The activated sludge process—IV: Application of the general kinetic model to anoxic-aerobic digestion of waste activated sludge

This paper discusses the application of the general activated sludge model as set out by Dold et al. (Prog. Wat. Technol.12, 47–77, 1980) and extended by Van Haandel et al. (Wat. Res.15, 1135–1152, 1981), to anoxic-aerobic digestion of waste activated sludge. The laboratory scale experimental investigation comprised a 6 day sludge age activated sludge process, the waste sludge from which was fed to a number of digesters operated as follows: single reactor flow-through digesters at 4 or 10 days sludge age (retention times) under aerobic or anoxic-aerobic conditions (with 1.5 and 4 h cycle times) and 3-in-series flow-through aerobic digesters each with 4 days sludge age; all digesters were fed draw-and-fill wise once per day. The general kinetic model simulated accurately all the experimental data without the need to change the values of the kinetic constants. Both theoretical simulations and experimental data indicate that (i) the rate of volatile solids destruction is not affected by the incorporation of anoxic cycles and (ii) the specific denitrification rate constant in a digester is about two-thirds of that in the secondary anoxic reactor of the single sludge activated sludge system; this allows definition of a fourth denitrification rate constant K₄ for the anoxic-aerobic digester with K₄T = 0.046(1.029)^(T-20) mg(NO₃-N) (mgAVSS d)⁻¹, a constant independent of sludge age. An important consequence of (i) and (ii) above is that the denitrification can be integrated readily into the steady state digester model of Marais and Ekama (Wat. SA2, 163–200, 1976) and used for design purposes.     

Endothelin 1 mediates ex vivo coronary vasoconstriction caused by exogenous and endogenous cytokines

Treatment of rats with cytokines has been associated with an increase in the circulating levels of endothelin 1 (ET-1). Here we show that administration of tumor necrosis factor alpha (TNF-alpha; 4 micrograms.kg-1) to anesthetized rats caused within 15 min a strong elevation in the circulating levels of ET-1. This was associated with a striking coronary vasoconstriction in hearts from these animals when they were removed and perfused in vitro by the Langendorff technique. This vasoconstriction was largely overcome by treatment with either the endothelin type A (ETA) receptor antagonist FR 139317 or antibody against ET-1. Furthermore, it was mimicked by in vivo exposure to exogenous ET-1. Endogenously produced TNF-alpha may also cause such a coronary vasoconstriction, for treatment with interleukin 2 (600 micrograms.kg-1) produced an increase in coronary perfusion pressure that correlated with the increases in circulating TNF-alpha. This coronary vasoconstriction was substantially reversed by treatment either with antibody against TNF-alpha or with FR 139317. We suggest, therefore, that cytokine-driven changes in the production of ET-1 are key events in the development of vascular pathologies.     

The use of structural equation modeling in assessing the quality of marital observations.

The authors examine traditional analytic approaches to assessing the quality of observational measures and suggest a structural equation modeling (SEM) approach that extends the multitrait-multimethod tradition to assess both reliability and validity of observational data. Drawing on observations of hostility and coercion in marital interactions obtained with the Iowa Family Interaction Rating Scales (J. Melby et al., 1990), the authors illustrate the use of SEM as a means to evaluate estimates of psychometric properties of both observational ratings and family member reports within the same analytic framework, thereby providing more comparable assessments across study informants. The results demonstrate the utility of this approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nuclear waste management: shifting the paradigm

In planning the management of nuclear waste, the U.S. has emphasized performance assessments and compliance with regulations, and has under-utilized processes for facilitating public understanding and public acceptance. A paradigm shift is needed. Motivation for this viewpoint comes from the author's five years of service on the Nuclear Waste Technical Review Board (NWTRB) and from his experience in assessing risks associated with the Department of Energy (DOE) nuclear weapons complex.     

Malignant oncocytoma of the lacrimal sac: ultrastructure and immunocytochemistry

Malignant oncocytoma of the lacrimal sac is a rare tumor. A third example is presented here. In addition to oncocytes, tumor acini also harbored a few mucin cells and myoepithelial cells. The presence of immunoreactive lactoferrin and secretory piece suggested a resemblance to parotid acinic cell carcinomas. The difference was marked by a compact acinar structure and myoepithelial cell differentiation in the oncocytoma.     

Facilitating condom use with clients during commercial sex in Nevada's legal brothels

OBJECTIVES: This study examined condom use in legal Nevada brothels. METHODS: Forty female prostitutes in two brothels were interviewed about client resistance to condoms and techniques for facilitating condom use. RESULTS: Of 3290 clients in the previous month, 2.7% (95% confidence interval [CI] = 2.2%,3.4%) were reluctant to use condoms. Of these individuals, 72% ultimately used condoms, while 12% chose nonpenetrative sex without condoms. The remaining 16% left the brothels without services. Condom use rates were markedly lower with nonpaying sex partners (lowers) than with clients. CONCLUSIONS: Brothel prostitutes may be at greater risk for acquiring HIV and other sexually transmitted diseases from lovers than from clients.