X-ray diffraction and computer simulation studies on the structure of homophase and heterophase interfaces in metals

We use the Thin Film X-ray Diffraction (TFXD) technique in conjunction with computer simulation methods to obtain detailed information on the structure of complex interfacial systems in metals. Results for three types of interfaces are presented. These are, a [Sigma] 13 [001] twist homophase boundary in a Au-Cu 10 at. % alloy, a [Sigma] 26/29 [001] twist Au-Pd heterophase boundary and finally the [Sigma] 4/5 [001] twist Ag-Cu heterophase boundary. For the homophase boundary in Au-Cu we demonstrate the utility of the X-ray technique in studying the effects of solute segregation on boundary structure. Calculations predict trends which are in agreement with the experimental observations; however the precise magnitudes of the observed effects are not reproduced by the calculations. For the Au-Pd heterophase boundary semi-quantitative agreement is obtained between the experiments and the calculations (performed using EAM potentials and Molecular Statics). Finally, in the Ag-Cu [Sigma] 4/5 system, strong X-ray scattering is observed on the BDL, and is correlated with surprisingly large atomic displacements in this boundary; fairly good agreement is obtained with computer simulated structures. We conclude with speculations on the usefulness of the simple dislocation model in the Ag-Cu [001] twist system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31311/1/0000220.pd

The Role of Appearance in Adolescents’ Experiences of Neurofibromatosis Type 1: A Survey of Young People and Parents

© 2016, National Society of Genetic Counselors, Inc. Neurofibromatosis type 1 (NF1) is a genetic condition which can result in varying degrees of visible difference (disfigurement). Adolescence is a time when appearance concerns become more salient for many young people and is acknowledged as a particularly challenging time for individuals with NF1. There is currently little research into the psychosocial impact of the appearance changes associated with NF1 during this stage of life. In order to address this, surveys of young people with NF1 aged 14–24years (n=73), and parents of young people with NF1 (n=55) were developed following interview studies with these groups. The surveys included the Perceived Stigma Questionnaire, Social Comfort Questionnaire, Body Esteem Scale (appearance subscale) and the Subjective Happiness Scale. Young people and parents identified appearance as central to young peoples’ experience of NF1, however no significant difference was found on measures of body esteem, happiness, stigma or social comfort between those young people who reported their NF1 was noticeable to others and those who reported it was not. Findings from the parent survey indicated that their reports of greater perceived noticeability did relate to greater perceived stigma and lower levels of social comfort. Findings highlight the importance of attending to young people’s concerns around appearance in general and managing the possibility of future appearance changes, rather than the current noticeability of NF1

Complex modular architecture around a simple toolkit of wing pattern genes

Identifying the genomic changes that control morphological variation and understanding how they generate diversity is a major goal of evolutionary biology. In Heliconius butterflies, a small number of genes control the development of diverse wing colour patterns. Here, we used full-genome sequencing of individuals across the Heliconius erato radiation and closely related species to characterize genomic variation associated with wing pattern diversity. We show that variation around colour pattern genes is highly modular, with narrow genomic intervals associated with specific differences in colour and pattern. This modular architecture explains the diversity of colour patterns and provides a flexible mechanism for rapid morphological diversification.We acknowledge the University of Puerto Rico, the Puerto Rico INBRE grant P20 GM103475 from the National Institute for General Medical Sciences (NIGMS), a component of the National Institutes of Health (NIH); CNRS Nouraugues and CEBA awards (B.A.C.); National Science Foundation awards DEB-1257839 (B.A.C.), DEB-1257689 (W.O.M.), DEB-1027019 (W.O.M.); awards 1010094 and 1002410 from the Experimental Program to Stimulate Competitive Research (EPSCoR) program of the National Science Foundation (NSF) for computational resources; and the Smithsonian Institution. This research was supported in part by Lilly Endowment, Inc., through its support for the Indiana University Pervasive Technology Institute, and in part by the Indiana METACyt Initiative. The Indiana METACyt Initiative at IU is also supported in part by Lilly Endowment, Inc

Genomic Hotspots for Adaptation: The Population Genetics of Müllerian Mimicry in the Heliconius melpomene Clade

Wing patterning in Heliconius butterflies is a longstanding example of both Müllerian mimicry and phenotypic radiation under strong natural selection. The loci controlling such patterns are “hotspots” for adaptive evolution with great allelic diversity across different species in the genus. We characterise nucleotide variation, genotype-by-phenotype associations, linkage disequilibrium, and candidate gene expression at two loci and across multiple hybrid zones in Heliconius melpomene and relatives. Alleles at HmB control the presence or absence of the red forewing band, while alleles at HmYb control the yellow hindwing bar. Across HmYb two regions, separated by ∼100 kb, show significant genotype-by-phenotype associations that are replicated across independent hybrid zones. In contrast, at HmB a single peak of association indicates the likely position of functional sites at three genes, encoding a kinesin, a G-protein coupled receptor, and an mRNA splicing factor. At both HmYb and HmB there is evidence for enhanced linkage disequilibrium (LD) between associated sites separated by up to 14 kb, suggesting that multiple sites are under selection. However, there was no evidence for reduced variation or deviations from neutrality that might indicate a recent selective sweep, consistent with these alleles being relatively old. Of the three genes showing an association with the HmB locus, the kinesin shows differences in wing disc expression between races that are replicated in the co-mimic, Heliconius erato, providing striking evidence for parallel changes in gene expression between Müllerian co-mimics. Wing patterning loci in Heliconius melpomene therefore show a haplotype structure maintained by selection, but no evidence for a recent selective sweep. The complex genetic pattern contrasts with the simple genetic basis of many adaptive traits studied previously, but may provide a better model for most adaptation in natural populations that has arisen over millions rather than tens of years