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At least 793 records · Page 44Linked to original sources
PubMed1989

[Clinical study on sweep-frequency tympanometry--data analysis using principal component analysis].

A sweep-frequency tympanometer has been developed to diagnose auditory ossicular lesions more precisely. This device measures acoustic middle ear features by changing the probe tone frequency continuously. The oscillator sweeps frequency of the probe tone from 200 to 2,500Hz 1.5 seconds. A microphone picks up the changes in the acoustic pressure and the phase in the external auditory meatus during the frequency change of the probe tone. These measurements are performed under pressures at -200 and 0 dapa, and differences of both the acoustic pressure and the phase between these two pressures are graphically displayed using a microcomputer. This device can also measure and digitally display the frequency (BHz) and the sound pressure (BdB) at the minimum point (B) of the sound pressure curve, the frequency (ZHz) at 0 crossing point (Z) of the sound pressure curve, and the frequency (PHz) and the phase difference (Pdeg) at the maximum point (P) of the phase curve. Normal ranges of these five values were obtained to establish diagnostic criteria from 200 normal ears. The normal values were as follows: BHz, 480 to 1,070Hz; BdB, -6.0 to -1.8dB; ZHz, 1,100 to 1,860Hz; PHz, 910 to 1,820Hz; and Pdeg, 16.3 to 47.9 degrees. Eight cases of ossicular dislocation and 14 cases of ossicular fixation, all of which had normal external auditory meatus and tympanic membrane, were evaluated based on these values. All the cases with ossicular dislocation and 12 cases out of 14 with ossicular fixation were correctly diagnosed.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Impedance Tests↗
PubMedDate not supplied

Application of the principal component analysis (PCA) to the ecological study of an artificial environment: the tunny-fishing net of Camogli (Ligurian Sea).

The management of the marine environment and resource exploitation depend on the knowledge of both water conditions and ecological relationships between organisms. In the framework of fishing problems, an adequate food availability is important in order to allow maintaining and growth of fish stocks. The tunny-fishing of Camogli, owing to the coco-fibre texture of its net, can improve the trophic resources allowing the settlement of organisms eaten by fish. The distribution and composition of settled organisms was studied during the campaign 1988 by microscopical methods. The results have been elaborated by using multivariate (PCA) methods. Foraminifers, ciliates, hydroids, nematodes and copepods were the mainly observed groups. Their variations with season and depth and the relationships with caught fish species are presented. The elaboration of data by PCA allowed an easy and complete interpretation of the obtained complex data set showing the existence of a "rope" and of a "depth" effect.

Animals↗
PubMed1994

[Population projection and its principal components: the future model of population in the province of Alicante].

"In this article we analyze the different demographic patterns defining the population in the province of Alicante [Spain]. The behaviour of the demographic factors in the past and in the present is studied here, and a series of models are put into practice in order to foresee the future pattern of population.... The result shows either the effect of a possible ageing in an already aged population, as is the case of the province of Alicante, or what the job market would have to endure if the above mentioned ageing took place, increased by the possibility of an inmigration of an older population." (SUMMARY IN ENG AND FRE)

Age Distribution↗