EXTENSIONS FROM MODELS OF SIMPLE SHORT PERIOD GRAIN BOUNDARIES

La structure et l'énergie de deux joints intergranulaires, avec des angles de 36,9°, entre les plans (100) pour l'un et entre les plans (110) pour l'autre, ont été calculées pour l'or et trois alliages or-cuivre. Les trois alliages étaient : a) un alliage ordonné 50-50, b) un alliage d'or contenant un atome de cuivre pour chaque période de la structure de joint, c) un alliage biphasé composé d'un grain de cuivre pur et d'un grain d'or pur séparés par un joint de grains. Si, dans le système Cu-Au, caractérisé par une solubilité complète, les structures des joints de grains trouvées ne sont pas sensibles à la composition de l'alliage, les atomes étrangers ont cependant tendance a ségréger au joint, dans des alliages dilués. Plusieurs modèles de structure des joints intergranulaires sont discutés et une nouvelle description de ces structures est proposée.The structure and energy of two 36.9° grain boundaries, one between (100) planes and the other between (110) planes, were calculated for gold and three gold-copper alloys. Three types of alloys were examined : (a) an ordered alloy containing an equal number of gold and copper atoms, (b) a gold rich alloy in which only one copper impurity atom was associated With each periodic unit of boundary structure, and (c) a two phase alloy with an interphase boundary between a pure gold grain and a pure copper grain. In this alloy system, which is characterized by a high degree of solubility, the grain boundary structures were not found to be sensitive to the alloying conditions ; however, there was a tendency in dilute solution for foreign atoms to segregate to the grain boundary. Several of the existing methods of describing the grain boundary structure are discussed and a new alternative method of describing the structure is proposed

The development of delinquency during adolescence: a comparison of missing data techniques

Reinecke J, Weins C. The development of delinquency during adolescence: a comparison of missing data techniques. Quality & Quantity. 2013;47(6):3319-3334.Conclusions on the development of delinquent behaviour during the life-course can only be made with longitudinal data, which is regularly gained by repeated interviews of the same respondents. Missing data are a problem for the analysis of delinquent behaviour during the life-course shown with data from an adolescents’ four-wave panel. In this article two alternative techniques to cope with missing data are used: full information maximum likelihood estimation and multiple imputation. Both methods allow one to consider all available data (including adolescents with missing information on some variables) in order to estimate the development of delinquency. We demonstrate that self-reported delinquency is systematically underestimated with listwise deletion (LD) of missing data. Further, LD results in false conclusions on gender and school specific differences of the age–crime relationship. In the final discussion some hints are given for further methods to deal with bias in panel data affected by the missing process