Emission Amplitude Research Articles

Increased vitamin plasma levels in Swedish military personnel treated with nutrients prior to automatic weapon training

Noise-induced hearing loss (NIHL) is a significant clinical, social, and economic issue. The development of novel therapeutic agents to reduce NIHL will potentially benefit multiple very large noise-exposed populations. Oxidative stress has been identified as a significant contributor to noise-induced sensory cell death and NIHL, and several antioxidant strategies have now been suggested for potential translation to human subjects. One such strategy is a combination of beta-carotene, vitamins C and E, and magnesium, which has shown promise for protection against NIHL in rodent models, and is being evaluated in a series of international human clinical trials using temporary (military gunfire, audio player use) and permanent (stamping factory, military airbase) threshold shift models (NCT00808470). The noise exposures used in the recently completed Swedish military gunfire study described in this report did not, on average, result in measurable changes in auditory function using conventional pure-tone thresholds and distortion product otoacoustic emission (DPOAE) amplitudes as metrics. However, analysis of the plasma samples confirmed significant elevations in the bloodstream 2 hours after oral consumption of active clinical supplies, indicating the dose is realistic. The plasma outcomes are encouraging, but clinical acceptance of any novel therapeutic critically depends on demonstration that the agent reduces noise-induced threshold shift in randomized, placebo-controlled, prospective human clinical trials. Although this noise insult did not induce hearing loss, the trial design and study protocol can be applied to other populations exposed to different noise insults.

The Effect Aging on Latency of Distortion Product Otoacoustic Emission

Otoacoustic emission (OAE) originated from very specific locations in the cochlea are closely linked to the function of outer hair cells. Thus, the latency and amplitude of distortion product otoacoustic emission (DPOAE), afford valuable information about cochlear processes such as study of traveling wave propagation. This study was to predetermine the discrimination standard point of DPOAE latency, which discriminates the degree of age, and to estimate the accuracy and predictability of the discrimination standard point of DPOAE latency. DPOAE latency was examined in series of human subjects, with clinically normal hearing, ranging in age from 20 to 69 years. All 60 subjects were divided into 5 age groups. The aging effect on pure tone audiometry (PTA) did not exist, especially 60 years group showed higher threshold in all frequencies. The gender effect on DPOAE latency did not exist. The DPOAE latency increased as the frequency increased and decreased as the age increased. This finding was that, when compared between emissions in each age DPOAE latency were able to detect the functional effects of auditory aging. KEY WORDS：DPOAE·DPOAE latency·SOAE·TEOAE.

Structural and luminescence properties of amorphous SiO 2 nanoparticles

We report an experimental study on the photoluminescence band peaked at 2.7 eV (blue band) induced by thermal treatments in nanometric amorphous SiO 2. In particular the emission dependence on the nanometric particles size as a function of their mean diameter from 7 nm up to 40 nm is investigated. We found that the emission amplitude increases on decreasing the particle diameter, showing a strong correlation between the blue band and the nanometric nature of the particles. By Raman spectroscopy measurements it is evidenced that the SiO 2 nanoparticles matrix is significantly affected by the reduction of size. Basing on the shell-like model, these findings are interpreted assuming that the defects responsible for the photoluminescence are localized on a surface shell of the particles and not simply on their surface. In addition it is found that the generation efficiency of these defects depends on the structural properties of the SiO 2 matrix in the surface shell.

The Effect of Static Ear Canal Pressure on Human Spontaneous Otoacoustic Emissions: Spectral Width as a Measure of the Intra-cochlear Oscillation Amplitude

Spontaneous otoacoustic emissions can be detected as peaks in the Fourier spectrum of a microphone signal recorded from the ear canal. The height, center frequency, and spectral width of SOAE peaks changed when a static pressure was applied to the ear canal. Most commonly, with either increasing or decreasing static pressure, the frequency increased, the amplitude decreased, and the width increased. These changes are believed to result from changes in the middle ear properties. Specifically, reduced middle ear transmission is assumed to attenuate the amplitude of emissions. We reconsidered this explanation by investigating the relation between peak height and width. We showed that the spectral width of SOAE peaks is approximately proportional to 1/sqrt {{{hbox{peak}};{hbox{height}}}} . This is consistent with a (Rayleigh) oscillator model in which broadening of the SOAE peak is caused by broadband intra-cochlear noise, which is assumed to be independent of static ear canal pressure. The relation between emission peak height and width implicates that the intra-cochlear oscillation amplitude attentuates relative to the intra-cochlear noise level when a static ear canal pressure is applied. Apparently, ear canal static pressure directly affects the active mechanics in the inner ear.

Far-red light-regulated efficient energy transfer from phycobilisomes to photosystem I in the red microalga Galdieria sulphuraria and photosystems-related heterogeneity of phycobilisome population

Phycobilisomes (PBS) are the major photosynthetic antenna complexes in cyanobacteria and red algae. In the red microalga Galdieria sulphuraria, action spectra measured separately for photosynthetic activities of photosystem I (PSI) and photosystem II (PSII) demonstrate that PBS fraction attributed to PSI is more sensitive to stress conditions and upon nitrogen starvation disappears from the cell earlier than the fraction of PBS coupled to PSII. Preillumination of the cells by actinic far-red light primarily absorbed by PSI caused an increase in the amplitude of the PBS low-temperature fluorescence emission that was accompanied by the decrease in PBS region of the PSI 77 K fluorescence excitation spectrum. Under the same conditions, fluorescence excitation spectrum of PSII remained unchanged. The amplitude of P700 photooxidation in PBS-absorbed light at physiological temperature was found to match the fluorescence changes observed at 77 K. The far-red light adaptations were reversible within 2–5 min. It is suggested that the short-term fluorescence alterations observed in far-red light are triggered by the redox state of P700 and correspond to the temporal detachment of the PBS antenna from the core complexes of PSI. Furthermore, the absence of any change in the 77 K fluorescence excitation cross-section of PSII suggests that light energy transfer from PBS to PSI in G. sulphuraria is direct and does not occur through PSII. Finally, a novel photoprotective role of PBS in red algae is discussed.

Relationship between medial‐olivocochlear reflex strength and masked thresholds.

Otoacoustic emission amplitude is reduced by contralateral acoustic stimulation (CAS). This effect is produced by the medial‐olivocochlear (MOC) reflex. Past studies have shown that the MOC reflex is related to listening in noise and selective attention. The present study examined the relationship between the MOC reflex and masked thresholds in 14 normally hearing adults. Detection thresholds were determined for a 1000‐Hz, 300‐ms tone presented simultaneously with a 300‐ms masker. Three masking conditions in which energetic or informational masking predominate were investigated. DPOAEs were evoked from 500–4000 Hz with primary tones swept in frequency at 8 s/oct, using a fixed f2/f1 ratio of 1.22 at 65/55 dB sound pressure level. The MOC reflex and MOC‐shift were measured at DPOAE fine structure maxima at 948 and 1091 Hz with and without CAS. An inverse fast‐Fourier transform was performed to evaluate MOC effects on individual DPOAE components. Preliminary data analyzes showed MOC activity to be correlated with masked thresholds for both indices of medial efferent function. Most notably, higher masked thresholds for the random and broadband conditions were associated with a stronger MOC reflex for DPOAE maxima around 948 Hz. These results suggest that MOC activation plays a role in selective listening.

Personal Music Systems: Do They Pose Risk for Hearing Loss?

The proliferation of personal music systems in recent years raises concern because of the tremendous quantity of audio stimulation that users – especially children are exposed to. Hearing loss induced by personal music systems may evolve into a significant social and public health problem in future years. Currently, in our lab we are assessing the relationship among music listening habits of young adults, output sound pressure levels of different personal music systems and their effect on the auditory system, using behavioral and physiological measures. Our results show that about 66% of young adults listen to music using personal music systems for more than 1 hour a day. About 27% of these individuals report some kind of ontological problems. Measurement of output sound pressure levels of personal music system showed that about 20% of users listen to music at sufficiently high levels to cause permanent hearing loss. Pure tone audiogram and otoacoustic emissions revealed that listening to music through personal music system at preferred volume control settings did not result in “clinically significant” elevation of hearing thresholds or reduction of otoacoustic emissions amplitudes but caused subtle pre-clinical damage to the auditory system and over the years such behavior may be hazardous to hearing.

Realistic simulations of the Galactic polarized foreground: consequences for 21-cm reionization detection experiments

Experiments designed to measure the redshifted 21~cm line from the Epoch of Reionization (EoR) are challenged by strong astrophysical foreground contamination, ionospheric distortions, complex instrumental response and other different types of noise (e.g. radio frequency interference). The astrophysical foregrounds are dominated by diffuse synchrotron emission from our Galaxy. Here we present a simulation of the Galactic emission used as a foreground module for the LOFAR- EoR key science project end-to-end simulations. The simulation produces total and polarized intensity over $10^\circ \times 10^\circ$ maps of the Galactic synchrotron and free-free emission, including all observed characteristics of the emission: spatial fluctuations of amplitude and spectral index of the synchrotron emission, together with Faraday rotation effects. The importance of these simulations arise from the fact that the Galactic polarized emission could behave in a manner similar to the EoR signal along the frequency direction. As a consequence, an improper instrumental calibration will give rise to leakages of the polarized to the total signal and mask the desired EoR signal. In this paper we address this for the first time through realistic simulations.

The Actions of Dopamine Receptors in the Guinea Pig Cochlea

Dopamine, a major lateral olivocochlear efferent neurotransmitter, exerts both excitatory and inhibitory effects on the central nervous system depending on the receptor involved. We investigated the effects of different dopamine receptors on the cochlea by perilymphatic perfusion with D_1/5, D₂ and D₃ receptor agonists and antagonists and recording neural and hair cell responses (compound action potential – CAP; summating potential – SP) before, during and after perfusions. The D_1/5 agonist resulted in marked suppression of CAP amplitudes whilst leaving SP amplitudes unchanged, suggesting an inhibitory action of these receptors on afferent dendrites. The D_1/5 antagonist had little or no effect, suggesting that there is no influence of tonic dopamine release on these receptors. In contrast, perfusing a D₂ receptor antagonist resulted in marked suppression of CAP suggesting an excitatory action of the receptors and a strong influence of tonic dopamine release on the D₂ receptors. The D₂ agonist had little effect, implying that tonic dopamine release is maximally activating this class of dopamine receptors. D₂ antagonists resulted in reduction of SP, cochlear microphonic and distortion product otoacoustic emission amplitudes, suggesting that D₂ receptor action is not confined to afferent dendrites. Perfusion with D₃ agonists and antagonists had no effect.

Following a chemical reaction using high-harmonic interferometry

The study of chemical reactions on the molecular (femtosecond) timescale typically uses pump laser pulses to excite molecules and subsequent probe pulses to interrogate them. The ultrashort pump pulse can excite only a small fraction of molecules, and the probe wavelength must be carefully chosen to discriminate between excited and unexcited molecules. The past decade has seen the emergence of new methods that are also aimed at imaging chemical reactions as they occur, based on X-ray diffraction, electron diffraction or laser-induced recollision--with spectral selection not available for any of these new methods. Here we show that in the case of high-harmonic spectroscopy based on recollision, this apparent limitation becomes a major advantage owing to the coherent nature of the attosecond high-harmonic pulse generation. The coherence allows the unexcited molecules to act as local oscillators against which the dynamics are observed, so a transient grating technique can be used to reconstruct the amplitude and phase of emission from the excited molecules. We then extract structural information from the amplitude, which encodes the internuclear separation, by quantum interference at short times and by scattering of the recollision electron at longer times. The phase records the attosecond dynamics of the electrons, giving access to the evolving ionization potentials and the electronic structure of the transient molecule. In our experiment, we are able to document a temporal shift of the high-harmonic field of less than an attosecond (1 as = 10(-18) s) between the stretched and compressed geometry of weakly vibrationally excited Br(2) in the electronic ground state. The ability to probe structural and electronic features, combined with high time resolution, make high-harmonic spectroscopy ideally suited to measuring coupled electronic and nuclear dynamics occurring in photochemical reactions and to characterizing the electronic structure of transition states.

A note on single soft scalar emission of $$ \mathcal{N} = 8 $$ SUGRA and E 7(7) symmetry

We study single soft scalar emission amplitudes of $\mathcal{N}=8$ supergravity (SUGRA) at the one-loop level using an explicit formula for one-loop amplitudes in terms of tree amplitudes, which in turn are evaluated using supersymmetric BCFW recursion relations. It turns out that the infrared finite parts of all such amplitudes vanish in the soft momentum limit, which supports the conjecture that $E_{7(7)}$ symmetry has no anomalies at the one-loop level.

Spontaneous otoacoustic emissions measured using an open ear-canal recording technique

Spontaneous otoacoustic emissions (SOAEs) and synchronized spontaneous otoacoustic emissions (SSOAEs) were recorded using both the standard closed-canal method of recording and a novel open-canal method which involved suspending the probe at the entrance to the ear canal with no occluding tip. In both conditions, a probe tube microphone was inserted down the ear canal to measure the acoustic pressure near the tympanic membrane. Open- and closed-canal recordings were obtained in twelve otologically normal ears, all of which exhibited SSOAEs, and 6 of which exhibited SOAEs. The results were analysed to identify any differences in response to frequency and amplitude. The different recording conditions appeared to have no significant effect on SOAE or SSOAE frequency, suggesting little effect on the SOAE generator within the cochlea. Below about 2 kHz, the amplitude for both types of emission was less for the open-canal recording when compared to the closed-canal recordings. Above 2 kHz, SSOAE amplitudes were greater in the open- than the closed-canal condition. Model stimulations of the ear canal and middle-ear acoustics are presented which were in qualitative agreement with the results shown for the effects on emission amplitudes.

Human liver autofluorescence: An intrinsic tissue parameter discriminating normal and diseased conditions

Autofluorescence (AF) emission is an intrinsic parameter that can provide real-time information on morpho-functional properties of biological tissue, being strictly related with their biochemical composition and structural organization. The diagnostic potentials of AF-based techniques have been investigated on normal, fibrotic, and steatotic liver tissues, in reference to histological features as evidenced by specific histochemical stainings. AF emission under excitation at 366 nm has been examined on cryostatic tissue sections obtained from biopsies collected during surgical operation, by means of fluorescence imaging and microspectrofluorometric techniques. NAD(P)H, collagen, and vitamin A were found to be the endogenous fluorophores characterizing normal, fibrotic, and steatotic liver tissue AF, respectively. The differences of their photo-physical properties, in terms of emission amplitude, spectral shape, and response to irradiation, give rise to modifications of overall AF signal collected from tissues that allow the liver conditions to be distinguished. The study provides a valid premise for a development of AF-based optical biopsy techniques for a real-time discrimination of liver anatomo-pathological patterns.

Short-term Auditory Effects of Listening to an MP3 Player

To determine the output levels of a commercially available MPEG layer-3 (MP3) player and to evaluate changes in hearing after 1 hour of listening to the MP3 player. First, A-weighted sound pressure levels (measured in decibels [dBA]) for 1 hour of pop-rock music on an MP3 player were measured on a head and torso simulator. Second, after participants listened to 1 hour of pop-rock music using an MP3 player, changes in hearing were evaluated with pure-tone audiometry, transient-evoked otoacoustic emissions, and distortion product otoacoustic emissions. Twenty-one participants were exposed to pop-rock music in 6 different sessions using 2 types of headphones at multiple preset gain settings of the MP3 player. Output levels of an MP3 player and temporary threshold and emission shifts after 1 hour of listening. The output levels at the full gain setting were 97.36 dBA and 102.56 dBA for the supra-aural headphones and stock earbuds, respectively. In the noise exposure group, significant changes in hearing thresholds and transient-evoked otoacoustic emission amplitudes were found between preexposure and postexposure measurements. However, this pattern was not seen for distortion product otoacoustic emission amplitudes. Significant differences in the incidence of significant threshold or emission shifts were observed between almost every session of the noise exposure group compared with the control group. Temporary changes in hearing sensitivity measured by audiometry and otoacoustic emissions indicate the potential harmful effects of listening to an MP3 player. Further research is needed to evaluate the long-term risk of cumulative noise exposure on the auditory system of adolescents and adults.

D1D5 microstate geometries from string amplitudes

We reproduce the asymptotic expansion of the D1D5 microstate geometries by computing the emission amplitudes of closed string states from disks with mixed D1D5 boundary conditions. Thus we provide a direct link between the supergravity and D-brane descriptions of the D1D5 microstates at non-zero string coupling. Microscopically, the profile functions characterizing the microstate solutions are encoded in the choice of a condensate for the twisted open string states connecting D1 and D5 branes.

Vortices in atomic wave functions

Vortices in atomic wave functions are shown to have observable consequences. It is shown that time-dependent electron wave functions in coordinate space go over to electron emission amplitudes in the limit that time becomes infinite. This relation between wave functions and emission amplitudes is called the imaging theorem. According to this theorem vortices in wave functions at small times when particles interact in a complex way appear as vortices in electron momentum distributions where they produce observable features. Conversely, some observable structures may be interpreted in terms of vortices no matter how they are seen or computed. We verify that previously unexplained features in (e,2e) triply differential cross sections can be interpreted in terms of vortices.

Quantitative experimental measurements of matrix cracking and delamination using acoustic emission

Quantitative measurements of the amplitude and angular variation of acoustic emission (AE) events due to matrix cracking and delamination in large quasi-isotropic composite plate specimens are reported. A procedure for determining the minimum specimen size necessary to make quantitative measurements is presented. The amplitude of AE events is quoted as the absolute surface displacement of different guided wave modes and can therefore be used as the input to forward models of the AE process. Matrix cracking events are found to be dominated by the S 0 guided wave mode and have a pronounced amplitude variation with angle. Events due to delamination growth are dominated by the A 0 guided wave mode and have no clear angular dependence.

Audiological and transient evoked otoacoustic emission findings in patients with vitiligo

Objective To investigate hearing loss in patients with vitiligo. Study Design Case-control study. setting University hospital. subjects and Methods Conventional pure-tone and high-frequency audiometric tests were obtained, and pure-tone average hearing thresholds were calculated for 22 consecutive cases with vitiligo and 22 sex- and age-matched controls. Transient evoked otoacoustic emission testing was also performed. Results There was sensorineural hearing loss on pure-tone audiogram in 16 (36.4%) ears in patients with vitiligo. The hearing thresholds (in dB) were 16.02 ± 6.61 versus 12.39 ± 6.05, 15.68 ± 6.34 versus 13.18 ± 3.75, 15.80 ± 13.93 versus 7.39 ± 6.95, 25.11 ± 17.40 versus 15.91 ± 12.91, 29.89 ± 18.57 versus 17.84 ± 12.36, and 45.91 ± 23.31 versus 33.86 ± 15.99 in the patient and control groups at 0.25, 1, 4, 8, 10, and 12.5 kHz, respectively, and were statistically significantly different. Reduction of transient evoked otoacoustic emission amplitude was statistically significant at 4 kHz in patients with vitiligo (6.34 ± 3.98 dB vs 8.63 ± 5.15 dB, P = 0.023). There was no significant difference in reproducibility, stimulus intensity, stability, and average transient evoked otoacoustic emission amplitudes in patients with vitiligo. Conclusion Hearing thresholds at pure-tone and high-frequency audiometry were higher in patients with vitiligo. Also, significantly lower high-frequency amplitudes were recorded during transient evoked otoacoustic emission testing in the disease group.

Loops in the gluon emission amplitude: reggeization from the eikonal scattering

It is shown that in the Glauber scattering of a fast quark in the external field loop corrections to the gluon emission amplitude due to virtual softer gluon after renormalization coincide with a correction due to reggeization of the exchanged gluon in the BFKL picture.

Transient-evoked and distortion product otoacoustic emissions: A short-term test-retest reliability study

Knowledge regarding the variability of transient-evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) is essential in clinical settings and improves their utility in monitoring hearing status over time. In the current study, TEOAEs and DPOAEs were measured with commercially available OAE-equipment in 56 normally-hearing ears during three sessions. Reliability was analysed for the retest measurement without probe-refitting, the immediate retest measurement with probe-refitting, and retest measurements after one hour and one week. The highest reliability was obtained in the retest measurement without probe-refitting, and decreased with increasing time-interval between measurements. For TEOAEs, the lowest reliability was seen at half-octave frequency bands 1.0 and 1.4 kHz; whereas for DPOAEs half-octave frequency band 8.0 kHz had also poor reliability. Higher primary tone level combination for DPOAEs yielded to a better reliability of DPOAE amplitudes. External environmental noise seemed to be the dominating noise source in normal-hearing subjects, decreasing the reliability of emission amplitudes especially in the low-frequency region.SumarioEs esencial conocer la variabilidad de las emisiones otoacústicas evocadas por transitorios (TEOAEs) y por productos de distorsión (DPOAEs) en ambientes clínicos para mejorar su utilidad en el monitoreo de la condición auditiva en el tiempo. En este estudio se midieron TEOAEs y DPOAEs con equipo de OAE comercialmente disponible en 56 oídos normales durante tres sesiones. La confiabilidad se analizó en el retest sin re-colocar la sonda, en el retest inmediato con recolocación de la sonda y con mediciones después de una hora y una semana. La mayor confiabilidad se obtuvo en el retest sin recolocación de la sonda y disminuyó a aumentar el intervalo entre mediciones. Con TEOAEs la confiabilidad más baja se observó en bandas de frecuencia en 1.0 y 1.4 kHz mien-tras que para las DPOAEs también la banda de frecuencia de media octava de 8 kHz tuvo también confiabilidad pobre. La combinación de niveles tonales primarios superiores con DPOAEs, llevó a una mejor confiabilidad de las amplitudes de las DPOAEs. El ruido ambiental externo parece ser la fuente de ruido dominante en sujetos normales, disminuyendo la confiabilidad de las amplitudes de la emisión, especialmente en la región de las frecuencias graves.