Distortion product otoacoustic emissions in schoolchildren: Effects of ear asymmetry, handedness and gender

The present study examined effects of ear asymmetry, handedness, and gender on distortion-product otoacoustic emissions (DPOAEs) obtained from schoolchildren. A total of 1003 children (528 boys and 475 girls), with a mean age of 6.2 years (SD = 0.4, range = 5.2-7.9 years), were tested in a quiet room at their schools using the GSI-60 DPOAE system. A distortion-product (DP)-gram was obtained for each ear, with f2 varying from 1.1 to 6.0 kHz and the ratio of f2/f1 at 1.21. The signal-to-noise ratios (SNRs) (DPOAE amplitude minus the mean noise floor) at the tested frequencies 1.1, 1.5, 1.9, 2.4, 3.0, 3.8, 4.8, and 6.0 kHz were measured. The results revealed a small but significant difference in SNR between ears, with right ears showing a higher mean SNR than left ears at 1.9, 3.0, 3.8, and 6.0 kHz. At these frequencies, the difference in mean SNR between ears was less than 1 dB. A significant gender effect was also found. Girls exhibited a higher SNR than boys at 3.8, 4.8, and 6.0 kHz. The difference in mean SNR, as a result of the gender effect, was about 1 to 2 dB at these frequencies. There was no significant difference in mean SNR between left-handed and right-handed children for all tested frequencies.

Distortion product otoacoustic emissions in children at school entry: A comparison with pure tone screening and tympanometry results

This study examined the test performance of distortion product otoacoustic emissions (DPOAEs) when used as a screening tool in the school setting. A total of 1003 children (mean age 6.2 years, SD = 0.4) were tested with pure-tone screening, tympanometry, and DPOAE assessment. Optimal DPOAE test performance was determined in comparison with pure-tone screening results using clinical decision analysis. The results showed hit rates of 0.86, 0.89, and 0.90, and false alarm rates of 0.52, 0.19, and 0.22 for criterion signal-to-noise ratio (SNR) values of 4, 5, and 11 dB at 1.1, 1.9, and 3.8 kHz respectively. DPOAE test performance was compromised at 1.1 kHz. In view of the different test performance characteristics across the frequencies, the use of a fixed SNR as a pass criterion for all frequencies in DPOAE assessments is not recommended. When compared to pure tone plus tympanometry results, the DPOAEs showed deterioration in test performance, suggesting that the use of DPOAEs alone might miss children with subtle middle ear dysfunction. However, when the results of a test protocol, which incorporates both DPOAEs and tympanometry, were used in comparison with the gold standard of pure-tone screening plus tympanometry, test performance was enhanced. In view of its high performance, the use of a protocol that includes both DPOAEs and tympanometry holds promise as a useful tool in the hearing screening of schoolchildren, including difficult-to-test children.

Quantum symmetries and the Weyl–Wigner product of group representations

In the usual formulation of quantum mechanics, groups of automorphisms of quantum states have ray representations by unitary and antiunitary operators on complex Hilbert space, in accordance with Wigner's theorem. In the phase-space formulation, they have real, true unitary representations in the space of square-integrable functions on phase space. Each such phase-space representation is a Weyl–Wigner product of the corresponding Hilbert space representation with its contragredient, and these can be recovered by 'factorizing' the Weyl–Wigner product. However, not every real, unitary representation on phase space corresponds to a group of automorphisms, so not every such representation is in the form of a Weyl–Wigner product and can be factorized. The conditions under which this is possible are examined. Examples are presented.

The response of native Australian rodents to predator odours varies seasonally: a by-product of life history variation?

Small mammals are subject to predation from mammalian, avian and reptilian predators. There is an obvious advantage for prey species to detect the presence of predators in their environment, enabling them to make decisions about movement and foraging behaviour based on perceived risk of predation. We examined the effect of faecal odours from marsupial and eutherian predators, and a native reptilian predator, on the behaviour of three endemic Australian rodent species (the fawn-footed melomys, Melomys cervinipes, the bush rat, Rattus fuscipes, and the giant white-tailed rat, Uromys caudimaculatus) in rainforest remnants on the Atherton Tableland, North Queensland, Australia. Infrared camera traps were used to assess visit rates of rodents to odour stations containing faecal and control odours. Rodents avoided odour stations containing predator faeces, but did not avoid herbivore or control odours. The responses of the three prey species differed: in the late wet season U. caudimaculatus avoided predator odours, whereas R. fuscipes and M. cervinipes did not. In contrast, in the late dry season all three species avoided odour stations containing predator odours. We speculate that these different responses may result from variation in life history traits between the species. (c) 2006 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.

H-1 NMR spectroscopic studies of the stability of an oxazolidine condensation product

Condensation of (-)-norephedrine with excess formaldehyde under mild conditions leads to formation of the 2:1 condensation product N,N'-methylenebis(4-methyl-5-phenyl)oxazolidine compared with the reaction with 1 mol of formaldehyde, which leads to 4-methyl-5-phenyloxazolidine. H-1 and C-13 NMR spectroscopy was used to monitor the stability of this compound and its decomposition products. The 2:1 condensation product is found to be stable in CDC1(3) but breaks down rapidly in CD3OD to yield a 50:50 mixture of 4-methyl-5-phenyloxazolidine and 3-hydroxymethyl-4-methyl-5-phenyloxazolidine. Upon addition of D2O to this equimolar mixture, the latter compound decomposes to norephedrine and formaldehyde, whereas the former compound is stable. (C) 1997 by John Wiley & Sons, Ltd.

Matrix-product codes over Fq

Codes C-1,...,C-M of length it over F-q and an M x N matrix A over F-q define a matrix-product code C = [C-1 (...) C-M] (.) A consisting of all matrix products [c(1) (...) c(M)] (.) A. This generalizes the (u/u + v)-, (u + v + w/2u + v/u)-, (a + x/b + x/a + b + x)-, (u + v/u - v)- etc. constructions. We study matrix-product codes using Linear Algebra. This provides a basis for a unified analysis of /C/, d(C), the minimum Hamming distance of C, and C-perpendicular to. It also reveals an interesting connection with MDS codes. We determine /C/ when A is non-singular. To underbound d(C), we need A to be 'non-singular by columns (NSC)'. We investigate NSC matrices. We show that Generalized Reed-Muller codes are iterative NSC matrix-product codes, generalizing the construction of Reed-Muller codes, as are the ternary 'Main Sequence codes'. We obtain a simpler proof of the minimum Hamming distance of such families of codes. If A is square and NSC, C-perpendicular to can be described using C-1(perpendicular to),...,C-M(perpendicular to) and a transformation of A. This yields d(C-perpendicular to). Finally we show that an NSC matrix-product code is a generalized concatenated code.