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Water Networks (water + network)
Selected AbstractsA Multicriteria Decision Support Methodology for Annual Rehabilitation Programs of Water NetworksCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 7 2007Pascal Le Gauffre A first set of criteria is formulated for the purpose of comparing and ranking rehabilitation projects. Each proposed criterion is a measure of a particular impact of the condition of a pipe. The ELECTRE TRI method is implemented for defining rehabilitation priorities. Two reference profiles are used to define the limits of three categories associated with three increasing priority levels. With these two reference profiles, applying the ELECTRE TRI method to an asset stock (a set of pipes that are candidates for rehabilitation) means assigning each pipe to one of six possible priority groups. A second set of criteria, based on the concept of efficiency, is proposed for comparing alternative rehabilitation programs (subsets of the asset stock). [source] The Trickle-down Effect: Ideology and the Development of Premium Water Networks in China's CitiesINTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 1 2007ALANA BOLAND This article examines the relationship between networked infrastructure and uneven development in transitional cities through a study of premium water networks in China. Beginning in the mid-1990s, select buildings and housing enclaves began to bypass municipal tap water supply systems through the construction of small-scale secondary pipe networks for purified drinking water. I focus on the early development of these premium water networks to highlight the ideological interplay between a new more market-based approach to networked supply and the existing model characterized by relatively universal and uniform access within cities. I illustrate how this dual water supply model was well suited to the ideological conditions and contradictions associated with China's economic liberalization in the 1990s. While the emergence of premium water networks can be linked to ascendant forms of market reasoning in the environmental and social spheres, I also argue that they were enabled by unresolved ideological tensions associated with China's transitional program. Rather than providing a basis for resistance in the early development of premium water supply, the socialist legacy in urban water supply left its mark more in the noticeable absence of debate regarding the distributional outcomes. By examining premium water networks in relation to the politics of ideology in China's transitional period, my analysis highlights the complex and sometimes unexpected ways that ideologies can influence the development of new infrastructural spaces and processes of splintering urbanism. [source] Optimal design of single-contaminant regeneration reuse water networks with process decompositionAICHE JOURNAL, Issue 4 2010Jie Bai Abstract Water network with regeneration schemes (e.g., regeneration reuse, regeneration recycling) can reduce freshwater consumption further than water network merely with direct reuse. Regeneration reuse, compared with regeneration recycling, can additionally avoid unexpected accumulation of contaminants. Owing to these features, process decomposition can help to reduce freshwater usage and wastewater discharge of regeneration reuse water systems and achieve the results, which graphical method delivers. In this article, the effect of decomposition on water-using process and further on regeneration reuse water system is briefly analyzed on the concentration-mass load diagram. Then a superstructure and three sequential mathematical models, which take process decomposition into account, are in turn developed to optimize single contaminant regeneration reuse water systems. By several examples, the reliability of the models is verified. Moreover, several decomposition strategies are summarized to realize the regeneration reuse water network, which attains the targets from graphical method. The results indicate that postregeneration concentration has a major impact on the scheme of process decomposition. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Stability and Dynamics of Domain-Swapped Bovine-Seminal RibonucleaseCHEMISTRY & BIODIVERSITY, Issue 5 2004Kalyan The proteins of the ribonuclease-A (RNase-A) family are monomeric, with the exception of bovine-seminal ribonuclease (BS-RNase). BS-RNase is formed by swapping the N-terminal helices across the two monomeric units. A molecular-dynamics (MD) study has been performed on the protein for a simulation time of 5.5,ns to understand the factors responsible for the stability of the dimer. Essential dynamics analysis and motional correlation of the protein atoms yielded the picture of a stabilising, yet flexible, interface. We have investigated the role of intermolecular H-bonding, protein/water interaction, and protein/water networks in stabilising the dimer. The networks of interchain H-bonds involving side-chain/side-chain or side-chain/main-chain (ScHB) interactions between the two chains have also been studied. The ability of protein atoms in retaining particular H2O molecules was investigated as a function of the accessible surface area (ASA), depth, and hydration parameters, as well as their participation in protein/water networks. [source] Optimal design of single-contaminant regeneration reuse water networks with process decompositionAICHE JOURNAL, Issue 4 2010Jie Bai Abstract Water network with regeneration schemes (e.g., regeneration reuse, regeneration recycling) can reduce freshwater consumption further than water network merely with direct reuse. Regeneration reuse, compared with regeneration recycling, can additionally avoid unexpected accumulation of contaminants. Owing to these features, process decomposition can help to reduce freshwater usage and wastewater discharge of regeneration reuse water systems and achieve the results, which graphical method delivers. In this article, the effect of decomposition on water-using process and further on regeneration reuse water system is briefly analyzed on the concentration-mass load diagram. Then a superstructure and three sequential mathematical models, which take process decomposition into account, are in turn developed to optimize single contaminant regeneration reuse water systems. By several examples, the reliability of the models is verified. Moreover, several decomposition strategies are summarized to realize the regeneration reuse water network, which attains the targets from graphical method. The results indicate that postregeneration concentration has a major impact on the scheme of process decomposition. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Collagen structure: The molecular source of the tendon magic angle effectJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2007Gary D. Fullerton PhD Abstract This review of tendon/collagen structure shows that the orientational variation in MRI signals from tendon, which is referred to as the "magic angle" (MA) effect, is caused by irreducible separation of charges on the main chain of the collagen molecule. These charges are held apart in a vacuum by stereotactic restriction of protein folding due in large part to a high concentration of hydroxyproline ring residues in the amino acids of mammalian collagen. The elevated protein electrostatic energy is reduced in water by the large dielectric constant of the highly polar solvent (, , 80). The water molecules serve as dielectric molecules that are bound by an energy that is nearly equivalent to the electrostatic energy between the neighboring positive and negative charge pairs in a vacuum. These highly immobilized water molecules and secondary molecules in the hydrogen-bonded water network are confined to the transverse plane of the tendon. Orientational restriction causes residual dipole coupling, which is directly responsible for the frequency and phase shifts observed in orientational MRI (OMRI) described by the MA effect. Reference to a wide range of biophysical measurements shows that native hydration is a monolayer on collagen hm = 1.6 g/g, which divides into two components consisting of primary hydration on polar surfaces hpp = 0.8 g/g and secondary hydration hs = 0.8 g/g bridging over hydrophobic surface regions. Primary hydration further divides into side-chain hydration hpsc = 0.54 g/g and main-chain hydration hpmc = 0.263 g/g. The main-chain fraction consists of water that bridges between charges on the main chain and is responsible for almost all of the enthalpy of melting ,H = 70 J/g-dry mass. Main-chain water bridges consist of one extremely immobilized Ramachandran water bridge per tripeptide hRa = 0.0658 g/g and one double water bridge per tripeptide hdwb = 0.1974 g/g, with three water molecules that are sufficiently slowed to act as the spin-lattice relaxation sink for the entire tendon. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc. [source] Iron uptake is essential for Escherichia coli survival in drinking waterLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2006D. Grandjean Abstract Aims:, The aim of this study was to elucidate if the need for iron for Escherichia coli to remain cultivable in a poorly nutritive medium such as the drinking water uses the iron transport system via the siderophores. Methods and Results:, Environmental strains of E. coli (isolated from a drinking water network), referenced strains of E. coli and mutants deficient in TonB, an essential protein for iron(III) acquisition, were incubated for 3 weeks at 25°C, in sterile drinking water with and without lepidocrocite (, -FeOOH), an insoluble iron corrosion product. Only cells with a functional iron transport system were able to survive throughout the weeks. Conclusions:, The iron transport system via protein TonB plays an essential role on the survival of E. coli in a weakly nutritive medium like drinking water. Significance and Impacts of the Study:, Iron is a key parameter involved in coliform persistence in drinking water distribution systems. [source] Near-atomic resolution structures of urate oxidase complexed with its substrate and analogues: the protonation state of the ligandACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2010Laure Gabison Urate oxidase (uricase; EC 1.7.3.3; UOX) from Aspergillus flavus catalyzes the oxidation of uric acid in the presence of molecular oxygen to 5-hydroxyisourate in the degradation cascade of purines; intriguingly, catalysis proceeds using neither a metal ion (Fe, Cu etc.) nor a redox cofactor. UOX is a tetrameric enzyme with four active sites located at the interface of two subunits; its structure was refined at atomic resolution (1,Å) using new crystal data in the presence of xanthine and at near-atomic resolution (1.3,1.7,Å) in complexes with the natural substrate (urate) and two inhibitors: 8-nitroxanthine and 8-thiouric acid. Three new features of the structural and mechanistic behaviour of the enzyme were addressed. Firstly, the high resolution of the UOX,xanthine structure allowed the solution of an old structural problem at a contact zone within the tetramer; secondly, the protonation state of the substrate was determined from both a halochromic inhibitor complex (UOX,8-nitroxanthine) and from the H-atom distribution in the active site, using the structures of the UOX,xanthine and the UOX,uric acid complexes; and thirdly, it was possible to extend the general base system, characterized by the conserved catalytic triad Thr,Lys,His, to a large water network that is able to buffer and shuttle protons back and forth between the substrate and the peroxo hole along the reaction pathway. [source] Preliminary joint neutron and X-ray crystallographic study of human carbonic anhydrase IIACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009S. Z. Fisher Carbonic anhydrases catalyze the interconversion of CO2 to HCO3,, with a subsequent proton-transfer (PT) step. PT proceeds via a proposed hydrogen-bonded water network in the active-site cavity that is stabilized by several hydrophilic residues. A joint X-ray and neutron crystallographic study has been initiated to determine the specific water network and the protonation states of the hydrophilic residues that coordinate it in human carbonic anhydrase II. Time-of-flight neutron crystallographic data have been collected from a large (,1.2,mm3) hydrogen/deuterium-exchanged crystal to 2.4,Å resolution and X-ray crystallographic data have been collected from a similar but smaller crystal to 1.5,Å resolution. Obtaining good-quality neutron data will contribute to the understanding of the catalytic mechanisms that utilize water networks for PT in protein environments. [source] Molecular Mechanism of the Hydration of Candida antarctica Lipase B in the Gas Phase: Water Adsorption Isotherms and Molecular Dynamics SimulationsCHEMBIOCHEM, Issue 18 2009Ricardo J. F. Branco Dr. Abstract Hydration is a major determinant of activity and selectivity of enzymes in organic solvents or in gas phase. The molecular mechanism of the hydration of Candida antarctica lipase B (CALB) and its dependence on the thermodynamic activity of water (aw) was studied by molecular dynamics simulations and compared to experimentally determined water sorption isotherms. Hydration occurred in two phases. At low water activity, single water molecules bound to specific water binding sites at the protein surface. As the water activity increased, water networks gradually developed. The number of protein-bound water molecules increased linearly with aw, until at aw=0.5 a spanning water network was formed consisting of 311 water molecules, which covered the hydrophilic surface of CALB, with the exception of the hydrophobic substrate-binding site. At higher water activity, the thickness of the hydration shell increased up to 10 Å close to aw=1. Above a limit of 1600 protein-bound water molecules the hydration shell becomes unstable and the formation of pure water droplets occurs in these oversaturated simulation conditions. While the structure and the overall flexibility of CALB was independent of the hydration state, the flexibility of individual loops was sensitive to hydration: some loops, such as those part of the substrate-binding site, became more flexible, while other parts of the protein became more rigid upon hydration. However, the molecular mechanism of how flexibility is related to activity and selectivity is still elusive. [source] Global Minimum-Energy Structure and Spectroscopic Properties of I2.,,n,H2O Clusters: A Monte Carlo Simulated Annealing StudyCHEMPHYSCHEM, Issue 1 2010Arup Kumar Pathak Abstract The vibrational (IR and Raman) and photoelectron spectral properties of hydrated iodine-dimer radical-anion clusters, I2.,,n,H2O (n=1,10), are presented. Several initial guess structures are considered for each size of cluster to locate the global minimum-energy structure by applying a Monte Carlo simulated annealing procedure including spin,orbit interaction. In the Raman spectrum, hydration reduces the intensity of the II stretching band but enhances the intensity of the OH stretching band of water. Raman spectra of more highly hydrated clusters appear to be simpler than the corresponding IR spectra. Vibrational bands due to simultaneous stretching vibrations of OH bonds in a cyclic water network are observed for I2.,,n,H2O clusters with n,3. The vertical detachment energy (VDE) profile shows stepwise saturation that indicates closing of the geometrical shell in the hydrated clusters on addition of every four water molecules. The calculated VDE of finite-size small hydrated clusters is extrapolated to evaluate the bulk VDE value of I2., in aqueous solution as 7.6 eV at the CCSD(T) level of theory. Structure and spectroscopic properties of these hydrated clusters are compared with those of hydrated clusters of Cl2., and Br2.,. [source] Water pipeline failure due to water hammer effectsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2006C. SCHMITT ABSTRACT A numerical model has been established in order to simulate the propagation of pressure waves in water networks. The present model formulation is based on a system of partial hyperbolic differential equations. This system has been solved via the characteristics method. The current model provides the necessary data and the necessary damping of water hammer waves, taking into account the structure of the pipe network and the pressure loss. The numerical algorithm estimates the maximum pressure values resulting from the water hammer when closing valves in the network and consequently, the maximum stresses in the pipes have been calculated. In the case of simultaneous closing of several valves, the over pressure can exceed the admissible pressure. In this case, the severity of a defect such as a corrosion crater (pit) has been estimated by computing a safety factor for the stress distribution at the defect tip. This allows the applied notch stress intensity factor to be obtained. To investigate the defect geometry effects, semi-spherical and semi-elliptical defects are deemed to exist in up to one-half of the thickness of the pipe wall. The outcomes have been introduced into the structural integrity assessment procedure (SINTAP) failure diagram assessment (FAD) in order to obtain the safety factor value. Conventionally, it is considered that a failure hazard exists if this safety factor is less than two. [source] Application of ozone treatment and pinch technology in cooling water systems design for water and energy conservationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2010A. Ataei Abstract Re-circulating cooling water systems offer the means to remove heat from a wide variety of industrial processes that generate excess heat. Such systems consist of a cooling tower and a heat-exchanger network that conventionally has a parallel configuration. However, reuse of water between different cooling duties allows cooling water networks to be designed in a series arrangement. This results in performance improvement and increased cooling tower capacity. In addition, by the integration of ozone treatment into the cooling tower, the cycle of concentration can be increased. The ozone treatment also dramatically reduces the blow-down that, in turn, is environmentally constructive. In this study, a new environmental-friendly and cost-effective design methodology for cooling water systems was introduced. Using this design methodology, Integrated Ozone Treatment Cooling System (IOTCS), achievement of minimum environmental impacts and total cost were afforded through a simultaneous integration of the cooling system components using an ozone treatment cooling tower and optimum heat-exchanger network configuration. Moreover, in the proposed method, the cooling tower optimum design was achieved through a mathematical model. The IOTCS design method is based upon a complex design approach using a combined pinch analysis and mathematical programming that provides an optimum heat-exchanger configuration while maximizing water and energy conservation and minimizing total cost. Related coding in MATLAB version 7.3 was used for the illustrative example to obtain optimal values in the IOTCS design method computations. The results of the recently introduced design methodology were compared with the conventional method. Copyright © 2009 John Wiley & Sons, Ltd. [source] The Trickle-down Effect: Ideology and the Development of Premium Water Networks in China's CitiesINTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 1 2007ALANA BOLAND This article examines the relationship between networked infrastructure and uneven development in transitional cities through a study of premium water networks in China. Beginning in the mid-1990s, select buildings and housing enclaves began to bypass municipal tap water supply systems through the construction of small-scale secondary pipe networks for purified drinking water. I focus on the early development of these premium water networks to highlight the ideological interplay between a new more market-based approach to networked supply and the existing model characterized by relatively universal and uniform access within cities. I illustrate how this dual water supply model was well suited to the ideological conditions and contradictions associated with China's economic liberalization in the 1990s. While the emergence of premium water networks can be linked to ascendant forms of market reasoning in the environmental and social spheres, I also argue that they were enabled by unresolved ideological tensions associated with China's transitional program. Rather than providing a basis for resistance in the early development of premium water supply, the socialist legacy in urban water supply left its mark more in the noticeable absence of debate regarding the distributional outcomes. By examining premium water networks in relation to the politics of ideology in China's transitional period, my analysis highlights the complex and sometimes unexpected ways that ideologies can influence the development of new infrastructural spaces and processes of splintering urbanism. [source] WATGEN: An algorithm for modeling water networks at protein,protein interfacesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2007Huynh-Hoa Bui Abstract Water molecules at protein,protein interfaces contribute to the close packing of atoms and ensure complementarity between the protein surfaces, as well as mediating polar interactions. Therefore, modeling of interface water is of importance in understanding the structural basis of biomolecular association. We present an algorithm, WATGEN, which predicts locations for water molecules at a protein,protein or protein,peptide interface, given the atomic coordinates of the protein and peptide. A key element of the WATGEN algorithm is the prediction of water sites that can form multiple hydrogen bonds that bridge the binding interface. Trial calculations were performed on water networks predicted by WATGEN at 126 protein,peptide interfaces (X-ray resolutions , 2.0 Å), using different criteria for water placement. The energies of the predicted water networks were evaluated in AMBER8 and used in the choice of parameters for WATGEN. The 126 interfaces include 1264 experimentally determined bridging water sites, and the WATGEN algorithm predicts 72 and 88% of these sites within 1.5 and 2.0 Å, respectively. The predicted number of water molecules at each interface was much higher than the number of water molecules identified experimentally. Therefore, random placement of the same number of water molecules as that predicted at each interface was performed as a control, and resulted in only 22 and 40% of water sites placed within 1.5 and 2.0 Å of experimental sites, respectively. Based on these data, we conclude that WATGEN can accurately predict the location of water molecules at a protein,peptide interface, and this may be of value for understanding the energetics and specificity of biomolecular association. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Optimal design of single-contaminant regeneration reuse water networks with process decompositionAICHE JOURNAL, Issue 4 2010Jie Bai Abstract Water network with regeneration schemes (e.g., regeneration reuse, regeneration recycling) can reduce freshwater consumption further than water network merely with direct reuse. Regeneration reuse, compared with regeneration recycling, can additionally avoid unexpected accumulation of contaminants. Owing to these features, process decomposition can help to reduce freshwater usage and wastewater discharge of regeneration reuse water systems and achieve the results, which graphical method delivers. In this article, the effect of decomposition on water-using process and further on regeneration reuse water system is briefly analyzed on the concentration-mass load diagram. Then a superstructure and three sequential mathematical models, which take process decomposition into account, are in turn developed to optimize single contaminant regeneration reuse water systems. By several examples, the reliability of the models is verified. Moreover, several decomposition strategies are summarized to realize the regeneration reuse water network, which attains the targets from graphical method. The results indicate that postregeneration concentration has a major impact on the scheme of process decomposition. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Preliminary joint neutron and X-ray crystallographic study of human carbonic anhydrase IIACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009S. Z. Fisher Carbonic anhydrases catalyze the interconversion of CO2 to HCO3,, with a subsequent proton-transfer (PT) step. PT proceeds via a proposed hydrogen-bonded water network in the active-site cavity that is stabilized by several hydrophilic residues. A joint X-ray and neutron crystallographic study has been initiated to determine the specific water network and the protonation states of the hydrophilic residues that coordinate it in human carbonic anhydrase II. Time-of-flight neutron crystallographic data have been collected from a large (,1.2,mm3) hydrogen/deuterium-exchanged crystal to 2.4,Å resolution and X-ray crystallographic data have been collected from a similar but smaller crystal to 1.5,Å resolution. Obtaining good-quality neutron data will contribute to the understanding of the catalytic mechanisms that utilize water networks for PT in protein environments. [source] A preliminary neutron crystallographic study of an A-DNA crystalACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009Ricardo M. F. Leal The LADI-III diffractometer at the Institut Laue,Langevin has been used to carry out a preliminary neutron crystallographic study of the self-complementary DNA oligonucleotide d(AGGGGCCCCT)2 in the A conformation. The results demonstrate the viability of a full neutron crystallographic analysis with the aim of providing enhanced information on the ion,water networks that are known to be important in stabilizing A-DNA. This is the first account of a single-crystal neutron diffraction study of A-DNA. The study was carried out with the smallest crystal used to date for a neutron crystallographic study of a biological macromolecule. [source] | |||||||||||||