Investigating hookworm genomes by comparative analysis of two Ancylostoma species

Background Hookworms, infecting over one billion people, are the mostly closely related major human parasites to the model nematode Caenorhabditis elegans. Applying genomics techniques to these species, we analyzed 3,840 and 3,149 genes from Ancylostoma caninum and A. ceylanicum. Results Transcripts originated from libraries representing infective L3 larva, stimulated L3, arrested L3, and adults. Most genes are represented in single stages including abundant transcripts like hsp-20 in infective L3 and vit-3 in adults. Over 80% of the genes have homologs in C. elegans, and nearly 30% of these were with observable RNA interference phenotypes. Homologies were identified to nematode-specific and clade V specific gene families. To study the evolution of hookworm genes, 574 A. caninum / A. ceylanicum orthologs were identified, all of which were found to be under purifying selection with distribution ratios of nonsynonymous to synonymous amino acid substitutions similar to that reported for C. elegans / C. briggsae orthologs. The phylogenetic distance between A. caninum and A. ceylanicum is almost identical to that for C. elegans / C. briggsae. Conclusion The genes discovered should substantially accelerate research toward better understanding of the parasites' basic biology as well as new therapies including vaccines and novel anthelmintics

The Radial Velocity Experiment (rave): Second Data Release

We present the second data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity, and rotational velocity) of up to one million stars using the 6 dF multi-object spectrograph on the 1.2 m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO). The RAVE program started in 2003, obtaining medium resolution spectra (median R = 7500) in the Ca-triplet region (8410-8795 ) for southern hemisphere stars drawn from the Tycho-2 and SuperCOSMOS catalogues, in the magnitude range 9 < I < 12. Following the first data release, the current release doubles the sample of published radial velocities, now containing 51,829 radial velocities for 49,327 individual stars observed on 141 nights between 2003 April 11 and 2005 March 31. Comparison with external data sets shows that the new data collected since 2004 April 3 show a standard deviation of 1.3 km s-1, about twice as good as for the first data release. For the first time, this data release contains values of stellar parameters from 22,407 spectra of 21,121 individual stars. They were derived by a penalized χ2 method using an extensive grid of synthetic spectra calculated from the latest version of Kurucz stellar atmosphere models. From comparison with external data sets, our conservative estimates of errors of the stellar parameters for a spectrum with an average signal-to-noise ratio (S/N) of 40 are 400 K in temperature, 0.5 dex in gravity, and 0.2 dex in metallicity. We note however that, for all three stellar parameters, the internal errors estimated from repeat RAVE observations of 855 stars are at least a factor 2 smaller. We demonstrate that the results show no systematic offsets if compared to values derived from photometry or complementary spectroscopic analyses. The data release includes proper motions from Starnet2, Tycho-2, and UCAC2 catalogs and photometric measurements from Tycho-2 USNO-B, DENIS, and 2MASS. The data release can be accessed via the RAVE Web site: http://www.rave-survey.org and through CDS

Resonant dipole-dipole interaction in the presence of dispersing and absorbing surroundings

Within the framework of quantization of the macroscopic electromagnetic field, equations of motion and an effective Hamiltonian for treating both the resonant dipole-dipole interaction between two-level atoms and the resonant atom-field interaction are derived, which can suitably be used for studying the influence of arbitrary dispersing and absorbing material surroundings on these interactions. The theory is applied to the study of the transient behavior of two atoms that initially share a single excitation, with special emphasis on the role of the two competing processes of virtual and real photon exchange in the energy transfer between the atoms. In particular, it is shown that for weak atom-field interaction there is a time window, where the energy transfer follows a rate regime of the type obtained by ordinary second-order perturbation theory. Finally, the resonant dipole-dipole interaction is shown to give rise to a doublet spectrum of the emitted light for weak atom-field interaction and a triplet spectrum for strong atom-field interaction.Comment: 15 pages, 1 figure, RevTE