PubMed · 5776943
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E D Schubert. 1969. On estimating aural harmonics.. https://pubmed.ncbi.nlm.nih.gov/5776943/
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Previous studies have shown that acoustic rhinometry (AR) is well suited to describe the nasal airway dimensions in healthy infants. The technique is quick to perform, non-invasive, without potential hazards and requires minimal cooperation. Due to the small dimensions of the infant nasal airways, the optimized miniprobe (Rhinometrics, Lynge, Denmark) provides abilities superior to those of adult probes. The equipment is portable and examinations can be performed in the maternity ward, out-patient department or at home. Measurements on models simulating the pre- and post-operative nasal geometry were performed to determine the accuracy and resolution of AR and to improve the interpretation of the curves obtained in vivo. Acoustic measurements in five infants with congenital respiratory distress caused by bilateral choanal atresia or stenosis have been compared with CT-scans and the results of the model simulations to evaluate the diagnostic value of the method. We conclude that AR represents a new and valuable tool in the diagnosis of congenital choanal malformations. Despite current technical limitations, it may also be of value in the post-operative evaluation, particularly if the posterior part of the septum is not resected.
The effect of red, white and blue environmental noise on discrete-time population dynamics is analyzed. The coloured noise is superimposed on Moran-Ricker and Maynard Smith dynamics, the resulting power spectra are less than examined. Time series dominated by short- and long-term fluctuations are said to be blue and red, respectively. In the stable range of the Moran-Ricker dynamics, environmental noise of any colour will make population dynamics red or blue depending the intrinsic growth rate. Thus, telling apart the colour of the noise from the colour of the population dynamics may not be possible. Population dynamics subjected to red and blue environmental noises show, respectively, more red or blue power spectra than those subjected to white noise. The sensitivity to differences in the noise colours decreases with increasing complexity and ultimately disappears in the chaotic range of the population dynamics. These findings are duplicated with the Maynard Smith model for high growth rates when the strength of density dependence changes. However, for low growth rates the power spectra of the population dynamics with noise are red in stable, periodic and aperiodic ranges irrespective of the noise colour. Since chaotic population fluctuations may show blue spectra in the deterministic case, this implies that blue deterministic chaos may become red under any colour of the noise.
Aspergillus flavus and other pathogenic fungi display typical infrared spectra which differ significantly from spectra of substrate materials such as corn. On this basis, specific spectral features have been identified which permit detection of fungal infection on the surface of corn kernels by photoacoustic infrared spectroscopy. In a blind study, ten corn kernels showing bright greenish yellow fluorescence (BGYF) in the germ or endosperm and ten BGYF-negative kernels were correctly classified as infected or not infected by Fourier transform infrared photoacoustic spectroscopy. Earlier studies have shown that BGYF-positive kernels contain the bulk of the aflatoxin contaminating grain at harvest. Ten major spectral features, identified by visual inspection of the photoacoustic spectra of A. flavus mycelium grown in culture versus uninfected corn, were interpreted and assigned by theoretical comparisons of the relative chemical compositions of fungi and corn. The spectral features can be built into either empirical or knowledge-based computer models (expert systems) for automatic infrared detection and segregation of grains or kernels containing aflatoxin from the food and feed supply.