Nitrogen removal and ammonia-oxidising bacteria in a vertical flow constructed wetland treating inorganic wastewater

Nitrogen removal performance and the ammonia-oxidising bacterial (AOB) community were assessed in the batch loaded 1.3ha saturated surface vertical flow wetland at CSBP Ltd, a fertiliser and chemical manufacturer located in Kwinana, Western Australia. From September 2008 to October 2009 water quality was monitored and sediment samples collected for bacterial analyses. During the period of study the wetland received an average inflow of 1109m3/day with NH3-N = 40mg/L and NO3-N=23mg/L. Effluent NH3-N and NO3-N were on average 31mg/L and 25mg/L respectively. The overall NH3-N removal rate for the period was 1.2g/m2/d indicating the nitrifying capacity of the wetland. The structure of the AOB community was analysed using group specific primers for the ammonia monooxygenase gene (amoA) by terminal restriction fragment length polymorphism (T-RFLP) and by clone libraries to identify key members. The majority of sequences obtained were most similar to Nitrosomonas sp. while Nitrosospira sp. was less frequent. Another two vertical flow wetlands, 0.8ha each, were commissioned at CSBP in July 2009, since then the wetland in this study has received nitrified effluent from these two new cells

Framing Effects on Bidding Behavior in Experimental First-Price Sealed-Bid Money Auctions

Consumers often face prices that are the sum of two components, for example, an online purchase that includes a stated price and shipping costs. In such cases consumer behavior may be influenced by framing, i.e., how the components are bifurcated. Previous studies have demonstrated the effects of framing and anchoring in auctions. This study examines bidding patterns in a series of first-price sealed-bid experimental money auctions (where the commodity being auctioned is money itself). We hypothesize that bidders’ behavior is affected by the framing of the potential monetary payoff into “monetary prize” and “winner’s bonus” components. We find strong evidence of an anchoring effect that influences the strategic behavior of bidders

Exploring the Link Between Self-Construal and Distress Among African American and Asian American College Students

The authors investigated ethnicity, self-construal, and distress among African American and Asian American college students. African American students expressed more salient independent self-construals, whereas Asian American students expressed more salient interdependent self-construals. As hypothesized, among African American participants, distress was positively related to interdependent self-construal and negatively associated with independent self-construal. Contrary to prediction, the same pattern was found for Asian American participants. Multicultural clinical practice implications are presented

The Evolutionary Status of Isolated Dwarf Irregular Galaxies II. Star Formation Histories and Gas Depletion

The results of UBV and H alpha imaging of a large sample of isolated dwarf irregular galaxies are interpreted in the context of composite stellar population models. The observed optical colors are best fit by composite stellar populations which have had approximately constant star formation rates for at least 10 Gyr. The galaxies span a range of central surface brightness, from 20.5 to 25.0 mag arcsec^{-2}; there is no correlation between surface brightness and star formation history. Although the current star formation rates are low, it is possible to reproduce the observed luminosities without a major starburst episode. The derived gas depletion timescales are long, typically ~20 Gyr. These results indicate that dwarf irregular galaxies will be able to continue with their slow, but constant, star formation activity for at least another Hubble time. The sample of isolated dIs is compared to a sample of star bursting dwarf galaxies taken from the literature. The star bursting dwarf galaxies have many similar properties; the main difference between these two types of gas-rich dwarf galaxies is that the current star formation is concentrated in the center of the star bursting systems while it is much more distributed in the quiescent dIs. This results in pronounced color gradients for the starbursting dwarf galaxies, while the majority of the quiescent dwarf irregular galaxies have minor or non-existent color gradients. Thus, the combination of low current star formation rates, blue colors, and the lack of significant color gradients indicates that star formation percolates slowly across the disk of normal dwarf galaxies in a quasi-continuous manner.Comment: 16 pages, uses emulateapj, to appear in The Astronomical Journal (April 2001

Oxygen and Nitrogen in Leo A and GR 8

We present elemental abundances for multiple HII regions in Leo A and GR 8 obtained from long slit optical spectroscopy of these two nearby low luminosity dwarf irregular galaxies. As expected from their luminosities, and in agreement with previous observations, the derived oxygen abundances are extremely low in both galaxies. High signal-to-noise ratio observations of a planetary nebula in Leo A yield 12 + log(O/H) = 7.30 +/- 0.05; "semi-empirical" calculations of the oxygen abundance in four HII regions in Leo A indicate 12 + log(O/H) = 7.38 +/- 0.10. These results confirm that Leo A has one of the lowest ISM metal abundances of known nearby galaxies. Based on results from two HII regions with high signal-to-noise measurements of the weak [O III] 4363 line, the mean oxygen abundance of GR 8 is 12 + log(O/H) = 7.65 +/- 0.06; using "empirical" and "semi-empirical" methods, similar abundances are derived for 6 other GR 8 HII regions. Similar to previous results in other low metallicity galaxies, the mean log(N/O) = -1.53 +/- 0.09 for Leo A and -1.51 +/- 0.07 for GR 8. There is no evidence of significant variations in either O/H or N/O in the HII regions. The metallicity-luminosity relation for nearby (D < 5 Mpc) dwarf irregular galaxies with measured oxygen abundances has a mean correlation of 12 + log(O/H) = 5.67 - 0.151 M_B with a dispersion in oxygen about the relationship of 0.21. These observations confirm that gas-rich low luminosity galaxies have extremely low elemental abundances in the ionized gas-phase of their interstellar media. Although Leo A has one of the lowest metal abundances of known nearby galaxies, detection of tracers of an older stellar population indicate that it is not a newly formed galaxy as has been proposed for some other similarly low metallicity star forming galaxies.Comment: 36 pages, 7 figures. Accepted to Ap