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Dolphins are able to successfully coordinate their behavior using audio signals. Therefore, the current study tested whether or not belugas can use sound to exchange information in a cooperative task and verified the mechanisms of the transmission of information during trials. The subjects are two male belugas, Nack and Duke. Nack was trained to rotate its body when the experimenter turns a hand in a circular motion (rotation cue) or to take a vertical position on the spot of the pool when the experimenter turned on a light toward the subject (headstand cue). Duke was required to do the same behavior as Nack but was blindfolded. During the test trials, the experimenter presented both cues toward Nack in random order. The result indicated that Nack responded correctly to both cues, and Duke behaved similarly to Nack. Moreover, Nack emitted different sounds in response to the cues, which indicates that Nack spontaneously transmitted information to Duke by emitting sounds, which led Duke to provide correct responses. Although Duke displayed the same behaviors as Nack did despite the lack of training to do so, Duke’s performance was due to learning by hearing sounds instead of training.

We tested the ability of a beluga (Delphinapterus leucas) to imitate sounds presented to it. During the training session, we presented the subject three recorded sounds that were emitted by the subject, and the subject was trained to imitate them. The subject learned to correctly imitate the sounds. During the test session, two novel computer-generated artificial sounds were presented through an audio speaker. In addition, nine arbitrary vocal sounds produced by the experimenter were presented to the subject, and the subject was required to imitate them. Seven persons, who were not involved in the experiment, were presented the sample sounds and imitated calls; subsequently, they judged whether both sounds were similar to each other. In addition, sound spectrums of the sample sounds and imitated calls were analyzed. As a result, some components of the sound spectrums were similar, and most of imitated calls possess spectral features similar to the sample sounds. These results demonstrated that the beluga was able to correctly imitate novel sounds and spontaneously displayed aptitude for imitation.

A beluga was tested to label objects using vocal symbols in order to form a bidirectional relationship between the visual symbols and sounds. In the Training session, the subject was first trained todistinguish four objects by four separate calls that he made. He learned to emit different calls corresponding to the sample stimuli. Next, these three recorded calls were played back to the subject,and he was required to select the objects (comparative stimuli) corresponding to the presented sound. He succeeded in correctly choosing the objects corresponding to the sounds played back. In the Test session, when a completely new recorded sound was presented to the subject, he could choose the correct object by matching the sample sound with the object. It is suggested that a beluga have realized bidirectional relationships or symmetrical relationship between visual symbols and sounds.This is a preliminary study that shows both production and comprehension of symbols in marine mammals.

Optical transition properties of nanocrystalline silicon (nc-Si) doped Si[O.sub.2] thin films prepared by cosputtering with Si[O.sub.2] target and Si-chips followed by high temperature annealing were investigated as a function of ratio of target area (Si/Si[O.sub.2]) in the range of 0 to 0.19. Optical transmission measurements revealed that the indirect band-gap of nc-Si decreased from 4.87 to 2.32 eV with increasing Si/Si[O.sub.2] from 0.04 to 0.19, whereas no noticeable absorption was observed for the samples with Si/Si[O.sub.2] = 0.00. Photoluminescence (PL) measurements showed that considerably weak emissions due to oxygen deficient center (ODC) in Si[O.sub.2] films were observed at 514-539 nm for samples with lower Si/Si[O.sub.2] of 0.0-0.09, while the strong emissions due to an interfacial layer between the nc-Si core and the Si[O.sub.2] surface layer were observed at 746-808 nm for samples with higher Si/Si[O.sub.2] of 0.13-0.19. PL excitation spectrum monitored at 800 nm showed that the PL at 800 nm was excited through nc-Si. On the other hand, cathodoluminesncence peaks were observed at 455 and 465 nm for the samples with 0.04 and 0.13, respectively, in which both peaks were assigned to originate from oxygen vacancies created during electron beam irradiation. The mechanisms of three types of luminescence, due to the ODC in Si[O.sub.2] band-to-band transition of nc-Si, and the interfacial layer between the nc-Si core and the Si[O.sub.2] surface layer, are discussed. PACS Nos.: 78.67.Bf, 78.55.Hx, 81.15.Cd. Nous analysons, en fonction d'un rapport de surface de cible (Si/Si[O.sub.2]) variant de 0 a 0,19, les proprietes des transitions optiques de films minces de Si[O.sub.2] dopes au silicium nanocristallin, nc-Si, prepares par une co-pulverisation avec des cibles de Si[O.sub.2] et des puces de Si, suivie d'un recuit a haute temperature. Les mesures de transmission optique revelent que la bande interdite indirecte du nc-Si decroit de 4,87 a 2,32 eV lorsque Si/Si[O.sub.2] augmente de 0,04 a 0,19, alors qu'on n'observe aucune absorption pour les echantillons avec Si/Si[O.sub.2] = 0,0. Des mesures de photoluminescence (PL) montrent qu'une tres faible emission due au centre deficient en oxygene (ODC) dans les films de Si[O.sub.2] est observee a 514-539 nm pour les echantillons avec Si/Si[O.sub.2] = 0,0-0,09, alors qu'une forte emission due a une couche inter-faciale entre le coeur de nc-Si et la couche de surface de Si[O.sub.2] est observee a 706-808 nm pour des echantillons avec Si/Si[O.sub.2] = 0,13-0,19. Le spectre d'excitation de PL observe a 800 nm montre que le PL a 800 nm est excite par le nc-Si. D'autre part, les pics de cathodoluminescence sont observes a 455 et 465 nm pour les echantillons avec 0,04 et 0,13 respectivement, dans lesquels les deux pics proviennent de lacunes en oxygene crees pendant l'irradiation par faisceau d'electrons. Nous discutons des trois mecanismes de luminescence, due aux ODC dans le Si[O.sub.2], aux transitions bande-a-bande du nc-Si et a la couche interfaciale entre le coeur de nc-Si et la couche de surface de Si[O.sub.2]. [Traduit par la Redaction], 1. Introduction Multifunctional electronic devices are attractive for the realization of optoelectronic integrated circuits because one electronic device has many functions (e.g., light emitting device and flash memory), which can [...]

Single-phase polycrystalline beta-FeSi2 formation up to the surface was attained by heavy implantation of Fe+ ions into Si and subsequent two-step annealing. Its optical absorption and photoluminescence characteristics were systematically examined as a function of second-step annealing temperature and its duration time. Findings indicated that the implanted layer is composed of polycrystalline precipitates of beta-FeSi2 with a small amount of Si. The type of the optical transition and the inverse logarithmic slope of the Urbach tail were studied.

Presents a study which showed that the formation of ΒFeSi[sub2] is achieved by high dose iron ion implantation into silicon and subsequent two-step annealing. Experimental methods; Results and discussion; Conclusions.

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