Is nonlinear propagation responsible for the brassiness of elephant trumpet calls?

African elephants (Loxodonta africana) produce a broad diversity of sounds ranging from infrasonic rumbles to much higher frequency trumpets. Trumpet calls are very loud voiced signals given by highly aroused elephants, and appear to be produced by a forceful expulsion of air through the trunk. Some trumpet calls have a very distinctive quality that is unique in the animal kingdom, but resemble the "brassy" sounds that can be produced with brass musical instruments such as trumpets or trombones. Brassy musical sounds are characterised by a flat spectral slope caused by the nonlinear propagation of the source wave as it travels through the long bore of the instrument. The extent of this phenomenon, which normally occurs at high intensity levels (e.g. fortissimo), depends on the fundamental frequency (F0) of the source as well as on the length of the resonating tube. Interestingly, the length of the vocal tract of the elephant (as measured from the vocal folds to the end of the trunk) approximates the critical length for shockwave formation, given the fundamental frequency and intensity of trumpet calls. We suggest that this phenomenon could explain the unique, distinctive brassy quality of elephant trumpet calls

New sol-gel formulations to increase the barrier effect of a protective coating against the corrosion of steels

Films were deposited onto AISI 430 stainless steel substrates by dip-coating technique. The aim is to reach the AISI 304L stainless steel anti-corrosion properties by a coated AISI 430 stainless steel system. Sol formulation is done from the starting precursors tetraethylorthosilicate (TEOS) and 3(trimethoxysilyl) propyl methacrylate (MAP). After the hydrolysis of these precursors, sol-gel reactions occur before the addition (or not) of a controlled quantity of cerium nitrate. The addition of the PEG (polyethylene glycol), used as plasticizer has been studied in this paper and both physical and chemical properties of the synthesized hybrid films were studied by varying PEG ratios. Based on SEM observations and mass gain measurements, the thickness of the films has been adjustable. Another parameter plays a key role: the drying step of the whole system. It has been investigated and optimized in this paper to lead to coatings with a high barrier effect. The efficiency of the anti-corrosion protection of hybrid-coated stainless steel was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) after immersion of the material in a 3.5% NaCl solution. Double-layered systems were successfully developed and a good compromise between PEG content and drying conditions has been found. Potentiodynamic polarization curves showed that the hybrid coating prepared using a TEOS/MAP/PEG yielded the best anti-corrosion performances. It acts as an efficient barrier similar to AISI 304 stainless steel used as reference, increasing the total impedance and significantly reducing the current densities

The Electrochemical Behavior of α,β′-Brass in Basic NaNO3Solutions

The electrochemical behavior of an α,β'-brass CuZn40Pb2 (CW617N) was studied in basic nitrate solutions with various basic pHs and nitrate ion concentrations. In all the chosen experimental conditions, corrosion at the open circuit potential proceeded by the galvanic coupling of the α and β' phases, leading to a surface dezincification of the β' phase. The study showed that the extent of the dezincification was affected by the presence of lead in the alloy but the pH was the major parameter. During polarization tests, a pseudo-passive or a passive stage followed by a breakdown was observed: corrosion phenomena mainly involved copper and zinc dissolution from the β' phase. At pH 11, a Cu2O/PbO layer was efficient in achieving passivity of the brass. At pH 12, a Cu(OH)2-rich surface layer was formed: it was not protective enough, and complete dissolution of the β' phase was observed leading to the removal of lead particles

Corrosion Behavior of α,β'-Brass in NaNO3 Solutions

The corrosion behavior of an α,β'-brass CuZn40Pb2 (CW617N) was studied in solutions with basic pHs and various nitrate ion concentrations. Corrosion at the open circuit potential was observed to proceed by the galvanic coupling of α and β' phases, leading to a surface dezincification of the β' phase and the evolution of the passive layer. When the alloy was polarized in the anodic domain, a pseudo-passive or a passive stage followed by a passive breakdown was observed

Dissolution Kinetics of α,β′-Brass in Basic NaNO3 Solutions

Corrosion tests at a constant anodic potential, referred to as dissolution tests, were performed to determine the dissolution kinetics of an α,β′-brass CuZn40Pb2 (CW617N) in a basic nitrate solution with and without mechanical loading. The corrosion behavior of the α,β′-brass was characterized by a two-step mechanism, with an initiation step for which the simultaneous dissolution of all the alloying elements of the β′ phase occurred only and a propagation step including at first, the afore-mentioned simultaneous dissolution process before a critical time tc and then, both simultaneous dissolution and dezincification of the β′ phase after tc. The pH and Cu concentration of the electrolyte near the brass surface were determined to be two of the major factors influencing the occurrence of the dezincification process. The dezincification of the β′ phase extended in depth by a percolation dissolution mechanism. Mechanical loading during the dissolution tests was observed to largely influence the dezincification process. It was assumed to open or close the pores present in the dezincified β′ phase, which promoted or slowed down the dezincification mechanism depending on the sign of the stress

Development of Representative Tests to Quantify the Susceptibility to Stress Corrosion Cracking of , '-Brass Used for Gas Transfer Devices

Corrosion susceptibility of an α,β'-brass CuZn40Pb2 (CW617N), used for gas transfer devices, was investigated through accelerated corrosion tests at a constant anodic potential in NaNO3 solution with basic pHs. The anodic dissolution behavior of the α,β'-brass was characterized by a two stages-mechanism, with each stage including both dezincification and simultaneous dissolution phenomena of the β' phase but with different kinetics at each stage. Compressive or tensile stresses applied on brass specimens during the accelerated tests were observed largely to influence the anodic dissolution kinetics. Stresses were assumed to open or close the pores present in the dezincified β' phase, which promoted or slowed the dezincification mechanism, including with the Zn diffusion into the solution trapped inside of the pores

New architectured hybrid sol-gel coatings for wear and corrosion protection of low-carbon steel

The replacement of expensive stainless steel in various socio-economic sectors such as mechanical or alimentary is an issue that would be possible to solve by developing a protective coating on low-carbon steel. In these applications, complex pieces are in contact with different kinds of fluids, with or without particles when functioning. Consequently, the expected coating function is to effectively protect the equipment from corrosion, abrasion and erosion. In this work thin hybrid coatings obtained by the sol-gel process have been developed for corrosion and wear protection on low-carbon steel. This innovative system is constituted of alumino-silicate epoxy based sol-gel coatings acting as barrier layers which, when loaded with zirconia particles, improve the mechanical properties. Taking into account the specificity of the carbon steel, we developed two architectured coatings displaying corrosion and wear protection. They are built by superposition of a bi-layered hybrid primer coating and a mono-layered zirconia loaded hybrid coating. Using two different zirconia contents, 30 wt.% and 40 wt.%, thin coatings of 5 and 10 μm are achieved. What is of interest is that the combination of antiwear tests and EIS to evaluate the influence of abrasive wear on anticorrosion properties has, for the first time, been demonstrated on such thin hybrid sol-gel coatings. The loss of corrosion protection of the lower zirconia loaded coating was attributed to the formation of localized defects after removal of material. On the contrary, the higher zirconia loaded coating demonstrated an interesting corrosion and wear behavior with the formation of a compacted layer at the top of the outer layer providing a barrier effect against water and ion permeation. To further characterize the protective systems, the morphology and the microstructure of the coatings were investigated by scanning electron microscopy

Spectral acoustic structure of barking in roe deer: sex age and individual related variations.

In roe deer, barking is a loud call commonly given by males and females during inter- or intraspecific interactions. The analysis of a set of 19 spectral variables computed on 560 calls revealed significant variation between sexes, individuals, and probably age classes. Discriminant analysis predicted the sex of an individual with a 93.5% probability from a small portion of the bark frequency range. Among six males, a linear combination of six variables predicted the identity of the barking individual with a 70% probability. These sexual and individual differences provide the potential for social recognition from vocalizations. These results are consistent with the hypothesis that barking in roe deer may allow remote signalling of presence, location and identity, and play an important role in the territorial system of this species

Male vocal behavior and phylogeny in deer

International audienc

Diurnal and seasonal variations of roaring activity of farmed red deer stags

International audienc