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Blainville's beaked whales (Mesoplodon densirostris Blainville) echolocate for prey during deep foraging dives. Here we use acoustic tags to demonstrate that these whales, in contrast to other toothed whales studied, produce two distinct types of click sounds during different phases in biosonar-based foraging. Search clicks are emitted during foraging dives with inter-click intervals typically between 0.2 and 0.4 s. They have the distinctive form of an FM upsweep (modulation rate of about 110 kHz ms(-1)) with a -10 dB bandwidth from 26 to 51 kHz and a pulse length of 270 micros, somewhat similar to chirp signals in bats and Cuvier's beaked whales (Ziphius cavirostris Cuvier), but quite different from clicks of other toothed whales studied. In comparison, the buzz clicks, produced in short bursts during the final stage of prey capture, are short (105 micros) transients with no FM structure and a -10 dB bandwidth from 25 to 80 kHz or higher. Buzz clicks have properties similar to clicks reported from large delphinids and hold the potential for higher temporal resolution than the FM clicks. It is suggested that the two click types are adapted to the separate problems of target detection and classification versus capture of low target strength prey in a cluttered acoustic environment.

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Toothed whales (Cetacea, odontoceti) emit sound pulses to probe their surroundings by active echolocation. Non-invasive, acoustic Dtags were placed on deep-diving Blainville's beaked whales (Mesoplodon densirostris) to record their ultrasonic clicks and the returning echoes from prey items, providing a unique view on how a whale operates its biosonar during foraging in the wild. The process of echolocation during prey capture in this species can be divided into search, approach and terminal phases, as in echolocating bats. The approach phase, defined by the onset of detectable echoes recorded on the tag for click sequences terminated by a buzz, has interclick intervals (ICI) of 300-400 ms. These ICIs are more than a magnitude longer than the decreasing two-way travel time to the targets, showing that ICIs are not given by the two-way-travel times plus a fixed, short lag time. During the approach phase, the received echo energy increases by 10.4(+/-2) dB when the target range is halved, demonstrating that the whales do not employ range-compensating gain control of the transmitter, as has been implicated for some bats and dolphins. The terminal/buzz phase with ICIs of around 10 ms is initiated when one or more targets are within approximately a body length of the whale (2-5 m), so that strong echo returns in the approach phase are traded for rapid updates in the terminal phase. It is suggested that stable ICIs in the search and approach phases facilitate auditory scene analysis in a complex multi-target environment, and that a concomitant low click rate allows the whales to maintain high sound pressure outputs for prey detection and discrimination with a pneumatically driven, bi-modal sound generator.

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BACKGROUND: The contribution of middle-ear development to the overall development of hearing has not been explored in great detail. This presentation describes the maturation of conductive elements in the rat middle ear, and provides the basis on which future studies of middle-ear functional development will follow. METHODS: The middle-ear apparatus was examined at nine different ages (between 1 and 80 days postpartum) in Long Evans rats. At each age elements of the conducting apparatus was observed with either light or scanning electron microscopy (SEM), and quantitative measurements were made from video enhanced photomicrographs. Tympanic membrane area and cone depth, the length of the malleus and incus arms, ossicular weight, stapes foot plate and oval window areas, and bulla volume were all measured. Development of the area and lever ratios were derived from these measurements. The data were fitted to exponential equations and the time in days required to reach 90% of the adult level determined. RESULTS: The pars tensa achieved 90% of total area by 17 days. The oval window achieved the 90% criterion by 13 days, while the area ratio was within 10% of its adult size by 8 days. The ossicles took between 26 and 34 days, while bulla volume took 59 days to reach the 90% level. CONCLUSIONS: Middle-ear growth was very orderly and systematic in the data reported. When maturation of the area ratio was considered against development of the endocochlear potential or the round window compound action potential, it was clear that the growth of this important aspect of the middle ear preceded the onset of cochlear function.

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We investigated orofacial manifestations in 42 patients with Melkersson-Rosenthal syndrome who were examined at our institution between 1965 and 1990. Patient histories and histologic and clinical findings were reviewed in detail. These data were compared with the oral findings in 220 cases that were reported in the literature between 1965 and 1990. There were 28 females in our study. The age at onset of signs and symptoms varied widely with a mean of 33.8 years. Most frequent initial signs were labial edema, facial swelling, and Bell's palsy. During the course of the disease, 75% of all patients had labial swelling, 50% had facial edema, and 33% had Bell's palsy. Swelling, erythema, or painful erosions that affected the gingiva, buccal mucosa, palate, or tongue were common intraoral symptoms. A comparison with patients reported in the literature revealed a similar frequency of extraoral symptoms but more prevalent intraoral symptoms in our patients.

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To investigate public awareness and acceptance of dental implants, 120 adult US citizens were asked to answer a questionnaire. Of the 109 persons who completed the questionnaire, 77% had heard about dental implants, mostly through media and lay persons. Only 17% named a dentist or physician as the source of information. Persons with many missing teeth were not more aware of implants than those with fewer missing teeth. Of 19 removable denture prosthesis wearers, 15 knew about implants but only one third learned of them from their dentist or physician. Of 84 persons with information about implants, 51 would consider implant treatment, 17 would not, and 16 were undecided. Esthetics was the most frequent motivating factor favoring implants, while high cost was the most frequent argument against them. Younger interviewees were significantly more often in favor of implants than older persons. It was concluded that public awareness and acceptance of dental implants are high. Dentists and physicians, however, play only a minor role as sources of information.

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