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  • sexual orientation  (9)
  • twins  (5)
  • Inorganic Chemistry  (4)
  • perennial ryegrass  (4)
  • 1
    Electronic Resource
    Electronic Resource
    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
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066337
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  • 2
    Electronic Resource
    Electronic Resource
    Estimating true scores in kinship data (1987)
    Springer
    Behavior genetics 17 (1987), S. 487-491 
    Details
    ISSN: 1573-3297
    Keywords: true scores ; measurement error ; kinship data ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073115
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Familiality of female and male homosexuality (1993)
    Springer
    Behavior genetics 23 (1993), S. 313-322 
    Details
    ISSN: 1573-3297
    Keywords: Homosexuality ; sexual orientation ; familiality ; environment ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract We examined data from a large cohort of homosexual and heterosexual females and males concerning their siblings' sexual orientations. As in previous studies, both male and female homosexuality were familial. Homosexual females had an excess of homosexual brothers compared to heteroxual subjects, thus providing evidence that similar familial factors influence both male and female homosexuality. Furthermore, despite the large sample size, homosexual females and males did not differ significantly from each other in their proportions of either homosexual sisters or homosexual brothers. Thus, results were most consistent with the possibility that similar familial factors influence male and female sexual orientation. However, because results conflicted with those of some other studies, and because siblings' sexual orientations were obtained in a manner likely to yield more errors than in these other, smaller studies, further work is needed using large samples and more careful methods before the degree of cofamiliality of male and female homosexuality can be resolved definitively. We also examined whether some parental influences comprised shared environmental effects on sexual orientation. Scales attempting to measure such influences failed to distinguish subjects with homosexual siblings from subjects with only heterosexual siblings and, thus, did not appear to measure shared environmental determinants of sexual orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067431
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  • 4
    Electronic Resource
    Electronic Resource
    Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins (1991)
    Springer
    Behavior genetics 21 (1991), S. 75-96 
    Details
    ISSN: 1573-3297
    Keywords: sexual orientation ; twins ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067668
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  • 5
    Electronic Resource
    Electronic Resource
    A re-examination of phosphorus-lime interactions in perennial ryegrass (1991)
    Springer
    Plant and soil 135 (1991), S. 185-196 
    Details
    ISSN: 1573-5036
    Keywords: calcium ; critical phosphorus concentration ; gypsum ; lime ; perennial ryegrass ; root membranes ; soluble carbohydrate ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The results of a previous study had suggested that under conditions of limited P availability, Ca may be able to compensate for P in the shoot tissue of perennial ryegrass. To verify this preliminary finding, a factorial experiment was set up which simultaneously tested the effects of Ca and P fertilization on the yield and chemical composition of perennial ryegrass. Calcium was supplied as either lime or gypsum in order to differentiate between the effects of Ca and pH on the response of perennial ryegrass to P fertilization. In the final stage of the experiment a Zn treatment was included, to see whether altering the P/Zn ratios of plant shoots had any influence on the purported interaction between Ca and P. The results demonstrated that the P-sparing effect of lime occurs, at least partly, because Ca application improves the efficiency of absorbed P for DM production. However, it was reasonably clear that the site of the interaction between Ca and P was the soil-root interface, and not shoot tissue. It was suggested that under conditions of limited P supply, Ca stablizes root membranes and thereby minimizes both the efflux losses of nutrients from root tissue, and the compensatory flow of photosynthates from shoots to roots. No interaction was observed between P and Zn treatments in this study. Instead, a positive interaction was found between lime and Zn treatments, which suggests that the stabilizing action of Ca on root membranes requires Zn as a co-stabilizing factor. It is proposed that chemical analysis of shoot tissue alone may not be sufficient to accurately diagnose the P, Ca or Zn status of whole plants, since the critical levels of these elements in shoots appear to bear little relation to their requirements in the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010906
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of gypsum on the uptake, assimilation and cycling of 15N-labelled ammonium and nitrate-N by perennial ryegrass (1992)
    Springer
    Plant and soil 143 (1992), S. 19-31 
    Details
    ISSN: 1573-5036
    Keywords: ammonium ; calcium ; carboxylate/organic nitrogen ratio ; 15N isotope ; nitrate ; nitrogen cycling ; perennial ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Solution culture studies have shown that plant uptake of NH4 + and NO3 - can be improved by increasing the concentration of Ca2+ in the root environment: the same may be true for grass grown in soil culture. An experiment was set up to see whether gypsum (CaSO4 2H2O) increased the rate at which perennial ryegrass absorbed 15NH4 + and 15NO3 - from soil. The results demonstrated that gypsum increases the rates of uptake of both NH4 + and NO3 - by perennial ryegrass. However because there was little potential for mineral-N loss from the experimental system, either by gaseous emission or by N immobilization, long term improvements in fertilizer efficiency were not observed. Nitrogen cycling from shoots to roots commenced once net uptake of N into plants had ceased. Labelled N transferred thus to roots underwent isotopic exchange with unlabelled soil N. It was suggested that this exchange of N might constitute an energy drain from the plant, if plant organic N was exchanged for soil inorganic N. The fact that the exchange occurred at all cast doubt on the suitability of the 15N-isotope dilution technique for assessing fertilizer efficiency in medium to long term experiments. There was evidence that the ‘extra’ NO3 --N taken up by plants on the all-nitrate treatments as a result of gypsum application, was reduced in root tissue rather than in shoots, but to the detriment of subsequent root growth and N uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009125
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  • 7
    Electronic Resource
    Electronic Resource
    Empirical Models for Predicting the Dry Matter Yield of Grass Silage Swards Using Plant Tissue Analyses (2000)
    Springer
    Precision agriculture 2 (2000), S. 131-145 
    Details
    ISSN: 1573-1618
    Keywords: empirical models ; perennial ryegrass ; silage swards ; tissue analyses ; yield mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quantifying spatial variability in forage grass yield within individual fields is hampered by the lack of accurate yield monitoring equipment. Here, it is shown how dry matter (DM) yield of silage swards can be predicted on the basis of their mineral composition. This empirical method of predicting yield enables diagnoses of sward nutrient status to be made simultaneously from the tissue test information, and provides a unique opportunity for identifying the nutritional and non-nutritional factors responsible for variability in sward productivity at sub-field scales. Maps of sward DM yield at first, second and third cut silage stages in 1999, and at first cut silage stage in 2000, on a large (7.9 ha) grassland field were produced using two different yield models: one model for first cut and a separate model for second and third cuts. The maps indicated that DM production varied considerably across the field, particularly at first cut, but that the pattern of yield variability at this cut was consistent from 1999 to 2000. The results of the plant tissue tests suggested that N deficiency had been responsible for limiting DM production on the lower yielding parts of the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011421613409
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    The Diagnosis and Recommendation Integrated System (DRIS) for diagnosing the nutrient status of grassland swards: III Practical applications (2000)
    Springer
    Plant and soil 222 (2000), S. 255-262 
    Details
    ISSN: 1573-5036
    Keywords: basaltic soils ; DRIS ; perennial ryegrass ; phosphorus recommendations ; soil P test ; soil type
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Perennial ryegrass is the most important species of forage grass in both continental Europe and the British Isles. An investigation was carried out to see if the DRIS model developed for this species was able to diagnose crop nutrient sufficiency status, at harvest time, using data for herbage samples collected 2 weeks earlier. A re-evaluation of P fertiliser recommendations for silage, based on the ‘Olsen’ soil P-test, was then carried out using DRIS diagnoses of P sufficiency status as the criteria with which to judge if swards had been adequately, under, or over-supplied with fertiliser P. The results confirmed that reliable (DRIS) diagnoses of N, P, K and S sufficiency statuses of silage swards may be made from herbage clippings taken 2 weeks prior to harvest. Current P recommendations for silage swards proved to be excessive for non-basaltic sandy textured soils at first cut, correct for this group of soils at second cut, and more or less correct for non-basaltic clay textured soils at both cuts. For basaltic soils, however, P recommendations at both cuts appeared to be unrelated to plant P status, and it was concluded that the ‘Olsen’ soil P-test had provided an erroneous assessment of plant available P in these exceptionally iron-rich soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004827206618
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  • 9
    Electronic Resource
    Electronic Resource
    Sexual Orientation and Professional Dance (1997)
    Springer
    Archives of sexual behavior 26 (1997), S. 433-444 
    Details
    ISSN: 1573-2800
    Keywords: sexual orientation ; dance ; careers ; gender identity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract The stereotypical professional male dancer is a gay man. However, little if any systematic research has investigated the validity of this stereotype, much less the reasons why male sexual orientation would be associated with interest in dance. We interviewed 136 professional dancers about the prevalence of homosexuality among dancers, the dancers' own sexual development, and relationships between dancers of different sexual orientations. Dancers estimated that over half of male dancers are gay, but that only a small minority of female dancers are lesbian. Gay men recalled more intense early interest in dance compared to heterosexual men and women, and were more feminine as boys than were heterosexual men. Gay men's homosexual feelings typically preceded their dance experience, and only one gay man felt that his dance experiences may have influenced his sexual orientation. Heterosexual men voiced some mild complaints about gay male dancers, but these were balanced by positive sentiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1024595419744
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  • 10
    Electronic Resource
    Electronic Resource
    Sexual Orientation of Female-to-Male Transsexuals: A Comparison of Homosexual and Nonhomosexual Types (2000)
    Springer
    Archives of sexual behavior 29 (2000), S. 259-278 
    Details
    ISSN: 1573-2800
    Keywords: transsexual ; female-to-male ; sexual orientation ; gender identity ; mating psychology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract Homosexual and nonhomosexual (relative to genetic sex) female-to-male transsexuals (FTMs) were compared on a number of theoretically or empirically derived variables. Compared to nonhomosexual FTMs, homosexual FTMs reported greater childhood gender nonconformity, preferred more feminine partners, experienced greater sexual rather than emotional jealousy, were more sexually assertive, had more sexual partners, had a greater desire for phalloplasty, and had more interest in visual sexual stimuli. Homosexual and nonhomosexual FTMs did not differ in their overall desire for masculinizing body modifications, adult gender identity, or importance of partner social status, attractiveness, or youth. These findings indicate that FTMs are not a homogeneous group and vary in ways that may be useful in understanding the relation between sexual orientation and gender identity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001915530479
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