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  • Author or Editor: V. Coetzee x
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Abstract  

The possible application of cyclotron-produced fast neutrons to activation analysis for oxygen based on the16O(n, p)16N reaction has been investigated. Neutrons were produced by bombarding a thick beryllium target with 22 to 45 MeV deuterons. It was found that the sensitivity increases rapidly with the energy of the deuterons. Using 45 MeV deuterons and a 10 μA beam current a sensitivity of about 20 counts per 1 μg oxigen could be achieved, enabling the determination of less than 1 μg oxigen. In a direct comparison it was experimentally established that the sensitivity for cyclotron-produced neutrons assuming a deuteron beam of about 10 μA, is up to two orders of magnitude higher than that achievable for 14 MeV neutrons with a flux of about 1010 n/s. The interference of fluorine is at about the same level for both the cyclotron-produced and 14 MeV neutrons. Using cyclotron-produced fast neutrons in the investigated energy range, sodium and magnesium can also interfere, but only to a very much lower extent.

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Authors: D. E. Re, V. Coetzee, D. Xiao, D. Buls, B. P. Tiddeman, L. G. Boothroyd and D. I. Perrett

Abstract

Experience-dependent changes in mate choice preferences may confer an evolutionary benefit by shifting preferences towards traits that are advantageous for specific environments. Previous studies have demonstrated that prolonged exposure to one type of face biases perceptions of subsequently viewed faces and exposure to one type of body biases perceptions of subsequently viewed bodies. We tested whether preferences in facial adiposity were affected by viewing heavy or light bodies. We first assessed facial adiposity preferences by asking Caucasian participants (n = 59) to transform three-dimensional female Caucasian faces along a body mass index (BMI) continuum until they reached optimal attractiveness. Participants then viewed heavy- or light-bodied two-dimensional images with the faces cropped out before repeating the face preference task. Male and female participants who viewed heavy bodies shifted preferences toward significantly higher facial adiposity, while those who viewed the light bodies showed no significant overall shift. These results provide evidence that adaptation to certain body types affects subsequent preferences for facial adiposity, and suggest that adaptation to one body domain may affect preferences in other body domains.

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