Fluorescent protein tagging confirms the presence of ribosomal proteins atDrosophilapolytene chromosomes

\ud \ud Most ribosomal proteins (RPs) are stoichiometrically incorporated into ribosomal subunits and play essential roles in ribosome biogenesis and function. However, a number of RPs appear to have non-ribosomal functions, which involve direct association with pre-mRNA and transcription factors at transcription sites. The consensus is that the RPs found at these sites are off ribosomal subunits, but observation that different RPs are usually found together suggests that ribosomal or ribosomal-like subunits might be present. Notably, it has previously been reported that antibodies against 20 different RPs stain the same Pol II transcription sites in Drosophila polytene chromosomes. Some concerns, however, were raised about the specificity of the antibodies. To investigate further whether RPs are present at transcription sites in Drosophila, we have generated several transgenic flies expressing RPs (RpS2, RpS5a, RpS9, RpS11, RpS13, RpS18, RpL8, RpL11, RpL32, and RpL36) tagged with either green or red fluorescent protein. Imaging of salivary gland cells showed that these proteins are, as expected, abundant in the cytoplasm as well as in the nucleolus. However, these RPs are also apparent in the nucleus in the region occupied by the chromosomes. Indeed, polytene chromosome immunostaining of a representative subset of tagged RPs confirms the association with transcribed loci. Furthermore, characterization of a strain expressing RpL41 functionally tagged at its native genomic locus with YFP, also showed apparent nuclear accumulation and chromosomal association, suggesting that such a nuclear localization pattern might be a shared feature of RPs and is biologically important. We anticipate that the transgenes described here should provide a useful research tool to visualize ribosomal subunits in Drosophila tissues and to study the non-ribosomal functions of RPs.\u

Survival of Massive Star-forming Galaxies in Cluster Cores Drives Gas-Phase Metallicity Gradients : The Effects of Ram Pressure Stripping

Recent observations of galaxies in a cluster at z=0.35 show that their integrated gas-phase metallicities increase with decreasing cluster-centric distance. To test if ram pressure stripping (RPS) is the underlying cause, we use a semi-analytic model to quantify the "observational bias" that RPS introduces into the aperture-based metallicity measurements. We take integral field spectroscopy of local galaxies, remove gas from their outer galactic disks via RPS, and then conduct mock slit observations of cluster galaxies at z=0.35. Our RPS model predicts a typical cluster-scale metallicity gradient of -0.03 dex/Mpc. By removing gas from the outer galactic disks, RPS introduces a mean metallicity enhancement of +0.02 dex at a fixed stellar mass. This gas removal and subsequent quenching of star formation preferentially removes low mass cluster galaxies from the observed star-forming population. As only the more massive star-forming galaxies survive to reach the cluster core, RPS produces a cluster-scale stellar mass gradient of -0.05 log(M_*/M_sun)/Mpc. This mass segregation drives the predicted cluster-scale metallicity gradient of -0.03 dex/Mpc. However, the effects of RPS alone can not explain the higher metallicities measured in cluster galaxies at z=0.35. We hypothesize that additional mechanisms including steep internal metallicity gradients and self-enrichment due to gas strangulation are needed to reproduce our observations at z=0.35.Comment: 17 pages, 21 figures, accepted for publication Ap

An HPSG approach to Welsh unbounded dependencies

Welsh is a language in which unbounded dependency constructions involve both gaps and resumptive pronouns (RPs). Gaps and RPs appear in disjoint sets of environments. Otherwise, however, they are quite similar. This suggests that they involve the same mechanism, and in HPSG that they involve the SLASH feature. It is possible to provide an analysis in which RPs are associated with the SLASH feature but are also the ordinary pronouns which they appear to be

A Federal Renewable Electricity Requirement

Rising energy prices and climate change have changed both the economics and politics of electricity. In response, over half the states have enacted "renewable portfolio standards" (RPS) that require utilities to obtain some power from "renewable" generation resources rather than carbon emitting fossil fuels. Reports of state-level success have brought proposals for a national standard. Like several predecessor Congresses, however, the most recent one failed to pass RPS legislation. Before trying one more time, legislators should ask why they favor a policy so politically correct and so economically suspect. Support for a national program largely stems from misleading claims about state-level successes, misunderstandings about how renewables interact with other environmental regulation, and misinformation about the actual benefits renewables create. State RPS programs are largely in disarray, and even the apparently successful ones have had little impact. California's supposedly aggressive program has left it with the same percentage of renewable power as in 1998, and Texas's seemingly impressive wind turbine investments produce only two percent of its electricity. The public may envision solar collectors but wind accounts for almost all of the growth in renewable power, and it largely survives on favorable tax treatment. Wind's intermittency reduces its efficacy in carbon control because it requires extra conventional generation reserves. Computer-generated predictions about a national RPS are generally unreliable, but they show that with or without one the great majority of generation investments for the next several decades will be fossil-fueled. Even without the technological and environmental shortcomings of renewables, the case for a national RPS is economically flawed. Emissions policies are moving toward efficient market-based trading systems and more rational setting of standards. A national RPS clashes with principles of efficient environmental policy because it is a technological requirement that applies to a single industry. Arguments that a national RPS will create jobs, mitigate energy price risks, improve national security and make the United Sates more competitive internationally are in the main restatements of elementary economic fallacies. It is hard to imagine a program that delivers as little in theory as a national RPS, and the experiences of the states indicate that it delivers equally little in practice

The roles of ram-pressure stripping and minor mergers in evolution of galaxies

We investigate environmental effects on evolution of bright cluster galaxies in a Lambda-dominated cold dark matter universe using a combination of dissipationless N-body simulations and a semi-analytic galaxy formation model. We incorporate effects of ram-pressure stripping (RPS) and minor merger-induced small starburst (minor burst) into our model. By considering minor burst, observed morphology-radius relation is successfully reproduced. When we do not consider minor burst, the RPS hardly increases the intermediate B/T population. In addition, the RPS and minor burst are not important for colours or star formation rates of galaxies in the cluster core if star formation time-scale is properly chosen, because the star formation is sufficiently suppressed by consumption of the cold gas. We also find that SF in bulge-dominated galaxies is mainly terminated by starburst induced by major mergers in all environments.Comment: To appear in the proceedings of IAU colloq. No. 195, "Outskirts of Galaxy Clusters: intense life in the suburbs", Torino, 12-16 March 2004, 5 pages, 2 figures, uses IAU macr