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  • twins  (5)
  • heritability  (4)
  • muon-catalyzed fusion  (3)
  • 1
    Digitale Medien
    Digitale Medien
    A source of variance in IQ unique to the lower-scoring monozygotic (MZ) cotwin (1986)
    Springer
    Behavior genetics 16 (1986), S. 509-516 
    Details
    ISSN: 1573-3297
    Schlagwort(e): twins ; heritability ; environment ; intelligence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Environmental factors more common in twins than singletons appear to be disadvantageous with respect to intelligence. If these factors contribute to within-pair differences in IQ, the effect should be found more in the cotwin lower in IQ (the low twin) than in the cotwin higher in IQ (the high twin). In this case, the variance of the low twins should exceed that of the high twins. This hypothesis was tested for five samples of monozygotic (MZ) twins and three samples of dizygotic (DZ) twins but was confirmed only for the MZ samples. These results suggest that there are disadvantageous environmental factors unique to MZ twins which contribute to within-pair variability. Such factors will cause heritability coefficients obtained using MZ twins to be underestimated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01066337
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  • 2
    Digitale Medien
    Digitale Medien
    Estimating true scores in kinship data (1987)
    Springer
    Behavior genetics 17 (1987), S. 487-491 
    Details
    ISSN: 1573-3297
    Schlagwort(e): true scores ; measurement error ; kinship data ; twins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Estimated true scores are occasionally used to provide an estimate of scores which would be obtained if measurement error could be removed from fallible measures. When one knows only a test's relibility and an observed score for each subject, true scores are estimated by regressing observed scores toward the group mean. When relatives' observed scores are also available, estimates of true scores can be improved by using the additional information. Observed scores of subjects and relatives can be used as predictors of subjects' true scores in a multiple regression. The resulting formula is presented for the case in which only one relative's score per subject is known. Estimation of true scores for the general case ofN relatives per subject is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01073115
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  • 3
    Digitale Medien
    Digitale Medien
    Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins (1991)
    Springer
    Behavior genetics 21 (1991), S. 75-96 
    Details
    ISSN: 1573-3297
    Schlagwort(e): sexual orientation ; twins ; heritability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchial tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01067668
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  • 4
    Digitale Medien
    Digitale Medien
    Muon-catalyzed fusion in deuterium at 3 K (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 21-28 
    Details
    ISSN: 1572-9540
    Schlagwort(e): muon-catalyzed fusion ; deuterium ; solid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Muon-catalyzed fusion in deuterium has traditionally been studied in gaseous and liquid targets. The TRIUMF solid hydrogen layer target system has been used to study the fusion reaction rates in the solid phase at a target temperature of 3 K. Both branches of the cycle were observed; neutrons by a liquid organic scintillator, and protons by a silicon detector located inside the target system. The effective molecular formation rate from the upper hyperfine state and the spin exchange rate have been measured, and information on the branching ratio parameters has been extracted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02227602
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  • 5
    Digitale Medien
    Digitale Medien
    Characterization of solid hydrogen targets (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 641-646 
    Details
    ISSN: 1572-9540
    Schlagwort(e): muon-catalyzed fusion ; thickness measurement ; solid hydrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In experiments using the TRIUMF solid hydrogen target system, the knowledge of the target thickness and uniformity is often essential in order to extract physical parameters from the data. We have characterized the thickness and uniformity of frozen targets using the energy loss of alpha particles. An accuracy of ∼5% was achieved, a limit imposed by the uncertainty in the stopping powers: The details of the method are described, and the thickness calibration of the target is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02227677
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  • 6
    Digitale Medien
    Digitale Medien
    Time-of-flight measurement of resonant molecular formation in muon-catalyzed dt fusion (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 47-55 
    Details
    ISSN: 1572-9540
    Schlagwort(e): muon-catalyzed fusion ; muonic hydrogen ; muonic atoms ; muonic molecules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Preliminary results are reported for an experiment at TRIUMF where a time-of-flight technique was tested for measuring the energy dependence of the rate for muon-catalyzed dt fusion. Muonic tritium atoms were created following transfer of negative muons from muonic protium in a layer of solid hydrogen (protium) containing a small fraction of tritium. The atoms escaped from the solid layer via the Ramsauer-Townsend mechanism, traversed a drift region of 18 mm, and then struck an adjacent layer of deuterium, where the muonic atom could form a molecular system. The time of detection of a fusion product (neutron or alpha) following muon arrival is dependent upon the energy of the muonic tritium atom as it traverses the drift region. By comparison of the time distribution of fusion events with a prediction based on the theoretical energy dependence of the rate, the strength of resonant formation can in principle be determined. The results extracted so far are discussed and the limitations of the method are examined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02227605
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  • 7
    Digitale Medien
    Digitale Medien
    Increased heritability for lower IQ levels? (1991)
    Springer
    Behavior genetics 21 (1991), S. 397-404 
    Details
    ISSN: 1573-3297
    Schlagwort(e): twins ; heritability ; environment ; intelligence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Dettermanet al. (1990) presented evidence based on twins that the heritability of IQ may be higher in the lower part of the IQ range. We first offer an alternative test for differential heritability across the IQ range, based on the analysis of absolute intrapair differences of monozygotic versus dizygotic twins. We then review two previous studies, each containing more twins than the sample of Dettermanea al., which examined the distribution of intrapair absolute differences. In contrast to the study of Dettermanet al., both yielded results more compatible with higher heritability in the upper range of IQ. We discuss various interpretations of these findings and show how our proposed test might aid in distinguishing among them.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01065975
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  • 8
    Digitale Medien
    Digitale Medien
    Measurement Models for Sexual Orientation in a Community Twin Sample (2000)
    Springer
    Behavior genetics 30 (2000), S. 345-356 
    Details
    ISSN: 1573-3297
    Schlagwort(e): Homosexuality ; sexual orientation ; heritability ; twins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Multivariate structural equation modeling techniques have been applied to examine the causes of individual differences in responses to several items concerning sexual orientation. To minimize potential ascertainment and response biases, the study sample involved a large (N = 4901) community-based cohort of Australian twins aged 18–52 who answered an anonymous questionnaire on sexual behavior and attitudes. The statistical power of the analysis was increased by the availability of multiple measures of sexual orientation (behaviors, attitudes and feelings), providing stronger evidence for the existence of additive genetic influences on this phenotype than in a previous analysis (Bailey et al., 2000). Estimates of the heritability of homosexuality in this sample ranged between 50 and 60% in females but were significantly lower (heritability of approximately 30%) in males.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026557719181
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