Different sizes and arrangements of solar bottle bulbs might greatly affect the lighting delivered and there is no general agreement on the best interior bottle exposure levels. This study was undertaken to examine the lighting performance of three prototype solar bottle bulbs and to compare their performance at three different interior bottle exposure levels: one-third, half and two-thirds. A solar bottle bulb made of one 1.5 litre bottle proved to be better than a solar bottle bulb made of three 0.5 litre bottles. In terms of interior bottle exposure levels, the half level performed the best. Some inexplicable phenomena were also observed with recommendations for further study.

The mechanism of the hook effect in a two site immunometric assay of hepatitis B surface antigen (HBsAg) was studied using a novel method. The results showed that HBsAg dissociated from immobilized anti-HBsAg at low as well as high doses of antigen (Ag). This probably was not due to lack of immobilized antibody (Ab) or dissociation of HBsAg non-specifically bound to the immobilized Ab. The dissociated Ag sequestered the labelled Ab in the second reaction and contributed to the decrease in percent binding (B%) of the assay and thus the hook effect. The dissociated Ag could contaminate the recovered pooled labelled Ab in recycled assay and give rise to high non-specific binding. Prolonged washing decreased the side reaction but also the B% of the assay.

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