1,693 research outputs found

    Electromechanical Simulation of Actively Controlled Rotordynamic Systems with Piezoelectric Actuators

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    Theories and tests for incorporating piezoelectric pushers as actuator devices for active vibration control are discussed. It started from a simple model with the assumption of ideal pusher characteristics and progressed to electromechanical models with nonideal pushers. Effects on system stability due to the nonideal characteristics of piezoelectric pushers and other elements in the control loop were investigated

    Unhatched Eggs in Nests of Red-cockaded Woodpeckers

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    During 1991 and 1992, nests of Red-cockaded Woodpeckers (Picoides borealis) were monitored in the Ouachita National Forest in Scott and Polk counties of west-central Arkansas. Nests in three additional woodpecker areas in Arkansas and Oklahoma were also monitored in 1992. Of 92 eggs laid in 27 nesting attempts in the Ouachita National Forest, 18 (19%) failed to hatch. When viewed in the cavities, six unhatched eggs were noticeably below average in size for the species and eight were average size. Seven unhatched eggs were removed in 1992 from seven nests in Arkansas and Oklahoma; three eggs showed some embryological development and three showed no development. Techniques used to remove unhatched eggs and results of analysis of eggs are presented. Possible management applications of egg data are discussed

    Gene content phylogeny of herpesviruses

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    Clusters of orthologous groups [COGs; Tatusov, R. L., Koonin, E. V. & Lipman, D. J. (1997) Science 278, 631–637] were identified for a set of 13 completely sequenced herpesviruses. Each COG represented a family of gene products conserved across several herpes genomes. These families were defined without using an arbitrary threshold criterion based on sequence similarity. The COG technique was modified so that variable stringency in COG construction was possible. High stringencies identify a core set of highly conserved genes. Varying COG stringency reveals differences in the degree of conservation between functional classes of genes. The COG data were used to construct whole-genome phylogenetic trees based on gene content. These trees agree well with trees based on other methods and are robust when tested by bootstrap analysis. The COG data also were used to construct a reciprocal tree that clustered genes with similar phylogenetic profiles. This clustering may give clues to genes with related functions or with related histories of acquisition and loss during herpesvirus evolution

    Restocking Northern Bobwhites in East Texas: A Genetic Assessment

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    Habitat on a 610-ha study area in the Pineywoods Ecological Region of eastern Texas was enhanced for northern bobwhites ( Coli nus virginianus). In February and March 1990, 1991, and 1992, bobwhites from south Texas (C. v. texanus) and disjunct areas of east Texas (C. v. mexicanus) were captured, radio tagged, and relocated to the study area which had a small ( \u3c25 birds) resident population. Blood samples were collected from the birds relocated in 1991. Samples were also collected from birds in the resident population during 1991 and 1992; these birds were assumed to be offspring of the previous years\u27 resident and relocated bobwhites. Restriction site variation of mitochondrial DNA (mtDNA) revealed geographic subdivision between the subspecies but not between resident and east Texas relocated birds. The observed frequency differences of mtDNA haplotypes were used to assess the relative reproductive success of the 2 subspecies. Among the birds examined for mtDNA variation, offspring produced on the study area during 1990 and 1991 were genetically more similar to the east Texas subspecies than to the south Texas subspecies. These results suggest that efforts to restock northern bobwhite should involve either local birds or birds from the same subspecies. Management implications of these findings are discussed

    Multi-round trust game quantifies inter-individual differences in social exchange from adolescence to adulthood

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    Investing in strangers in a socio-economic exchange is risky, as we may be uncertain whether they will reciprocate. Nevertheless, the potential rewards for cooperating can be great. Here, we used a cross sectional sample (n = 784) to study how the challenges of cooperation versus defection are negotiated across an important period of the lifespan: from adolescence to young adulthood (ages 14 to 25). We quantified social behaviour using a multi round investor-trustee task, phenotyping individuals using a validated model whose parameters characterise patterns of real exchange and constitute latent social characteristics. We found highly significant differences in investment behaviour according to age, sex, socio-economic status and IQ. Consistent with the literature, we showed an overall trend towards higher trust from adolescence to young adulthood but, in a novel finding, we characterized key cognitive mechanisms explaining this, especially regarding socio-economic risk aversion. Males showed lower risk-aversion, associated with greater investments. We also found that inequality aversion was higher in females and, in a novel relation, that socio-economic deprivation was associated with more risk averse play
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