RESUMO
Meteorites provide a sample of Solar System bodies and so constrain the types of objects that have collided with Earth over time. Meteorites analysed to date, however, are unlikely to be representative of the entire population and it is also possible that changes in their nature have occurred with time. Large objects are widely believed to be completely melted or vaporized during high-angle impact with the Earth. Consequently, identification of large impactors relies on indirect chemical tracers, notably the platinum-group elements. Here we report the discovery of a large (25-cm), unaltered, fossil meteorite, and several smaller fragments within the impact melt of the giant (> 70 km diameter), 145-Myr-old Morokweng crater, South Africa. The large fragment (clast) resembles an LL6 chondrite breccia, but contains anomalously iron-rich silicates, Fe-Ni sulphides, and no troilite or metal. It has chondritic chromium isotope ratios and identical platinum-group element ratios to the bulk impact melt. These features allow the unambiguous characterization of an impactor at a large crater. Furthermore, the unusual composition of the meteorite suggests that the Morokweng asteroid incorporated part of the LL chondrite parent body not represented by objects at present reaching the Earth.
RESUMO
Early education of children with hearing impairments has been carried out in the FRG for the past ca. 40 years using a variety of different educational concepts. One of these concepts is the natural auditory-verbal approach. By supporting the development of hearing, even amongst children with profound hearing impairments, it stakes the claim of being capable of initiating the children's development of natural auditory-verbal skills, which are then comparable to those of children with normal hearing. Nevertheless, to this date, no empirical study of the approach and its measure of success had ever been undertaken. During the course of this study, the measures involved in a hearing-oriented system of early education were comprehensively examined. The analysis was performed on the advancements made in the natural auditory-verbal skills of infants suffering a loss of hearing of 90 dB or more and who were educated in such a way. The study comprised 103 children with profound hearing impairments, who were younger than 24 months old at the time the study began. Their respective developments were followed in three separate surveys between 1996 and 1998. The results were analysed using bivariate as well as statistical correlation methods. The children's development is impeded by such factors as late initial diagnosis; delayed supply of hearing aids and late commencement of early education; poorly-adjusted hearing aids and short periods of wearing them. A system of early education that is only to a very limited degree hearing-oriented, and a family environment where little is spoken and where the child's auditory disability receives only scant attention, may also play a part. On the other hand, under favourable circumstances, even children with profound hearing-impairments may attain a development level of natural auditory-verbal skills which corresponds to that of children who can hear well-perhaps with a certain time-delay, and certainly involving a greater effort on the part of the children, but basically, in the same natural way and with a very similar quality of results. The early education system must urgently be improved by the introduction of screening for new-born infants. As far as devices are concerned, the cochlear-implant (CI) will very soon be standard equipment for infants with profound hearing-impairments. Within institutional facilities, there is a broad consensus that the goal of these measures consists of the development of speech communication skills in children. In practice, however, the strategies for realising this goal are not only very different, but also, partly, have downright counterproductive effects.
