Humans detect gaps in broadband noise according to effective gap duration without additional cues from abrupt envelope changes

Previous studies of behavior and IC single units in the mouse support theoretical expectations that gaps with ramped trailing markers have reduced detectability compared to equivalent gaps with ramped leading markers. In experiment 1, detection probability and response speeds of humans listening for gaps in broadband noise were investigated by independently varying either leading marker fall-time (FT) or trailing marker rise-time (RT). Gaps with silent duration of 1, 4, or 12 ms were presented 2 s into a 3-s noise burst, with either abrupt marker onsets and offsets or linearly ramped RT/FT of 2, 4, or 8 ms durations. Addition of a nonzero RT or FT to the gap silent period increased detectability and also increased reaction speed on trials with "Yes" response, but there was no difference in detectability or response speeds between RT and FT conditions. Experiment 2 extended this finding to gaps having two, one, or no abrupt marker edges. These findings suggest that human listeners do not make use of abrupt onset or offset information to enhance gap detection, but seem to rely on the effective sound level reduction associated with the gap for detection.     

The relative detectability for mice of gaps having different ramp durations at their onset and offset boundaries

The effect on gap detectability of varying noise fall time (FT) and rise time (RT) of the gap boundary ramps was examined in mice using reflex modification audiometry, measuring inhibition of acoustic startle reflexes by variously shaped gaps just preceding reflex expression. In experiment 1 (n = 12) inhibition increased up to near-asymptotic values with longer FT (0, 1, 2, 3, 5, or 10 ms) and QT (quiet time, 0 to 13 ms), with a 2:1 trade-off between FT and QT. In experiment 2 (n = 24) inhibition increased for any RT above 0 ms (2, 3, 5, or 7 ms) if QT= 1 ms, but diminished with increased RT when QT = 3 or 8 ms. Enhanced detectability for subthreshold gaps by longer ramps results from their extending the apparent gap duration. The negative effect of increased RT for threshold gaps suggests the importance for gap detection of the stronger neural responses to sharp edges at the end of the gap shown previously in the mouse inferior colliculus. These effects are specific to gaps: inhibition for fixed (70-dB SPL) or varied level pulses (30 to 60 dB) was unaffected by varying the ramped edges (experiments 3 and 4, n = 9).     

The attention filter for tones in noise has the same shape and effective bandwidth in the elderly as it has in young listeners

Listeners asked to detect tones masked by noise hear frequent signals but miss infrequent probes, suggesting that they attend to spectral regions where they expect the signals to occur. The narrow detection pattern centered on the frequent target approximates that obtained in notched noise, indicating that attention is focused on the auditory filter. We measured attention bands in young and elderly listeners (n=5, 4; 20-25 and 62-82 years of age) for targets (800 or 1200 Hz) and infrequent probe signals (target +/-25-100 Hz) masked in wideband noise. We anticipated that their width would increase with age, as has been reported for auditory filters. A yes-no single-interval procedure provided detection probabilities and detection response speeds. Both measures showed near-linear declines with decreasing signal level, and graded decay functions as probe frequency deviated from the target frequency. Probes deviating from the target by 25 to 50 Hz were equivalent to a 2-dB reduction in signal level for both measures. The equivalent rectangular bandwidth (ERB) for detection approximated 11% of the signal frequency for each age group. Confidence intervals (95%) showed that the elderly ERB could be at most only about 20% larger than that of younger listeners.     

Modeling of aortic valve dynamics in a lumped parameter model of left ventricular-arterial coupling

A lumped parameter model of the sub-system of left ventricle, aortic valve, systemic arteries, systemic capillaries and systemic veins was considered during systole. A model of aortic valve dynamics based solely on geometrical and kinematical consideration is defined. The model is described by two geometrical parameters of aortic valve and a few kinematical relationships. The proposed model mimics the incisures in the aortic flow and aortic pressure very well. We showed that the dicrotic notch could be explained by aortic valve closing in terms of a lumped parameter model, without a need for any wave reflection theory. According to the proposed model the effects of aortic valve dynamics on the aortic flow and pressure are mainly limited to the valve opening and closing periods. The model offers a new paradigm for defining a more realistic left ventricle model.      

Raman Micro-Spectroscopy of Dental Pulp Stem Cells: An Approach to Monitor the Effects of Cone Beam Computed Tomography Low-Dose Ionizing Radiation

The objective of this study was to determine the molecular and biochemical changes in dental pulp stem cells (DPSCs) due to consecutive low-dose ionizing radiation exposures using label-free Raman micro-spectroscopy (RMS). Ionizing radiation produces biological damage leading to health effects of varying severity. The effects and subsequent health implications caused by exposure to low-dose radiation, such as diagnostic exposure, remain ambiguous. We identified Raman biomarkers characteristic to low-dose cone beam computed tomography (CBCT) irradiation of the DPSCs. The biomarkers were monitored inside the cells using the relative intensity distribution of the 785 and 1734?cm^?1 bands. The control cells presented a higher relative intensity of the nucleic acid specific Raman bands, whereas the irradiated cells revealed an increased intensity of the lipid-induced bands. The results obtained in this study demonstrate the capability of RMS for the detection of cell response to diagnostic radiation dose levels. This may indicate the potential of the technique for future applications such as monitoring the radiation responses in pediatric patients suffering repeated radiological exposures.     

Quantitative ultratrace distribution analysis of tantalum wires with SIMS

Summary The potential of SIMS for multielement ultratrace bulk analysis in refractory metals has already been shown in previous publications [1, 2]. In this paper it will be demonstrated, that the high sensitivity of SIMS can be used advantageously for high resolution distribution analysis. Due to the high useful yield (0.5 to 10^–5) it is possible to perform distribution analysis in the ng/g range with a sample consumption of about 1 pg per data point. A good lateral resolution of about 1 m and the variability of the sputtering rate over 3 orders of magnitude allow an optimization of the measurement parameters with respect to the sample geometry. This is of special importance in our work, because small lateral dimensions, high total sputtering depth (300 m) and crooked surfaces have to be considered. In this paper also the technical significance of sensitive high resolution distribution analysis of tantalum wires, which are used for microelectronic applications, will be discussed.

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Quantitative Ultraspuren-Verteilungsanalyse von Tantaldrähten mit Hilfe von SIMS

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday