No abstract

The place of lenticular galaxies within the range of types of galaxies remains unclear. We previously reported the mass of molecular hydrogen for a volume-limited sample of lenticular galaxies, where we saw that the amount of gas was less than that predicted by the return of stellar mass to the interstellar medium. Here we report observations of atomic hydrogen (H i) for the same sample. Detections in several galaxies make more compelling the case presented in our earlier paper that the mass of cool gas in S0 galaxies cuts off at $10% of what is expected from current models of gas return from stellar evolution. The molecular and atomic phases of the gas in our sample galaxies appear to be separate and distinct, both spatially and in velocity space. We propose that the molecular gas arises mostly from the stellar mass returned to the galaxy, while the atomic hydrogen is mainly accumulated from external sources (infall, captured dwarfs, etc.). While this proposal fits most of the observations, it makes the presence of the upper mass cutoff even more mysterious.

No abstract

We present preliminary results from a survey of CO emission from members of a volume-limited sample of non-cluster elliptical galaxies. Our intent is to compare the gas properties of these ellipticals to a sample of lenticulars selected using similar criteria. The data, although still sparse, suggest that the cool gas in ellipticals shows the same puzzling upper mass cutoff found in the lenticular galaxies. We find, however, significantly lower detection rates and possibly much lower H2/HI mass ratios in the ellipticals. The detection rate is higher among the lower-mass galaxies, as has been found previously. This seems puzzling given that the deeper potential wells of the larger galaxies ought to make gas retention easier, but perhaps that effect is overwhelmed by feedback from the central suppermassive black hole. As we have observed ~40 percent of our sample, the conclusions are necessarily tentative at this time.Comment: Accepted for publication in the Astrophysical Journa

The pretreatment of cellulose in corn fiber by liquid hot water at 160 degrees C and a pH above 4.0 dissolved 50% of the fiber in 20 min. The pretreatment also enabled the subsequent complete enzymatic hydrolysis of the remaining polysaccharides to monosaccharides. The carbohydrates dissolved by the pretreatment were 80% soluble oligosaccharides and 20% monosaccharides with <1% of the carbohydrates lost to degradation products. Only a minimal amount of protein was dissolved, thus enriching the protein content of the undissolved material. Replication of laboratory results in an industrial trial at 43 gallons per minute (163 L/min) of fiber slurry with a residence time of 20 min illustrates the utility and practicality of this approach for pretreating corn fiber. The added costs owing to pretreatment, fiber, and hydrolysis are equivalent to less than 0.84 dollars/gal of ethanol produced from the fiber. Minimizing monosaccharide formation during pretreatment minimized the formation of degradation products; hence, the resulting sugars were readily fermentable to ethanol by the recombinant hexose and by pentose-fermenting Saccharomyces cerevisiae 424A(LNH-ST) and ethanologenic Escherichia coli at yields >90% of theoretical based on the starting fiber. This cooperative effort and first successful trial opens the door for examining the robustness of the pretreatment system under extended run conditions as well as pretreatment of other cellulose-containing materials using water at controlled pH.