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PubMed1981

Responses of auditory-nerve fibers to characteristic-frequency tones and low-frequency suppressors.

Responses of single auditory-nerve fibers to combinations of low-frequency (suppressor) and characteristic frequency (CF) tones were recorded. The shapes of period histograms were observed as the level of the suppressor was raised. For fibers with CFs above 5.0 kHz, at the lowest suppressor levels used, the phase of the suppressor tone which caused instantaneous rate to increase when presented alone caused a rate decrease when added to a CF tone. For suppressor frequencies of 500 and 100 Hz, as suppressor level is increased, two peaks appear in the period histograms. Further increase in level causes first one, then the other of these peaks to disappear and the histogram takes on the shape of the histogram to the suppressor alone. A similar progression of histogram shape follows a decrease in CF tone level for fixed suppressor level.

Acoustic Stimulation↗
PubMed1987

Formulae describing frequency selectivity as a function of frequency and level, and their use in calculating excitation patterns.

The auditory filter may be considered as a weighting function representing frequency selectivity at a particular centre frequency. Its shape can be derived using the power-spectrum model of masking which assumes: (1) in detecting a signal in a masker the observer uses the single auditory filter giving the highest signal-to-masker ratio; (2) threshold corresponds to a fixed signal-to-masker ratio at the output of that filter. Factors influencing the choice of a masker to measure the auditory filter shape are discussed. Narrow-band maskers are unsuitable for this purpose, since they violate the assumptions of the power-spectrum model. A method using a notched-noise masker is recommended, and typical results using that method are presented. The variation of the auditory filter shape with centre frequency and with level, and the relationship of the auditory filter shape and the excitation pattern are described. A method of calculating the excitation pattern of any sound as a function of level is presented, and examples and applications are given. The appendix gives a Fortran program for calculating excitation patterns.

Auditory Perception↗
PubMed2005

Measuring alcohol consumption: a comparison of graduated frequency, quantity frequency, and weekly recall diary methods in a general population survey.

OBJECTIVE: The objective of this study is to compare self-reports of alcohol consumption obtained by graduated frequency (GF), quantity frequency (QF), and prospective weekly diary methods in a Swiss general population survey using a within-subject design. Another objective is to examine the consumption means, ranking order, and drinking classifications and to relate differences in consumption means and classification inconsistencies to social and drinking characteristics. METHOD: The data came from the first wave of a longitudinal study on changes in alcohol consumption. A subsample of 767 respondents who completed the three measures was examined. The sample design was accounted for. RESULTS: Weekly drinking diary (WDD) yielded over 50% more alcohol consumption than the QF and GF measures did. Measures on quantity and graduated frequencies did not differ significantly. There were more light drinkers found on QF and more harmful drinkers on the WDD. Classification inconsistencies between GF and the weekly drinking diary were significantly related to gender and problematic drinking.

Adolescent↗
PubMed2005

The use of generic failure frequencies in QRA: the quality and use of failure frequencies and how to bring them up-to-date.

Quantitative Risk Assessment (QRA) is a method which is often used in the chemical industry and, in some countries, also in land-use planning. In QRA calculations the frequency of an accident scenario is most often assessed by a generic failure frequency approach. The credibility and validity of the failure frequencies used in the Netherlands for land-use planning is evaluated by means of an historical review. Furthermore, the possibility is presented how these generic data can be revised and updated.

Accidents, Occupational↗
PubMed1999

Neural source estimation from a time-frequency component of somatic evoked high-frequency magnetic oscillations to posterior tibial nerve stimulation.

OBJECTIVE: High frequency oscillations (HFOs) evoked by posterior tibial nerve stimulation were recorded using magnetoencephalography (MEG). Time-frequency domain multiple signal classification (TF-MUSIC) algorithm was applied, and the usefulness of this method was demonstrated. METHODS: Ten normal subjects were studied. To localize sources for the HFOs of those somatosensory evoked fields, we applied two kinds of methods: the single moving dipole (SMD) method and the TF-MUSIC method. The SMD method was applied after digitally band-pass filtering the somatosensory response with a bandwidth of 500-800 Hz. To estimate the locations of sources with the TF-MUSIC algorithm, we first set the target region on the spectrogram of the somatosensory responses. Then, the procedure described in Section 2.2 was applied with this target region. RESULTS: A clear, isolated region was detected in 6 out of 10 subjects using a time-frequency spectrogram. The averaged distance of the dipole sources between the HFOs and the underlying P37m using the TF-MUSIC algorithm was smaller than using the SMD method. CONCLUSIONS: The TF-MUSIC algorithm is suitable for extracting a target response whose spectrum changes significantly during the observation.

Adult↗
PubMed2002

[Frequency of oral hygiene nursing in cancer patients in Belgian hospitals. Frequency of nursing interventions and indicators].

This article describes the frequency of mouth care for cancer patients in Belgian hospitals. It also analyses the indicators used for this specific type of compensatory nursing care. The study was designed as a secondary data analysis of the 1990 Belgian Nursing Minimum Data set. The randomised sample included 35,347 oncology patients. Frequency of mouth care was 10.3%. The most important indicators were ventilation (70.58%), nasogastric tube (55.01%), endotracheal tube (43.17%), isolation of the patient (40.57%), malignant neoplasmas of lip, cavity and pharynx (40.21%), age younger than 8 years (37.06%) and disorientation of the patient (31.49%). Frequency of mouth care increased with a higher qualification of staff and higher staffing ratios.

Adolescent↗
PubMed1977

Variables of color, duration, frequency, presentation order, and sex in the estimation of dot frequency.

The estimation of number depends on the information as dot frequency, exposure conditions, order of presentation, and sensitivity of the observer to color. Ninety-six color-normal observers (age 17-27) equally divided by sex were assigned so that each one viewed 42 cards, each of which contained dots of one of three colors on one of two grounds at one of seven frequency levels. For any observer, cards were exposed for either .5 second or 1.0 second intervals and in either ascending or descending order. The ANOVA indicated a significant effect for the following variables: dot frequency, dot color, and exposure time. Estimates increased with dot number on the several displays. Yellow-red (YR) dots were slightly overestimated. Yellow-green (YG) and gray dots were not. The briefer exposure yielded an underestimation and the longer an overestimation. Interpolated intervals are given for correct estimates.

Adolescent↗
PubMed1977

Frequencies of mitogen-reactive B cells in the mouse. II. Frequencies of B cells producing antibodies which lyse sheep or horse erythrocytes, and trinitrophenylated or nitroiodophenylated sheep erythrocytes.

The B-cell mitogens LPS and lipoprotein stimulate 20-35 percent of all B cells in the spleen of 6- to 8-wk old C3H/Tif mice, as determined by limiting dilution analysis of precursors. Each reactive cell grows to a clone of IgM-secreting PFC, enumerated in a hemolytic plaque assay detecting all IgM secreting cells, regardless of v-region specificity. We have used these mitogens to reveal the total repertoire of Ig specificities produced by these mitogen-reactive B cells. We have determined in plaque assays with six different target erythrocytes the number of spleen cells limiting to one the number of mitogen-reactive B cells detected as specific IgM-secreting clones in each of these plaque assays. By this method, the absolute frequencies of precursor B cells with defined v-gene specificities could be calculated, for at least, one third of all B cells. The frequencies of specific IgM-plaque-forming B-cell clones within the total pool of mitogen-reactive B cells was 1 in 10 for NIP(12),-SRC, 1 in 50 for TNP(12)- SRC, 1 in 100 for NIP(1)-SRC, 1 in 160 for TNP(3)- SRC, 1 in 500 for HRC, and 1 in 1,000 for SRC. These frequencies were the same in the LPS- and in the lipoprotein-reactive B-cell population for TNP(30)- SRC and SRC.

Animals↗
PubMed2006

Electrical impedance tomography in extremely prematurely born infants and during high frequency oscillatory ventilation analyzed in the frequency domain.

Functional electrical impedance tomography (EIT) measures relative impedance change that occurs in the chest during a distinct observation period and an EIT image describing regional relative impedance change is generated. Analysis of such an EIT image may be erroneous because it is based on an impedance signal that has several components. Most of the change in relative impedance in the chest is caused by air movement but other physiological events such as cardiac activity change in end expiratory level or pressure swings originating from a ventilator circuit can influence the impedance signal. We obtained EIT images and signals in spontaneously breathing healthy adults, in extremely prematurely born infants on continuous positive airway pressure and in ventilated sheep on conventional mechanical or high frequency oscillatory ventilation (HFOV). Data were analyzed in the frequency domain and results presented after band pass filtering within the frequency range of the physiological event of interest. Band pass filtering of EIT data is necessary in premature infants and on HFOV to differentiate and eliminate relative impedance changes caused by physiological events other than the one of interest.

Adult↗
PubMed2006

Time-frequency analysis reveals decreased high-frequency oscillations in writer's cramp.

High-frequency oscillations (HFO) have been suggested to reflect the activity of thalamocortical and/or intracortical neurons bursting at high frequencies. These circuits seem to be involved in pathophysiological mechanisms of focal dystonia. In healthy subjects, we characterized the spectrotemporal properties of HFO patterns evoked by dominant-hand median-nerve stimulation, using magnetoencephalography coupled with time-frequency analysis. Then, we investigated HFO in patients with writer's cramp and found that HFO patterns are strongly decreased in power and disorganized in time. This supports the assumption that abnormal HFOs reflect pathophysiological mechanisms occurring in focal dystonia, possibly resulting from a dysfunction of somatosensory processing.

Adult↗
PubMedDate not supplied

Quantitation of T-cell receptor frequencies by competitive polymerase chain reaction: dynamics of T-cell clonotype frequencies in an expanding tumor-infiltrating lymphocyte culture.

The use of T-cell receptor (TCR) genes as markers for antigen-reactive T cells is dependent on the ability of the TCR genes to rapidly identify antigen-reactive T-cell clonotypes in patient samples. We recently reported a competitive reverse-transcriptase polymerase chain reaction (cRT-PCR) method that can measure the frequency of individual TCRBV subfamilies and clonotypes in mixed lymphocyte populations more accurately than other semiquantitative PCR assays. However, it is impractical to measure changes in the absolute frequency of each TCRBV subfamily to identify those T cells with increasing frequency after antigen stimulation in vivo or in vitro. Therefore, we have modified our cRT-PCR method to more rapidly identify expanding T-cell populations by combining all of the TCRBV subfamily-specific competitors into a single sample to determine the relative abundance of each TCRBV subfamily. Using an expanding TIL 620 culture, we identified four TCRBV (BV2, BV12, BV17, and BV23) subfamilies that expanded over a 23-day period. These subfamilies accounted for 23% of the T cells in the day 35 culture and increased to 57%, 92%, and 80% of the days 44, 51, and 58 cultures respectively. Analysis of DNA sequences demonstrated that the observed expansion was caused primarily by a single clonotype within each subfamily. T cells expressing BV17 and BV23 recognized gp100 and MART-1 respectively. Therefore, this cRT-PCR method can detect expanding T-cell populations based solely on their TCRBV subfamily expression. Furthermore, T-cell expansion in a mixed TIL population was a good predictor of antigen reactivity.

Antigens, Neoplasm↗
PubMed2004

Frequency entrainment in long chains of oscillators with random natural frequencies in the weak coupling limit.

We study oscillator chains of the form phi; (k) = omega(k) +K[Gamma( phi(k-1) - phi(k) )+Gamma( phi(k+1) - phi(k) )], where phi(k) epsilon[0,2pi) is the phase of oscillator k. In the thermodynamic limit where the number of oscillators goes to infinity, for suitable choices of Gamma(x), we prove that there is a critical coupling strength K(c), above which a stable frequency-entrained state exists, but below which the probability is zero to have such a state. It is assumed that the natural frequencies are random with finite bandwidth. A crucial condition on Gamma(x) is that it is nonodd, i.e., mid R: Gamma(x)+Gamma(-x) mid R: not equal 0. The interest in the results comes from the fact that any chain of limit-cycle oscillators can be described by equations of the above form in the limits of weak coupling and narrow distribution of natural frequencies.

Journal Article↗
PubMed2005

Multistage chemical etching for high-precision frequency adjustment in ultrahigh-frequency fundamental quartz resonators.

Chemical etching to precisely adjust and to make uniform the thicknesses of vibrating areas of multiple resonators in a single wafer was applied to inverted-mesa quartz resonators exciting an ultrahigh-frequency fundamental thickness vibration. The process consisted of five stages, combining high-rate etching for high productivity and low-rate etching for high-precision adjustment. By using this process, the resonance frequencies of 41 resonators in the single wafer were adjusted to 620 +/- 1.5 MHz, which corresponds to vibrating area thicknesses of 2.2 microm +/- 6 nm. In the temperature-frequency characteristics of these resonators in the single wafer, the difference between the maximum first-order temperature coefficient and the minimum first-order temperature coefficient was equivalent to a cut angle change of two arcminutes. In addition, vibrating areas with an arithmetic mean surface roughness of 0.17 nm on the concave side were produced by this multistage etching.

Journal Article↗
PubMed2006

Development of a real-time, high-frequency ultrasound digital beamformer for high-frequency linear array transducers.

A real-time digital beamformer for high-frequency (>20 MHz) linear ultrasonic arrays has been developed. The system can handle up to 64-element linear array transducers and excite 16 channels and receive simultaneously at 100 MHz sampling frequency with 8-bit precision. Radio frequency (RF) signals are digitized, delayed, and summed through a real-time digital beamformer, which is implemented using a field programmable gate array (FPGA). Using fractional delay filters, fine delays as small as 2 ns can be implemented. A frame rate of 30 frames per second is achieved. Wire phantom (20 microm tungsten) images were obtained and -6 dB axial and lateral widths were measured. The results showed that, using a 30 MHz, 48-element array with a pitch of 100 microm produced a -6 dB width of 68 microm in the axial and 370 microm in the lateral direction at 6.4 mm range. Images from an excised rabbit eye sample also were acquired, and fine anatomical structures, such as the cornea and lens, were resolved.

Computer Systems↗
PubMed2001

Formant-frequency matching between sounds with different bandwidths and on different fundamental frequencies.

The two experiments described here use a formant-matching task to investigate what abstract representations of sound are available to listeners. The first experiment examines how veridically and reliably listeners can adjust the formant frequency of a single-formant sound to match the timbre of a target single-formant sound that has a different bandwidth and either the same or a different fundamental frequency (F0). Comparison with previous results [Dissard and Darwin, J. Acoust. Soc. Am. 106, 960-969 (2000)] shows that (i) for sounds on the same F0, introducing a difference in bandwidth increases the variability of matches regardless of whether the harmonics close to the formant are resolved or unresolved; (ii) for sounds on different F0's, introducing a difference in bandwidth only increases variability for sounds that have unresolved harmonics close to the formant. The second experiment shows that match variability for sounds differing in F0, but with the same bandwidth and with resolved harmonics near the formant peak, is not influenced by the harmonic spacing or by the alignment of harmonics with the formant peak. Overall, these results indicate that match variability increases when the match cannot be made on the basis of the excitation pattern, but match variability does not appear to depend on whether ideal matching performance requires simply interpolation of a spectral envelope or also the extraction of the envelope's peak frequency.

Adult↗
PubMed2005

Effect of frequency-modulation coherence for inharmonic stimuli: frequency-modulation phase discrimination and identification of artificial double vowels.

The ability to compare patterns of frequency modulation (FM) in separate frequency regions was explored. In experiment 1, listeners had to distinguish whether the FM applied to two nonharmonically related sinusoidal carriers was in phase or out of phase. The FM rate was the same for each carrier. The starting phase of the modulation was randomized for each stimulus in a three alternative, forced-choice (3AFC) trial. Subjects were sensitive to relative FM phase for modulation rates of 2 and 4 Hz, but not for higher rates. In experiment 2, vowel identification was compared for artificial single and double vowels. The vowels were constructed from complex tones with components spaced at 2-ERB(N) (equivalent rectangular bandwidth) intervals, by increasing the levels of three components by 15 dB, to create three "formants." In the double vowels, the components of the two vowels were interleaved, to give 1-ERB(N) spacing. The three "formant" components were frequency modulated at 2, 4, or 8 Hz, with either the same or different rates for the two vowels. The identification of double vowels was not improved by a difference in FM rate across vowels, suggesting that differences in FM rate do not support perceptual segregation of inharmonic stimuli.

Acoustic Stimulation↗