Can Volunteers Learn to Prune Trees?

Volunteer pruning programs are becoming an important tool in helping municipal arborists manage the urban forest. To find if volunteers can learn to prune trees well, the ability of volunteers to prune small trees after receiving training was assessed in three different ways, a written exam, a pruning prescription assessment, and a pruning cut assessment. Volunteers were assigned to either an indoor, lecture-based training or an outdoor, hands-on training session. After the training volunteers were asked to complete a written exam to gauge their understanding of the curriculum. Volunteers were then asked to perform a pruning prescription on small street trees indicating where they would prune to remove structural issues and branches growing into signs and walkways. Finally, volunteers were asked to make a removal cut and reduction cut using hand pruners. Volunteers who received indoor training performed significantly better on the written exam. Both training groups performed well on the pruning prescription assessment. At each location, volunteers who received the outdoor training scored significantly higher than the indoor group on their pruning prescription. The type of training received did not affect a volunteer’s ability to make good pruning cuts. These results indicate that, given proper training, volunteers can learn to prune small trees to the satisfaction of an arborist

The Struggle to Make CNS Axons Regenerate: Why Has It Been so Difficult?

Funder: Medical Research CouncilFunder: Wings for LifeFunder: International Foundation for Research in ParaplegiaAbstract: Axon regeneration in the CNS is inhibited by many extrinsic and intrinsic factors. Because these act in parallel, no single intervention has been sufficient to enable full regeneration of damaged axons in the adult mammalian CNS. In the external environment, NogoA and CSPGs are strongly inhibitory to the regeneration of adult axons. CNS neurons lose intrinsic regenerative ability as they mature: embryonic but not mature neurons can grow axons for long distances when transplanted into the adult CNS, and regeneration fails with maturity in in vitro axotomy models. The causes of this loss of regeneration include partitioning of neurons into axonal and dendritic fields with many growth-related molecules directed specifically to dendrites and excluded from axons, changes in axonal signalling due to changes in expression and localization of receptors and their ligands, changes in local translation of proteins in axons, and changes in cytoskeletal dynamics after injury. Also with neuronal maturation come epigenetic changes in neurons, with many of the transcription factor binding sites that drive axon growth-related genes becoming inaccessible. The overall aim for successful regeneration is to ensure that the right molecules are expressed after axotomy and to arrange for them to be transported to the right place in the neuron, including the damaged axon tip

Tomographic reconstruction of velocity anomalies

An approximate inversion formula is proposed for the reconstruction of slowness anomalies in a known depth varying background field. The data are observed travel-time perturbations for reflections from a known planar reflector. The limitations of the formula are discussed and numerical examples are given