Most plants have the ability to respond to fluctuations in light to minimize damage to the photosynthetic apparatus. A proteolytic activity has been discovered that is involved in the degradation of the major light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCII) when the antenna size of photosystem II is reduced ...

Recognition of consonants, vowels, and sentences was measured in conditions of reduced spectral resolution and distorted spectral distribution of temporal envelope cues. Speech materials were processed through four bandpass filters (analysis bands), half-wave rectified, and low-pass filtered to extract the temporal envelope from each band. The envelope from each speech ...

The effect of a Bagolini lens on spatial vision was investigated by studying its far-field diffraction pattern as produced by a coherent beam of laser light, and its effect on the contrast sensitivity function (CSF) in human subjects. For lenses of the main type studied, which were crossed by a ...

The relative contributions of various regions of the frequency spectrum to speech recognition were assessed with a correlational method [K. A. Doherty and C. W. Turner, J. Acoust. Soc. Am. 100, 3769-3773 (1996)]. The speech materials employed were the 258-item set of the Nonsense Syllable Test. The speech was filtered ...

Barley (Hordeum vulgare L.) plants were grown at different photon flux densities ranging from 100 to 1800 &mgr;mol m-2 s-1 in air and/or in atmospheres with reduced levels of O2 and CO2. Low O2 and CO2 partial pressures allowed plants to grow under high photosystem II (PSII) excitation pressure, estimated ...

Detection thresholds were measured for silent temporal gaps within combinations of two, three, or four sinusoidal markers (i.e., combinations of one or two pre-gap markers with one or two post-gap markers). The markers were selected from the frequency range 2000-3100 Hz. Sinusoidal frequencies F1 and F4 were used as pre-gap ...

Measures of event-related band power such as event-related desynchronization (ERD) are conventionally analyzed within fixed frequency bands, although it is known that EEG frequency varies as a function of a variety of factors. The question of how to determine these frequency bands for ERD analyses is discussed and a new ...

These experiments were designed to test the hypothesis that glides in frequency are detected and discriminated by monitoring changes in excitation level on the low-frequency side of the excitation pattern. Thresholds were measured for detecting an increase in the extent of a frequency glide, for various standard extents (transition spans). ...

Monaurally measured temporal gap detection (TGD) thresholds characteristically increase as the frequency difference is increased over a range of about half an octave to an octave between two sinusoids that mark the onset and offset of the silent gap. For greater sinusoidal frequency separations, the TGD thresholds often become asymptotic. ...

A method is described for reversibly removing bacteriochlorophyll from the B800-site of the B850-850 antenna complex from Rhodobacter sphaeroides. This method uses the oligosaccharidic detergent Triton BG-10, together with an incubation at pH 5.0. Reconstitution at the B800-site has been successfully achieved for a range of modified bacteriochlorophylls. Copyright 1998 ...

Temporal gap detection thresholds were measured between perceptually dissimilar electrical markers in cochlear implant listeners. Both markers were presented to the same electrode pair. The amplitude and pulse rate of the first marker were fixed, and gap thresholds were measured as a function of either the pulse rate or the ...

Normal listeners were tested for their temporal auditory gap detection thresholds using free-field presentation of white-noise stimuli delivered from the left (L) and right (R) poles of the interaural axis. The noise bursts serving as the leading and trailing markers for the silent period were presented in either the same ...

The unicellular, diazotrophic cyanobacterium Cyanothece sp. ATCC 51142 demonstrated important modifications to photosystem II (PSII) centers when grown under light/dark N2-fixing conditions. The properties of PSII were studied throughout the diurnal cycle using O2-flash-yield and pulse-amplitude-modulated fluorescence techniques. Nonphotochemical quenching (qN) of PSII increased during N2 fixation and persisted after ...

Detection thresholds for either 500-Hz tones or 4-kHz tones were measured for a group of 19 listeners utilizing the interaural configurations NoSo and NoS pi. Both broadband (100-8500 Hz) noises and narrow-band (50-Hz-wide) noises served as maskers. In addition, direct measures of the listeners' sensitivities to changes in interaural temporal ...

Release of masking for a sinusoidal signal of 5 kHz masked by a 25-Hz-wide noise band centered around 5 kHz was measured. The masking release was provided by a second noise band that was comodulated with the on-frequency masker band. For CMR configurations the second noise band was centered at ...

The question is examined whether the extent of changes in relative band power as measured by event-related desynchronization (ERD) depends on absolute band power. The results for target stimuli of a simple oddball task indicate that the prestimulus (reference) level of absolute band power has indeed a strong influence on ...

A method for evaluating the spectral, temporal and combined spectral temporal resolution of hearing is presented; it was used to obtain masked hearing thresholds using the fixed frequency Békéy technique. The masking noise was a broadband random noise with a 3 dB/octave roll off (pink noise). Spectral resolution was assessed ...

Neural correlates of temporal resolution in the central auditory system are currently under intense investigation. The gap detection paradigm offers a simple, yet important, test of temporal acuity because changes in behavioral gap thresholds have been correlated with deficits in complex stimulus processing, such as speech perception. In gap detection ...

The study of the perception of loudness lends itself well to the psychophysical scaling technique of magnitude estimation. This study was designed to extend the range of auditory stimuli used to study the magnitude estimation scaling of loudness. The five stimuli chosen were a 1000-Hz pure tone, narrow band noise ...

Discrimination experiments were performed for a change in the spectral shape of noise bands. The subject's task was to discriminate noise bands with a positive spectral slope from those with a negative spectral slope. Thresholds were measured at several bandwidths and center frequencies, as well as for several noise samples. ...

In this study, the pattern-reversal visual evoked potentials (PRVEP's) collected from normal and demented subjects are investigated by applying the quadratic spline wavelet analysis. The data are decomposed into six octave frequency bands. For quantitative purposes, the wavelet coefficients in the residual waveform representing the delta-theta band activity (0-8 Hz) ...

The bioelectrical activity of the cochlea, without any ipsilateral acoustic stimulation, was recorded in awake guinea pigs (GPs) between electrodes chronically implanted at the round window (RW) and the skull. Measuring its power in the band centered around 1.0 kHz (0.5-2.5 kHz) provided an indirect measure of the ensemble background ...

We calculated the two-dimensional Fourier spectrum of a Landolt C. For Landolt Cs of orthogonal orientation, the main differences in the amplitude spectrum were found at a low frequency such that 1.3 periods were equal to the size fo the Landolt C, rather than at the high frequency corresponding to ...

Temporal resolution of hearing was studied in bottlenosed dolphins by recording the auditory brain-stem response (ABR) evoked by gap in noise. Gaps shorter than 0.5 ms evoked a response combining both off- and on-components; longer gaps evoked separate off- and on-responses. Both the response to a short gap and on-response ...

The principal neurons of the dorsal cochlear nucleus have complex response properties, many of which are classified as type IV. These units integrate energy in the acoustic signal in a nonlinear fashion; for example, at high sound levels the response to a noise of narrow bandwidth and to a band-reject ...

this study sought to characterize the integration of synchronous energy fluctuations across relatively independent spectral regions. The detection of four classes of signal was examined where each class of signal was associated with a change in energy over time. The four signal types were: (1) multicomponent tonal complexes, with each ...

The present study was based on earlier findings that the observation of a coherently moving long bar induced gamma-band activity in humans. The power in the EEG-gamma-band was reduced during the presentation of two incoherently moving short bars. The present study demonstrates the replicability of this cortical activity pattern and ...

The perception of sound is based on signal processing by a bank of frequency-selective auditory filters, the so-called critical bands. Here we investigate how the internal frequency organization of the main auditory midbrain station, the central nucleus of the inferior colliculus (ICC), might contribute to the generation of the critical-band ...

Brain processes elicited by speech were studied in 10 right-handed subjects by means of examining the desynchronization and synchronization of the 8-10 Hz and 10-12 Hz EEG alpha frequency bands. The subjects listened to an auditorily presented 5 min text passage. The text was presented both forward and backward. Listening ...

This article describes four experiments on gap detection by normal listeners, with the general goal being to examine the consequences of using noises in different perceptual channels to delimit a silent temporal gap to be detected. In experiment 1, subjects were presented with pairs of narrow-band noise sequences. The leading ...

The purpose of this investigation is to present evidence from experimental as well as model results on temporal variations of the frequency of oscillation in the basilar membrane's impulse response. Stimuli were either clicks leading to a direct estimate of the impulse response, or bands of pseudo-random noise (one or ...

Gap detection was measured for 50 and 1000-Hz-wide noise markers arithmetically centered on 1000 Hz. The markers were presented in a lowpass background noise having a high-frequency cutoff of 2000 Hz. The pressure spectrum level of the background noise was either 0 or 40 dB/Hz. Gap detection was determined at ...

In order to function effectively as a means of communication, speech must be intelligible under the noisy conditions encountered in everyday life. Two types of perceptual synthesis have been reported that can reduce or cancel the effects of masking by extraneous sounds: Phonemic restoration can enhance intelligibility when segments are ...

Thresholds were measured for discriminating changes in the slopes of the amplitude spectra of stimuli derived from photographs of natural scenes and from random-luminance patterns. The variety and magnitudes of the thresholds could be explained by a model based on the discrimination of the changes in band-limited local contrast. Different ...

A comparison betweeen the electropherograms of the spelt and wheat cultivars showed specific differences in the gliadin band patterns which provided the possibility of a clear classification into spelt or wheat. A special nomenclature was developed to be able to improve the presentation of the gliadin band pattern of spelt, ...

Two experiments were performed to investigate subjects' ability to detect and discriminate 50-ms up-glides in frequency in several different conditions. In the first experiment, the subjects indicated which of two signals increased more in pitch. The comparison, or standard signal, was a sinusoid which increased in frequency by either 0, ...

Intensity resolution of pure tones in a one-interval forced-choice paradigm was measured for experienced musicians under fixed- and uncertain-frequency conditions, and under uncertain-frequency conditions with informative cues as to target frequency. The uncertain frequency effect for intensity resolution, when present, was reduced or removed by frequency cueing, both with auditory ...

Ferrets were tested for their ability to detect temporal gaps in noise before and after bilateral lesions of the primary auditory cortex. Thresholds for gap detection were determined first for normal animals with band-pass noises at various center frequencies (0.5 to 32 kHz) and at 8 kHz with various sound ...

A role for the peripheral (B800-850) light-harvesting complex in vesicularization of the Rhodobacter sphaeroides intracytoplasmic membrane (ICM), suggested from studies in mutant strains lacking one or more of the pigment-protein complexes, was examined further in the wild-type strain NCIB 8253 grown at high ( approximately 1000 W m-2), moderate ( ...

Temporal gap detection was determined for single 20-Hz-wide noise bands having various center frequencies, and for simultaneously present pairs of noise bands where the spectral separation between center frequencies was varied. in most conditions, each noise band was present 30 dB above its detection threshold, but in some conditions, each ...

Optical methods of quantifying total hemoglobin (tHb), applying the principles of the Lambert-Beer law, have been used both on untreated whole blood and on blood mixed with chemicals to form a stable chromophore, since the earliest days of laboratory medicine. The same principles may be applied for quantitation of the ...

BACKGROUND AND AIM OF THE STUDY: Transient cavitation has been directly observed near operating mechanical heart valves in vitro and inferred in vivo via the observation of pitting on explanted clinically used valves. Visual detection of cavitation bubbles, however, cannot be accomplished in vivo or when any opaque fluid, e.g. ...

This study examines the ability to lateralize a complex signal characterized by correlated temporal activity across widely separated frequency regions. The high-frequency complex consisted of two narrow-band stimuli. The two stimuli had common interaural delays but different carriers centered on nonoverlapping critical bands. Two basic conditions were examined: The narrow-band ...

It has recently been proposed that brain responses in the gamma-range (> 20 Hz) include information about specific cognitive processes in the human brain. Empirical data substantiating this assumption come from EEG and MEG recordings during visual and language processing. For example, 30 Hz activity has been found to be ...

Nearly perfect speech recognition was observed under conditions of greatly reduced spectral information. Temporal envelopes of speech were extracted from broad frequency bands and were used to modulate noises of the same bandwidths. This manipulation preserved temporal envelope cues in each band but restricted the listener to severely degraded information ...

1. The spike interval pattern during the light responses of 155 on- and 81 off-centre cells of the dorsal lateral geniculate nucleus (LGN) was studied in anaesthetized and paralysed cats by the use of a novel analysis. Temporally localized interval distributions were computed from a 100 ms time window, which ...

Normal-hearing subjects participated in two CMR experiments. For experiment 1, two, three, five or nine 20-Hz-wide comodulated flanking bands were presented continuously or gated simultaneously with a 2000-Hz signal. The signal had a duration of 400 ms. Larger CMRs were obtained as the number of flanking bands increased for both ...

The notched-noise method has been widely used to estimate the shape of the auditory filter. Results obtained using this method may be influenced by combination bands produced by the interaction of components within the upper band of noise in the notched-noise masker. To assess the possible effect of such combination ...

The intelligibility of word lists subjected to various types of spectral filtering has been studied extensively. Although words used for communication are usually present in sentences rather than lists, there has been no systematic report of the intelligibility of lexical components of narrowband sentences. In the present study, we found ...

OBJECTIVE: This study investigated the intensive effects of a low-frequency (200 to 400 Hz) and a high-frequency (1000 to 5000 Hz) band of speech presented jointly and in isolation. DESIGN: Each band was presented at a reference intensity level equivalent to the average normal conversational level. To investigate intensive effects, ...