Innervation of Gill Lateral Cells in the Bivalve Mollusc Crassostrea virginica Affects Cellular Membrane Potential and Cilia Activity

Gill lateral cells of Crassostrea virginica are innervated by the branchial nerve, which contains serotonergic and dopaminergic fibers that regulate cilia beating rate. Terminal release of serotonin or dopamine results in an increase or decrease, respectively, of cilia beating rate in lateral gill cells. In this study we used the voltage sensitive fluorescent probe DiBAC4(3) to quantify changes in gill lateral cell membrane potential in response to electrical stimulation of the branchial nerve or to applications of serotonin and dopamine, and correlate these changes to cilia beating rates. Application of serotonin to gill lateral cells caused prolonged membrane depolarization, similar to plateau potentials, while increasing cilia beating rate. Application of dopamine hyperpolarized the resting membrane while decreasing cilia beating rate. Low frequency (5 Hz) electrical stimulations of the branchial nerve, which cause terminal release of endogenous serotonin, or high frequency (20 Hz) stimulations, which cause terminal release of endogenous dopamine, had the same effects on gill lateral cell membrane potentials and cilia beating rate as the respective applications of serotonin or dopamine. The study shows that innervation of gill lateral cells by the branchial nerve affects membrane potential as well as cilia beating rate, and demonstrates a strong correlation between changes in membrane potential and regulation of cilia beating rate. The study furthers the understanding of serotonin and dopamine signaling in the innervation and regulation of gill cilia in bivalves. The study also shows that voltage sensitive fluorescent probes like DiBAC 4(3) can be successfully used as an alternative to microelectrodes to measure changes in membrane potential of ciliated gill cells and other small cells with fast moving cilia

Transmission Loss Analyses on Different Angular Distributions of Periodic Inclusions in a Porous Layer

The scope of this paper is to investigate the sound transmission loss of an acoustic package of glass wool with embedded periodic inclusions, considering the possibility to improve a standard configuration and inserting the innovative package in a practical configuration used in the aeronautic field for noise suppression. Periodic inclusions are introduced to enhance the sound transmission loss performance of the acoustic package in the mid-high range of frequencies. The main interest of the present work, with respect to the state of the art, is represented by the arrangement of the inclusions one respect to the others, then creating an inclusion pattern that improves the performance of the periodicity peak. To reach this goal, a numerical model of the package is studied, and the effect of the patterns of periodic inclusions is simulated. The pattern behavior is evaluated for eight configurations, which are different from each other for the cubic dimensions and the inclusion radii. Furthermore, an optimized configuration for aeronautical applications is designed starting from the studied acoustic package; then, the results in terms of mass and performance are discussed. Results are presented in terms of tables and graphs, which may constitute a good basis to perform preliminary design consideration that could be interesting for further generalizations

Acoustic characteristics evaluation of an innovative metamaterial obtained through 3D printing technique

The reduction of interior noise level in the transportation sector is a big problem to cope with in view to increase the comfort of passengers. For this reason a great emphasis from the research community is devoted to develop new technology which are able to satisfy the mechanical requirements with concrete benefits from the acoustic point of view. Currently, it does not exist a solution for wideband range of frequency. Indeed, porous materials are characterized by outstanding dissipation in the high frequency range but they exhibit poor performance in the low and medium frequency range, where instead resonant cavities systems have the best performances but with narrow-band sound absorption. For this reason, the design and development of new materials which offers a good acoustic absorption over a wide range of frequencies is requested. In this paper, a hybrid metamaterial is designed, by coupling resonant cavities with micro-porous material and obtained through additive manufacturing technique which enables to model complex geometries that could not be feasible with classical manufacturing. Numerical and experimental studies have been conducted on the manufactured samples of PLA, with an interesting focus on the effect of each parameter which affects the absorption properties

Acoustic metamaterial design for aeronautical purposes

Labyrinth-shape quarter wavelength tubes are numerically studied under plane wave excitation, with analytical comparison. These labyrinth resonators (LRs) are tuned at 60, 90 and 120 Hz, and their sound absorption response exhibits maximum peak at those frequencies with high fidelity and performance. These objects can absorb tonal sources at very low frequencies, with an incredibly competitive thickness, resulting in the possibility of considering them for the design of acoustic liners for an aerospace engine, but also for the automotive and naval industries. They are put together to form an acoustic metamaterial which exhibits multiple tonal peaks, demonstrating that the performance of each resonator is not affected by their coupling

THE CENTRAL NERVOUS SYSTEM REGULATION OF CILIARY ACTIVITY IN THE BIVALVE MOLLUSC MYTILUS EDULIS.

Abstract not availabl

The Role of the Visceral Ganglion in the Control of Gill Lateral Cilia of Mytilus Edulis

Abstract not availabl

Coiled quarter wavelength resonators for low-frequency sound absorption under plane wave and diffuse acoustic field excitations

To reduce their space requirement, quarter wavelength resonators are coiled up into a spiral to have the shape of a flat cylinder. The practical implementation of these resonators is tested using 3D printing, laser cutting and machining. Numerical simulations and impedance tube measurements are first compared for a normally incident plane wave excitation. This step allows to evaluate the effect of the resonator's inlet diameter, internal wall thickness, overall height as well as its constitutive material. A series of samples are then 3D printed following the identified optimal geometrical configuration. An array of resonators is tested alone and in combination with a glass wool layer under diffuse acoustic field excitation in a small reverberation chamber. The obtained results show that coiled quarter wavelength resonators can provide large sound absorption at their lowest resonance frequency and under both considered excitations, even if the largest external dimension of the resonators is only 1/18th of the targeted acoustic wavelength