The Cool ISM in Elliptical Galaxies. II. Gas Content in the Volume - Limited Sample and Results from the Combined Elliptical and Lenticular Surveys

We report new observations of atomic and molecular gas in a volume limited sample of elliptical galaxies. Combining the elliptical sample with an earlier and similar lenticular one, we show that cool gas detection rates are very similar among low luminosity E and SO galaxies but are much higher among luminous S0s. Using the combined sample we revisit the correlation between cool gas mass and blue luminosity which emerged from our lenticular survey, finding strong support for previous claims that the molecular gas in ellipticals and lenticulars has different origins. Unexpectedly, however, and contrary to earlier claims, the same is not true for atomic gas. We speculate that both the AGN feedback and merger paradigms might offer explanations for differences in detection rates, and might also point towards an understanding of why the two gas phases could follow different evolutionary paths in Es and S0s. Finally we present a new and puzzling discovery concerning the global mix of atomic and molecular gas in early type galaxies. Atomic gas comprises a greater fraction of the cool ISM in more gas rich galaxies, a trend which can be plausibly explained. The puzzle is that galaxies tend to cluster around molecular-to-atomic gas mass ratios near either 0.05 or 0.5.Comment: 37 pages, including 4 tables and 12 figures. Accepted for publication in the Astrophysical Journa

Basic Performance Evaluation of a Radiation Survey Meter That Uses a Plastic-Scintillation Sensor

After the Fukushima nuclear power plant accident in 2011, many types of survey meters were used, including Geiger–Müller (GM) survey meters, which have long been used to measure β-rays. Recently, however, a novel radiation survey meter that uses a plastic-scintillation sensor has been developed. Although manufacturers’ catalog data are available for these survey meters, there have been no user reports on performance. In addition, the performance of commercial plastic-scintillation survey meters has not been evaluated. In this study, we experimentally compared the performance of a plastic-scintillation survey meter with that of a GM survey meter. The results show that the two instruments performed very similarly in most respects. The GM survey meter exhibited count losses when the radiation count rate was high, whereas the plastic-scintillation survey meter remained accurate under such circumstances, with almost no count loss at high radiation rates. For measurements at background rates (i.e., low counting rates), the counting rates of the plastic-scintillation and GM survey meters were similar. Therefore, an advantage of plastic-scintillation survey meters is that they are less affected by count loss than GM survey meters. We conclude that the plastic-scintillation survey meter is a useful β-ray measuring/monitoring instrument

A structural and dynamic investigation of the inhibition of catalase by nitric oxide.

Determining the chemical and structural modifications occurring within a protein during fundamental processes such as ligand or substrate binding is essential to building up a complete picture of biological function. Currently, significant unanswered questions relate to the way in which protein structural dynamics fit within the structure-function relationship and to the functional role, if any, of bound water molecules in the active site. Addressing these questions requires a multidisciplinary approach and complementary experimental techniques that, in combination, enhance our understanding of the complexities of protein chemistry. We exemplify this philosophy by applying both physical and biological approaches to investigate the active site chemistry that contributes to the inhibition of the Corynebacterium glutamicum catalase enzyme by nitric oxide. Ultrafast two-dimensional infrared spectroscopy (2D-IR) experiments exploit the NO ligand as a local probe of the active site molecular environment and shows that catalase displays a dynamically-restricted, 'tight,' structure. X-ray crystallography studies of C. glutamicum catalase confirm the presence of a conserved chain of hydrogen-bonded bound water molecules that link the NO ligand and the protein scaffold. This combination of bound water and restricted dynamics stands in stark contrast to other haem proteins, such as myoglobin, that exhibit ligand transport functionality despite the presence of a similar distal architecture in close proximity to the ligand. We conclude not only that the bound water molecules in the catalase active site play an important role in molecular recognition of NO but also may be part of the mechanistic operation of this important enzyme