The Antarctic ozone hole during 2011

The Antarctic ozone hole of 2011 is reviewed from a variety of perspectives, making use of various data and analyses. The ozone hole of 2011 was relatively large in terms of maximum area, minimum ozone level and total ozone deficit, being ranked amongst the top ten in terms of severity of the 32 ozone holes adequately characterised since 1979. In particular, the estimated integrated ozone mass effectively removed within the ozone hole of 2011 was 2119 Mt, which is the 7th largest deficit on record and 82 per cent of the peak value observed in 2006. The key factors in promoting the extent of Antarctic ozone loss in 2011 were the relatively low temperatures that occurred in the lower stratosphere of the polar cap region over most of the year, and the fact that the stratospheric vortex was relatively strong and stable, at least up to mid-spring. Dynamical disturbance of the polar vortex from mid-spring increased Antarctic ozone levels in the latter part of the ozone hole’s evolution and helped to limit the overall severity of depletion. Through examination of regression of various ozone metrics against expected levels of equivalent effective stratospheric chlorine, we suggest that recent changes in averaged ozone levels over Antarctica show some evidence of the recovery expected due to international controls on the manufacture of ozone depleting chemicals, albeit at a statistically low level of confidence due to the influence of meteorological factors that largely dictate year-to-year variability of Antarctic ozone loss

The Antarctic ozone during 2010

The Antarctic ozone hole of 2010 is reviewed from a variety of perspectives, making use of various data and analyses. Based on total column ozone metrics, the 2010 ozone hole was one of the smallest in the past fifteen–twenty years. The main influence on the size of the ozone hole was relatively warm temperatures in the Antarctic lower stratosphere which impeded ozone depletion in the austral spring. The warm winter temperatures were associated with a significant dynamical disturbance in the mid- and high latitude upper stratosphere during July which included a substantial warming of the mid- and upper extratropical stratosphere, a deceleration of zonal winds and a cooling in the polar mesosphere. The disturbance was likely influenced by the phase of the Quasi-Biennial Oscillation (QBO) which favoured a weak and disturbed polar vortex in the winter months. The winter warming also resulted in significant off-pole displacement and weakening of the polar vortex in the mid- to upper stratosphere, producing a long-lasting increase in the overburden of ozone and weakening ozone hole metrics based on total column ozone measurements. Ozone loss in the lower stratosphere was less markedly affected by this dynamical activity, and was similar to other recent years. A notable feature was the reduction in dynamical disturbances of the polar vortex after September, when the QBO moved into a strongly eastward phase. During the late spring and early summer, stratospheric temperatures warmed more slowly than in recent years, and this produced one of the longest-lasting ozone holes yet observed which eventually disappeared in the last week of December. The relatively low ozone levels in December resulted in unusually high surface ultraviolet fluxes as measured on the coast of East Antarctica

The Antarctic ozone hole during 2008 and 2009

The Antarctic ozone holes of 2008 and 2009 are reviewed from various perspectives, making use of a range of Australian data and analyses. In both years, ozone holes formed that were fairly typical of those observed since the late 1990s. The ozone hole of 2008 was somewhat larger than that of 2009. In 2009 the ozone hole developed more rapidly, but did not last as long as in 2008, particularly in the lower stratosphere

Visualizing Lipid Raft Dynamics and Early Signaling Events during Antigen Receptor-mediated B-Lymphocyte Activation

Recent biochemical evidence indicates that an early event in signal transduction by the B-cell antigen receptor (BCR) is its translocation to specialized membrane subdomains known as lipid rafts. We have taken a microscopic approach to image lipid rafts and early events associated with BCR signal transduction. Lipid rafts were visualized on primary splenic B lymphocytes from wild-type or anti-hen egg lysozyme BCR transgenic mice, and on a mature mouse B-cell line Bal 17 by using fluorescent conjugates of cholera toxin B subunit or a Lyn-based chimeric protein, which targets green fluorescent protein to the lipid raft compartment. Time-lapse imaging of B cells stimulated via the BCR with the antigen hen egg lysozyme, or surrogate for antigen anti-IgM, demonstrated that lipid rafts are highly dynamic entities, which move laterally on the surface of these cells and coalesce into large regions. These regions of aggregated lipid rafts colocalized with the BCR and tyrosine-phosphorylated proteins. Microscopic imaging of live B cells also revealed an inducible colocalization of lipid rafts with the tyrosine kinase Syk and the receptor tyrosine phosphatase CD45. These two proteins play indispensable roles in BCR-mediated signaling but are not detectable in biochemically purified lipid raft fractions. Strikingly, BCR stimulation also induced the formation of long, thread-like filopodial projections, similar to previously described structures called cytonemes. These B-cell cytonemes are rich in lipid rafts and actin filaments, suggesting that they might play a role in long-range communication and/or transportation of signaling molecules during an immune response. These results provide a window into the morphological and molecular organization of the B-cell membrane during the early phase of BCR signaling