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The late Neogene megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), is mostly known for its gigantic teeth and vertebrae. Re-examination of the rock matrix surrounding a previously described associated tooth set of O. megalodon from the upper Miocene of Japan resulted in the observation of numerous fragments of tessellated calcified cartilage and placoid scales. The morphology of each tessera and the arrangement of overall tessellated calcified cartilage are practically identical to those of extant chondrichthyans. Many placoid scales possess pronounced, rather broadly-spaced keels. A quantitative relationship between interkeel distances of keeled scales and reported cruising speeds across extant pelagic lamniforms and carcharhiniforms suggests that O. megalodon with a representative interkeel distance of ca. 100 µm was not a fast swimmer. We propose that O. megalodon was generally a slow cruising shark with occasional burst swimming for prey capture, where much of its metabolic heat through regional endothermy was possibly used to facilitate the digestion of large pieces of ingested meat as well as absorbing and processing nutrients. If so, the relative importance of the functional roles of regional endothermy possibly shifted from maintaining high cruising speeds to visceral food processing through the evolution towards gigantism in otodontids. [ABSTRACT FROM AUTHOR]

This study provides experimental evidence for the following: (1) Excess minority carrier recombination at SiO2/Si interfaces is associated with O2 dissociative adsorption; (2) the x-ray induced enhancement of SiO2 growth is not caused by the band flattening resulting from the surface photovoltaic effect but by the electron–hole pair creation resulting from core level photoexcitation for the spillover of bulk Si electronic states toward the SiO2 layer; and (3) a metastable chemisorbed O2 species plays a decisive role in combining two types of the single- and double-step oxidation reaction loops. Based on experimental results, the unified Si oxidation reaction model mediated by point defect generation [S. Ogawa et al., Jpn. J. Appl. Phys., Part 1 59, SM0801 (2020)] is extended from the viewpoints of (a) the excess minority carrier recombination at the oxidation-induced vacancy site and (b) the trapping-mediated adsorption through the chemisorbed O2 species at the SiO2/Si interface. [ABSTRACT FROM AUTHOR]

Because graphene stacked on hexagonal boron nitride (h-BN) exhibits high electron mobility, it is expected to be applied to next-generation high-speed transistors and electron emitters. To further improve the performance of graphene/h-BN devices, it is necessary to determine the band alignment of graphene/h-BN laminates. However, because mechanically peeled h-BN single crystals transferred onto Si substrates are small, pinpoint observation of h-BN with ordinary photoelectron spectroscopy is difficult. In this study, the electric structure of a graphene/h-BN laminate was identified by photoemission electron microscopy and local measurements of valence band and secondary electron spectra using micro-ultraviolet photoelectron spectroscopy were performed. From these measurements, we determined the band alignment of a graphene/h-BN laminate with a crystal size of a few tens of micrometers. The work function and electron affinity measured by photoelectron spectroscopy of single-crystal h-BN were 4.6 and −0.5 eV, respectively. Laminating graphene on h-BN caused the Fermi level of h-BN to rise 0.85 eV above that of nonlaminated h-BN. In addition, it was found that graphene on h-BN displayed weak n-type conductivity. The results obtained in this research are expected to be widely applied in the field of electronics such as electron emitters using h-BN with negative electron affinity. [ABSTRACT FROM AUTHOR]

The effect of naturally adsorbed gas on an NiP-Al substrate surface on the growth of a very thin WCr seedlayer and the effect of growth form of a WCr seedlayer on the microstructure and properties of magnetic recording media have been studied. An Auger electron spectroscopy analysis result clarifies that the critical thickness at which the WCr seedlayer changes from island-like to continuous layer is 2.5 and 1.5 nm when grown on the substrate surface with and without naturally adsorbed gas, respectively. The result means that the NiP-Al substrate surface with adsorbed gas enhances the island-like growth of the WCr seedlayer, probably due to the reduction of mobility of sputtered WCr particles when they react with the adsorbed gas on a substrate surface. It is found that the media grain size and the media noise are reduced only when using a WCr seedlayer thinner than 1.25 nm fabricated on substrate surface with adsorbed gas. Index Terms--Auger electron spectroscopy (AES), initial growth style, naturally adsorbed gas, reflection high-energy electron diffraction (RHEED), very thin WCr seedlayer.

W[Cr.sub.100-X] (X = 0-100) and Cr[Ti.sub.15] seedlayers with a thickness of 0.5 nm have been utilized to reduce the grain size of CoCrPtB-CrMo longitudinal media. It is found that the media grain size and the media noise are reduced when using W[Cr.sub.100-X] (X = 0, 25, 50) seedlayers and not reduced when using Cr[Ti.sub.15] or W[Cr.sub.100-X] (X = 75,100) seedlayer. Auger electron spectroscope (AES) analysis results show that the critical thickness just before W, W[Cr.sub.50] and Cr seedlayers become continuous layer are 1.5, 2.5, and 5 nm, respectively. Reflection high-energy electron diffraction (RHEED) analysis shows that the structure of 2.0-nm W film is consisted of very small two-dimensional random oriented crystal grains. This result suggests that W seedlayer, which has the highest melting point, forms a layer-like film with very small and dense island grains, due to its high free surface energy and low mobility. On the other hand, W[Cr.sub.50] and Cr seedlayers, which have a lower melting point than W seedlayer, form island film. It is concluded that W[Cr.sub.100-X] (X = 0, 25, 50) seedlayers that have dispersed island film and higher melting point than the underlayer are effective to reduce the grain size and the media noise in CoCrPtB-CrMo media. Index Terms--Auger electron spectroscope (AES), island or layer-like structure, melting point, reflection high-energy electron diffraction (RHEED), very thin Cr-based seedlayer.