http://precedings.nature.com/tags/water Recently posted documents tagged with 'water' Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://dx.doi.org/10.1038/npre.2009.3617.1 Background/Question/MethodsThe demand for fresh water has largely outpaced supply both globally and locally with current water management policies unable to meet the needs of urban, agricultural, and industrial activities. Irrigation is one of the many anthropogenic uses of water and is arguably the most important maintenance factor in a landscape. This is particularly true in an arid climate, such as the Central Valley of California. Urban residents’ decisions about the design and maintenance of their landscapes affect bird species richness. Published research indicates that these decisions are also affected by the residents’ socioeconomic status. However, the driver of this relationship remains unknown. This paper uses data from the Fresno Bird Count, a citizen science organization, to test the hypothesis that neighborhood socioeconomic status influences residential irrigation regimes, which influences plant cover, in turn influencing bird diversity and abundance. A random sampling grid containing 460 points are used as locations for five minute point counts for the Fresno Bird Count (fresnobirds.org). Socioeconomic data has been obtained from the U.S. Census and irrigation regimes from the city of Fresno. Aerial imagery and ground sampling on point count locations are used for characterizing habitat.Results/ConclusionsPreliminary analysis of the first year of data (2008) supports this hypothesis and reveals a north/south gradient of bird diversity paralleling the socioeconomic gradient of Fresno. This paper will present results from a more comprehensive analysis of data including the spring 2009 bird census. Policies in the U.S. regarding the distribution and cost of water are changing in response to increased water demands, and the city of Fresno is about to undergo such a change. In 2013 a policy of metered water is scheduled to begin, which is predicted to increase water conservation by residents due to an increase in it overall cost. In addition to examining coupled socio-ecological drivers of urban diversity, this study will be the first part of a Before After Control Impact experiment taking advantage of the planned implementation of metering the cost of water use. The results can help guide the city in improving its management of urban habitat and biodiversity. http://dx.doi.org/10.1038/npre.2009.3617.1 Mon, 17 Aug 2009 10:52:21 UTC Residential irrigation as a driver of urban bird communities doi:10.1038/npre.2009.3617.1 2009-08-17 Madhusudan Katti Nature Precedings 2009-08-17T10:52:21Z Poster Ecology Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3520/version/1 Nitrogen provides a fundamental building block for life. However, some nitrogen species (e.g., NO3) cause water quality degradation and contribute to climatic warming as a greenhouse gas (e.g., N2O). Denitrification is a central process in the nitrogen cycle, transforming water-soluble nitrogen to gaseous nitrogen, thereby removing nitrogen from the system. The factors controlling denitrification are known, yet the general quantitative comparison of controls on denitrification remains a rich area of study. Understanding the relative importance of various controls over denitrification is critical given its biological importance, role in the Earth system, and the current perturbation of the global nitrogen cycle by human activity. We demonstrate that the ‘effective’ denitrification rate constant (first-order constant; ke [T-1]) and advective water transport (mean residence time; τ [T]) scale inversely across diverse systems, ranging from hillslopes and groundwater to large lakes and estuaries. As a result, we observe a relatively constant nitrogen removal across nine orders of magnitude in transport time scales. A central question remains as to why ke scales approximately linearly with τ. We suggest that the variability of ke arises from hydrologic masking of an intrinsic denitrification rate constant (kden). A two-compartment model shows how ke varies with the amount of advective water, and thus τ, explaining how denitrification losses in the reactive zone of a system are controlled by mass transfer to that reactive zone. Our finding highlights mean residence time in the advective zone as a primary control on effective rates of denitrification, while other factors (e.g., nitrate and organic carbon concentrations) provide secondary controls. Furthermore, the relationship between ke and τ demonstrates the strong coupling of the water and nitrogen cycles. http://precedings.nature.com/documents/3520/version/1 Thu, 06 Aug 2009 09:42:05 UTC Effective denitrification scales predictably with water residence time across diverse systems hdl:10101/npre.2009.3520.1 2009-08-06 Mark B. Green Nature Precedings 2009-08-06T09:42:05Z Manuscript Ecology Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/3432/version/2 Expression of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2) has been shown to increase WUE in rice by Karaba et al 2007 (PNAS, 104:15270–15275). We conducted a detail analysis of the complete sorghum genome for the similarity/presence of either DNA, mRNA or protein product of the Arabidopsis HARDY (hrd) DNA binding transcription factor (555 bp present on chromosome 2). Chromosome 6 showed a sequence match of 61.5 percent positive between 61 and 255 mRNA residues of the query region. Further confirmation was obtained by TBLASTN which showed that chromosome 6 of the sorghum genome has a region between 54948120 and 54948668 which has 80 amino acid similarities out of the 185 residues. A homology model was constructed and verified using Anolea, Gromos and Verify3D. Scanning the motif for possible activation sites revealed that there was a protein kinase C phosphorylation site between 15th and 20th residue. The study indicates the possibility of the presence of a DNA binding transcription factor in chromosome 6 of Sorghum bicolor with 60 percent similarity to that of Arabidopsis hrd DNA binding transcription factor. http://precedings.nature.com/documents/3432/version/2 Mon, 20 Jul 2009 09:09:06 UTC In silico analysis for the presence of HARDY an Arabidopsis drought tolerance DNA binding transcription factor product in chromosome 6 of Sorghum bicolor genome hdl:10101/npre.2009.3432.2 2009-07-20 Arun K. Shanker Nature Precedings 2009-07-20T09:09:06Z Manuscript Bioinformatics http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.2636.1 Within the scope of producing clean fossil fuels by simultaneously tackling greenhouse gas emissions, the interfacial tension of partially miscible phases containing CO2 is being investigated with the pendant drop method. Emphasis is given to measurements at elevated pressures and temperatures, analogous to reservoir conditions. A high pressure apparatus consisting of a view cell and high pressure capillary fittings is used for creating pendent drops at the desired conditions. A computer aided Drop Shape Analysis system is used for capturing images of such drops, which are then analysed for the interfacial tension calculation of the two phases with the KRUSS DSA software. The results acquired from the initial measurements conducted for the H2O/CO2 system are presented in comparison with literature data. http://dx.doi.org/10.1038/npre.2008.2636.1 Fri, 12 Dec 2008 17:34:45 UTC Pendent Drops at Elevated P & T doi:10.1038/npre.2008.2636.1 2008-12-12 Apostolos Georgiadis Nature Precedings 2008-12-12T17:34:45Z Poster Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.2649.1 Acquiring a comprehensive understanding of the behaviour of carbon dioxide under reservoir conditions is essential for optimizing its usage in enhanced oil recovery (EOR) and for developing sequestration schemes. In order to obtain this understanding, it is necessary to study the physical properties and phase behaviour of mixtures of carbon dioxide with hydrocarbons and brines under conditions of high pressure. In this work we are addressing both the experimental and the theoretical aspects of this problem. A new apparatus, based on the static-analytical method, has been developed to measure phase equilibrium. The equipment comprises a high-pressure cell with sapphire windows for visual observation and phase sampling, with on-line gas chromatography analysis, for measuring the phase compositions. The experimental work is complemented with a theoretical modelling for these mixtures, using the statistical association fluid theory for potentials of variable range (SAFT-VR). As an example of the predictive capabilities of the equation, the fluid phase behaviour of the mixture (carbon dioxide + n-decane) is presented. http://dx.doi.org/10.1038/npre.2008.2649.1 Fri, 12 Dec 2008 17:33:17 UTC Measurement & Prediction of Phase Behaviour of Carbon Dioxide Mixtures doi:10.1038/npre.2008.2649.1 2008-12-12 Esther Forte Nature Precedings 2008-12-12T17:33:17Z Poster Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/2476/version/1 The chemical nature of aqueous electrolyte ionization is illustrated by a simple relationship with water as a reactant believed to correlate ionization of aqueous sodium chloride approaching infinite dilution over the entire range of temperature and pressure [0 to 1000oC; 0.1 to 1000 MPa (10000 Atm)]. The derived equation accurately and smoothly describes the ionization constant of sodium chloride [K(NaCl)] in both water and water strongly diluted by inert solvent. Effects of water density on ionization are quantitatively and simply described that oppose conventional theory that ionization is a function only of dielectric constant, and theorists should apply this simplicity with density in understanding aqueous electrolyte ionization. There appears to be no substantive evidence for Pitzer’s earlier proposal (1983) that K(NaCl) with decreasing very low densities (if known) would diverge sharply downward by several orders of magnitude. Classical ionization theories are limited in universal application, and it seems that theory must adjust to this observed simple fundamental relationship. http://precedings.nature.com/documents/2476/version/1 Thu, 06 Nov 2008 18:08:50 UTC Aqueous Electrolyte Ionization over Extreme Ranges as Simple Fundamental Relation with Density and Believed Universal; Sodium Chloride Ionization from 0o to 1000oC and to 1000 MPa (10000 Atm.) hdl:10101/npre.2008.2476.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T18:08:50Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/2474/version/1 Examinations of past complex theoretical equations describing isothermal dielectric constants (ε) of liquids show that none describe experiments throughout and that only a two-constant equation of density is required. The dielectric susceptibility (ε – 1) as a simple exponential function of density is shown here to describe ε for both polar and non-polar organic liquids over all available experimental ranges from 0.50 to 1.2 g cm-3 and temperatures to 400oC. For water above 0.25 g cm-3, the equation describes the excellent dielectric-constant formulation of Fernández, et al., (1997) throughout its experimental range [-35 to +600oC; to 1000 MPa (10000 Atm)] and even when diluted by “inert” solvents (Marshall, 2008). At lower densities at all temperatures, water susceptibilities converge to an even more simple unit proportionality to density below 0.003 g cm-3, not yet verified for organics without experiment. While the past Born, Tait, Clausius-Mossotti, and Owen-Brinkley theories describe ε equally well over a limited 10% change in density, all are shown to fail over greater ranges. The simple density relation presented here should be useful in clarifying and reducing complexity of theory applied to liquid structure. http://precedings.nature.com/documents/2474/version/1 Thu, 06 Nov 2008 17:59:24 UTC Dielectric Constant of Liquids (Fluids) Shown to be Simple Fundamental Relation of Density over Extreme Ranges from – 50o to + 600oC, Believed Universal hdl:10101/npre.2008.2474.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T17:59:24Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2008.2472.1 The experimental static dielectric constants (ε) of water formulated by Fernández, et al., (1997-International Association for the Properties of Water and Steam, IAPWS), –35 to 600oC; 0.1 to 1200 MPa, are discovered to be closely described throughout by a simple equation of density (ρ), presented here, and agreeing with their reported calculated (extrapolated) values to 923oC. Eight limiting boundary conditions are observed. Values of ε follow isothermal straight-line slopes of log (ε – 1) vs log ρ down to densities of 0.25 g cm-3 water, even in dioxane-water solutions. At lower densities, all slopes curve asymptotically in approaching unity, while becoming unity throughout at –35oC (near metastable freezing point). Slopes above 0.25 g cm-3 asymptotically approach 1 2/3 at high temperatures that numerically proportionates (ε – 1) to volume times surface densities, with a proposed explanation given. Values for ε of water dissolved in dioxane down to 0.006 g cm-3 water (25-300oC) and in benzene to 0.014 g cm-3 water (300-400oC) extend uninterrupted from those for pure water. The Deul-Franck (1984, 1991) values of ε for benzene (25-400oC; to 400 MPa) by the relationship fall on a single straight-line independent of temperature. Theorists should evaluate this simple relationship of water and other liquids to density that appears to be universal. http://dx.doi.org/10.1038/npre.2008.2472.1 Thu, 06 Nov 2008 17:56:46 UTC Dielectric Constant of Water Discovered to be Simple Function of Density over Extreme Ranges from – 35 to + 600oC and to 1200 MPa (12000 Atm.), Believed Universal doi:10.1038/npre.2008.2472.1 2008-11-06 William L. Marshall Nature Precedings 2008-11-06T17:56:46Z Manuscript Chemistry Earth & Environment http://creativecommons.org/licenses/by/3.0/