Comparison of FFP predictions with measurements of a low-frequency signal propagated in the atmosphere

An experimental study of low-frequency propagation over a distance of 770 m was previously reported (J. Acoust. Soc. Am. Suppl. 1 86, S120 (1989)). For that study, sound speed profiles were reconstructed entirely from surface-layer micrometeorological data. When the acoustic data were compared with theoretical predictions from a fast field program (FFP), it was found that the FFP underpredicted sound levels measured in a shadow zone. Here, the effect on the predictions of including meteorological data for heights greater than the surface layer, i.e., wind profiles measured by a Doppler sodar, is discussed. Vertical structure of turbulence is simulated by stochastically perturbing the mean profiles, and the agreement between the acoustic data and FFP predictions is improved

Characterisation and optimisation of PECVD SiNx as an antireflection coating and passivation layer for silicon solar cells

In this work, we investigate how the film properties of silicon nitride (SiNx) depend on its deposition conditions when formed by plasma enhanced chemical vapour deposition (PECVD). The examination is conducted with a Roth & Rau AK400 PECVD reactor, where the varied parameters are deposition temperature, pressure, gas flow ratio, total gas flow, microwave plasma power and radio-frequency bias voltage. The films are evaluated by Fourier transform infrared spectroscopy to determine structural properties, by spectrophotometry to determine optical properties, and by capacitance–voltage and photoconductance measurements to determine electronic properties. After reporting on the dependence of SiNx properties on deposition parameters, we determine the optimized deposition conditions that attain low absorption and low recombination. On the basis of SiNx growth models proposed in the literature and of our experimental results, we discuss how each process parameter affects the deposition rate and chemical bond density. We then focus on the effective surface recombination velocity S eff, which is of primary importance to solar cells. We find that for the SiNx prepared in this work, 1) S eff does not correlate universally with the bulk structural and optical properties such as chemical bond densities and refractive index, and 2) S eff depends primarily on the defect density at the SiNx-Si interface rather than the insulator charge. Finally, employing the optimized deposition condition, we achieve a relatively constant and low S eff,UL on low-resistivity (≤1.1 Ωcm) p- and n-type c-Si substrates over a broad range of n = 1.85–4.07. The results of this study demonstrate that the trade-off between optical transmission and surface passivation can be circumvented. Although we focus on photovoltaic applications, this study may be useful for any device for which it is desirable to maximize light transmission and surface passivation.This work was supported by an Australian Research Council Linkage between The Australian National University and Braggone Oy under Grant LP0989593

A new Devonian fish (Crossopterygii: Rhipidistia) considered in relation of the origin of the Amphibia

Hyneria lindae, gen. et sp. nov., is a large rhizodontid rhipidistian fish from the Upper Devonian (Oswayo Formation) of Pennsylvania. It shows a remarkable similarity to the intermediate stages that must have preceded the first true Amphibia. The similarity is due to the parallel evolution of rhizodontid Rhipidistia and the Amphibia from a common stock in the Middle or early Late Devonian

New evidence on the evolution of the paired fins of Rhipidistia and the origin of the tetrapod limb, with description of a new genus of Osteolepidae

A specimen of Sterropterygion brandei, gen. et sp. nov., a rhipidistian from the Upper Devonian of Pennsylvania, shows for the first time the detailed internal structure of the pectoral and pelvic fins and girdles in a member of the Family Osteolepidae. The structure conforms to the general pattern once thought to be directly antecedent to that of tetrapods but which now must also be considered an ancient feature of rhipidistian fishes. It is contended that the known Rhipidistia could not support their own weight during terrestrial locomotion through fin action alone and a scheme of evolution is proposed according to which the paired fins of osteolepids and tristicopterids evolved with a dual function: in locomotion and support of lung ventilation

Lung ventilation in dipnoan fishes

Lung ventilation in Dipnoi and probably all other primitive fishes is effected by muscular action of the buccopharyngeal region (inhalation) and the muscular and elastic lung wall (exhalation). Differential hydrostatic pressure plays no major part in ventilation. Lung volume is under precise control

An Early Triassic hybodont shark from Northern Madagascar

Material of the upper and lower jaws, together with teeth and other remains, of a Triassic hybodont shark from Madagascar is tentatively referred to the genus Acrodus. The material offers new evidence concerning the jaw suspension in hybodont sharks and its significance in the evolution of Elasmobranchii

Glyptolepis from the Middle Devonian of Scotland

The Rhipidistia (Osteichthyes, Crossopterygii) comprise three superfamilies of Paleozoic fossil fishes, the Holoptychoidea, Osteolepoidea and Rhizodontoidea…

On the biology of cosmine

Cosmine is a unique combination of dentine, enameloid and, at least in the functional sense, some true bone, with the pore-canal sensory system, and is found only in certain early fishes….https://elischolar.library.yale.edu/peabody_museum_natural_history_bulletin/1039/thumbnail.jp