Orphanhood, child fostering and the AIDS epidemic in rural Tanzania

The AIDS epidemic has caused an increase in adult mortality and consequently an increase in the numbers of orphaned children. Data were used from the Kisesa Community Study in northwest Tanzania, to assess the prevalence and consequences of orphanhood in the context of existing child care practices in a rural area with moderately high HIV-prevalence. This study was carried out in a ward with about 20,000 people with HIV prevalence of 6.2 per cent among adults 15-44 years and slightly over one-third of adult deaths associated with HIV/AIDS. Seven point six per cent of children under 15 and 8.9 per cent of children under 18 had lost one or both parents. Child fostering was very common. Virtually all orphans and foster-children were cared for by members of the extended family, often the maternal grandparents: 14 per cent of households had at least one orphan. Such households did not have a lower economic status, but had a less favourable dependency ratio. Households with orphans were also more likely to be female-headed. Follow-up mortality rates were similar among orphans, foster-children and other children, for both sexes. Mobility was much higher among orphans and foster-children, and orphans and foster-children had somewhat lower school attendance rates: lower enrolment and higher dropout rates. The problem of rapidly increasing numbers of orphans needs to be considered in the context of previously high levels of adult mortality, child-fostering practices and general poverty. The extended family seems to be able to absorb the increase in orphans, because caring for children of other members of the family is widespread, whether the parents are alive or dead. This study yields no evidence that orphans as a group are disadvantaged, although certain subgroups of orphans or orphan households may be more vulnerable and in need of support

Application of convergent-beam electron diffraction to the determination of grain boundary structures

Convergent-beam electron diffraction (CBED) has been applied in grain boundary structure determination, both for horizontal and vertical boundaries in thin specimens. First the relation between bicrystal symmetry and CBED pattern symmetry is developed for the two types of boundaries. These results are subsequently employed for a structure determination of twin boundaries in Au and Si. The CBED patterns from twinned bicrystals obtained experimentally are compared with computer-simulated patterns, for the case of a horizontal twin boundary in Au and Si. Finally the symmetry of CBED patterns from vertical twin boundaries in Si is analysed and found to depend on whether a static incident beam or a rocking-beam geometry is employed.La diffraction en faisceau convergent (DFC) a été appliquée à la détermination des structures de joints de grains placés horizontalement et verticalement dans une lame mince. D'abord, on établit la relation entre symétrie du bicristal et symétrie du diagramme DFC pour les deux types de joints. Les résultats sont ensuite appliqués pour déterminer la structure de joints de macle dans Au et Si. Les diagrammes DFC de bicristaux maclés sont comparés avec des diagrammes calculés pour un joint de macle horizontal dans Au et Si. Finalement, la symétrie des diagrammes DFC pour des joints de macle verticaux dans Si est analysée ; elle varie selon que l'on emploie un faisceau incident statique ou oscillant

Statistical thermodynamics of vacancies in binary alloys

Applied Science

TEM DETERMINATION OF INCOHERENT TWIN-BOUNDARY STRUCTURE IN L12 ORDERED ALLOYS

The structure of incoherent Σ=3 twin boundaries in the L12 ordered alloy Cu3Au is investigated employing TEM. The boundary planes are found to vary about ten degrees from a {112} plane. Employing the TEM method of α-fringes common diffraction vectors are used for determining the rigid-body translation between the two crystals at the boundary. No dilatation has been found at a (754) incoherent twin boundary within experimental error. Four grain boundary areas having different translations that preserve the density in the boundary are demonstrated, separated from each other by an antiphase boundary on one side of the boundary plane