8,257 research outputs found

    Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield

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    Tree root pruning is a potential tool for managing below-ground competition when trees and crops are grown together in agroforestry systems. This study investigates its effects on growth and root distribution of Alnus acuminata (HB & K), Casuarina equisetifolia (L), Grevillea robusta (A. Cunn. ex R. Br), Maesopsis eminii (Engl.), and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was re-opened and roots re-cut at 50 and 62 months after planting. Effects on tree growth and root distribution were assessed over a 3 year period, and crop yield after the third root pruning at 62 months is reported here. Overall, root pruning had only a slight effect on tree growth: height growth was unaffected and diameter growth was reduced by only 4 %. A substantial amount of root re-growth was observed by 11 months after pruning. Tree species varied in the number and distribution of their roots, and Casuarina and Markhamia had considerably more roots per unit of trunk volume than the other tree species, especially in the surface soil layers. Casuarina and Maesopsis were the most competitive tree species with crops and Grevillea and Markhamia the least. Crop yield data provides strong evidence of the redistribution of root activity following root pruning, so that competition increased on the unpruned side of tree rows. Thus, one-sided root pruning will only be of use to farmers in a few circumstances. Key words: Alnus acuminata, Casuarina equisetifolia, Grevillea robusta, Maesopsis eminii, Markhamia lutea, root distribution, root functio

    Non-rigid registration of breast surfaces using the laplace and diffusion equations

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    A semi-automated, non-rigid breast surface registration method is presented that involves solving the Laplace or diffusion equations over undeformed and deformed breast surfaces. The resulting potential energy fields and isocontours are used to establish surface correspondence. This novel surface-based method, which does not require intensity images, anatomical landmarks, or fiducials, is compared to a gold standard of thin-plate spline (TPS) interpolation. Realistic finite element simulations of breast compression and further testing against a tissue-mimicking phantom demonstrate that this method is capable of registering surfaces experiencing 6 - 36 mm compression to within a mean error of 0.5 - 5.7 mm

    Belief in karma is associated with perceived (but not actual) trustworthiness

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    Believers of karma believe in ethical causation where good and bad outcomes can be traced to past moral and immoral acts. Karmic belief may have important interpersonal consequences. We investigated whether American Christians expect more trustworthiness from (and are more likely to trust) interaction partners who believe in karma. We conducted an incentivized study of the trust game where interaction partners had different beliefs in karma and God. Participants expected more trustworthiness from (and were more likely to trust) karma believers. Expectations did not match actual behavior: karmic belief was not associated with actual trustworthiness. These findings suggest that people may use others’ karmic belief as a cue to predict their trustworthiness but would err when doing so
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