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Results for “interaction frequencies”

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PubMed1991

Endurance time and physiological responses to prolonged arm lifting.

The main objective of this study was to examine the effects of prolonged arm lifting tasks on endurance time and physiological responses. Ten male college students participated in the study. The independent variables were the frequency of handling and weight of load. The dependent variables were endurance time, oxygen consumption, minute ventilation, heart rate, and ratings of perceived exertion of the shoulder, arm, back, leg and overall body. The results indicated that: (1) endurance time decreased with an increase in frequency or load; (2) oxygen consumption and heart rate limits were dependent on the interaction of frequency and load; (3) oxygen consumption and heart rate limits for arm lifting were generally lower than limits for leg lifting tasks; and (4) for arm work, average physiological responses recorded over short durations were not significantly different from those based on long durations.

Adult↗

PubMed1998

Natural killer cell frequency and function in pigs selectively bred for high or low antibody and cell-mediated immune response: response to vaccination with modified live transmissible gastroenteritis virus.

Porcine NK cells are small to medium lymphocytes which are lytic for tumours and virally infected cells when co-cultured for long periods ( approximately 16 h). The frequency and function of NK cells were examined in generation 8 of pigs genetically selected for high (H), low (L), and control (C) antibody (Ab) and cell-mediated immune response (CMIR). The NK phenotype was identified using a pan-species NK-specific murine monoclonal antibody (5C6) and both binding and lysis of the NK target, K562. Vaccination with modified live transmissible gastroenteritis virus (TGEV) had no effect on blood leucocyte NK cell frequency. In interactions with K562 targets, NK cells of H and C pigs responded similarly in frequency of conjugate formation and lytic activity, while L pigs had very little or no response. Therefore, in pigs selected for high Ab and CMIR, there was no correlated enhancement of NK-cell-related traits following vaccination with TGEV, while selection for low immune response was associated with reduced NK response in pigs. This may suggest that low immune response can reflect reduced contribution of NK cells in pigs.

Analysis of Variance↗

PubMed1997

Linear and nonlinear spectral integration in type IV neurons of the dorsal cochlear nucleus. II. Predicting responses with the use of nonlinear models.

Two nonlinear modeling methods were used to characterize the input/output relationships of type IV units, which are one principal cell type in the dorsal cochlear nucleus (DCN). In both cases, the goal was to derive predictive models, i.e., models that could predict the responses to other stimuli. In one method, frequency integration was estimated from response maps derived from single tones and simultaneous pairs of tones presented over a range of frequencies. This model combined linear integration of energy across frequency and nonlinear interactions of energy at different frequencies. The model was used to predict responses to noisebands with varying width and center frequency. In almost all cases, predictions using two-tone interactions were better than linear predictions based on single-tone responses only. In about half the cases, reasonable quantitative fits were achieved. The fits were best for noisebands with narrow bandwidth and low sound levels. In the second nonlinear method, the spectrotemporal receptive field (STRF) was derived from responses to broadband stimuli. The STRF could account for some qualitative features of the responses to broad noisebands and spectral notches embedded in broad noisebands. Quantitatively, however, the STRFs failed to predict the responses of type IV units even to simple broadband noise stimuli. For narrowband stimuli, the STRF failed to predict even qualitative features (such as excitatory and inhibitory frequency bands). The responses of DCN type IV units presumably result from interactions of two inhibitory sources, a strong one that is preferentially activated by narrowband stimuli and a weaker one that is preferentially activated by broadband stimuli. The results presented here suggest that the STRF measures effects related to the broadband inhibition, whereas two-tone interactions measure mostly effects related to narrowband inhibition. This explains why models based on two-tone interactions predict the responses to narrow noisebands much better then models based on STRFs. It is concluded that a minimal stimulus set for characterizing type IV units must contain both broadband and narrowband stimuli, because each stimulus class by itself activates only partially the integration mechanisms that shape the responses of type IV units. Similar conclusions are expected to hold in other parts of the auditory system: when characterizing a complex auditory unit, it is necessary to use a range of stimuli to ensure that all integration mechanisms are activated.

Acoustic Stimulation↗

PubMed1990

Frequency, intensity, and target matching effects on photoglottographic measures of open quotient and speed quotient.

Measurements of Open Quotient (OQ) and Speed Quotient (SQ) were made from photoglottographic signals of normal male subjects during phonation. Samples were obtained at spontaneous levels of fundamental frequency and intensity, and at nine specified frequency/intensity combinations. OQ increased with fundamental frequency. OQ change was not significant for change in intensity and there was no significant interaction between frequency and intensity. Changes in SQ with variations of frequency and intensity were not significant. However, SQ did increase significantly when spontaneous phonation was compared to target matching phonation at similar frequency/intensity. Changes in both OQ and SQ across comfortable frequency and intensity ranges were relatively small in comparison to changes in OQ and SQ reported for pathological phonation.

Adult↗

PubMed2001

Functional dependence and quasiperiodicity in the spatiotemporal dynamics of yttrium iron garnet films.

When thin films of yttrium iron garnet (YIG) are placed in a magnetic field and driven at microwave (rf) frequencies, nonlinear interactions within the material cause the normal microwave spin precession to be modulated at lower frequencies. We measure these lower frequency (kHz) signals at two spatially separated locations on the YIG film and use linear and nonlinear analysis to study the functional dependence of the spin dynamics at one location on the spin dynamics at the other location. We see dynamical states where nonlinear analysis can detect a functional dependence that the linear analysis fails to reveal.

Journal Article↗

PubMed1980

Binaural interaction of a beating frequency-following response.

Frequency-following responses to 500-Hz tone bursts presented to the left ear and 540-Hz tone bursts presented to the right ear were recorded from human subjects. Recordings were made both under monaural and binaural conditions. The responses summed over monaural conditions (for left and right ear stimulation) were larger than the responses obtained in the binaural condition. This binaural interaction shows that the frequency-following response reflects binaural processing probably occurring at or below the level of the inferior colliculi.

Acoustic Stimulation↗

PubMed2000

NMR relaxation in multipolar AMX systems under spin-locking conditions

A relaxation network has been calculated for multipolar AMX systems under application of a spin-locking RF field. Systems of this type are of interest in the study of proteins with fractional (2)H enrichment. All possible auto- and cross-correlation terms involving dipolar, quadrupolar, and CSA interactions have been taken into account. The results show the presence of spectral densities at zero frequency for interactions associated with the locked nuclei, which are nonvanishing in the absence of fast motions. In addition, the application of a spin-locking field blocks certain cross-correlation interactions, thereby considerably simplifying the relaxation network. Copyright 2000 Academic Press.

Journal Article↗

PubMed1998

Sources of error in bioimpedance spectroscopy.

Two different makes of bioimpedance spectrometer (UniQuest-SEAC SFB-3 and Xitron 4000B) were used for a series of measurements on volunteers and patients in intensive care. Although each machine was accurate over the frequency range 5 to 500 kHz when bench tested on model resistor-capacitor circuits, significant differences in their recorded impedance parameters appeared when used in vivo, especially on intensive care patients. A series of laboratory tests was performed on each machine simulating the situation in vivo to identify possible reasons for these differences. Whilst stray capacitance in the environment was identified as the major contributor to variability in high-frequency performance, interaction between electrode impedance and lead positioning was also a factor. The observed phase shift with frequency or time delay (Td) used in the Xitron modeling software appears to be the result of a time constant caused by stray capacitance and so is unlikely to have any biological meaning. Significant differences in the in vivo numerical values produced by bioimpedance spectrometers may be attributed to instrument design, data processing and, in particular, the clinical environment.

Adult↗

PubMed1997

Effect of stimulus level and frequency on ABR and MLR binaural interaction in human neonates.

Auditory brainstem (ABR) and middle latency (MLR) responses were evoked by click and tone-burst stimuli from human neonates. Electrophysiologic evidence of binaural interaction was measured by subtracting waveforms obtained for binaural stimulus conditions from waveforms obtained for the sum of right ear monaural and left ear monaural stimulus conditions. The effects of stimulus level and stimulus frequency on binaural interaction were evaluated by measuring the number, latency and amplitude of components found in the derived binaural interaction waveform, that is, binaural interaction components (BIC). BICs were more prevalent in the latency range of ABRs than for MLRs. Click and tonal stimuli were equally effective for deriving ABR-BICs, while tone-bursts were somewhat less effective than clicks for deriving MLR-BICs. Stimulus-response dependencies for ABR and MLR component latencies were apparent in monaural, binaural and binaural interaction waveforms. Normalized amplitudes for BICs showed that low-frequency tone-burst stimuli resulted in the largest values compared to click and high-frequency tonal stimuli. Comparison of these results with published results from adults demonstrated immaturity of binaural interaction in neonates.

Acoustic Stimulation↗

PubMed1996

Frequency-Dependent Stability for Two-Species Interactions

Evolutionary game theory is extended to models of two-species interactions where fitnesses are based on individual characteristics (strategies) rather than on a population dynamic that assumes homogeneous species. It is shown that the coevolutionary theories in the literature that combine ecology with genetic viability selection are part of this extended theory and that the dynamic stability resulting from a separation of ecological and evolutionary processes actually follows from game-theoretic solution concepts. The main focus of the paper is to investigate the application of the ESS (evolutionarily stable strategy) solution concept to dynamic stability when fitnesses are given by random interactions between individuals as opposed to viability selection. For two-species frequency-dependent interactions, the ESS criterion that implies stability asserts that, in any system near the ESS, at least one of the species is better off (i.e., more fit) if it evolves towards the ESS. The global stability of a polymorphic two-species ESS that is shown for two-species matrix games gives a powerful tool to predict the course of evolution through static fitness comparisons.

Journal Article↗

PubMed2004

Spatial variation in frequency and intensity of antibiotic interactions among Streptomycetes from prairie soil.

Antibiotic interactions are believed to be significant to microbial fitness in soil, yet little is known of the frequency, intensity, and diversity of antibiotic inhibition and resistance among indigenous microbes. To begin to address these issues, we studied the abilities of streptomycete isolates from prairie soil to inhibit growth and display resistance to antibiotics produced by a test collection of 10 streptomycete isolates. Wide variations in antibiotic inhibition and resistance for prairie isolates among three locations and four soil depths within a 1-m2 plot were revealed. Fewer than 10% of 153 prairie isolates inhibited all 10 test isolates, while more than 40% of the isolates did not inhibit any of the test isolates. No field isolate was resistant to all of the test isolates, nor was any isolate susceptible to all of the test isolates. No correlation between inhibition and resistance phenotypes was found, suggesting that inhibition and resistance are under independent selection. The significant spatial variation in the frequency and intensity of antibiotic inhibition implies that the fitness benefits of antibiotic production are not the same among locations in soil. In contrast, the consistency of resistance over space indicates that its significance to fitness across locations is stable or the costs of maintaining resistance in the absence of selection are small or nonexistent. The spatial clustering of antibiotic inhibitory activity suggests a variable matrix of selection pressures and microbial responses across the soil landscape.

Anti-Bacterial Agents↗

PubMed1999

Age of acquisition, word frequency, and the role of phonology in the lexical decision task.

In five experiments, we examined the respective roles of word age of acquisition (AoA) and frequency in the lexical decision task. The two variables were manipulated orthogonally (while controlling for concreteness and length) in fully factorial designs. Experiment 1 was a conventional lexical decision task, and Experiments 2-5 involved various attempts to interfere with reliance upon phonology. In Experiment 2, only orthographically illegal nonwords were used; in Experiment 3, pseudohomophone nonwords; in Experiment 4, articulatory suppression by the recitation of a nursery rhyme; and in Experiment 5, articulatory suppression by the repetition of a single word. The same basic pattern of results was observed in all experiments: There were main effects of both AoA and frequency, which interacted in such a way that the AoA effect was larger for low- than for high-frequency words. Although the AoA effect was reduced by manipulations intended to interfere with phonological processing, the manipulations did not eliminate the effect. The results are discussed in terms of current models of reading in which it is proposed that AoA has its primary effect on the retrieval of lexical phonology, which appears to be consulted automatically in the lexical decision task.

Adult↗

PubMed2026

Dissecting contributions of directional and balancing selection to trajectories of mitochondrial haplotype evolution in Drosophila melanogaster.

Emerging evidence suggests mtDNA haplotypes contribute to fitness variation and local adaptation, with directional thermal selection and negative frequency-dependent selection shaping haplotype diversity. However, their interplay remains unexplored. We conducted experimental evolution using Drosophila melanogaster populations from opposite ends of an Australian latitudinal cline (Melbourne and Townsville), exposing them to contrasting temperatures (17°C versus 27°C) and varying starting frequencies of two mtDNA haplotypes (A1 and B1) that occur at appreciable frequencies in these populations. We paired this with population genetic simulations to estimate selection and its influence on haplotype trajectories. Haplotype frequencies were influenced by interactions involving temperature, starting frequency, and nuclear genomic background (Melbourne, Townsville, or admixed). Although prior work predicted A1 should be favoured at the warmer temperature and B1 at the cooler temperature, A1 was generally favoured across both temperatures. Simulations supported directional selection in populations evolving at 17°C in the Melbourne background; otherwise dynamics were best explained by balancing selection shaped by negative frequency-dependent fitness effects. Patterns also varied across nuclear backgrounds, suggestive of mito-nuclear epistasis. These findings challenge a simple thermal adaptation model of mtDNA dynamics, suggesting that mtDNA evolution is shaped by interacting effects of temperature, frequency-dependence, nuclear background and experimental environment.

adaptation↗

PubMedDate not supplied

Frequency discrimination for bands of noise.

Recoding of speech in order to improve discrimination for profoundly deaf people has been tried in various ways. One of these is frequency transposition of voiceless consonants. Some authors report positive and very promising results. Others, however, have not found any significant difference when using control groups with normal amplification. One reason might be a poor frequency discrimination. Is it possible to establish what minimum hearing capacity the listener must show for a successful use of frequency transposition? Using noise bands with different Q factors and varying the levels, the thresholds as minimum midfrequency shift have been measured. Great individual variations have been shown. There is a significant difference between (1) threshold values at different Q factors, (2) threshold values at different frequencies, and (3) threshold values for increasing and decreasing frequency, position of deltaf. There is a significant interaction between (1) frequency and position of deltaf, (2) Q factor and position of deltaf, and (3) between Q factor and frequency. There is also a significant triple interaction between Q factor, frequency, and position of deltaf.

Acoustic Stimulation↗

PubMed2000

Effects of word frequency and spelling-to-sound regularity in naming with and without preceding lexical decision.

The effects of word frequency and spelling-to-sound regularity were examined using standard naming, standard lexical-decision, go/no-go naming, and go/no-go lexical-decision tasks. In both the standard and go/no-go naming tasks, tasks requiring phonological coding, a significant Frequency x Regularity interaction was observed. That is, the regularity effect was limited to low-frequency words. In the standard and go/no-go lexical-decision tasks, tasks not requiring phonological coding, no Frequency x Regularity interaction was observed. These results indicate not only that the Frequency x Regularity interaction is a product of phonological coding processes but also that these processes are similar in the standard and go/no-go naming tasks. Results are discussed in terms of the dual-route and the parallel distributed processing frameworks.

Adult↗

PubMed1985

Interaction of 5-hydroxytryptamine and ketanserin in rat vas deferens subjected to low frequency field stimulation.

The interaction of 5-hydroxytryptamine (5HT) and ketanserin was investigated in isolated rat vas deferens. Ketanserin (10(-7) M) almost completely abolished the phasic and the following rhythmic contractions induced by 5HT, whereas the inhibition by prazosin (10(-6) M) or methysergide (10(-6) M) of 5HT-induced contractions were incomplete. The amplitude of twitch contractions of vas deferens subjected to low frequency (0.1 Hz) field stimulation were substantially unchanged by 5HT (10(-7)-10(-5) M) per se. After pretreatment of the tissue with ketanserin (10(-8)-10(-6) M), 5HT, in a concentration-dependent manner, attenuated the amplitude of twitch contractions. Such attenuation of the amplitude was not observed after pretreatments with methysergide (10(-8)-10(-6) M) or prazosin (10(-7)-10(-5) M). The 5HT-induced inhibition of twitch contractions in the presence of ketanserin was not antagonized by phentolamine, propranolol, methysergide, morphine, promethazine, cimetidine, atropine or indomethacin. It is suggested that 5HT has dual (excitatory and inhibitory) effects upon nerve transmission of rat vas deferens, and only the excitatory effect is suppressed by ketanserin.

Animals↗

PubMed1984

The mechanism of 3-aminobenzamide-mediated increases in spontaneous and induced SCEs.

Cells exposed to the poly-(ADP-ribose)-polymerase inhibitor, 3-aminobenzamide (3AMB), have increased levels of sister chromatid exchanges (SCEs). In addition, cells exposed to certain monofunctional alkylating agents in combination with 3AMB have frequencies of SCEs much greater than expected if the 2 agents acted independently. Because poly-(ADP-ribose)-polymerase is stimulated by the production of DNA strand breaks, and 3AMB is said to inhibit strand-break rejoining, we determined the relationship between DNA strand breakage and SCE formation. Alkylating agents and the incorporation of bromodeoxyuridine (BrdUrd) into DNA led to the production of DNA strand breaks and the most potent SCE-inducing agents were also the most efficient DNA strand-breaking agents. In increasing SCE frequency, 3AMB interacted most strongly with those agents that produced the greatest number of DNA strand breaks. 3AMB also increased the frequency of strand breaks by delaying strand-break rejoining and introducing new strand breaks. The protease inhibitor, antipain, inhibited the formation of 3AMB-induced strand breaks in BrdUrd-containing cells and reduced by half the 3AMB-mediated increase in SCE frequency, suggesting that one mechanism for SCE induction involves the introduction of breaks into DNA possibly in response to changes in chromatin structure. We conclude that the primary lesion responsible for SCE induction after exposure to alkylating agents or incorporation of BrdUrd into DNA is either a DNA strand break or a lesion that can result in a strand break. 3AMB increases SCE frequency in combination with these agents by introducing new breaks and possibly delaying strand-break rejoining.

Alkylating Agents↗

PubMed2003

Peer interaction and loneliness in high-functioning children with autism.

Social interaction with peers and the understanding and feelings of loneliness were examined in 18 high-functioning children with autism and 17 typically developing children matched for IQ, chronological age, gender, and maternal education. Observations were conducted on children's spontaneous social initiations and responses to their peers in natural settings such as recess and snack time, and children reported on their understanding and feelings of loneliness and social interaction. Overall, children with autism revealed a good understanding of both social interaction and loneliness, and they demonstrated a high level of social initiation. However, they spent only half the time in social interactions with peers compared with their matched counterparts, and they interacted more often with a typically developing child than with another special education child. Despite the intergroup differences in frequency of interaction, a similar distribution of interactions emerged for both groups, who presented mostly positive social behaviors, fewer low-level behaviors, and very infrequent negative behaviors. Children with autism reported higher degrees of loneliness than their typical age-mates, as well as a lower association between social interaction and loneliness, suggesting their poorer understanding of the relations between loneliness and social interaction. Research and practice implications of these findings are discussed.

Adolescent↗