OVI Emission in the Halos of Edge-on Spiral Galaxies

We have used the Far Ultraviolet Spectroscopic Explorer to search for OVI 1031.926, 1037.617 A emission in the halos of the edge-on spiral galaxies NGC4631 and NGC891. In NGC4631, we detected OVI in emission toward a soft X-ray bubble above a region containing numerous Halpha arcs and filaments. The line-of-sight component of the motion of the OVI gas appears to match the underlying disk rotation. The observed OVI luminosities can account for 0.2-2% of the total energy input from supernovae (assuming a full OVI emitting halo) and yield mass flux cooling rates between 0.48 and 2.8 M_sun/yr depending on the model used in the derivations. Based on these findings, we believe it is likely that we are seeing cooling, galactic fountain gas. No emission was detected from the halo of NGC891, a galaxy in a direction with considerably high foreground Galactic extinction.Comment: accepted for publication in ApJ, 16 pages including 4 figure

'Exit' in deeply divided societies: regimes of discrimination in Estonia and Latvia and the potential for Russophone migration

Hirschman’s model of ‘exit’ envisages that mass migration can communicate feedback to a state and elicit modifying policy behaviour. The regimes of discrimination against Russophones in Estonia and Latvia are examined to demonstrate that in certain conditions of inter-ethnic conflict the model does not work as predicted. In deeply divided societies the mass migration of a minority can be intentionally promoted by a majority regime of discrimination and thus does not perform a feedback function. Equally, in such conditions migration may operate as a safety valve to release the build up of minority antagonisms against the discriminatory regimes. The cases of Estonia and Latvia also illustrate the limitations of international conditionality from the EU and OSCE to prevent anti-minority policies, when there is a lack of international commitment and when governing elites resist. Given the lack of political will in Estonia and Latvia to modify the regimes of discrimination, and the poor prospects for integration or assimilation, the article predicts a significant out-migration by Russophones to other EU member states when restrictions on freedom of movement are eased after the transitional period

Semi-automated counting of axon regeneration in poly(lactide co-glycolide) spinal cord bridges.

BackgroundSpinal cord injury (SCI) is a debilitating event with multiple mechanisms of degeneration leading to life-long paralysis. Biomaterial strategies, including bridges that span the injury and provide a pathway to reconnect severed regions of the spinal cord, can promote partial restoration of motor function following SCI. Axon growth through the bridge is essential to characterizing regeneration, as recovery can occur via other mechanisms such as plasticity. Quantitative analysis of axons by manual counting of histological sections can be slow, which can limit the number of bridge designs evaluated. In this study, we report a semi-automated process to resolve axon numbers in histological sections, which allows for efficient analysis of large data sets.New methodAxon numbers were estimated in SCI cross-sections from animals implanted with poly(lactide co-glycolide) (PLG) bridges with multiple channels for guiding axons. Immunofluorescence images of histological sections were filtered using a Hessian-based approach prior to threshold detection to improve the signal-to-noise ratio and filter out background staining associated with PLG polymer.ResultsSemi-automated counting successfully recapitulated average axon densities and myelination in a blinded PLG bridge implantation study.Comparison with existing methodsAxon counts obtained with the semi-automated technique correlated well with manual axon counts from blinded independent observers across sections with a wide range of total axons.ConclusionsThis semi-automated detection of Hessian-filtered axons provides an accurate and significantly faster alternative to manual counting of axons for quantitative analysis of regeneration following SCI

Semi-automated counting of axon regeneration in poly(lactide co-glycolide) spinal cord bridges.

BackgroundSpinal cord injury (SCI) is a debilitating event with multiple mechanisms of degeneration leading to life-long paralysis. Biomaterial strategies, including bridges that span the injury and provide a pathway to reconnect severed regions of the spinal cord, can promote partial restoration of motor function following SCI. Axon growth through the bridge is essential to characterizing regeneration, as recovery can occur via other mechanisms such as plasticity. Quantitative analysis of axons by manual counting of histological sections can be slow, which can limit the number of bridge designs evaluated. In this study, we report a semi-automated process to resolve axon numbers in histological sections, which allows for efficient analysis of large data sets.New methodAxon numbers were estimated in SCI cross-sections from animals implanted with poly(lactide co-glycolide) (PLG) bridges with multiple channels for guiding axons. Immunofluorescence images of histological sections were filtered using a Hessian-based approach prior to threshold detection to improve the signal-to-noise ratio and filter out background staining associated with PLG polymer.ResultsSemi-automated counting successfully recapitulated average axon densities and myelination in a blinded PLG bridge implantation study.Comparison with existing methodsAxon counts obtained with the semi-automated technique correlated well with manual axon counts from blinded independent observers across sections with a wide range of total axons.ConclusionsThis semi-automated detection of Hessian-filtered axons provides an accurate and significantly faster alternative to manual counting of axons for quantitative analysis of regeneration following SCI