Many underwater bioacoustical recording experiments (e.g., fish sound production during courtship or agonistic encounters) are usually conducted in a controlled laboratory environment of small-sized tanks. The effects of reverberation, resonance, and tank size on the characteristics of sound recorded inside small tanks have never been fully addressed, although these factors are known to influence the recordings. In this work, 5-cycle tone bursts of 1-kHz sound were used as a test signal to investigate the sound recorded in a 170-l rectangular glass tank at various depths and distances from a transducer. The dominant frequency, sound-pressure level, and power spectrum recorded in small tanks were significantly distorted compared to the original tone bursts. Due to resonance, the dominant frequency varied with water depth, and power spectrum level of the projected frequency decreased exponentially with increased distance between the hydrophone and the sound source; however, the resonant component was nearly uniform throughout the tank. Based on the empirical findings and theoretical calculation, a working protocol is presented that minimizes distortion in fish sound recordings in small tanks. To validate this approach, sounds produced by the croaking gourami (Trichopsis vittata) during staged agonistic encounters were recorded according to the proposed protocol in an 1800-l circular tank and in a 37-l rectangular tank to compare differences in acoustic characteristics associated with tank size and recording position. The findings underscore pitfalls associated with recording fish sounds in small tanks. Herein, an empirical solution to correct these distortions is provided.

No abstract

The established technique is ideally suited for precise quantification of microanalysis of drug substances and drug products, particularly at the surface and interior of the tablet.

The double network concept, based on the fracture of sacrificial bonds, has been revolutionary toward the creation of robust soft materials. Based on the essence of double network hydrogels, macroscale, three-dimensional printed rigid sacrificial networks are embedded within silicone rubber stretchable matrices. Preferential fracture of the sacrificial network results in a ∼60 time increase in stiffness and a ∼50% increase in the work of extension compared with the neat matrix. Maximizing yield strength while maintaining multistep internal fracture occurs when the strength of the sacrificial network approaches the strength of the matrix. Upon determining the optimal sacrificial network strength, the sacrificial bond section density can be increased to maximize energy dissipation and toughening efficiencies up to ∼70% of the maximum theoretical toughness are achieved. High toughness and dissipation are achieved because topological interlocking enables significant force transmission to the sacrificial network at smaller length scales than interfacial adhesion, allowing much higher sacrificial bond density. This method is general and can be used with a variety of materials systems, without requiring strong interfacial adhesion, contrasting traditional composite systems. Demonstrating that the double network concept can be used at length scales far beyond the molecular scale will have important implications toward the development of future structural materials.

No abstract