Transient evoked otoacoustic emissions in children studying in special schools

Objectives: The present study aimed to investigate the feasibility and practicalities or testing children in special school settings using transient evoked otoacoustic emissions (TEOAE) and tympanometry. Children studying in special schools, particularly those with intellectual impairment, may be highly susceptible to hearing pathologies and can be difficult to assess using traditional test batteries. Researchers have recently suggested the possible applicability of TEOAE testing. in lieu of conventional behavioral methods, as a hearing screening device for persons with intellectual impairment. However, to date. few publications have detailed the particulars and results of such testing. Methods: A total of 489 children, with a mean age of 9.6 years, were tested in 15 special schools. Case information was obtained regarding birth history, medical history and type,degree of impairment, for later comparison with screening results. TEOAEs were collected using Quickscreen mode of the ILO292 Otodynamics Analyzer, whilst tympanometry was performed utilizing a Madsen Zodiac 901 Middle Ear Analyzer. Results: In total, 80% of students were able to be tested using TEOAEs. Average test time per ear was 2 min. However, a large proportion (40 of those able to be tested) failed TEOAE testing in at least one ear. No significant effects were found between could-not-test (CNT) cases and case history factors, A significant difference in TEOAE failure rates was found across history of neonatal special care nursery residency and history of parental concern regarding possible hearing impairment. Failure rates were higher for those who indicated positive histories. A total of 74% of subjects could be tested using tympanometry, with 25% of those able to be tested failing in at least one ear. Notably, neither type nor degree of impairment had any significant bearing on CNT or failure rates for tympanometry or TEOAE screening. Conclusions: Findings of the present investigation lend support to the review of hearing screening programs for children in special schools. with TEOAEs presenting as a potential alternative procedure. Further examination of the performance measures of protocols incorporating TEOAEs would now be advantageous. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Handedness effects in transient evoked otoacoustic emissions in school children

Handedness, as a potentially influencing, nonpathologic factor, has not been investigated in relation to transient evoked otoacoustic emissions (TEOAEs). The present study aimed to examine the effects of handedness on the TEOAE spectrum in entry-level schoolchildren, with attention also to possible ear asymmetry. A total of 228 subjects (114 males, 114 females, mean age = 6.3 years) were tested using the ILO292 Otodynamics Analyzer (Quickscreen mode) in quiet rooms in 22 schools. For statistical analysis, subjects were matched for factors such as handedness, gender, age, and history of recent ear infection. The results from subjects with passing TEOAE, pure-tone screening, and tympanometry revealed no significant handedness effect overall, although a significant ear asymmetry effect on the measurement parameters of AB difference, noise level, response level, whole-wave reproducibility, band reproducibility, and signal-to-noise ratios was found.

A normative study of distortion product otoacoustic emissions in six-year-old school children

Evoked otoacoustic emissions have demonstrated potential for application in the community-based hearing screening of paediatric populations. Distortion-product otoacoustic emissions (DPOAEs), as opposed to transient evoked otoacoustic emissions (TEOAEs), have not been extensively researched in this regard. The current study aimed to describe the range of DPOAE values obtained in a large cohort (1576 ears) of 6-year-old children in school settings and to examine possible ear asymmetry, gender and history of ear infection effects on the data. Results indicated a variety of significant effects, particularly in the high frequencies, for DPOAE signal-to-noise ratio. The measurement parameter, DPOAE amplitude (DP-amp), was found to display potentially less clinical applicability due to large standard deviation values. Use of descriptive normative data, as derived in the present investigation, may contribute toward future improvements in the hearing screening of 6-year-old schoolchildren

Design of microchannel free-space optical interconnects based on vertical-cavity surface-emitting laser arrays

We investigate the design of free-space optical interconnects (FSOIs) based on arrays of vertical-cavity surface-emitting lasers (VCSELs), microlenses, and photodetectors. We explain the effect of the modal structure of a multimodeVCSEL beam on the performance of a FSOI with microchannel architecture. A Gaussian-beam diffraction model is used in combination with the experimentally obtained spectrally resolved VCSEL beam profiles to determine the optical channel crosstalk and the signal-to-noise ratio (SNR) in the system. The dependence of the SNR on the feature parameters of a FSOI is investigated. We found that the presence of higher-order modes reduces the SNR and the maximum feasible interconnect distance. We also found that the positioning of a VCSEL array relative to the transmitter microlens has a significant impact on the SNR and the maximum feasible interconnect distance. Our analysis shows that the departure from the traditional confocal system yields several advantages including the extended interconnect distance and/or improved SNR. The results show that FSOIs based on multimode VCSELs can be efficiently utilized in both chip-level and board-level interconnects. (C) 2002 Optical Society of America.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

Modelling the activated sludge flocculation process combining laser light diffraction particle sizing and population balance modelling (PBM)

A technique based on laser light diffraction is shown to be successful in collecting on-line experimental data. Time series of floc size distributions (FSD) under different shear rates (G) and calcium additions were collected. The steady state mass mean diameter decreased with increasing shear rate G and increased when calcium additions exceeded 8 mg/l. A so-called population balance model (PBM) was used to describe the experimental data, This kind of model describes both aggregation and breakage through birth and death terms. A discretised PBM was used since analytical solutions of the integro-partial differential equations are non-existing. Despite the complexity of the model, only 2 parameters need to be estimated: the aggregation rate and the breakage rate. The model seems, however, to lack flexibility. Also, the description of the floc size distribution (FSD) in time is not accurate.

The current status of laser applications in dentistry

A range of lasers. is now available for use in dentistry. This paper summarizes key current and emerging applications, for lasers in clinical practice. A major diagnostic application of low power lasers is the detection of caries, using fluorescence elicited from hydroxyapatite or from bacterial by-products. Laser fluorescence is an effective method for detecting and quantifying incipient occlusal and cervical,carious lesions, and with further refinement could be used in the, same manner for proximal lesions. Photoactivated dye techniques have been developed which use low power lasers to elicit a photochemical reaction, Photoactivated dye techniques' can be used to disinfect root canals, periodontal pockets, cavity preparations and sites of peri-implantitis. Using similar principles, more powerful lasers tan be used for photodynamic therapy in the treatment of malignancies of the oral mucosa. Laser-driven photochemical reactions can also be used for tooth whitening. In combination with fluoride, laser irradiation can improve the resistance of tooth structure to demineralization, and this application is of particular benefit for susceptible sites in high caries risk patients. Laser technology for caries' removal, cavity preparation and soft tissue surgery is at a high state of refinement, having had several decades of development up to the present time. Used in conjunction with or as a replacement for traditional methods, it is expected that specific laser technologies will become an essential component of contemporary dental practice over the next decade.

Use of confocal scanning laser microscopy to measure the concentrations of aerial and penetrative hyphae during growth of Rhizopus oligosporus on a solid surface

In order to develop a method for use in investigations of spatial biomass distribution in solid-state fermentation systems, confocal scanning laser microscopy was used to determine the concentrations of aerial and penetrative biomass against height and depth above and below the substrate surface, during growth of Rhizopus oligosporus on potato dextrose agar. Penetrative hyphae had penetrated to a depth of 0.445 cm by 64 h and showed rhizoid morphology, in which the maximum biomass concentration, of 4.45 mg dry wt cm(-3), occurred at a depth of 0.075 cm. For aerial biomass the maximum density of 39.54 mg dry wt(-3) occurred at the substrate surface. For both aerial and penetrative biomass, there were two distinct regions in which the biomass concentration decayed exponentially with distance from the surface. For aerial biomass, the first exponential decay region was up to 0.1 cm height. The second region above the height of 0.1 cm corresponded to that in which sporangiophores dominated. This work lays the foundation for deeper studies into what controls the growth of fungal hyphae above and below the surfaces of solid substrates. (C) Wiley Periodicals, Inc.

Synthesis of optically complex core-shell colloidal suspensions: Pathways to multiplexed biological screening

The ability to generate enormous random libraries of DNA probes via split-and-mix synthesis on solid supports is an important biotechnological application of colloids that has not been fully utilized to date. To discriminate between colloid-based DNA probes each colloidal particle must be 'encoded' so it is distinguishable from all other particles. To this end, we have used novel particle synthesis strategies to produce large numbers of optically encoded particle suitable for DNA library synthesis. Multifluorescent particles with unique and reproducible optical signatures (i.e., fluorescence and light-scattering attributes) suitable for high-throughput flow cytometry have been produced. In the spectroscopic study presented here, we investigated the optical characteristics of multi-fluorescent particles that were synthesized by coating silica 'core' particles with up to six different fluorescent dye shells alternated with non-fluorescent silica 'spacer' shells. It was observed that the diameter of the particles increased by up to 20% as a result of the addition of twelve concentric shells and that there was a significant reduction in fluorescence emission intensities from inner shells as an increasing number of shells were deposited.

Quantum theory of the far-off-resonance continuous-wave Raman laser: Heisenberg-Langevin approach

We present the quantum theory of the far-off-resonance continuous-wave Raman laser using the Heisenberg-Langevin approach. We show that the simplified quantum Langevin equations for this system are mathematically identical to those of the nondegenerate optical parametric oscillator in the time domain with the following associations: pump pump, Stokes signal, and Raman coherence idler. We derive analytical results for both the steady-state behavior and the time-dependent noise spectra, using standard linearization procedures. In the semiclassical limit, these results match with previous purely semiclassical treatments, which yield excellent agreement with experimental observations. The analytical time-dependent results predict perfect photon statistics conversion from the pump to the Stokes and nonclassical behavior under certain operational conditions.

Transient evoked otoacoustic emissions in adults: a comparison between two test protocols

This study compares the performance of the Quickscreen and Default protocols of the ILO-96 Otodynamics Analyzer in recording transient evoked otoacoustic emissions (TEOAEs) from adults using clinical decision analysis. Data were collected from 25 males (mean age = 29.0 years, SD = 6.8) and 35 females (mean age = 28.1 years, SD = 9.6). The results showed that the mean signal-to-noise ratios obtained from the Quickscreen were significantly greater than those from the Default protocol at 1,2, and 4 kHz. The comparison of the performance of the two protocols, based on the results using receiver operating characteristics curves, revealed a higher performance of the Quickscreen than the Default protocol at 1 and 4 kHz but not at 2 kHz. In view of the enhanced performance of the Quickscreen over the Default protocol in general, the routine use of the Default protocol for testing adults in audiology clinics should be reconsidered.