ANALYSIS AND PREDICTION OF WATER TREATMENT COSTS AT THE DV HARRIS PLANT IN THE UMGENI CATCHMENT AREA.

This paper has two objectives: first, to identify the main contaminants responsible for high treatment costs in the Umgeni catchment area, and second, to predict treatment costs from observed levels of contaminants. A partial adjustment model of treatment costs is estimated for the DV Harris plant, which draws water from Midmar Dam, using ordinary least squares regression and principal component analysis. The model highlights important policy issues and explains 61% of the variation in chemical treatment costs. Environmental contaminants have a marked impact on treatment costs. Treatment costs increase when levels of alkalinity, sodium and turbidity fall. Conversely, costs rise with higher levels of dissolved oxygen and water stability. Paradoxically, clean water - typical of Midmar Dam - is expensive to treat. Treatment costs also rise when concentrations of the algae, Chlorella, decline. Apparently the level of Chlorella varies inversely with the level of other, more harmful, contaminants.Resource /Energy Economics and Policy,

Fluctuation-stabilized marginal networks and anomalous entropic elasticity

We study the elastic properties of thermal networks of Hookean springs. In the purely mechanical limit, such systems are known to have vanishing rigidity when their connectivity falls below a critical, isostatic value. In this work we show that thermal networks exhibit a non-zero shear modulus $G$ well below the isostatic point, and that this modulus exhibits an anomalous, sublinear dependence on temperature $T$. At the isostatic point, $G$ increases as the square-root of $T$, while we find $G \propto T^{\alpha}$ below the isostatic point, where ${\alpha} \simeq 0.8$. We show that this anomalous $T$ dependence is entropic in origin.Comment: 9 pages, 7 figure

Microwave ISM Emission Observed by WMAP

We investigate the nature of the diffuse Galactic emission in the Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial dust-correlated emission is observed at all WMAP frequencies, far exceeding the expected thermal dust emission in the lowest frequency channels (23, 33, 41 GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated synchrotron radiation, attributing the correlation to the natural association of relativistic electrons produced by SNae with massive star formation in dusty clouds, and deriving an upper limit of 5% on the contribution of Draine & Lazarian spinning dust at K-band (23 GHz). We pursue an alternative interpretation that much, perhaps most, of the dust-correlated emission at these frequencies is indeed spinning dust, and explore the spectral dependence on environment by considering a few specific objects as well as the full sky average. Models similar to Draine & Lazarian spinning dust provide a good fit to the full-sky data. The full-sky fit also requires a significant component with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K) gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and added references. 23 pages, 5 figures, 2 tables. Free-free haze map is available at http://skymaps.inf

Critical behaviour in the nonlinear elastic response of hydrogels

In this paper we study the elastic response of synthetic hydrogels to an applied shear stress. The hydrogels studied here have previously been shown to mimic the behaviour of biopolymer networks when they are sufficiently far above the gel point. We show that near the gel point they exhibit an elastic response that is consistent with the predicted critical behaviour of networks near or below the isostatic point of marginal stability. This point separates rigid and floppy states, distinguished by the presence or absence of finite linear elastic moduli. Recent theoretical work has also focused on the response of such networks to finite or large deformations, both near and below the isostatic point. Despite this interest, experimental evidence for the existence of criticality in such networks has been lacking. Using computer simulations, we identify critical signatures in the mechanical response of sub-isostatic networks as a function of applied shear stress. We also present experimental evidence consistent with these predictions. Furthermore, our results show the existence of two distinct critical regimes, one of which arises from the nonlinear stretch response of semi-flexible polymers.

Microwave ISM Emission in the Green Bank Galactic Plane Survey: Evidence for Spinning Dust

We observe significant dust-correlated emission outside of H II regions in the Green Bank Galactic Plane Survey (-4 < b < 4 degrees) at 8.35 and 14.35 GHz. The rising spectral slope rules out synchrotron and free-free emission as majority constituents at 14 GHz, and the amplitude is at least 500 times higher than expected thermal dust emission. When combined with the Rhodes (2.326 GHz), and WMAP (23-94 GHz) data it is possible to fit dust-correlated emission at 2.3-94 GHz with only soft synchrotron, free-free, thermal dust, and an additional dust-correlated component similar to Draine & Lazarian spinning dust. The rising component generally dominates free-free and synchrotron for \nu >~ 14 GHz and is overwhelmed by thermal dust at \nu > 60 GHz. The current data fulfill most of the criteria laid out by Finkbeiner et al. (2002) for detection of spinning dust.Comment: ApJ in press. 26 pages, 11 figures, figures jpeg compressed to save spac

Methods to Determine Total Electron-Induced Electron Yields Over Broad Range ofConductive and Nonconductive Materials

The electron emission properties of a material subject to incident radiation flux are key parameters in determining to what equilibrium charge a spacecraft will established under given environmental conditions. However, there is a complex relation between these emission properties and the charge built up in spacecraft insulators. Complex modeling codes have been developed to predict the potential a spacecraft will adopt as a consequence of its interaction with the space plasma. These require correct models of the electron yields as a function of charge to accurately predict the both the charge build up and the equilibrium potential of spacecraft components. This paper focuses on different methods appropriate to determine the fundamental electronic material property of total electron yield as the materials accumulates charge. Three methods for determining the uncharged total yield are presented: (i) The DC Continuous Beam Method is a relatively easy and accurate method appropriate for conductors and semi- conductors with maximum total electron yield σmaxρ\u3c106 \u3eΩ-cm. (ii) The Pulse-Yield Method seeks to minimize the effects of charging and is applicable to materials with σmaxρ up to \u3e1024 Ω-cm. (iii) The Yield Decay Method is a very difficult and time consuming that uses a combination of measurement and modeling to measure the most difficult materials with σmax\u3e4 and ρ up to \u3e1024 Ω-cm. Data for high purity polycrystalline Au, Kapton HN, and polycrystalline aluminum oxide ceramic are presented. These data demonstrate the relative strengths and weaknesses of each method, but more importantly show that the methods described herein are capable of reliably measuring the total electron yield of almost any spacecraft material

When the Bloom is on the Cotton Dixie Lee

VERSE 1Round my southern home the cotton fields are blooming,Far away the river glistens ‘neath the moon;Through the twilight comes the breath of clover blossoms,Far away the darkies sing a southern tune.Side by side down by the flowing stream we wandered,On your face the moonlight cast a golden glow;And I kissed away the tears when you were cryingAs I said “Goodbye” and whispered soft and low. REFRAINWhen the bloom is on the cotton, Dixie Lee,Life’s sun will shine again for you and me;I’ll return to you once more, we’ll be happy as of yoreWhen the bloom is on the cotton, Dixie Lee. VERSE 2In my dreams tonight I’m roaming with you Dixie,While the cotton fields are all abloom once more;I can see the soft moonlight upon the river,And your sweet face as you stroll along the shore.But we nevermore will wander down the pathway,As we did the night you gave your heart to me,For the tolling bells they tell the sad, and storyWhile the breezes whisper “Farewell” Dixie Lee. REFRAI