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PubMed1991

Interaction of spatial frequency and separation in vernier acuity.

There are two general theories which attempt to explain the ability to judge the relative positions of objects in the visual field. The first is the "local-sign" model which assigns location to individual features of the stimulus. The other is the "channel" model involving pooling of responses of overlapping filters having different spatial frequency and orientation tuning. We set out to investigate these using vernier stimuli whose frequency content could be controlled. The stimuli consisted of vertically orientated sinusoidal gratings placed one above the other with a variable separation between them. Thresholds for high frequency gratings increased rapidly with separation while low frequencies were little affected. In addition the cycle width of gratings which could just be distinguished as being in or out of phase and of gratings which gave optimum vernier acuity both increased linearly with separation. Results are discussed in terms of a model based on spatial frequency filters and we suggest that our findings place significant constraints upon a local-sign model.

Contrast Sensitivity↗
PubMed2004

The interaction of formant frequency and pitch in the perception of voice category and jaw opening in female singers.

This study represents a first step toward understanding the contribution formant frequency makes to the perception of female voice categories. The effects of formant frequency and pitch on the perception of voice category were examined by constructing a perceptual study that used two sets of synthetic stimuli at various pitches throughout the female singing range. The first set was designed to test the effects of systematically varying formants 1 through 4. The second set was designed to test the relative effects of lower frequency formants (F1 and F2) versus higher frequency formants (F3 and F4) through construction of mixed stimuli. Generally, as the frequencies of all four formants decreased, perception of soprano voice category decreased at all but the highest pitch, A5. However, perception of soprano voice category also increased as a function of pitch. Listeners appeared to need agreement between all four formants to perceive voice categories. When upper and lower formants are inconsistent in frequency, listeners were unable to judge voice category, but they could use the inconsistent patterns to form perceptions about degree of jaw opening.

Acoustics↗
PubMed2004

[Why does the general practitioner overlooks psychological disorders in his patient?].

Physicians have a major screening function in the care of patients suffering from psychological disorders. Often, psychosocial disorders are overlooked in primary care. The study presented here investigates factors correlating with the identification of psychosocial disorders in primary care. Physician-patient consultations of 120 patients with psychological disorders of 16 primary care practices were analyzed with respect to doctor-patient interactions using Structured Analysis of Social Behavior (SASB). In addition, reported complaints, length of consultations and identification of psychological disorders by the physicians were analyzed. The physicians identified 60.8 % of the psychological disorders. There was a significant association between physician's identification of psychological disorders and (1) the severity of the disorder, (2) the number of complaints reported during consultation (3) the pattern of physician-patient interaction. A high frequency of interaction patterns referred to as complementary and controlling in terms of SASB categories, interferes with identification of psychological disorders. The study shows that the interactional process during primary care consultation is associated with physicians' identification of psychological disorders.

Adult↗
PubMed2003

Interaction of low frequency electric fields with the nervous system: the retina as a model system.

The retina provides an example of effects, the visually perceived 'phosphenes', being generated in nervous tissue by external electric or magnetic fields of low frequency and intensity. What is known about the cellular mechanisms by which the phosphenes are generated is reviewed, whether they provide useful information for setting limits on the magnitude of induced electric fields to which nervous tissue can be safely exposed is assessed, and some difficulties in translating these values of internal fields into safe values of external electric or magnetic fields are considered.

Animals↗
PubMed1970

Conjugation in Escherichia coli: interactions affecting recombination frequencies for markers situated at the leading end of the donor chromosome.

Experiments have been performed to test the validity of a model which relates low recovery of very early donor markers in recombinants to the presence of sex-factor deoxyribonucleic acid at the leading end of donor deoxyribonucleic acid transferred by conjugation. This model has been found to be incorrect. The results obtained do not rule out the possibility that a piece of sex factor is transferred at the leading end, but indicate, however, that if this occurs it is not the cause of the low recovery of a very early donor marker.

Chromosome Mapping↗
PubMed2006

Can one TV show make a difference? Will & Grace and the Parasocial Contact Hypothesis.

Television has an opportunity to influence beliefs about groups with which individuals typically may have little direct social contact. This study describes a synthesis of the Contact Hypothesis and the concept of Parasocial Interaction to pose what we call the Parasocial Contact Hypothesis to test whether exposure to gay men on Will & Grace can influence attitudes toward gay men in general. Based on a study of 245 university students, this study examines the relationships among number and intimacy of gay social contacts, parasocial interaction, viewing frequency of Will & Grace, and scores on Herek's Attitudes Toward Gay Men and Lesbians scale. Increased viewing frequency and parasocial interaction were found to correlate with lower levels of sexual prejudice-a relationship that was most pronounced for those with the least amount of social contact with lesbians and gay men.

Adolescent↗
PubMed1997

Modeling ruminal pH fluctuations: interactions between meal frequency and digestion rate.

A steady periodic analysis of ruminal carbohydrate digestion was developed to predict the effects of diet and frequency of eating on ruminal pH fluctuation. Tests of the model against previous data showed that pH fluctuations were too large when previously published rates of carbohydrate digestion were used but were improved using rates from an in vitro gas production system, which were lower. With the original digestion rates, the minimum meal frequency to maintain steady-state conditions in the rumen increased from 4 to 12 meals/d as dietary effective neutral detergent fiber (NDF) decreased from 34 to 6% of dry matter (DM); with the revised rates, the minimum frequency was 3 to 6 meals/d, respectively. The minimum effective NDF to maintain a pH value above 6.0 increased from 14 to 23% of DM as meal frequency decreased from steady state to 2 meals/d using the original rates; with the revised rates, the minimum effective NDF was slightly smaller, increasing from 13 to 21% of DM, respectively. Effects of DM intake and body weight on pH fluctuation were minor, and dietary buffers, when used at rates less than 1%, did not reduce fluctuation. Different methods of calculating mean ruminal pH yielded different results for the effect of meal frequency on mean pH.

Animals↗
PubMed1993

Type and frequency of social interaction among workers with and without mental retardation.

The social/verbal interactions of 6 employees with moderate or severe mental retardation and 6 workers without mental retardation were observed in six restaurants. Results showed that target workers without mental retardation gave more directions, asked more work-related questions, initiated more jokes, and had more general work-related comments than did target workers with mental retardation. The latter received more greetings and social amenities. Interactions between workers with mental retardation and the job coach correlated negatively with the workers' initiation of interactions with co-workers who did not have mental retardation. Implications for job placement and training as well as future research needs were discussed.

Adult↗
PubMed2005

Characterization of degree frequency distribution in protein interaction networks.

In this work, we analyze the degree frequency distribution in the yeast protein interaction network by studying a previously proposed duplication network model. This model correctly predicts the observed degree distribution (a power law for large degree values and a departure from this behavior for small degree). We numerically and analytically characterize this distribution as a mixture of random and power-law behavior, and make a comparative study of the robustness of the network model against realistic perturbations. We conclude that the particular distribution observed in both the model and the experimental data has many advantages in terms of dynamical and topological robustness and could have emerged in the evolutionary history as a sort of compromise between purely deterministic and random underlying mechanisms of network growth.

Computer Simulation↗
PubMed1981

The effects of neuroleptic drugs on the social interactions of hospitalized psychotic patients.

The frequency of social interactions emitted by two groups of hospitalized psychotic patients was studied with a time sampling procedure during lunch periods in the ward dayroom. One group was treated with neuroleptic medication upon admission to the ward, and the other group was medicated after a 2- to 3-week washout period. The data suggest that the principle effect of the medication is to produce a transient depression in social interaction frequency which returns to baseline with continued drug treatment. The results are supportive of previous research which indicated that the major impact of pharmacotherapy is on activity rather than social behaviors, and highlights the utility of including baseline measures to ensure adequate drug vs. control comparisons.

Adult↗
PubMed2003

Mechanisms of interaction of extremely low frequency electric fields and biological systems.

This article reviews mechanisms of interaction between extremely-low frequency (ELF) fields and biological systems. The emphasis is on simple quantitative models, supplemented by results of more detailed computer analysis. Scaling relations are reviewed which underlie the coupling of external fields to the inside of the body, and of extracellular fields to potentials induced in cell membranes. The relation between time domain and frequency thresholds for stimulating excitable tissues is reviewed, based on the work of Reilly. A range of thermal and non-thermal interaction mechanisms are reviewed, with respect to the question of possible effects of weak ELF fields in biological systems. Each mechanism is characterised by a threshold field strength (below which no observable response is produced) and dynamics; in each case, the anticipated in situ tissue strengths for producing observable effects are far higher than the range of 'weak' fields considered in this review. However, the bioeffects literature is unclear in many places, with numerous speculations about possible mechanisms for weak field effects and many reports of effects that are not clearly interpretable in terms of the mechanisms discussed in this article.

Animals↗
PubMed2005

New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 1. Assessment of van der Waals interactions.

Solvent effects on OH stretching vibrations in several complexes with hydrogen bonding have been investigated by FTIR spectroscopy. To assess the influence of van der Waals (vdW) interactions on frequency shifts, a new parameter of solvent, square root deltacavhS, is proposed. This parameter has been derived from equations describing enthalpy of non-specific solvation. Linear correlation was established between the OH frequency shift (with respect to the gas phase) and parameter square root deltacavhS for a series of complexes of aliphatic alcohols with standard proton acceptors. Linear correlations with square root deltacavhS were also observed for a series of "free" O-H and also C=O, P=O, S=O and C-Br stretching vibrations. A new method is proposed for estimating the gas-phase stretching frequency from IR spectra of solutions. In addition, frequencies of "free" X-H groups in neat bases were deduced from the experimental data.

Chemical Phenomena↗
PubMed1994

Modelling induced currents in biological cells exposed to low-frequency magnetic fields.

Interactions of low-frequency magnetic fields with biological systems have been a subject of intense scientific inquiry and public concern. Most research has been done at powerline frequencies of 50 Hz or 60 Hz. One of the key questions related to interactions of low-frequency magnetic fields with biological systems is which parameters of the exposure field are responsible for observed effects. Knowledge of the induced electric field and current in various experimental in vitro systems is important for this purpose. The 3D impedance method is used in this research to model spatial patterns of induced electric fields and current in two preparations of cells. A cell monolayer with a random distribution of cells and a confluent monolayer of cells with gap junctions are considered; because of the limitations of the computational method, biological cells are represented by cubes rather than more realistic shapes (e.g. spheres). The random model indicates that for higher cell densities the pattern of the induced current flow has a limited dependence on the size and shape of the container in which the cells are placed, it depends mostly on the actual cell placement. Gap junctions, not surprisingly, are shown to increase the current density, but only if their resistance is sufficiently low. The highest current density occurs in the gaps.

Animals↗
PubMed2005

Dual-frequency 2D IR on interaction of weak and strong IR modes.

Dual-frequency 2D IR heterodyne photon-echo spectroscopy of C[triple bond]N and C=O stretching vibrational modes in 2-cyanocoumarin is reported. We have shown that the interaction among these modes provides convenient and useful structural constraints for molecules. Implementation of two pulse sequences, 4, 4, and 6 microm and 6, 6, and 4 microm, allowed the clear determination of contributions caused by vibrational relaxation. Positive correlation between C[triple bond]N and C=O frequency distributions was observed in 2-cyanocoumarin. Because C[triple bond]N modes are highly localized and have frequencies in a spectral region with minimal water absorption, the C[triple bond]N/C=O interactions have a strong potential for use as structural reporters in proteins. In addition to CN/CO peaks, the cross-peaks responsible for the C[triple bond]N/C=C interaction are also observed in the 2D IR spectra, where C=C is a coumarin ring stretching mode. We have demonstrated that 2D IR spectroscopy can utilize interactions of strong IR modes with weak local modes as structural reporters.

Journal Article↗
PubMed2003

Study into mechanisms of the enhancement of multibubble sonoluminescence emission in interacting fields of different frequencies.

The main factor of the enhancement of sonoluminescence (SL) emission by the interaction of two fields of highly different frequencies is the generation of new cavitation nuclei upon collapse of bubbles driven by the low-frequency (LF) field. The factors connected with the direct interaction of the two fields play a significant role in the enhancement of SL emission only in the case when intensities of the fields are less or not much higher than the corresponding thresholds of SL emission. The phenomena of afteraction of the LF field on cavitation generated by the high-frequency field is explained also by the generation of new nuclei upon collapse of bubbles driven by the LF fields.

Journal Article↗
PubMed1987

Interaction of extremely low frequency electric and magnetic fields with humans.

The dosimetry and physical interaction mechanisms of electromagnetic fields with frequencies in the extremely low frequency (ELF) range (below 300 Hz) are described. The mechanisms through which ELF electric and magnetic fields induce electric currents in living organisms are summarized, with particular emphasis on humans. Topics that are discussed include: (1) sources and measurements of ELF electric and magnetic fields; (2) direct and indirect coupling of these fields to humans; (3) transient discharges and contact currents, and the thresholds for human response to these phenomena; (4) protective measures for the mitigation of potential ELF field effects on humans; and (5) mechanisms of interaction of ELF fields with cellular and tissue systems, with emphasis on field transduction mechanisms involving the cell membrane.

Electricity↗