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PubMed2001

Evolutionary stability concepts for N-species frequency-dependent interactions.

The classical static concept of an evolutionarily stable strategy (ESS) for a single species gives rise to two new notions when there are more than two species (called an N-species ESS and RL-stability). The paper relates these to the dynamic stability of monomorphic and polymorphic evolutionary systems. It is shown that RL-stability implies the global asymptotic stability of either system with or without mutations. However, the N-species ESS only implies stability of the monomorphic system.

Animals↗
PubMed1999

Karlsburg Type I diabetes risk study of a general population: frequencies and interactions of the four major Type I diabetes-associated autoantibodies studied in 9419 schoolchildren.

AIMS/HYPOTHESIS: The Karlsburg Type I (insulin-dependent) diabetes risk study on schoolchildren aims to evaluate the predictive diagnostic value of diabetes-associated autoantibodies in the general population. METHODS: We took capillary serum from 9419 schoolchildren, aged 6-17 years, for testing of autoantibodies (AAbs) to glutamic acid decarboxylase (GADA), protein tyrosine phosphatase (IA2A) and insulin (IAA) by 125I-antigen binding. We also tested for autoantibodies to cytoplasmic islet cell antigens (ICA) immunohistochemically. RESULTS: By testing of 9419 sera for the four AAbs at cut-off at or greater than the 98th centile for the radioassayed AAbs and at or greater than 10 Juvenile Diabetes Foundation (JDF) units for ICA, 8.1% of schoolchildren had at least one AAb. We found that 3.04, 2.97, 2.35, and 0.86% had IAA, GADA, IA2A or ICA, respectively. 7.3% had only one AAb and 0.8% (75) had two or more AAbs, reflecting a risk to develop diabetes. Thus, by primary screening by combined testing of GADA and IA2A, 98.7% (74/75) would be identified. At high AAb levels, cut-off at or greater than the 99.8th centile and at or greater than 40 JDF units for ICA, 0.23% (22/9419) of schoolchildren, similar to the disease prevalence of 0.3%, had two or more AAbs. Ten of 17 children tested had reduced (p < 0.001) first-phase insulin secretion by intravenous glucose tolerance test. Six of 22 subjects developed Type I diabetes within a follow-up of 19 +/- 10 months. CONCLUSION/INTERPRETATION: For children older than 5 years the combined anti-GAD/IA2 test with cut-off at or greater than the 98th centile should be used for primary screening followed by testing for IAA and ICA. Subjects at risk for diabetes have two or more AAbs at or greater than the 98th centile. Subjects at risk for rapid progression to Type I diabetes have two or more AAbs at or greater than the 99.8th centile.

Adolescent↗
PubMed2006

Friend influence on prosocial behavior: The role of motivational factors and friendship characteristics.

This study examined motivation (prosocial goals), individual characteristics (sex, ethnicity, and grade), and friendship characteristics (affective quality, interaction frequency, and friendship stability) in relation to middle adolescents' prosocial behavior over time. Ninth- and 10th-grade students (N = 208) attending a suburban, mid-Atlantic public high school and having at least 1 reciprocated friendship were followed for 1 year. Hierarchical regression analyses revealed that a friend's behavior is related to an individual's prosocial goal pursuit, which in turn, is related to an individual's prosocial behavior. Further, the affective quality of a friendship and the frequency with which friends interact moderate relations of a friend's prosocial behavior to an individual's prosocial goal pursuit.

Adolescent↗
PubMed1973

Interaction of frequency and magnitude of reinforcement on concurrent performances.

Frequency and magnitude of reinforcement were varied in concurrent variable-interval variable-interval schedules of reinforcement. The relative response rate to the two stimuli did not support the notion that choice approximately matches relative total access to food (the product of frequency and magnitude of reinforcement in one schedule divided by the sum of products of frequency and magnitude in both schedules). Relative response rates matched relative reinforcement value when that measure was adjusted to give more emphasis to reinforcement frequency than to reinforcement duration.

Journal Article↗
PubMed1998

High frequency of interactions between lung cancer susceptibility genes in the mouse: mapping of Sluc5 to Sluc14.

Although several genes that cause monogenic familial cancer syndromes have been identified, susceptibility to sporadic cancer remains unresolved. Animal experiments have demonstrated multigenic control of tumor susceptibility. Recently, we described four mouse lung cancer susceptibility (Sluc) loci, the main effects of which are masked by their mutual interactions. Because such interactions can considerably affect the strategies for identification of cancer susceptibility genes in humans, it is necessary to establish whether they are common or rare. Here, we report the mapping of 10 additional Sluc loci and show that 13 of the 14 Sluc loci are involved in one or more interactions, demonstrating that interactions of tumor susceptibility genes are frequent and that they probably form complex networks.

Animals↗
PubMed1980

[Changes in the relation between therapist and group in the phases of intended dynamic group psychotherapy].

The progress of a group under intended dynamic direction was recorded over a period of 65 hours on the basis of interaction frequencies and directions as well as interaction contents and styles. It could be demonstrated that by means of this relatively simple or global approach an adequate and sufficiently sensitive picture of the therapist/patient activities and their phase-specific change could be reflected. On the basis of an example of a cohesive group, the change in significance of the therapist postulated in our conception and the interaction process between group, therapist and patient could be confirmed. The data obtained for the individual hours have been condensed for a demonstration of the phase-typical course.

Communication↗
PubMed1979

Selecting a cost-effective screening measure for the assessment of preschool social withdrawal.

The utility of teacher judgment (rankings, ratings) and peer judgment (sociometric ratings) were studied as screening variables for preschool social withdrawal/responsiveness. Observational measures of preschoolers' interaction were used as the validation criterion based upon theoretical, empirical, and practical considerations related to development of a multipurpose behavioral assessment system. Results indicated that teacher rankings of students' verbal interaction frequencies (1) were most highly correlated to interaction rate in two preschool settings, (2) had test-retest reliability consistently above Rho = .80, and (3) were useful in that 77% of teachers using this procedure could identify their least socially responsive student within five rankings. The peer nomination sociometric rating was the least reliable measure at retest (Rho = .35) and showed consistently the lowest correlation with observational indices of interaction partner preferences, e.g., reciprocal rate (Rho = .29 to .39). The tendency for relationships among screening measures and the criterion to increase at retest suggested a training effect on screening accuracy. The use of teacher rankings in combination with observational measures to confirm selection accuracy and for monitoring treatment progress is discussed as a cost-effective behavioral assessment procedure for preschool social withdrawal/responsiveness.

Child↗
PubMed1993

Interactions between physicians and the pharmaceutical industry: what does the literature say?

OBJECTIVE: To determine the effect of three types of interaction between physicians and the pharmaceutical industry--company-funded clinical trials, company-sponsored continuing medical education (CME) and information for physicians supplied by pharmaceutical detailers--on orientation and quality of clinical trials, content of CME courses and physicians' prescribing behaviour. DATA SOURCES: MEDLINE and HEALTH searches for English-language articles published from 1978 to 1993, supplemented by material from the author's personal collection. STUDY SELECTION: A total of 227 papers from the MEDLINE and HEALTH searches and about 2000 items from the author's library were initially reviewed. The following selection criteria were used: studies conducted in Australia, Canada, New Zealand, Britain and the United States; studies conducted after 1977; quantitative surveys containing details of the survey methods; studies on the orientation and quality of company-funded clinical trials and on the content of CME courses giving explicit criteria used in the evaluation; and reports on the outcome of interactions stating how the outcomes were assessed. Thirty-six studies met these criteria. DATA EXTRACTION: Information was extracted on five topics: physicians' attitudes toward drug industry interactions, frequency with which physicians participate in the interactions, orientation and quality of company-funded clinical trials, content of company-sponsored CME courses and changes in physicians' prescribing behaviour as a result of an interaction. DATA SYNTHESIS: Although most physicians participate only occasionally in company-sponsored clinical trials, most see detailers and attend company-sponsored CME courses. However, physicians do not have a very high opinion of the information from detailers or of company-sponsored CME events. Many doctors regard pharmaceutical companies as an important source of funding for clinical trials, but they also have concerns about accepting money from this source. Company funding of clinical trials may affect the quality of the trials and the types of research that physicians undertake. Company-sponsored CME courses may have a commercial bias even if conducted under guidelines designed to ensure the independence of the event. All three types of interactions affect physicians' prescribing behaviour and, in the case of obtaining information from detailers, physicians' prescribing practices are less appropriate as a result of the interaction. CONCLUSIONS: Physicians are affected by their interactions with the pharmaceutical industry. Further research needs to be done in most cases to determine whether such interactions lead to more or less appropriate prescribing practices. The CMA's guidelines on this topic should be evaluated to see whether they are effective in controlling physician-industry interactions. Further measures may be necessary if the guidelines fail to prevent negative effects on prescribing practices.

Attitude of Health Personnel↗
PubMed2004

Effect of supplementation frequency and supplemental urea level on dormant tallgrass-prairie hay intake and digestion by beef steers and prepartum performance of beef cows grazing dormant tallgrass-prairie.

Effect of supplementation frequency and supplemental urea level on forage use (Exp. 1) and performance (Exp. 2 and 3) of beef cattle consuming low-quality tallgrass-prairie were evaluated. For Exp. 1 and 2, a 2 x 2 factorial treatment structure was used, such that two supplements (30% CP) containing 0 or 30% of supplemental degradable intake protein (DIP) from urea were fed daily or on alternate days. In Exp. 1 and 2, supplement was fed at 0.41% BW daily or at 0.83% BW (DM basis) on alternate days. For Exp. 3, a 2 x 4 factorial treatment structure was used, such that four supplements (40% CP) containing 0, 15, 30, or 45% of supplemental DIP from urea were fed daily or 3 d/wk. Supplements were group-fed at 0.32% BW daily or at 0.73% BW (DM basis) 3 d/wk. In Exp. 1, 16 Angus x Hereford steers (initial BW = 252 kg) were blocked by BW and assigned to treatment. Urea level x supplementation frequency interactions were not evident for forage intake, digestion, or rate of passage. Forage OM intake (OMI) and total digestible OMI (TDOMI) were not significantly affected by treatment. Total-tract digestion of OM (P = 0.03) and NDF (P = 0.06) were greater for steers supplemented daily. In Exp. 2, 48 Angus x Hereford cows (initial BW = 490 kg) grazing winter tallgrass prairie were used. Significant frequency x urea interactions were not evident for BW and body condition (BC) change; similarly, the main effects were not substantive for these variables. In Exp. 3, 160 Angus x Hereford cows (initial BW = 525 kg) grazing dormant, tallgrass prairie were used. Supplement refusal occurred for cows fed the highest urea levels, particularly for cows fed the supplement with 45% of the DIP from urea 3 d/wk, and supplement refusal increased closer to calving. A frequency x urea interaction (P = 0.02) was observed for prepartum BW changes. As supplemental urea level increased, prepartum BW loss increased quadratically (P = 0.02); however, a greater magnitude of loss occurred when feeding supplements containing > or = 30% of DIP from urea 3 d/ wk. Cumulative BC change followed a similar trend. In conclusion, moderate protein (< or = 30% CP) supplements with < or = 30% of supplemental DIP from urea can be fed on alternate days without a substantive performance penalty. However, infrequent feeding of higher protein (> 30% CP) supplements with significant urea levels (> 15% of DIP from urea) may result in decreased performance compared with lower urea levels.

Animal Feed↗
PubMed1985

Spatial-frequency-dependent visible persistence and specific reading disability.

Visible persistence duration for sine-wave gratings was measured in 9-year-old normal and specific-reading-disabled children. Experiment 1 investigated the influence of stimulus duration on visible persistence. The results demonstrated a Reading Group X Spatial Frequency interaction with disabled readers showing a smaller increase in persistence duration with increasing spatial frequency than controls. This interaction was greatest with stimulus durations longer than 80 msec. In Experiments 2a and 2b persistence was measured across a range of contrasts from .1 to .5. The stimulus durations employed were 100 msec in Experiment 2a and 300 msec in Experiment 2b. In both experiments, increasing contrast decreased persistence duration at 2 and 12 cycles per degree (c/deg) for the control group. In the specific-reading-disabled group, however, contrast had little effect on the persistence of 2-c/deg gratings in either experiment. In Experiment 2a the persistence of the 12-c/deg grating decreased with increasing contrast for both groups. In Experiment 2b contrast had significantly less effect on persistence duration in the specific-reading-disabled group, however, contrast had little effect on the persistence of 2-c/deg ratings in either experiment. In Experiment 2b contrast had significantly less effect on persistence duration in the specific-reading-disabled group than in the control group at 12 c/deg. Consequently, contrast had less effect on persistence in specific-reading-disabled children than in normal readers, especially at durations longer than the "critical duration" for each spatial frequency. Experiment 3 extended this finding to gratings with spatial frequencies of 4 and 8 c/deg. These results indicate a difference between normal and specific-reading-disabled children in cortical visible persistence. Two scores of visual processing were derived from the above experiments. On these scores the reading-disabled children were divided into Visual Disabled Readers (approximately 70%--eight subjects) and Nonvisual Disabled Readers (approximately 30%--four subjects). The percentages of disabled readers in each category remained constant when the sample size was increased to 61 normal and disabled readers.

Attention↗
PubMed2001

The effects of frequency of social interaction and relationship closeness on reward allocation.

In this study of how the frequency of interaction affects decisions on reward allocation, 320 Chinese adults were randomly assigned to 8 conditions and instructed to read a scenario describing 2 co-workers completing a task and obtaining a bonus. The 8 conditions differed in the type of relationships, the frequency of past interaction between co-workers, and the possibility of future interaction. Each participant was instructed to act as the allocator and to hypothetically allocate a monetary reward to the co-worker. The results indicated that both past interaction and future interaction between the co-workers significantly influenced the allocation decision. These results also suggested that the frequency of 2 individuals' past interaction can be predictive of the closeness of their relationship.

Adult↗
PubMed1990

Hemispheric differences are found in the identification, but not the detection, of low versus high spatial frequencies.

The processing of sine-wave gratings presented to the left and right visual fields was examined in four experiments. Subjects were required either to detect the presence of a grating (Experiments 1 and 2) or to identify the spatial frequency of a grating (Experiments 3 and 4). Orthogonally to this, the stimuli were presented either at threshold levels of contrast (Experiments 1 and 3) or at suprathreshold levels (Experiments 2 and 4). Visual field and spatial frequency interacted when the task required identification of spatial frequency, but not when it required only stimulus detection. Regardless of contrast level (threshold, suprathreshold), high-frequency gratings were identified more readily in the right visual field (left hemisphere), whereas low-frequency gratings showed no visual field difference (Experiment 3) or were identified more readily in the left visual field (right hemisphere) (Experiment 4). Thus, hemispheric asymmetries in the processing of spatial frequencies depend on the task. These results support Sergent's (1982) spatial frequency hypothesis, but only when the computational demands of the task exceed those required for the simple detection of the stimuli.

Adult↗
PubMed2003

Cochlear phase and amplitude retrieved from the auditory nerve at arbitrary frequencies.

It is currently impossible to mechanically measure the overall vibration pattern of the intact mammalian cochlea because of its inaccessibility and vulnerability. At first sight, data from the auditory nerve are a poor substitute because of their limited temporal resolution. The nonlinear character of neural coding, however, causes low-frequency interactions among the components of multitone stimuli. We designed a novel stimulus for which these interactions take a particularly systematic form, and we recorded the response of the auditory nerve to this stimulus. A careful analysis of interactions in the data allowed us to reconstruct frequency transfer functions (both their amplitude and their phase) at multiple points spanning the entire length of the cochlea. The generic character of our stimuli and analysis suggests its wider use in nonlinear system analysis, particularly in those instances in which limitations in temporal resolution restrict the use of customary methods.

Acoustic Stimulation↗
PubMed1995

Frequency modulated sound pattern analysis in the lesser bulldog bat: the role of interactions between adjacent frequency elements of complex sounds.

A stereotyped approach phase vocalization response of Noctilio albiventris to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bats depended on the temporal pattern of frequency change of the continuously sweeping frequency modulated (FM) component of the signals. When the bats were presented with a CF/FM signal containing a time-reversed upward FM sweep, they responded with approach phase behavior at a performance level that was significantly below that seen with a CF/FM signal containing a naturally structured downward FM sweep. When the FM sweep was divided into a series of brief pure tone steps, the extent to which the bats showed a difference in their capability to process upward versus downward FM sweeps depended on the difference in frequency between the pure tone steps. The bats effectively processed downward but not upward FM sweeps when the difference in frequency between pure tone frequency elements of the FM sweeps was from about 100-200 Hz, but they effectually processed both downward and upward FM sweeps when the tonal elements composing the FM sweeps were separated by more than about 200 Hz. This suggests that the ability of the bats to effectively process downward but not upward FM sweeps is based on local interactions between adjacent frequency elements of the complex sounds.

Animals↗