In the Brits area of the Bushveld Complex, the stratigraphically lowermost magnetitite layer of the Upper Zone is underlain by an anorthosite containing discrete, euhedral magnetite crystals, measuring 0.1–0.3 mm in diameter, which form thin layers (1 mm-1 cm thick) and laminae (commonly one grain in thickness). Discordant relationships between laminae and layers indicate a consistent younging direction upwards towards the contact with the overlying magnetitite. Our interpretation is that these crystals are cumulus and have escaped modification by postcumulus overgrowth. They also record, in places, the morphology of the floor onto which they accumulated. Their preservation is largely attributed to adcumulus growth of plagioclase before, during and after, accumulation, but may also indicate that there was only a limited supply of magnetite to the floor, thus precluding grain contact and prohibiting grain enlargement. The results of a study of compositional variations across individual plagioclase grains suggest that the presence of magnetite within the crystallising mush hindered the development of an ideal plagioclase adcumulate.

In 1990, 13 regionally based Behaviour Intervention Support Teams (BISTs) were established in Victoria to assist agencies providing support to persons with an intellectual disability who exhibited challenging behaviour. A primary function of the BISTs was to conduct intensive interventions for clients with severe challenging behaviours. The outcomes of the interventions conducted by eight of these teams were monitored over the period from 1991 to 1993. During this time, a total of 134 such interventions were completed by the teams. Many outcome measures were used for each intervention. These included direct observational measures of the challenging behaviours, measures of skill acquisition by the clients, and satisfaction with the results by caregivers. It was concluded that the interventions resulted in a high rate of success (approximately 75%). Additionally, it was concluded that the use of regionally based specialist teams was an effective way of treating severe challenging behaviours that had previously proven difficult to manage.

In 1990 a number of regionally based Behaviour Intervention Support Teams (BISTs) were established in Victoria to assist agencies providing support to persons with an intellectual disability who exhibited challenging behaviour. A primary function of the BISTs was to conduct intensive interventions for clients with severe challenging behaviours. A cost-benefit analysis of these interventions was carried out. It was found that the existence of a severe challenging behaviour resulted in an additional cost to the service system of an average $40,510 per annum. In contrast, the cost of a single intensive intervention conducted by a BIST was $5,725. Allowing for the fact that not all intensive interventions were successful, it was still concluded that the interventions conducted by the BISTs were cost efficient. Methodological difficulties associated with the cost-benefit analysis are discussed.

The model of addiction proposed by Redish et al. shows a lack of fit with recent data and models in psychological studies of addiction. In these dual process models, relatively automatic appetitive processes are distinguished from explicit goal-directed expectancies and motives, whereas these are all grouped together in the planning system in the Redish et al. model. Implications are discussed.

Luminescence quenching experiments on oriented and drop-cast poly(phenylene vinylene), (PPV), films identify the excitons in these polymer films as Wannier-Mott excitons. The data are interpreted in terms of a distribution of exciton binding energies (Eb ). We find that the width of this distribution is well correlated with the degree of structural disorder. The relatively small mean EbEb , approximately 60 meV, results in field-induced exciton disociation that limits the quantum efficiency obtained from polymer-based light emitting diodes (PLEDs) which typically are operated at applied fields of 106 V/cm or greater where the field-induced exciton disociation is significant. We present data and analysis that support these conclusions, as well as a discussion on the implications of our findings on polymer-based display technology.

Purine-rich exonic splicing enhancers (ESEs) have been identified in many alternatively spliced exons. Alternative splicing of several ESE-containing exons has been shown to depend on subsets of the SR protein family of pre-mRNA splicing factors. In this report, we show that purified SR protein family member SRp55 by itself binds a 30-nt ESE-containing exon, the alternatively spliced exon 5 of avian cardiac troponin T. We show that purified SRp55 binds specifically to this RNA sequence with an apparent Kd of 60 nM as assayed by gel mobility retardation experiments. Mutations in the exon 5 sequence that increase or decrease exon 5 inclusion in vivo and in vitro have correspondingly different affinities for SRp55 in our assays. The exon 5 sequence contains two purine-rich motifs, common to many ESEs, and both are required for SRp55 binding. Hill plot analysis of binding titration reactions indicates that there is a cooperative binding of at least two SRp55 proteins to the exon sequence. Chemical modification interference studies using kethoxal show that SRp55 binding to exon 5 requires the N1 and/or the N2 of almost every G residue in the exon. Dimethylsulfate modification interference studies indicate that none of the N1 positions of A residues in the exon are important for binding. We postulate that SRp55 may recognize both primary sequence and RNA secondary structural elements within pre-mRNA.

The use of a rotation pedicled flap, entitled the ‘Singapore Swing’, comprising temporalis fascia and mastoid periosteum, is presented as a new method of promoting healing in ‘open’ mastoid surgery for chronic ear discharge. Cadaver studies show that the main blood supply of the flap is derived from a branch of the postauricular artery which enters the pedicle near the mastoid tip. A review of the first 14 operations showed complete healing with dry ears and intact tympanic membranes in all instances, three cases requiring secondary grafting of residual perforations. We consider the results sufficiently encouraging to merit an extended trial ofthe technique.

Educational and Developmental Psychologists are frequently required to assess a person for the presence or absence of an intellectual disability. The assessment is important as the availability of particular services is usually tied to a formal determination that an intellectual disability is present. A key element to deciding on the existence of an intellectual disability is the presence of a level of intelligence below a predetermined level. Although definitions of intellectual disability usually refer only to significant sub-average intellectual functioning, the actual cut-off score used to indicate this level of intellectual functioning has varied over time. Whatever that cut-off level is determined to be, there are technical difficulties that make assessment of intellectual functioning less than straightforward. These difficulties result from (a) standardized tests having different standard deviations, resulting in differing scores for cut-off levels based on standard deviation calculations, (b) different standardized tests giving different scores when administered to the same person, (c) less than perfect test reliability creating uncertainty about whether the measured intelligence corresponds with the actual intelligence of the individual being assessed, and (d) many people having impairments in sight, hearing, or motor function that make the standardized administration of tests impossible. It is recommended that educational psychologists be familiar with these issues so that they can make decisions that satisfy social justice objectives. Furthermore, it is argued that familiarity with these issues will help psychologists to defend their decisions when it is necessary.