An unfitted discontinuous Galerkin scheme for conservation laws on evolving surfaces

Motivated by considering partial differential equations arising from conservation laws posed on evolving surfaces, a new numerical method for an advection problem is developed and simple numerical tests are performed. The method is based on an unfitted discontinuous Galerkin approach where the surface is not explicitly tracked by the mesh which means the method is extremely flexible with respect to geometry. Furthermore, the discontinuous Galerkin approach is well-suited to capture the advection driven by the evolution of the surface without the need for a space-time formulation, back-tracking trajectories or streamline diffusion. The method is illustrated by a one-dimensional example and numerical results are presented that show good convergence properties for a simple test problem

Algometry to measure pain threshold in the horse's back - An in vivo and in vitro study

Abstract Background The aim of this study was to provide information on algometric transmission of pressure through the dorsal thoracolumbar tissues of the equine back. Using a commercially available algometer, measurements were carried out with six different tips (hemispheric and cylindrical surfaces, contact areas 0.5 cm2, 1 cm2, and 2 cm2). In nine live horses the threshold of pressure that lead to any reaction was documented. In postmortem specimens of five euthanized horses the transmission of algometer pressure onto a pressure sensor placed underneath the dorsal thoracolumbar tissues at the level of the ribs or the transverse lumbar processes respectively was measured. Results Algometer tips with a contact area of 1 cm2 led to widely similar results irrespective of the surface shape; these measurements also had the lowest variance. Contact areas of 0.5 cm2 resulted in a lower pressure threshold, and those of 2 cm2 resulted in a higher pressure threshold. The hemispheric shape of the contact area resulted in a higher pressure threshold, than the cylindrical contact area. Compared to the thoracic region, a significantly higher pressure threshold was found in the lumbar region in the live horses. This result corresponds to the increased tissue thickness in the lumbar region compared to the thoracic region, also documented as less pressure transmission in the lumbar region on the in vitro specimens. Conclusions Algometry is an easily practicable and well tolerated method to quantify pain but it is important to consider the many factors influencing the results obtained

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Postmortem angiography after vascular perfusion with diesel oil and a lipophilic contrast agent.

OBJECTIVE: The objective of our study was to establish optimal perfusion conditions for high-resolution postmortem angiography that would permit dynamic visualization of the arterial and venous systems. MATERIALS AND METHODS: Cadavers of two dogs and one cat were perfused with diesel oil through a peristaltic pump. The lipophilic contrast agent Lipiodol Ultra Fluide was then injected, and angiography was performed. The efficiency of perfusion was evaluated in the chick chorioallantoic membrane. RESULTS: Vessels could be seen up to the level of the smaller supplying and draining vessels. Hence, both the arterial and the venous sides of the vascular system could be distinguished. The chorioallantoic membrane assay revealed that diesel oil enters microvessels up to 50 microm in diameter and that it does not penetrate the capillary network. CONCLUSION: After establishing a postmortem circulation by diesel oil perfusion, angiography can be performed by injection of Lipiodol Ultra Fluide. The resolution of the images obtained up to 3 days after death is comparable to that achieved in clinical angiography