Paternal influence on twinning was investigated through a study of all the state and church records of Scotland for the period 1800-2000 (nine generations) in relation to one Scottish patronymic - in total 50,000 births. All recorded twins born with the chosen patronymic were identified and their whole paternal ascent and descent on the male line were charted for twins. There were established t...

There is widespread concern about a possible decline in human fertility in recent decades. The spontaneous dizygotic twinning rate provides a way of measuring a combination of male plus female fertility as it reflects the frequency of double ovulation, the probability of fertilization, and the survival of the zygote. There was a decline in dizygotic twinning rates in developed countries which b...

The crystal structure of superoxide dismutase from the hyperthermophilic crenarchaeon Pyrobaculum aerophilum was determined by molecular replacement at 1.8 A resolution. The structure determination was made especially challenging by the large number of molecules (24) in the asymmetric unit, the presence of a pseudo-crystallographic twofold operator close to a twinning operator and the inability...

Variation in the frequency of twinning among human populations has been presumed to reflect genetic differences. It has been commonly reported that populations of African ancestry have the highest, those of Asian ancestry the lowest, and those of European and Middle-Eastern ancestry intermediate frequencies of twinning. Populations from the Americas have been reported to have intermediate twinn...

Based on the birth record data from the National Vital Statistics in the 1990 Census of China, the present study analyzed the differences between urban and rural areas on monozygotic (MZ) and dizygotic (DZ) twin rates by maternal age in 1989. The twins by zygosity were calculated with Weinberg's differential method. Results show that the MZ and DZ twinning rates in China were associated with ma...

The seasonality of twinning in the Spanish populations has not been studied until now. Differences between seasonal distribution of the twin conceptions and those of the single births have been observed in other populations. The aim of this work is to explore the frequency of twinning in a rural population from Catalonia during the nineteenth century, as well as the seasonality patterns charact...

Because of the predominance of multiple ovulation in mice, it has been generally accepted that evidence for monozygotic twinning would be difficult to obtain. The two attempts that have been made have failed to find any evidence for twins surviving birth at a measurable rate. In Fisher and Mather's (I936) sevenfold backcross experiment there is no evidence of twinning at all. In each of Bateman...

AIMS To investigate whether twinning occurs more frequently in residents in the vicinity of a toxic waste incinerator (TWI). METHODS Within a longitudinal environmental study that addressed child health second grade school children and their parents were recruited. The proportion of twinning in the TWI region was compared with two comparison areas. In a second confirmatory investigation, birt...

The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. Considering grain size effects on the critical stress for twinning, twins ...

Nanocrystalline (nc) materials can be defined as solids with grain sizes in the range of 1–100 nm. Contrary to coarse-grained metals, which become more difficult to twin with decreasing grain size, nanocrystalline face-centered-cubic (fcc) metals become easier to twin with decreasing grain size, reaching a maximum twinning probability, and then become more difficult to twin when the grain size ...