862 research outputs found

    Changes in Completed Family Size and Reproductive Span in Anabaptist Populations

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    The Anabaptist Amish, Hutterite and Mennonite peoples trace their origins to the Reformation. Although they share certain beliefs, such as adult baptism and the separation of church and state, each group is culturally unique. The Hutterite and Amish are highly fertile and their populations exhibit stable rates of growth. These demographic characteristics reflect communal living among the Hutterites and labor intensive farming practices among the Amish. The Mennonites are the most receptive Anabaptist group to outside socioeconomic influences and provide a demographic contrast to the more conservative Amish and Hutterites. Demographic data collected during a study of aging in Mennonite population samples from Goessel and Meridian, Kansas, 1980, and Henderson, Nebraska, 1981, formed the basis of a cohort analysis in order to assess fertility change over time. Completed family size has decreased significantly in all three communities since 1870. Since the early 1900\u27s the mean age of the mother at first birth has fluctuated but the mean age of mother at the birth of the last child is decreasing significantly for the communities of Goessel and Henderson, thus effectively shortening the reproductive span. The pattern is somewhat different for Meridian, the most conservative of the three communities

    Immunoglobulin Haplotypes – Markers of Reproductive Success

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    Immunoglobulin haplotypes are highly polymorphic and are useful for analyses of both macro- and microdifferentiation of populations. The origins of this diversity are not known, but recent reports suggest strong selection at this locus. Increased rates of first-trimester spontaneous abortions have been reported when parents share GM phenotypes. Reduced fertility has been observed in mixed European descent white and Hutterite populations when both parents share immunoglobulin haplotypes. Population samples with completed family information and GM haplotype data are rare; the objective here is to provide this information on another sample. A sample of 242 Mennonite couples with mothers older than 40 years was divided into 3 groups of matings based on how many haplotypes were shared: 0, 1, or 2. The distribution of mean completed family sizes for the three groups were 3.35 ± 1.85 ( n = 23), 3.47 ± 1.69 ( n = 128), and 3.37 ± 1.60 ( n = 91), respectively; these values were not significantly different (F = 0.145, p = 0.865). The log-rank test was used to compare the time-to-next-birth curves. The intervals between first and later births (2-4 births) were not significantly different for the three subgroups either. There is also only limited evidence for segregation distortion in another sample of 923 offspring (in which at least one parent is heterozygous)

    Mitochondrial DNA Diversity in Mennonite Communities from the Midwestern United States

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    We examined mitochondrial DNA (mtDNA) variation in six Mennonite communities from Kansas (Goessel, Lone Tree, Garden View, Meridian, and Garden City) and Nebraska (Henderson) to determine their genetic structure and its relationship to population history. Mitochondrial DNA haplogroup and haplotype information were obtained from blood samples from 118 individuals. Molecular genetic variation was analyzed using diversity measures, neutrality test statistics, spatial analysis of molecular variance (SAMOVA), and multidimensional scaling plots. The Mennonite samples exhibited eight western European mtDNA haplogroups: H, HVO, I, J, K, T, U, and X. Comparable to other populations of European descent, haplogroup H was the most frequent in all six communities and ranged from 35% in Lone Tree to 75% in Old Order Mennonites from Garden City. Fifty-eight different mtDNA haplotypes were found in these groups with only one shared among all six populations. Haplotype diversities varied from 0.81 in Goessel to 0.96 in Henderson and Garden View. Multivariate statistical analysis of these populations indicates that these Anabaptist communities formed new congregations by fissioning along familial lines. Population subdivision of these communities into congregations supports previously documented patterns of fission-fusion. These haploid molecular data provide a more accurate reflection of biological relationships between midwestern Mennonite communities than evidence based on classical genetic markers

    XMMU J0541.8-6659, a new supernova remnant in the Large Magellanic Cloud

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    The high sensitivity of the XMM-Newton instrumentation offers the opportunity to study faint and extended sources in the Milky Way and nearby galaxies such as the Large Magellanic Cloud (LMC) in detail. The ROSAT PSPC survey of the LMC has revealed more than 700 X-ray sources, among which there are 46 supernova remnants (SNRs) and candidates. We have observed the field around one of the most promising SNR candidates in the ROSAT PSPC catalogue, labelled [HP99] 456 with XMM-Newton, to determine its nature. We investigated the XMM-Newton data along with new radio-continuum, near infrared and optical data. In particular, spectral and morphological studies of the X-ray and radio data were performed. The X-ray images obtained in different energy bands reveal two different structures. Below 1.0 keV the X-ray emission shows the shell-like morphology of an SNR with a diameter of ~73 pc, one of the largest known in the LMC. For its thermal spectrum we estimate an electron temperature of (0.49 +/- 0.12)keV assuming non-equilibrium ionisation. The X-ray images above 1.0 keV reveal a less extended source within the SNR emission, located ~1' west of the centre of the SNR and coincident with bright point sources detected in radio-continuum. This hard component has an extent of 0.9' (i.e. ~13 pc at a distance of ~50 kpc) and a non-thermal spectrum. The hard source coincides in position with the ROSAT source [HP99] 456 and shows an indication for substructure. We firmly identify a new SNR in the LMC with a shell-like morphology and a thermal spectrum. Assuming the SNR to be in the Sedov phase yields an age of ~23 kyr. We explore possible associations of the hard non-thermal emitting component with a pulsar wind nebula (PWN) or background active galactic nuclei (AGN).Comment: 8 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

    Spherically symmetric relativistic stellar structures

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    We investigate relativistic spherically symmetric static perfect fluid models in the framework of the theory of dynamical systems. The field equations are recast into a regular dynamical system on a 3-dimensional compact state space, thereby avoiding the non-regularity problems associated with the Tolman-Oppenheimer-Volkoff equation. The global picture of the solution space thus obtained is used to derive qualitative features and to prove theorems about mass-radius properties. The perfect fluids we discuss are described by barotropic equations of state that are asymptotically polytropic at low pressures and, for certain applications, asymptotically linear at high pressures. We employ dimensionless variables that are asymptotically homology invariant in the low pressure regime, and thus we generalize standard work on Newtonian polytropes to a relativistic setting and to a much larger class of equations of state. Our dynamical systems framework is particularly suited for numerical computations, as illustrated by several numerical examples, e.g., the ideal neutron gas and examples that involve phase transitions.Comment: 23 pages, 25 figures (compressed), LaTe

    Immunoglobulin Haplotype Frequencies in Anabaptist Population Samples: Kansas and Nebraska Mennonites and Indiana Amish

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    Anabaptist history is a chronicle of repeated migrations, fissions, and fusions of various subgroups. The effects of these events should be evident in the population biology of the Anabaptist groups. No prior genetic studies have included the polymorphic and highly informative immunoglobulin markers. Here, 685 serum samples representing 1 Amish and 3 Mennonite community samples (7 congregations) were studied for immunoglobulin allotypes. The haplotypes IGHG*F B, IGHG*A,Z G, and IGHG*A,X,Z G range in frequency from 0.542 to 0.765, 0.123 to 0.290, and 0.075 to 0.170, respectively. IGK*1 frequencies range from 0.035 to 0.077, All frequencies are within expected ranges for central and western European population samples, There was considerable intergroup variability among the Anabaptist samples that was statistically significant x29 = 22.63, 0.005 \u3c p \u3c 0.01), Principal component analyses, including the immunoglobulin allotype frequencies and published data on ABO, MN, and Rhesus (Dd) markers, demonstrate that the Mennonite congregation samples with close historical ties group together acid are distinct from the Amish and Meridian congregation samples

    Key aerodynamic technologies for aircraft engine nacelles

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    Customer requirements and vision in aerospace dictate that the next generation of civil transport aircraft should have a strong emphasis on increased safety, reduced environmental impact and reduced cost without sacrificing performance. In this context, the School of Mechanical and Aerospace Engineering at the Queen's University of Belfast and Bombardier have, in recent years, been conducting research into some of the key aerodynamic technologies for the next generation of aircraft engine nacelles. Investigations have been performed into anti-icing technology, efficient thrust reversal, engine fire zone safety, life cycle cost and integration of the foregoing with other considerations in engine and aircraft design. A unique correlation for heat transfer in an anti-icing system has been developed. The effect of normal vibration on heat transfer in such systems has been found to be negligible. It has been shown that carefully designed natural blockage thrust reversers without a cascade can reduce aircraft weight with only a small sacrifice in the reversed thrust. A good understanding of the pressure relief doors and techniques to improve the performance of such doors have been developed. Trade off studies between aerodynamics, manufacturing and assembly of engine nacelles have shown the potential for a significant reduction in life cycle cost
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