Threshold shift

Standard threshold shift (STS) An increase of 10 dB or more in a person s HTL in the 2000 to 4000 Hz range, significant because it represents loss of a significant proportion of hearing. 

Temporary threshold shift (TTS) A temporary shift in hearing threshold level that goes away after the person has been in a quiet environment for a few hours. It is confirmed by an audiogram retest following a suspected standard threshold shift (STS) after at least 14 hours away from high levels of noise. 

Palladium clusters deposited on amorphous carbon have been studied by XPS and UPS [28] and both techniques show broadening of the d-band peak as cluster size increases. The d-threshold shifts towards Ep as cluster size increases. In UPS studies the d-emission of the single atom has its peak at 3.0 eV below Ep, whereas the d-threshold is 2eV below Ep. Palladium clusters evaporated onto Si02 have been studied by UPS [38]. At large coverages of the Pd metal evaporated (> 10 atoms/cm ), a high emission intensity at Ep excited with photons of 21.2 eV (He(I)) or 40.8 eV (He(II)) as excitation source, is observed. This feature is characteristic in the spectra from bulk Pd samples. At the lowest metal coverage (3 x 10 atoms/cm ),... 

Gagnon P, Mergler D, Lapare S Olfactory adaptation, threshold shift and recovery at low levels of exposure to methyl isobutyl ketone (MIBK). Neurotoxicology 15(3) 637-642, 1994... 

Fig. 5. Observed hearing threshold shift (dB) at 1, 2 and 4 kHz versus measured unbound (upper panel) and total plasma quinine concentration in a subject who received a computer-controlled quinine infusion. The reduced sigmoid Fmax model has been applied and is shown as the solid line. Note that the y axis is hy definition a log scale. (From Karlsson KK, Beminger E, Gustafsson LL, Al-van G. Pronounced quinine-induced cochlear hearing loss. A mechanistic study in one volunteer at multiple stable plasma concentrations. J Audiol Med 1995 4 12-24, with permission.)...

Fig. 6. Counterclockwise hysteresis appearing between hearing threshold shift and quinine plasma concentration in a subject who received two identical oral doses (dotted and solid lines) and an infusion (dashed line) of quinine. (From Paintaud G, Alvan G, Beminger E et al. The concentration-effect relationship of quinine-induced hearing impairment. Clin Pharmacol Ther 1994 55 317-23, with permission from MOSBY Inc.)...

Fig. 11.11. Voltage threshold shift as a function of time for conventionally processed (open circles) and digital lithographically processed (closed diamonds) TFT. Conventionally processed TFT data from Ref. [1].

Figures 15a and 15b summarize the results for the threshold shifts after the 1 -Mrad and 5-Mrad irradiations. The shift A VT is plotted against VG, the gate voltage applied during the irradiation. In spite of the scatter of experimental points, results for the 1-Mrad dose show a tendency toward a small negative threshold shift for both positive and negative VG. This is consistent with observations made on crystalline devices, and it is possible that a similar mechanism is responsible in both cases. However, Fig. 15b for a dose of 5 Mrad shows a predominantly positive AVT, suggesting that other mechanisms begin to play a part during the longer irradiation period.

Fig. 6.32. Time dependence of the induced defect density near the dielectric interface of a field effect transistor after the application of a gate bias. The measurement is of the threshold shift, AK, which is proportional to the defect density (Jackson and Moyer 1988).

The metastable defect creation mechanism affects the TFTs, since defects are created when the device is held in accumulation for an extended time. Fortunately the defect creation rate is low near room temperature, so that the resulting threshold shift is less than 0.1 V and is not much of a problem. The threshold voltage shifts very rapidly at elevated temperatures, by several volts in a few minutes at about 100 °C, so that the TFTs cannot be used in high temperature applications. 

Fechter, L.D., Young, J.S., Carlisle, L. (1988). Potentiation of noise-induced threshold shifts and hair cell loss by carbon monoxide. Hear. Res. 34 39-48. 

Compared with aminoglycosides, which caused significant loss of hair cells in the basal turn of the cochlea, ofloxacin caused no loss of hair cells in rats, even at concentrations higher than are achieved clinically (5). Moreover, auditory brainstem testing showed no change in auditory thresholds in the ofloxacin-treated animals, whereas neomycin-treated animals showed substantial threshold shifts. In human studies, topical ofloxacin 0.3% had no demonstrable adverse effects on middle ear or cochlear function and was not associated with any changes in hearing. 

Nakagawara VB, Montgomery RW, Dillard A, McLin L, and Connor CW (2003) The effects of laser illumination on operational and visual performance of pilots conducting terminal operations. DOT/FAA/AM-03/12. Niskar A, Kieszak S, Holmes A, et al. (2002) Estimated prevalence of noise-induced hearing threshold shifts among children 6 to 19 years of age The Third National Health and Nutrition Examination Survey 1988-1994. Pediatrics 109 987-988. 

As discussed in Section 13.3 concurrent exposure to noise and some organic solvents and solvent mixtures is ototoxic. Styrene is an example of an ototoxic compound, with exposures to it causing permanent hearing threshold shifts and outer hair cell damage. Ethanol alone does not affect auditory sensitivity, yet, when combined with styrene it induces hearing and outer hair cell losses in test animals in levels greater than those caused by styrene alone. The potentiation of the ototoxicity of styrene by ethanol is ascribed to the altering of styrene metabolism by ethanol. 15 ... 

Photooxidation experiments with other small olefins add strong support to the assignment of the visible absorption of hydrocarbon 02 complexes in zeolites as charge-transfer absorptions [19,20]. For example, the onset of the absorption tail (and the photolysis threshold) shifts linearly to higher energies with increasing ionization potential of the olefin. We have also found that, as expected, the optical absorption onset is sensitive to the magnitude of the electrostatic field. For example, the increase of the electrostatic field upon substitution of Na by Ba is accompanied by a red shift of the 2-butene 02 absorption onset of 100 nm (4000 cm-1) [14]. 

The observed threshold shift of AVj = 2.0 V results in a trap density t= 2.4 X lO" traps/cm. This number is not so small eompared with the number of eharge carriers Wj, indicating that traps largely influence the device performance. One may speculate whether structural defects within the pentacene film contribute to trap states. An X-ray analysis of the defect densities in pentacene films revealed defect densities in the order of t=2xl0" defects/cm [44], in good agreement with the trap density inferred from the electronic characterisation. Thus, the observed structural defects apparently contribute to... 

For OFETs, stored at dark ambient atmosphere for a longer period of time without an applied bias field, the threshold shifted in the negative direction [42]. Regarding Table 18.3 and Figure 18.4, the influence of water seems to dominate the degradation of the OFETs in comparison with an oxygen atmosphere. 

It is unclear at this time how the light sensitivity of OTFTs compares to silicon-based TFTs, but it is certain that similar light-shielding measures must be employed. Studies in our laboratory have shown that, in addition to the photocurrents generated by incident illumination, long-lived light-induced threshold shifts can occur in pen-... 

Another typical feature of a-Si TFTs is that the threshold shift under on-bias is more rapid than the shift under off-bias. However, TFTs used as pixel switches are in the on-condition for much less time than they are in the off-condition. For example, in an SXGA display, the TFTs are on for about 0.1% of the time and off for about 99.9% of the time. As a result, the direction of the net threshold shift under actual usage conditions can depend on the fabrication details of the TFT and must be determined experimentally. In any case, because pixel TFTs are left in the more unstable on-condition for a low duty-cycle and because they are subject to the compensating effect of the off-condition, the shift of an a-Si pixel TFT over a typical 10,000-hour lifetime is small, at most a few volts. This is taken into aeeount by allowing some voltage margin in the select and deselect voltages applied to the select lines. 

An alarm system component such as a beU, buzzer, horn, speaker, light, or text display that provides an audible, visible, or tactile output to announce a condition of concern. Significant Threshold Shift (STS)... 

A vertical barrier erected along exposed edges of a floor opening, wall opening, ramp, platform, or runway to prevent the fall of an individual. See also Handrail. Standard Threshold Shift (STS)... 

STS Standard Threshold Shift or Signihcant Threshold Shift... 

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