No abstract

[1] Number concentrations of submicrometer aerosol particles at altitudes of 8.5-11.3 km were measured along a single flight route between Germany ($50°N, $10°E) and the Indic ($5°N, $80°E) over 3 years using a commercial aircraft platform (project Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container (CARIBIC)). During 41 intercontinental flights ($380 flight hours), more than one million individual particle concentration measurements were made, yielding a comprehensive and unique aerosol data set. Using these data, the first meridional and seasonal probability distributions for ultrafine particles and for Aitken mode plus accumulation mode particles in the upper troposphere (UT) and lower stratosphere (LS) were derived. High particle number concentrations were observed in summer at tropical latitudes over the Arabian Sea and at midlatitudes over Europe, in contrast to lower values in the subtropics over the Middle East. This distribution primarily reflects the vertical transport pattern of the atmosphere. In winter, number concentrations were generally lower. The Intertropical Convergence Zone (ITCZ) was identified as a region of pronounced particle formation, but particle nucleation also occurred in the upper troposphere at midlatitudes. At tropical latitudes, convective transport and photochemistry appear to be the main driving forces for particle formation in the free troposphere. Consistent with these observations, integral length scales calculated from the aerosol data ranged from 6 to 12 km. Compared to particle concentrations in the midlatitudinal upper troposphere, those in the lowermost stratosphere were lower in winter, but equal or higher in summer. This seasonality is likely caused by stronger in-mixing of upper tropospheric air in summer.

Using a homology-based cloning strategy we have identified five members of the Trk family in the zebrafish Danio rerio. They are homologous to the three mammalian Trk receptors in their conserved intracellular kinase regions and the organization of their extracellular regions. The five trk genes are differentially expressed in the developing brain, spinal cord, cranial ganglia, and retina. Full-length forms of three of the trk genes are expressed when neurons pioneer the major axon tracts, whereas the two other trk genes have a later onset of expression. Truncated transcripts and forms containing an extracellular juxtamembrane region insert were found. The degree of sequence variation and expression differences within the family suggest that each of the five zebrafish Trk receptors have a functionally distinct role. These findings demonstrate that the vertebrate Trk family is larger than previously appreciated.