure to CO2-enriched water (1000 ppm and 1800 ppm CO2). In the control and two treatment groups, pH was stable at 8.21, 7.92 and 7.64, respectively. After acute exposure to seawater acidified by enrichment with CO2, there was a clear upregulation of c-Fos protein in the medaka brain (P

Different from regular bandgap narrowing for better sunlight absorption, a series of nanostructure-induced wedge-shaped colored TiO2 array photoelectrodes exhibited full solar spectrum light harvesting and enhanced performances exemplified by photoelectrochemical (PEC) degradation of Ni(II)–EDTA. Finite element method (FEM) simulation confirmed the influence of the nanostructure towards light absorption in UV, visible, and near-infrared (NIR) regions.

We propose a high performance N-structure type-II superlattice (T2SL) photodetector for long wavelength infrared (LWIR) applications. Theoretical study on the electrical and optical properties of the N-structure T2SL LWIR detector with different carrier concentration and different thicknesses in the p-region is carried out. We obtain the relationship of material parameters and performance parameters. With the increasing of the thickness of p-region, quantum efficiency ( QE ) gradually improves. In contrast, zero-bias resistance area ( R 0 A ) product decreases. QE will significantly decreases when the carrier concentration of p-region is too high, while R 0 A first increases, then decreases. The results show that the performance of the N-structure T2SL LWIR detector can be state of the art by optimizing the carrier concentration and material thickness during the structure growth and device fabrication.

In this paper, a broadband and tunable radar cross section (RCS) reduction structure is proposed by using the hybrid physical mechanism that is based on high-order reflections and Salisbury-type absorption. Our design combines the high-index grating structure with a traditional Salisbury screen in which the lossy sheet is made of a graphene structure. When it is illuminated by a plane wave with normal incidence, the Salisbury screen can absorb the incoming wave, and the introducing high-index grating structure could further reduce the backward scattering wave by generating high-order reflection beams, which broadens the RCS reduction bandwidth. In addition, the RCS reduction level can be dynamically controlled by tuning the surface resistance of the graphene layer. Simulated results show that the proposed structure can realize tunable RCS reduction between 4.1 and 18 GHz under normal incidence with different graphene resistances. Experimental results are in accordance with those of the simulation results. In addition, the scattering field distributions and the plots of surface power loss density have been illustrated to analyze the RCS-reduction mechanism of our structure.

Fish detect water motion with their mechanosensory lateral line. The basic functional unit of the lateral line is the neuromast. In most fish species, neuromasts are located in lateral line canals (canal neuromasts) or on the skin (superficial neuromasts). In this paper, we describe the lateral line system of the pufferfish

The lateral line found in some amphibians and fishes has two distinctive classes of sensory organs: mechanoreceptors (neuromasts) and electroreceptors (ampullary organs). Hair cells in neuromasts can be damaged by aminoglycoside antibiotics and they will regenerate rapidly afterward. Aminoglycoside sensitivity and the capacity for regeneration have not been investigated in ampullary organs. We treated Siberian sturgeon (Acipenser baerii) larvae with neomycin and observed loss and regeneration of sensory hair cells in both organs by labeling with DASPEI and scanning electron microscopy (SEM). The numbers of sensory hair cells in both organs were reduced to the lowest levels at 6 hours posttreatment (hpt). New sensory hair cells began to appear at 12 hpt and were regenerated completely in 7 days. To reveal the possible mechanism for ampullary hair cell regeneration, we analyzed cell proliferation and the expression of neural placodal gene eya1 during regeneration. Both cell proliferation and eya1 expression were concentrated in peripheral mantle cells and both increased to the highest level at 12 hpt, which is consistent with the time course for regeneration of the ampullary hair cells. Furthermore, we used Texas Red-conjugated gentamicin in an uptake assay following pretreatment with a cation channel blocker (amiloride) and found that entry of the antibiotic was suppressed in both organs. Together, our results indicate that ampullary hair cells in Siberian sturgeon larvae can be damaged by neomycin exposure and they can regenerate rapidly. We suggest that the mechanisms for aminoglycoside uptake and hair cell regeneration are conserved for mechanoreceptors and electroreceptors. J. Comp. Neurol. 524:1443-1456, 2016. © 2015 Wiley Periodicals, Inc.

We propose a novel metamaterial structure to realize dispersionless slow light based on plasmon-induced transparency (PIT) at optical frequency. Simply by breaking the symmetry of the metamaterial structure, two electric excitation coupling to the magnetic resonance (EEMR) modes generate and interplay with each other resulting the formation of the PIT resonance. Due to the hybridization of the two EEMR modes, an ultrabroad flat-band as large as 15 THz with average group index of $\sim 5$ is obtained. The corresponding normalized delay-bandwidth product is 0.475, which indicates the prominent feature in light slowing down without distortion. The proposed metamaterial structure is promising for practical information storage, optical memory, and optical buffers design.

Fish detect water motions with their mechanosensory lateral line. The basic functional unit of the lateral line is the neuromast. In most fish species neuromasts are located in lateral line canals (canal neuromasts) or on the skin (superficial neuromasts). In this paper we describe the lateral line system of pufferfish, Takifugu obscurus. If threatened, this fish inflates its body by sucking water into the esophagus. Pufferfish lack a canal system but have neuromasts located directly on the skin or in open grooves. Each groove houses Tall, Medium, and Short Neuromasts, based on the height of their pedestal. One or more Medium neuromasts were always located between two Tall neuromasts, and the Short neuromasts were scattered between them. Tall neuromasts showed phasic responses to water jets, similar to the canal neuromasts of other fish species. In contrast, the Medium and Short neuromasts showed tonic responses to water jets. The response properties of nerve fibers that innervated the latter two types of neuromasts were similar to the response properties of the superficial neuromasts found in other fish species. Our results suggest that each groove of a pufferfish has two functional groups of neuromasts. This may allow pufferfish to extract spatial and temporal hydrodynamic information, despite the changes in body shape that occur during and after inflation. The short neuromasts at the bottom of a groove most likely supplement the medium neuromasts when the body is maximally inflated.

We propose a planar metamaterial design to realize active manipulation of plasmon-induced transparency. Under periodic boundary condition, a surface plasmon polaritons mode is excited by a plane wave with momentum conservation at oblique incidence. Due to the destructive interference between the surface plasmon polaritons mode and induction-capacitance resonance mode, an approximate 100% transparency window is produced at large incident angles. Simply by varying the incident angle, the plasmon-induced transparency features can be dynamically tuned. At the incident angle of 70°, a sharp transparency window with a bandwidth of 30 nm is obtained at 1.71 μm. The corresponding quality factor and group index are 58 and 410, respectively, which is promising for efficient plasmonic sensing, optical switching, and slow-light devices design.

Recently, phase cancellation metasurface has caused much attention due to its great capability of realizing radar cross section (RCS) reduction. However, owing to the intrinsic resonance property of the meta-atom, it is still challenging to expand the RCS reduction bandwidth. Here, we present a novel strategy to design ultra-broadband low-scattering metasurface by using the mixed meta-atoms combined with the evolutionary algorithm. The mixed meta-atoms are composed of single-layer or double-layer reflected elements, and the six different unit configurations are adopted to generate various reflection phases over a wide band. The planar array theory combined with particle swarm optimization (PSO) algorithm is employed to obtain the optimal mixed meta-atoms and their arrangement. The proposed low-scattering metasurface can achieve more than 10 dB RCS reduction between 5 and 18 GHz with a fractional bandwidth of 113% under normal incidence for both polarizations. The experimental results agree well with the simulated ones, and its bandwidth of the 10 dB RCS reduction reaches about 105.3%. In addition, our metasurface is still demonstrated to have the wide-angle stability for low-scattering property. The proposed design provides a feasible way to achieve ultra-broadband RCS reduction, which may find potential applications in concealing fields

In this paper, a broadband low-scattering metasurface is proposed by using a combination of phase cancellation and absorption mechanisms. The metasurface is composed of two structural layers. One layer adopts the geometric phase cell that can obtain a different reflection phase by changing its orientation. Through the random phase distribution design, electromagnetic diffusion can be realized to reduce the backward scattering energy. The other layer is made of a resistive frequency selective surface (RFSS) that can absorb the incident wave by converting it into Ohmic loss. The above two physical mechanisms respectively play the great roles at two distinct frequency bands, and finally make our metasurface achieve the RCS reduction over a wide frequency band ranging from 13 to 31.5 GHz. Both simulation and experimental results are in good agreement, which fully demonstrates our design method. The analysis of the scattering patterns, electric-field distribution and power loss density are given to explain the hybrid RCS-reduction mechanism of our metasurface.

Due to the strong capability to control electromagnetic (EM) wave, metasurfaces have garnered considerable interest and brought in many intriguing EM functional devices. However, most of such devices can only work in either transmitted or reflected mode, and it is still very challenging to achieve a simultaneous control of reflection and transmission in one device. Here, we present a cascaded metasurface which integrates the resonant and geometrical phase cells, to manipulate the transmitted and reflected wave independently. By specific design of phase distribution, the reflected and transmitted wavefront can be respectively reshaped on the shared aperture at two different frequency bands. As a proof of concept, a bidirectional beam deflector is realized by our metasurface and experimentally demonstrated at the microwave region. Both simulated and experimental results show that the transmitted and reflected beams can be simultaneously deflected to the predesigned angles. Furthermore, this metasurface exhibits isotropic EM responses under the different linear polarized wave in the reflected mode, while behaves anisotropic EM responses under the different circular polarized waves in the transmitted mode. Our approach provides a simple way to realize full-space EM manipulation, which could be developed for potential applications in mutlifunctional devices and integrated systems.

Ocean acidification is predicted to affect a wide diversity of marine organisms. However, no studies have reported the effects of ocean acidification on Indian Ocean fish. We have used the Indian Ocean medaka (Oryzias melastigma) as a model species for a marine fish that lives in coastal waters. We investigated the impact of ocean acidification on the embryonic development and the stereotyped escape behavior (mediated by the Mauthner cell) in newly hatched larvae. Newly fertilized eggs of medaka were reared in seawater at three different partial pressures of carbon dioxide (pCO2): control at 450 μatm, moderate at 1160 μatm, and high at 1783 μatm. Hatch rates, embryonic duration, and larval malformation rates were compared and were not significantly different between the treatments and the control. In the high pCO2 group, however, the yolks of larvae were significantly smaller than in the control group, and the newly hatched larvae were significantly longer than the larvae in the control. In the moderate pCO2 group, the eye distance decreased significantly. No significantly negative growth effects were observed in the larvae when exposed to pCO2 levels that are predicted as a result of ocean acidification in the next 100–200 years. Larvae reared under control conditions readily produced C-start escape behavior to mechanosensory stimuli; however, in the moderate and high pCO2 experimental groups, the probabilities of C-start were significantly lower than those of the control group. Therefore, the sensory integration needed for the C-start escape behavior appears to be vulnerable to ocean acidification. Altered behavior in marine larval fish, particularly behaviors involved in escape from predation, could have potentially negative implications to fish populations, and, further, to the marine ecosystems at the levels of CO2 projected for the future.

Light and scanning electron microscopy (SEM) were used to study the epidermal lateral line system of the Siberian sturgeon (Acipenser baerii Brandt, 1869). This system consists of mechanoreceptive neuromasts, ampullae and the electroreceptive organ. The neuromasts are located in 5 pairs of cephalic and 1 pair of trunk canals and superficially in the middle and posterior pit lines that lie dorsomedially along the top of the skull immediately adjacent to the otic ampullae field. Both canal neuromasts and pit organ superficial neuromasts have opposite polarized hair cells that are parallel along the axis of the canal and pit line, respectively. However, they differ in both size and shape and in the density and length of the hair bundles. The ampullae are confined on the head, adjacent to the neuromast lines. The morphological structure of the ampullae in the Siberian sturgeon is similar to the ampullae in elasmobranchs and other primitive fish. Nevertheless, it has a relatively large mucus-filled ampulla, and a shorter and narrower canal leading to a small opening to the outer epidermal surface. We also present new information concerning the peripheral innervation of lateral line receptors in sturgeons. The receptors of the lateral line system are innervated by 2 pairs of cranial nerves: anterior and posterior lateral line nerves. The peripheral processes of the anterior lateral line nerve form superficial ophthalmic, buccal, otic and anteroventral rami. The peripheral processes of the posterior lateral line nerve form middle, supratemporal and lateral rami.

The electro-receptive lateral line system appeared early in the evolutionary history of fish. Sturgeons, members of the primitive Chondrostei group, are known for their electroreceptors (ampullae of Lorenzini) on the head, which are thought to be sensitive to weak electric fields in aquatic environments and involved in feeding, mating and migration. Here, we report the results of a set of behavioral and electrophysiological experiments designed to determine the function and characteristics of the electrosense in cultured sturgeons. The results showed Siberian sturgeon (Acipenser baerii Brandt, 1869) feeding striking at bio-electric fields produced by living feed-fish enclosed in a gel chamber and at the corrosion field produced by metal rods. With an electric stimulus that mimics the bio-electric fields produced by living prey, the relative discharge rate of electrosensory neurons in the dorsal octavolateralis nucleus (DON) was modulated by and phase-locked to sinusoidal stimulus and some units showed selectivity for dipolar direction in white sturgeon (Acipenser transmontanus Richardson, 1836). This is the first study to provide the empirical evidence correlating with electrosensory behaviors and electrophysiological responses in cultured sturgeons, and suggesting that electrosense does play an innate role in feeding behavior of sturgeon. We believe this will have important implications for protecting sturgeons in the wild.

The passive electrosense is a primitive sensory modality in the Chondrostei, which include sturgeon and paddlefish. Using electroreceptors, these fish detect the weak electric fields from other animals or geoelectric sources, and use this information for prey detection or other behaviors. The primary afferent fibers innervating the electroreceptors project to a single hindbrain target called the dorsal octavolateral nucleus (DON), where the electrosensory information is first processed. Here, we investigated the electrophysiological properties of DON neurons.Extracellular recording was used to investigate the response properties of DON neurons to dipole electric fields with different amplitudes and frequencies in the white sturgeon, Acipenser transmontanus.The DON neurons showed regular spontaneous activity and could be classified into two types: neurons with a low spontaneous rate (10 Hz) and those with a high spontaneous rate (10 Hz). In response to sinusoidal electric field stimuli, DON neurons showed sinusoidally-modulated and phase-locked firing. In addition, neurons showed opposite phase responses corresponding to the different directions of the dipole.The response properties of DON neurons match the electrosensory biological function in sturgeon, as they match the characteristics of the electric fields of its prey.

This article presents a novel way of greatly enhancing the electrical and thermal stability of copper fiber (CuF)-filled acrylonitrile–butadiene–styrene (ABS) composites via the incorporation of small amount of tin–lead (Sn–Pb) alloy. It was observed that many fibers are soldered together by Sn–Pb, and a continuous CuF/Sn–Pb network is formed throughout the ABS matrix. As a result, the percolation concentration of ABS/CuF composite containing 1 vol% Sn–Pb is lower than for ABS/CuF composite, and the addition of Sn–Pb to the ABS composites containing 5 vol% CuF leads to a further decrease of electrical resistivity compared to ABS/CuF composites with corresponding filler contents. Furthermore, the electrical resistivity of ABS/CuF/Sn–Pb composite shows no temperature dependence, and remains constant during the thermal post-treatment.

Recently, considerable attention has been focused on orbital angular momentum (OAM) vortex wave, owing to its prospect of increasing communication capacity. Here, a single-layer metasurface is proposed to realize vortex beams with different OAM modes and polarizations carried at two distinctive bands. Both the resonant and geometric (Pancharatnam-Berry) phase cells are adopted to construct this metasurface for generating the desired phase profile, and each type of phase modulation cell can independently control the vortex beam at different frequencies. When a linearly-polarized wave is incident onto our metasurface, the resonant phase cells with spiral phase distribution can achieve OAM beam with topological charge of + 1 at 5.2 GHz. And under illumination of left-handed circular polarized (LHCP) wave, the rotated geometric phase cells assist the metasurface to generate the deflected OAM beam with topological charge of + 2 at 10.5~12 GHz. Both simulated and experimental results demonstrate good performance of the proposed single-layer metasurface at the above two frequency bands.

The hearing abilities of three age-groups (which correspond to size-classes) of walleye pollock Theragra chalcogramma were determined from auditory evoked potentials. Walleye pollock had the best hearing sensitivity from 100 to 200 Hz, with thresholds around 75 dB re: 1 μPa. Hearing sensitivity decreased with increasing frequency up to 450 Hz. There was no significant difference in hearing sensitivity between the age-groups, although there was a significant interaction between frequency and age as well as a trend in which the older fish had slightly lower mean thresholds. At the same time, there was a substantial increase in the size of the saccular otolith and associated sensory epithelia of the inner ear, suggesting that a large increase in ear size does not lead to a large change in hearing sensitivity. In addition, there was an effect of water temperature on the hearing thresholds at 350 Hz, whereby each degree of temperature (°C) increase resulted in an 8.3-dB decrease in hearing threshold. ...

The marine marbled rockfish Sebastiscus marmoratus is dependent on kelp beds and rocks for survival and reproduction. We found that sound production and hearing sensitivity in S. marmoratus are closely matched in the frequency domain. We also found that the juvenile rockfish prefers the habitat of the larger macroalgae Sargassum horueri rather than the habitat containing the smaller algae Ulva pertusa where the adult rockfish prefers to live. Our underwater noise recording data from these two habitats indicate that their spectra of the background noise have different values. The results suggest that the acoustic cues may be critical for pelagic larvae when selecting the preferential habitat in which to settle.

This study investigated the effects on rainbow trout (Oncorhynchus mykiss) of exposure to high-intensity, low-frequency sonar using an element of the standard Surveillance Towed Array Sensor System Low Frequency Active (LFA) sonar source array. Effects of the LFA sonar on hearing were tested using auditory brainstem responses. Effects were also examined on inner ear morphology using scanning electron microscopy and on nonauditory tissues using general pathology and histopathology. Animals were exposed to a maximum received rms sound pressure level of 193 dB re 1 microPa(2) for 324 or 648 s, an exposure that is far in excess of any exposure a fish would normally encounter in the wild. The most significant effect was a 20-dB auditory threshold shift at 400 Hz. However, the results varied with different groups of trout, suggesting developmental and/or genetic impacts on how sound exposure affects hearing. There was no fish mortality during or after exposure. Sensory tissue of the inner ears did not show morphological damage even several days post-sound exposure. Similarly, gross- and histopathology observations demonstrated no effects on nonauditory tissues.

The marine marbled rockfish Sebastiscus marmoratus is dependent on kelp beds and rocks for survival and reproduction. We found that sound production and hearing sensitivity in S. marmoratus are closely matched in the frequency domain. We also found that the juvenile rockfish prefers the habitat of the larger macroalgae Sargassum horueri rather than the habitat containing the smaller algae Ulva pertusa where the adult rockfish prefers to live. Our underwater noise recording data from these two habitats indicate that their spectra of the background noise have different values. The results suggest that the acoustic cues may be critical for pelagic larvae when selecting the preferential habitat in which to settle.

High power GaSb based type-I GaInAsSb/AlGaAsSb three quantum wells laser diodes emitting at 2.4 μm were optimized and fabricated. The laser wafer was grown with solid source Molecular Beam Epitaxy System. With optimizations of the epitaxial structure design and the ohmic contact, the operation voltage and the internal loss decreased; the internal quantum efficiency and output power increased. The internal quantum efficiency was determined about 80.1% and the internal loss was 12 cm -1 by measuring laser diodes with different cavity lengths. An uncoated 2-mm-long laser diode with 90-μm-wide aperture exhibited a threshold current density of 222 A/cm 2 (74 A/cm 2 per quantum well), a continuous wave output power of 232 mW and a quasi-continuous wave (1 kHz, 10 μs) output power of 1 W at room temperature.

We present a hybrid waveguide-magnetic resonance system with split ring resonators (SRRs) periodically arranged on top of a waveguide layer. Due to the destructive interference between the electric coupling to the magnetic resonance mode generated in the SRRs and the TE/TM waveguide modes supported by the waveguide layer, double plasmon-induced transparency is obtained at the infrared wavelength. Furthermore, the PIT resonance can be dynamically tuned by the incident angle. An ultranarrow PIT window with an FWHM of 7 nm is observed at the wavelength of 1.448 μm. The group index at the narrow PIT window can reach up to 100. We also demonstrate that the refractive index sensitivity and the figure of merit value can reach up to 640 nm/RIU and 64 in the sensing range, respectively. The proposed hybrid waveguide-magnetic resonance system with a high-quality factor PIT window is promising for efficient optical sensing, optical switching, and slow-light device design.

The ears of five large bluefin tuna Thunnus thynnus were examined by light and scanning electron microscopy (SEM). The gross structure of the ear is similar to that in other fishes. The ears, however, appear to be held more rigidly in place than in other species through the presence of an extensive connective tissue between the membranous ear and the surrounding bone. Moreover, unlike other fishes, the semicircular canals and otolithic end organs have thick cartilaginous walls and there is a dense matrix surrounding the otoliths rather than a more watery fluid found in other species. SEM revealed that the saccular epithelium has a 'standard' hair cell orientation pattern. The hair cell orientation patterns in the lagena and utricle resemble those found in most other fishes. Ciliary bundle density and length vary in different epithelial regions and each ear had >2 x 10 6 sensory cells. The morphological results support the hypothesis that bluefin tuna probably do not detect sounds to much over 1000 Hz (if that high) and that only very loud anthropogenic sounds have the potential to affect hearing in this species.

Many species of odontocete cetaceans (toothed whales) use high-frequency clicks (60–170 kHz) to identify objects in their environment, including potential prey. Behavioral studies have shown that American shad, Alosa sapidissima, can detect ultrasonic signals similar to those of odontocetes that are potentially their predators. American shad also show strong escape behavior in response to ultrasonic pulses between 70 and 110 kHz and can determine the location of the sound source at least in the horizontal plane. The present study examines physiological aspects of ultrasound detection by American shad and provides the first insights into the neural encoding of ultrasound signals in any nonmammalian vertebrate. The recordings were obtained by penetration through the cerebellar surface. All but two units responded exclusively to ultrasound. Ultrasound-sensitive units did not phase-couple to any stimulus frequency. Some units resembled the response of constant latency neurons found in the ventral nucleus of the lateral lemniscus of bats. We suggest that ultrasonic and sonic signals are processed along different pathways in Alosa. The ultrasonic pathway in Alosa appears to be a feature detector that is likely to be adapted (e.g., frequency, intensity) to odontocete echolocation signals.

The lateral line found in some amphibians and fishes has two distinctive classes of sensory organs: mechanoreceptors (neuromasts) and electroreceptors (ampullary organs). Hair cells in neuromasts can be damaged by aminoglycoside antibiotics and they will regenerate rapidly afterward. Aminoglycoside sensitivity and the capacity for regeneration have not been investigated in ampullary organs. We treated Siberian sturgeon (Acipenser baerii) larvae with neomycin and observed loss and regeneration of sensory hair cells in both organs by labeling with DASPEI and scanning electron microscopy (SEM). The numbers of sensory hair cells in both organs were reduced to the lowest levels at 6 hours posttreatment (hpt). New sensory hair cells began to appear at 12 hpt and were regenerated completely in 7 days. To reveal the possible mechanism for ampullary hair cell regeneration, we analyzed cell proliferation and the expression of neural placodal gene eya1 during regeneration. Both cell proliferation and eya1 expression were concentrated in peripheral mantle cells and both increased to the highest level at 12 hpt, which is consistent with the time course for regeneration of the ampullary hair cells. Furthermore, we used Texas Red-conjugated gentamicin in an uptake assay following pretreatment with a cation channel blocker (amiloride) and found that entry of the antibiotic was suppressed in both organs. Together, our results indicate that ampullary hair cells in Siberian sturgeon larvae can be damaged by neomycin exposure and they can regenerate rapidly. We suggest that the mechanisms for aminoglycoside uptake and hair cell regeneration are conserved for mechanoreceptors and electroreceptors. J. Comp. Neurol. 524:1443-1456, 2016. © 2015 Wiley Periodicals, Inc.

Cephalopods (octopus, squid and cuttlefish) are some of the most intriguing molluscs, and they represent economically important commercial marine species for fisheries. Previous studies have shown that cephalopods are sensitive to underwater particle motion, especially at low frequencies in the order of 10 Hz. The present paper deals with quantitative modeling of the statocyst system in three cephalopod species: Octopus vulgaris, Sepia officinalis and Loligo vulgaris. The octopus's macula/statolith organ was modeled as a 2nd-order dynamic oscillator using parameter values estimated from scanning electron micrograph images. The modeling results agree reasonably well with experimental data (acceleration threshold) in the three cephalopod species. Insights made from quantitative modeling and simulating the particle motion sensing mechanism of cephalopods elucidated their underwater particle motion detection capabilities. Sensitivity to emerging environmental issues, such as low frequency noise caused by near-shore wind farms and increasing levels of carbon dioxide in the ocean, and sensitivity to sounds produced by impending landslides were investigated in octopus using the model.