Georgia Water: "A Public Resource Or A Commodity" What Are The Real Policy Questions?

In this paper we first address the question as to the strength of Georgia's commitment to protect public interests in the state's water resources as such commitments are expressed in existing laws. Comparing legislative declarations of state policy in Georgia with those in 36 other Eastern States, we find that none of the states have expressions of this commitment that would reasonably be regarded as more strongly stated than Georgia law. In conclusion, we find that Georgia water law currently recognizes the public's dependence on the state's water resources and its commitment to policies and programs that assure that water is used prudently for the maximum benefit of the people. Adding "public resource" language to the law would not substantively strengthen these existing policy declarations.Attention is then turned to the "water as a commodity" issue. We argue here that the "water as a commodity" issues is at best poorly framed. In our view debate in Georgia should center on alternatives for resolving the reallocation issue; it should focus on the question as to how Georgia is to strike a balance between private, competing use of water and public, non-competing uses of water (e.g., instream flows), and how this balance is to be adjusted over time in response to changes in social, environmental, and climatic conditions. When market mechanisms are considered as one of the means to achieve reallocation, evaluation of their effectiveness is dependent on a particular set of market institutions. Thus, being "for" or "against" markets makes no more sense that being "for" or "against" water use permits -- everything depends on the provisions and protections of specific laws and proposals. Working Paper # 2002-00

Conservation Pricing Of Household Water Use In Public Water Systems In Georgia's Coastal Communities: A Preliminary Exploration

The purpose of this study is to explore the effect of price on residential water use in public water supply systems in Georgia's Coastal region. Particular attention is focused on measures for the elasticity of demand for residential water use inasmuch as a showing of price inelasticity may make the wider adoption of conservation pricing more palatable to small communities with concerns that raising water prices will reduce much-needed revenues.To clarify the nature and importance of the elasticity measure, consider the following simplified example. A community sells 100 units of water for $1.00 per unit. Its' total revenues are$100. Suppose price is increased by 20% to $1.20, and that the units purchased falls by 30$84.00. In this case, we say that demand is "elastic;" the quantity of water used by folks "stretches" relative to the change in price. With elastic demand, rising prices mean lower total revenues. Suppose, however, that with the 20% price increase, demand fell to only 90 units -- a 10% decrease. Total revenues are now $108. In this case we say demand is inelastic -- quantity doesn't really "stretch" much when prices rise. If demand is inelastic, rising prices means higher revenues.From our limited, phase one efforts in these regards, we use aggregate water pricing data from 50 public water supply systems in 28 coastal counties that participated in a survey conducted during late the period 2003-2005. We find strong evidence that, at the margin, residential water use is indeed affected by prices charged for water in this region. We also find what we regard to be reasonably compelling evidence suggesting that residential water demand is inelastic over the range of marginal prices observed in our sample. This latter finding suggests that the use of conservation pricing as a tool for water conservation may not have an adverse effect on community revenues. Indeed, it may well be the case that increasing water prices will increase, not decrease, the community's revenues from the sale of water.In moving to phase two of this work, a great more will be accomplished in terms of refinements in the nature and quality of data used; greater efforts will be placed on attempts to identify functional forms that will yield best estimates for residential water demand in the state. Our ultimate goal is to be capable of responding to the needs of Georgia communities in the coastal region for information related to how one might improve the design of a community's water rate structure, and to conservation pricing policies that will best serve their interests and the interests of the state. Working Paper Number 2005-00

A theoretical treatment of void electromigration in the strip geometry

The void electromigration process in the strip geometry is investigated analytically and numerically. The void is assumed to travel either along the axis of symmetry of the metal strip or at the boundary. In each case, the shape, the velocity of the void and the characteristic electrical current are predicte

Models of void electromigration

We study the motion of voids in conductors subject to intense electrical current densities. We use a free-boundary model in which the flow of current around the insulating void is coupled to a law of motion (kinematic condition) for the void boundary. In the first part of the paper, we apply a new complex variable formulation of the model to an infinite domain and use this to (i) consider the stability of circular and flat front travelling waves, (ii) show that, in the unbounded metal domain, the only travelling waves of finite void area are circular, and (iii) consider possible static solutions. In the second part of the paper, we look at a conducting strip (which can be used to model interconnects in electronic devices) and use asymptotic methods to investigate the motion of long wavelength voids on the conductor boundary. In this case we derive a nonlinear parabolic PDE describing the evolution of the free boundary and, using this simpler model, are able to make some predictions about the evolution of the void over long times.<br/

A moving boundary model motivated by electric breakdown: II. Initial value problem

An interfacial approximation of the streamer stage in the evolution of sparks and lightning can be formulated as a Laplacian growth model regularized by a 'kinetic undercooling' boundary condition. Using this model we study both the linearized and the full nonlinear evolution of small perturbations of a uniformly translating circle. Within the linear approximation analytical and numerical results show that perturbations are advected to the back of the circle, where they decay. An initially analytic interface stays analytic for all finite times, but singularities from outside the physical region approach the interface for $t\to\infty$, which results in some anomalous relaxation at the back of the circle. For the nonlinear evolution numerical results indicate that the circle is the asymptotic attractor for small perturbations, but larger perturbations may lead to branching. We also present results for more general initial shapes, which demonstrate that regularization by kinetic undercooling cannot guarantee smooth interfaces globally in time.Comment: 44 pages, 18 figures, paper submitted to Physica

Dissolution in a field

We study the dissolution of a solid by continuous injection of reactive ``acid'' particles at a single point, with the reactive particles undergoing biased diffusion in the dissolved region. When acid encounters the substrate material, both an acid particle and a unit of the material disappear. We find that the lengths of the dissolved cavity parallel and perpendicular to the bias grow as t^{2/(d+1)} and t^{1/(d+1)}, respectively, in d-dimensions, while the number of reactive particles within the cavity grows as t^{2/(d+1)}. We also obtain the exact density profile of the reactive particles and the relation between this profile and the motion of the dissolution boundary. The extension to variable acid strength is also discussed.Comment: 6 pages, 6 figures, 2-column format, for submission to PR

Self-similarity in Laplacian Growth

We consider Laplacian Growth of self-similar domains in different geometries. Self-similarity determines the analytic structure of the Schwarz function of the moving boundary. The knowledge of this analytic structure allows us to derive the integral equation for the conformal map. It is shown that solutions to the integral equation obey also a second order differential equation which is the one dimensional Schroedinger equation with the sinh inverse square potential. The solutions, which are expressed through the Gauss hypergeometric function, characterize the geometry of self-similar patterns in a wedge. We also find the potential for the Coulomb gas representation of the self-similar Laplacian growth in a wedge and calculate the corresponding free energy.Comment: 16 pages, 9 figure

A moving boundary problem motivated by electric breakdown: I. Spectrum of linear perturbations

An interfacial approximation of the streamer stage in the evolution of sparks and lightning can be written as a Laplacian growth model regularized by a `kinetic undercooling' boundary condition. We study the linear stability of uniformly translating circles that solve the problem in two dimensions. In a space of smooth perturbations of the circular shape, the stability operator is found to have a pure point spectrum. Except for the zero eigenvalue for infinitesimal translations, all eigenvalues are shown to have negative real part. Therefore perturbations decay exponentially in time. We calculate the spectrum through a combination of asymptotic and series evaluation. In the limit of vanishing regularization parameter, all eigenvalues are found to approach zero in a singular fashion, and this asymptotic behavior is worked out in detail. A consideration of the eigenfunctions indicates that a strong intermediate growth may occur for generic initial perturbations. Both the linear and the nonlinear initial value problem are considered in a second paper.Comment: 37 pages, 6 figures, revised for Physica

Prebiotic effects: metabolic and health benefits

The different compartments of the gastrointestinal tract are inhabited by populations of micro-organisms. By far the most important predominant populations are in the colon where a true symbiosis with the host exists that is a key for well-being and health. For such a microbiota, 'normobiosis' characterises a composition of the gut 'ecosystem' in which micro-organisms with potential health benefits predominate in number over potentially harmful ones, in contrast to 'dysbiosis', in which one or a few potentially harmful micro-organisms are dominant, thus creating a disease-prone situation. The present document has been written by a group of both academic and industry experts (in the ILSI Europe Prebiotic Expert Group and Prebiotic Task Force, respectively). It does not aim to propose a new definition of a prebiotic nor to identify which food products are classified as prebiotic but rather to validate and expand the original idea of the prebiotic concept (that can be translated in 'prebiotic effects'), defined as: 'The selective stimulation of growth and/or activity(ies) of one or a limited number of microbial genus(era)/species in the gut microbiota that confer(s) health benefits to the host.' Thanks to the methodological and fundamental research of microbiologists, immense progress has very recently been made in our understanding of the gut microbiota. A large number of human intervention studies have been performed that have demonstrated that dietary consumption of certain food products can result in statistically significant changes in the composition of the gut microbiota in line with the prebiotic concept. Thus the prebiotic effect is now a well-established scientific fact. The more data are accumulating, the more it will be recognised that such changes in the microbiota's composition, especially increase in bifidobacteria, can be regarded as a marker of intestinal health. The review is divided in chapters that cover the major areas of nutrition research where a prebiotic effect has tentatively been investigated for potential health benefits. The prebiotic effect has been shown to associate with modulation of biomarkers and activity(ies) of the immune system. Confirming the studies in adults, it has been demonstrated that, in infant nutrition, the prebiotic effect includes a significant change of gut microbiota composition, especially an increase of faecal concentrations of bifidobacteria. This concomitantly improves stool quality (pH, SCFA, frequency and consistency), reduces the risk of gastroenteritis and infections, improves general well-being and reduces the incidence of allergic symptoms such as atopic eczema. Changes in the gut microbiota composition are classically considered as one of the many factors involved in the pathogenesis of either inflammatory bowel disease or irritable bowel syndrome. The use of particular food products with a prebiotic effect has thus been tested in clinical trials with the objective to improve the clinical activity and well-being of patients with such disorders. Promising beneficial effects have been demonstrated in some preliminary studies, including changes in gut microbiota composition (especially increase in bifidobacteria concentration). Often associated with toxic load and/or miscellaneous risk factors, colon cancer is another pathology for which a possible role of gut microbiota composition has been hypothesised. Numerous experimental studies have reported reduction in incidence of tumours and cancers after feeding specific food products with a prebiotic effect. Some of these studies (including one human trial) have also reported that, in such conditions, gut microbiota composition was modified (especially due to increased concentration of bifidobacteria). Dietary intake of particular food products with a prebiotic effect has been shown, especially in adolescents, but also tentatively in postmenopausal women, to increase Ca absorption as well as bone Ca accretion and bone mineral density. Recent data, both from experimental models and from human studies, support the beneficial effects of particular food products with prebiotic properties on energy homaeostasis, satiety regulation and body weight gain. Together, with data in obese animals and patients, these studies support the hypothesis that gut microbiota composition (especially the number of bifidobacteria) may contribute to modulate metabolic processes associated with syndrome X, especially obesity and diabetes type 2. It is plausible, even though not exclusive, that these effects are linked to the microbiota-induced changes and it is feasible to conclude that their mechanisms fit into the prebiotic effect. However, the role of such changes in these health benefits remains to be definitively proven. As a result of the research activity that followed the publication of the prebiotic concept 15 years ago, it has become clear that products that cause a selective modification in the gut microbiota's composition and/or activity(ies) and thus strengthens normobiosis could either induce beneficial physiological effects in the colon and also in extra-intestinal compartments or contribute towards reducing the risk of dysbiosis and associated intestinal and systemic pathologies