PERCHLORATE CROP INTERACTIONS VIA CONTAMINATED IRRIGATION WATER

EPA Science Inventory

Perchlorate has contaminated water and sods at several locations in the United States. Perchlorate is water soluble, exceedingly mobile in aqueous systems, and can persist for many decades under typical ground- and surface water conditions. Perchlorate is of concern because of un...

Role of water mediated interactions in protein-protein recognition landscapes.

PubMed

Papoian, Garegin A; Ulander, Johan; Wolynes, Peter G

2003-07-30

The energy landscape picture of protein folding and binding is employed to optimize a number of pair potentials for direct and water-mediated interactions in protein complex interfaces. We find that water-mediated interactions greatly complement direct interactions in discriminating against various types of trap interactions that model those present in the cell. We highlight the context dependent nature of knowledge-based binding potentials, as contrasted with the situation for autonomous folding. By performing a Principal Component Analysis (PCA) of the corresponding interaction matrixes, we rationalize the strength of the recognition signal for each combination of the contact type and reference trap states using the differential in the idealized "canonical" amino acid compositions of native and trap layers. The comparison of direct and water-mediated contact potential matrixes emphasizes the importance of partial solvation in stabilizing charged groups in the protein interfaces. Specific water-mediated interresidue interactions are expected to influence significantly the kinetics as well as thermodynamics of protein association.

Analytical theory of the hydrophobic effect of solutes in water.

PubMed

Urbic, Tomaz; Dill, Ken A

2017-09-01

We develop an analytical statistical-mechanical model for hydrophobic solvation in water. In this three-dimensional Mercedes-Benz-like model, two neighboring waters have three possible interaction states: a radial van der Waals interaction, a tetrahedral orientation-dependent hydrogen-bonding interaction, or no interaction. Nonpolar solutes are modeled as van der Waals particles of different radii. The model is sufficiently simple that we can calculate the partition function and thermal and volumetric properties of solvation versus temperature, pressure, and solute radius. Predictions are in good agreement with results of Monte Carlo simulations. And their trends agree with experiments on hydrophobic solute insertion. The theory shows that first-shell waters are more highly structured than bulk waters, because of hydrogen bonding, and that that structure melts out faster with temperature than it does in bulk waters. Because the theory is analytical, it can explore a broad range of solvation properties and anomalies of water, at minimal computational expense.

Analytical theory of the hydrophobic effect of solutes in water

NASA Astrophysics Data System (ADS)

Urbic, Tomaz; Dill, Ken A.

2017-09-01

We develop an analytical statistical-mechanical model for hydrophobic solvation in water. In this three-dimensional Mercedes-Benz-like model, two neighboring waters have three possible interaction states: a radial van der Waals interaction, a tetrahedral orientation-dependent hydrogen-bonding interaction, or no interaction. Nonpolar solutes are modeled as van der Waals particles of different radii. The model is sufficiently simple that we can calculate the partition function and thermal and volumetric properties of solvation versus temperature, pressure, and solute radius. Predictions are in good agreement with results of Monte Carlo simulations. And their trends agree with experiments on hydrophobic solute insertion. The theory shows that first-shell waters are more highly structured than bulk waters, because of hydrogen bonding, and that that structure melts out faster with temperature than it does in bulk waters. Because the theory is analytical, it can explore a broad range of solvation properties and anomalies of water, at minimal computational expense.

Two-state protein model with water interactions: Influence of temperature on the intrinsic viscosity of myoglobin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakk, Audun

2001-06-01

We describe a single-domain protein as a two-state system with water interactions. Around the unfolded apolar parts of the protein we incorporate the hydration effect by introducing hydrogen bonds between the water molecules in order to mimic the {open_quotes}icelike{close_quotes} shell structure. Intrinsic viscosity, proportional to the effective hydrodynamic volume, for sperm whale metmyoglobin is assigned from experimental data in the folded and in the denaturated state. By weighing statistically the two states against the degree of folding, we express the total intrinsic viscosity. The temperature dependence of the intrinsic viscosity, for different chemical potentials, is in good correspondence with experimentalmore » data [P. L. Privalov , J. Mol. Biol. >190, 487 (1986)]. Cold and warm unfolding, common to small globular proteins, is also a result of the model.« less

PERCHLORATE-CROP INTERACTIONS FROM CONTAMINATED IRRIGATION WATER AND FERTILIZER APPLICATIONS

EPA Science Inventory

Perchlorate has contaminated water and soils at several locations in the United States. Perchlorate is water soluble, exceedingly mobile in aqueous systems, and can persist for many decades under typical ground and surface water conditions. Perchlorate is of concern because of un...

Water demands for electricity generation in the U.S.: Modeling different scenarios for the water–energy nexus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Lu; Hejazi, Mohamad I.; Patel, Pralit L.

Water withdrawal for electricity generation in the United States accounts for approximately half the total freshwater withdrawal. With steadily growing electricity demands, a changing climate, and limited water supplies in many water-scarce states, meeting future energy and water demands poses a significant socio-economic challenge. Employing an integrated modeling approach that can capture the energy-water interactions at regional and national scales is essential to improve our understanding of the key drivers that govern those interactions and the role of national policies. In this study, the Global Change Assessment Model (GCAM), a technologically-detailed integrated model of the economy, energy, agriculture and landmore » use, water, and climate systems, was extended to model the electricity and water systems at the state level in the U.S. (GCAM-USA). GCAM-USA was employed to estimate future state-level electricity generation and consumption, and their associated water withdrawals and consumption under a set of six scenarios with extensive details on the generation fuel portfolio, cooling technology mix, and their associated water use intensities. Six scenarios of future water demands of the U.S. electric-sector were explored to investigate the implications of socioeconomics development and growing electricity demands, climate mitigation policy, the transition of cooling systems, electricity trade, and water saving technologies. Our findings include: 1) decreasing water withdrawals and substantially increasing water consumption from both climate mitigation and the conversion from open-loop to closed-loop cooling systems; 2) open trading of electricity benefiting energy scarce yet demand intensive states; 3) within state variability under different driving forces while across state homogeneity under certain driving force ; 4) a clear trade-off between water consumption and withdrawal for the electricity sector in the U.S. The paper discusses this withdrawal-consumption trade-off in the context of current national policies and regulations that favor decreasing withdrawals (increasing consumptive use), and the role of water saving technologies. The highly-resolved nature of this study both geographically and technologically provides a useful platform to address scientific and policy relevant and emerging issues at the heart of the water-energy nexus in the U.S.« less

Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water-molecular interactions and states of water.

PubMed

Pastorczak, Marcin; Dominguez-Espinosa, Gustavo; Okrasa, Lidia; Pyda, Marek; Kozanecki, Marcin; Kadlubowski, Slawomir; Rosiak, Janusz M; Ulanski, Jacek

2014-01-01

Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the pre-melting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above -60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting.

Protein-lipid interactions at the air/water interface.

PubMed

Lad, Mitaben D; Birembaut, Fabrice; Frazier, Richard A; Green, Rebecca J

2005-10-07

Surface pressure measurements and external reflection FTIR spectroscopy have been used to probe protein-lipid interactions at the air/water interface. Spread monomolecular layers of stearic acid and phosphocholine were prepared and held at different compressed phase states prior to the introduction of protein to the buffered subphase. Contrasting interfacial behaviour of the proteins, albumin and lysozyme, was observed and revealed the role of both electrostatic and hydrophobic interactions in protein adsorption. The rate of adsorption of lysozyme to the air/water interface increased dramatically in the presence of stearic acid, due to strong electrostatic interactions between the negatively charged stearic acid head group and lysozyme, whose net charge at pH 7 is positive. Introduction of albumin to the subphase resulted in solubilisation of the stearic acid via the formation of an albumin-stearic acid complex and subsequent adsorption of albumin. This observation held for both human and bovine serum albumin. Protein adsorption to a PC layer held at low surface pressure revealed adsorption rates similar to adsorption to the bare air/water interface and suggested very little interaction between the protein and the lipid. For PC layers in their compressed phase state some adsorption of protein occurred after long adsorption times. Structural changes of both lysozyme and albumin were observed during adsorption, but these were dramatically reduced in the presence of a lipid layer compared to that of adsorption to the pure air/water interface.

INTERACTIVE WORKSHOP ON ARSENIC REMOVAL FROM DRINKING WATER

EPA Science Inventory

In 2005, EPA's Office of Water and Office of Research and Development collaborated to present eleven arsenic training events. The workshops provided in-depth treatment technology training to help those affected; state drinking water staff, design engineers, system owners and cert...

On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazil, J.; Feingold, G.; Wang, Hailong

2014-01-02

The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. Itmore » is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.« less

Interactions between groundwater and surface water: The state of the science

USGS Publications Warehouse

Sophocleous, M.

2002-01-01

The interactions between groundwater and surface water are complex. To understand these interactions in relation to climate, landform, geology, and biotic factors, a sound hydrogeoecological framework is needed. All these aspects are synthesized and exemplified in this overview. In addition, the mechanisms of interactions between groundwater and surface water (GW-SW) as they affect recharge-discharge processes are comprehensively outlined, and the ecological significance and the human impacts of such interactions are emphasized. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. This overview concludes with a discussion of research needs and challenges facting this evolving field. The biogeochemical processes within the upper few centimeters of sediments beneath nearly all surface-water bodies (hyporheic zone) have a profound effect on the chemistry of the water interchange, and here is where most of the recent research has been focusing. However, to advance conceptual and other modeling of GW-SW systems, a broader perspective of such interactions across and between surface-water bodies is needed, including multidimensional analyses, interface hydraulic characterization and spatial variability, site-to-region regionalization approaches, as well as cross-disciplinary collaborations.

Influence of Poly(ethylenimine) on the Monolayer of Oleic Acid at the Air/Water Interface.

PubMed

Hwan Ha, Tai; Kyu Kim, Dai; Choi, Myung-Un; Kim, Kwan

2000-06-01

The effect of poly(ethylenimine) (PEI) dissolved in water on the surface pressure-area isotherm of oleic acid (OA) at the air/water interface was investigated. On a concentrated PEI solution, the isotherm of the OA monolayers exhibited a noticeable difference as a function of subphase pH. PEI caused the collapse pressure of the OA monolayer to increase up to 45 mN/m, due to a stronger acid-base-type interaction occurring between the amine group of the PEI and the carboxyl group of OA; on a pure water subphase, the collapse pressure was;28 mN/m. On the other hand, owing to a stronger OA-PEI interaction, the OA monolayers favored a liquid-expanded state more on the PEI-containing water subphase than on the pure water. From the QCM measurement, each OA molecule appeared to interact, on average, with 4.3-5.8 ethylenimine repeating units at basic pHs. We also found that OA multilayers could be assembled on a hydrophilic substrate by a Z-type Langmuir-Blodgett (LB) deposition in a PEI-containing subphase at basic pHs. The ATR-IR spectral data revealed that, in a Z-type LB film, the headgroup of OA was mostly present as carboxylate, interacting in an ionic state with the protonated amine groups of PEI. In acidic conditions, neither a Y-type nor a Z-type deposition was really accomplished. Nonetheless, the ATR-IR spectral data suggested that OA molecules should exist in a monomeric state in a LB film assembled at acidic pHs without PEI while they would form intermolecular hydrogen bridges and/or dimers in the presence of PEI. Copyright 2000 Academic Press.

Protein crowding in solution, frozen and freeze-dried states: small-angle neutron and X-ray scattering study of lysozyme/sorbitol/water systems

NASA Astrophysics Data System (ADS)

Krueger, Susan; Khodadadi, Sheila; Clark, Nicholas; McAuley, Arnold; Cristiglio, Viviana; Theyencheri, Narayanan; Curtis, Joseph; Shalaev, Evgenyi

2015-03-01

For effective preservation, proteins are often stored as frozen solutions or in glassy states using a freeze-drying process. However, aggregation is often observed after freeze-thaw or reconstitution of freeze-dried powder and the stability of the protein is no longer assured. In this study, small-angle neutron and X-ray scattering (SANS and SAXS) have been used to investigate changes in protein-protein interaction distances of a model protein/cryoprotectant system of lysozyme/sorbitol/water, under representative pharmaceutical processing conditions. The results demonstrate the utility of SAXS and SANS methods to monitor protein crowding at different stages of freezing and drying. The SANS measurements of solution samples showed at least one protein interaction peak corresponding to an interaction distance of ~ 90 Å. In the frozen state, two protein interaction peaks were observed by SANS with corresponding interaction distances at 40 Å as well as 90 Å. On the other hand, both SAXS and SANS data for freeze-dried samples showed three peaks, suggesting interaction distances ranging from ~ 15 Å to 170 Å. Possible interpretations of these interaction peaks will be discussed, as well as the role of sorbitol as a cryoprotectant during the freezing and drying process.

Implications of hydrogen/halogen-bond in the stabilization of confined water and anion-water clusters by a cationic receptor

NASA Astrophysics Data System (ADS)

Hoque, Md. Najbul; Das, Gopal

2016-03-01

Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F2-H2O]2- and square shaped chloride-water cluster [Cl2-(H2O)2]2- inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow‧H⋯Ow, N/C/Ow‧H⋯X- (X- = F-, Cl- and I-) H-bonds and electrostatic interactions. Moreover, C-H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I2···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD.

Anthropogenic shift of planktonic food web structure in a coastal lagoon by freshwater flow regulation

NASA Astrophysics Data System (ADS)

Hemraj, Deevesh A.; Hossain, A.; Ye, Qifeng; Qin, Jian G.; Leterme, Sophie C.

2017-03-01

Anthropogenic modification of aquatic systems has diverse impacts on food web interactions and ecosystem states. To reverse the adverse effects of modified freshwater flow, adequate management of discharge is required, especially due to higher water requirements and abstractions for human use. Here, we look at the effects of anthropogenically controlled freshwater flow regimes on the planktonic food web of a Ramsar listed coastal lagoon that is under recovery from degradation. Our results show shifts in water quality and plankton community interactions associated to changes in water flow. These shifts in food web interactions represent modifications in habitat complexity and water quality. At high flow, phytoplankton-zooplankton interactions dominate the food web. Conversely, at low flow, bacteria, viruses and nano/picoplankton interactions are more dominant, with a substantial switch of the food web towards heterotrophy. This switch can be associated with excess organic matter loading, decomposition of dead organisms, and synergistic and antagonistic interactions. We suggest that a lower variability in flow amplitude could be beneficial for the long-term sustaining of water quality and food web interactions, while improving the ecosystem health of systems facing similar stresses as the Coorong.

Anthropogenic shift of planktonic food web structure in a coastal lagoon by freshwater flow regulation

PubMed Central

Hemraj, Deevesh A.; Hossain, A.; Ye, Qifeng; Qin, Jian G.; Leterme, Sophie C.

2017-01-01

Anthropogenic modification of aquatic systems has diverse impacts on food web interactions and ecosystem states. To reverse the adverse effects of modified freshwater flow, adequate management of discharge is required, especially due to higher water requirements and abstractions for human use. Here, we look at the effects of anthropogenically controlled freshwater flow regimes on the planktonic food web of a Ramsar listed coastal lagoon that is under recovery from degradation. Our results show shifts in water quality and plankton community interactions associated to changes in water flow. These shifts in food web interactions represent modifications in habitat complexity and water quality. At high flow, phytoplankton-zooplankton interactions dominate the food web. Conversely, at low flow, bacteria, viruses and nano/picoplankton interactions are more dominant, with a substantial switch of the food web towards heterotrophy. This switch can be associated with excess organic matter loading, decomposition of dead organisms, and synergistic and antagonistic interactions. We suggest that a lower variability in flow amplitude could be beneficial for the long-term sustaining of water quality and food web interactions, while improving the ecosystem health of systems facing similar stresses as the Coorong. PMID:28327643

The influence of self-assembling supramolecular structures on the passive membrane transport of ion-paired molecules.

PubMed

Benaouda, F; Brown, M B; Shah, B; Martin, G P; Jones, S A

2012-12-15

Weak ion-ion interactions, such as those associated with ion-pair formation, are difficult to isolate and characterise in the liquid state, but they have the potential to alter significantly the physicochemical behaviour of molecules in solution. The aim of this work was to gain a better understanding of how ion-ion interactions influenced passive membrane transport. The test system was composed of propylene (PG) glycol, water and diclofenac diethylamine (DDEA). Infrared spectroscopy was employed to determine the nature of the DDEA ion-pair interactions and the drug-vehicle association. Passive transport was assessed using homogeneous synthetic membranes. Solution-state analysis demonstrated that the ion-pair was unperturbed by vehicle composition changes, but the solvent-DDEA interactions were modified. DDEA-PG/water hydrogen bonding influenced the ion-pair solubility (X(dev)) and the solvent interactions slowed transport rate in PG-rich vehicles (0.84±0.05 μg cm(-2) h(-1), at ln(X(dev))=0.57). In water-rich co-solvents, the presence of strong water structuring facilitated a significant increase (p<0.05) in transmembrane penetration rate (e.g. 4.33±0.92 μg cm(-2) h(-1), at ln(X(dev))=-0.13). The data demonstrates that weak ion-ion interactions can result in the embedding of polar entities within a stable solvent complex and spontaneous supramolecular assembly should be considered when interpreting transmembrane transport processes of ionic molecules. Copyright © 2012 Elsevier B.V. All rights reserved.

Wetting of water on graphene nanopowders of different thicknesses

NASA Astrophysics Data System (ADS)

Bera, Bijoyendra; Shahidzadeh, Noushine; Mishra, Himanshu; Belyaeva, Liubov A.; Schneider, Grégory F.; Bonn, Daniel

2018-04-01

We study the wetting of graphene nanopowders by measuring the water adsorption in nanopowder flakes of different flake thicknesses. Chemical analysis shows that the graphene flakes, especially the thin ones, might exist in the partially oxidized state. We observe that the thinnest graphene nanopowder flakes do not adsorb water at all, independent of the relative humidity. Thicker flakes, on the other hand, do adsorb an increasing amount of water with increasing humidity. This allows us to assess their wetting behavior which is actually the result of the competition between the adhesive interactions of water and graphene and the cohesive interactions of water. Explicit calculation of these contributions from the van der Waals interactions confirms that the adhesive interactions between very thin flakes of graphene oxide and water are extremely weak, which makes the flakes superhydrophobic. "Liquid marble" tests with graphene nanopowder flakes confirm the superhydrophobicity. This shows that the origin of the much debated "wetting transparency" of graphene is due to the fact that a single graphene or graphene oxide layer does not contribute significantly to the adhesion between a wetting phase and the substrate.

Quantum coherence and temperature dependence of the anomalous state of nanoconfined water in carbon nanotubes

DOE PAGES

Reiter, George F.; Deb, Aniruddha; Sakurai, Y.; ...

2016-10-17

X-ray Compton scattering measurements of the electron momentum distribution in water confined in both single-walled and double-walled carbon nanotubes (SWNT and DWNT), as a function of temperature and confinement size are presented here together with earlier measurements of the proton momentum distribution in the same systems using neutron Compton scattering. These studies provide a coherent picture of an anomalous state of water that exists because of nanoconfinement. This state cannot be described by the weakly interacting molecule picture. It has unique transport properties for both protons and water molecules. In conclusion, we suggest that knowledge of the excitation spectrum ofmore » this state is needed to understand the enhanced flow of water in cylinders with diameters on the order of 20 Å.« less

INTERACTION OF METHYL-TERT BUTYL ETHER AND WATER STRESS ON SEED GERMINATION AND SEEDLING GROWTH IN SOIL MICROCOSMS

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is a widespread contaminant in surface and ground water in the United States. Frequently irrigation is used to water fields to germinate planted seeds and sustain plant growth. A likely possibility exists that water used may have some MTBE. Our s...

Water as a matrix for life

NASA Technical Reports Server (NTRS)

Pohorille, Andrew

2005-01-01

Life is based on non-covalent interactions. They might be either specific (enzyme-substrate interactions, selective ion transport) or nonspecific (lipid-lipid and lipid-protein interactions needed for membrane integrity, fusion and division). Their strength needs to be properly tuned, and this is mediated by the solvent. If interactions are too weak, there might be undesired response to natural fluctuations of physical and chemical parameters. If they are too strong it could impede kinetics and energetics of cellular processes. Thus, the solvent must allow for balancing these interactions. Physical and chemical properties of solvent provide strong constraints for life. Water exhibits a remarkable trait that it promotes both solvophobic and solvophilic interactions. Solvophobic interactions; related to high dielectric constant of the solvent) are necessary for self-organization of matter whereas solvophilic interactions are needed to ensure solubility of polar species. Water offers a large temperature domain of stable liquid and the characteristics hydrophobic effects are a consequence of the temperature in sensitivity of essential properties of its liquid state. Water, however, is not the only liquid with these favorable properties. I will compare in detail properties of water and other pure liquids or their mixtures that have a high dielectric constant and simultaneously support self-organization. I will also discuss properties of water that are unfavorable to life (e.g. its chemical activity against polymerization reactions) and close with summarizing what are alternatives to water as a matrix of life in space.

Options and Consequences: Water Banking/Leasing Issues Explored for the Rio Grande in Southern New Mexico

NASA Astrophysics Data System (ADS)

Brookshire, D. S.; Coursey, D.; Dimint, A.; Tidwell, V.

2004-12-01

Since 1950, the demand for water has more than doubled in the United States. Historically, growing demands have been met by increasing reservoir capacity and through groundwater mining, often at the expense of environmental and cultural concerns. The future is expected to hold much the same. Demand for water will continue to increase particularly in response to the expanding urban sector, while growing concerns over the environment are prompting interest in allocating more water for in-stream uses. So, where will this water come from? Virtually all water supplies are allocated. Providing for new uses requires a reduction in the amount of water dedicated to existing uses. The water banking/leasing model is formulated within a system dynamics context using the object oriented commercial software package, Powersimä Studio 2003. System dynamics provides a unique mathematical framework for integrating the natural and social processes important to managing natural resources and can provide an interactive interface for engaging the public in the decision process. These system level models focus on capturing the broad structure of the system, specifically the feedback and time delays between interacting subsystems. The spatially aggregated models are computationally efficient allowing simulations to be conducted on a PC in a matter of seconds to minutes. By employing interactive interfaces, these models can be taken directly to the public or decision maker. To demonstrate the water banking/leasing model, application has been made to potential markets on the Rio Grande. Specifically, the model spans the reach between Elephant Butte Reservoir (central New Mexico) and the New Mexico/Texas state line. Primary sectors in the model include climate, surface and groundwater, riparian and aquatic habitat, watershed processes, water quality, water demand (residential, commercial, industrial, institution, and agricultural), economics, policy, and legal institutions. Within the model the basin is divided into four distinct but interacting reaches and a monthly time-step is employed. River operations and water demand trends have been calibrated to historical data.

Waters Without Borders: Scarcity and the Future of State Interactions over Shared Water Resources

DTIC Science & Technology

2010-04-01

urbanization, increasing per capita consumption (associated with globalization and economic development), pollution , and climate change will exacerbate...Standards of Living, and Pollution : Water is fundamental to ensuring an adequate food supply. Agricultural irrigation accounts for 70% of fresh water...Agricultural run-off is also a major source of pollution reducing the quality and availability of drinking water. Energy: Water is also needed for the

Beneficial Reuse of Produced and Flowback Water

EPA Pesticide Factsheets

Water reuse and recycling is a significant issue in the development of oil and gas shale plays in the United StatesDrilling operations – 60,000 to 650,000 gallons per wellHydraulic fracturing operations – 3 million to 5 million gallons per wellDefinition of produced water and flowback waterInteractions of water quality constituents as they relate to water reuse and recyclingTesting criteria in the laboratory and field operations

Methodology to explore interactions between the water system and society in order to identify adaptation strategies

NASA Astrophysics Data System (ADS)

Offermans, A. G. E.; Haasnoot, M.

2009-04-01

Development of sustainable water management strategies involves analysing current and future vulnerability, identification of adaptation possibilities, effect analysis and evaluation of the strategies under different possible futures. Recent studies on water management often followed the pressure-effect chain and compared the state of social, economic and ecological functions of the water systems in one or two future situations with the current situation. The future is, however, more complex and dynamic. Water management faces major challenges to cope with future uncertainties in both the water system as well as the social system. Uncertainties in our water system relate to (changes in) drivers and pressures and their effects on the state, like the effects of climate change on discharges. Uncertainties in the social world relate to changing of perceptions, objectives and demands concerning water (management), which are often related with the aforementioned changes in the physical environment. The methodology presented here comprises the 'Perspectives method', derived from the Cultural Theory, a method on analyzing and classifying social response to social and natural states and pressures. The method will be used for scenario analysis and to identify social responses including changes in perspectives and management strategies. The scenarios and responses will be integrated within a rapid assessment tool. The purpose of the tool is to provide users with insight about the interaction of the social and physical system and to identify robust water management strategies by analysing the effectiveness under different possible futures on the physical, social and socio-economic system. This method allows for a mutual interaction between the physical and social system. We will present the theoretical background of the perspectives method as well as a historical overview of perspective changes in the Dutch Meuse area to show how social and physical systems interrelate. We will also show how the integration of both can contribute to the identification of robust water management strategies.

Subangstrom resolution X-ray structure details aquaporin-water interactions.

PubMed

Eriksson, Urszula Kosinska; Fischer, Gerhard; Friemann, Rosmarie; Enkavi, Giray; Tajkhorshid, Emad; Neutze, Richard

2013-06-14

Aquaporins are membrane channels that facilitate the flow of water across biological membranes. Two conserved regions are central for selective function: the dual asparagine-proline-alanine (NPA) aquaporin signature motif and the aromatic and arginine selectivity filter (SF). Here, we present the crystal structure of a yeast aquaporin at 0.88 angstrom resolution. We visualize the H-bond donor interactions of the NPA motif's asparagine residues to passing water molecules; observe a polarized water-water H-bond configuration within the channel; assign the tautomeric states of the SF histidine and arginine residues; and observe four SF water positions too closely spaced to be simultaneously occupied. Strongly correlated movements break the connectivity of SF waters to other water molecules within the channel and prevent proton transport via a Grotthuss mechanism.

Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida

USDA-ARS?s Scientific Manuscript database

Water quality in Florida is significantly impacted by nitrogen (N) losses from agriculture in a large part of the state, where there is a close interaction between surface water and groundwater that has a high water table. Horticultural crops are planted across large areas of Florida, including area...

A First-Principles Approach to the Dynamics and Electronic Properties of p-Nitroaniline in Water.

PubMed

Cabral, Benedito J Costa; Coutinho, Kaline; Canuto, Sylvio

2016-06-09

Born-Oppenheimer molecular dynamics of p-nitroaniline (PNA) in water was carried out and the electronic structure was investigated by time-dependent density functional theory. Hydrogen bonding involving the PNA nitro and amine groups and the water molecules leads to an ∼160 cm(-1) red shift of the ν(N-O) and ν(N-H) stretching frequencies relative to the gas phase species. Our estimate for the peak position of the charge transfer (CT) band in the absorption spectrum of PNA in water (∼3.5 eV) is in good agreement with experimental data (3.3 eV). We have investigated the specific role played by local hydrogen bonding and electrostatic interactions on the electronic absorption spectrum. It is shown that although electrostatic interactions play a major role for explaining the structure of the PNA CT band in water, the theoretical prediction of the observed red shift is improved by the explicit consideration of local hydrogen bonding of PNA to water. For isolated PNA, we predict that the dipole moment of the second excited state (S2) is 9.6 D greater than ground state (S0) dipole, which is in good agreement with experimental information (8.2-9.3 D). Calculation of charge transfer indexes for the two first excitations of PNA in water indicates that despite the feature that a small fraction of S1 states (<5%) may exhibit some CT character, CT states in solution are mainly associated with S2 ← S0 transitions.

Molecular dynamics study of polysaccharides in binary solvent mixtures of an ionic liquid and water.

PubMed

Liu, Hanbin; Sale, Kenneth L; Simmons, Blake A; Singh, Seema

2011-09-01

Some ionic liquids (ILs) have great promise as effective solvents for biomass pretreatment, and there are several that have been reported that can dissolve large amounts of cellulose. The solubilized cellulose can then be recovered by addition of antisolvents, such as water or ethanol, and this regeneration process plays an important role in the subsequent enzymatic saccharification reactions and in the recovery of the ionic liquid. To date, little is known about the fundamental intermolecular interactions that drive the dissolution and subsequent regeneration of cellulose in complex mixtures of ionic liquids, water, and cellulose. To investigate these interactions, in this work, molecular dynamics (MD) simulations were carried out to study binary and ternary mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) with water and a cellulose oligomer. Simulations of a cellulose oligomer dissolved in three concentrations of binary mixtures of [C2mim][OAc] and water were used to represent the ternary system in the dissolution phase (high [C2mim][OAc] concentration) and present during the initial phase of the regeneration step (intermediate and low [C2mim][OAc] concentrations). The MD analysis of the structure and dynamics that exist in these binary and ternary mixtures provides information on the key intermolecular interactions between cellulose and [C2mim][OAc] that lead to dissolution of cellulose and the key intermolecular interactions in the intermediate states of cellulose precipitation as a function of water content in the cellulose/IL/water system. The analysis of this intermediate state provides new insight into the molecular driving forces present in this ternary system. © 2011 American Chemical Society

Vacuum ultraviolet spectroscopy of the lowest-lying electronic state in subcritical and supercritical water

NASA Astrophysics Data System (ADS)

Marin, Timothy W.; Janik, Ireneusz; Bartels, David M.; Chipman, Daniel M.

2017-05-01

The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381 °C gives insight into the extent of hydrogen bonding in supercritical water. The known gas-phase spectrum, including its vibronic structure, is duplicated in the low-density limit. With increasing density, the spectrum blueshifts and the vibronic structure is quenched as the water monomer becomes electronically perturbed. Fits to the supercritical water spectra demonstrate consistency with dimer/trimer fractions calculated from the water virial equation of state and equilibrium constants. Using the known water dimer interaction potential, we estimate the critical distance between molecules (ca. 4.5 Å) needed to explain the vibronic structure quenching.

Vacuum ultraviolet spectroscopy of the lowest-lying electronic state in subcritical and supercritical water

DOE PAGES

Marin, Timothy W.; Janik, Ireneusz; Bartels, David M.; ...

2017-05-17

The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381°C gives insight into the extent of hydrogen bonding in supercritical water. The known gas-phase spectrum, including its vibronic structure, is duplicated in the low-density limit. With increasing density, the spectrum blueshifts and the vibronic structure is quenched as themore » water monomer becomes electronically perturbed. Fits to the supercritical water spectra demonstrate consistency with dimer/trimer fractions calculated from the water virial equation of state and equilibrium constants. As a result, using the known water dimer interaction potential, we estimate the critical distance between molecules (ca. 4.5 Å) needed to explain the vibronic structure quenching.« less

Surface force and vibrational spectroscopic analyses of interfacial water molecules in the vicinity of methoxy-tri(ethylene glycol)-terminated monolayers: mechanisms underlying the effect of lateral packing density on bioinertness.

PubMed

Sekine, Taito; Asatyas, Syifa; Sato, Chikako; Morita, Shigeaki; Tanaka, Masaru; Hayashi, Tomohiro

Unequivocal dependence of bioinertness of self-assembled monolayers of methoxy-tri(ethylene glycol)-terminated alkanethiol (EG3-OMe SAMs) on their packing density has been a mystery for more than two decades. We tackled this long-standing question by performing surface force and surface-enhanced infrared absorption (SEIRA) spectroscopic measurements. Our surface force measurements revealed a physical barrier of interfacial water in the vicinity of the Au-supported EG3-OMe SAM (low packing density), whereas the Ag-supported one (high packing density) did not possess such interfacial water. In addition, the results of SEIRA measurements clearly exhibited that hydrogen bonding states of the interfacial water differ depending on the substrates. We also characterized the bioinertness of these SAMs by protein adsorption tests and adhesion assays of platelet and human umbilical vein endothelial cells. The hydrogen bonding states of the interfacial water and water-induced interaction clearly correlated with the bioinertness of the SAMs, suggesting that the interfacial water plays an important role determining the interaction of the SAMs with biomolecules and cells.

Corresponding-states behavior of SPC/E-based modified (bent and hybrid) water models

NASA Astrophysics Data System (ADS)

Weiss, Volker C.

2017-02-01

The remarkable and sometimes anomalous properties of water can be traced back at the molecular level to the tetrahedral coordination of molecules due to the ability of a water molecule to form four hydrogen bonds to its neighbors; this feature allows for the formation of a network that greatly influences the thermodynamic behavior. Computer simulations are becoming increasingly important for our understanding of water. Molecular models of water, such as SPC/E, are needed for this purpose, and they have proved to capture many important features of real water. Modifications of the SPC/E model have been proposed, some changing the H-O-H angle (bent models) and others increasing the importance of dispersion interactions (hybrid models), to study the structural features that set water apart from other polar fluids and from simple fluids such as argon. Here, we focus on the properties at liquid-vapor equilibrium and study the coexistence curve, the interfacial tension, and the vapor pressure in a corresponding-states approach. In particular, we calculate Guggenheim's ratio for the reduced apparent enthalpy of vaporization and Guldberg's ratio for the reduced normal boiling point. This analysis offers additional insight from a more macroscopic, thermodynamic perspective and augments that which has already been learned at the molecular level from simulations. In the hybrid models, the relative importance of dispersion interactions is increased, which turns the modified water into a Lennard-Jones-like fluid. Consequently, in a corresponding-states framework, the typical behavior of simple fluids, such as argon, is seen to be approached asymptotically. For the bent models, decreasing the bond angle turns the model essentially into a polar diatomic fluid in which the particles form linear molecular arrangements; as a consequence, characteristic features of the corresponding-states behavior of hydrogen halides emerge.

Role of air-water interfaces in colloid transport in porous media: A review

NASA Astrophysics Data System (ADS)

Flury, Markus; Aramrak, Surachet

2017-07-01

Air-water interfaces play an important role in unsaturated porous media, giving rise to phenomena like capillarity. Less recognized and understood are interactions of colloids with the air-water interface in porous media and the implications of these interactions for fate and transport of colloids. In this review, we discuss how colloids, both suspended in the aqueous phase and attached at pore walls, interact with air-water interfaces in porous media. We discuss the theory of colloid/air-water interface interactions, based on the different forces acting between colloids and the air-water interface (DLVO, hydrophobic, capillary forces) and based on thermodynamic considerations (Gibbs free energy). Subsurface colloids are usually electrostatically repelled from the air-water interface because most subsurface colloids and the air-water are negatively charged. However, hydrophobic interactions can lead to attraction to the air-water interface. When colloids are at the air-water interface, capillary forces are usually dominant over other forces. Moving air-water interfaces are effective in mobilizing and transporting colloids from surfaces. Thermodynamic considerations show that, for a colloid, the air-water interface is the favored state as compared with the suspension phase, except for hydrophilic colloids in the nanometer size range. Experimental evidence indicates that colloid mobilization in soils often occurs through macropores, although matrix transport is also prevalent in absence of macropores. Moving air-water interfaces, e.g., occurring during infiltration, imbibition, or drainage, have been shown to scour colloids from surfaces and translocate colloids. Colloids can also be pinned to surfaces by thin water films and capillary menisci at the air-water-solid interface line, causing colloid retention and immobilization. Air-water interfaces thus can both mobilize or immobilize colloids in porous media, depending on hydrodynamics and colloid and surface chemistry.

Sensitivity of future U.S. water shortages to socioeconomic and climate drivers: A case study in Georgia using an integrated human-earth system modeling framework

DOE PAGES

Scott, Michael J.; Daly, Don S.; Hejazi, Mohamad I.; ...

2016-02-06

Here, one of the most important interactions between humans and climate is in the demand and supply of water. Humans withdraw, use, and consume water and return waste water to the environment for a variety of socioeconomic purposes, including domestic, commercial, and industrial use, production of energy resources and cooling thermal-electric power plants, and growing food, fiber, and chemical feed stocks for human consumption. Uncertainties in the future human demand for water interact with future impacts of climatic change on water supplies to impinge on water management decisions at the international, national, regional, and local level, but until recently toolsmore » were not available to assess the uncertainties surrounding these decisions. This paper demonstrates the use of a multi-model framework in a structured sensitivity analysis to project and quantify the sensitivity of future deficits in surface water in the context of climate and socioeconomic change for all U.S. states and sub-basins. The framework treats all sources of water demand and supply consistently from the world to local level. The paper illustrates the capabilities of the framework with sample results for a river sub-basin in the U.S. state of Georgia.« less

METHYL TERT-BUTYLETHER-WATER INTERACTION

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is a well-known environmental contaminant owing to its high solubility in water. Since the early 1990s, MTBE has been added to gasoline to improve air quality in some metropolitan areas of the United States. Improved air quality was, however, achiev...

Recrystallization of water in non-water-soluble (meth)acrylate polymers is not rare and is not devitrification.

PubMed

Gemmei-Ide, Makoto; Ohya, Atsushi; Kitano, Hiromi

2012-02-16

Change in the state of water sorbed into four kinds of non-water-soluble poly(meth)acrylates with low water content by temperature (T) perturbation was examined on the basis of T variable mid-infrared (MIR) spectroscopy. Many studies using differential scanning calorimetry suggested that there was no change in the state. T dependence of their MIR spectra, however, clearly demonstrated various changes in the state. Furthermore, recrystallization, which was crystallization during heating, was observed in all four polymers. The recrystallization observed in this study was not devitrification, which is the change in the state from glassy water to crystalline water, but vapor deposition during heating (vapor re-deposition). There were only two reports about recrystallization of water in a non-water-soluble polymer before this report; therefore, it might be considered to be a rare phenomenon. However, as demonstrated in this study, it is not a rare phenomenon. Recrystallization (vapor re-deposition) of water in the polymer matrices is related to a balance between flexibility and strength of the electrostatic interaction sites of polymer matrices but might not be related to the biocompatibility of polymers.

Conformational behavior of phenylglycines and hydroxyphenylglycines and non-planarity of phenyl rings.

PubMed

Nandel, Fateh S; Shafique, Mohd

2014-10-01

The non-proteinogenic amino acids--phenylglycine (PG) and hydroxyphenylglycine (HPG) are crucial components of certain peptidic natural products and are important for the preparation of various medicines. In this, study, the conformation of model dipeptides Ac-X-NHMe of PG, p-HPG and 3, 5-di-hydroxyphenylglycine (3, 5-DHPG) was studied both in R and S form by quantum mechanical (QM) and molecular dynamics approaches. On the energy scale, the conformational states of these molecules in both the R and S were found to be degenerate by QM studies, stabilized by non-covalent interactions like carbonyl--carbonyl interactions, carbonyl-lp .. π (aromatic ring) interactions etc. These interactions disappeared/weakened due to interaction of water molecules with carbonyl groups of backbone in simulation and water was found to interact with the aromatic ring through O(w)-H .. π or O(w)lp .. π interactions. The degeneracy of conformational states was lifted in favor of R-form of PG and DHPG and water molecules interactions with aromatic ring led to non-planarity of the aromatic ring. In simulation studies, irrespective of the starting geometry, the Φ, ψ values for the R form correspond to inverse β/inverse collagen region and for the S-form, the Φ, ψ values correspond to β/collagen region i.e., adopt single conformation. The obtained results were in conformity with the CD spectroscopic data on D-PG and D-p-HPG. The conformational behavior of the unusual amino acids might be of great help in designing of bioactive peptides/peptide based drugs to be realized in single conformation--an essential requirement.

Negotiating water across levels: A peace and conflict "Toolbox" for water diplomacy

NASA Astrophysics Data System (ADS)

Grech-Madin, Charlotte; Döring, Stefan; Kim, Kyungmee; Swain, Ashok

2018-04-01

As a key policy tool, water diplomacy offers greater political engagement in the cooperative management of shared water. A range of initiatives has been dedicated to this end, almost invariably oriented around the interactions of nation states. Crucially, however, practitioners of water diplomacy also need to address water governance at sub-state levels. As a political, multi-level, and normative field, peace and conflict research offers a pluralism of approaches designed to bring actors together at all levels. Drawing upon this research, this paper offers new focal points for water diplomacy that can enhance its policy effectiveness and enrich its underlying academic current. More specifically, it presents three hitherto undervalued tools for water diplomacy: at the interstate level, to uncover the rich body of political norms that bind states to shared understandings of acceptable practice around water. At the intrastate level, to incorporate ethnography of water users and civil society groups' responses to state-led waterworks projects, and at the communal level to employ disaggregated georeferenced data on water resources in conflict-prone areas. Taken together, these analytical tools provide a multi-faceted political gauge of the dynamics of water diplomacy, and add vital impetus to develop water diplomacy across multiple levels of policy engagement.

Household's willingness to pay for heterogeneous attributes of drinking water quality and services improvement: an application of choice experiment

NASA Astrophysics Data System (ADS)

Dauda, Suleiman Alhaji; Yacob, Mohd Rusli; Radam, Alias

2015-09-01

The service of providing good quality of drinking water can greatly improve the lives of the community and maintain a normal health standard. For a large number of population in the world, specifically in the developing countries, the availability of safe water for daily sustenance is none. Damaturu is the capital of Yobe State, Nigeria. It hosts a population of more than two hundred thousand, yet only 45 % of the households are connected to the network of Yobe State Water Corporation's pipe borne water services; this has led people to source for water from any available source and thus, exposed them to the danger of contracting waterborne diseases. In order to address the problem, Yobe State Government has embarked on the construction of a water treatment plant with a capacity and facility to improve the water quality and connect the town with water services network. The objectives of this study are to assess the households' demand preferences of the heterogeneous water attributes in Damaturu, and to estimate their marginal willingness to pay, using mixed logit model in comparison with conditional logit model. A survey of 300 households randomly sampled indicated that higher education greatly influenced the households' WTP decisions. The most significant variable from both of the models is TWQ, which is MRS that rates the water quality from the level of satisfactory to very good. 219 % in simple model is CLM, while 126 % is for the interaction model. As for MLM, 685 % is for the simple model and 572 % is for the interaction model. Estimate of MLM has more explanatory powers than CLM. Essentially, this finding can help the government in designing cost-effective management and efficient tariff structure.

A Study of Drop-Microstructured Surface Interactions during Dropwise Condensation with Quartz Crystal Microbalance

PubMed Central

Su, Junwei; Charmchi, Majid; Sun, Hongwei

2016-01-01

Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of aerodynamic surfaces, to list a few. The direct dynamic characterization of liquid/solid interaction can significantly accelerate the progress toward a full understanding of the thermal and mass transport mechanisms during DWC processes. This work reports a novel Quartz Crystal Microbalance (QCM) based method that can quantitatively analyze the interaction between water droplets and micropillar surfaces during different condensation states such as filmwise, Wenzel, and partial Cassie states. A combined nanoimprinting lithography and chemical surface treatment approach was utilized to fabricate the micropillar based superhydrophobic and superhydrophilic surfaces on the QCM substrates. The normalized frequency shift of the QCM device together with the microscopic observation of the corresponding drop motion revealed the droplets growth and their coalescence processes and clearly demonstrated the differences between the three aforementioned condensation states. In addition, the transition between Cassie and Wenzel states was successfully captured by this method. The newly developed QCM system provides a valuable tool for the dynamic characterization of different condensation processes. PMID:27739452

Size matters in the water uptake and hygroscopic growth of atmospherically relevant multicomponent aerosol particles.

PubMed

Laskina, Olga; Morris, Holly S; Grandquist, Joshua R; Qin, Zhen; Stone, Elizabeth A; Tivanski, Alexei V; Grassian, Vicki H

2015-05-14

Understanding the interactions of water with atmospheric aerosols is crucial for determining the size, physical state, reactivity, and climate impacts of this important component of the Earth's atmosphere. Here we show that water uptake and hygroscopic growth of multicomponent, atmospherically relevant particles can be size dependent when comparing 100 nm versus ca. 6 μm sized particles. It was determined that particles composed of ammonium sulfate with succinic acid and of a mixture of chlorides typical of the marine environment show size-dependent hygroscopic behavior. Microscopic analysis of the distribution of components within the aerosol particles show that the size dependence is due to differences in the mixing state, that is, whether particles are homogeneously mixed or phase separated, for different sized particles. This morphology-dependent hygroscopicity has consequences for heterogeneous atmospheric chemistry as well as aerosol interactions with electromagnetic radiation and clouds.

30 CFR 256.5 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., conditions, and quality of the marine ecosystem, including the waters of the high seas, the contiguous zone..., conditions, and factors which interactively determine the productivity, state, conditions, and quality of the... determine the state, condition, and quality of living conditions, employment, and health of those affected...

30 CFR 256.5 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... productivity, state, conditions, and quality of the marine ecosystem, including the waters of the high seas..., conditions, and quality of the terrestrial ecosystem from the shoreline inward to the boundaries of the... factors which interactively determine the state, condition, and quality of living conditions, employment...

Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

DOE PAGES

Zarzycki, Piotr; Gilbert, Benjamin

2016-04-27

Water diffusion within smectite clay interlayers is reduced by confinement and hence is highly determined by the interlayer spacings that are adopted during swelling. However, a molecular understanding of the short-and long-range forces governing interlayer water structure and dynamics is lacking. Using molecular dynamics simulations of water intercalated between pyrophyllite (smectite prototype) layers we provide a detailed picture of the variation of interlayered water mobility accompanying smectite expansion. Subtle changes in hydrogen bond network structure cause significant changes in water mobility that is greater for stable hydration states and reduced for intermediate separations. By studying pyrophyllite with and without externalmore » water we reveal that long-range electrostatic forces apply a restraining effect upon interlayer water mobility. Our findings are relevant for broad range of confining nanostructures with walls thin enough to permit long-range interactions that could affect the mobility of confined solvent molecules and solute species.« less

Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

PubMed Central

Zarzycki, Piotr; Gilbert, Benjamin

2016-01-01

Water diffusion within smectite clay interlayers is reduced by confinement and hence is highly determined by the interlayer spacings that are adopted during swelling. However, a molecular understanding of the short- and long-range forces governing interlayer water structure and dynamics is lacking. Using molecular dynamics simulations of water intercalated between pyrophyllite (smectite prototype) layers we provide a detailed picture of the variation of interlayered water mobility accompanying smectite expansion. Subtle changes in hydrogen bond network structure cause significant changes in water mobility that is greater for stable hydration states and reduced for intermediate separations. By studying pyrophyllite with and without external water we reveal that long-range electrostatic forces apply a restraining effect upon interlayer water mobility. Our findings are relevant for broad range of confining nanostructures with walls thin enough to permit long-range interactions that could affect the mobility of confined solvent molecules and solute species. PMID:27118164

Role of soil texture on mesquite water relations and response to summer precipitation

Treesearch

Alessandra Fravolini; Kevin R. Hultine; Dan F. Koepke; David G. Williams

2003-01-01

In the arid Southwest United States, monsoon precipitation plays a key role in ecosystem water balance and productivity. The sensitivity of deeply rooted plants to pulses of summer precipitation is, in part, controlled by the interaction between soil texture, precipitation intensity, and plant rooting depth and activity. In this study we evaluated the water relations...

Waterlike glass polyamorphism in a monoatomic isotropic Jagla model.

PubMed

Xu, Limei; Giovambattista, Nicolas; Buldyrev, Sergey V; Debenedetti, Pablo G; Stanley, H Eugene

2011-02-14

We perform discrete-event molecular dynamics simulations of a system of particles interacting with a spherically-symmetric (isotropic) two-scale Jagla pair potential characterized by a hard inner core, a linear repulsion at intermediate separations, and a weak attractive interaction at larger separations. This model system has been extensively studied due to its ability to reproduce many thermodynamic, dynamic, and structural anomalies of liquid water. The model is also interesting because: (i) it is very simple, being composed of isotropically interacting particles, (ii) it exhibits polyamorphism in the liquid phase, and (iii) its slow crystallization kinetics facilitate the study of glassy states. There is interest in the degree to which the known polyamorphism in glassy water may have parallels in liquid water. Motivated by parallels between the properties of the Jagla potential and those of water in the liquid state, we study the metastable phase diagram in the glass state. Specifically, we perform the computational analog of the protocols followed in the experimental studies of glassy water. We find that the Jagla potential calculations reproduce three key experimental features of glassy water: (i) the crystal-to-high-density amorphous solid (HDA) transformation upon isothermal compression, (ii) the low-density amorphous solid (LDA)-to-HDA transformation upon isothermal compression, and (iii) the HDA-to-very-high-density amorphous solid (VHDA) transformation upon isobaric annealing at high pressure. In addition, the HDA-to-LDA transformation upon isobaric heating, observed in water experiments, can only be reproduced in the Jagla model if a free surface is introduced in the simulation box. The HDA configurations obtained in cases (i) and (ii) are structurally indistinguishable, suggesting that both processes result in the same glass. With the present parametrization, the evolution of density with pressure or temperature is remarkably similar to the corresponding experimental measurements on water. Our simulations also suggest that the Jagla potential may reproduce features of the HDA-VHDA transformations observed in glassy water upon compression and decompression. Snapshots of the system during the HDA-VHDA and HDA-LDA transformations reveal a clear segregation between LDA and HDA but not between HDA and VHDA, consistent with the possibility that LDA and HDA are separated by a first order transformation as found experimentally, whereas HDA and VHDA are not. Our results demonstrate that a system of particles with simple isotropic pair interactions, a Jagla potential with two characteristic length scales, can present polyamorphism in the glass state as well as reproducing many of the distinguishing properties of liquid water. While most isotropic pair potential models crystallize readily on simulation time scales at the low temperatures investigated here, the Jagla potential is an exception, and is therefore a promising model system for the study of glass phenomenology.

Development of a water-use data system in Minnesota

USGS Publications Warehouse

Horn, M.A.

1986-01-01

The Minnesota Water-Use Data System stores data on the quantity of individual annual water withdrawals and discharges in relation to the water resources affected, provides descriptors for aggregation of data and trend analysis, and enables access to additional data contained in other data bases. MWUDS is stored on a computer at the Land Management Information Center, an agency associated with the State Planning Agency. Interactive menu-driven programs simplify data entry, update, and retrieval and are easy to use. Estimates of unreported water use supplement reported water use to completely describe the stress on the hydrologic system. Links or common elements developed in the MWUDS enable access to data available in other State waterrelated data bases, forming a water-resource information system. Water-use information can be improved by developing methods for increasing accuracy of reported water use and refining methods for estimating unreported water use.

Interaction of surface water and groundwater in the Nile River basin: isotopic and piezometric evidence

NASA Astrophysics Data System (ADS)

Kebede, Seifu; Abdalla, Osman; Sefelnasr, Ahmed; Tindimugaya, Callist; Mustafa, Osman

2017-05-01

Past discussions around water-resources management and development in the River Nile basin disregard groundwater resources from the equation. There is an increasing interest around factoring the groundwater resources as an integral part of the Nile Basin water resources. This is hampered by knowledge gap regarding the groundwater resources dynamics (recharge, storage, flow, quality, surface-water/groundwater interaction) at basin scale. This report provides a comprehensive analysis of the state of surface-water/groundwater interaction from the headwater to the Nile Delta region. Piezometric and isotopic (δ18O, δ2H) evidence reveal that the Nile changes from a gaining stream in the headwater regions to mostly a loosing stream in the arid lowlands of Sudan and Egypt. Specific zones of Nile water leakage to the adjacent aquifers is mapped using the two sources of evidence. Up to 50% of the surface-water flow in the equatorial region of the Nile comes from groundwater as base flow. The evidence also shows that the natural direction and rate of surface-water/groundwater interaction is largely perturbed by human activities (diversion, dam construction) particularly downstream of the Aswan High Dam in Egypt. The decrease in discharge of the Nile River along its course is attributed to leakage to the aquifers as well as to evaporative water loss from the river channel. The surface-water/groundwater interaction occurring along the Nile River and its sensitivity to infrastructure development calls for management strategies that account groundwater as an integral part of the Nile Basin resources.

Sele coastal plain flood risk due to wave storm and river flow interaction

NASA Astrophysics Data System (ADS)

Benassai, Guido; Aucelli, Pietro; Di Paola, Gianluigi; Della Morte, Renata; Cozzolino, Luca; Rizzo, Angela

2016-04-01

Wind waves, elevated water levels and river discharge can cause flooding in low-lying coastal areas, where the water level is the interaction between wave storm elevated water levels and river flow interaction. The factors driving the potential flood risk include weather conditions, river water stage and storm surge. These data are required to obtain inputs to run the hydrological model used to evaluate the water surface level during ordinary and extreme events regarding both the fluvial overflow and storm surge at the river mouth. In this paper we studied the interaction between the sea level variation and the river hydraulics in order to assess the location of the river floods in the Sele coastal plain. The wave data were acquired from the wave buoy of Ponza, while the water level data needed to assess the sea level variation were recorded by the tide gauge of Salerno. The water stages, river discharges and rating curves for Sele river were provided by Italian Hydrographic Service (Servizio Idrografico e Mareografico Nazionale, SIMN).We used the dataset of Albanella station (40°29'34.30"N, 15°00'44.30"E), located around 7 km from the river mouth. The extreme river discharges were evaluated through the Weibull equation, which were associated with their return period (TR). The steady state river water levels were evaluated through HEC-RAS 4.0 model, developed by Hydrologic Engineering Center (HEC) of the United States Army Corps of Engineers Hydrologic Engineering Center (USACE,2006). It is a well-known 1D model that computes water surface elevation (WSE) and velocity at discrete cross-sections by solving continuity, energy and flow resistance (e.g., Manning) equation. Data requirements for HEC-RAS include topographic information in the form of a series of cross-sections, friction parameter in the form of Manning's n values across each cross-section, and flow data including flow rates, flow change locations, and boundary conditions. For a steady state sub-critical simulation, the boundary condition is a known downstream WSE, in this case the elevated water level due to wave setup, wind setup and inverted barometer, while the upstream boundary condition consisted in WSE corresponding to river discharges associated to different return periods. The results of the simulations evidence, for the last 10 kilometers of the river, the burst of critical inundation scenarios even with moderate flow discharge, if associated with concurrent storm surge which increase the water level at the river mouth, obstructing normal flow discharge.

Make a Splash Day

ERIC Educational Resources Information Center

Coverdale, Greg; Rust, April; Jensen, Belinda

2004-01-01

At the annual, all-day events-sponsored by Project WET (Water Education for Teachers) and held in nearly every state across the country each September--students participate in interactive activities and exhibits to learn about water resources and explore how human behaviors, such as development and recreation, can affect the quality of the…

Measurement of the adsorption energy difference between ortho- and para-D2 on an amorphous ice surface.

PubMed

Amiaud, L; Momeni, A; Dulieu, F; Fillion, J H; Matar, E; Lemaire, J-L

2008-02-08

Molecular hydrogen interaction on water ice surfaces is a major process taking place in interstellar dense clouds. By coupling laser detection and classical thermal desorption spectroscopy, it is possible to study the effect of rotation of D(2) on adsorption on amorphous solid water ice surfaces. The desorption profiles of ortho- and para-D(2) are different. This difference is due to a shift in the adsorption energy distribution of the two lowest rotational states. Molecules in J''=1 rotational state are on average more strongly bound to the ice surface than those in J''=0 rotational state. This energy difference is estimated to be 1.4+/-0.3 meV. This value is in agreement with previous calculation and interpretation. The nonspherical wave function J'' =1 has an interaction with the asymmetric part of the adsorption potential and contributes positively in the binding energy.

Physicochemical basis for water-actuated movement and stress generation in nonliving plant tissues.

PubMed

Bertinetti, L; Fischer, F D; Fratzl, P

2013-12-06

Generating stresses and strains through water uptake from atmospheric humidity is a common process in nature, e.g., in seed dispersal. Actuation depends on a balance between chemical interactions and the elastic energy required to accomplish the volume change. In order to study the poorly understood chemical interactions, we combine mechanosorption experiments with theoretical calculations of the swelling behavior to estimate the mechanical energy and extract the contribution of the chemical energy per absorbed water molecule. The latter is highest in the completely dry state and stays almost constant at about 1.2 kT for higher hydrations. This suggests that water bound to the macromolecular components of the wood tissues acquires one additional hydrogen bond per eight water molecules, thus providing energy for actuation.

On the transition towards slow manifold in shallow-water and 3D Euler equations in a rotating frame

NASA Technical Reports Server (NTRS)

Mahalov, A.

1994-01-01

The long-time, asymptotic state of rotating homogeneous shallow-water equations is investigated. Our analysis is based on long-time averaged rotating shallow-water equations describing interactions of large-scale, horizontal, two-dimensional motions with surface inertial-gravity waves field for a shallow, uniformly rotating fluid layer. These equations are obtained in two steps: first by introducing a Poincare/Kelvin linear propagator directly into classical shallow-water equations, then by averaging. The averaged equations describe interaction of wave fields with large-scale motions on time scales long compared to the time scale 1/f(sub o) introduced by rotation (f(sub o)/2-angular velocity of background rotation). The present analysis is similar to the one presented by Waleffe (1991) for 3D Euler equations in a rotating frame. However, since three-wave interactions in rotating shallow-water equations are forbidden, the final equations describing the asymptotic state are simplified considerably. Special emphasis is given to a new conservation law found in the asymptotic state and decoupling of the dynamics of the divergence free part of the velocity field. The possible rising of a decoupled dynamics in the asymptotic state is also investigated for homogeneous turbulence subjected to a background rotation. In our analysis we use long-time expansion, where the velocity field is decomposed into the 'slow manifold' part (the manifold which is unaffected by the linear 'rapid' effects of rotation or the inertial waves) and a formal 3D disturbance. We derive the physical space version of the long-time averaged equations and consider an invariant, basis-free derivation. This formulation can be used to generalize Waleffe's (1991) helical decomposition to viscous inhomogeneous flows (e.g. problems in cylindrical geometry with no-slip boundary conditions on the cylinder surface and homogeneous in the vertical direction).

LANDSAT supports data needs for EPA 208 planning. [water quality control and waste treatment management

NASA Technical Reports Server (NTRS)

1979-01-01

Excerpts from federal legislation and regulations mandating areawide waster treatment management as a means of restoring and maintaining the integrity of the nation's water are presented along with requirements for grants to the states for water quality planning, management, and implementation. Experiences using LANDSAT to identify nonpoint sources of water pollution as well as land/use/land cover features in South Dakota, Kentucky, Georgia, New Jersey, and Texas are described. Present activities suggest that this type of remote sensing is an efficient, effective tool for areawide water quality planning. Interaction with cognizant federal, state, and local government personnel involved in EPA section 208 planning activities can guide the development of new capabilities and enhance their utility and prospect for use.

Recent experimental advances on hydrophobic interactions at solid/water and fluid/water interfaces.

PubMed

Zeng, Hongbo; Shi, Chen; Huang, Jun; Li, Lin; Liu, Guangyi; Zhong, Hong

2015-03-15

Hydrophobic effects play important roles in a wide range of natural phenomena and engineering processes such as coalescence of oil droplets in water, air flotation of mineral particles, and folding and assembly of proteins and biomembranes. In this work, the authors highlight recent experimental attempts to reveal the physical origin of hydrophobic effects by directly quantifying the hydrophobic interaction on both solid/water and fluid/water interfaces using state-of-art nanomechanical techniques such as surface forces apparatus and atomic force microscopy (AFM). For solid hydrophobic surfaces of different hydrophobicity, the range of hydrophobic interaction was reported to vary from ∼10 to >100 nm. With various characterization techniques, the very long-ranged attraction (>100 nm) has been demonstrated to be mainly attributed to nonhydrophobic interaction mechanisms such as pre-existing nanobubbles and molecular rearrangement. By ruling out these factors, intrinsic hydrophobic interaction was measured to follow an exponential law with decay length of 1-2 nm with effective range less than 20 nm. On the other hand, hydrophobic interaction measured at fluid interfaces using AFM droplet/bubble probe technique was found to decay with a much shorter length of ∼0.3 nm. This discrepancy of measured decay lengths is proposed to be attributed to inherent physical distinction between solid and fluid interfaces, which impacts the structure of interface-adjacent water molecules. Direct measurement of hydrophobic interaction on a broader range of interfaces and characterization of interfacial water molecular structure using spectroscopic techniques are anticipated to help unravel the origin of this rigidity-related mismatch of hydrophobic interaction and hold promise to uncover the physical nature of hydrophobic effects. With improved understanding of hydrophobic interaction, intrinsic interaction mechanisms of many biological and chemical pathways can be better elucidated, and novel devices/processes can be developed with capacity to modulate and control the hydrophobic effects from the molecular to the macroscopic scale.

Understanding and managing the effects of groundwater pumping on streamflow

USGS Publications Warehouse

Leake, Stanley A.; Barlow, Paul M.

2013-01-01

Groundwater is a critical resource in the United States because it provides drinking water, irrigates crops, supports industry, and is a source of water for rivers, streams, lakes, and springs. Wells that pump water out of aquifers can reduce the amount of groundwater that flows into rivers and streams, which can have detrimental impacts on aquatic ecosystems and the availability of surface water. Estimation of rates, locations, and timing of streamflow depletion due to groundwater pumping is needed for water-resource managers and users throughout the United States, but the complexity of groundwater and surface-water systems and their interactions presents a major challenge. The understanding of streamflow depletion and evaluation of water-management practices have improved during recent years through the use of computer models that simulate aquifer conditions and the effects of pumping groundwater on streams.

Deprotonation states of the two active site water molecules regulate the binding of protein phosphatase 5 with its substrate: A molecular dynamics study.

PubMed

Wang, Lingyun; Yan, Feng

2017-10-01

Protein phosphatase 5 (PP5), mainly localized in human brain, can dephosphorylate tau protein whose high level of phosphorylation is related to Alzheimer's disease. Similar to other protein phosphatases, PP5 has a conserved motif in the catalytic domain that contains two binding sites for manganese (Mn 2+ ) ions. Structural data indicate that two active site water molecules, one bridging the two Mn 2+ ions and the other terminally coordinated with one of the Mn 2+ ions (Mn1), are involved in catalysis. Recently, a density functional theory study revealed that the two water molecules can be both deprotonated to keep a neutral active site for catalysis. The theoretical study gives us an insight into the catalytic mechanism of PP5, but the knowledge of how the deprotonation states of the two water molecules affect the binding of PP5 with its substrate is still lacking. To approach this problem, molecular dynamics simulations were performed to model the four possible deprotonation states. Through structural, dynamical and energetic analyses, the results demonstrate that the deprotonation states of the two water molecules affect the structure of the active site including the distance between the two Mn 2+ ions and their coordination, impact the interaction energy of residues R275, R400 and H304 which directly interact with the substrate phosphoserine, and mediate the dynamics of helix αJ which is involved in regulation of the enzyme's activity. Furthermore, the deprotonation state that is preferable for PP5 binding of its substrate has been identified. These findings could provide new design strategy for PP5 inhibitor. © 2017 The Protein Society.

Density-Difference-Driven Optimized Embedding Potential Method To Study the Spectroscopy of Br₂ in Water Clusters.

PubMed

Roncero, Octavio; Aguado, Alfredo; Batista-Romero, Fidel A; Bernal-Uruchurtu, Margarita I; Hernández-Lamoneda, Ramón

2015-03-10

A variant of the density difference driven optimized embedding potential (DDD-OEP) method, proposed by Roncero et al. (J. Chem. Phys. 2009, 131, 234110), has been applied to the calculation of excited states of Br2 within small water clusters. It is found that the strong interaction of Br2 with the lone electronic pair of the water molecules makes necessary to optimize specific embedding potentials for ground and excited electronic states, separately and using the corresponding densities. Diagnosis and convergence studies are presented with the aim of providing methods to be applied for the study of chromophores in solution. Also, some preliminary results obtained for the study of electronic states of Br2 in clathrate cages are presented.

Illuminating water and life: Emilio Del Giudice.

PubMed

Ho, Mae-Wan

2015-01-01

The quantum electrodynamics theory of water put forward by Del Giudice and colleagues provides a useful foundation for a new science of water for life. The interaction of light with liquid water generates quantum coherent domains in which the water molecules oscillate between the ground state and an excited state close to the ionizing potential of water. This produces a plasma of almost free electrons favoring redox reactions, the basis of energy metabolism in living organisms. Coherent domains stabilized by surfaces, such as membranes and macromolecules, provide the excited interfacial water that enables photosynthesis to take place, on which most of life on Earth depends. Excited water is the source of superconducting protons for rapid intercommunication within the body. Coherent domains can also trap electromagnetic frequencies from the environment to orchestrate and activate specific biochemical reactions through resonance, a mechanism for the most precise regulation of gene function.

The Role of Water Distribution Controlled by Transmembrane Potentials in the Cytochrome c-Cardiolipin Interaction: Revealing from Surface-Enhanced Infrared Absorption Spectroscopy.

PubMed

Zeng, Li; Wu, Lie; Liu, Li; Jiang, Xiue

2017-11-02

The interaction of cytochrome c (cyt c) with cardiolipin (CL) plays a crucial role in apoptotic functions, however, the changes of the transmembrane potential in governing the protein behavior at the membrane-water interface have not been studied due to the difficulties in simultaneously monitoring the interaction and regulating the electric field. Herein, surface-enhanced infrared absorption (SEIRA) spectroelectrochemistry is employed to study the mechanism of how the transmembrane potentials control the interaction of cyt c with CL membranes by regulating the electrode potentials of an Au film. When the transmembrane potential decreases, the water content at the interface of the membranes can be increased to slow down protein adsorption through decreasing the hydrogen-bond and hydrophobic interactions, but regulates the redox behavior of CL-bound cyt c through a possible water-facilitated proton-coupled electron transfer process. Our results suggest that the potential drop-induced restructure of the CL conformation and the hydration state could modify the structure and function of CL-bound cyt c on the lipid membrane. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interactions of water quality and integrated groundwater management: exampled from the United States

USDA-ARS?s Scientific Manuscript database

Groundwater is available in many parts of the world, but the quality of the water may limit its use. Contaminants can limit the use of groundwater through concerns associated with human health, aquatic health, economic costs, or even societal perception. Given this broad range of concerns, this chap...

User's instructions for the 41-node thermoregulatory model (steady state version)

NASA Technical Reports Server (NTRS)

Leonard, J. I.

1974-01-01

A user's guide for the steady-state thermoregulatory model is presented. The model was modified to provide conversational interaction on a remote terminal, greater flexibility for parameter estimation, increased efficiency of convergence, greater choice of output variable and more realistic equations for respiratory and skin diffusion water losses.

What does the Sr-substituted 2.1 Å resolution crystal structure of photosystem II reveal about the water oxidation mechanism?

PubMed

Terrett, Richard; Petrie, Simon; Pace, Ron J; Stranger, Robert

2014-03-25

A density functional study of the Sr-substituted photosystem II water oxidising complex demonstrates that its recent X-ray crystal structure is consistent with a (Mn(III))4 oxidation state pattern, and with a Sr-bound hydroxide ion. The Sr-water-hydroxide interactions rationalize differences in the exchange rates of substrate water and kinetics of dioxygen bond formation relative to the Ca-containing structure.

Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni 2+ aqua complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunnus, K.; Josefsson, I.; Schreck, S.

We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni 2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L 3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. Here, we propose that 2p3d RIXS at the Ni L 3-edge can be utilized to quantify covalency in Ni complexes without the use of externalmore » references or simulations.« less

Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni 2+ aqua complex

DOE PAGES

Kunnus, K.; Josefsson, I.; Schreck, S.; ...

2016-12-23

We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni 2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L 3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. Here, we propose that 2p3d RIXS at the Ni L 3-edge can be utilized to quantify covalency in Ni complexes without the use of externalmore » references or simulations.« less

Atom-bond electronegativity equalization method fused into molecular mechanics. I. A seven-site fluctuating charge and flexible body water potential function for water clusters.

PubMed

Yang, Zhong-Zhi; Wu, Yang; Zhao, Dong-Xia

2004-02-08

Recently, experimental and theoretical studies on the water system are very active and noticeable. A transferable intermolecular potential seven points approach including fluctuation charges and flexible body (ABEEM-7P) based on a combination of the atom-bond electronegativity equalization and molecular mechanics (ABEEM/MM), and its application to small water clusters are explored and tested in this paper. The consistent combination of ABEEM and molecular mechanics (MM) is to take the ABEEM charges of atoms, bonds, and lone-pair electrons into the intermolecular electrostatic interaction term in molecular mechanics. To examine the charge transfer we have used two models coming from the charge constraint types: one is a charge neutrality constraint on whole water system and the other is on each water molecule. Compared with previous water force fields, the ABEEM-7P model has two characters: (1) the ABEEM-7P model not only presents the electrostatic interaction of atoms, bonds and lone-pair electrons and their changing in respond to different ambient environment but also introduces "the hydrogen bond interaction region" in which a new parameter k(lp,H)(R(lp,H)) is used to describe the electrostatic interaction of the lone-pair electron and the hydrogen atom which can form the hydrogen bond; (2) nonrigid but flexible water body permitting the vibration of the bond length and angle is allowed due to the combination of ABEEM and molecular mechanics, and for van der Waals interaction the ABEEM-7P model takes an all atom-atom interaction, i.e., oxygen-oxygen, hydrogen-hydrogen, oxygen-hydrogen interaction into account. The ABEEM-7P model based on ABEEM/MM gives quite accurate predictions for gas-phase state properties of the small water clusters (H(2)O)(n) (n=2-6), such as optimized geometries, monomer dipole moments, vibrational frequencies, and cluster interaction energies. Due to its explicit description of charges and the hydrogen bond, the ABEEM-7P model will be applied to discuss properties of liquid water, ice, aqueous solutions, and biological systems.

Mathematical modelling of surface water-groundwater flow and salinity interactions in the coastal zone

NASA Astrophysics Data System (ADS)

Spanoudaki, Katerina; Kampanis, Nikolaos A.

2014-05-01

Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. In these numerical models surface water flow is usually described by the 1-D Saint Venant equations (e.g. Swain and Wexler, 1996) or the 2D shallow water equations (e.g. Liang et al., 2007). Further simplified equations, such as the diffusion and kinematic wave approximations to the Saint Venant equations, are also employed for the description of 2D overland flow and 1D stream flow (e.g. Gunduz and Aral, 2005). However, for coastal bays, estuaries and wetlands it is often desirable to solve the 3D shallow water equations to simulate surface water flow. This is the case e.g. for wind-driven flows or density-stratified flows. Furthermore, most integrated models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated surface water-groundwater model IRENE (Spanoudaki et al., 2009; Spanoudaki, 2010) has been modified in order to simulate surface water-groundwater flow and salinity interactions in the coastal zone. IRENE, in its original form, couples the 3D, non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of hydrostatic pressure distribution, to the equations describing 3D saturated groundwater flow of constant density. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection-diffusion equation describing the fate and transport of contaminants introduced in a 3D turbulent flow field to the partial differential equation describing the fate and transport of contaminants in 3D transient groundwater flow systems. The model has been further developed to include the effects of density variations on surface water and groundwater flow, while the already built-in solute transport capabilities are used to simulate salinity interactions. Initial results show that IRENE can accurately predict surface water-groundwater flow and salinity interactions in coastal areas. Important research issues that can be investigated using IRENE include: (a) sea level rise and tidal effects on aquifer salinisation and the configuration of the saltwater wedge, (b) the effects of surface water-groundwater interaction on salinity increase of coastal wetlands and (c) the estimation of the location and magnitude of groundwater discharge to coasts. Acknowledgement The work presented in this paper has been funded by the Greek State Scholarships Foundation (IKY), Fellowships of Excellence for Postdoctoral Studies (Siemens Program), 'A simulation-optimization model for assessing the best practices for the protection of surface water and groundwater in the coastal zone', (2013 - 2015). References Gunduz, O. and Aral, M.M. (2005). River networks and groundwater flow: a simultaneous solution of a coupled system. Journal of Hydrology 301 (1-4), 216-234. Liang, D., Falconer, R.A. and Lin, B. (2007). Coupling surface and subsurface flows in a depth-averaged flood wave model. Journal of Hydrology 337, 147-158. Spanoudaki, K., Stamou, A.I. and Nanou-Giannarou, A. (2009). Development and verification of a 3-D integrated surface water-groundwater model. Journal of Hydrology, 375 (3-4), 410-427. Spanoudaki, K. (2010). Integrated numerical modelling of surface water groundwater systems (in Greek). Ph.D. Thesis, National Technical University of Athens, Greece. Swain, E.D. and Wexler, E.J. (1996). A coupled surface water and groundwater flow model (Modbranch) for simulation of stream-aquifer interaction. United States Geological Survey, Techniques of Water Resources Investigations (Book 6, Chapter A6).

Thermodynamics of water structural reorganization due to geometric confinement

NASA Astrophysics Data System (ADS)

Stroberg, Wylie; Lichter, Seth

2015-03-01

Models of aqueous solvation have successfully quantified the behavior of water near convex bodies. However, many important processes occurring in aqueous solution involve interactions between solutes and surfaces with complicated non-convex geometries. Examples include the folding of proteins, hydrophobic association of solutes, ligand-receptor binding, and water confined within nanotubes and pores. For these geometries, models for solvation of convex bodies fail to account for the added interactions associated with structural confinement. Due to water's propensity to form networks of hydrogen bonds, small alterations to the confining geometry can induce large structural rearrangement within the water. We perform systematic Monte Carlo simulations of water confined to cylindrical cavities of varying aspect ratio to investigate how small geometric changes to the confining geometry may cause large changes to the structure and thermodynamic state of water. Using the Wang-Landau algorithm, we obtain free energies, enthalpies, entropies, and heat capacities across a broad range of temperatures, and show how these quantities are influenced by the structural rearrangement of water molecules due to geometric perturbations.

DRoP: a water analysis program identifies Ras-GTP-specific pathway of communication between membrane-interacting regions and the active site.

PubMed

Kearney, Bradley M; Johnson, Christian W; Roberts, Daniel M; Swartz, Paul; Mattos, Carla

2014-02-06

Ras GTPase mediates several cellular signal transduction pathways and is found mutated in a large number of cancers. It is active in the GTP-bound state, where it interacts with effector proteins, and at rest in the GDP-bound state. The catalytic domain is tethered to the membrane, with which it interacts in a nucleotide-dependent manner. Here we present the program Detection of Related Solvent Positions (DRoP) for crystallographic water analysis on protein surfaces and use it to study Ras. DRoP reads and superimposes multiple Protein Data Bank coordinates, transfers symmetry-related water molecules to the position closest to the protein surface, and ranks the waters according to how well conserved and tightly clustered they are in the set of structures. Coloring according to this rank allows visualization of the results. The effector-binding region of Ras is hydrated with highly conserved water molecules at the interface between the P-loop, switch I, and switch II, as well as at the Raf-RBD binding pocket. Furthermore, we discovered a new conserved water-mediated H-bonding network present in Ras-GTP, but not in Ras-GDP, that links the nucleotide sensor residues R161 and R164 on helix 5 to the active site. The double mutant RasN85A/N86A, where the final link between helix 5 and the nucleotide is not possible, is a severely impaired enzyme, while the single mutant RasN86A, with partial connection to the active site, has a wild-type hydrolysis rate. DRoP was instrumental in determining the water-mediated connectivity networks that link two lobes of the catalytic domain in Ras. Copyright © 2013 Elsevier Ltd. All rights reserved.

Non-Equilibrium Water-Glassy Polymer Dynamics

NASA Astrophysics Data System (ADS)

Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

2012-02-01

For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

CONCEPTUALIZING BIOPOLITICS: CITIZEN-STATE INTERACTIONS IN THE SECURING OF WATER SERVICES IN SOUTH AFRICA

PubMed Central

Bulled, Nicola

2015-01-01

Despite constitutional obligations to provide clean water to all citizens in South Africa, access to water and related services remains highly contested. The discord between constitutional promises and lived realities of water access, particularly through national infrastructure, provides a platform upon which to examine Foucauldian notions of biopolitics, the control of populations through technologies of governing. Drawing on the situations of residents in the rural Vhembe district in the north eastern corner of the country, I examine how individuals conceptualize the relationship that exists between citizen and state and the responsibilities of each in post-apartheid South Africa as it relates to water access. In addition, I describe strategies employed throughout South Africa to voice rights to water and how these approaches are perceived. Finally, I consider how the three primary forms of ‘water citizenship’ – citizen, agent, and subject – influence the current and future health of vulnerable residents. PMID:26087245

Conceptualizing Biopolitics: Citizen-State Interactions in the Securing of Water Services in South Africa.

PubMed

Bulled, Nicola

2015-01-01

Despite constitutional obligations to provide clean water to all citizens in South Africa, access to water and related services remains highly contested. The discord between constitutional promises and lived realities of water access, particularly through national infrastructure, provides a platform on which to examine Foucauldian notions of biopolitics, the control of populations through technologies of governing. Drawing on the situations of residents in the rural Vhembe district in the north eastern corner of the country, I examine how individuals conceptualize the relationship that exists between citizen and state and the responsibilities of each in post-Apartheid South Africa as it relates to water access. In addition, I describe strategies employed throughout South Africa to voice rights to water and how these approaches are perceived. Finally, I consider how the three primary forms of 'water citizenship'-citizen, agent, and subject-influence the current and future health of vulnerable residents.

Characterization of seepage in the exploratory studies facility, Yucca Mountain, Nevada

USGS Publications Warehouse

Oliver, T.A.; Whelan, J.F.

2006-01-01

Following a 5-month period of above-average precipitation during the winter of 2004-2005, water was observed seeping into the South Ramp section of the Exploratory Studies Facility of the proposed repository for high-level radioactive waste at Yucca Mountain, Nevada. Samples of the seepage were collected and analyzed for major ions, trace metals, and delta deuterium and delta oxygen-18 values in an effort to characterize the water and assess the interaction of seepage with anthropogenic materials used in the construction of the proposed repository. As demonstrated by the changes in the chemistry of water dripping from a rock bolt, interaction of seepage with construction materials can alter solution chemistry and oxidation state.

Molecular Theory and Simulation of Water-Oil Contacts

NASA Astrophysics Data System (ADS)

Tan, Liang

The statistical mechanical theory of hydrophobic interactions was initiated decades ago for purely repulsive hydrophobic species, in fact, originally for hard-sphere solutes in liquid water. Systems which treat only repulsive solute-water interactions obviously differ from the real world situation. The issue of the changes to be expected from inclusion of realistic attractive solute-water interactions has been of specific interest also for decades. We consider the local molecular field (LMF) theory for the effects of solute attractive forces on hydrophobic interactions. The principal result of LMF theory is outlined, then tested by obtaining radial distribution functions (rdfs) for Ar atoms in water, with and without attractive interactions distinguished by the Weeks-Chandler-Andersen (WCA) separation. Change from purely repulsive atomic solute interactions to include realistic attractive interactions substantially diminishes the strength of hydrophobic bonds. Since attractions make a big contribution to hydrophobic interactions, Pratt-Chandler theory, which did not include attractions, should not be naively compared to computer simulation results with general physical interactions, including attractions. Lack of general appreciation of this point has lead to mistaken comparisons throughout the history of this subject. The rdfs permit evaluation of osmotic second virial coefficients B2. Those B 2 are consistent with the conclusion that incorporation of attractive interactions leads to more positive (repulsive) values. In all cases here, B2 becomes more attractive with increasing temperature below T = 360K, the so-call inverse temperature behavior. In 2010, the Gulf of Mexico Macondo well (Deepwater Horizon) oil spill focused the attention of the world on water-oil phase equilibrium. In response to the disaster, chemical dispersants were applied to break oil slicks into droplets and thus to avoid large-scale fouling of beaches and to speed up biodegradation. Eventually the dispersant COREXIT 9500 was used predominantly in responding to this accident. The formulation of COREXIT dispersants is somewhat complicated and the various constituents (and their interactions) deserve exhaustive study. Here we focus on sorbitan monooleate (SPAN80), one important component of COREXIT 9500, and we investigate its behavior in oil-water-surfactant systems. Extensive all-atom molecular dynamics calculations on the water-squalane interface for nine different loadings with SPAN80, at T = 300K, are analyzed for the surface tension equation of state, desorption free energy profiles as they depend on loading, and to evaluate escape times for absorbed SPAN80 into the bulk phases. These results suggest that loading only weakly affects accommodation of a SPAN80 molecule by this squalane-water interface. Specifically, the surface tension equation of state is simple from conditions of low loading (high tension) to high loading (lower tension) studied, and the desorption free energy profiles are weakly dependent on loading here. The perpendicular motion of the centroid of the SPAN80 head-group ring is well-described by a diffusional model near the minimum of the desorption free energy profile. Lateral diffusional motion is weakly dependent on loading. Escape times evaluated on the basis of a diffusional model and the desorption free energies are 0.07 s (into the squalane) and 300 h (into the water). The latter value is consistent with irreversible absorption observed by related experimental work.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerald Hill; Kenneth Nemeth; Gary Garrett

The Southern States Energy Board's (SSEB) 'Regional Effort to Deploy Clean Coal Technologies' program began on June 1, 2003, and was completed on January 31, 2009. The project proved beneficial in providing state decision-makers with information that assisted them in removing barriers or implementing incentives to deploy clean coal technologies. This was accomplished through two specific tasks: (1) domestic energy security and diversity; and (2) the energy-water interface. Milestones accomplished during the project period are: (1) Presentations to Annual Meetings of SSEB Members, Associate Member Meetings, and the Gasification Technologies Council. (2) Energy: Water reports - (A) Regional Efforts tomore » Deploy Clean Coal Technologies: Impacts and Implications for Water Supply and Quality. June 2004. (B) Energy-Water Interface Challenges: Coal Bed Methane and Mine Pool Water Characterization in the Southern States Region. 2004. (C) Freshwater Availability and Constraints on Thermoelectric Power Generation in the Southeast U.S. June 2008. (3) Blackwater Interactive Tabletop Exercise - Decatur, Georgia April 2007. (4) Blackwater Report: Blackwater: Energy and Water Interdependency Issues: Best Practices and Lessons Learned. August 2007. (5) Blackwater Report: BLACKWATER: Energy Water Interdependency Issues REPORT SUMMARY. April 2008.« less

The effect of water on the solid state characteristics of pharmaceutical excipients: Molecular mechanisms, measurement techniques, and quality aspects of final dosage form

PubMed Central

Szakonyi, Gergely; Zelkó, Romána

2012-01-01

In this paper we give an overview about the interaction of water molecules with pharmaceutical excipients. Most of these excipients are amorphous or partially amorphous polymers and their characteristics are very sensitive to the water content. In the course of the manufacturing processes water sorption is possible, therefore in some cases it is important to strictly control the residual moisture content of a dosage form. There are several mechanisms of water sorption, like water is able to bind to polar groups of hygroscopic excipients and could also exist in the capillary system of amorphous excipients. Several techniques are available to characterise the states of water inside the materials and the effects of residual water on polymers. For this purpose water sorption measurements, differential scanning calorimetry and the Fourier-transform infrared spectroscopy are reviewed. The importance of water content and storage conditions of pharmaceuticals on the properties of the final dosage forms are also demonstrated with practical examples. PMID:23071956

First-principles molecular dynamics study of water dissociation on the γ-U(1 0 0) surface

NASA Astrophysics Data System (ADS)

Yang, Yu; Zhang, Ping

2015-05-01

Based on first-principles molecular dynamics simulations at finite temperatures, we systematically study the adsorption and dissociation of water molecules on the γ-U(1 0 0) surface. We predict that water molecules spontaneously dissociate upon approaching the native γ-U(1 0 0) surface. The dissociation results from electronic interactions between surface uranium 6d states and 1b2, 3a1, and 1b1 molecular orbitals of water. With segregated Nb atoms existing on the surface, adsorbing water molecules also dissociate spontaneously because Nb 3d electronic states can also interact with the molecular orbitals similarly. After dissociation, the isolated hydrogen atoms are found to diffuse fast on both the γ-U surface and that with a surface substitutional Nb atom, which is very similar to the ‘Hot-Atom’ dissociation of oxygen molecules on the Al(1 1 1) surface. From a series of consecutive molecular dynamics simulations, we further reveal that on both the γ-U surface and that with a surface substitutional Nb atom, one surface U atom will be pulled out to form the U-O-U structure after dissociative adsorption of 0.44 ML water molecules. This result indicates that oxide nucleus can form at low coverage of water adsorption on the two surfaces.

Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions

NASA Astrophysics Data System (ADS)

Taylor, Sean; Samokhvalov, Alexander

2017-03-01

Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3 is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3 at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3 was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3 is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.

Water-polysaccharide interactions in the primary cell wall of Arabidopsis thaliana from polarization transfer solid-state NMR.

PubMed

White, Paul B; Wang, Tuo; Park, Yong Bum; Cosgrove, Daniel J; Hong, Mei

2014-07-23

Polysaccharide-rich plant cell walls are hydrated under functional conditions, but the molecular interactions between water and polysaccharides in the wall have not been investigated. In this work, we employ polarization transfer solid-state NMR techniques to study the hydration of primary-wall polysaccharides of the model plant, Arabidopsis thaliana. By transferring water (1)H polarization to polysaccharides through distance- and mobility-dependent (1)H-(1)H dipolar couplings and detecting it through polysaccharide (13)C signals, we obtain information about water proximity to cellulose, hemicellulose, and pectins as well as water mobility. Both intact and partially extracted cell wall samples are studied. Our results show that water-pectin polarization transfer is much faster than water-cellulose polarization transfer in all samples, but the extent of extraction has a profound impact on the water-polysaccharide spin diffusion. Removal of calcium ions and the consequent extraction of homogalacturonan (HG) significantly slowed down spin diffusion, while further extraction of matrix polysaccharides restored the spin diffusion rate. These trends are observed in cell walls with similar water content, thus they reflect inherent differences in the mobility and spatial distribution of water. Combined with quantitative analysis of the polysaccharide contents, our results indicate that calcium ions and HG gelation increase the amount of bound water, which facilitates spin diffusion, while calcium removal disrupts the gel and gives rise to highly dynamic water, which slows down spin diffusion. The recovery of spin diffusion rates after more extensive extraction is attributed to increased water-exposed surface areas of the polysaccharides. Water-pectin spin diffusion precedes water-cellulose spin diffusion, lending support to the single-network model of plant primary walls in which a substantial fraction of the cellulose surface is surrounded by pectins.

An Analytic Approach to Modeling Land-Atmosphere Interaction: 1. Construct and Equilibrium Behavior

NASA Astrophysics Data System (ADS)

Brubaker, Kaye L.; Entekhabi, Dara

1995-03-01

A four-variable land-atmosphere model is developed to investigate the coupled exchanges of water and energy between the land surface and atmosphere and the role of these exchanges in the statistical behavior of continental climates. The land-atmosphere system is substantially simplified and formulated as a set of ordinary differential equations that, with the addition of random noise, are suitable for analysis in the form of the multivariate Îto equation. The model treats the soil layer and the near-surface atmosphere as reservoirs with storage capacities for heat and water. The transfers between these reservoirs are regulated by four states: soil saturation, soil temperature, air specific humidity, and air potential temperature. The atmospheric reservoir is treated as a turbulently mixed boundary layer of fixed depth. Heat and moisture advection, precipitation, and layer-top air entrainment are parameterized. The system is forced externally by solar radiation and the lateral advection of air and water mass. The remaining energy and water mass exchanges are expressed in terms of the state variables. The model development and equilibrium solutions are presented. Although comparisons between observed data and steady state model results re inexact, the model appears to do a reasonable job of partitioning net radiation into sensible and latent heat flux in appropriate proportions for bare-soil midlatitude summer conditions. Subsequent work will introduce randomness into the forcing terms to investigate the effect of water-energy coupling and land-atmosphere interaction on variability and persistence in the climatic system.

Long-Term Uptake of Phenol-Water Vapor Follows Similar Sigmoid Kinetics on Prehydrated Organic Matter- and Clay-Rich Soil Sorbents.

PubMed

Borisover, Mikhail; Bukhanovsky, Nadezhda; Lado, Marcos

2017-09-19

Typical experimental time frames allowed for equilibrating water-organic vapors with soil sorbents might lead to overlooking slow chemical reactions finally controlling a thermodynamically stable state. In this work, long-term gravimetric examination of kinetics covering about 4000 h was performed for phenol-water vapor interacting with four materials pre-equilibrated at three levels of air relative humidity (RHs 52, 73, and 92%). The four contrasting sorbents included an organic matter (OM)-rich peat soil, an OM-poor clay soil, a hydrophilic Aldrich humic acid salt, and water-insoluble leonardite. Monitoring phenol-water vapor interactions with the prehydrated sorbents, as compared with the sorbent samples in phenol-free atmosphere at the same RH, showed, for the first time, a sigmoid kinetics of phenol-induced mass uptake typical for second-order autocatalytic reactions. The apparent rate constants were similar for all the sorbents, RHs and phenol activities studied. A significant part of sorbed phenol resisted extraction, which was attributed to its abiotic oxidative coupling. Phenol uptake by peat and clay soils was also associated with a significant enhancement of water retention. The delayed development of the sigmoidal kinetics in phenol-water uptake demonstrates that long-run abiotic interactions of water-organic vapor with soil may be overlooked, based on short-term examination.

Interactive effects of nocturnal transpiration and climate change on the root hydraulic redistribution and carbon and water budgets of southern United States pine plantations

Treesearch

Jean-Christophe Domec; Jérôme Ogée; Asko Noormets; Julien Jouangy; Michael Gavazzi; Emrys Treasure; Ge Sun; Steve G. McNulty; John S. King

2012-01-01

Deep root water uptake and hydraulic redistribution (HR) have been shown to play a major role in forest ecosystems during drought, but little is known about the impact of climate change, fertilization and soil characteristics on HR and its consequences on water and carbon fluxes. Using data from three mid-rotation loblolly pine plantations, and simulations with the...

Thermodynamics of cellulose solvation in water and the ionic liquid 1-butyl-3-methylimidazolim chloride.

PubMed

Gross, Adam S; Bell, Alexis T; Chu, Jhih-Wei

2011-11-24

Cellulose is present in biomass as crystalline microfibrils held together by a complex network of intermolecular interactions making it difficult to initiate its hydrolysis and conversion to fuels. While cellulose is insoluble in water and most organic solvents, complete dissolution of cellulose can be achieved in certain classes of ionic liquids (ILs). The present study was undertaken to analyze the thermodynamic driving forces of this process and to understand how the anions and cations comprising an IL interact with the different moieties of glucose residues to cause dissolution. All-atom molecular dynamics (MD) simulations were performed at two extreme states of cellulose dissolution: a crystalline microfibril and a dissociated state in which all the glucan chains of the microfibril are fully separated from each other by at least four solvation shells. MD simulations of the two states were carried out in water and in the IL 1-butyl-3-methylimidazolium chloride (BmimCl) to provide a comprehensive analysis of solvent effects on cellulose dissolution. The results reveal two important molecular aspects of the mechanism of cellulose dissolution. The first is that the perturbation of solvent structures by the dissolved glucan chains can be a crucial factor in determining solubility, particularly for the insolubility of cellulose in water at 300 K. Second, both the Cl(-) and the Bmim(+) ions of BmimCl interact with the moieties of glucan residues that form intersheet contacts, the most robust component of the interaction network of crystalline cellulose. Cl(-) anions can form hydrogen bonds (HBs) with the hydroxyl groups of glucan chains from either the equatorial or the axial directions. For Bmim(+) cations, the calculated density profiles reveal that the contacts with glucan chains along the axial directions are closer than those along the equatorial directions. On the basis of the results of atomistic MD simulations, we propose that interacting with glucan chains along axial directions and disrupting the intersheet contacts of cellulose is an important ability of cellulose pretreatment solvents. © 2011 American Chemical Society

Thermodynamic and structural signatures of water-driven methane-methane attraction in coarse-grained mW water.

PubMed

Song, Bin; Molinero, Valeria

2013-08-07

Hydrophobic interactions are responsible for water-driven processes such as protein folding and self-assembly of biomolecules. Microscopic theories and molecular simulations have been used to study association of a pair of methanes in water, the paradigmatic example of hydrophobic attraction, and determined that entropy is the driving force for the association of the methane pair, while the enthalpy disfavors it. An open question is to which extent coarse-grained water models can still produce correct thermodynamic and structural signatures of hydrophobic interaction. In this work, we investigate the hydrophobic interaction between a methane pair in water at temperatures from 260 to 340 K through molecular dynamics simulations with the coarse-grained monatomic water model mW. We find that the coarse-grained model correctly represents the free energy of association of the methane pair, the temperature dependence of free energy, and the positive change in entropy and enthalpy upon association. We investigate the relationship between thermodynamic signatures and structural order of water through the analysis of the spatial distribution of the density, energy, and tetrahedral order parameter Qt of water. The simulations reveal an enhancement of tetrahedral order in the region between the first and second hydration shells of the methane molecules. The increase in tetrahedral order, however, is far from what would be expected for a clathrate-like or ice-like shell around the solutes. This work shows that the mW water model reproduces the key signatures of hydrophobic interaction without long ranged electrostatics or the need to be re-parameterized for different thermodynamic states. These characteristics, and its hundred-fold increase in efficiency with respect to atomistic models, make mW a promising water model for studying water-driven hydrophobic processes in more complex systems.

Interaction of L-Phenylalanine with a Phospholipid Monolayer at the Water-Air Interface.

PubMed

Griffith, Elizabeth C; Perkins, Russell J; Telesford, Dana-Marie; Adams, Ellen M; Cwiklik, Lukasz; Allen, Heather C; Roeselová, Martina; Vaida, Veronica

2015-07-23

The interaction of L-phenylalanine with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer at the air-water interface was explored using a combination of experimental techniques and molecular dynamics (MD) simulations. By means of Langmuir trough methods and Brewster angle microscopy, L-phenylalanine was shown to significantly alter the interfacial tension and the surface domain morphology of the DPPC film. In addition, confocal microscopy was used to explore the aggregation state of L-phenylalanine in the bulk aqueous phase. Finally, MD simulations were performed to gain molecular-level information on the interactions of L-phenylalanine and DPPC at the interface. Taken together, these results show that L-phenylalanine intercalates into a DPPC film at the air-water interface, thereby affecting the surface tension, phase morphology, and ordering of the DPPC film. The results are discussed in the context of biological systems and the mechanism of diseases such as phenylketonuria.

How to examine soil sorption of ionizable organic compounds and avoid varying pH?

NASA Astrophysics Data System (ADS)

Borisover, Mikhail

2017-04-01

Multiple natural and anthropogenic organic compounds including new and emerging pollutants undergo ionization in aqueous solutions, and their sorption by soils and sediments is contributed by presence of both molecular and ionized species. Better understanding of environmental fate of organic chemicals requires taking into account interactions of molecular and ionized species with environmental sorbents. A "standard" (and undoubtedly important) procedure for differentiating contributions of molecular and ionized species into the overall soil sorption of an organic compound involves varying pH of solution in batch sorption experiments. However, varying pH is (1) often not possible, without destroying a sorbent, e.g., due to the buffer capacity of soils containing carbonates, (2) difficult for further interpretation, since it changes not only the ionization status of a solute in a solution but also the sorbent structure, e.g., a conformation of organic matter, and/or ionization of surface functional groups, (3) making difficult (or even impossible) to explicitly evaluate the role of dissolved species-bulk water interactions, directly affecting the affinity of a sorbate to distribute between water and a sorbent. Indeed, both molecular and ionized species undergo interactions with the solvent bulk and, at least in the case of the ionized ones, there was no a simple way to quantify organic ion-water interactions and their role in organic ion distribution between soil and water phases. This paper presents a "counter-intuitive" approach to examine sorption interactions of an ionizable compound, without experimenting with varied pH. The approach is based on an idea of replacing an initial state in sorption transfer of an ionizable compound from the solvent bulk to a solvated (hydrated) sorbed state: a traditional coefficient describing distribution of a partially ionized compound between a hydrated sorbent and a co-equilibrated aqueous phase is converted to the coefficient describing the transfer of the sorbing compound from its initial molecular (non-ionized) state (in a solution or in the gas phase) to the final hydrated sorbed state equilibrated with the actual aqueous solution of this ionizable compound. In this way, any contributions from the bulk solvent-organic ion interactions into the sorption transfer may be excluded; in addition, further any solute-solvent interactions may be taken out of the consideration. Therefore, compound's sorption characteristics "cleared" of solute-solvent interactions may be obtained, and a better understanding of relations between interactions in a sorbed phase and a molecular structure of organic sorbates can be reached. The approach is illustrated by examining sorption of variously ionized organic compounds, i.e., those belonging to the pharmaceuticals and personal care products (triclosan, gemfibrozil, galaxolide), and aliphatic organic acids on natural and organic amendment-enriched soils. Specifically, it is demonstrated how the greater H-donating ability of trifluoroacetic acid, as compared with acetic acid, strengthens the acid interactions in the soil phase. In another series of examples, it is shown how hydrophobic and non-ionizing galaxolide interacts weakly with soils, as compared with partially ionized triclosan and almost fully ionized gemfibrozil, i.e., leading to the conclusions not reachable based only on the direct comparison of experimentally measured distribution coefficients.

Collaborative routes to clarifying the murky waters of aqueous supramolecular chemistry.

PubMed

Cremer, Paul S; Flood, Amar H; Gibb, Bruce C; Mobley, David L

2017-12-19

On planet Earth, water is everywhere: the majority of the surface is covered with it; it is a key component of all life; its vapour and droplets fill the lower atmosphere; and even rocks contain it and undergo geomorphological changes because of it. A community of physical scientists largely drives studies of the chemistry of water and aqueous solutions, with expertise in biochemistry, spectroscopy and computer modelling. More recently, however, supramolecular chemists - with their expertise in macrocyclic synthesis and measuring supramolecular interactions - have renewed their interest in water-mediated non-covalent interactions. These two groups offer complementary expertise that, if harnessed, offer to accelerate our understanding of aqueous supramolecular chemistry and water writ large. This Review summarizes the state-of-the-art of the two fields, and highlights where there is latent chemical space for collaborative exploration by the two groups.

Hydroxide diffuses slower than hydronium in water because its solvated structure inhibits correlated proton transfer

NASA Astrophysics Data System (ADS)

Chen, Mohan; Zheng, Lixin; Santra, Biswajit; Ko, Hsin-Yu; DiStasio, Robert A., Jr.; Klein, Michael L.; Car, Roberto; Wu, Xifan

2018-03-01

Proton transfer via hydronium and hydroxide ions in water is ubiquitous. It underlies acid-base chemistry, certain enzyme reactions, and even infection by the flu. Despite two centuries of investigation, the mechanism underlying why hydroxide diffuses slower than hydronium in water is still not well understood. Herein, we employ state-of-the-art density-functional-theory-based molecular dynamics—with corrections for non-local van der Waals interactions, and self-interaction in the electronic ground state—to model water and hydrated water ions. At this level of theory, we show that structural diffusion of hydronium preserves the previously recognized concerted behaviour. However, by contrast, proton transfer via hydroxide is less temporally correlated, due to a stabilized hypercoordination solvation structure that discourages proton transfer. Specifically, the latter exhibits non-planar geometry, which agrees with neutron-scattering results. Asymmetry in the temporal correlation of proton transfer leads to hydroxide diffusing slower than hydronium.

Collaborative routes to clarifying the murky waters of aqueous supramolecular chemistry

NASA Astrophysics Data System (ADS)

Cremer, Paul S.; Flood, Amar H.; Gibb, Bruce C.; Mobley, David L.

2018-01-01

On planet Earth, water is everywhere: the majority of the surface is covered with it; it is a key component of all life; its vapour and droplets fill the lower atmosphere; and even rocks contain it and undergo geomorphological changes because of it. A community of physical scientists largely drives studies of the chemistry of water and aqueous solutions, with expertise in biochemistry, spectroscopy and computer modelling. More recently, however, supramolecular chemists -- with their expertise in macrocyclic synthesis and measuring supramolecular interactions -- have renewed their interest in water-mediated non-covalent interactions. These two groups offer complementary expertise that, if harnessed, offer to accelerate our understanding of aqueous supramolecular chemistry and water writ large. This Review summarizes the state-of-the-art of the two fields, and highlights where there is latent chemical space for collaborative exploration by the two groups.

Behavior of severely supercooled water drops impacting on superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Maitra, Tanmoy; Antonini, Carlo; Tiwari, Manish K.; Mularczyk, Adrian; Imeri, Zulkufli; Schoch, Philippe; Poulikakos, Dimos

2014-11-01

Surface icing, commonplace in nature and technology, has broad implications to daily life. To prevent surface icing, superhydrophobic surfaces/coatings with rationally controlled roughness features (both at micro and nano-scale) are considered to be a promising candidate. However, to fabricate/synthesize a high performance icephobic surface or coating, understanding the dynamic interaction between water and the surface during water drop impact in supercooled state is necessary. In this work, we investigate the water/substrate interaction using drop impact experiments down to -17°C. It is found that the resulting increased viscous effect of water at low temperature significantly affects all stages of drop dynamics such as maximum spreading, contact time and meniscus penetration into the superhydrophobic texture. Most interestingly, the viscous effect on the meniscus penetration into roughness feature leads to clear change in the velocity threshold for rebounding to sticking transition by 25% of supercooled drops. Swiss National Science Foundation (SNF) Grant 200021_135479.

a System Dynamics Approach for Looking at the Human and Environmental Interactions of Community-Based Irrigation Systems in New Mexico

NASA Astrophysics Data System (ADS)

Ochoa, C. G.; Tidwell, V. C.

2012-12-01

In the arid southwestern United States community water management systems have adapted to cope with climate variability and with socio-cultural and economic changes that have occurred since the establishment of these systems more than 300 years ago. In New Mexico, the community-based irrigation systems were established by Spanish settlers and have endured climate variability in the form of low levels of precipitation and have prevailed over important socio-political changes including the transfer of territory between Spain and Mexico, and between Mexico and the United States. Because of their inherent nature of integrating land and water use with society involvement these community-based systems have multiple and complex economic, ecological, and cultural interactions. Current urban population growth and more variable climate conditions are adding pressure to the survival of these systems. We are conducting a multi-disciplinary research project that focuses on characterizing these intrinsically complex human and natural interactions in three community-based irrigation systems in northern New Mexico. We are using a system dynamics approach to integrate different hydrological, ecological, socio-cultural and economic aspects of these three irrigation systems. Coupled with intensive field data collection, we are building a system dynamics model that will enable us to simulate important linkages and interactions between environmental and human elements occurring in each of these water management systems. We will test different climate variability and population growth scenarios and the expectation is that we will be able to identify critical tipping points of these systems. Results from this model can be used to inform policy recommendations relevant to the environment and to urban and agricultural land use planning in the arid southwestern United States.

Coastal groundwater/surface-water interactions: a Great Lakes case study

USGS Publications Warehouse

Neff, Brian P.; Haack, Sheridan K.; Rosenberry, Donald O.; Savino, Jacqueline F.; Lundstrom, Scott C.

2006-01-01

Key similarities exist between marine and Great Lakes coastal environments. Water and nutrient fluxes across lakebeds in the Great Lakes are influenced by seiche and wind set-up and set-down, analogous to tidal influence in marine settings. Groundwater/surface-water interactions also commonly involve a saline-fresh water interface, although in the Great-Lakes cases, it is groundwater that is commonly saline and surface water that is fresh. Evapotranspiration also affects nearshore hydrology in both settings. Interactions between groundwater and surface water have recently been identified as an important component of ecological processes in the Great Lakes. Water withdrawals and the reversal of the groundwater/surface water seepage gradient are also common to many coastal areas around the Great Lakes. As compared to surface water, regional groundwater that discharges to western Lake Erie from Michigan is highly mineralized. Studies conducted by the U.S. Geological Survey at Erie State Game Area in southeastern Michigan, describe groundwater flow dynamics and chemistry, shallow lake-water chemistry, and fish and invertebrate communities. Results presented here provide an overview of recent progress of ongoing interdisciplinary studies of Great Lakes nearshore systems and describe a conceptual model that identifies relations among geologic, hydrologic, chemical, and biological processes in the coastal habitats of Lake Erie. This conceptual model is based on analysis of hydraulic head in piezometers at the study site and chemical analysis of deep and shallow coastal groundwater.

Stress and temperature distributions of individual particles in a shock wave propagating through dry and wet sand mixtures

NASA Astrophysics Data System (ADS)

Schumaker, Merit G.; Kennedy, Gregory; Thadhani, Naresh; Hankin, Markos; Stewart, Sarah T.; Borg, John P.

2017-01-01

Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, the researcher cannot easily observe particle interactions during a planar shock experiment. By using mesoscale simulations, we can unravel granular particle interactions. Unlike homogenous materials, the averaged Hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. From planar shock experiments for dry and water-saturated Oklahoma sand, we constructed simulations using Sandia National Laboratory code known as CTH and then compared these simulated results to the experimental results. This document compares and presents stress and temperature distributions from simulations, with a discussion on the difference between Hugoniot measurements and distribution peaks for dry and water-saturated sand.

Effect of collector molecular structure on the wettability of gold for froth flotation

NASA Astrophysics Data System (ADS)

Moncayo-Riascos, Ivan; Hoyos, Bibian A.

2017-10-01

Molecular dynamics simulations were conducted to evaluate the alteration of the hydrophilic state of gold surfaces caused by the adsorption of collectors with different molecular structures, using the contact angle of water droplets as an evaluation parameter. Four collectors were evaluated: SDS (with twelve hydrogenated carbon atoms), PAX (with five hydrogenated carbon atoms), DTP (with two branched aliphatic chains) and MBT (with an aromatic ring). The contact angle was evaluated for coatings of a monolayer (ML) and for surface densities of 2.89 μmol/m2 for each collector. For a ML, the hydrophobic effect generated by the aromatic ring of the MBT collector is comparable with the effect of the non-polar short chain of the PAX collector. The increase in hydrophobicity for the gold surfaces achieved by collectors with aliphatic chains is because the water-collector interaction energy is significantly higher (repulsive) than the water-gold interactions (attractive). The lowest increase in hydrophobicity was achieved with the MBT collector, since the carbon-water interaction energy of the aromatic ring is stronger than the interaction with the carbon atoms in the aliphatic chains. The calculated contact angles of the water droplets deviated less than 4% with respect to the experimental values.

Global Operational Remotely Sensed Evapotranspiration System for Water Resources Management: Case Study for the State of New Mexico

NASA Astrophysics Data System (ADS)

Halverson, G. H.; Fisher, J.; Magnuson, M.; John, L.

2017-12-01

An operational system to produce and disseminate remotely sensed evapotranspiration using the PT-JPL model and support its analysis and use in water resources decision making is being integrated into the New Mexico state government. A partnership between the NASA Western Water Applications Office (WWAO), the Jet Propulsion Laboratory (JPL), and the New Mexico Office of the State Engineer (NMOSE) has enabled collaboration with a variety of state agencies to inform decision making processes for agriculture, rangeland, and forest management. This system improves drought understanding and mobilization, litigation support, and economic, municipal, and ground-water planning through interactive mapping of daily rates of evapotranspiration at 1 km spatial resolution with near real-time latency. This is facilitated by daily remote sensing acquisitions of land-surface temperature and near-surface air temperature and humidity from the Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite as well as the short-term composites of Normalized Difference Vegetation Index (NDVI) and albedo provided by MODIS. Incorporating evapotranspiration data into agricultural water management better characterizes imbalances between water requirements and supplies. Monitoring evapotranspiration over rangeland areas improves remediation and prevention of aridification. Monitoring forest evapotranspiration improves wildlife management and response to wildfire risk. Continued implementation of this decision support system should enhance water and food security.

Water-chromophore electron transfer determines the photochemistry of cytosine and cytidine.

PubMed

Szabla, Rafał; Kruse, Holger; Šponer, Jiří; Góra, Robert W

2017-07-21

Many of the UV-induced phenomena observed experimentally for aqueous cytidine were lacking the mechanistic interpretation for decades. These processes include the substantial population of the puzzling long-lived dark state, photohydration, cytidine to uridine conversion and oxazolidinone formation. Here, we present quantum-chemical simulations of excited-state spectra and potential energy surfaces of N1-methylcytosine clustered with two water molecules using the second-order approximate coupled cluster (CC2), complete active space with second-order perturbation theory (CASPT2), and multireference configuration interaction with single and double excitation (MR-CISD) methods. We argue that the assignment of the long-lived dark state to a singlet nπ* excitation involving water-chromophore electron transfer might serve as an explanation for the numerous experimental observations. While our simulated spectra for the state are in excellent agreement with experimentally acquired data, the electron-driven proton transfer process occurring on the surface may initiate the subsequent damage in the vibrationally hot ground state of the chromophore.

Development of a methodology to compute solvation free energies on the basis of the theory of energy representation for solutions represented with a polarizable force field.

PubMed

Suzuoka, Daiki; Takahashi, Hideaki; Ishiyama, Tatsuya; Morita, Akihiro

2012-12-07

We have developed a method of molecular simulations utilizing a polarizable force field in combination with the theory of energy representation (ER) for the purpose of establishing an efficient and accurate methodology to compute solvation free energies. The standard version of the ER method is, however, based on the assumption that the solute-solvent interaction is pairwise additive for its construction. A crucial step in the present method is to introduce an intermediate state in the solvation process to treat separately the many-body interaction associated with the polarizable model. The intermediate state is chosen so that the solute-solvent interaction can be formally written in the pairwise form, though the solvent molecules are interacting with each other with polarizable charges dependent on the solvent configuration. It is, then, possible to extract the free energy contribution δμ due to the many-body interaction between solute and solvent from the total solvation free energy Δμ. It is shown that the free energy δμ can be computed by an extension of the recent development implemented in quantum mechanical∕molecular mechanical simulations. To assess the numerical robustness of the approach, we computed the solvation free energies of a water and a methanol molecule in water solvent, where two paths for the solvation processes were examined by introducing different intermediate states. The solvation free energies of a water molecule associated with the two paths were obtained as -5.3 and -5.8 kcal∕mol. Those of a methanol molecule were determined as -3.5 and -3.7 kcal∕mol. These results of the ER simulations were also compared with those computed by a numerically exact approach. It was demonstrated that the present approach produces the solvation free energies in comparable accuracies to simulations of thermodynamic integration (TI) method within a tenth of computational time used for the TI simulations.

Thermodynamics of water sorption in high performance glassy thermoplastic polymers

PubMed Central

Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino; Mensitieri, Giuseppe

2014-01-01

Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different “populations” of water molecules present within the PEEK and a quantitative assessment of these “populations” in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data. PMID:24860802

National Interest Shown in Watershed Mapping Tool

EPA Pesticide Factsheets

The State of Maryland is able to identify prime locations for watershed restoration and preservation using an interactive mapping tool developed by a partnership of agencies led by EPA’s Mid-Atlantic Water Protection Division.

CORAL REEF BIOLOGICAL CRITERIA: USING THE CLEAN ...

EPA Pesticide Factsheets

Coral reefs are declining at unprecedented rates worldwide due to multiple interactive stressors including climate change and land-based sources of pollution. The Clean Water Act (CWA) can be a powerful legal instrument for protecting water resources, including the biological inhabitants of coral reefs. The objective of the CWA is to restore and maintain the chemical, physical and biological integrity of water resources. Coral reef protection and restoration under the Clean Water Act begins with water quality standards - provisions of state or Federal law that consist of a designated use(s) for the waters of the United States and water quality criteria sufficient to protect the uses. Aquatic life use is the designated use that is measured by biological criteria (biocriteria). Biocriteria are expectations set by a jurisdiction for the quality and quantity of living aquatic resources in a defined waterbody. Biocriteria are an important addition to existing management tools for coral reef ecosystems. The Technical Support Document “Coral Reef Biological Criteria: Using the Clean Water Act to Protect a National Treasure” will provide a framework to aid States and Territories in their development, adoption, and implementation of coral reef biocriteria in their respective water quality standards. The Technical Support Document “Coral Reef Biological Criteria: Using the Clean Water Act to Protect a National Treasure” will provide a framework for coral re

Supramolecular Structures with Blood Plasma Proteins, Sugars and Nanosilica

NASA Astrophysics Data System (ADS)

Turov, V. V.; Gun'ko, V. M.; Galagan, N. P.; Rugal, A. A.; Barvinchenko, V. M.; Gorbyk, P. P.

Supramolecular structures with blood plasma proteins (albumin, immunoglobulin and fibrinogen (HPF)), protein/water/silica and protein/water/ silica/sugar (glucose, fructose and saccharose) were studied by NMR, adsorption, IR and UV spectroscopy methods. Hydration parameters, amounts of weakly and strongly bound waters and interfacial energy (γ S) were determined over a wide range of component concentrations. The γ S(C protein,C silica) graphs were used to estimate the energy of protein-protein, protein-surface and particle-particle interactions. It was shown that interfacial energy of self-association (γ as) of protein molecules depends on a type of proteins. A large fraction of water bound to proteins can be displaced by sugars, and the effect of disaccharide (saccharose) was greater than that of monosugars. Changes in the structural parameters of cavities in HPF molecules and complexes with HPF/silica nanoparticles filled by bound water were analysed using NMR-cryoporometry showing that interaction of proteins with silica leads to a significant decrease in the amounts of water bound to both protein and silica surfaces. Bionanocomposites with BSA/nanosilica/sugar can be used to influence states of living cells and tissues after cryopreservation or other treatments. It was shown that interaction of proteins with silica leads to strong decrease in the volume of all types of internal cavities filled by water.

The Action of a Magnetic Field on Water,

DTIC Science & Technology

The effect of a low intensity magnetic field on water as a flotation medium with the enrichment of coal and dressing of copper sulfied ore is studied...magnetic field with flotation is expressed. The imposition of an external magnetic field disturbs the energy state of water, which leads to a change in...intermolecular interaction, stability of hydrogen bonds, deterioration in the wettability of rigid surfaces, and a change in the technological indices of flotation enrichment. (Author)

Modelling wetland-groundwater interactions in the boreal Kälväsvaara esker, Northern Finland

NASA Astrophysics Data System (ADS)

Jaros, Anna; Rossi, Pekka; Ronkanen, Anna-Kaisa; Kløve, Bjørn

2016-04-01

Many types of boreal peatland ecosystems such as alkaline fens, aapa mires and Fennoscandia spring fens rely on the presence of groundwater. In these ecosystems groundwater creates unique conditions for flora and fauna by providing water, nutrients and constant water temperature enriching local biodiversity. The groundwater-peatland interactions and their dynamics are not, however, in many cases fully understood and their measurement and quantification is difficult due to highly heterogeneous structure of peatlands and large spatial extend of these ecosystems. Understanding of these interactions and their changes due to anthropogenic impact on groundwater resources would benefit the protection of the groundwater dependent peatlands. The groundwater-peatland interactions were investigated using the fully-integrated physically-based groundwater-surface water code HydroGeoSphere in a case study of the Kälväsvaara esker aquifer, Northern Finland. The Kälväsvaara is a geologically complex esker and it is surrounded by vast aapa mire system including alkaline and springs fens. In addition, numerous small springs occur in the discharge zone of the esker. In order to quantify groundwater-peatland interactions a simple steady-state model was built and results were evaluated using expected trends and field measurements. The employed model reproduced relatively well spatially distributed hydrological variables such as soil water content, water depths and groundwater-surface water exchange fluxes within the wetland and esker areas. The wetlands emerged in simulations as a result of geological and topographical conditions. They could be identified by high saturation levels at ground surface and by presence of shallow ponded water over some areas. The model outputs exhibited also strong surface water-groundwater interactions in some parts of the aapa system. These areas were noted to be regions of substantial diffusive groundwater discharge by the earlier studies. In contrast, the simulations were not able to capture small scale point groundwater discharge i.e. springs. This reflects that modelling small scale groundwater input to wetland ecosystems can be challenging without detailed information on the aquifer and wetland geology. Overall, the good consistency between simulations and observations demonstrated that wetland-groundwater interactions can be studied using fully-integrated physically-based groundwater-surface water models.

A statistical mechanical theory for a two-dimensional model of water

NASA Astrophysics Data System (ADS)

Urbic, Tomaz; Dill, Ken A.

2010-06-01

We develop a statistical mechanical model for the thermal and volumetric properties of waterlike fluids. Each water molecule is a two-dimensional disk with three hydrogen-bonding arms. Each water interacts with neighboring waters through a van der Waals interaction and an orientation-dependent hydrogen-bonding interaction. This model, which is largely analytical, is a variant of the Truskett and Dill (TD) treatment of the "Mercedes-Benz" (MB) model. The present model gives better predictions than TD for hydrogen-bond populations in liquid water by distinguishing strong cooperative hydrogen bonds from weaker ones. We explore properties versus temperature T and pressure p. We find that the volumetric and thermal properties follow the same trends with T as real water and are in good general agreement with Monte Carlo simulations of MB water, including the density anomaly, the minimum in the isothermal compressibility, and the decreased number of hydrogen bonds for increasing temperature. The model reproduces that pressure squeezes out water's heat capacity and leads to a negative thermal expansion coefficient at low temperatures. In terms of water structuring, the variance in hydrogen-bonding angles increases with both T and p, while the variance in water density increases with T but decreases with p. Hydrogen bonding is an energy storage mechanism that leads to water's large heat capacity (for its size) and to the fragility in its cagelike structures, which are easily melted by temperature and pressure to a more van der Waals-like liquid state.

A statistical mechanical theory for a two-dimensional model of water.

PubMed

Urbic, Tomaz; Dill, Ken A

2010-06-14

We develop a statistical mechanical model for the thermal and volumetric properties of waterlike fluids. Each water molecule is a two-dimensional disk with three hydrogen-bonding arms. Each water interacts with neighboring waters through a van der Waals interaction and an orientation-dependent hydrogen-bonding interaction. This model, which is largely analytical, is a variant of the Truskett and Dill (TD) treatment of the "Mercedes-Benz" (MB) model. The present model gives better predictions than TD for hydrogen-bond populations in liquid water by distinguishing strong cooperative hydrogen bonds from weaker ones. We explore properties versus temperature T and pressure p. We find that the volumetric and thermal properties follow the same trends with T as real water and are in good general agreement with Monte Carlo simulations of MB water, including the density anomaly, the minimum in the isothermal compressibility, and the decreased number of hydrogen bonds for increasing temperature. The model reproduces that pressure squeezes out water's heat capacity and leads to a negative thermal expansion coefficient at low temperatures. In terms of water structuring, the variance in hydrogen-bonding angles increases with both T and p, while the variance in water density increases with T but decreases with p. Hydrogen bonding is an energy storage mechanism that leads to water's large heat capacity (for its size) and to the fragility in its cagelike structures, which are easily melted by temperature and pressure to a more van der Waals-like liquid state.

Global water cycle

NASA Technical Reports Server (NTRS)

Robertson, Franklin; Goodman, Steven J.; Christy, John R.; Fitzjarrald, Daniel E.; Chou, Shi-Hung; Crosson, William; Wang, Shouping; Ramirez, Jorge

1993-01-01

This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates change on both global and regional scales. Significant accomplishments in the past year are presented and include the following: (1) water vapor variability; (2) multi-phase water analysis; (3) global modeling; and (4) optimal precipitation and stream flow analysis and hydrologic processes.

Understanding heterogeneity and data assimilation in karst groundwater surface water interactions: The role of geophysics and hydrologic models in a semi-confined aquifer

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.

Groundwater and surface water historically have been treated as different entities. Due to this, planning and development of groundwater and surface water resources, both quantity and quality are often also treated separately. Recently, there has been work to characterize groundwater and surface water as a single system. Karstic systems are widely influenced by these interactions due to varying permeability, fracture geometry and porosity. Here, three different approaches are used to characterize groundwater surface water interactions in karstic environments. 1) A hydrologic model, ParFlow, is conditioned with known subsurface data to determine whether a reduction in subsurface uncertainty will enhance the prediction of surface water variables. A reduction in subsurface uncertainty resulted in substantial reductions in uncertainty in Hortonian runoff and less reductions in Dunne runoff. 2) Geophysical data is collected at a field site in O'leno State Park, Florida to visualize groundwater and surface water interactions in karstic environments. Significant changes in resistivity are seen through time at two locations. It is hypothesized that these changes are related to changing fluid source waters (e.g groundwater or surface water). 3). To confirm these observations an ensemble of synthetic forward models are simulated, inverted and compared directly with field observations and End-Member-Mixing-Analysis (EMMA). Field observations and synthetic models have comparable resistivity anomalies patterns and mixing fractions. This allows us to characterize and quantify subsurface mixing of groundwater and surface in karst environments. These three approaches (hydrologic models, field data and forward model experiments), (1) show the complexity and dynamics of groundwater and surface mixing in karstic environments in varying flow conditions, (2) showcase a novel geophysical technique to visualize groundwater and surface water interactions and (3) confirm hypothesis of flow and mixing in subsurface karst environments.

EnviroAtlas - Industrial Water Demand by 12-Digit HUC for the Conterminous United States

EPA Pesticide Factsheets

This EnviroAtlas dataset includes industrial water demand attributes which provide insight into the amount of water currently used for manufacturing and production of commodities in the contiguous United States. The values are based on 2005 water demand and Dun and Bradstreet's 2009/2010 source data, and have been summarized by watershed or 12-digit hydrologic unit code (HUC). For the purposes of this metric, industrial water use includes chemical, food, paper, wood, and metal production. The industrial water is for self-supplied only such as by private wells or reservoirs. Sources include either surface water or groundwater. This dataset was produced by the US EPA to support research and online mapping activities related to the EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Plant Water Stress Affects Interactions Between an Invasive and a Naturalized Aphid Species on Cereal Crops.

PubMed

Foote, N E; Davis, T S; Crowder, D W; Bosque-Pérez, N A; Eigenbrode, S D

2017-06-01

In cereal cropping systems of the Pacific Northwestern United States (PNW), climate change is projected to increase the frequency of drought during summer months, which could increase water stress for crop plants. Yet, it remains uncertain how interactions between herbivore species are affected by drought stress. Here, interactions between two cereal aphids present in PNW cereal systems, Metopolophium festucae (Theobald) subsp. cerealium (a newly invasive species) and Rhopalosiphum padi L. (a naturalized species), were tested relative to wheat water stress. When aphids were confined in leaf cages on wheat, asymmetrical facilitation occurred; per capita fecundity of R. padi was increased by 46% when M. festucae cerealium was also present, compared to when only R. padi was present. Imposed water stress did not influence this interaction. When aphids were confined on whole wheat plants, asymmetrical competition occurred; cocolonization inhibited M. festucae cerealium population growth but did not affect R. padi population growth. Under conditions of plant water stress, however, the inhibitory effect of R. padi on M. festucae cerealium was not observed. We conclude that beneficial effects of cocolonization on R. padi are due to a localized plant response to M. festucae cerealium feeding, and that cocolonization of plants is likely to suppress M. festucae cerealium populations under ample water conditions, but not when plants are water stressed. This suggests that plant responses to water stress alter the outcome of competition between herbivore species, with implications for the structure of pest communities on wheat during periods of drought. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America.

Proton conducting membranes for high temperature fuel cells with solid state water free membranes

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

2006-01-01

A water free, proton conducting membrane for use in a fuel cell is fabricated as a highly conducting sheet of converted solid state organic amine salt, such as converted acid salt of triethylenediamine with two quaternized tertiary nitrogen atoms, combined with a nanoparticulate oxide and a stable binder combined with the converted solid state organic amine salt to form a polymeric electrolyte membrane. In one embodiment the membrane is derived from triethylenediamine sulfate, hydrogen phosphate or trifiate, an oxoanion with at least one ionizable hydrogen, organic tertiary amine bisulfate, polymeric quaternized amine bisulfate or phosphate, or polymeric organic compounds with quaternizable nitrogen combined with Nafion to form an intimate network with ionic interactions.

Insight into hydrogen bonds and characterization of interlayer spacing of hydrated graphene oxide.

PubMed

Liu, Liyan; Zhang, Ruifeng; Liu, Ying; Tan, Wei; Zhu, Guorui

2018-05-28

The number of hydrogen bonds and detailed information on the interlayer spacing of graphene oxide (GO) confined water molecules were calculated through experiments and molecular dynamics simulations. Experiments play a crucial role in the modeling strategy and verification of the simulation results. The binding of GO and water molecules is essentially controlled by hydrogen bond networks involving functional groups and water molecules confined in the GO layers. With the increase in the water content, the clusters of water molecules are more evident. The water molecules bounding to GO layers are transformed to a free state, making the removal of water molecules from the system difficult at low water contents. The diffuse behaviors of the water molecules are more evident at high water contents. With an increase in the water content, the functional groups are surrounded by fewer water molecules, and the distance between the functional groups and water molecules increases. As a result, the water molecules adsorbed into the GO interlamination will enlarge the interlayer spacing. The interlayer spacing is also affected by the number of GO layers. These results were confirmed by the calculations of number of hydrogen bonds, water state, mean square displacement, radial distribution function, and interlayer spacing of hydrated GO. Graphical Abstract This work research the interaction between GO functional groups and confined water molecules. The state of water molecules and interlayer spacing of graphene oxide were proved to be related to the number of hydrogen bonds.

The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates.

PubMed

Dureckova, Hana; Woo, Tom K; Udachin, Konstantin A; Ripmeester, John A; Alavi, Saman

2017-10-13

Clathrate hydrate phases of Cl 2 and Br 2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen-halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen-halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme-substrate compounds. The nature of the halogen-water interactions for the Cl 2 and Br 2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl 2 and Br 2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

National Pollutant Discharge Elimination System (NPDES)

EPA Pesticide Factsheets

Provides information about how the permit program interacts with other CWA programs to protect and improve water quality, and provides resources for professionals working in the program at the federal, state, local, and firm level, and concerned public.

Stress and Temperature Distributions of Individual Particles in a Shock Wave Propagating through Dry and Wet Sand Mixtures

NASA Astrophysics Data System (ADS)

Schumaker, Merit; Stewart, Sarah T.; Borg, John P.

2015-06-01

Determining stress and temperature distributions of dynamically compacted particles is of interest to the geophysical and astrological research communities. However, these particle interactions during a shock event are not easily observed in planar shock experiments; it is with the utilization of mesoscale simulations that these granular particle interactions can be unraveled. Unlike homogenous materials, the overall averaged hugoniot state for heterogeneous granular materials differs from the individual stress and temperature states of particles during a shock event. From planar shock experiments on dry and wet sand mixtures, simulations were constructed using CTH. A baseline dry sand simulation was also setup to be compared to sand grains that possessed water particles between grains. It is from these simulations that the distributions of stress and temperatures for individual sand and water particles are presented and compared in this document.

Free energy landscape of a minimalist salt bridge model.

PubMed

Li, Xubin; Lv, Chao; Corbett, Karen M; Zheng, Lianqing; Wu, Dongsheng; Yang, Wei

2016-01-01

Salt bridges are essential to protein stability and dynamics. Despite the importance, there has been scarce of detailed discussion on how salt bridge partners interact with each other in distinct solvent exposed environments. In this study, employing a recent generalized orthogonal space tempering (gOST) method, we enabled efficient molecular dynamics simulation of repetitive breaking and reforming of salt bridge structures within a minimalist salt-bridge model, the Asp-Arg dipeptide and thereby were able to map its detailed free energy landscape in aqueous solution. Free energy surface analysis shows that although individually-solvated states are more favorable, salt-bridge states still occupy a noticeable portion of the overall population. Notably, the competing forces, e.g. intercharge attractions that drive the formation of salt bridges and solvation forces that pull the charged groups away from each other, are energetically comparable. As the result, the salt bridge stability is highly tunable by local environments; for instance when local water molecules are perturbed to interact more strongly with each other, the population of the salt-bridge states is likely to increase. Our results reveal the critical role of local solvent structures in modulating salt-bridge partner interactions and imply the importance of water fluctuations on conformational dynamics that involves solvent accessible salt bridge formations. © 2015 The Protein Society.

Sea water - basalt interactions and genesis of the coastal thermal waters of Maharashtra, India

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muthuraman, K.

1986-01-01

The thermal waters close to the western coastal belt of India (in Maharashtra State) generally discharge Na-Ca-Cl and Ca-Na-Cl types of waters through the basic lava flows of late Cretaceous-early Tertiary age. Experimental work to study the reactions between the dilute sea water and basalt conducted in static autoclaves at selected elevated temperatures, indicates the possibility of producing chloride waters with relatively high calcium, similar to these thermal waters. In view of the increase in Ca in the resultant solutions during sea water-basalt reactions at elevated temperatures, the base temperatures computed by Na-K-Ca geothermometry would be far lower than themore » actual temperatures of the system. At lower temperatures (around 100/sup 0/C) absorption by K by basalt is possible and, hence, alkali geothermometry also may not be reliable for such systems. Anhydrite saturation temperature seems to be a reliable geothermometer for such coastal thermal water systems involving a sea water component. The results of the computer processing of the chemistry of some of these thermal waters using ''WATEQ'' are discussed. Two of these waters are oversaturated with diopside, tremolite, calcite and aragonite, indicating a rather low temperature of origin. In two other cases, interaction with ultramafic rocks is indicated, as these waters are oversaturated with diopside, tremolite, talc, chrysotile, sepiolite and its precipitate. There is no clear evidence to show that the thermal waters of the west coast of India emerge directly from either marine evaporites or oil field waters. It is proposed that the majority of these thermal waters should have originated through interaction of an admixture of sea water and meteoric water with the local basalt flows at some elevated temperatures.« less

The U.S. Geological Survey's water resources program in New York

USGS Publications Warehouse

Wiltshire, Denise A.

1983-01-01

The U.S. Geological Survey performs hydrologic investigations throughout the United States to appraise the Nation's water resources. The Geological Survey began its water-resources investigations in New York in 1895. To meet the objectives of assessing New York's water resources, the Geological Survey (1) monitors the quantity and quality of surface and ground water, (2) conducts investigations of the occurrence, availability, and chemical quality of water in specific areas of the State, (3) develops methods and techniques of data-collection and interpretation, (4) provides scientific guidance to the research community, to Federal, State, and local governments, and to the public, and (5) disseminates data and results of research through reports, maps, news releases, conferences, and workshops. Many of the joint hydrologic investigations are performed by the Geological Survey in cooperation with State, county, and nonprofit organizations. The data collection network in New York includes nearly 200 gaging stations and 250 observation wells; chemical quality of water is measured at 260 sites. Data collected at these sites are published annually and are filed in the WATSTORE computer system. Some of the interpretive studies performed by the Geological Survey in New York include (1) determining the suitability of ground-water reservoirs for public-water supply in urban areas, (2) assessing geohydrologic impacts of leachate from hazardous waste sites on stream and ground-water quality, (3) evaluating the effects of precipitation quality and basin characteristics on streams and lakes, and (4) developing digital models of the hydrology of aquifers to simulate ground-water flow and the interaction between ground water and streams.

IPA (v1): a framework for agent-based modelling of soil water movement

NASA Astrophysics Data System (ADS)

Mewes, Benjamin; Schumann, Andreas H.

2018-06-01

In the last decade, agent-based modelling (ABM) became a popular modelling technique in social sciences, medicine, biology, and ecology. ABM was designed to simulate systems that are highly dynamic and sensitive to small variations in their composition and their state. As hydrological systems, and natural systems in general, often show dynamic and non-linear behaviour, ABM can be an appropriate way to model these systems. Nevertheless, only a few studies have utilized the ABM method for process-based modelling in hydrology. The percolation of water through the unsaturated soil is highly responsive to the current state of the soil system; small variations in composition lead to major changes in the transport system. Hence, we present a new approach for modelling the movement of water through a soil column: autonomous water agents that transport water through the soil while interacting with their environment as well as with other agents under physical laws.

Molecular and kinetic determinants of local anaesthetic action on sodium channels.

PubMed

French, R J; Zamponi, G W; Sierralta, I E

1998-11-23

(1) Local anaesthetics (LA) rely for their clinical actions on state-dependent inhibition of voltage-dependent sodium channels. (2) Single, batrachoxin-modified sodium channels in planar lipid bilayers allow direct observation of drug-channel interactions. Two modes of inhibition of single-channel current are observed: fast block of the open channels and prolongation of a long-lived closed state, some of whose properties resemble those of the inactivated state of unmodified channels. (3) Analogues of different parts of the LA molecule separately mimic each blocking mode: amines--fast block, and water-soluble aromatics--closed state prolongation. (4) Interaction between a mu-conotoxin derivative and diethylammonium indicate an intrapore site of fast, open-state block. (5) Site-directed mutagenesis studies suggest that hydrophobic residues in transmembrane segment 6 of repeat domain 4 of sodium channels are critical for both LA binding and stabilization of the inactivated state.

Migrating from Mexico and Sharing Pretend with Peers in the United States

ERIC Educational Resources Information Center

Howes, Carollee; Wishard Guerra, Alison G.; Zucker, Eleanor

2008-01-01

The intent of this study was to examine the development of peer interaction in low-income Mexican-heritage families in the United States. Eighty-eight children (44 girls) were observed and mothers interviewed when children were 14, 24, 36, and 54 months old. We used the Attachment Q-Set (Waters, 1990), the Peer Play Scale (Howes & Matheson, 1992),…

Dispersion Interactions between Urea and Nucleobases Contribute to the Destabilization of RNA by Urea in Aqueous Solution

PubMed Central

Kasavajhala, Koushik; Bikkina, Swetha; Patil, Indrajit; MacKerell, Alexander D.; Priyakumar, U. Deva

2015-01-01

Urea has long been used to investigate protein folding and, more recently, RNA folding. Studies have proposed that urea denatures RNA by participating in stacking interactions and hydrogen bonds with nucleic acid bases. In this study, the ability of urea to form unconventional stacking interactions with RNA bases is investigated using ab initio calculations (RI-MP2 and CCSD(T) methods with the aug-cc-pVDZ basis set). A total of 29 stable nucleobase-urea stacked complexes are identified in which the intermolecular interaction energies (up to −14 kcal/mol) are dominated by dispersion effects. Natural bond orbital (NBO) and atoms in molecules (AIM) calculations further confirm strong interactions between urea and nucleobases. Calculations on model systems with multiple urea and water molecules interacting with a guanine base lead to a hypothesis that urea molecules along with water are able to form cage-like structures capable of trapping nucleic acid bases in extrahelical states by forming both hydrogen bonded and dispersion interactions, thereby contributing to the unfolding of RNA in the presence of urea in aqueous solution. PMID:25668757

Charge Redistribution in the β-NAPHTHOL-WATER Complex as Measured by High Resolution Stark Spectroscopy in the Gas Phase.

NASA Astrophysics Data System (ADS)

Fleisher, Adam J.; Pratt, David W.; Cembran, Alessandro; Gao, Jiali

2010-06-01

The extensively studied photoacid β-naphthol exhibits a large decrease in pKa upon irradiation with ultraviolet light, in the condensed phase. β-naphthol is almost 10 million times more acidic in the excited electronic state, compared to the ground state. Motivated by this fact, we report here the measurement of the electronic dipole moments of the β-naphthol-water complex in both electronic states, from which estimates of the charge transfer from solute to solvent in both states will be made. Comparisons to ab initio and density functional theory calculations will also be reported. N. Mataga and T. Kubota, Molecular Interactions and Electronic Spectra (Marcel Dekker, New York, 1970). Y. Mo, J. Gao, S.D. Peyerimhoff, J. Chem. Phys. 112, 5530 (2000).

Embedded resource accounting for coupled natural-human systems: An application to water resource impacts of the western U.S. electrical energy trade

NASA Astrophysics Data System (ADS)

Ruddell, Benjamin L.; Adams, Elizabeth A.; Rushforth, Richard; Tidwell, Vincent C.

2014-10-01

In complex coupled natural-human systems (CNH), multitype networks link social, environmental, and economic systems with flows of matter, energy, information, and value. Embedded Resource Accounting (ERA) is a systems analysis framework that includes the indirect connections of a multitype CNH network. ERA is conditioned on perceived system boundaries, which may vary according to the accountant's point of view. Both direct and indirect impacts are implicit whenever two subnetworks interact in such a system; the ratio of two subnetworks' impacts is the embedded intensity. For trade in the services of water, this is understood as the indirect component of a water footprint, and as "virtual water" trade. ERA is a generalization of input-output, footprint, and substance flow methods, and is a type of life cycle analysis. This paper presents results for the water and electrical energy system in the western U.S. This system is dominated by California, which outsources the majority of its water footprint of electrical energy. Electricity trade increases total water consumption for electricity production in the western U.S. by 15% and shifts water use to water-stressed Colorado River Basin States. A systemic underaccounting for water footprints occurs because state-level processes discount a portion of the water footprint occurring outside of the state boundary.

Ringin' the water bell: dynamic modes of curved fluid sheets

NASA Astrophysics Data System (ADS)

Kolinski, John; Aharoni, Hillel; Fineberg, Jay; Sharon, Eran

2015-11-01

A water bell is formed by fluid flowing in a thin, coherent sheet in the shape of a bell. Experimentally, a water bell is created via the impact of a cylindrical jet on a flat surface. Its shape is set by the splash angle (the separation angle) of the resulting cylindrically symmetric water sheet. The separation angle is altered by adjusting the height of a lip surrounding the impact point, as in a water sprinkler. We drive the lip's height sinusoidally, altering the separation angle, and ringin' the water bell. This forcing generates disturbances on the steady-state water bell that propagate forward and backward in the fluid's reference frame at well-defined velocities, and interact, resulting in the emergence of an interference pattern unique to each steady-state geometry. We analytically model these dynamics by linearizing the amplitude of the bell's response about the underlying curved geometry. This simple model predicts the nodal structure over a wide range of steady-state water bell configurations and driving frequencies. Due to the curved water bell geometry, the nodal structure is quite complex; nevertheless, the predicted nodal structure agrees extremely well with the experimental data. When we drive the bell beyond perturbative separation angles, the nodal locations surprisingly persist, despite the strikingly altered underlying water bell shape. At extreme driving amplitudes the water sheet assumes a rich variety of tortuous, non-convex shapes; nevertheless, the fluid sheet remains intact.

Incorporating water table dynamics in climate modeling: 1. Water table observations and equilibrium water table simulations

NASA Astrophysics Data System (ADS)

Fan, Ying; Miguez-Macho, Gonzalo; Weaver, Christopher P.; Walko, Robert; Robock, Alan

2007-05-01

Soil moisture is a key participant in land-atmosphere interactions and an important determinant of terrestrial climate. In regions where the water table is shallow, soil moisture is coupled to the water table. This paper is the first of a two-part study to quantify this coupling and explore its implications in the context of climate modeling. We examine the observed water table depth in the lower 48 states of the United States in search of salient spatial and temporal features that are relevant to climate dynamics. As a means to interpolate and synthesize the scattered observations, we use a simple two-dimensional groundwater flow model to construct an equilibrium water table as a result of long-term climatic and geologic forcing. Model simulations suggest that the water table depth exhibits spatial organization at watershed, regional, and continental scales, which may have implications for the spatial organization of soil moisture at similar scales. The observations suggest that water table depth varies at diurnal, event, seasonal, and interannual scales, which may have implications for soil moisture memory at these scales.

Evaluation of aluminum phthalocyanine chloride and DNA interactions for the design of an advanced drug delivery system in photodynamic therapy.

PubMed

Jayme, Cristiano Ceron; Calori, Italo Rodrigo; Cunha, Elise Marques Freire; Tedesco, Antonio Claudio

2018-08-05

The aim of this study was to evaluate the interaction of aluminum phthalocyanine chloride (AlClPc) with double-stranded DNA. Absorption and fluorescence spectra, resonance light scattering, and circular dichroism were evaluated in water and water/ethanol mixtures with different concentrations of DNA or AlClPc. AlClPc showed a high ability to bind to DNA in both water and 4/6 water/ethanol mixture (v/v), with a majority of monomeric and aggregated initial forms of AlClPc, respectively. In this interaction, AlClPc bound preferentially to the grooves of DNA. The monomeric/aggregate state of AlClPc in DNA was dependent on the AlClPc/DNA ratio. At low concentrations of AlClPc, the interaction of AlClPc with few DNA sites caused a curvature in the DNA structure that provided a favorable environment for the intercalation of AlClPc aggregates. Increase in AlClPc concentration induced interactions with a high number of binding sites on DNA, which prevented bending and therefore aggregation of AlClPc molecules throughout the double-stranded DNA. These results are relevant to the understanding of the behavior and interaction of AlClPc with double-stranded DNA in the design of novel drug delivery systems for clinical application in photodynamic therapy as a new approach to treat skin or oral cancer, scars, or wound healing. Copyright © 2018 Elsevier B.V. All rights reserved.

Numerical investigation of shock induced bubble collapse in water

NASA Astrophysics Data System (ADS)

Apazidis, N.

2016-04-01

A semi-conservative, stable, interphase-capturing numerical scheme for shock propagation in heterogeneous systems is applied to the problem of shock propagation in liquid-gas systems. The scheme is based on the volume-fraction formulation of the equations of motion for liquid and gas phases with separate equations of state. The semi-conservative formulation of the governing equations ensures the absence of spurious pressure oscillations at the material interphases between liquid and gas. Interaction of a planar shock in water with a single spherical bubble as well as twin adjacent bubbles is investigated. Several stages of the interaction process are considered, including focusing of the transmitted shock within the deformed bubble, creation of a water-hammer shock as well as generation of high-speed liquid jet in the later stages of the process.

Structures and Spectroscopic Properties of F-(H2O) n with n = 1-10 Clusters from a Global Search Based On Density Functional Theory.

PubMed

Shi, Ruili; Wang, Pengju; Tang, Lingli; Huang, Xiaoming; Chen, Yonggang; Su, Yan; Zhao, Jijun

2018-04-05

Using a genetic algorithm incorporated in density functional theory, we explore the ground state structures of fluoride anion-water clusters F - (H 2 O) n with n = 1-10. The F - (H 2 O) n clusters prefer structures in which the F - anion remains at the surface of the structure and coordinates with four water molecules, as the F - (H 2 O) n clusters have strong F - -H 2 O interactions as well as strong hydrogen bonds between H 2 O molecules. The strong interaction between the F - anion and adjacent H 2 O molecule leads to a longer O-H distance in the adjacent molecule than in an individual water molecule. The simulated infrared (IR) spectra of the F - (H 2 O) 1-5 clusters obtained via second-order vibrational perturbation theory (VPT2) and including anharmonic effects reproduce the experimental results quite well. The strong interaction between the F - anion and water molecules results in a large redshift (600-2300 cm -1 ) of the adjacent O-H stretching mode. Natural bond orbital (NBO) analysis of the lowest-energy structures of the F - (H 2 O) 1-10 clusters illustrates that charge transfer from the lone pair electron orbital of F - to the antibonding orbital of the adjacent O-H is mainly responsible for the strong interaction between the F - anion and water molecules, which leads to distinctly different geometric and vibrational properties compared with neutral water clusters.

Separating para and ortho water.

PubMed

Horke, Daniel A; Chang, Yuan-Pin; Długołęcki, Karol; Küpper, Jochen

2014-10-27

Water exists as two nuclear-spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules, the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separated, and no pure para sample has been produced. Accordingly, little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. The production of isolated samples of both spin isomers is demonstrated in pure beams of para and ortho water in their respective absolute ground state. These single-quantum-state samples are ideal targets for unraveling spin-conversion mechanisms, for precision spectroscopy and fundamental symmetry-breaking studies, and for spin-enhanced applications, for example laboratory astrophysics and astrochemistry or hypersensitized NMR experiments. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strontium isotope geochemistry of groundwater in the central part of the Dakota (Great Plains) aquifer, USA

USGS Publications Warehouse

Gosselin, D.C.; Harvey, F.E.; Frost, C.; Stotler, R.; Macfarlane, P.A.

2004-01-01

The Dakota aquifer of the central and eastern Great Plains of the United States is an important source of water for municipal supplies, irrigation and industrial use. Although the regional flow system can be characterized generally as east to northeasterly from the Rocky Mountains towards the Missouri River, locally the flow systems are hydrologically complex. This study uses Sr isotopic data from groundwater and leached aquifer samples to document the complex subsystems within the Dakota aquifer in Nebraska and Kansas. The interaction of groundwater with the geologic material through which it flows has created spatial patterns in the isotopic measurements that are related to: long-term water-rock interaction, during which varying degrees of isotopic equilibrium between water and rock has been achieved; and the alteration of NaCl fluids by water-rock interaction. Specifically, Sr isotopic data distinguish brines from Kansas and western Nebraska from those in eastern Nebraska: the former are interpreted to reflect interaction with Permian rocks, whereas the latter record interaction with Pennsylvanian rocks. The Sr isotopic composition of groundwater from other parts of Nebraska and Kansas are a function of the dynamic interaction between groundwater and unlithified sediments (e.g., glacial till and loess), followed by interaction with oxidized and unoxidized sediments within the Dakota Formation. This study illustrates the power of combining Sr chemistry with more conventional geochemical data to obtain a more complete understanding of groundwater flow systems within regional aquifer systems where extensive monitoring networks do not exist. ?? 2003 Elsevier Ltd. All rights reserved.

A statistical mechanical theory for a two-dimensional model of water

PubMed Central

Urbic, Tomaz; Dill, Ken A.

2010-01-01

We develop a statistical mechanical model for the thermal and volumetric properties of waterlike fluids. Each water molecule is a two-dimensional disk with three hydrogen-bonding arms. Each water interacts with neighboring waters through a van der Waals interaction and an orientation-dependent hydrogen-bonding interaction. This model, which is largely analytical, is a variant of the Truskett and Dill (TD) treatment of the “Mercedes-Benz” (MB) model. The present model gives better predictions than TD for hydrogen-bond populations in liquid water by distinguishing strong cooperative hydrogen bonds from weaker ones. We explore properties versus temperature T and pressure p. We find that the volumetric and thermal properties follow the same trends with T as real water and are in good general agreement with Monte Carlo simulations of MB water, including the density anomaly, the minimum in the isothermal compressibility, and the decreased number of hydrogen bonds for increasing temperature. The model reproduces that pressure squeezes out water’s heat capacity and leads to a negative thermal expansion coefficient at low temperatures. In terms of water structuring, the variance in hydrogen-bonding angles increases with both T and p, while the variance in water density increases with T but decreases with p. Hydrogen bonding is an energy storage mechanism that leads to water’s large heat capacity (for its size) and to the fragility in its cagelike structures, which are easily melted by temperature and pressure to a more van der Waals-like liquid state. PMID:20550408

The dominant interaction between peptide and urea is electrostatic in nature: a molecular dynamics simulation study.

PubMed

Tobi, Dror; Elber, Ron; Thirumalai, Devarajan

2003-03-01

The conformational equilibrium of a blocked valine peptide in water and aqueous urea solution is studied using molecular dynamics simulations. Pair correlation functions indicate enhanced concentration of urea near the peptide. Stronger hydrogen bonding of urea-peptide compared to water-peptide is observed with preference for helical conformation. The potential of mean force, computed using umbrella sampling, shows only small differences between urea and water solvation that are difficult to quantify. The changes in solvent structure around the peptide are explained by favorable electrostatic interactions (hydrogen bonds) of urea with the peptide backbone. There is no evidence for significant changes in hydrophobic interactions in the two conformations of the peptide in urea solution. Our simulations suggest that urea denatures proteins by preferentially forming hydrogen bonds to the peptide backbone, reducing the barrier for exposing protein residues to the solvent, and reaching the unfolded state. Copyright 2003 Wiley Periodicals, Inc. Biopolymers: 359-369, 2003

Mapping hydration dynamics and coupled water-protein fluctuations around a protein surface

NASA Astrophysics Data System (ADS)

Zhang, Luyuan; Wang, Lijuan; Kao, Ya-Ting; Qiu, Weihong; Yang, Yi; Okobiah, Oghaghare; Zhong, Dongping

2009-03-01

Elucidation of the molecular mechanism of water-protein interactions is critical to understanding many fundamental aspects of protein science, such as protein folding and misfolding and enzyme catalysis. We recently carried out a global mapping of protein-surface hydration dynamics around a globular α-helical protein apomyoglobin. The intrinsic optical probe tryptophan was employed to scan the protein surface one at a time by site-specific mutagenesis. With femtosecond resolution, we mapped out the dynamics of water-protein interactions with more than 20 mutants and for two states, native and molten globular. A robust bimodal distribution of time scales was observed, representing two types of water motions: local relaxation and protein-coupled fluctuations. The time scales show a strong correlation with the local protein structural rigidity and chemical identity. We also resolved two distinct contributions to the overall Stokes-shifts from the two time scales. These results are significant to understanding the role of hydration water on protein structural stability, dynamics and function.

A Coupled Modeling Framework of the Co-evolution of Humans and Water: Case Study of Tarim River Basin, Western China

NASA Astrophysics Data System (ADS)

Liu, D.; Tian, F.; Lin, M.; Sivapalan, M.

2014-12-01

The complex interactions and feedbacks between humans and water are very essential issues but are poorly understood in the newly proposed discipline of socio-hydrology (Sivapalan et al., 2012). An exploratory model with the appropriate level of simplification can be valuable to improve our understanding of the co-evolution and self-organization of socio-hydrological systems driven by interactions and feedbacks operating at different scales. In this study, a simple coupled modeling framework for socio-hydrology co-evolution is developed for the Tarim River Basin in Western China, and is used to illustrate the explanatory power of such a model. The study area is the mainstream of the Tarim River, which is divided into two modeling units. The socio-hydrological system is composed of four parts, i.e., social sub-system, economic sub-system, ecological sub-system, and hydrological sub-system. In each modeling unit, four coupled ordinary differential equations are used to simulate the dynamics of the social sub-system represented by human population, the economic sub-system represented by irrigated crop area, the ecological sub-system represented by natural vegetation cover and the hydrological sub-system represented by stream discharge. The coupling and feedback processes of the four dominant sub-systems (and correspondingly four state variables) are integrated into several internal system characteristics interactively and jointly determined by themselves and by other coupled systems. For example, the stream discharge is coupled to the irrigated crop area by the colonization rate and mortality rate of the irrigated crop area in the upper reach and the irrigated area is coupled to stream discharge through irrigation water consumption. The co-evolution of the Tarim socio-hydrological system is then analyzed within this modeling framework to gain insights into the overall system dynamics and its sensitivity to the external drivers and internal system variables. In the modeling framework, the state of each subsystem is holistically described by one state variable and the framework is flexible enough to comprise more processes and constitutive relationships if they are needed to illustrate the interaction and feedback mechanisms of the human-water system.

Analysis of state and federal regulatory regimes potentially governing the extraction of water from carbon storage reservoirs in the United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, Jenna N.; Harto, Christopher B.; Clark, Corrie E.

Extracted water—water brought to the surface of the ground during carbon capture and sequestration (CCS) projects to create additional room for carbon dioxide injection—exists in a murky legal environment. As part of a broader attempt to identify the complex interactions between water resource policies and CCS, an analysis was undertaken at both the state and the federal level to scope the policy environments surrounding extracted water policies and laws. Six states (California, Illinois, Mississippi, Montana, North Dakota, and Texas) were chosen for this analysis because either active CCS work is currently underway, or the potential exists for future work. Although regulationmore » of extracted waters could potentially occur at many points along the CCS life cycle, this paper focuses on regulation that may apply when the water is withdrawn—that is, accessed and removed from the saline aquifer—and when it is re-injected in a close but unconnected aquifer. It was found that no regulations exist for this source specifically. In addition, greater input is needed from regulators and policy makers in terms of defining this resource. In particular, regulation of extracted waters (and CCS activities broadly) often overlaps with the management of fluids produced during oil and gas development. Many regulations would apply to extracted waters if they were classified as such. Therefore, correct categorization is key as the industry in this space continues to grow.« less

Application of a Groundwater Modeling Tool for Managing Hydrologically Connected Area in State of Nebraska, US

NASA Astrophysics Data System (ADS)

Li, R.; Flyr, B.; Bradley, J.; Pun, M.; Schneider, J.; Wietjes, J.; Chinta, S.

2014-12-01

Determination of the nature and degree of hydrologically connected groundwater and surface water resources is of paramount importance to integrated water management within the State of Nebraska to understand the impact of water uses on available supplies, such as depletion of streams and aquifers caused by groundwater pumping. The ability to quantify effects of surface water-groundwater hydrologic connection and interactions, is regarded as one of the most important steps towards effectively managing water resources in Nebraska and provides the basis for designating management areas. Designation of management areas allows the state and other management entities to focus various efforts and resources towards those projects that have the greatest impact to water users. Nebraska Department of Natural Resources (NDNR) developed a groundwater modeling tool, Cycle Well Analysis, to determine the areas defined to have a high degree of connectivity between groundwater and surface water (in accordance with the state regulations). This tool features two graphic user interfaces to allow the analysis to be fully compatible with most MODFLOW-based numerical groundwater models currently utilized by NDNR. Case studies showed that the tool, in combination of Geographic Information Systems (GIS), can be used to quantify the degree of stream depletion and delineate the boundary of hydrologically connected areas within different political boundaries and subbasins in Nebraska. This approach may be applied to other regions with similar background and need for integrated water management.

Dynamics of water bound to crystalline cellulose

DOE Office of Scientific and Technical Information (OSTI.GOV)

O’Neill, Hugh; Pingali, Sai Venkatesh; Petridis, Loukas

Interactions of water with cellulose are of both fundamental and technological importance. Here, we characterize the properties of water associated with cellulose using deuterium labeling, neutron scattering and molecular dynamics simulation. Quasi-elastic neutron scattering provided quantitative details about the dynamical relaxation processes that occur and was supported by structural characterization using small-angle neutron scattering and X-ray diffraction. We can unambiguously detect two populations of water associated with cellulose. The first is “non-freezing bound” water that gradually becomes mobile with increasing temperature and can be related to surface water. The second population is consistent with confined water that abruptly becomes mobilemore » at ~260 K, and can be attributed to water that accumulates in the narrow spaces between the microfibrils. Quantitative analysis of the QENS data showed that, at 250 K, the water diffusion coefficient was 0.85 ± 0.04 × 10-10 m2sec-1 and increased to 1.77 ± 0.09 × 10-10 m2sec-1 at 265 K. MD simulations are in excellent agreement with the experiments and support the interpretation that water associated with cellulose exists in two dynamical populations. Our results provide clarity to previous work investigating the states of bound water and provide a new approach for probing water interactions with lignocellulose materials.« less

Soy protein polymers: Enhancing the water stability property

NASA Astrophysics Data System (ADS)

Srinivasan, Gowrishankar

Soy protein based plastics have been processed in the past by researchers for various short-term applications; however a common issue is the high water sensitivity of these plastics. This work concentrates on resolving this water sensitivity issue of soy protein polymers by employing chemical and mechanical interaction at the molecular level during extrusion. The primary chemical interactions employed were anhydride chemistries such as maleic anhydride (MA), phthalic anhydride (PTA), and butylated hydroxyanisole (BHA). These were respectively used in conjunction with glycerol as a plasticizer to produce relatively water stable soy protein based plastics. Formulations with varying additive levels of the chemistries were extruded and injection molded to form the samples for characterization. The additive levels of anhydrides were varied between 3-10% tw/tw (total mass). Results indicated that phthalic anhydride formulations resulted in highest water stability. Plastic formulations with concentration up to 10% phthalic anhydride were observed to have water absorption as low as 21.5% after 24 hrs of exposure to water with respect to 250% for the control formulation. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize and confirm the fundamental mechanisms of water stability achieved by phthalic and maleic anhydride chemistries. In addition, the anhydride formulations were modified by inclusion of cotton fibers and pretreated cotton powder in order to improve mechanical properties. The incorporation of cotton fibers improved the dry strength by 18%, but did not significantly improve the wet state strength of the plastics. It was also observed that the butylated-hydroxy anisole (BHA) formulation exhibited high extension values in the dry state and had inferior water absorption properties in comparison with anhydride formulations.

Updating CMAQ secondary organic aerosol properties relevant for aerosol water interactions

EPA Science Inventory

Properties of secondary organic aerosol (SOA) compounds in CMAQ are updated with state-of-the-science estimates from structure activity relationships to provide consistency among volatility, molecular weight, degree of oxygenation, and solubility/hygroscopicity. These updated pro...

Towards improved solubility of poorly water-soluble drugs: cryogenic co-grinding of piroxicam with carrier polymers.

PubMed

Penkina, Anna; Semjonov, Kristian; Hakola, Maija; Vuorinen, Sirpa; Repo, Timo; Yliruusi, Jouko; Aruväli, Jaan; Kogermann, Karin; Veski, Peep; Heinämäki, Jyrki

2016-01-01

Amorphous solid dispersions (SDs) open up exciting opportunities in formulating poorly water-soluble active pharmaceutical ingredients (APIs). In the present study, novel catalytic pretreated softwood cellulose (CPSC) and polyvinylpyrrolidone (PVP) were investigated as carrier polymers for preparing and stabilizing cryogenic co-ground SDs of poorly water-soluble piroxicam (PRX). CPSC was isolated from pine wood (Pinus sylvestris). Raman and Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) were used for characterizing the solid-state changes and drug-polymer interactions. High-resolution scanning electron microscope (SEM) was used to analyze the particle size and surface morphology of starting materials and final cryogenic co-ground SDs. In addition, the molecular aspects of drug-polymer interactions and stabilization mechanisms are presented. The results showed that the carrier polymer influenced both the degree of amorphization of PRX and stabilization against crystallization. The cryogenic co-ground SDs prepared from PVP showed an enhanced dissolution rate of PRX, while the corresponding SDs prepared from CPSC exhibited a clear sustained release behavior. In conclusion, cryogenic co-grinding provides a versatile method for preparing amorphous SDs of poorly water-soluble APIs. The solid-state stability and dissolution behavior of such co-ground SDs are to a great extent dependent on the carrier polymer used.

Surface-Water Conditions in Georgia, Water Year 2005

USGS Publications Warehouse

Painter, Jaime A.; Landers, Mark N.

2007-01-01

INTRODUCTION The U.S. Geological Survey (USGS) Georgia Water Science Center-in cooperation with Federal, State, and local agencies-collected surface-water streamflow, water-quality, and ecological data during the 2005 Water Year (October 1, 2004-September 30, 2005). These data were compiled into layers of an interactive ArcReaderTM published map document (pmf). ArcReaderTM is a product of Environmental Systems Research Institute, Inc (ESRI?). Datasets represented on the interactive map are * continuous daily mean streamflow * continuous daily mean water levels * continuous daily total precipitation * continuous daily water quality (water temperature, specific conductance dissolved oxygen, pH, and turbidity) * noncontinuous peak streamflow * miscellaneous streamflow measurements * lake or reservoir elevation * periodic surface-water quality * periodic ecological data * historical continuous daily mean streamflow discontinued prior to the 2005 water year The map interface provides the ability to identify a station in spatial reference to the political boundaries of the State of Georgia and other features-such as major streams, major roads, and other collection stations. Each station is hyperlinked to a station summary showing seasonal and annual stream characteristics for the current year and for the period of record. For continuous discharge stations, the station summary includes a one page graphical summary page containing five graphs, a station map, and a photograph of the station. The graphs provide a quick overview of the current and period-of-record hydrologic conditions of the station by providing a daily mean discharge graph for the water year, monthly statistics graph for the water year and period of record, an annual mean streamflow graph for the period of record, an annual minimum 7-day average streamflow graph for the period of record, and an annual peak streamflow graph for the period of record. Additionally, data can be accessed through the layer's link to the National Water Inventory System Web (NWISWeb) Interface.

Understanding the Dynamic System of Terrorist-Government Interaction

DTIC Science & Technology

2003-03-01

organizations out of support or for services rendered (Department of State, 2002:65; Wallace, 2003:2). However, financial support does not have to be in...America’s critical infrastructure encompasses a large number of sectors[:]” agriculture, food, water, public health, emergency services , government...military, international law enforcement community, or the U.S. or international intelligence services (Department of State, 2002:vii-xiii). In fact

A study of N-methylacetamide in water clusters: based on atom-bond electronegativity equalization method fused into molecular mechanics.

PubMed

Yang, Zhong-Zhi; Qian, Ping

2006-08-14

N-methylacetamide (NMA) is a very interesting compound and often serves as a model of the peptide bond. The interaction between NMA and water provides a convenient prototype for the solvation of the peptides in aqueous solutions. Here we present NMA-water potential model based on atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM) that is to take ABEEM charges of all atoms, bonds, and lone-pair electrons of NMA and water molecules into the electrostatic interaction term in molecular mechanics. The model has the following characters: (1)it allows the charges in system to fluctuate responding to the ambient environment; (2) for two major types of intermolecular hydrogen bonds, which are the hydrogen bond forming between the lone-pair electron on amide oxygen and the water hydrogen, and the one forming between the lone-pair electron on water oxygen and the amide hydrogen, we take special treatments in describing the electrostatic interaction by the use of the parameters k(lpO=, H) and k(lpO(-), HN(-)), respectively. The newly constructed potential model based on ABEEM/MM is first applied to amide-water clusters and reproduces gas-phase state properties of NMA(H(2)O)(n) (n=1-3) including optimal structures, dipole moments, ABEEM charge distributions, energy difference of the isolated trans- and cis-NMA, interaction energies, hydrogen bonding cooperative effects, and so on, whose results show the good agreement with those measured by available experiments and calculated by ab initio methods. In order to further test the reasonableness of this model and the correctness and transferability of the parameters, many static properties of the larger NMA-water complexes NMA(H(2)O)(n) (n=4-6) are also studied including optimal structures and interaction energies. The results also show fair consistency with those of our quantum chemistry calculations.

Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States

USGS Publications Warehouse

Payn, R.A.; Gooseff, M.N.; McGlynn, B.L.; Bencala, K.E.; Wondzell, S.M.

2009-01-01

Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface.

Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States

USGS Publications Warehouse

Payn, R.A.; Gooseff, M.N.; McGlynn, B.L.; Bencala, K.E.; Wondzell, S.M.

2009-01-01

Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface. Copyright 2009 by the American Geophysical Union.

Signatures of Solvation Thermodynamics in Spectra of Intermolecular Vibrations

PubMed Central

2017-01-01

This study explores the thermodynamic and vibrational properties of water in the three-dimensional environment of solvated ions and small molecules using molecular simulations. The spectrum of intermolecular vibrations in liquid solvents provides detailed information on the shape of the local potential energy surface, which in turn determines local thermodynamic properties such as the entropy. Here, we extract this information using a spatially resolved extension of the two-phase thermodynamics method to estimate hydration water entropies based on the local vibrational density of states (3D-2PT). Combined with an analysis of solute–water and water–water interaction energies, this allows us to resolve local contributions to the solvation enthalpy, entropy, and free energy. We use this approach to study effects of ions on their surrounding water hydrogen bond network, its spectrum of intermolecular vibrations, and resulting thermodynamic properties. In the three-dimensional environment of polar and nonpolar functional groups of molecular solutes, we identify distinct hydration water species and classify them by their characteristic vibrational density of states and molecular entropies. In each case, we are able to assign variations in local hydration water entropies to specific changes in the spectrum of intermolecular vibrations. This provides an important link for the thermodynamic interpretation of vibrational spectra that are accessible to far-infrared absorption and Raman spectroscopy experiments. Our analysis provides unique microscopic details regarding the hydration of hydrophobic and hydrophilic functional groups, which enable us to identify interactions and molecular degrees of freedom that determine relevant contributions to the solvation entropy and consequently the free energy. PMID:28783431

Switchgrass growth and pine-switchgrass interactions in established intercropping systems

DOE PAGES

Tian, Shiying; Cacho, Julian F.; Youssef, Mohamed A.; ...

2016-06-22

Intercropping switchgrass ( Panicum virgatum L.) with loblolly pine ( Pinus taeda L.) has been proposed for producing bioenergy feedstock in the southeastern United States. This study investigated switchgrass growth and pine–switchgrass interactions at two established experimental fields (7-year-old Lenoir site and 5-year-old Carteret site) located on the coastal plain of eastern United States. Position effects (edge and center of switchgrass alley in intercropping plots) and treatment effects (intercropping vs. grass-only) on above ground switchgrass growth were evaluated. Interspecific interactions with respect to capturing resources (light, soil water, and nitrogen) were investigated by measuring photosynthetically active radiation (PAR) above grassmore » canopy, soil moisture, and soil mineral nitrogen contents. Switchgrass growth was significantly (P = 0.001) affected by treatments in Lenoir and by position (P < 0.0001) in both study sites. Relative to the center, PAR above grass canopy at edge in both sites was about 48% less during the growing season. Soil water content during the growing season at the edge of grass alley was significantly (P = 0.0001) lower by 23% than at the center in Lenoir, while no significant (P = 0.42) difference was observed in Carteret, in spite of more grass growth at center at both sites. Soil mineral nitrogen content at the center of intercropping plots in Lenoir (no fertilization during 2015) was significantly (P < 0.07) lower than at the edge during the peak of growing season (June, July, and August), but not during early and late parts of growing season (May, September, and November). Position effects on soil water and mineral nitrogen were less evident under conditions with higher external inputs (rainfall and fertilization) and lower plant uptake during nongrowing seasons. Here, results from this study contributed to a better understanding of above- and belowground pine–switchgrass interactions which is necessary to properly manage this new cultivation system for bioenergy production in the southeastern United States.« less

Toward Effective Water Pipe Tobacco Control Policy in the United States: Synthesis of Federal, State, and Local Policy Texts.

PubMed

Colditz, Jason B; Ton, Jessica N; James, A Everette; Primack, Brian A

2017-07-01

Water pipe tobacco smoking (WTS) is growing in popularity among U.S. young adults and is associated with health risks similar to those of cigarette smoking. The purpose of this study is to examine existing tobacco control policies (TCPs) in order to investigate how they engage WTS. A systematic synthesis of content and legal interactions among federal, state, and local TCP documents. Pennsylvania, which represents a politically and demographically diverse microcosm of the United States. No human subjects. Federal and state TCPs were retrieved via public legal repositories. Local policy searches were conducted via county/municipal Web sites, inclusive of 13 localities that had autonomous health departments or existing TCPs based on a National Cancer Institute report. Full-text TCPs were double coded within a grounded theory framework for health policy analysis. Emergent codes were used to compare and contrast policy texts and to examine legal interactions among TCPs. Examination of policy categories including youth access, use restrictions, and taxation revealed WTS as largely omitted from current TCPs. WTS was sometimes addressed as an "other" tobacco product under older TCPs, though ambiguities in language led to questionable enforceability. State preemptions have rolled back or prevented well-tailored reforms at the local level. Federal preemptions have likewise constrained state TCPs. Outdated, preempted, and unclear policies limit the extent to which TCPs engage WTS. Health advocates might target these aspects of TCP reform.

THE ENVIRONMENTAL PROTECTION AGENCY'S WATERSHED MANAGEMENT RESEARCH PROGRAM: AN OVERVIEW

EPA Science Inventory

The Environmental Protection Agency (EPA) has directed much attention to watersheds and water quality during its tenure as the United States Federal Agency charged with protection of human health and the environment. Watershed research as a vehicle to understand the interaction ...

Active site dynamics of ribonuclease.

PubMed Central

Brünger, A T; Brooks, C L; Karplus, M

1985-01-01

The stochastic boundary molecular dynamics method is used to study the structure, dynamics, and energetics of the solvated active site of bovine pancreatic ribonuclease A. Simulations of the native enzyme and of the enzyme complexed with the dinucleotide substrate CpA and the transition-state analog uridine vanadate are compared. Structural features and dynamical couplings for ribonuclease residues found in the simulation are consistent with experimental data. Water molecules, most of which are not observed in crystallographic studies, are shown to play an important role in the active site. Hydrogen bonding of residues with water molecules in the free enzyme is found to mimic the substrate-enzyme interactions of residues involved in binding. Networks of water stabilize the cluster of positively charged active site residues. Correlated fluctuations between the uridine vanadate complex and the distant lysine residues are mediated through water and may indicate a possible role for these residues in stabilizing the transition state. Images PMID:3866234

Inelastic electron injection in a water chain

PubMed Central

Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.

2017-01-01

Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage. Low-energy electrons are one of the main secondary species and electron-phonon interaction plays a fundamental role in their dynamics. We have developed a method to capture the electron-phonon inelastic energy exchange in real time and have used it to inject electrons into a simple system that models a biological environment, a water chain. We simulated both an incoming electron pulse and a steady stream of electrons and found that electrons with energies just outside bands of excited molecular states can enter the chain through phonon emission or absorption. Furthermore, this phonon-assisted dynamical behaviour shows great sensitivity to the vibrational temperature, highlighting a crucial controlling factor for the injection and propagation of electrons in water. PMID:28350013

First measurement of the νμ charged-current cross section on a water target without pions in the final state

NASA Astrophysics Data System (ADS)

Abe, K.; Amey, J.; Andreopoulos, C.; Antonova, M.; Aoki, S.; Ariga, A.; Ashida, Y.; Ban, S.; Barbi, M.; Barker, G. J.; Barr, G.; Barry, C.; Batkiewicz, M.; Berardi, V.; Berkman, S.; Bhadra, S.; Bienstock, S.; Blondel, A.; Bolognesi, S.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buizza Avanzini, M.; Calland, R. G.; Campbell, T.; Cao, S.; Cartwright, S. L.; Catanesi, M. G.; Cervera, A.; Chappell, A.; Checchia, C.; Cherdack, D.; Chikuma, N.; Christodoulou, G.; Coleman, J.; Collazuol, G.; Coplowe, D.; Cudd, A.; Dabrowska, A.; De Rosa, G.; Dealtry, T.; Denner, P. F.; Dennis, S. R.; Densham, C.; Di Lodovico, F.; Dolan, S.; Drapier, O.; Duffy, K. E.; Dumarchez, J.; Dunne, P.; Emery-Schrenk, S.; Ereditato, A.; Feusels, T.; Finch, A. J.; Fiorentini, G. A.; Friend, M.; Fujii, Y.; Fukuda, D.; Fukuda, Y.; Garcia, A.; Giganti, C.; Gizzarelli, F.; Golan, T.; Gonin, M.; Hadley, D. R.; Haegel, L.; Haigh, J. T.; Hansen, D.; Harada, J.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayashino, T.; Hayato, Y.; Hillairet, A.; Hiraki, T.; Hiramoto, A.; Hirota, S.; Hogan, M.; Holeczek, J.; Hosomi, F.; Huang, K.; Ichikawa, A. K.; Ikeda, M.; Imber, J.; Insler, J.; Intonti, R. A.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Izmaylov, A.; Jamieson, B.; Jiang, M.; Johnson, S.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Karlen, D.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kim, H.; Kim, J.; King, S.; Kisiel, J.; Knight, A.; Knox, A.; Kobayashi, T.; Koch, L.; Koga, T.; Koller, P. P.; Konaka, A.; Kormos, L. L.; Koshio, Y.; Kowalik, K.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Lamont, I.; Lamoureux, M.; Lasorak, P.; Laveder, M.; Lawe, M.; Licciardi, M.; Lindner, T.; Liptak, Z. J.; Litchfield, R. P.; Li, X.; Longhin, A.; Lopez, J. P.; Lou, T.; Ludovici, L.; Lu, X.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Maret, L.; Marino, A. D.; Martin, J. F.; Martins, P.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Ma, W. Y.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Mefodiev, A.; Metelko, C.; Mezzetto, M.; Minamino, A.; Mineev, O.; Mine, S.; Missert, A.; Miura, M.; Moriyama, S.; Morrison, J.; Mueller, Th. A.; Nakadaira, T.; Nakahata, M.; Nakamura, K. G.; Nakamura, K.; Nakamura, K. D.; Nakanishi, Y.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nantais, C.; Nielsen, C.; Nishikawa, K.; Nishimura, Y.; Novella, P.; Nowak, J.; O'Keeffe, H. M.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Ovsyannikova, T.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Patel, N. D.; Paudyal, P.; Pavin, M.; Payne, D.; Petrov, Y.; Pickering, L.; Pinzon Guerra, E. S.; Pistillo, C.; Popov, B.; Posiadala-Zezula, M.; Poutissou, J.-M.; Pritchard, A.; Przewlocki, P.; Quilain, B.; Radermacher, T.; Radicioni, E.; Ratoff, P. N.; Rayner, M. A.; Reinherz-Aronis, E.; Riccio, C.; Rondio, E.; Rossi, B.; Roth, S.; Ruggeri, A. C.; Rychter, A.; Sakashita, K.; Sánchez, F.; Scantamburlo, E.; Scholberg, K.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shah, R.; Shaikhiev, A.; Shaker, F.; Shaw, D.; Shiozawa, M.; Shirahige, T.; Smy, M.; Sobczyk, J. T.; Sobel, H.; Steinmann, J.; Stewart, T.; Stowell, P.; Suda, Y.; Suvorov, S.; Suzuki, A.; Suzuki, S. Y.; Suzuki, Y.; Tacik, R.; Tada, M.; Takeda, A.; Takeuchi, Y.; Tamura, R.; Tanaka, H. K.; Tanaka, H. A.; Thakore, T.; Thompson, L. F.; Tobayama, S.; Toki, W.; Tomura, T.; Tsukamoto, T.; Tzanov, M.; Vagins, M.; Vallari, Z.; Vasseur, G.; Vilela, C.; Vladisavljevic, T.; Wachala, T.; Walter, C. W.; Wark, D.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilking, M. J.; Wilkinson, C.; Wilson, J. R.; Wilson, R. J.; Wret, C.; Yamada, Y.; Yamamoto, K.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; T2K Collaboration

2018-01-01

This paper reports the first differential measurement of the charged-current interaction cross section of νμ on water with no pions in the final state. This flux-averaged measurement has been made using the T2K experiment's off-axis near detector, and is reported in doubly differential bins of muon momentum and angle. The flux-averaged total cross section in a restricted region of phase space was found to be σ =(0.95 ±0.08 (stat) ±0.06 (det syst)±0.04 (model syst)±0.08 (flux ))×10-38 cm2/n .

Water resources planning for rivers draining into Mobile Bay

NASA Technical Reports Server (NTRS)

April, G. C.

1976-01-01

The application of remote sensing, automatic data processing, modeling and other aerospace related technologies to hydrological engineering and water resource management are discussed for the entire river drainage system which feeds the Mobile Bay estuary. The adaptation and implementation of existing mathematical modeling methods are investigated for the purpose of describing the behavior of Mobile Bay. Of particular importance are the interactions that system variables such as river flow rate, wind direction and speed, and tidal state have on the water movement and quality within the bay system.

A 2H nuclear magnetic resonance study of the state of water in neat silica and zwitterionic stationary phases and its influence on the chromatographic retention characteristics in hydrophilic interaction high-performance liquid chromatography.

PubMed

Wikberg, Erika; Sparrman, Tobias; Viklund, Camilla; Jonsson, Tobias; Irgum, Knut

2011-09-23

2H NMR has been used as a tool for probing the state of water in hydrophilic stationary phases for liquid chromatography at temperatures between -80 and +4 °C. The fraction of water that remained unfrozen in four different neat silicas with nominal pore sizes between 60 and 300 Å, and in silicas with polymeric sulfobetaine zwitterionic functionalities prepared in different ways, could be determined by measurements of the line widths and temperature-corrected integrals of the 2H signals. The phase transitions detected during thawing made it possible to estimate the amount of non-freezable water in each phase. A distinct difference was seen between the neat and modified silicas tested. For the neat silicas, the relationship between the freezing point depression and their pore size followed the expected Gibbs-Thomson relationship. The polymeric stationary phases were found to contain considerably higher amounts of non-freezable water compared to the neat silica, which is attributed to the structural effect that the sulfobetaine polymers have on the water layer close to the stationary phase surface. The sulfobetaine stationary phases were used alongside the 100 Å silica to separate a number of polar compounds in hydrophilic interaction (HILIC) mode, and the retention characteristics could be explained in terms of the surface water structure, as well as by the porous properties of the stationary phases. This provides solid evidence supporting a partitioning mechanism, or at least of the existence of an immobilized layer of water into which partitioning could be occurring. Copyright © 2011 Elsevier B.V. All rights reserved.

Progress in studies on hydrological impacts of degrading permafrost in the Source Area of Yellow River on NE Qinghai-Tibet Plateau, SW China

NASA Astrophysics Data System (ADS)

Jin, H.; Ma, Q.; Jin, X.

2017-12-01

Permafrost degradation substantially impacts hydrological processes in the Source Area of the Yellow River (SAYR). Deepening active layer has directly led to a reduction of surface runoffs, alters the generation and dynamics of slope runoffs and groundwater, leading to a deepening of groundwater flow paths. At present, however, there is only a limited understanding of the hydrological impact mechanisms of degrading permafrost. On the basis of analyzing and evaluating the current states, changing history and developing trends of climate, permafrost and hydrological processes, this program aims at further and better quantifying the nature of these mechanisms linking the degrading permafrost with changing hydrological processes. The key scientific themes for this research are the characterization of interactions between ground freezing-thawing and hydrogeology in the SAYR. For this study, a coupling is made between geothermal states and the occurrences of taliks in river systems, in order to understand how expanding taliks control groundwater and surface-water interactions and how these interactions might intensify or weaken when the climate warms and dries persistently. Numerical models include freeze-thaw dynamics coupled to groundwater and surface flow processes. For the proper parameterization of these models, field and laboratory studies are conducted with a focus on the SAYR. Geophysical investigations are employed for mapping permafrost distribution in relation to landscape elements. Boreholes and water wells and observation sites for the hydrothermal processes and water tables are used for establishing the current thermal state of frozen ground and talik and monitor their changes over time, and serve to ground-truth surface geophysical observations. Boreholes and wellbores, water wells and active layer sites have provided access to the permafrost and aquifer systems, allowing the dating of ground-water and -ice and soil strata for elucidating the regional hydrogeological system underlying the SAYR, and groundwater recharge mechanisms. The project plans to quantitatively study the impacting mechanisms of degrading frozen ground on changes in hydrological processes and systems in the SAYR.

Interactions of carbon and water cycles in north temperate wetlands: Modeling and observing the impact of a declining water table trend on regional biogeochemistry

Treesearch

Benjamin N. Sulman; Ankur R. Desai; D.S. Mackay; S. Samanta; B.D. Cook; N. Saliendra

2008-01-01

Terrestrial carbon fluxes represent a major source of uncertainty in estimates of future atmospheric greenhouse gas accumulation and consequently models of climate change. In the Upper Great Lakes states (Minnesota, Wisconsin, and Michigan), wetlands cover 14% of the land area, and compose up to one third of the land cover in the forest-wetland landscapes that dominate...

Controlled cohort evaluation of the LiveLighter mass media campaign's impact on adults' reported consumption of sugar-sweetened beverages.

PubMed

Morley, Belinda C; Niven, Philippa H; Dixon, Helen G; Swanson, Maurice G; McAleese, Alison B; Wakefield, Melanie A

2018-04-25

To evaluate the LiveLighter 'Sugary Drinks' campaign impact on awareness, knowledge and sugar-sweetened beverage (SSB) consumption. Cohort study with population surveys undertaken in intervention and comparison states at baseline (n=900 each), with 78% retention at follow-up (intervention: n=673; comparison: n=730). Analyses tested interactions by state (intervention, comparison) and time (baseline, follow-up). Adults aged 25-49 years residing in the Australian states of Victoria and South Australia. The 6-week mass media campaign ran in Victoria in October/November 2015. It focused on the contribution of SSBs to the development of visceral 'toxic fat', graphically depicted around vital organs, and ultimately serious disease. Paid television advertising was complemented by radio, cinema, online and social media advertising, and stakeholder and community engagement. Self-reported consumption of SSBs, artificially sweetened drinks and water. Campaign recall and recognition; knowledge of the health effects of overweight and SSB consumption; perceived impact of SSB consumption on body weight and of reduced consumption on health. A significant reduction in frequent SSB consumption was observed in the intervention state (intervention: 31% compared with 22%, comparison: 30% compared with 29%; interaction p<0.01). This was accompanied by evidence of increased water consumption (intervention: 66% compared with 73%; comparison: 68% compared with 67%; interaction p=0.09) among overweight/obese SSB consumers. This group also showed increased knowledge of the health effects of SSB consumption (intervention: 60% compared with 71%, comparison: 63% compared with 59%; interaction p<0.05) and some evidence of increased prevalence of self-referent thoughts about SSB's relationship to weight gain (intervention: 39% compared with 45%, comparison: 43% compared with 38%; interaction p=0.06). The findings provide evidence of reduced SSB consumption among adults in the target age range following the LiveLighter campaign. This is notable in a context where public health campaigns occur against a backdrop of heavy commercial product advertising promoting increased SSB consumption. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Incorporating human-water dynamics in a hyper-resolution land surface model

NASA Astrophysics Data System (ADS)

Vergopolan, N.; Chaney, N.; Wanders, N.; Sheffield, J.; Wood, E. F.

2017-12-01

The increasing demand for water, energy, and food is leading to unsustainable groundwater and surface water exploitation. As a result, the human interactions with the environment, through alteration of land and water resources dynamics, need to be reflected in hydrologic and land surface models (LSMs). Advancements in representing human-water dynamics still leave challenges related to the lack of water use data, water allocation algorithms, and modeling scales. This leads to an over-simplistic representation of human water use in large-scale models; this is in turn leads to an inability to capture extreme events signatures and to provide reliable information at stakeholder-level spatial scales. The emergence of hyper-resolution models allows one to address these challenges by simulating the hydrological processes and interactions with the human impacts at field scales. We integrated human-water dynamics into HydroBlocks - a hyper-resolution, field-scale resolving LSM. HydroBlocks explicitly solves the field-scale spatial heterogeneity of land surface processes through interacting hydrologic response units (HRUs); and its HRU-based model parallelization allows computationally efficient long-term simulations as well as ensemble predictions. The implemented human-water dynamics include groundwater and surface water abstraction to meet agricultural, domestic and industrial water demands. Furthermore, a supply-demand water allocation scheme based on relative costs helps to determine sectoral water use requirements and tradeoffs. A set of HydroBlocks simulations over the Midwest United States (daily, at 30-m spatial resolution for 30 years) are used to quantify the irrigation impacts on water availability. The model captures large reductions in total soil moisture and water table levels, as well as spatiotemporal changes in evapotranspiration and runoff peaks, with their intensity related to the adopted water management strategy. By incorporating human-water dynamics in a hyper-resolution LSM this work allows for progress on hydrological monitoring and predictions, as well as drought preparedness and water impact assessments at relevant decision-making scales.

Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling.

PubMed

Reid, Michael S; Kedzior, Stephanie A; Villalobos, Marco; Cranston, Emily D

2017-08-01

This work explores cellulose nanocrystal (CNC) thin films (<50 nm) and particle-particle interactions by investigating film swelling in aqueous solutions with varying ionic strength (1-100 mM). CNC film hydration was monitored in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

Design principles from multiscale simulations to predict nanostructure in self-assembling ionic liquids

DOE PAGES

Nebgen, Benjamin Tyler; Magurudeniya, Harsha D.; Kwock, Kevin Wen Chi; ...

2017-07-18

Molecular dynamics simulations (up to the nanoscale) were performed on the 3-methyl-1-pentylimidazolium ionic liquid cation paired with three anions; chloride, nitrate, and thiocyanate as aqueous mixtures, using the effective fragment potential (EFP) method, a computationally inexpensive way of modeling intermolecular interactions. The simulations provided insight (preferred geometries, radial distribution functions and theoretical proton NMR resonances) into the interactions within the ionic domain and are validated against 1H NMR spectroscopy and small- and wide-angle X-ray scattering experiments on 1-decyl-3-methylimidazolium. Ionic liquids containing thiocyanate typically resist gelation and form poorly ordered lamellar structures upon mixing with water. Conversely, chloride, a strongly coordinatingmore » anion, normally forms strong physical gels and produces well-ordered nanostructures adopting a variety of structural motifs over a very wide range of water compositions. Nitrate is intermediate in character, whereby upon dispersal in water it displays a range of viscosities and self-assembles into nanostructures with considerable variability in the fidelity of ordering and symmetry, as a function of water content in the binary mixtures. The observed changes in the macro and nanoscale characteristics were directly correlated to ionic domain structures and intermolecular interactions as theoretically predicted by the analysis of MD trajectories and calculated RDFs. Specifically, both chloride and nitrate are positioned in the plane of the cation. Anion to cation proximity is dependent on water content. Thiocyanate is more susceptible to water insertion into the second solvent shell. Experimental 1H NMR chemical shifts monitor the site-specific competition dependence with water content in the binary mixtures. As a result, thiocyanate preferentially sits above and below the aromatic ring plane, a state disallowing interaction with the protons on the imidazolium ring.« less

Design principles from multiscale simulations to predict nanostructure in self-assembling ionic liquids.

PubMed

Nebgen, Benjamin T; Magurudeniya, Harsha D; Kwock, Kevin W C; Ringstrand, Bryan S; Ahmed, Towfiq; Seifert, Sönke; Zhu, Jian-Xin; Tretiak, Sergei; Firestone, Millicent A

2017-12-14

Molecular dynamics simulations (up to the nanoscale) were performed on the 3-methyl-1-pentylimidazolium ionic liquid cation paired with three anions; chloride, nitrate, and thiocyanate as aqueous mixtures, using the effective fragment potential (EFP) method, a computationally inexpensive way of modeling intermolecular interactions. The simulations provided insight (preferred geometries, radial distribution functions and theoretical proton NMR resonances) into the interactions within the ionic domain and are validated against 1 H NMR spectroscopy and small- and wide-angle X-ray scattering experiments on 1-decyl-3-methylimidazolium. Ionic liquids containing thiocyanate typically resist gelation and form poorly ordered lamellar structures upon mixing with water. Conversely, chloride, a strongly coordinating anion, normally forms strong physical gels and produces well-ordered nanostructures adopting a variety of structural motifs over a very wide range of water compositions. Nitrate is intermediate in character, whereby upon dispersal in water it displays a range of viscosities and self-assembles into nanostructures with considerable variability in the fidelity of ordering and symmetry, as a function of water content in the binary mixtures. The observed changes in the macro and nanoscale characteristics were directly correlated to ionic domain structures and intermolecular interactions as theoretically predicted by the analysis of MD trajectories and calculated RDFs. Specifically, both chloride and nitrate are positioned in the plane of the cation. Anion to cation proximity is dependent on water content. Thiocyanate is more susceptible to water insertion into the second solvent shell. Experimental 1 H NMR chemical shifts monitor the site-specific competition dependence with water content in the binary mixtures. Thiocyanate preferentially sits above and below the aromatic ring plane, a state disallowing interaction with the protons on the imidazolium ring.

A water-soluble hybrid material of single-walled carbon nanotubes with an amphiphilic poly(phenyleneethynylene): preparation, characterization, and photovoltaic properties.

PubMed

Mao, Jie; Liu, Qian; Lv, Xin; Liu, Zunfeng; Huang, Yi; Ma, Yanfeng; Chen, Yongsheng; Yin, Shougen

2007-08-01

A novel rigid linear polymer poly(phenyleneethynylene) (PPE) was synthesized and the polymer exhibits good solubility in both water and common organic solvents. The interaction at both ground and excited state between this polymer and single-walled carbon nanotubes (SWNTs) was studied and a water-soluble nano-scale PPE/SWNTs hybrid was fabricated, where the water solubility of SWNTs was enhanced to 1.8 mg/ml. Steady state fluorescence spectra and fluorescence lifetime decay measurements showed that the emissions from PPEs in this hybrid at excited state were efficiently quenched by the attachment of SWNTs, where an efficient energy transfer happened from PPEs to SWNTs as the electron acceptor. Using this hybrid as the active layer we fabricated a photovoltaic cell with the bulk heterojunction configuration, and it showed a photoresponse with an open circuit voltage (Voc) of 105 mV and a short circuit current density (Isc) of 28.7 microA/cm2 under standard AM 1.5 illumination (100 mW/cm2).

People and water: Exploring the social-ecological condition of watersheds of the United States

EPA Science Inventory

A recent paradigm shift from purely biophysical towards social-ecological assessment of watersheds has been proposed to understand, monitor, and manipulate the myriad interactions between human well-being and the ecosystem services that watersheds provide. However, large-scale, q...

Mercury dynamics in a coastal plain watershed: insights from multiple models and empirical data

EPA Science Inventory

Interactions among atmospherically deposited mercury, abundant wetlands, and surface waters with elevated acidity and dissolved organic carbon (DOC) often lead to widespread mercury-related fish consumption advisories in the Coastal Plain of the southeastern United States (US). H...

Electrostatic effects in unfolded staphylococcal nuclease

PubMed Central

Fitzkee, Nicholas C.; García-Moreno E, Bertrand

2008-01-01

Structure-based calculations of pK a values and electrostatic free energies of proteins assume that electrostatic effects in the unfolded state are negligible. In light of experimental evidence showing that this assumption is invalid for many proteins, and with increasing awareness that the unfolded state is more structured and compact than previously thought, a detailed examination of electrostatic effects in unfolded proteins is warranted. Here we address this issue with structure-based calculations of electrostatic interactions in unfolded staphylococcal nuclease. The approach involves the generation of ensembles of structures representing the unfolded state, and calculation of Coulomb energies to Boltzmann weight the unfolded state ensembles. Four different structural models of the unfolded state were tested. Experimental proton binding data measured with a variant of nuclease that is unfolded under native conditions were used to establish the validity of the calculations. These calculations suggest that weak Coulomb interactions are an unavoidable property of unfolded proteins. At neutral pH, the interactions are too weak to organize the unfolded state; however, at extreme pH values, where the protein has a significant net charge, the combined action of a large number of weak repulsive interactions can lead to the expansion of the unfolded state. The calculated pK a values of ionizable groups in the unfolded state are similar but not identical to the values in small peptides in water. These studies suggest that the accuracy of structure-based calculations of electrostatic contributions to stability cannot be improved unless electrostatic effects in the unfolded state are calculated explicitly. PMID:18227429

Considering ionic state in modeling sorption of pharmaceuticals to sewage sludge.

PubMed

Rybacka, Aleksandra; Andersson, Patrik L

2016-12-01

Information on the partitioning of chemicals between particulate matter and water in sewage treatment plants (STPs) can be used to predict their subsequent environmental fate. However, this information can be challenging to acquire, especially for pharmaceuticals that are frequently present in ionized forms. This study investigated the relationship between the ionization state of active pharmaceutical ingredients (APIs) and their partitioning between water and sludge in STPs. We also investigated the underlying mechanisms of sludge sorption by using chemical descriptors based on ionized structures, and evaluated the usefulness of these descriptors in quantitative structure-property relationship (QSPR) modeling. K D values were collected for 110 APIs, which were classified as neutral, positive, or negative at pH 7. The models with the highest performance had the R 2 Y and Q 2 values of above 0.75 and 0.65, respectively. We found that the dominant intermolecular forces governing the interactions of neutral and positively charged APIs with sludge are hydrophobic, pi-pi, and dipole-dipole interactions, whereas the interactions of negatively charged APIs with sludge were mainly governed by covalent bonding as well as ion-ion, ion-dipole, and dipole-dipole interactions; hydrophobicity-driven interactions were rather unimportant. Including charge-related descriptors improved the models' performance by 5-10%, underlining the importance of electrostatic interactions. The use of descriptors calculated for ionized structures did not improve the model statistics for positive and negative APIs, but slightly increased model performance for neutral APIs. We attribute this to a better description of neutral zwitterions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Direct characterization of hydrophobic hydration during cold and pressure denaturation.

PubMed

Das, Payel; Matysiak, Silvina

2012-05-10

Cold and pressure denaturation are believed to have their molecular origin in hydrophobic interactions between nonpolar groups and water. However, the direct characterization of the temperature- and pressure-dependent variations of those interactions with atomistic simulations remains challenging. We investigated the role of solvent in the cold and pressure denaturation of a model hydrophobic 32-mer polymer by performing extensive coarse-grained molecular dynamics simulations including explicit solvation. Our simulations showed that the water-excluded folded state of this polymer is marginally stable and can be unfolded by heating or cooling, as well as by applying pressure, similar to globular proteins. We further detected essential population of a hairpin-like configuration prior to the collapse, which is consistently accompanied by a vapor bubble at the elbow of the kink. Increasing pressure suppresses formation of this vapor bubble by reducing water fluctuations in the hydration shell of the polymer, thus promoting unfolding. Further analysis revealed a slight reduction of water tetrahedrality in the polymer hydration shell compared to the bulk. Cold denaturation is driven by an enhanced tetrahedral ordering of hydration shell water than bulk water. At elevated pressures, the strikingly reduced fluctuations combined with the increase in interstitial water molecules in the polymer hydration shell contribute to weakening of hydrophobic interactions, thereby promoting pressure unfolding. These findings provide critical molecular insights into the changes in hydrophobic hydration during cold and pressure unfolding of a hydrophobic polymer, which is strongly related to the cold and pressure denaturation of globular proteins.

Reversible exposure of hydrophobic residues on albumin as a novel strategy for formulation of nanodelivery vehicles for taxanes

PubMed Central

Garro, AG; Beltramo, DM; Alasino, RV; Leonhard, V; Heredia, V; Bianco, ID

2011-01-01

Background: We report herein a novel strategy for the preparation of protein-based nanode-livery vehicles for hydrophobic active pharmaceutical ingredients. Methods: The procedure consisted of three steps, ie, exposure of hydrophobic residues of a protein to a pH-induced partial unfolding: interaction between hydrophobic residues on the protein and the hydrophobic active pharmaceutical ingredient, and a final step where the structure of the protein was reversed to a native-like state by returning to neutral pH. As proof of concept, the interaction of paclitaxel with partially unfolded states of human serum albumin was evaluated as a potential method for the preparation of water-soluble complexes of the taxane with albumin. Results: We found that paclitaxel readily binds to pH-induced partially unfolded albumin, leading to the formation of optically clear water-soluble complexes. The complexes thus formed were more stable in solution when the albumin native state was at least partially restored by neutralization of the solution to a pH around 7. It was also observed that the hydrodynamic radius of human serum albumin was only slightly increased after the cycle of pH changes, remaining in a monomeric state with a size according to paclitaxel binding. Furthermore, paclitaxel binding did not affect the overall exposure of charged groups of human serum albumin, as evaluated by its interaction with an ionic exchange resin. Conclusion: The in vitro biological activity of the complexes formed was qualitatively equivalent to that of a Cremophor®-based formulation. PMID:21822381

Vegetation pattern formation in a fog-dependent ecosystem.

PubMed

Borthagaray, Ana I; Fuentes, Miguel A; Marquet, Pablo A

2010-07-07

Vegetation pattern formation is a striking characteristic of several water-limited ecosystems around the world. Typically, they have been described on runoff-based ecosystems emphasizing local interactions between water, biomass interception, growth and dispersal. Here, we show that this situation is by no means general, as banded patterns in vegetation can emerge in areas without rainfall and in plants without functional root (the Bromeliad Tillandsia landbeckii) and where fog is the principal source of moisture. We show that a simple model based on the advection of fog-water by wind and its interception by the vegetation can reproduce banded patterns which agree with empirical patterns observed in the Coastal Atacama Desert. Our model predicts how the parameters may affect the conditions to form the banded pattern, showing a transition from a uniform vegetated state, at high water input or terrain slope to a desert state throughout intermediate banded states. Moreover, the model predicts that the pattern wavelength is a decreasing non-linear function of fog-water input and slope, and an increasing function of plant loss and fog-water flow speed. Finally, we show that the vegetation density is increased by the formation of the regular pattern compared to the density expected by the spatially homogeneous model emphasizing the importance of self-organization in arid ecosystems. (c) 2010 Elsevier Ltd. All rights reserved.

Experimental investigation of flow field around the elastic flag flapping in periodic state

NASA Astrophysics Data System (ADS)

Jia, Yongxia; Jia, Lichao; Su, Zhuang; Yuan, Huijing

2018-05-01

The flapping of a flag in the wind is a classical fluid-structure problem that concerns the interaction of elastic bodies with ambient fluid. We focus on the desirable experimental results of the flow around the flapping flag. By immersing the elastic yet self-supporting heavy flag into water flow, we use particle image velocimetry (PIV) techniques to obtain the whole flow field around the midspan of the flag interacting with a fluid in periodic state. A unique PIV image processing method is used to measure near-wall flow velocities around a moving elastic flag. There exists a thin flow circulation region on the suction side of the flag in periodic state. This observation suggests that viscous flow models may be needed to improve the theoretical predictions of the flapping flag in periodic state, especially in a large amplitude.

Dynamics of water bound to crystalline cellulose.

PubMed

O'Neill, Hugh; Pingali, Sai Venkatesh; Petridis, Loukas; He, Junhong; Mamontov, Eugene; Hong, Liang; Urban, Volker; Evans, Barbara; Langan, Paul; Smith, Jeremy C; Davison, Brian H

2017-09-19

Interactions of water with cellulose are of both fundamental and technological importance. Here, we characterize the properties of water associated with cellulose using deuterium labeling, neutron scattering and molecular dynamics simulation. Quasi-elastic neutron scattering provided quantitative details about the dynamical relaxation processes that occur and was supported by structural characterization using small-angle neutron scattering and X-ray diffraction. We can unambiguously detect two populations of water associated with cellulose. The first is "non-freezing bound" water that gradually becomes mobile with increasing temperature and can be related to surface water. The second population is consistent with confined water that abruptly becomes mobile at ~260 K, and can be attributed to water that accumulates in the narrow spaces between the microfibrils. Quantitative analysis of the QENS data showed that, at 250 K, the water diffusion coefficient was 0.85 ± 0.04 × 10 -10  m 2 sec -1 and increased to 1.77 ± 0.09 × 10 -10  m 2 sec -1 at 265 K. MD simulations are in excellent agreement with the experiments and support the interpretation that water associated with cellulose exists in two dynamical populations. Our results provide clarity to previous work investigating the states of bound water and provide a new approach for probing water interactions with lignocellulose materials.

Characterization of a water-solid interaction in a partially ordered system.

PubMed

Chakravarty, Paroma; Lubach, Joseph W

2013-11-04

GNE068-PC, a developmental compound, was previously characterized to be mesomorphous, i.e. having long-range order associated with significant local molecular disorder (Chakravarty et. al., Mol. Pharmaceutics, accepted). The compound was exposed to moisture under different relative humidity conditions ranging from 11% to 60% RH at room temperature (RT) for 7 days, and the resultant product phases were characterized. The partially ordered sample progressively lost crystallinity (long-range order) and birefringence (orientational order) upon exposure to increasing RH conditions, leading to the formation of a completely disordered amorphous phase at 60% RH (RT). Long-range positional order was irrecoverable even after moisture removal from the sample exposed to 60% RH. This was attributed to replacement of residual ethyl acetate by water, the former being critical for maintenance of long-range order in the material. In addition, water sorption appeared to irreversibly alter the molecular orientation, thereby affecting sample birefringence. Solid-state NMR revealed increases in (1)H and (13)C spin-lattice relaxation times (T1) going from the mesomorphous phase to the fully amorphous phase. This was indicative of reduction in lattice mobility, likely due to the decreased motion of the aromatic portions of the molecule, in particular C17, which showed the most dramatic increase in (13)C T1. This is likely due to decrease in available free volume upon water sorption. Drying of the hydrated disordered phase showed somewhat greater mobility than the hydrated phase, likely due to increased relative free volume through removal of water. A water-solid interaction therefore irreversibly changed the solid-state makeup of GNE068-PC.

ESIPT and photodissociation of 3-hydroxychromone in solution: photoinduced processes studied by static and time-resolved UV/Vis, fluorescence, and IR spectroscopy.

PubMed

Chevalier, Katharina; Grün, Anneken; Stamm, Anke; Schmitt, Yvonne; Gerhards, Markus; Diller, Rolf

2013-11-07

The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC.

Quick and Easy Measurements of the Inherent Optical Property of Water by Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izadi, Dina; Hajiesmaeilbaigi, Fereshteh

2009-04-19

To generate realistic images of natural waters, one must consider in some detail the interaction of light with the water body. The reflectance and attenuation coefficient of the second harmonic of Nd:YAG laser light through distilled water and a sample of water from the Oman Sea were measured in a solid-state laser laboratory to estimate inherent optical properties of natural waters. These measurements determined the bottom conditions and the impurities of the water. The water's reflectivity varied depending on the angle of incidence, height of the laser from water surface, wavelength of laser light, radiant intensities, and depth of water.more » In these experiments laser light propagated through the water nonlinearly, and different reflectance showed different bottom slopes. The differences among various water samples were obtained taking into account the exponential equation in attenuation coefficient versus depth graphs.« less

Rationalization of the solvation effects on the AtO+ ground-state change.

PubMed

Ayed, Tahra; Réal, Florent; Montavon, Gilles; Galland, Nicolas

2013-09-12

(211)At radionuclide is of considerable interest as a radiotherapeutic agent for targeted alpha therapy in nuclear medicine, but major obstacles remain because the basic chemistry of astatine (At) is not well understood. The AtO(+) cationic form might be currently used for (211)At-labeling protocols in aqueous solution and has proved to readily react with inorganic/organic ligands. But AtO(+) reactivity must be hindered at first glance by spin restriction quantum rules: the ground state of the free cation has a dominant triplet character. Investigating AtO(+) clustered with an increasing number of water molecules and using various flavors of relativistic quantum methods, we found that AtO(+) adopts in solution a Kramers restricted closed-shell configuration resembling a scalar-relativistic singlet. The ground-state change was traced back to strong interactions, namely, attractive electrostatic interactions and charge transfer, with water molecules of the first solvation shell that lift up the degeneracy of the frontier π* molecular orbitals (MOs). This peculiarity brings an alternative explanation to the highly variable reproducibility reported for some astatine reactions: depending on the production protocols (with distillation in gas-phase or "wet chemistry" extraction), (211)At may or may not readily react.

Towards A Predictive First Principles Understanding Of Molecular Adsorption On Graphene

DTIC Science & Technology

2016-10-05

used and developed state-of-the-art quantum mechanical methods to make accurate predictions about the interaction strength and adsorption structure...density functional theory, ab initio methods 16.  SECURITY CLASSIFICATION OF: 17.  LIMITATION OF ABSTRACT SAR 18.  NUMBER OF PAGES   11   19a.  NAME OF...important physical properties for a whole class of systems with weak non-covalent interactions, for example those involving the binding between water

Production waters associated with the Ferron coalbed methane fields, central Utah: Chemical and isotopic composition and volumes

USGS Publications Warehouse

Rice, C.A.

2003-01-01

This study investigated the composition of water co-produced with coalbed methane (CBM) from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in east-central Utah to better understand coalbed methane reservoirs. The Ferron coalbed methane play currently has more than 600 wells producing an average of 240 bbl/day/well water. Water samples collected from 28 wellheads in three fields (Buzzards Bench, Drunkards Wash, and Helper State) of the northeast-southwest trending play were analyzed for chemical and stable isotopic composition.Water produced from coalbed methane wells is a Na-Cl-HCO3 type. Water from the Drunkards Wash field has the lowest total dissolved solids (TDS) (6300 mg/l) increasing in value to the southeast and northeast. In the Helper State field, about 6 miles northeast, water has the highest total dissolved solids (43,000 mg/l), and major ion abundance indicates the possible influence of evaporite dissolution or mixing with a saline brine. In the southern Buzzards Bench field, water has variable total dissolved solids that are not correlated with depth or spatial distance. Significant differences in the relative compositions are present between the three fields implying varying origins of solutes and/or different water-rock interactions along multiple flow paths.Stable isotopic values of water from the Ferron range from +0.9??? to -11.4??? ?? 18O and -32??? to -90??? ?? 2H and plot below the global meteoric water line (GMWL) on a line near, but above values of present-day meteoric water. Isotopic values of Ferron water are consistent with modification of meteoric water along a flow path by mixing with an evolved seawater brine and/or interaction with carbonate minerals. Analysis of isotopic values versus chloride (conservative element) and total dissolved solids concentrations indicates that recharge water in the Buzzards Bench area is distinct from recharge water in Drunkards Wash and is about 3 ??C warmer. These variations in isotopes along with compositional variations imply that the Ferron reservoir is heterogeneous and compartmentalized, and that multiple flow paths may exist. ?? 2003 Published by Elsevier B.V. All rights reserved.

Reorganization of Hydration Water of DPPC Multilamellar Vesicles Induced by l-Cysteine Interaction.

PubMed

Arias, Juan M; Tuttolomondo, María E; Díaz, Sonia B; Ben Altabef, Aida

2018-05-24

The aim of this study is to analyze the consequences of water redistribution on the structure and stability of phospholipid bilayers induced by cysteine (Cys). This interaction is studied with 1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine (DPPC) multilamellar vesicles in gel (30 °C) and liquid crystalline (50 °C) state; experimental studies were performed by means of Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and differential scanning calorimetry (DSC). The polar head sites of the lipid molecules to which water can bind are identified by competition with compounds that form hydrogen bonds, such as Cys. FTIR spectroscopy results revealed that there is a Cys interaction with the phospholipid head groups in the gel and liquid crystalline phases. Raman spectra were measured in the gel state. They were dominated by vibrations of the fatty acyl chains, with superposition of a few bands from the head group, and clearly showed that the S-H stretching band of Cys shifted to lower frequencies with a decrease in its force constant. DSC disclosed an overview of the behavior of the multilamellar vesicles in the working temperature range (30-50 °C) and showed how the increase of the molar ratios modified the environment of the polar head and the hydrocarbon chains. A loss of the pretransition ( T P ) and an increase in the temperature of main transition ( T m ) with increasing Cys/DPPC molar ratio were observed.

NOHRSC Interactive Snow Information

Science.gov Websites

-present) RFC Basin Other (non-RFC) Basin State NSA region (Discussion) NSA subregion (Disc.) Basins by None Snow Water Equivalent Snow Depth Shallow SWE Shallow Snow Depth Snow Temperature Snow Density Snow Melt Snow Precipitation Non-Snow Precipitation Air Temperature Solar Radiation Relative Humidity

MANAGEMENT OF DIFFUSE POLLUTION IN AGRICULTURAL WATERSHEDS: LESSONS FROM THE MINNESOTA RIVER BASIN. (R825290)

EPA Science Inventory

Abstract

The Minnesota River (Minnesota, USA) receives large non-point source pollutant loads. Complex interactions between agricultural, state agency, environmental groups, and issues of scale make watershed management difficult. Subdividing the basin's 12 major water...

EMPIRICAL RELATIONSHIPS BETWEEN LAND USE/COVER AND ESTUARINE CONDITION IN THE NORTHEASTERN UNITED STATES

EPA Science Inventory

Land–water interactions were examined in three regions in the Virginian Biogeographic Province; the southern shore of Cape Cod, Massachusetts; the Hudson/Raritan region of New York; and the eastern shore of the Delmarva (Delaware/Maryland/Virginia) Peninsula. Cumulative distribut...

In vitro assessment of estrogen, androgen, and glucocorticoid bioactivity in a nationwide screen of United States stream waters

EPA Science Inventory

In vitro bioassays can identify environmental samples contaminated with bioactive chemicals that interact with steroid receptors and provide a cumulative, effect-based measurement of contamination. We measured in vitro estrogen (ER), androgen (AR), and glucocorticoid receptor (GR...

Modeling Molecular Interactions in Water: From Pairwise to Many-Body Potential Energy Functions

PubMed Central

2016-01-01

Almost 50 years have passed from the first computer simulations of water, and a large number of molecular models have been proposed since then to elucidate the unique behavior of water across different phases. In this article, we review the recent progress in the development of analytical potential energy functions that aim at correctly representing many-body effects. Starting from the many-body expansion of the interaction energy, specific focus is on different classes of potential energy functions built upon a hierarchy of approximations and on their ability to accurately reproduce reference data obtained from state-of-the-art electronic structure calculations and experimental measurements. We show that most recent potential energy functions, which include explicit short-range representations of two-body and three-body effects along with a physically correct description of many-body effects at all distances, predict the properties of water from the gas to the condensed phase with unprecedented accuracy, thus opening the door to the long-sought “universal model” capable of describing the behavior of water under different conditions and in different environments. PMID:27186804

Oxidation of MnO(100) and NaMnO2 formation: Characterization of Mn2+ and Mn3+ surfaces via XPS and water TPD

NASA Astrophysics Data System (ADS)

Feng, Xu; Cox, David F.

2018-09-01

The oxidation of clean and Na precovered MnO(100) has been investigated by X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD) of adsorbed water. XPS results indicate that Mn3O4-like and Mn2O3-like surfaces can be formed by various oxidation treatments of clean and nearly-stoichiometric MnO(100), while a NaMnO2-like surface can be produced by the oxidation of MnO(100) pre-covered with multilayers of metallic Na. Water TPD results indicate that water adsorption/desorption is sensitive to the available oxidation states of surface Mn cations, and can be used to distinguish between surfaces exposing Mn2+and Mn3+ cations, or a combination of these oxidation states. Carbon dioxide and water TPD results from the NaMnO2-like surface indicate that pre-adsorbed water blocks the uptake of CO2, while water displaces pre-adsorbed CO2. No indication of a strong reactive interaction is observed between CO2, water and the NaMnO2-like surface under the conditions of our study.

Electronic stopping power calculation for water under the Lindhard formalism for application in proton computed tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerrero, A. F., E-mail: afguerreror@uqvirtual.edu.co; Mesa, J., E-mail: jmesa@ibb.unesp.br

2016-07-07

Because of the behavior that charged particles have when they interact with biological material, proton therapy is shaping the future of radiation therapy in cancer treatment. The planning of radiation therapy is made up of several stages. The first one is the diagnostic image, in which you have an idea of the density, size and type of tumor being treated; to understand this it is important to know how the particles beam interacts with the tissue. In this work, by using de Lindhard formalism and the Y.R. Waghmare model for the charge distribution of the proton, the electronic stopping powermore » (SP) for a proton beam interacting with a liquid water target in the range of proton energies 10{sup 1} eV - 10{sup 10} eV taking into account all the charge states is calculated.« less

Use of natural user interfaces in water simulations

NASA Astrophysics Data System (ADS)

Donchyts, G.; Baart, F.; van Dam, A.; Jagers, B.

2013-12-01

Conventional graphical user interfaces, used to edit input and present results of earth science models, have seen little innovation for the past two decades. In most cases model data is presented and edited using 2D projections even when working with 3D data. The emergence of 3D motion sensing technologies, such as Microsoft Kinect and LEAP Motion, opens new possibilities for user interaction by adding more degrees of freedom compared to a classical way using mouse and keyboard. Here we investigate how interaction with hydrodynamic numerical models can be improved using these new technologies. Our research hypothesis (H1) states that properly designed 3D graphical user interface paired with the 3D motion sensor can significantly reduce the time required to setup and use numerical models. In this work we have used a LEAP motion controller combined with a shallow water flow model engine D-Flow Flexible Mesh. Interacting with numerical model using hands

Photoemission into water adsorbed on metals: Probing dissociative electron transfer using theory

NASA Astrophysics Data System (ADS)

Zhang, Yu; Whitten, J. L.

The photoinduced dissociation of water adsorbed on a silver nanoparticle is explored using theory to probe reaction pathways that produce hydrogen. Ab initio configuration theory is used to describe the systems. A formulation that allows excited electronic states embedded in a near continuum of lower energy states to be calculated accurately is described. Electron attachment of a photoemitted electron to adsorbed water can lead to the formation of H2 at a very low energy barrier with oxygen remaining on the Ag surface. A large energy barrier to form H2 plus adsorbed O is found for the ground state. The excited state has a much smaller barrier to OH stretch; however, to dissociate, the system must cross over from the excited state to the ground state potential energy surface. The cross over point is near the transition state for a ground state process. A characteristic feature of the excited state potential curve is an increase in energy in the early stages of OH stretch as the charge transfer state evolves from a state with considerable Rydberg character to one that has a typical OH antibonding molecular orbital. Another pathway releases a H atom leaving OH on the surface. Effects due to doping of a Ag nanoparticle with a K electron donor atom are compared with those caused by a Fermi level shift due to an applied potential. Results are also reported for electron transfer to a solvated lithium ion, Li(H2O) 6+, near the surface of a silver particle. A steering mechanism is found that involves the interaction of a hydridic hydrogen formed after electron transfer with an acidic hydrogen of a second solvated water molecule.

Spectral studies of N-nonyl acridine orange in anionic, cationic and neutral surfactants

NASA Astrophysics Data System (ADS)

Wiosetek-Reske, Agnieszka M.; Wysocki, Stanisław

2006-08-01

The spectroscopic and photophysical properties of N-nonyl acridine orange - a metachromatic dye useful as a mitochondrial probe in living cells - are reported in water and microheterogeneous media: anionic sodium dodecylsulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and neutral octylophenylpolyoxyethylene ether (TX-100). The spectral changes of N-nonyl acridine orange were observed in the presence of varying amount of SDS, CTAB and TX-100 and indicated formation of a dye-surfactant complex. The spectral changes were also regarded to be caused by the incorporation of dye molecules to micelles. It was proved by calculated values Kb and f in the following order: Kb TX-100 > Kb CTAB > Kb SDS and fTX-100 > fCTAB > fSDS. NAO binds to the micelle regardless the micellar charge. There are two types of interactions between NAO and micelles: hydrophobic and electrostatic. The hydrophobic interactions play a dominant role in binding of the dye to neutral TX-100. The unexpected fact of the binding NAO to cationic CTAB can be explained by a dominant role of hydrophobic interactions over electrostatic repulsion. Therefore, the affinity of NAO to CTAB is smaller than TX-100. Electrostatic interactions play an important role in binding of NAO to anionic micelles SDS. We observed a prolonged fluorescence lifetime after formation of the dye-surfactant complex τSDS > τTX-100 > τCTAB > τwater, the dye being protected against water in this environment. TX-100 is found to stabilize the excited state of NAO which is more polar than the ground state. Spectroscopic and photophysical properties of NAO will be helpful for a better understanding of the nature of binding and distribution inside mammalian cells.

Interaction of ice binding proteins with ice, water and ions.

PubMed

Oude Vrielink, Anneloes S; Aloi, Antonio; Olijve, Luuk L C; Voets, Ilja K

2016-03-19

Ice binding proteins (IBPs) are produced by various cold-adapted organisms to protect their body tissues against freeze damage. First discovered in Antarctic fish living in shallow waters, IBPs were later found in insects, microorganisms, and plants. Despite great structural diversity, all IBPs adhere to growing ice crystals, which is essential for their extensive repertoire of biological functions. Some IBPs maintain liquid inclusions within ice or inhibit recrystallization of ice, while other types suppress freezing by blocking further ice growth. In contrast, ice nucleating proteins stimulate ice nucleation just below 0 °C. Despite huge commercial interest and major scientific breakthroughs, the precise working mechanism of IBPs has not yet been unraveled. In this review, the authors outline the state-of-the-art in experimental and theoretical IBP research and discuss future scientific challenges. The interaction of IBPs with ice, water and ions is examined, focusing in particular on ice growth inhibition mechanisms.

Quantifying Groundwater Fluctuations in the Southern High Plains with GIS and Geostatistics

NASA Astrophysics Data System (ADS)

Whitehead, B.

2008-12-01

Groundwater as a dwindling non-renewable natural resource has been an important research theme in agricultural studies coupled with human-environment interaction. This research incorporated contemporary Geographic Information System (GIS) methodologies and a universal kriging interpolator (geostatistics) to develop depth to groundwater surfaces for the southern portion of the High Plains, or Ogallala, aquifer. The variations in the interpolated surfaces were used to calculate the volume of water mined from the aquifer from 1980 to 2005. The findings suggest a nearly inverse relationship to the water withdrawal scenarios derived by the United States Geological Survey (USGS) during the Regional Aquifer System Analysis (RASA) performed in the early 1980's. These results advocate further research into regional climate change, groundwater-surface water interaction, and recharge mechanisms in the region, and provide a substantial contribution to the continuing and contentious issue concerning the environmental sustainability of the High Plains.

Lid dynamics of porcine pancreatic lipase in non-aqueous solvents.

PubMed

Haque, Neshatul; Prabhu, N Prakash

2016-10-01

Understanding the dynamics of enzymes in organic solvents has wider implications on their industrial applications. Pancreatic lipases, which show activity in their lid open-state, demonstrate enhanced activity in organic solvents at higher temperatures. However, the lid dynamics of pancreatic lipases in non-aqueous environment is yet to be clearly understood. Dynamics of porcine pancreatic lipase (PPL) in open and closed conformations was followed in ethanol, toluene, and octanol using molecular simulation methods. In silico double mutant D250V and E254L of PPL (PPLmut-Cl) was created and its lid opening dynamics in water and in octanol was analyzed. PPL showed increase in solvent accessible surface area and decrease in packing density as the polarity of the surrounded solvent decreased. Breaking the interactions between D250-Y115, and D250-E254 in PPLmut-Cl directed the lid to attain open-state conformation. Major energy barriers during the lid movement in water and in octanol were identified. Also, the trajectories of lid movement were found to be different in these solvents. Only the double mutant at higher temperature showed lid opening movement suggesting the essential role of the three residues in holding the lid in closed conformation. The lid opening dynamics was faster in octanol than water suggesting that non-polar solvents favor open conformation of the lid. This study identifies important interactions between the lid and the residues in domain 1 which possibly keeps the lid in closed conformation. Also, it explains the rearrangements of residue-residue interactions during lid opening movement in water and in octanol. Copyright © 2016 Elsevier B.V. All rights reserved.

EnviroAtlas - Domestic Water Demand by 12-Digit HUC for the Conterminous United States

EPA Pesticide Factsheets

This EnviroAtlas dataset includes domestic water demand attributes which provide insight into the amount of water currently used for indoor and outdoor residential purposes in the contiguous United States. The values are based on 2010 water demand and 2010 population distribution, and have been summarized by subwatershed, or 12-digit hydrologic unit code (HUC12). For the purposes of this metric, domestic water use includes residential uses, such as for drinking, bathing, cleaning, landscaping, and pools. Depending on the location, domestic water can be self-supplied, such as by private wells, or publicly-supplied, such as by municipalities. Sources include surface water and groundwater. Estimates are for primary residences only (i.e., excluding second homes and tourism rentals). This dataset was produced by the US EPA to support research and online mapping activities related to the EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Number of Water Markets per HUC8 Watershed, U.S., 2015, Forest Trends' Ecosystem Marketplace

EPA Pesticide Factsheets

This EnviroAtlas dataset contains polygons depicting the number of watershed-level market-based programs, referred to herein as markets, in operation per 8-digit HUC watershed throughout the United States. The data were collected via surveys and desk research conducted by Forest Trends' Ecosystem Marketplace during 2014 regarding markets operating to protect watershed ecosystem services. Utilizing these data, the number of water market coverage areas overlaying each HUC8 watershed were calculated to produce this dataset. Only water markets identified as operating at the watershed level (i.e., single or multiple watersheds define the market boundaries) were included in the count of water markets per HUC8 watershed. Excluded were water markets operating at the national, state, county, or federal lands level and all water projects. Attribute data include the watershed's 8-digit hydrologic unit code and name, in addition to the watershed-level water market count associated with the watershed. This dataset was produced by Forest Trends' Ecosystem Marketplace to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Addi

Stability of micro-Cassie states on rough substrates

NASA Astrophysics Data System (ADS)

Guo, Zhenjiang; Liu, Yawei; Lohse, Detlef; Zhang, Xuehua; Zhang, Xianren

2015-06-01

We numerically study different forms of nanoscale gaseous domains on a model for rough surfaces. Our calculations based on the constrained lattice density functional theory show that the inter-connectivity of pores surrounded by neighboring nanoposts, which model the surface roughness, leads to the formation of stable microscopic Cassie states. We investigate the dependence of the stability of the micro-Cassie states on substrate roughness, fluid-solid interaction, and chemical potential and then address the differences between the origin of the micro-Cassie states and that of surface nanobubbles within similar models. Finally, we show that the micro-Cassie states share some features with experimentally observed micropancakes at solid-water interfaces.

Urea-mediated protein denaturation: a consensus view.

PubMed

Das, Atanu; Mukhopadhyay, Chaitali

2009-09-24

We have performed all-atom molecular dynamics simulations of three structurally similar small globular proteins in 8 M urea and compared the results with pure aqueous simulations. Protein denaturation is preceded by an initial loss of water from the first solvation shell and consequent in-flow of urea toward the protein. Urea reaches the first solvation shell of the protein mainly due to electrostatic interaction with a considerable contribution coming from the dispersion interaction. Urea shifts the equilibrium from the native to denatured ensemble by making the protein-protein contact less stable than protein-urea contact, which is just the reverse of the condition in pure water, where protein-protein contact is more stable than protein-water contact. We have also seen that water follows urea and reaches the protein interior at later stages of denaturation, while urea preferentially and efficiently solvates different parts of the protein. Solvation of the protein backbone via hydrogen bonding, favorable electrostatic interaction with hydrophilic residues, and dispersion interaction with hydrophobic residues are the key steps through which urea intrudes the core of the protein and denatures it. Why urea is preferred over water for binding to the protein backbone and how urea orients itself toward the protein backbone have been identified comprehensively. All the key components of intermolecular forces are found to play a significant part in urea-induced protein denaturation and also toward the stability of the denatured state ensemble. Changes in water network/structure and dynamical properties and higher degree of solvation of the hydrophobic residues validate the presence of "indirect mechanism" along with the "direct mechanism" and reinforce the effect of urea on protein.

Dynamics and Kinetics Study of "In-Water" Chemical Reactions by Enhanced Sampling of Reactive Trajectories.

PubMed

Zhang, Jun; Yang, Y Isaac; Yang, Lijiang; Gao, Yi Qin

2015-11-12

High potential energy barriers and engagement of solvent coordinates set challenges for in silico studies of chemical reactions, and one is quite commonly limited to study reactions along predefined reaction coordinate(s). A systematic protocol, QM/MM MD simulations using enhanced sampling of reactive trajectories (ESoRT), is established to quantitatively study chemical transitions in complex systems. A number of trajectories for Claisen rearrangement in water and toluene were collected and analyzed, respectively. Evidence was found that the bond making and breaking during this reaction are concerted processes in solutions, preferentially through a chairlike configuration. Water plays an important dynamic role that helps stabilize the transition sate, and the dipole-dipole interaction between water and the solute also lowers the transition barrier. The calculated rate coefficient is consistent with the experimental measurement. Compared with water, the reaction pathway in toluene is "narrower" and the reaction rate is slower by almost three orders of magnitude due to the absence of proper interactions to stabilize the transition state. This study suggests that the "in-water" nature of the Claisen rearrangement in aqueous solution influences its thermodynamics, kinetics, as well as dynamics.

Specific intermolecular interactions of conserved water molecules with amino acids in the Galectin-1 carbohydrate recognition domain

NASA Astrophysics Data System (ADS)

Di Lella, Santiago; Petruk, Ariel A.; Armiño, Diego J. Alonso de; Álvarez, Rosa M. S.

2010-08-01

Water molecules, rigidly associated to protein surfaces, play a key role in stabilizing biomolecules and participating in their biological functions. Recent studies on the solvation properties of the carbohydrate recognition domain of Galectin-1 by means of molecular dynamic simulations have revealed the existence of several water sites which were well correlated to both the bound water molecules observed in the crystal structure of the protein in the free state and to some of the hydroxyl groups of the carbohydrate ligand observed in the crystal structure of the complexed protein. In this work, we present a study using quantum mechanical methods (B3LYP/6-311++G(3df,3dp)//B3LYP/6-31+G(d)) to determine the energy involved in the binding of these water molecules to specific amino acids in the carbohydrate recognition domain of the protein. By modeling the hydroxyl groups of the carbohydrate by methanol, the energies associated to the local interactions between the ligand and the protein have been evaluated by replacing specific water molecules with methanol. The values of the binding energies have been compared to those previously obtained by the molecular dynamic method.

Flow of water and sediments through Southwestern riparian systems

Treesearch

Leonard F. DeBano; Peter F. Ffolliott; Kenneth N. Brooks

1996-01-01

The paper describes streamflow, sediment movement and vegetation interactions within riparian systems of the southwestern United States. Riparian systems are found in a wide range of vegetation types, ranging from lower elevation desert environments to high elevation conifer forests. The climatic, vegetative and hydrologic processes operating in the southwestern...

Problem Solving Interactions on Electronic Networks.

ERIC Educational Resources Information Center

Waugh, Michael; And Others

Arguing that electronic networking provides a medium which is qualitatively superior to the traditional classroom for conducting certain types of problem solving exercises, this paper details the Water Problem Solving Project, which was conducted on the InterCultural Learning Network in 1985 and 1986 with students from the United States, Mexico,…

Ordered and disordered dynamics in monolayers of rolling particles.

PubMed

Kim, Byungsoo; Putkaradze, Vakhtang

2010-12-10

We consider the ordered and disordered dynamics for monolayers of rolling self-interacting particles modeling water molecules. The rolling constraint represents a simplified model of a strong, but rapidly decaying bond with the surface. We show the existence and nonlinear stability of ordered lattice states, as well as disturbance propagation through and chaotic vibrations of these states. We study the dynamics of disordered gas states and show that there is a surprising and universal linear connection between distributions of angular and linear velocity, allowing definition of temperature.

Triangulating the Sociohydrology of Water Supply, Quality and Forests in the Triangle

NASA Astrophysics Data System (ADS)

Band, L. E.

2016-12-01

The North Carolina Research Triangle is among the most rapidly growing metropolitan areas in the United States, with decentralized governance split among several different municipalities, counties and water utilities. Historically smaller populations, plentiful rainfall, and riparian rights based water law provided both a sense of security for water resources and influenced the development of separate infrastructure systems across the region. The growth of water demand with rising populations with typical suburban sprawl, the development of multi-use reservoirs immediately downstream of urban areas, and increased hydroclimate variability have raised the potential for periodic water scarcity coupled with increasing eutrophication of water supplies. We discuss the interactions and tradeoffs between management of emerging water scarcity, quality and forest biodiversity in the Triangle as a model for the US Southeast. Institutional stakeholders include water supply and stormwater utilities, environmental NGOs, federal, state, county and municipal governments, developers and home owner associations. We emphasize principles of ecohydrologic resilience learned in heavily instrumented research watersheds, adapted to rapidly developing urban systems, and including socioeconomic and policy dynamics. Significant 20th century reforestation of central North Carolina landscapes have altered regional water balances, while providing both flood and water quality mitigation. The regrowth forest is dynamic and heterogeneous in water use based on age class and species distribution, with substantial plantation and natural regeneration. Forecasts of land use and forest structural and compositional change are based on scenario socioeconomic development, climate change and forecast wood product markets. Urban forest and green infrastructure has the potential to mediate the trade-offs and synergies of these goals, but is in a very nascent state. Computational tools to assess policy alternatives impacts on water quality, quantity and forest biodiversity are developed to serve information to multiple stakeholders, and communicate and visualize outcomes.

Quantifying structural states of soft mudrocks

NASA Astrophysics Data System (ADS)

Li, B.; Wong, R. C. K.

2016-05-01

In this paper, a cm model is proposed to quantify structural states of soft mudrocks, which are dependent on clay fractions and porosities. Physical properties of natural and reconstituted soft mudrock samples are used to derive two parameters in the cm model. With the cm model, a simplified homogenization approach is proposed to estimate geomechanical properties and fabric orientation distributions of soft mudrocks based on the mixture theory. Soft mudrocks are treated as a mixture of nonclay minerals and clay-water composites. Nonclay minerals have a high stiffness and serve as a structural framework of mudrocks when they have a high volume fraction. Clay-water composites occupy the void space among nonclay minerals and serve as an in-fill matrix. With the increase of volume fraction of clay-water composites, there is a transition in the structural state from the state of framework supported to the state of matrix supported. The decreases in shear strength and pore size as well as increases in compressibility and anisotropy in fabric are quantitatively related to such transition. The new homogenization approach based on the proposed cm model yields better performance evaluation than common effective medium modeling approaches because the interactions among nonclay minerals and clay-water composites are considered. With wireline logging data, the cm model is applied to quantify the structural states of Colorado shale formations at different depths in the Cold Lake area, Alberta, Canada. Key geomechancial parameters are estimated based on the proposed homogenization approach and the critical intervals with low strength shale formations are identified.

Evaluating the Effectiveness of Science for Decision-Making: Water Managers and Tree- Ring Data in the Western United States

NASA Astrophysics Data System (ADS)

Rice, J. L.; Woodhouse, C.; Lukas, J.

2008-12-01

Current climate variability, potential impacts of climate change, and limited resources in the face of growing demand are increasingly prompting water managers in the western United States to consider and use data from climate-related research in water resource planning. Much of these data are produced by stakeholder- driven science programs, such as NOAA's Regional Integrated Science Assessments (RISAs), but there have been few efforts to evaluate the effectiveness of these science-to-application efforts. Over the past several years, researchers with the Western Water Assessment (WWA) RISA have been providing tree-ring reconstructions of streamflow to water managers in Colorado and other western states, and presenting technical workshops explaining the applications of these tree-ring data for water management and planning. Using in-depth interviews and a survey questionnaire, we have assessed the effectiveness and outcomes of these engagements, addressing (1) the factors that have prompted water managers to seek out tree-ring data, (2) how paleoclimate data has been made relevant and accessible for water resource planning, and (3) how tree-ring data and information have been utilized by water managers and other workshop participants. We also provide an assessment of challenges and opportunities that exist in the translation of climate science for decision-making, including how tree-ring data are interpreted in the context of water planning paradigms, issues of credibility and acceptance of tree ring data, and what data needs exist in different planning environments. These findings have broader application in improving and evaluating science-policy interactions related to climate and climate change.

A quantitative analysis of hydraulic interaction processes in stream-aquifer systems

PubMed Central

Wang, Wenke; Dai, Zhenxue; Zhao, Yaqian; Li, Junting; Duan, Lei; Wang, Zhoufeng; Zhu, Lin

2016-01-01

The hydraulic relationship between the stream and aquifer can be altered from hydraulic connection to disconnection when the pumping rate exceeds the maximum seepage flux of the streambed. This study proposes to quantitatively analyze the physical processes of stream-aquifer systems from connection to disconnection. A free water table equation is adopted to clarify under what conditions a stream starts to separate hydraulically from an aquifer. Both the theoretical analysis and laboratory tests have demonstrated that the hydraulic connectedness of the stream-aquifer system can reach a critical disconnection state when the horizontal hydraulic gradient at the free water surface is equal to zero and the vertical is equal to 1. A boundary-value problem for movement of the critical point of disconnection is established for an analytical solution of the inverted water table movement beneath the stream. The result indicates that the maximum distance or thickness of the inverted water table is equal to the water depth in the stream, and at a steady state of disconnection, the maximum hydraulic gradient at the streambed center is 2. This study helps us to understand the hydraulic phenomena of water flow near streams and accurately assess surface water and groundwater resources. PMID:26818442

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

PubMed Central

2011-01-01

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating. PMID:27502633

Bibliography of U.S. Geological Survey studies of lakes and reservoirs; the first 100 years

USGS Publications Warehouse

Winter, Thomas C.

1982-01-01

For more than 100 years, the U.S. Geological Survey has pursued its mission of assessing and mapping the earth resources of the United States, including assessment of the Nation's water resources. Although the Survey has never been a water-management or development agency, it has assisted agencies that are responsible for such developments, and commonly provides data and information for such purposes. Because reservoirs are an intergral part of most water-development projects, the Survey has been involved in reservoir-related studies since the 1880's. The largest and longest involvement has centered on providing information on streamflows and sediment transport related to existing and proposed reservoirs. During the late 1940's, the Survey greatly expanded its activities in evaporation research. More recently, ground water, including bank storage, has gained increased attention. Most of these studies were related primarily to questions of water quantity, and the Survey continues to be involved in studies of physical hydrology. In addition, in response to the increased concern with environmental quality during the past 20 years, the number of Survey studies of the chemical and biological aspects of lakes and reservoirs have increased considerably. Prompted by the recent Centennial (1879-1979) of the U.S. Geological Survey, it is appropriate to assess the Survey's contributions to the hydrology of lakes and reservoirs. Both natural lakes and manmade reservoirs are included in this report. 1 This report includes studies in which lakes or reservoirs are the principal topics. It does not include reports of general water resources of an area in which lakes are discussed as part of that area. This report also does not include data reports in which the data are merely tabulated. The types of reports listed herein include studies of existing or proposed water bodies and associated fluxes of water to and from these water bodies. This report does not include geological or paleobiological studies of ancient lakes. This report does, however, include geological studies of proposed reservoir sites. This bibliography has three parts. The first part is an alphabetical listing that gives complete references to the given reports. Part 2 is a listing by topics, and only the authors, date of publication, and cross-reference to the State are given. Six general categories are considered: Lake hydrology; interaction of lakes and streamflow, including geological studies of reservoir sites; interaction of lakes and atmospheric water; interaction of lakes. and ground water; chemical and biological limnology; and sediment studies. The first four consist of studies of physical characteristics of lakes, and the last two of water-quality characteristics. The category of lake hydrology includes general studies of lakes that are not easily grouped into one of the more specific categories of physical characteristics. For example, it includes water-budget studies where all aspects of hydrology are discussed. It also includes studies of hydrodynamics of lakes as well as studies of lake-level fluctuations. The category of interaction of lakes and streamflow includes preimpoundment studies of streamflow discharge for reservoir design, and studies of the effects of existing reservoirs on streamflow and channel characteristics. Also included in this category are geological studies of river valleys for proposed reservoir sites. The category of interaction of lakes and atmospheric water includes primarily studies of evaporation. The interaction of lakes and ground water includes studies of bank storage. The category of chemical and biological studies was not subdivided into more specific types because of the virtually inseparable relation between chemistry and biology in most studies. This bibliography provided much of the information for two papers that discuss the history of U.S. Geological Survey studies of lakes and reservoirs. (See Winter, 1981b; and Hadley, 1981).

Spatially-explicit modeling of multi-scale drivers of aboveground forest biomass and water yield in watersheds of the Southeastern United States.

PubMed

Ajaz Ahmed, Mukhtar Ahmed; Abd-Elrahman, Amr; Escobedo, Francisco J; Cropper, Wendell P; Martin, Timothy A; Timilsina, Nilesh

2017-09-01

Understanding ecosystem processes and the influence of regional scale drivers can provide useful information for managing forest ecosystems. Examining more local scale drivers of forest biomass and water yield can also provide insights for identifying and better understanding the effects of climate change and management on forests. We used diverse multi-scale datasets, functional models and Geographically Weighted Regression (GWR) to model ecosystem processes at the watershed scale and to interpret the influence of ecological drivers across the Southeastern United States (SE US). Aboveground forest biomass (AGB) was determined from available geospatial datasets and water yield was estimated using the Water Supply and Stress Index (WaSSI) model at the watershed level. Our geostatistical model examined the spatial variation in these relationships between ecosystem processes, climate, biophysical, and forest management variables at the watershed level across the SE US. Ecological and management drivers at the watershed level were analyzed locally to identify whether drivers contribute positively or negatively to aboveground forest biomass and water yield ecosystem processes and thus identifying potential synergies and tradeoffs across the SE US region. Although AGB and water yield drivers varied geographically across the study area, they were generally significantly influenced by climate (rainfall and temperature), land-cover factor1 (Water and barren), land-cover factor2 (wetland and forest), organic matter content high, rock depth, available water content, stand age, elevation, and LAI drivers. These drivers were positively or negatively associated with biomass or water yield which significantly contributes to ecosystem interactions or tradeoff/synergies. Our study introduced a spatially-explicit modelling framework to analyze the effect of ecosystem drivers on forest ecosystem structure, function and provision of services. This integrated model approach facilitates multi-scale analyses of drivers and interactions at the local to regional scale. Copyright © 2017 Elsevier Ltd. All rights reserved.

Importance of hydrologic data for interpreting wetland maps and assessing wetland loss and mitigation

USGS Publications Warehouse

Carter, V.

1991-01-01

The US Geological Survey collects and disseminates, in written and digital formats, groundwater and surface-water information related to the tidal and nontidal wetlands of the United States. This information includes quantity, quality, and availability of groundwater and surface water; groundwater and surface-water interactions (recharge-discharge); groundwater flow; and the basic surface-water characteristics of streams, rivers, lakes, and wetlands. Water resources information in digital format can be used in geographic information systems (GISs) for many purposes related to wetlands. US Geological Survey wetland-related activities include collection of information important for assessing and mitigating coastal wetland loss and modification, hydrologic data collection and interpretation, GIS activities, identification of national trends in water quality and quantity, and process-oriented wetland research. -Author

Anomalous Dynamics of Water Confined in Protein-Protein and Protein-DNA Interfaces.

PubMed

Chong, Song-Ho; Ham, Sihyun

2016-10-06

Confined water often exhibits anomalous properties not observable in the bulk phase. Although water in hydrophobic confinement has been the focus of intense investigation, the behavior of water confined between hydrophilic surfaces, which are more frequently found in biological systems, has not been fully explored. Here, we investigate using molecular dynamics simulations dynamical properties of the water confined in hydrophilic protein-protein and protein-DNA interfaces. We find that the interfacial water exhibits glassy slow relaxations even at 300 K. In particular, the rotational dynamics show a logarithmic decay that was observed in glass-forming liquids at deeply supercooled states. We argue that such slow water dynamics are indeed induced by the hydrophilic binding surfaces, which is in opposition to the picture that the hydration water slaves protein motions. Our results will significantly impact the view on the role of water in biomolecular interactions.

Rate laws for water-assisted compaction and stress-induced water-rock interaction in sandstones

NASA Astrophysics Data System (ADS)

Dewers, Thomas; Hajash, Andrew

1995-07-01

Mineral-water interactions under conditions of nonhydrostatic stress play a role in subjects as diverse as ductile creep in fault zones, phase relations in metamorphic rocks, mass redistribution and replacement reactions during diagenesis, and loss of porosity in deep sedimentary basins. As a step toward understanding the fundamental geochemical processes involved, using naturally rounded St. Peter sand, we have investigated the kinetics of pore volume loss and quartz-water reactions under nonhydrostatic, hydrothermal conditions in flow-through reactors. Rate laws for creep and mineral-water reaction are derived from the time rate of change of pore volume, sand-water dissolution kinetics, and (flow rate independent) steady state silica concentrations, and reveal functional dependencies of rates on grain size, volume strain, temperature, effective pressure (confining minus pore pressure), and specific surface areas. Together the mechanical and chemical rate laws form a self-consistent model for coupled deformation and water-rock interaction of porous sands under nonhydrostatic conditions. Microstructural evidence shows a progressive widening of nominally circular and nominally flat grain-grain contacts with increasing strain or, equivalently, porosity loss, and small quartz overgrowths occurring at grain contact peripheries. The mechanical and chemical data suggest that the dominant creep mechanism is due to removal of mass from grain contacts (termed pressure solution or solution transfer), with a lesser component of time-dependent crack growth and healing. The magnitude of a stress-dependent concentration increase is too large to be accounted for by elastic or dislocation strain energy-induced supersaturations, favoring instead the normal stress dependence of molar Gibbs free energy associated with grain-grain interfaces.

Impact of fluid-rock chemical interactions on tracer transport in fractured rocks.

PubMed

Mukhopadhyay, Sumit; Liu, H-H; Spycher, N; Kennedy, B M

2013-11-01

In this paper, we investigate the impact of chemical interactions, in the form of mineral precipitation and dissolution reactions, on tracer transport in fractured rocks. When a tracer is introduced in fractured rocks, it moves through the fracture primarily by advection and it also enters the stagnant water of the surrounding rock matrix through diffusion. Inside the porous rock matrix, the tracer chemically interacts with the solid materials of the rock, where it can precipitate depending on the local equilibrium conditions. Alternatively, it can be dissolved from the solid phase of the rock matrix into the matrix pore water, diffuse into the flowing fluids of the fracture and is advected out of it. We show that such chemical interactions between the fluid and solid phases have significant impact on tracer transport in fractured rocks. We invoke the dual-porosity conceptualization to represent the fractured rocks and develop a semi-analytical solution to describe the transient transport of tracers in interacting fluid-rock systems. To test the accuracy and stability of the semi-analytical solution, we compare it with simulation results obtained with the TOUGHREACT simulator. We observe that, in a chemically interacting system, the tracer breakthrough curve exhibits a pseudo-steady state, where the tracer concentration remains more or less constant over a finite period of time. Such a pseudo-steady condition is not observed in a non-reactive fluid-rock system. We show that the duration of the pseudo-state depends on the physical and chemical parameters of the system, and can be exploited to extract information about the fractured rock system, such as the fracture spacing and fracture-matrix interface area. © 2013.

Investigation of the Hydantoin Monomer and its Interaction with Water Molecules

NASA Astrophysics Data System (ADS)

Gruet, Sébastien; Perez, Cristobal; Schnell, Melanie

2017-06-01

Hydantoin (Imidazolidine-2,4-dione, C_3H_4N_2O_2) is a five-membered heterocyclic compound of astrobiological interest. This molecule has been detected in carbonaceous chondrites [1], and its formation can rise from the presence of glycolic acid and urea, two prebiotic molecules [2]. The hydrolysis of hydantoin under acidic conditions can also produce glycine [3], an amino acid actively searched for in the interstellar medium. Spectroscopic data of hydantoin is very limited and mostly dedicated to the solid phase. The high resolution study in gas phase is restricted to the work recently published by Ozeki et al. reporting the pure rotational spectra of the ground state and two vibrational states of the molecule in the millimeter-wave region (90-370 GHz)[4]. Using chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy, we recorded the jet-cooled rotational spectra of hydantoin with water between 2 to 8 GHz. We observed the ground state of hydantoin monomer and several water complexes with one or two water molecules. All the observed species exhibit a hyperfine structure due to the two nitrogen atoms present in the molecule, which were fully resolved and analyzed. Additional experiments with a ^{18}O enriched water sample were realized to determine the oxygen-atom positions of the water monomers. These experiments yielded accurate structural information on the preferred water binding sites. The observed complexes and the interactions that hold them together, mainly strong directional hydrogen bonds, will be presented and discussed. [1] Shimoyama, A. and Ogasawara, R., Orig. Life Evol. Biosph., 32, 165-179, 2002. DOI:10.1023/A:1016015319112. [2] Menor-Salván, C. and Marín-Yaseli, M.R., Chem. Soc. Rev., 41(16), 5404-5415, 2012. DOI:10.1039/c2cs35060b. [3] De Marcellus P., Bertrand M., Nuevo M., Westall F. and Le Sergeant d'Hendecourt L., Astrobiology. 11(9), 847-854, 2011. DOI:10.1089/ast.2011.0677. [4] Ozeki, H., Miyahara R., Ihara H., Todaka S., Kobayashi K., and Ohishi M., Astron. Astrophys., Forthcoming article (

Inhibition effect of sugar-based amphiphiles on eutectic formation in the freezing-thawing process of aqueous NaCl solution.

PubMed

Ogawa, Shigesaburo; Osanai, Shuichi

2007-04-01

DSC and simultaneous XRD-DSC measurements were carried out to clarify the interaction among the ingredients in a ternary aqueous solution composed of NaCl, a sugar-based amphiphile or free sugar, and water. Two aspects of the inhibition of eutectic formation were suggested through the addition of the sugar amphiphile. One was the retention of the glass state of the eutectic phase, and the other was the trapping of NaCl hydrate into the sugar moiety of the amphiphilic aggregate. The difference between the free sugar and the amphiphilic one in terms of the trapping of NaCl hydrate was attributable to their dissimilarity in the dissolution state. The results indicated that the free sugars in water could interact with NaCl hydrate on the basis of their various hydroxyl groups. On the other hand, the sugar-based amphiphiles generated a self-assembly aggregate in the system, and interacted with NaCl hydrate by a salting-in effect with their sugar moiety in the freezing-thawing process. It was confirmed that the number of sugar units played an important role in trapping NaCl hydrate in the system. The effects of the structural isomerism in the sugars were slight with regard to the inhibition of eutectic formation.

An integrated assessment of energy-water nexus at the state level in the United States: Projections and analyses under different scenarios through 2095

NASA Astrophysics Data System (ADS)

Liu, L.; Patel, P. L.; Hejazi, M. I.; Kyle, P.; Davies, E. G.; Zhou, Y.; Clarke, L.; Edmonds, J.

2013-12-01

Water withdrawals for thermoelectric power plants account for approximately half of the total water use in the United States. With growing electricity demands in the future and limited water supplies in many water-scarce states in the U.S., grasping the trade-off between energy and water requires an integrated modeling approach that can capture the interactions among energy, water availability, climate, technology, and economic factors at various scales. In this study, the Global Change Assessment Model (GCAM), a technologically-detailed integrated model of the economy, energy, agriculture and land use, water, and climate systems, with 14 geopolitical regions that are further dissaggregated into up to 18 agro-ecological zones, was extended to model the electricity and water systems at the state level in the U.S. More specifically, GCAM was employed to estimate future state-level electricity generation and demands, and the associated water withdrawals and consumptions under a set of six scenarios with extensive levels of details on generation fuel portfolio, cooling technology mix, and water use intensities. The state-level estimates were compared against available inventories where good agreement was achieved on national and regional levels. We then explored the electric-sector water use up to 2095, focusing on implications from: 1) socioeconomics and growing demands, 2) the adoption of climate mitigation policy (e.g., RCP4.5 W/m2 vs. a reference scenario), 3) the transition of cooling systems, 4) constraints on electricity trading across states (full trading vs. limited trading), and 5) the adoption of water saving technologies. Overall, the fast retirement of once-through cooling, together with the gradual transition from fossil fuels dominant to a mixture of different fuels, accelerate the decline of water withdrawals and correspondingly compensate consumptive water use. Results reveal that U.S. electricity generation expands significantly as population grows, while U.S. electric-sector water withdrawals are projected to decline by 8.6% - 89% by 2095 and water consumptions are projected to increase by 14% - 101%. Some regional patterns could be observed when analyzing the state-level results spatially. Under the climate mitigation policy (RCP4.5) scenario, nuclear power plants contribute heavily to total electric-sector water withdrawal and consumption in Eastern U.S., while under the reference scenario, coal power plants are the primary water users in Eastern U.S. In the reference scenario, Eastern U.S. is projected to experience substantial drops in water withdrawals, while the Western U.S. will likely endure a moderate increase over the century. The highly-resolved nature of this study both geographically and technologically provides a useful platform to address scientific and policy relevant and emerging issues at the heart of the water-energy nexus in the U.S. Although this study is focused on the U.S., it is performed in the context of the global framework of GCAM where local changes can propagate to influence decisions in other regions outside of the U.S. and vice versa.

Optimized coordinates in vibrational coupled cluster calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomsen, Bo; Christiansen, Ove; Yagi, Kiyoshi

The use of variationally optimized coordinates, which minimize the vibrational self-consistent field (VSCF) ground state energy with respect to orthogonal transformations of the coordinates, has recently been shown to improve the convergence of vibrational configuration interaction (VCI) towards the exact full VCI [K. Yagi, M. Keçeli, and S. Hirata, J. Chem. Phys. 137, 204118 (2012)]. The present paper proposes an incorporation of optimized coordinates into the vibrational coupled cluster (VCC), which has in the past been shown to outperform VCI in approximate calculations where similar restricted state spaces are employed in VCI and VCC. An embarrassingly parallel algorithm for variationalmore » optimization of coordinates for VSCF is implemented and the resulting coordinates and potentials are introduced into a VCC program. The performance of VCC in optimized coordinates (denoted oc-VCC) is examined through pilot applications to water, formaldehyde, and a series of water clusters (dimer, trimer, and hexamer) by comparing the calculated vibrational energy levels with those of the conventional VCC in normal coordinates and VCI in optimized coordinates. For water clusters, in particular, oc-VCC is found to gain orders of magnitude improvement in the accuracy, exemplifying that the combination of optimized coordinates localized to each monomer with the size-extensive VCC wave function provides a supreme description of systems consisting of weakly interacting sub-systems.« less

Controlled cohort evaluation of the LiveLighter mass media campaign’s impact on adults’ reported consumption of sugar-sweetened beverages

PubMed Central

Morley, Belinda C; Niven, Philippa H; Dixon, Helen G; Swanson, Maurice G; McAleese, Alison B; Wakefield, Melanie A

2018-01-01

Objective To evaluate the LiveLighter ‘Sugary Drinks’ campaign impact on awareness, knowledge and sugar-sweetened beverage (SSB) consumption. Design Cohort study with population surveys undertaken in intervention and comparison states at baseline (n=900 each), with 78% retention at follow-up (intervention: n=673; comparison: n=730). Analyses tested interactions by state (intervention, comparison) and time (baseline, follow-up). Setting and participants Adults aged 25–49 years residing in the Australian states of Victoria and South Australia. Intervention The 6-week mass media campaign ran in Victoria in October/November 2015. It focused on the contribution of SSBs to the development of visceral ‘toxic fat’, graphically depicted around vital organs, and ultimately serious disease. Paid television advertising was complemented by radio, cinema, online and social media advertising, and stakeholder and community engagement. Primary outcome measure Self-reported consumption of SSBs, artificially sweetened drinks and water. Secondary outcome measures Campaign recall and recognition; knowledge of the health effects of overweight and SSB consumption; perceived impact of SSB consumption on body weight and of reduced consumption on health. Results A significant reduction in frequent SSB consumption was observed in the intervention state (intervention: 31% compared with 22%, comparison: 30% compared with 29%; interaction p<0.01). This was accompanied by evidence of increased water consumption (intervention: 66% compared with 73%; comparison: 68% compared with 67%; interaction p=0.09) among overweight/obese SSB consumers. This group also showed increased knowledge of the health effects of SSB consumption (intervention: 60% compared with 71%, comparison: 63% compared with 59%; interaction p<0.05) and some evidence of increased prevalence of self-referent thoughts about SSB’s relationship to weight gain (intervention: 39% compared with 45%, comparison: 43% compared with 38%; interaction p=0.06). Conclusions The findings provide evidence of reduced SSB consumption among adults in the target age range following the LiveLighter campaign. This is notable in a context where public health campaigns occur against a backdrop of heavy commercial product advertising promoting increased SSB consumption. PMID:29695387

Dynamics of the active site loops in catalyzing aminoacylation reaction in seryl and histidyl tRNA synthetases.

PubMed

Dutta, Saheb; Kundu, Soumya; Saha, Amrita; Nandi, Nilashis

2018-03-01

Aminoacylation reaction is the first step of protein biosynthesis. The catalytic reorganization at the active site of aminoacyl tRNA synthetases (aaRSs) is driven by the loop motions. There remain lacunae of understanding concerning the catalytic loop dynamics in aaRSs. We analyzed the functional loop dynamics in seryl tRNA synthetase from Methanopyrus kandleri ( mk SerRS) and histidyl tRNA synthetases from Thermus thermophilus ( tt HisRS), respectively, using molecular dynamics. Results confirm that the motif 2 loop and other active site loops are flexible spots within the catalytic domain. Catalytic residues of the loops form a network of interaction with the substrates to form a reactive state. The loops undergo transitions between closed state and open state and the relaxation of the constituent residues occurs in femtosecond to nanosecond time scale. Order parameters are higher for constituent catalytic residues which form a specific network of interaction with the substrates to form a reactive state compared to the Gly residues within the loop. The development of interaction is supported from mutation studies where the catalytic domain with mutated loop exhibits unfavorable binding energy with the substrates. During the open-close motion of the loops, the catalytic residues make relaxation by ultrafast librational motion as well as fast diffusive motion and subsequently relax rather slowly via slower diffusive motion. The Gly residues act as a hinge to facilitate the loop closing and opening by their faster relaxation behavior. The role of bound water is analyzed by comparing implicit solvent-based and explicit solvent-based simulations. Loops fail to form catalytically competent geometry in absence of water. The present result, for the first time reveals the nature of the active site loop dynamics in aaRS and their influence on catalysis.

Estimates of ground-water recharge, base flow, and stream reach gains and losses in the Willamette River basin, Oregon

USGS Publications Warehouse

Lee, Karl K.; Risley, John C.

2002-03-19

Precipitation-runoff models, base-flow-separation techniques, and stream gain-loss measurements were used to study recharge and ground-water surface-water interaction as part of a study of the ground-water resources of the Willamette River Basin. The study was a cooperative effort between the U.S. Geological Survey and the State of Oregon Water Resources Department. Precipitation-runoff models were used to estimate the water budget of 216 subbasins in the Willamette River Basin. The models were also used to compute long-term average recharge and base flow. Recharge and base-flow estimates will be used as input to a regional ground-water flow model, within the same study. Recharge and base-flow estimates were made using daily streamflow records. Recharge estimates were made at 16 streamflow-gaging-station locations and were compared to recharge estimates from the precipitation-runoff models. Base-flow separation methods were used to identify the base-flow component of streamflow at 52 currently operated and discontinued streamflow-gaging-station locations. Stream gain-loss measurements were made on the Middle Fork Willamette, Willamette, South Yamhill, Pudding, and South Santiam Rivers, and were used to identify and quantify gaining and losing stream reaches both spatially and temporally. These measurements provide further understanding of ground-water/surface-water interactions.

Maxwell displacement current allows to study structural changes of gramicidin A in monolayers at the air-water interface.

PubMed

Vitovic, Pavol; Weis, Martin; Tomcík, Pavol; Cirák, Július; Hianik, Tibor

2007-05-01

We applied methods of measurement Maxwell displacement current (MDC) pressure-area isotherms and dipole potential for analysis of the properties of gramicidin A (gA) and mixed gA/DMPC monolayers at an air-water interface. The MDC method allowed us to observe the kinetics of formation of secondary structure of gA in monolayers at an air-water interface. We showed, that secondary structure starts to form at rather low area per molecule at which gA monolayers are in gaseous state. Changes of the MDC during compression can be attributed to the reorientation of dipole moments in a gA double helix at area 7 nm(2)/molecule, followed by the formation of intertwined double helix of gA. The properties of gA in mixed monolayers depend on the molar fraction of gA/DMPC. At higher molar fractions of gA (around 0.5) the shape of the changes of dipole moment of mixed monolayer was similar to that for pure gA. The analysis of excess free energy in a gel (18( ) degrees C) and in a liquid-crystalline phase (28( ) degrees C) allowed us to show influence of the monolayer structural state on the interaction between gA and the phospholipids. In a gel state and at the gA/DMPC molar ratio below 0.17 the aggregates of gA were formed, while above this molar ratio gA interacts favorably with DMPC. In contrast, for DMPC in a liquid-crystalline state aggregation of gA was observed for all molar fractions studied. The effect of formation ordered structures between gA and DMPC is more pronounced at low temperatures.

Hydrophobic interactions of sucralose with protein structures.

PubMed

Shukla, Nimesh; Pomarico, Enrico; Hecht, Cody J S; Taylor, Erika A; Chergui, Majed; Othon, Christina M

2018-02-01

Sucralose is a commonly employed artificial sweetener that appears to destabilize protein native structures. This is in direct contrast to the bio-preservative nature of its natural counterpart, sucrose, which enhances the stability of biomolecules against environmental stress. We have further explored the molecular interactions of sucralose as compared to sucrose to illuminate the origin of the differences in their bio-preservative efficacy. We show that the mode of interactions of sucralose and sucrose in bulk solution differ subtly through the use of hydration dynamics measurement and computational simulation. Sucralose does not appear to disturb the native state of proteins for moderate concentrations (<0.2 M) at room temperature. However, as the concentration increases, or in the thermally stressed state, sucralose appears to differ in its interactions with protein leading to the reduction of native state stability. This difference in interaction appears weak. We explored the difference in the preferential exclusion model using time-resolved spectroscopic techniques and observed that both molecules appear to be effective reducers of bulk hydration dynamics. However, the chlorination of sucralose appears to slightly enhance the hydrophobicity of the molecule, which reduces the preferential exclusion of sucralose from the protein-water interface. The weak interaction of sucralose with hydrophobic pockets on the protein surface differs from the behavior of sucrose. We experimentally followed up upon the extent of this weak interaction using isothermal titration calorimetry (ITC) measurements. We propose this as a possible origin for the difference in their bio-preservative properties. Copyright © 2017 Elsevier Inc. All rights reserved.

An interacting spin-flip model for one-dimensional proton conduction

NASA Astrophysics Data System (ADS)

Chou, Tom

2002-05-01

A discrete asymmetric exclusion process (ASEP) is developed to model proton conduction along one-dimensional water wires. Each lattice site represents a water molecule that can be in only one of three states; protonated, left-pointing and right-pointing. Only a right- (left-) pointing water can accept a proton from its left (). Results of asymptotic mean field analysis and Monte Carlo simulations for the three-species, open boundary exclusion model are presented and compared. The mean field results for the steady-state proton current suggest a number of regimes analogous to the low and maximal current phases found in the single-species ASEP (Derrida B 1998 Phys. Rep. 301 65-83). We find that the mean field results are accurate (compared with lattice Monte Carlo simulations) only in certain regimes. Refinements and extensions including more elaborate forces and pore defects are also discussed.

A direct ab initio molecular dynamics (MD) study on the benzophenone-water 1 : 1 complex.

PubMed

Tachikawa, Hiroto; Iyama, Tetsuji; Kato, Kohichi

2009-07-28

Direct ab initio molecular dynamics (MD) method has been applied to a benzophenone-water 1 : 1 complex Bp(H(2)O) and free benzophenone (Bp) to elucidate the effects of zero-point energy (ZPE) vibration and temperature on the absorption spectra of Bp(H(2)O). The n-pi transition of free-Bp (S(1) state) was blue-shifted by the interaction with a water molecule, whereas three pi-pi transitions (S(2), S(3) and S(4)) were red-shifted. The effects of the ZPE vibration and temperature of Bp(H(2)O) increased the intensity of the n-pi transition of Bp(H(2)O) and caused broadening of the pi-pi transitions. In case of the temperature effect, the intensity of n-pi transition increases with increasing temperature. The electronic states of Bp(H(2)O) were discussed on the basis of the theoretical results.

Multi-Agent Many-Objective Robust Decision Making: Supporting Cooperative Regional Water Portfolio Planning in the Eastern United States

NASA Astrophysics Data System (ADS)

Herman, J. D.; Zeff, H. B.; Reed, P. M.; Characklis, G. W.

2013-12-01

In the Eastern United States, water infrastructure and institutional frameworks have evolved in a historically water-rich environment. However, large regional droughts over the past decade combined with continuing population growth have marked a transition to a state of water scarcity, for which current planning paradigms are ill-suited. Significant opportunities exist to improve the efficiency of water infrastructure via regional coordination, namely, regional 'portfolios' of water-related assets such as reservoirs, conveyance, conservation measures, and transfer agreements. Regional coordination offers the potential to improve reliability, cost, and environmental impact in the expected future state of the world, and, with informed planning, to improve robustness to future uncertainty. In support of this challenge, this study advances a multi-agent many-objective robust decision making (multi-agent MORDM) framework that blends novel computational search and uncertainty analysis tools to discover flexible, robust regional portfolios. Our multi-agent MORDM framework is demonstrated for four water utilities in the Research Triangle region of North Carolina, USA. The utilities supply nearly two million customers and have the ability to interact with one another via transfer agreements and shared infrastructure. We show that strategies for this region which are Pareto-optimal in the expected future state of the world remain vulnerable to performance degradation under alternative scenarios of deeply uncertain hydrologic and economic factors. We then apply the Patient Rule Induction Method (PRIM) to identify which of these uncertain factors drives the individual and collective vulnerabilities for the four cooperating utilities. Our results indicate that clear multi-agent tradeoffs emerge for attaining robustness across the utilities. Furthermore, the key factor identified for improving the robustness of the region's water supply is cooperative demand reduction. This type of approach is critically important given the risks and challenges posed by rising supply development costs, limits on new infrastructure, growing water demands and the underlying uncertainties associated with climate change. The proposed framework serves as a planning template for other historically water-rich regions which must now confront the reality of impending water scarcity.

Ultrafast Hydration Dynamics and Coupled Water-Protein Fluctuations in Apomyoglobin

NASA Astrophysics Data System (ADS)

Yang, Yi; Zhang, Luyuan; Wang, Lijuan; Zhong, Dongping

2009-06-01

Protein hydration dynamics are of fundamental importance to its structure and function. Here, we characterize the global solvation dynamics and anisotropy dynamics around the apomyoglobin surface in different conformational states (native and molten globule) by measuring the Stokes shift and anisotropy decay of tryptophan with femtosecond-resolved fluorescence upconversion. With site-directed mutagenesis, we designed sixteen mutants with one tryptophan in each, and placed the probe at a desirable position ranging from buried in the protein core to fully solvent-exposed on the protein surface. In all protein sites studied, two distinct solvation relaxations (1-8 ps and 20-200 ps) were observed, reflecting the initial collective water relaxation and subsequent hydrogen-bond network restructuring, respectively, and both are strongly correlated with protein's local structures and chemical properties. The hydration dynamics of the mutants in molten globule state are faster than those observed in native state, indicating that the protein becomes more flexible and less structured when its conformation is converted from fully-folded native state to partially-folded molten globule state. Complementary, fluorescence anisotropy dynamics of all mutants in native state show an increasing trend of wobbling times (40-260 ps) when the location of the probe is changed from a loop, to a lateral helix, and then, to the compact protein core. Such an increase in wobbling times is related to the local protein structural rigidity, which relates the interaction of water with side chains. The ultrafast hydration dynamics and related side-chain motion around the protein surface unravel the coupled water-protein fluctuations on the picosecond time scales and indicate that the local protein motions are slaved by hydrating water fluctuations.

Modeling U.S. water resources under climate change

NASA Astrophysics Data System (ADS)

Blanc, Elodie; Strzepek, Kenneth; Schlosser, Adam; Jacoby, Henry; Gueneau, Arthur; Fant, Charles; Rausch, Sebastian; Reilly, John

2014-04-01

Water is at the center of a complex and dynamic system involving climatic, biological, hydrological, physical, and human interactions. We demonstrate a new modeling system that integrates climatic and hydrological determinants of water supply with economic and biological drivers of sectoral and regional water requirement while taking into account constraints of engineered water storage and transport systems. This modeling system is an extension of the Massachusetts Institute of Technology (MIT) Integrated Global System Model framework and is unique in its consistent treatment of factors affecting water resources and water requirements. Irrigation demand, for example, is driven by the same climatic conditions that drive evapotranspiration in natural systems and runoff, and future scenarios of water demand for power plant cooling are consistent with energy scenarios driving climate change. To illustrate the modeling system we select "wet" and "dry" patterns of precipitation for the United States from general circulation models used in the Climate Model Intercomparison Project (CMIP3). Results suggest that population and economic growth alone would increase water stress in the United States through mid-century. Climate change generally increases water stress with the largest increases in the Southwest. By identifying areas of potential stress in the absence of specific adaptation responses, the modeling system can help direct attention to water planning that might then limit use or add storage in potentially stressed regions, while illustrating how avoiding climate change through mitigation could change likely outcomes.

A combined molecular dynamics and Monte Carlo simulation of the spatial distribution of energy deposition by proton beams in liquid water.

PubMed

Garcia-Molina, Rafael; Abril, Isabel; Heredia-Avalos, Santiago; Kyriakou, Ioanna; Emfietzoglou, Dimitris

2011-10-07

We have evaluated the spatial distribution of energy deposition by proton beams in liquid water using the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids), which combines molecular dynamics and Monte Carlo techniques and includes the main interaction phenomena between the projectile and the target constituents: (i) the electronic stopping force due to energy loss to target electronic excitations, including fluctuations due to the energy-loss straggling, (ii) the elastic scattering with the target nuclei, with their corresponding energy loss and (iii) the dynamical changes in projectile charge state due to electronic capture and loss processes. An important feature of SEICS is the accurate account of the excitation spectrum of liquid water, based on a consistent solid-state description of its energy-loss-function over the whole energy and momentum space. We analyse how the above-mentioned interactions affect the depth distribution of the energy delivered in liquid water by proton beams with incident energies of the order of several MeV. Our simulations show that the position of the Bragg peak is determined mainly by the stopping power, whereas its width can be attributed to the energy-loss straggling. Multiple elastic scattering processes contribute slightly only at the distal part of the Bragg peak. The charge state of the projectiles only changes when approaching the end of their trajectories, i.e. near the Bragg peak. We have also simulated the proton-beam energy distribution at several depths in the liquid water target, and found that it is determined mainly by the fluctuation in the energy loss of the projectile, evaluated through the energy-loss straggling. We conclude that a proper description of the target excitation spectrum as well as the inclusion of the energy-loss straggling is essential in the calculation of the proton beam depth-dose distribution.

Nonequilibrium Tricritical Point in a System with Long-Range Interactions

NASA Astrophysics Data System (ADS)

Antoniazzi, Andrea; Fanelli, Duccio; Ruffo, Stefano; Yamaguchi, Yoshiyuki Y.

2007-07-01

Systems with long-range interactions display a short-time relaxation towards quasistationary states whose lifetime increases with system size. With reference to the Hamiltonian mean field model, we here show that a maximum entropy principle, based on Lynden-Bell’s pioneering idea of “violent relaxation,” predicts the presence of out-of-equilibrium phase transitions separating the relaxation towards homogeneous (zero magnetization) or inhomogeneous (nonzero magnetization) quasistationary states. When varying the initial condition within a family of “water bags” with different initial magnetization and energy, first- and second-order phase transition lines are found that merge at an out-of-equilibrium tricritical point. Metastability is theoretically predicted and numerically checked around the first-order phase transition line.

Influence of the protonation state on the binding mode of methyl orange with cucurbiturils

NASA Astrophysics Data System (ADS)

He, Suhang; Sun, Xuzhuo; Zhang, Haibo

2016-03-01

Binding modes of methyl orange (MO) with cucurbiturils (CBs) have been investigated by Single Crystal X-ray Diffraction and NMR Spectroscopy. Detailed study of intermolecular interactions was supported by the Hirshfeld surface analysis. Protonation state of the anionic part of methyl orange has greatly influenced the binding mode of the complex. Stabilized by hydrogen bonding at the portal, hydrophobic and dispersion interactions in the cavity, the protonated methyl orange was deeply inserted into the cavity. On the contrary, the anionic methyl orange has been pushed towards the outside of the cavity by the electrostatic repulsion between the azo group and the portal oxygen. A ;water bridge; was found in MO@CB8 linking both host and guest via hydrogen bonds.

Protein structure and interactions in the solid state studied by small-angle neutron scattering.

PubMed

Curtis, Joseph E; McAuley, Arnold; Nanda, Hirsh; Krueger, Susan

2012-01-01

Small-angle neutron scattering (SANS) is uniquely qualified to study the structure of proteins in liquid and solid phases that are relevant to food science and biotechnological applications. We have used SANS to study a model protein, lysozyme, in both the liquid and water ice phases to determine its gross-structure, interparticle interactions and other properties. These properties have been examined under a variety of solution conditions before, during, and after freezing. Results for lysozyme at concentrations of 50 mg mL(-1) and 100 mg mL(-1), with NaCl concentrations of 0.4 M and 0 M, respectively, both in the liquid and frozen states, are presented and implications for food science are discussed.

Quantum-mechanical approach to predissociation of water dimers in the vibrational adiabatic representation: Importance of channel interactions.

PubMed

Mineo, H; Niu, Y L; Kuo, J L; Lin, S H; Fujimura, Y

2015-08-28

The results of application of the quantum-mechanical adiabatic theory to vibrational predissociation (VPD) of water dimers, (H2O)2 and (D2O)2, are presented. We consider the VPD processes including the totally symmetric OH mode of the dimer and the bending mode of the fragment. The VPD in the adiabatic representation is induced by breakdown of the vibrational adiabatic approximation, and two types of nonadiabatic coupling matrix elements are involved: one provides the VPD induced by the low-frequency dissociation mode and the other provides the VPD through channel interactions induced by the low-frequency modes. The VPD rate constants were calculated using the Fermi golden rule expression. A closed form for the nonadiabatic transition matrix element between the discrete and continuum states was derived in the Morse potential model. All of the parameters used were obtained from the potential surfaces of the water dimers, which were calculated by the density functional theory procedures. The VPD rate constants for the two processes were calculated in the non-Condon scheme beyond the so-called Condon approximation. The channel interactions in and between the initial and final states were taken into account, and those are found to increase the VPD rates by 3(1) orders of magnitude for the VPD processes in (H2O)2 ((D2O)2). The fraction of the bending-excited donor fragments is larger than that of the bending-excited acceptor fragments. The results obtained by quantum-mechanical approach are compared with both experimental and quasi-classical trajectory calculation results.

Hydrogen Production Cost Analysis | Hydrogen and Fuel Cells | NREL

Science.gov Websites

Analysis Hydrogen Production Cost Analysis This interactive map displays the results of a 2011 NREL analysis on the cost of hydrogen from electrolysis at potential sites across the United States. NREL analyzed the cost of hydrogen production via wind-based water electrolysis at 42 potential sites in 11

Can forest watershed management mitigate climate change effects on water resources

Treesearch

James M. Vose; Chelcy R. Ford; Stephanie Laseter; Salli Dymond; Ge Sun; Mary Beth Adams; Stephen Sebestyen; John Campbell; Charlie Luce; Devendra Amatya; Kelly Elder; Tamara Heartsill Scalley

2012-01-01

Long-term hydrology and climate data from United States Forest Service Experimental Forests and Ranges (EFR) provide critical information on the interactions among climate, streamflow, and forest management practices. We examined the relationships among streamflow responses to climate variation and forest management using long-term data. Analysis of climate data from a...

Can forest watershed management mitigate climate change impacts on water resources?

Treesearch

James M. Vose; Chelcy R. Ford; Stephanie Laseter; Salli Dymond; GE Sun; Mary Beth Adams; Stephen Sebestyen; John Campbell; Charles Luce; Devendra Amatya; Kelly Elder; Tamara. Heartsill-Scalley

2012-01-01

Long-term hydrology and climate data from United States Forest Service Experimental Forests and Ranges (EFR) provide critical information on the interactions among climate, streamflow, and forest management practices. We examined the relationships among streamflow responses to climate variation and forest management using long-term data. Analysis of climate data from a...

Diazatetraester 1H-pyrazole crowns as fluorescent chemosensors for AMPH, METH, MDMA (ecstasy), and dopamine.

PubMed

Reviriego, Felipe; Navarro, Pilar; García-España, Enrique; Albelda, M Teresa; Frías, Juan C; Domènech, Antonio; Yunta, Maria J R; Costa, Rubén; Ortí, Enrique

2008-11-20

The synthesis and steady-state fluorescence studies on the interaction with AMPH, METH, MDMA, and DA of two diazatetraester pyrazole crowns containing appended N-(9H-fluoren-9-yl) and N-(naphth-2-ylmethyl) functions, in a water/ethanol 70:30 mixture at physiological pH, are described.

Physical and Chemical Toeholds for Exoplanet Bioastronomy

NASA Technical Reports Server (NTRS)

Hoehler, Tori

2013-01-01

If a search for exoplanet life were mounted today, the likely focus would be to detect oxygen (or ozone) in the atmosphere of a water-bearing rocky planet orbiting roughly 1AU from a G-type star. This appropriately conservative and practical default is necessary in large part because biological input on the question of where and how to look for life has progressed little beyond a purely empirical reliance on the example of terrestrial biology. However, fundamental physical and chemical considerations may impose significant yet universal constraints on biological potential. The liquid water + oxygen paradigm will be considered as an example, with a focus on the question, is liquid water a prerequisite for life? . Life requires a solvent to mediate interactions among biological molecules. A key class of these interactions is molecular recognition with high specificity, which is essential for high fidelity catalysis and (especially) information processing. For example, to correctly reproduce a string consisting of 600,000 units of information (e.g., 600 kilobases, equivalent to the genome of the smallest free living terrestrial organisms) with a 90% success rate requires specificity greater than 10(exp 7):1 for the target molecule vs. incorrect alternatives. Such specificity requires (i) that the correct molecular association is energetically stabilized by at least 40 kJ/mol relative to alternatives, and (ii) that the system is able to sample among possible states (alternative molecular associations) rapidly enough to allow the system to fall under thermodynamic control and express the energetic stabilization. We argue that electrostatic interactions are required to confer the necessary energetic stabilization vs. a large library of molecular alternatives, and that a solvent with polarity and dielectric properties comparable to water is required for the system to sample among possible states and express thermodynamic control. Electrostatic associations can be made in non-polar solvents, but the resulting complexes are too stable to be "unmade" with sufficient frequency to confer thermodynamic control on the system. Such considerations suggest that water, or a solvent with properties very like water, is necessary to support high-fidelity information processing a feature that must be common to all biology and can therefore be considered a critical prerequisite for life.

Study of β-cyclodextrin inclusion complexes with volatile molecules geraniol and α-terpineol enantiomers in solid state and in solution

NASA Astrophysics Data System (ADS)

Ceborska, Magdalena; Szwed, Kamila; Asztemborska, Monika; Wszelaka-Rylik, Małgorzata; Kicińska, Ewa; Suwińska, Kinga

2015-11-01

Geraniol and α-terpineol are insoluble in water volatile compounds. α-Terpineol is a potentially important agent for medical applications. Formation of molecular complexes with β-cyclodextrin would lead to the increase of water solubility and bioavailability. β-Cyclodextrin forms 2:2 inclusion complexes with both enantiomers of α-terpineol and their precursor geraniol. Solid state complexes are thoroughly characterized by single X-ray crystallography and their stability over vast range of temperatures is proven by TG analysis. Intermolecular host-guest, host-host and guest-guest interactions give good insight into the nature of formed inclusion complexes. Stability constants of the complexes in solution are determined by HPLC.

Sagnac-interferometer-based fresnel flow probe.

PubMed

Tselikov, A; Blake, J

1998-10-01

We used a near-diffraction-limited flow or light-wave-interaction pipe to produce a Sagnac-interferometer-based Fresnel drag fluid flowmeter capable of detecting extremely small flow rates. An optimized design of the pipe along with the use of a state-of-the-art Sagnac interferometer results in a minimum-detectable water flow rate of 2.4 nl/s [1 drop/(5 h)]. The flowmeter's capability of measuring the water consumption by a small plant in real time has been demonstrated. We then designed an automated alignment system that finds and maintains the optimum fiber-coupling regime, which makes the applications of the Fresnel-drag-based flowmeters practical, especially if the length of the interaction pipe is long. Finally, we have applied the automatic alignment technique to an air flowmeter.

Humans in Biogeophysical Models: Colonial Period Human-Environment Interactions in the Northeastern United States

NASA Astrophysics Data System (ADS)

Parolari, A.; Greco, F.; Green, M.; Lally, M.; Hermans, C.

2008-12-01

Earth system models increasingly require representation of human activities and the important role they play in the environment. At the most fundamental level, human decisions are driven by the need to acquire basic resources - nutrients, energy, water, and space - each derived from the biogeophysical setting. Modern theories in Ecological Economics place these basic resources at the base of a consumption hierarchy (from subsistence to luxury resources) on which societies and economies are built. Human decisions at all levels of this hierarchy are driven by dynamic environmental, social, and economic factors. Therefore, models merging socio-economic and biogeophysical dynamics are required to predict the evolving relationship between humans and the hydrologic cycle. To provide an example, our study focuses on changes to the hydrologic cycle during the United States colonial period (1600 to 1800). Both direct, intentional, human water use (e.g. water supply, irrigation, or hydropower) and indirect, unintentional effects resulting from the use of other resources (e.g. deforestation or beaver trapping) are considered. We argue that water was not the limiting resource to either the Native or Colonist population growth. However, food and tobacco production and harvesting of beaver pelts led to indirect interventions and consequent changes in the hydrologic cycle. The analysis presented here suggests the importance of incorporating human decision- making dynamics with existing geophysical models to fully understand trajectories of human-environment interactions. Predictive tools of this type are critical to characterizing the long-term signature of humans on the landscape and hydrologic cycle.

Management of Reclaimed Produced Water in the Rocky Mountain States Enhanced with the Expanded U.S. Geological Survey Produced Waters Geochemical Database

NASA Astrophysics Data System (ADS)

Gans, K. D.; Blondes, M. S.; Reidy, M. E.; Conaway, C. H.; Thordsen, J. J.; Rowan, E. L.; Kharaka, Y. K.; Engle, M.

2016-12-01

The Rocky Mountain states; Wyoming, Colorado, Montana, New Mexico and Utah produce annually approximately 470,000 acre-feet (3.66 billion barrels) of produced water - water that coexists with oil and gas and is brought to the surface with the pumping of oil and gas wells. Concerns about severe drought, groundwater depletion, and contamination have prompted petroleum operators and water districts to examine the recycling of produced water. Knowledge of the geochemistry of produced waters is valuable in determining the feasibility of produced water reuse. Water with low salinity can be reclaimed for use inside and outside of the petroleum industry. Since a great proportion of petroleum wells in the Rocky Mountain states, especially coal-bed methane wells, have produced water with relatively low salinity (generally <10,000-40,000 mg/L TDS), reclaiming produced water could be important as a drought mitigation strategy, through the irrigation of farmland, blending of low salinity waters with existing drainage basins, re-use in the petroleum industry for hydraulic fracturing or enhanced oil recovery, and even for municipal uses, such as drinking water. The USGS Produced Waters Geochemical Database, available at http://eerscmap.usgs.gov/pwapp, has 60,000 data points in this region (this includes 35,000 new data points added to the 2002 database) and will facilitate studies on the management of produced water for reclamation in the Rocky Mountain region. Expanding on the USGS 2002 database, which contains geochemical analyses of major ions and total dissolved solids, the new data also include geochemical analyses of minor ions and stable isotopes. We have added an interactive web map application which allows the user to filter data on chosen fields (e.g. TDS < 35,000 mg/L). Using the web map application as well as more in-depth investigation on the full data set can provide critical insight for better management of produced waters in water-constrained regions of the Rocky Mountains.

Bovine insulin-phosphatidylcholine mixed Langmuir monolayers: behavior at the air-water interface.

PubMed

Pérez-López, S; Blanco-Vila, N M; Vila-Romeu, N

2011-08-04

The behavior of the binary mixed Langmuir monolayers of bovine insulin (INS) and phosphatidylcholine (PC) spread at the air-water interface was investigated under various subphase conditions. Pure and mixed monolayers were spread on water, on NaOH and phosphate-buffered solutions of pH 7.4, and on Zn(2+)-containing solutions. Miscibility and interactions between the components were studied on the basis of the analysis of the surface pressure (π)-mean molecular area (A) isotherms, surface compression modulus (C(s)(-1))-π curves, and plots of A versus mole fraction of INS (X(INS)). Our results indicate that intermolecular interactions between INS and PC depend on both the monolayer state and the structural characteristics of INS at the interface, which are strongly influenced by the subphase pH and salt content. Brewster angle microscopy (BAM) was applied to investigate the peptide aggregation pattern at the air-water interface in the presence of the studied lipid under any experimental condition investigated. The influence of the lipid on the INS behavior at the interface strongly depends on the subphase conditions.

A maximum entropy thermodynamics of small systems.

PubMed

Dixit, Purushottam D

2013-05-14

We present a maximum entropy approach to analyze the state space of a small system in contact with a large bath, e.g., a solvated macromolecular system. For the solute, the fluctuations around the mean values of observables are not negligible and the probability distribution P(r) of the state space depends on the intricate details of the interaction of the solute with the solvent. Here, we employ a superstatistical approach: P(r) is expressed as a marginal distribution summed over the variation in β, the inverse temperature of the solute. The joint distribution P(β, r) is estimated by maximizing its entropy. We also calculate the first order system-size corrections to the canonical ensemble description of the state space. We test the development on a simple harmonic oscillator interacting with two baths with very different chemical identities, viz., (a) Lennard-Jones particles and (b) water molecules. In both cases, our method captures the state space of the oscillator sufficiently well. Future directions and connections with traditional statistical mechanics are discussed.

Site Competition During Coadsorption of Acetone with Methanol and Water on TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Mingmin; Henderson, Michael A.

2011-08-02

The competitive interaction between acetone and two solvent molecules (methanol and water) for surface sites on rutile TiO2(110) was studied using temperature programmed desorption (TPD). On a vacuum reduced TiO2(110) surface, which possessed ~5% oxygen vacancy sites, excess methanol displaced preadsorbed acetone molecules to weakly bound and physisorbed desorption states below 200 K, whereas acetone was stabilized to 250 K against displacement by methanol on an oxidized surface through formation of an acetone-diolate species. These behaviors of acetone differ from the competitive interactions between acetone and water in that acetone is less susceptible to displacement by water. Examination of acetone+methanolmore » and acetone+water multilayer combinations shows that acetone is more compatible in water-ice films than in methanol-ice films, presumably because water has greater potential as a hydrogen-bond donor than does methanol. Acetone molecules displaced from the TiO2(110) surface by water are more likely to be retained in the near-surface region, having a greater opportunity to revisit the surface, than when methanol is used as a coadsorbate. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

Water use regimes: Characterizing direct human interaction with hydrologic systems

USGS Publications Warehouse

Weiskel, Peter K.; Vogel, Richard M.; Steeves, Peter A.; Zarriello, Philip J.; Desimone, Leslie A.; Ries, Kernell G.

2007-01-01

The sustainability of human water use practices is a rapidly growing concern in the United States and around the world. To better characterize direct human interaction with hydrologic systems (stream basins and aquifers), we introduce the concept of the water use regime. Unlike scalar indicators of anthropogenic hydrologic stress in the literature, the water use regime is a two‐dimensional, vector indicator that can be depicted on simple x‐y plots of normalized human withdrawals (hout) versus normalized human return flows (hin). Four end‐member regimes, natural‐flow‐dominated (undeveloped), human‐flow‐dominated (churned), withdrawal‐dominated (depleted), and return‐flow‐dominated (surcharged), are defined in relation to limiting values of hout and hin. For illustration, the water use regimes of 19 diverse hydrologic systems are plotted and interpreted. Several of these systems, including the Yellow River Basin, China, and the California Central Valley Aquifer, are shown to approach particular end‐member regimes. Spatial and temporal regime variations, both seasonal and long‐term, are depicted. Practical issues of data availability and regime uncertainty are addressed in relation to the statistical properties of the ratio estimators hout and hin. The water use regime is shown to be a useful tool for comparative water resources assessment and for describing both historic and alternative future pathways of water resource development at a range of scales.

Interaction of water vapor with silicate glass surfaces: Mass-spectrometric investigations

NASA Astrophysics Data System (ADS)

Kudriavtsev, Yu.; Asomoza-Palacio, R.; Manzanilla-Naim, L.

2017-05-01

The secondary ion mass-spectroscopy technique was used to study the results of hydration of borosilicate, aluminosilicate, and soda-lime silicate glasses in 1H2 18O water vapor containing 97% of the isotope 18O. It is shown that hydration of the surface of the soda-lime silicate glass occurs as a result of the ion-exchange reaction with alkali metals. In the case of borosilicate and aluminosilicate glasses, water molecules decompose on the glass surface, with the observed formation of hydrogenated layer in the glass being the result of a solid-state chemical reaction—presumably, with the formation of hydroxides from aluminum and boron oxides.

Interaction between Air Bubbles and Superhydrophobic Surfaces in Aqueous Solutions.

PubMed

Shi, Chen; Cui, Xin; Zhang, Xurui; Tchoukov, Plamen; Liu, Qingxia; Encinas, Noemi; Paven, Maxime; Geyer, Florian; Vollmer, Doris; Xu, Zhenghe; Butt, Hans-Jürgen; Zeng, Hongbo

2015-07-07

Superhydrophobic surfaces are usually characterized by a high apparent contact angle of water drops in air. Here we analyze the inverse situation: Rather than focusing on water repellency in air, we measure the attractive interaction of air bubbles and superhydrophobic surfaces in water. Forces were measured between microbubbles with radii R of 40-90 μm attached to an atomic force microscope cantilever and submerged superhydrophobic surfaces. In addition, forces between macroscopic bubbles (R = 1.2 mm) at the end of capillaries and superhydrophobic surfaces were measured. As superhydrophobic surfaces we applied soot-templated surfaces, nanofilament surfaces, micropillar arrays with flat top faces, and decorated micropillars. Depending on the specific structure of the superhydrophobic surfaces and the presence and amount of entrapped air, different interactions were observed. Soot-templated surfaces in the Cassie state showed superaerophilic behavior: Once the electrostatic double-layer force and a hydrodynamic repulsion were overcome, bubbles jumped onto the surface and fully merged with the entrapped air. On nanofilaments and micropillar arrays we observed in addition the formation of sessile bubbles with finite contact angles below 90° or the attachment of bubbles, which retained their spherical shape.

Molecular docking and molecular dynamics simulations of fumarate hydratase and its mutant H235N complexed with pyromellitic acid and citrate.

PubMed

Subasri, S; Chaudhary, Santosh Kumar; Sekar, K; Kesherwani, Manish; Velmurugan, D

2017-12-01

Fumarase catalyzes the reversible, stereospecific hydration/dehydration of fumarate to L-malate during the Kreb's cycle. In the crystal structure of the tetrameric fumarase, it was found that some of the active site residues S145, T147, N188 G364 and H235 had water-mediated hydrogen bonding interactions with pyromellitic acid and citrate which help to the protonation state for the conversion of fumarate to malate. When His 235 is mutated with Asn (H235N), water-mediated interactions were lost due to the shifting of active site water molecule by 0.7 Å away. Molecular dynamics (MD) simulations were also carried out by NAMD and analyzed using Assisted Model Building with Energy Refinement (AMBER) program to better understand the conformational stability and other aspects during the binding of pyromellitic acid and citrate with native and mutant FH. The role of hydrogen bonds and hydrophobic interactions was also analyzed. The present study confirms that the H235N mutation has a major effect on the catalytic activity of fumarase which is evident from the biochemical studies.

NYC Reservoirs Watershed Areas (HUC 12)

EPA Pesticide Factsheets

This NYC Reservoirs Watershed Areas (HUC 12) GIS layer was derived from the 12-Digit National Watershed Boundary Database (WBD) at 1:24,000 for EPA Region 2 and Surrounding States. HUC 12 polygons were selected from the source based on interactively comparing these HUC 12s in our GIS with images of the New York City's Water Supply System Map found at http://www.nyc.gov/html/dep/html/drinking_water/wsmaps_wide.shtml. The 12 digit Hydrologic Units (HUCs) for EPA Region 2 and surrounding states (Northeastern states, parts of the Great Lakes, Puerto Rico and the USVI) are a subset of the National Watershed Boundary Database (WBD), downloaded from the Natural Resources Conservation Service (NRCS) Geospatial Gateway and imported into the EPA Region 2 Oracle/SDE database. This layer reflects 2009 updates to the WBD that included new boundary data for New York and New Jersey.

Military Hydrology: Report 18, State-of-the-Art Review and Annotated Bibliography of Radar-Rain Gage Relations and Short-Term Weather Forecasting

DTIC Science & Technology

1991-04-01

conducted in four areas: (a) weather-hydrology interactions, (b) state of the ground, (c) streamflow , and (d) water supply. 4. Previously published...wavelengths having the greatest losses . Eccles (1978) had shown some success at figuring rainfall rates using dual wavelength radars and measuring differential...evaporation losses of up to 15 percent using the Mar- shall-Palmer (1948) drop size distribution with a temperature of 200 C and a relative humidity of 80

Decision Support for Integrated Energy-Water Planning

NASA Astrophysics Data System (ADS)

Tidwell, V. C.; William, H.; Klise, G.; Kobos, P. H.; Malczynski, L. A.

2008-12-01

Currently, electrical power generation uses about 140 billion gallons of water per day accounting for over 40% of all freshwater withdrawals thus competing with irrigated agriculture as the leading user of water. To meet their demand for water, proposed power plants must often target waterways and aquifers prone to overdraft or which may be home to environmentally sensitive species. Acquisition of water rights, permits and public support may therefore be a formidable hurdle when licensing new power plants. Given these current difficulties, what does the future hold when projected growth in population and the economy may require a 30% increase in power generation capacity by 2025? Technology solutions can only take us so far, as noted by the National Energy-Water Roadmap Exercise. This roadmap identified the need for long-term and integrated resource planning supported with scientifically credible models as a leading issue. To address this need a decision support framework is being developed that targets the shared needs of energy and water producers, resource managers, regulators, and decision makers at the federal, state and local levels. The framework integrates analysis and optimization capabilities to help identify potential trade-offs, and "best" alternatives among an overwhelming number of energy/water options and objectives. The decision support tool is comprised of three basic elements: a system dynamics model coupling the physical and economic systems important to integrated energy-water planning and management; an optimization toolbox; and a software wrapper that integrates the aforementioned elements along with additional external energy/water models, databases, and visualization products. An interactive interface allows direct interaction with the model and access to real-time results organized according to a variety of reference systems, e.g., from a political, watershed, or electric power grid perspective. With this unique synthesis of various perspectives, the tool may help highlight looming changes where policy, technical, economic, and data collection options may alleviate stresses within the underlying water systems that support electricity generation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04- 94AL85000.

Supercooled and glassy water: Metastable liquid(s), amorphous solid(s), and a no-man's land

NASA Astrophysics Data System (ADS)

Handle, Philip H.; Loerting, Thomas; Sciortino, Francesco

2017-12-01

We review the recent research on supercooled and glassy water, focusing on the possible origins of its complex behavior. We stress the central role played by the strong directionality of the water-water interaction and by the competition between local energy, local entropy, and local density. In this context we discuss the phenomenon of polyamorphism (i.e., the existence of more than one disordered solid state), emphasizing both the role of the preparation protocols and the transformation between the different disordered ices. Finally, we present the ongoing debate on the possibility of linking polyamorphism with a liquid-liquid transition that could take place in the no-man's land, the temperature-pressure window in which homogeneous nucleation prevents the investigation of water in its metastable liquid form.

Comparison of Intermolecular Forces in Anhydrous Sorbitol and Solvent Cocrystals.

PubMed

Dierks, Teresa M; Korter, Timothy M

2017-08-03

The hygroscopicity of solid sorbitol is important for its utilization as a sweetener in the pharmaceutical and food industries. The molecular foundations of sorbitol hydration characteristics are explored here using two solvated cocrystals, sorbitol-water and sorbitol-pyridine. In this work, solid-state density functional theory and terahertz time-domain spectroscopy were used to evaluate the relative stabilities of these cocrystals as compared to anhydrous sorbitol in terms of conformational and cohesive energies. The modification of the hydrogen-bonding network in crystalline sorbitol by solvent molecules gives new insight into the origins of the notable stability of sorbitol-water as compared to similar solids such as mannitol-water. In particular, the energy analysis reveals that the relative instability of the mannitol hydrate is based primarily in the lack of water-water interactions which provide considerable stabilization in the sorbitol-water crystal.

The Effects of Fine-scale Soil Moisture and Canopy Heterogeneities on Energy and Soil Water Fluxes in a Temperate Mixed Deciduous Forest

NASA Astrophysics Data System (ADS)

He, L.; Ivanov, V. Y.; Bohrer, G.; Maurer, K.; Vogel, C. S.; Moghaddam, M.

2011-12-01

Vegetation is heterogeneous at different scales, influencing spatially variable energy and water exchanges between land-surface and atmosphere. Current land surface parameterizations of large-scale models consider spatial variability at a scale of a few kilometers and treat vegetation cover as aggregated patches with uniform properties. However, the coupling mechanisms between fine-scale soil moisture, vegetation, and energy fluxes such as evapotranspiration are strongly nonlinear; the aggregation of surface variations may produce biased energy fluxes. This study aims to improve the understanding of the scale impact in atmosphere-biosphere-hydrosphere interactions, which affects predictive capabilities of land surface models. The study uses a high-resolution, physically-based ecohydrological model tRIBS + VEGGIE as a data integration tool to upscale the heterogeneity of canopy distribution resolved at a few meters to the watershed scale. The study was carried out for a spatially heterogeneous, temperate mixed forest environment of Northern Michigan located near the University of Michigan Biological Station (UMBS). Energy and soil water dynamics were simulated at the tree-canopy resolution in the horizontal plane for a small domain (~2 sq. km) located within a footprint of the AmeriFlux tower. A variety of observational data were used to constrain and confirm the model, including a 3-m profile continuous soil moisture dataset and energy flux data (measured at the AmeriFlux tower footprint). A scenario with a spatially uniform canopy, corresponding to the commonly used 'big-leaf' scheme in land surface parameterizations was used to infer the effects of coarse-scale averaging. To gain insights on how heterogeneous canopy and soil moisture interact and contribute to the domain-averaged transpiration, several scenarios of tree-scale leaf area and soil moisture spatial variability were designed. Specifically, for the same mean states, the scenarios of variability of canopy biomass account for the spatial distribution of photosynthesis (and thus the stomatal resistance), the aerodynamic and leaf boundary layer resistances as well as the differential radiation forcing due to tall tree exposure and lateral shading of short trees. The numerical experiments show that by transpiring spatially varying amounts of water, heterogeneous canopies adjust the spatial soil water state to the scaled inverse of the canopy biomass regardless of the initial moisture state. Such a spatial distribution can be further wiped out because of the differential water stress. The aggregation of canopy-scale atmosphere-biosphere-hydrosphere interactions demonstrates non-linear relationship between soil moisture and evapotranspiration, influencing domain-averaged energy fluxes.

Microfluidic Extraction of Biomarkers using Water as Solvent

NASA Technical Reports Server (NTRS)

Amashukeli, Xenia; Manohara, Harish; Chattopadhyay, Goutam; Mehdi, Imran

2009-01-01

A proposed device, denoted a miniature microfluidic biomarker extractor (mu-EX), would extract trace amounts of chemicals of interest from samples, such as soils and rocks. Traditionally, such extractions are performed on a large scale with hazardous organic solvents; each solvent capable of dissolving only those molecules lying within narrow ranges of specific chemical and physical characteristics that notably include volatility, electric charge, and polarity. In contrast, in the mu-EX, extractions could be performed by use of small amounts (typically between 0.1 and 100 L) of water as a universal solvent. As a rule of thumb, in order to enable solvation and extraction of molecules, it is necessary to use solvents that have polarity sufficiently close to the polarity of the target molecules. The mu-EX would make selection of specific organic solvents unnecessary, because mu-EX would exploit a unique property of liquid water: the possibility of tuning its polarity to match the polarity of organic solvents appropriate for extraction of molecules of interest. The change of the permittivity of water would be achieved by exploiting interactions between the translational states of water molecules and an imposed electromagnetic field in the frequency range of 300 to 600 GHz. On a molecular level, these interactions would result in disruption of the three-dimensional hydrogen-bonding network among liquid-water molecules and subsequent solvation and hydrolysis of target molecules. The mu-EX is expected to be an efficient means of hydrolyzing chemical bonds in complex macromolecules as well and, thus, enabling analysis of the building blocks of these complex chemical systems. The mu-EX device would include a microfluidic channel, part of which would lie within a waveguide coupled to an electronically tuned source of broad-band electromagnetic radiation in the frequency range from 300 to 600 GHz (see figure). The part of the microfluidic channel lying in the waveguide would constitute an interaction volume. The dimensions of the interaction volume would be chosen in accordance with the anticipated amount of solid sample material needed to ensure extraction of sufficient amount of target molecules for detection and analysis. By means that were not specified at the time of reporting the information for this article, the solid sample material would be placed in the interaction volume. Then the electromagnetic field would be imposed within the waveguide and water would be pumped through the interaction volume to effect the extraction.

Local Interactions of Hydrometeors by Diffusion in Mixed-Phase Clouds

NASA Astrophysics Data System (ADS)

Baumgartner, Manuel; Spichtinger, Peter

2017-04-01

Mixed-phase clouds, containing both ice particles and liquid droplets, are important for the Earth-Atmosphere system. They modulate the radiation budget by a combination of albedo effect and greenhouse effect. In contrast to liquid water clouds, the radiative impact of clouds containing ice particles is still uncertain. Scattering and absorption highly depends in microphysical properties of ice crystals, e.g. size and shape. In addition, most precipitation on Earth forms via the ice phase. Thus, better understanding of ice processes as well as their representation in models is required. A key process for determining shape and size of ice crystals is diffusional growth. Diffusion processes in mixed-phase clouds are highly uncertain; in addition they are usually highly simplified in cloud models, especially in bulk microphysics parameterizations. The direct interaction between cloud droplets and ice particles, due to spatial inhomogeneities, is ignored; the particles can only interact via their environmental conditions. Local effects as supply of supersaturation due to clusters of droplets around ice particles are usually not represented, although they form the physical basis of the Wegener-Bergeron-Findeisen process. We present direct numerical simulations of the interaction of single ice particles and droplets, especially their local competition for the available water vapor. In addition, we show an approach to parameterize local interactions by diffusion. The suggested parameterization uses local steady-state solutions of the diffusion equations for water vapor for an ice particle as well as a droplet. The individual solutions are coupled together to obtain the desired interaction. We show some results of the scheme as implemented in a parcel model.

Water levels and groundwater and surface-water exchanges in lakes of the northeast Twin Cities Metropolitan Area, Minnesota, 2002 through 2015

USGS Publications Warehouse

Jones, Perry M.; Trost, Jared J.; Erickson, Melinda L.

2016-10-19

OverviewThis study assessed lake-water levels and regional and local groundwater and surface-water exchanges near northeast Twin Cities Metropolitan Area lakes applying three approaches: statistical analysis, field study, and groundwater-flow modeling.  Statistical analyses of lake levels were completed to assess the effect of physical setting and climate on lake-level fluctuations of selected lakes. A field study of groundwater and surface-water interactions in selected lakes was completed to (1) estimate potential percentages of surface-water contributions to well water across the northeast Twin Cities Metropolitan Area, (2) estimate general ages for waters extracted from the wells, and (3) assess groundwater inflow to lakes and lake-water outflow to aquifers downgradient from White Bear Lake.  Groundwater flow was simulated using a steady-state, groundwater-flow model to assess regional groundwater and surface-water exchanges and the effects of groundwater withdrawals, climate, and other factors on water levels of northeast Twin Cities Metropolitan Area lakes.

Hydrology of Cache Valley, Cache County, Utah, and adjacent part of Idaho, with emphasis on simulation of ground-water flow

USGS Publications Warehouse

Kariya, Kim A.; Roark, D. Michael; Hanson, Karen M.

1994-01-01

A hydrologic investigation of Cache Valley was done to better understand the ground-water system in unconsolidated basin-fill deposits and the interaction between ground water and surface water. Ground-water recharge occurs by infiltration of precipitation and unconsumed irrigation water, seepage from canals and streams, and subsurface inflow from adjacent consolidated rock and adjacent unconsolidated basin-fill deposit ground-water systems. Ground-water discharge occurs as seepage to streams and reservoirs, spring discharge, evapotranspiration, and withdrawal from wells.Water levels declined during 1984-90. Less-than-average precipitation during 1987-90 and increased pumping from irrigation and public-supply wells contributed to the declines.A ground-water-flow model was used to simulate flow in the unconsolidated basin-fill deposits. Data primarily from 1969 were used to calibrate the model to steady-state conditions. Transient-state calibration was done by simulating ground-water conditions on a yearly basis for 1982-90.A hypothetical simulation in which the dry conditions of 1990 were continued for 5 years projected an average lO-foot water-level decline between Richmond and Hyrum. When increased pumpage was simulated by adding three well fields, each pumping 10 cubic feet per second, in the Logan, Smithfield, and College Ward areas, water-level declines greater than 10 feet were projected in most of the southeastern part of the valley and discharge from springs and seepage to streams and reservoirs decreased.

Parametrization of 2,2,2-trifluoroethanol based on the generalized AMBER force field provides realistic agreement between experimental and calculated properties of pure liquid as well as water-mixed solutions.

PubMed

Vymětal, Jiří; Vondrášek, Jiří

2014-09-04

We present a novel force field model of 2,2,2-trifluoroethanol (TFE) based on the generalized AMBER force field. The model was exhaustively parametrized to reproduce liquid-state properties of pure TFE, namely, density, enthalpy of vaporization, self-diffusion coefficient, and population of trans and gauche conformers. The model predicts excellently other liquid-state properties such as shear viscosity, thermal expansion coefficient, and isotropic compressibility. The resulting model describes unexpectedly well the state equation of the liquid region in the range of 100 K and 10 MPa. More importantly, the proposed TFE model was optimized for use in combination with the TIP4P/Ew and TIP4P/2005 water models. It does not manifest excessive aggregation, which is known for other models, and therefore, it is supposed to more realistically describe the behavior of TFE/water mixtures. This was demonstrated by means of the Kirkwood-Buff theory of solutions and reasonable agreement with experimental data. We explored a considerable part of the parameter space and systematically tested individual combinations of parameters for performance in combination with the TIP4P/Ew and TIP4P/2005 water models. We observed ambiguity in parameters describing pure liquid TFE; however, most of them failed for TFE/water mixtures. We clearly demonstrated the necessity for balanced TFE-TFE, TFE-water, and water-water interactions which can be acquired only by employing implicit polarization correction in the course of parametrization.

Xingu Project - Integrating Land Use Planning and Water Governance in Amazonia: Towards Improved Freshwater Security in the Agricultural Frontier of Mato Grosso.

NASA Astrophysics Data System (ADS)

Krusche, A. V.; Ballester, M. V.; Neill, C.; Elsenbeer, H.; Johnson, M. S.; Coe, M. T.; Garavello, M.; Molina, S. G.; Empinotti, V.; Reichardt, F.; Deegan, L.; Harris, L.

2014-12-01

The main goal of this project is to identify how impacts from land conversion, cropland expansion and intensification of both crop and animal production interact to affect regional evapotranspiration, rainfall generation, river flooding, and water quality and stream habitats, allowing us to identify thresholds of change that will endanger agricultural production, livelihoods of non-agricultural settlers and the region's new urban population and infrastructure. We will survey the effects of this on (1) soybean farmers, (2) cattle ranchers, (3) small-scale farm families, (4) rural non-agriculturists, including fishers, and (5) urban residents and map their roles as stakeholders. We will also conduct current water use surveys among the different stakeholder groups, accompanied by questions on desired aspects for future freshwater security to identify targets for desirable outcomes of water governance strategies. These targets, together with the information on land use drivers, water quantity and quality and predicted scenarios for global changes will be incorporated into a fully integrated and interactive geospatially oriented socio-ecological model that can serve as framework for future water governance that enhances Freshwater Security in such systems. This is an international cooperation initiative lead by Brazil and with the participation of Canada, Germany and United States of America.

Interactions of glycine betaine with proteins: insights from volume and compressibility measurements.

PubMed

Shek, Yuen Lai; Chalikian, Tigran V

2013-01-29

We report the first application of volume and compressibility measurements to characterization of interactions between cosolvents (osmolytes) and globular proteins. Specifically, we measure the partial molar volumes and adiabatic compressibilities of cytochrome c, ribonuclease A, lysozyme, and ovalbumin in aqueous solutions of the stabilizing osmolyte glycine betaine (GB) at concentrations between 0 and 4 M. The fact that globular proteins do not undergo any conformational transitions in the presence of GB provides an opportunity to study the interactions of GB with proteins in their native states within the entire range of experimentally accessible GB concentrations. We analyze our resulting volumetric data within the framework of a statistical thermodynamic model in which each instance of GB interaction with a protein is viewed as a binding reaction that is accompanied by release of four water molecules. From this analysis, we calculate the association constants, k, as well as changes in volume, ΔV(0), and adiabatic compressibility, ΔK(S0), accompanying each GB-protein association event in an ideal solution. By comparing these parameters with similar characteristics determined for low-molecular weight analogues of proteins, we conclude that there are no significant cooperative effects involved in interactions of GB with any of the proteins studied in this work. We also evaluate the free energies of direct GB-protein interactions. The energetic properties of GB-protein association appear to scale with the size of the protein. For all proteins, the highly favorable change in free energy associated with direct protein-cosolvent interactions is nearly compensated by an unfavorable free energy of cavity formation (excluded volume effect), yielding a modestly unfavorable free energy for the transfer of a protein from water to a GB/water mixture.

Structure and hydration of membranes embedded with voltage-sensing domains.

PubMed

Krepkiy, Dmitriy; Mihailescu, Mihaela; Freites, J Alfredo; Schow, Eric V; Worcester, David L; Gawrisch, Klaus; Tobias, Douglas J; White, Stephen H; Swartz, Kenton J

2009-11-26

Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly charged S1-S4 voltage-sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated ion channels. Here we use neutron diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1-S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations and cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings indicate that voltage sensors have evolved to interact with the lipid membrane while keeping energetic and structural perturbations to a minimum, and that water penetrates the membrane, to hydrate charged residues and shape the transmembrane electric field.

Structure and hydration of membranes embedded with voltage-sensing domains

PubMed Central

Krepkiy, Dmitriy; Mihailescu, Mihaela; Freites, J. Alfredo; Schow, Eric V.; Worcester, David L.; Gawrisch, Klaus; Tobias, Douglas; White, Stephen H.; Swartz, Kenton J.

2009-01-01

Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly-charged S1–S4 voltage-sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated potassium channels. Here we use neutron diffraction, solid-state nuclear magnetic resonance spectroscopy, and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1–S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations, cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings reveal that voltage sensors have evolved to interact with the lipid membrane while keeping the energetic and structural perturbations to a minimum, and that water penetrates into the membrane to hydrate charged residues and shape the transmembrane electric field. PMID:19940918

A Neutron View of Proteins in Lipid Bilayers

NASA Astrophysics Data System (ADS)

White, Stephen

2012-02-01

Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly-charged S1-S4 voltage- sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated potassium channels. We have used neutron diffraction, solid-state nuclear magnetic resonance spectroscopy, and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1-S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations, cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings reveal that voltage sensors have evolved to interact with the lipid membrane while keeping the energetic and structural perturbations to a minimum, and that water penetrates into the membrane to hydrate charged residues and shape the transmembrane electric field.

Origins of protein denatured state compactness and hydrophobic clustering in aqueous urea: inferences from nonpolar potentials of mean force.

PubMed

Shimizu, Seishi; Chan, Hue Sun

2002-12-01

Free energies of pairwise hydrophobic association are simulated in aqueous solutions of urea at concentrations ranging from 0-8 M. Consistent with the expectation that hydrophobic interactions are weakened by urea, the association of relatively large nonpolar solutes is destabilized by urea. However, the association of two small methane-sized nonpolar solutes in water has the opposite tendency of being slightly strengthened by the addition of urea. Such size effects and the dependence of urea-induced stability changes on the configuration of nonpolar solutes are not predicted by solvent accessible surface area approaches based on energetic parameters derived from bulk-phase solubilities of model compounds. Thus, to understand hydrophobic interactions in proteins, it is not sufficient to rely solely on transfer experiment data that effectively characterize a single nonpolar solute in an aqueous environment but not the solvent-mediated interactions among two or more nonpolar solutes. We find that the m-values for the rate of change of two-methane association free energy with respect to urea concentration is a dramatically nonmonotonic function of the spatial separation between the two methanes, with a distance-dependent profile similar to the corresponding two-methane heat capacity of association in pure water. Our results rationalize the persistence of residual hydrophobic contacts in some proteins at high urea concentrations and explain why the heat capacity signature (DeltaC(P)) of a compact denatured state can be similar to DeltaC(P) values calculated by assuming an open random-coil-like unfolded state. Copyright 2002 Wiley-Liss, Inc.

Dynamic molecular oxygen production in cometary comae.

PubMed

Yao, Yunxi; Giapis, Konstantinos P

2017-05-08

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O 2 incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O 2 production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O 2 formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H 2 O + abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O 2 - . Subsequent photo-detachment leads to molecular O 2 , whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O 2 production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Dynamic molecular oxygen production in cometary comae

NASA Astrophysics Data System (ADS)

Yao, Yunxi; Giapis, Konstantinos P.

2017-05-01

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O2 incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O2 production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O2 formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H2O+ abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O2-. Subsequent photo-detachment leads to molecular O2, whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O2 production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Potential of mean force between two hydrophobic solutes in water.

PubMed

Southall, Noel T; Dill, Ken A

2002-12-10

We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory. Copyright 2002 Elsevier Science B.V.

Regional Analysis of Energy, Water, Land and Climate Interactions

NASA Astrophysics Data System (ADS)

Tidwell, V. C.; Averyt, K.; Harriss, R. C.; Hibbard, K. A.; Newmark, R. L.; Rose, S. K.; Shevliakova, E.; Wilson, T.

2014-12-01

Energy, water, and land systems interact in many ways and are impacted by management and climate change. These systems and their interactions often differ in significant ways from region-to-region. To explore the coupled energy-water-land system and its relation to climate change and management a simple conceptual model of demand, endowment and technology (DET) is proposed. A consistent and comparable analysis framework is needed as climate change and resource management practices have the potential to impact each DET element, resource, and region differently. These linkages are further complicated by policy and trade agreements where endowments of one region are used to meet demands in another. This paper reviews the unique DET characteristics of land, energy and water resources across the United States. Analyses are conducted according to the eight geographic regions defined in the 2014 National Climate Assessment. Evident from the analyses are regional differences in resources endowments in land (strong East-West gradient in forest, cropland and desert), water (similar East-West gradient), and energy. Demands likewise vary regionally reflecting differences in population density and endowment (e.g., higher water use in West reflecting insufficient precipitation to support dryland farming). The effect of technology and policy are particularly evident in differences in the energy portfolios across the eight regions. Integrated analyses that account for the various spatial and temporal differences in regional energy, water and land systems are critical to informing effective policy requirements for future energy, climate and resource management. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Chemical mixtures in potable water in the U.S.

USGS Publications Warehouse

Ryker, Sarah J.

2014-01-01

In recent years, regulators have devoted increasing attention to health risks from exposure to multiple chemicals. In 1996, the US Congress directed the US Environmental Protection Agency (EPA) to study mixtures of chemicals in drinking water, with a particular focus on potential interactions affecting chemicals' joint toxicity. The task is complicated by the number of possible mixtures in drinking water and lack of toxicological data for combinations of chemicals. As one step toward risk assessment and regulation of mixtures, the EPA and the Agency for Toxic Substances and Disease Registry (ATSDR) have proposed to estimate mixtures' toxicity based on the interactions of individual component chemicals. This approach permits the use of existing toxicological data on individual chemicals, but still requires additional information on interactions between chemicals and environmental data on the public's exposure to combinations of chemicals. Large compilations of water-quality data have recently become available from federal and state agencies. This chapter demonstrates the use of these environmental data, in combination with the available toxicological data, to explore scenarios for mixture toxicity and develop priorities for future research and regulation. Occurrence data on binary and ternary mixtures of arsenic, cadmium, and manganese are used to parameterize the EPA and ATSDR models for each drinking water source in the dataset. The models' outputs are then mapped at county scale to illustrate the implications of the proposed models for risk assessment and rulemaking. For example, according to the EPA's interaction model, the levels of arsenic and cadmium found in US groundwater are unlikely to have synergistic cardiovascular effects in most areas of the country, but the same mixture's potential for synergistic neurological effects merits further study. Similar analysis could, in future, be used to explore the implications of alternative risk models for the toxicity and interaction of complex mixtures, and to identify the communities with the highest and lowest expected value for regulation of chemical mixtures.

Effective Potentials for Folding Proteins

NASA Astrophysics Data System (ADS)

Chen, Nan-Yow; Su, Zheng-Yao; Mou, Chung-Yu

2006-02-01

A coarse-grained off-lattice model that is not biased in any way to the native state is proposed to fold proteins. To predict the native structure in a reasonable time, the model has included the essential effects of water in an effective potential. Two new ingredients, the dipole-dipole interaction and the local hydrophobic interaction, are introduced and are shown to be as crucial as the hydrogen bonding. The model allows successful folding of the wild-type sequence of protein G and may have provided important hints to the study of protein folding.

EnviroAtlas - Percentage of stream and water body shoreline lengths within 30 meters of >= 5% or >= 15% impervious cover by 12-Digit HUC for the Conterminous United States

EPA Pesticide Factsheets

This EnviroAtlas dataset shows the percentages of stream and water body shoreline lengths within 30 meters of impervious cover by 12-digit Hydrologic Unit (HUC) subwatershed in the contiguous U.S. Impervious cover alters the hydrologic behavior of streams and water bodies, promoting increased storm water runoff and lower stream flow during periods in between rainfall events. Impervious cover also promotes increased pollutant loads in receiving waters and degraded streamside habitat. This dataset shows were impervious cover occurs close to streams and water bodies, where it is likely to have a greater adverse impact on receiving waters. This dataset was produced by the US EPA to support research and online mapping activities related to the EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Numerical modeling of the agricultural-hydrologic system in Punjab, India

NASA Astrophysics Data System (ADS)

Nyblade, M.; Russo, T. A.; Zikatanov, L.; Zipp, K.

2017-12-01

The goal of food security for India's growing population is threatened by the decline in freshwater resources due to unsustainable water use for irrigation. The issue is acute in parts of Punjab, India, where small landholders produce a major quantity of India's food with declining groundwater resources. To further complicate this problem, other regions of the state are experiencing groundwater logging and salinization, and are reliant on canal systems for fresh water delivery. Due to the lack of water use records, groundwater consumption for this study is estimated with available data on crop yields, climate, and total canal water delivery. The hydrologic and agricultural systems are modeled using appropriate numerical methods and software. This is a state-wide hydrologic numerical model of Punjab that accounts for multiple aquifer layers, agricultural water demands, and interactions between the surface canal system and groundwater. To more accurately represent the drivers of agricultural production and therefore water use, we couple an economic crop optimization model with the hydrologic model. These tools will be used to assess and optimize crop choice scenarios based on farmer income, food production, and hydrologic system constraints. The results of these combined models can be used to further understand the hydrologic system response to government crop procurement policies and climate change, and to assess the effectiveness of possible water conservation solutions.

A quantitative analysis of hydraulic interaction processes in stream-aquifer systems

DOE PAGES

Wang, Wenke; Dai, Zhenxue; Zhao, Yaqian; ...

2016-01-28

The hydraulic relationship between the stream and aquifer can be altered from hydraulic connection to disconnection when the pumping rate exceeds the maximum seepage flux of the streambed. This study proposes to quantitatively analyze the physical processes of stream-aquifer systems from connection to disconnection. A free water table equation is adopted to clarify under what conditions a stream starts to separate hydraulically from an aquifer. Both the theoretical analysis and laboratory tests have demonstrated that the hydraulic connectedness of the stream-aquifer system can reach a critical disconnection state when the horizontal hydraulic gradient at the free water surface is equalmore » to zero and the vertical is equal to 1. A boundary-value problem for movement of the critical point of disconnection is established for an analytical solution of the inverted water table movement beneath the stream. The result indicates that the maximum distance or thickness of the inverted water table is equal to the water depth in the stream, and at a steady state of disconnection, the maximum hydraulic gradient at the streambed center is 2. In conclusion, this study helps us to understand the hydraulic phenomena of water flow near streams and accurately assess surface water and groundwater resources.« less

A coupled modeling framework of the co-evolution of humans and water: case study of Tarim River Basin, western China

NASA Astrophysics Data System (ADS)

Liu, D.; Tian, F.; Lin, M.; Sivapalan, M.

2014-04-01

The complex interactions and feedbacks between humans and water are very essential issues but are poorly understood in the newly proposed discipline of socio-hydrology (Sivapalan et al., 2012). An exploratory model with the appropriate level of simplification can be valuable to improve our understanding of the co-evolution and self-organization of socio-hydrological systems driven by interactions and feedbacks operating at different scales. In this study, a simple coupled modeling framework for socio-hydrology co-evolution is developed for the Tarim River Basin in Western China, and is used to illustrate the explanatory power of such a model. The study area is the mainstream of the Tarim River, which is divided into two modeling units. The socio-hydrological system is composed of four parts, i.e. social sub-system, economic sub-system, ecological sub-system, and hydrological sub-system. In each modeling unit, four coupled ordinary differential equations are used to simulate the dynamics of the social sub-system represented by human population, the economic sub-system represented by irrigated crop area, the ecological sub-system represented by natural vegetation cover and the hydrological sub-system represented by stream discharge. The coupling and feedback processes of the four dominant sub-systems (and correspondingly four state variables) are integrated into several internal system characteristics interactively and jointly determined by themselves and by other coupled systems. For example, the stream discharge is coupled to the irrigated crop area by the colonization rate and mortality rate of the irrigated crop area in the upper reach and the irrigated area is coupled to stream discharge through irrigation water consumption. In a similar way, the stream discharge and natural vegetation cover are coupled together. The irrigated crop area is coupled to human population by the colonization rate and mortality rate of the population. The inflow of the lower reach is determined by the outflow from the upper reach. The natural vegetation cover in the lower reach is coupled to the outflow from the upper reach and governed by regional water resources management policy. The co-evolution of the Tarim socio-hydrological system is then analyzed within this modeling framework to gain insights into the overall system dynamics and its sensitivity to the external drivers and internal system variables. In the modeling framework, the state of each subsystem is holistically described by one state variable and the framework is flexible enough to comprise more processes and constitutive relationships if they are needed to illustrate the interaction and feedback mechanisms of the human-water system.

Non-covalent interactions between thio-caffeine derivatives and water-soluble porphyrin in ethanol-water environment

NASA Astrophysics Data System (ADS)

Lipke, Agnieszka; Makarska-Bialokoz, Magdalena; Sierakowska, Arleta; Jasiewicz, Beata

2018-03-01

To determine the binding interactions and ability to form the non-covalent systems, the association process between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H2TTMePP) and a series of five structurally diverse thio-caffeine analogues has been studied in ethanol and ethanol-water solutions, analyzing its absorption and steady-state fluorescence spectra. The porphyrin fluorescence lifetimes in the systems studied were established as well. During the titration with thio-caffeine compounds the slight bathochromic effect and considerable hypochromicity of the porphyrin Soret band maximum can be noted. The fluorescence quenching effect observed for interactions in H2TTMePP - thio-caffeine derivative systems, as well as the order of binding and fluorescence quenching constants (of 105-103 mol- 1) suggest the existence of the mechanism of static quenching due to the formation of non-covalent and non-fluorescent stacking complexes. In all the systems studied the phenomenon of the fractional accessibility of the fluorophore for the quencher was observed as well. Additionally, the specific binding interactions, due to the changes in reaction environment polarity, can be observed. It was found that thio-caffeine compounds can quench the porphyrin fluorescence according to the structure of thio-substituent in caffeine molecule. The obtained results can be potentially useful from scientific, therapeutic or environmental points of view.

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model

PubMed Central

Bauer, Brad A.; Patel, Sandeep

2009-01-01

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of Tc=623 K, ρc=0.351 g∕cm3, and Pc=250.9 atm, which are in good agreement with experimental values of Tc=647.1 K, ρc=0.322 g∕cm3, and Pc=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (Tc=631 K and ρc=0.308 g∕cm3). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300–450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended. PMID:19725623

Properties of water along the liquid-vapor coexistence curve via molecular dynamics simulations using the polarizable TIP4P-QDP-LJ water model.

PubMed

Bauer, Brad A; Patel, Sandeep

2009-08-28

We present an extension of the TIP4P-QDP model, TIP4P-QDP-LJ, that is designed to couple changes in repulsive and dispersive nonbond interactions to changes in polarizability. Polarizability is intimately related to the dispersion component of classical force field models of interactions, and we explore the effect of incorporating this connection explicitly on properties along the liquid-vapor coexistence curve of pure water. Parametrized to reproduce condensed-phase liquid water properties at 298 K, the TIP4P-QDP-LJ model predicts density, enthalpy of vaporization, self-diffusion constant, and the dielectric constant at ambient conditions to about the same accuracy as TIP4P-QDP but shows remarkable improvement in reproducing the liquid-vapor coexistence curve. TIP4P-QDP-LJ predicts critical constants of T(c)=623 K, rho(c)=0.351 g/cm(3), and P(c)=250.9 atm, which are in good agreement with experimental values of T(c)=647.1 K, rho(c)=0.322 g/cm(3), and P(c)=218 atm, respectively. Applying a scaling factor correction (obtained by fitting the experimental vapor-liquid equilibrium data to the law of rectilinear diameters using a three-term Wegner expansion) the model predicts critical constants (T(c)=631 K and rho(c)=0.308 g/cm(3)). Dependence of enthalpy of vaporization, self-diffusion constant, surface tension, and dielectric constant on temperature are shown to reproduce experimental trends. We also explore the interfacial potential drop across the liquid-vapor interface for the temperatures studied. The interfacial potential demonstrates little temperature dependence at lower temperatures (300-450 K) and significantly enhanced (exponential) dependence at elevated temperatures. Terms arising from the decomposition of the interfacial potential into dipole and quadrupole contributions are shown to monotonically approach zero as the temperature approaches the critical temperature. Results of this study suggest that self-consistently treating the coupling of phase-dependent polarizability with dispersion interactions in classical water force fields may be an important effect for the extension of polarizable water force fields to reproduce properties along the liquid-vapor coexistence envelope as well as near critical conditions. More importantly, the present study demonstrates the rather remarkable transferability of a water model parametrized to a single state point to other thermodynamic states. Further studies are recommended.

Kudzu-Goat Interactions--A Pilot Study

Treesearch

C. Bonsi; E. Rhoden; A. Woldeghebriel; P. Mount; S. Solaiman; R. Noble; G. Paris; Charles McMahon; H. Pearson; B. Cash

1992-01-01

The production and processing of forest products is a major industry in the State of Alabama. Current weed management and control practices rely heavily on the use of herbicides. With the risk of soil and water pollution associated with the use of some agricultural chemicals, the continuing use of such chemicals may become hazardous to human health. The need for...

EnviroAtlas - Agricultural Water Demand by 12-Digit HUC for the Conterminous United States

EPA Pesticide Factsheets

The national agricultural water demand metric provides insight into the amount of water currently used for agricultural irrigation in the contiguous United States. The values are based on 2005 irrigation water use; combined 2010 crop, 2006 land use, and 2001 remotely sensed irrigation location estimates; and have been summarized by watershed or 12-digit hydrologic unit code (HUC). Agricultural irrigation water use, as defined in this case, meets a variety of needs before, during, and after growing seasons (e.g., dust suppression, field preparation, chemical application, weed control, salt removal from root zones, frost protection, crop cooling, and harvesting). Estimates include self-supplied surface and groundwater, as well as supplies from irrigation-specific organizations (e.g., companies, districts, cooperatives, government). This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Hydrogeologic framework and groundwater/surface-water interactions of the Chehalis River basin, Washington

USGS Publications Warehouse

Gendaszek, Andrew S.

2011-01-01

The Chehalis River has the largest drainage basin of any river entirely contained within the State of Washington with a watershed of approximately 2,700 mi2 and has correspondingly diverse geology and land use. Demands for water resources have prompted the local citizens and governments of the Chehalis River basin to coordinate with Federal, State and Tribal agencies through the Chehalis Basin Partnership to develop a long-term watershed management plan. The recognition of the interdependence of groundwater and surface-water resources of the Chehalis River basin became the impetus for this study, the purpose of which is to describe the hydrogeologic framework and groundwater/surface-water interactions of the Chehalis River basin. Surficial geologic maps and 372 drillers' lithostratigraphic logs were used to generalize the basin-wide hydrogeologic framework. Five hydrogeologic units that include aquifers within unconsolidated glacial and alluvial sediments separated by discontinuous confining units were identified. These five units are bounded by a low permeability unit comprised of Tertiary bedrock. A water table map, and generalized groundwater-flow directions in the surficial aquifers, were delineated from water levels measured in wells between July and September 2009. Groundwater generally follows landsurface-topography from the uplands to the alluvial valley of the Chehalis River. Groundwater gradients are highest in tributary valleys such as the Newaukum River valley (approximately 23 cubic feet per mile), relatively flat in the central Chehalis River valley (approximately 6 cubic feet per mile), and become tidally influenced near the outlet of the Chehalis River to Grays Harbor. The dynamic interaction between groundwater and surface-water was observed through the synoptic streamflow measurements, termed a seepage run, made during August 2010, and monitoring of water levels in wells during the 2010 Water Year. The seepage run revealed an overall gain of 56.8 ± 23.7 cubic feet per second over 32.8 river miles (1.7 cubic feet per second per mile), and alternating gains and losses of streamflow ranging from -48.3 to 30.9 cubic feet per second per mile, which became more pronounced on the Chehalis River downstream of Grand Mound. However, most gains and losses were within measurement error. Groundwater levels measured in wells in unconsolidated sediments fluctuated with changes in stream stage, often within several hours. These fluctuations were set by precipitation events in the upper Chehalis River basin and tides of the Pacific Ocean in the lower Chehalis River basin.±

Perspective: A controversial benchmark system for water-oxide interfaces: H2O/TiO2(110)

NASA Astrophysics Data System (ADS)

Diebold, Ulrike

2017-07-01

The interaction of water with the single-crystalline rutile TiO2(110) surface has been the object of intense investigations with both experimental and computational methods. Not only is TiO2(110) widely considered the prototypical oxide surface, its interaction with water is also important in many applications where this material is used. At first, experimental measurements were hampered by the fact that preparation recipes for well-controlled surfaces had yet to be developed, but clear experimental evidence that water dissociation at defects including oxygen vacancies and steps emerged. For a perfect TiO2(110) surface, however, an intense debate has evolved whether or not water adsorbs as an intact molecule or if it dissociates by donating a proton to a so-called bridge-bonded surface oxygen atom. Computational studies agree that the energy difference between these two states is very small and thus depends sensitively on the computational setup and on the approximations used in density functional theory (DFT). While a recent molecular beam/STM experiment [Z.-T. Wang et al., Proc. Natl. Acad. Sci. U. S. A. 114(8), 1801-1805 (2017)] gives conclusive evidence for a slight preference (0.035 eV) for molecular water and a small activation energy of (0.36 eV) for dissociation, understanding the interface between liquid water and TiO2(110) arises as the next controversial frontier.

The Importance of Water for High Fidelity Information Processing and for Life

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Pohorille, Andrew

2011-01-01

Is water an absolute prerequisite for life? Life depends on a variety of non-covalent interactions among molecules, the nature of which is determined as much by the solvent in which they occur as by the molecules themselves. Catalysis and information processing, two essential functions of life, require non-covalent molecular recognition with very high specificity. For example, to correctly reproduce a string consisting of 600,000 units of information (e.g ., 600 kilobases, equivalent to the genome of the smallest free living terrestrial organisms) with a 90% success rate requires specificity > 107 : 1 for the target molecule vs. incorrect alternatives. Such specificity requires (i) that the correct molecular association is energetically stabilized by at least 40 kJ/mol relative to alternatives, and (ii) that the system is able to sample among possible states (alternative molecular associations) rapidly enough to allow the system to fall under thermodynamic control and express the energetic stabilization. We argue that electrostatic interactions are required to confer the necessary energetic stabilization vs. a large library of molecular alternatives, and that a solvent with polarity and dielectric properties comparable to water is required for the system to sample among possible states and express thermodynamic control. Electrostatic associations can be made in non-polar solvents, but the resulting complexes are too stable to be "unmade" with sufficient frequency to confer thermodynamic control on the system. An electrostatic molecular complex representing 3 units of information (e.g., 3 base pairs) with specificity > 107 per unit has a stability in non-polar solvent comparable to that of a carbon-carbon bond at room temperature. These considerations suggest that water, or a solvent with properties very like water, is necessary to support high-fidelity information processing, and can therefore be considered a critical prerequisite for life.

Plasma-based water purification: Challenges and prospects for the future

NASA Astrophysics Data System (ADS)

Foster, John E.

2017-05-01

Freshwater scarcity derived from seasonal weather variations, climate change, and over-development has led to serious consideration for water reuse. Water reuse involves the direct processing of wastewater for either indirect or directly potable water reuse. In either case, advanced water treatment technologies will be required to process the water to the point that it can be reused in a meaningful way. Additionally, there is growing concern regarding micropollutants, such as pharmaceuticals and personal care products, which have been detected in finished drinking water not removed by conventional means. The health impact of these contaminants in low concentration is not well understood. Pending regulatory action, the removal of these contaminants by water treatment plants will also require advanced technology. One new and emerging technology that could potentially address the removal of micropollutants in both finished drinking water as well as wastewater slated for reuse is plasma-based water purification. Plasma in contact with liquid water generates a host of reactive species that attack and ultimately mineralize contaminants in solution. This interaction takes place in the boundary layer or interaction zone centered at the plasma-liquid water interface. An understanding of the physical processes taking place at the interface, though poorly understood, is key to the optimization of plasma-based water purifiers. High electric field conditions, large density gradients, plasma-driven chemistries, and fluid dynamic effects prevail in this multiphase region. The region is also the source function for longer-lived reactive species that ultimately treat the water. Here, we review the need for advanced water treatment methods and in the process, make the case for plasma-based methods. Additionally, we survey the basic methods of interacting plasma with liquid water (including a discussion of breakdown processes in water), the current state of understanding of the physical processes taking place at the plasma-liquid interface, and the role these processes play in water purification. The development of plasma diagnostics usable in this multiphase environment along with modeling efforts aimed at elucidating physical processes taking place at the interface are also detailed. Key experiments that demonstrate the capability of plasma-based water treatment are also reviewed. The technical challenges to the implementation of plasma-based water reactors are also discussed. We conclude with a discussion of prospects for the future of plasma-based water purification.

Relationship between β-relaxation and structural stability of lysozyme: Microscopic insight on thermostabilization mechanism by trehalose from Raman spectroscopy experiments

NASA Astrophysics Data System (ADS)

Hédoux, Alain; Paccou, Laurent; Guinet, Yannick

2014-06-01

Raman investigations were carried out in the low-frequency and amide I regions on lysozyme aqueous solutions in absence and presence of trehalose. Raman spectroscopy gives the unique opportunity to analyze the protein and solvent dynamics in the low-frequency range while monitoring the unfolding process by capturing the spectrum of the amide I band. From the analysis of the quasielastic intensity, a dynamic change is firstly observed in a highly hydrated protein, around 70 °C, and interpreted in relation with the denaturation mechanism of the protein. The use of heavy water and partly deuterated trehalose gives clear information on protein-trehalose interactions in the native state of lysozyme (at room temperature) and during the thermal denaturation process of lysozyme. At room temperature, it was found that trehalose is preferentially excluded from the protein surface, and has a main effect on the tetrahedral local order of water molecules corresponding to a stiffening of the H-bond network in the solvent. The consequence is a significant reduction of the amplitude of fast relaxational motions, inducing a less marked dynamic transition shifted toward the high temperatures. Upon heating, interaction between trehalose and lysozyme is detected during the solvent penetration within the protein, i.e., while the native globular state softens into a molten globule (MG) state. Addition of trehalose reduces the protein flexibility in the MG state, improving the structural stability of the protein, and inhibiting the protein aggregation.

Linear response theory for long-range interacting systems in quasistationary states.

PubMed

Patelli, Aurelio; Gupta, Shamik; Nardini, Cesare; Ruffo, Stefano

2012-02-01

Long-range interacting systems, while relaxing to equilibrium, often get trapped in long-lived quasistationary states which have lifetimes that diverge with the system size. In this work, we address the question of how a long-range system in a quasistationary state (QSS) responds to an external perturbation. We consider a long-range system that evolves under deterministic Hamilton dynamics. The perturbation is taken to couple to the canonical coordinates of the individual constituents. Our study is based on analyzing the Vlasov equation for the single-particle phase-space distribution. The QSS represents a stable stationary solution of the Vlasov equation in the absence of the external perturbation. In the presence of small perturbation, we linearize the perturbed Vlasov equation about the QSS to obtain a formal expression for the response observed in a single-particle dynamical quantity. For a QSS that is homogeneous in the coordinate, we obtain an explicit formula for the response. We apply our analysis to a paradigmatic model, the Hamiltonian mean-field model, which involves particles moving on a circle under Hamiltonian dynamics. Our prediction for the response of three representative QSSs in this model (the water-bag QSS, the Fermi-Dirac QSS, and the Gaussian QSS) is found to be in good agreement with N-particle simulations for large N. We also show the long-time relaxation of the water-bag QSS to the Boltzmann-Gibbs equilibrium state. © 2012 American Physical Society

Water Accounting Priorities in the American West

NASA Astrophysics Data System (ADS)

Hanak, E.

2017-12-01

In regions facing water scarcity, understanding the water balance sheet—how much there is, who has claims to it, and what is actually being "spent"—is key to effectively managing supplies to meet a wide range of societal goals. This is a common challenge across the American West, a region needing to balance the water demands of large irrigated agricultural sectors, growing urban populations, and declining aquatic ecosystems—in a context of increasingly variable, and in some cases diminishing, water supplies. Many local urban water utilities, and some irrigation water suppliers, have developed sophisticated data systems for tracking water availability and use within their systems. But there are still major gaps in essential metrics at the scale of watersheds and river basins. On the supply side, key issues include understanding groundwater availability and surface-groundwater interactions. On the demand side, the biggest challenges relate to understanding groundwater use and return flows—the water that is returned to rivers or aquifers and is available for reuse. In addition, most states lack consistent accounting and data standards for sharing water availability, claims, and use information—and transparent systems for reporting information to users in ways that facilitates oversight and flexible tools such as water trading. Drawing on a detailed study of water accounting in 12 western states and 2 countries with similar water challenges (Escriva Bou et al. 2016, Accounting for Water in Dry Regions: A Comparative Review, Public Policy Institute of California), this talk provides insights on best practices that can help fill critical water accounting gaps.

Investigation of laser-tissue interaction in medicine by means of laser spectroscopic measurements

NASA Astrophysics Data System (ADS)

Lademann, Juergen; Weigmann, Hans-Juergen

1995-01-01

Toxic and carcinogenic substances were produced during laser application in medicine for the cutting and evaporation of tissue. The laser smoke presents a danger potential for the medical staff and the patients. The laser tissue interaction process was investigated by means of laser spectroscopic measurements which give the possibility of measuring metastable molecular states directly as a prerequisite to understand and to influence fundamental laser tissue interaction processes in order to reduce the amount of harmful chemicals. Highly excited atomic and molecular states and free radicals (CN, OH, C2, CH, CH2) have been detected applying spontaneous and laser induced fluorescence methods. It was found that the formation of harmful substances in the laser plumes can be reduced significantly by optimization of the surrounding gas atmosphere. A high content of oxygen or water in the interaction zone has been found, in agreement with the results of classical and analytical methods, as a suitable way to decrease pollutant emission. The experimental methods and the principal results are applicable not only in laser medicine but in laser material treatment generally.

Land-atmosphere interactions over the continental United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Xubin

This paper briefly discusses four suggested modifications for land surface modeling in climate models. The impact of the modifications on climate simulations is analyzed with the Biosphere-Atmosphere Transfer Scheme (BATS) land surface model. It is found that the modifications can improve BATS simulations. In particular, the sensitivity of BATS to the prescribed value of physical root fraction which cannot be observed from satellite remote sensing or field experiments is improved. These modifications significantly reduce the excessive summer land surface temperature over the continental United States simulated by the National Center for Atmospheric Research Community Climate Model (CCM2) coupled with BATS.more » A land-atmosphere interaction mechanism involving energy and water cycles is proposed to explain the results. 9 refs., 1 fig.« less

Measuring interactions between polydimethylsiloxane and serum proteins at the air-water interface.

PubMed

Liao, Zhengzheng; Hsieh, Wan-Ting; Baumgart, Tobias; Dmochowski, Ivan J

2013-07-30

The interaction between synthetic polymers and proteins at interfaces is relevant to basic science as well as a wide range of applications in biotechnology and medicine. One particularly common and important interface is the air-water interface (AWI). Due to the special energetics and dynamics of molecules at the AWI, the interplay between synthetic polymer and protein can be very different from that in bulk solution. In this paper, we applied the Langmuir-Blodgett technique and fluorescence microscopy to investigate how the compression state of polydimethylsiloxane (PDMS) film at the AWI affects the subsequent adsorption of serum protein [e.g., human serum albumin (HSA) or immunoglobulin G (IgG)] and the interaction between PDMS and protein. Of particular note is our observation of circular PDMS domains with micrometer diameters that form at the AWI in the highly compressed state of the surface film: proteins were shown to adsorb preferentially to the surface of these circular PDMS domains, accompanied by a greater than 4-fold increase in protein found in the interfacial film. The PDMS-only film and the PDMS-IgG composite film were transferred to cover glass, and platinum-carbon replicas of the transferred films were further characterized by scanning electron microscopy and atomic force microscopy. We conclude that the structure of the PDMS film greatly affects the amount and distribution of protein at the interface.

Reversible Self-Assembly of Water-Soluble Gold(I) Complexes.

PubMed

Aguiló, Elisabet; Moro, Artur J; Gavara, Raquel; Alfonso, Ignacio; Pérez, Yolanda; Zaccaria, Francesco; Guerra, Célia Fonseca; Malfois, Marc; Baucells, Clara; Ferrer, Montserrat; Lima, João Carlos; Rodríguez, Laura

2018-02-05

The reaction of the gold polymers containing bipyridyl and terpyridyl units, [Au(C≡CC 15 H 10 N 3 )] n and [Au(C≡CC 10 H 7 N 2 )] n , with the water-soluble phosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane gives rise to the formation of four gold(I) alkynyl complexes that self-assemble in water (H 2 O) and dimethyl sulfoxide (DMSO), through different intermolecular interactions, with an impact on the observed luminescence displayed by the supramolecular assemblies. A detailed analysis carried out by NMR studies performed in different DMSO/deuterated H 2 O mixtures indicates the presence of two different assembly modes in the aggregates: (i) chain assemblies, which are based mainly on aurophilic interactions, and (ii) stacked assemblies, which are based on Au···π and π···π interactions. These different supramolecular environments can also be detected by their intrinsic optical properties (differences in absorption and emission spectra) and are predicted by the changes in the relative binding energy from density functional theory calculations carried out in DMSO and H 2 O. Small-angle X-ray scattering (SAXS) experiments performed in the same mixture of solvents are in agreement with the formation of aggregates in all cases. The aromatic units chosen, bipyridine and terpyridine, allow the use of external stimuli to reversibly change the aggregation state of the supramolecular assemblies. Interaction with the Zn 2+ cation is observed to disassemble the aggregates, while encapsulating agents competing for Zn 2+ complexation revert the process to the aggregation stage, as verified by SAXS and NMR. The adaptive nature of the supramolecular assemblies to the metal-ion content is accompanied by significant changes in the absorption and emission spectra, signaling the aggregation state and also the content on Zn 2+ .

Dissociation energy and dynamics of water clusters

NASA Astrophysics Data System (ADS)

Ch'ng, Lee Chiat

The state-to-state vibrational predissociation (VP) dynamics of water clusters were studied following excitation of a vibrational mode of each cluster. Velocity-map imaging (VMI) and resonance-enhanced multiphoton ionization (REMPI) were used to determine pair-correlated center-of-mass translational energy distributions. Product energy distributions and dissociation energies were determined. Following vibrational excitation of the HCl stretch fundamental of the HCl-H2O dimer, HCl fragments were detected by 2 + 1 REMPI via the f 3□2(nu' = 0) ← X 1Sigma+(nu'' = 0) and V1Sigma + (nu' = 11 and 12) ← X1Sigma+ (nu'' = 0) transitions. REMPI spectra clearly show HCl from dissociation produced in the ground vibrational state with J'' up to 11. The fragments' center-of-mass translational energy distributions were determined from images of selected rotational states of HCl and were converted to rotational state distributions of the water cofragment. All the distributions could be fit well when using a dimer dissociation energy of bond dissociation energy D0 = 1334 +/- 10 cm--1. The rotational distributions in the water cofragment pair-correlated with specific rotational states of HCl appear nonstatistical when compared to predictions of the statistical phase space theory. A detailed analysis of pair-correlated state distributions was complicated by the large number of water rotational states available, but the data show that the water rotational populations increase with decreasing translational energy. H2O fragments of this dimer were detected by 2 + 1 REMPI via the C˜1B1(000) ← X˜1A1(000) transition. REMPI clearly shows that H2O from dissociation is produced in the ground vibrational state. The fragment's center-of-mass translational energy distributions were determined from images of selected rotational states of H2O and were converted to rotational state distributions of the HCl cofragment. The distributions gave D0 = 1334 +/- 10 cm --1 and show a clear preference for rotational levels in the HCl fragment that minimize translational energy release. The usefulness of 2 + 1 REMPI detection of water fragment is discussed. The hydrogen bonding in water is dominated by pair-wise dimer interactions, and the predissociation of the water dimer following vibrational excitation is reported. The measured D0 values of (H 2O)2 and (D2O)2, 1105 and 1244 +/- 10 cm--1, respectively, are in excellent agreement with the calculated values of 1103 and 1244 +/- 5 cm--1. Pair-correlated water fragment rovibrational state distributions following vibrational predissociation of (H2O)2 and (D2O) 2 were obtained upon excitation of the hydrogen bonded OH and OD stretch fundamentals, respectively. Quasiclassical trajectory calculations, using an accurate full-dimensional potential energy surface, are in accord with and help to elucidate experiment. Experiment and theory find predominant excitation of the fragment bending mode upon hydrogen bond breaking. A minor channel is also observed in which both fragments are in the ground vibrational state and are highly rotationally excited. The theoretical calculations reveal equal probability of bending excitation in the donor and acceptor subunits, which is a result of interchange of donor and acceptor roles. The rotational distributions associated with the major channel, in which one water fragment has one quantum of bend, and the minor channel with both water fragments in the ground vibrational state are calculated, and are in agreement with experiment. (Abstract shortened by UMI.)

Representing Water Scarcity in Future Agricultural Assessments

NASA Technical Reports Server (NTRS)

Winter, Jonathan M.; Lopez, Jose R.; Ruane, Alexander C.; Young, Charles A.; Scanlon, Bridget R.; Rosenzweig, Cynthia

2017-01-01

Globally, irrigated agriculture is both essential for food production and the largest user of water. A major challenge for hydrologic and agricultural research communities is assessing the sustainability of irrigated croplands under climate variability and change. Simulations of irrigated croplands generally lack key interactions between water supply, water distribution, and agricultural water demand. In this article, we explore the critical interface between water resources and agriculture by motivating, developing, and illustrating the application of an integrated modeling framework to advance simulations of irrigated croplands. We motivate the framework by examining historical dynamics of irrigation water withdrawals in the United States and quantitatively reviewing previous modeling studies of irrigated croplands with a focus on representations of water supply, agricultural water demand, and impacts on crop yields when water demand exceeds water supply. We then describe the integrated modeling framework for simulating irrigated croplands, which links trends and scenarios with water supply, water allocation, and agricultural water demand. Finally, we provide examples of efforts that leverage the framework to improve simulations of irrigated croplands as well as identify opportunities for interventions that increase agricultural productivity, resiliency, and sustainability.

Calculation of Relative Binding Free Energy in the Water-Filled Active Site of Oligopeptide-Binding Protein A.

PubMed

Maurer, Manuela; de Beer, Stephanie B A; Oostenbrink, Chris

2016-04-15

The periplasmic oligopeptide binding protein A (OppA) represents a well-known example of water-mediated protein-ligand interactions. Here, we perform free-energy calculations for three different ligands binding to OppA, using a thermodynamic integration approach. The tripeptide ligands share a high structural similarity (all have the sequence KXK), but their experimentally-determined binding free energies differ remarkably. Thermodynamic cycles were constructed for the ligands, and simulations conducted in the bound and (freely solvated) unbound states. In the unbound state, it was observed that the difference in conformational freedom between alanine and glycine leads to a surprisingly slow convergence, despite their chemical similarity. This could be overcome by increasing the softness parameter during alchemical transformations. Discrepancies remained in the bound state however, when comparing independent simulations of the three ligands. These difficulties could be traced to a slow relaxation of the water network within the active site. Fluctuations in the number of water molecules residing in the binding cavity occur mostly on a timescale larger than the simulation time along the alchemical path. After extensive simulations, relative binding free energies that were converged to within thermal noise could be obtained, which agree well with available experimental data.

Calculation of Relative Binding Free Energy in the Water-Filled Active Site of Oligopeptide-Binding Protein A

PubMed Central

Maurer, Manuela; de Beer, Stephanie B. A.; Oostenbrink, Chris

2018-01-01

The periplasmic oligopeptide binding protein A (OppA) represents a well-known example of water-mediated protein-ligand interactions. Here, we perform free-energy calculations for three different ligands binding to OppA, using a thermodynamic integration approach. The tripeptide ligands share a high structural similarity (all have the sequence KXK), but their experimentally-determined binding free energies differ remarkably. Thermodynamic cycles were constructed for the ligands, and simulations conducted in the bound and (freely solvated) unbound states. In the unbound state, it was observed that the difference in conformational freedom between alanine and glycine leads to a surprisingly slow convergence, despite their chemical similarity. This could be overcome by increasing the softness parameter during alchemical transformations. Discrepancies remained in the bound state however, when comparing independent simulations of the three ligands. These difficulties could be traced to a slow relaxation of the water network within the active site. Fluctuations in the number of water molecules residing in the binding cavity occur mostly on a timescale larger than the simulation time along the alchemical path. After extensive simulations, relative binding free energies that were converged to within thermal noise could be obtained, which agree well with available experimental data. PMID:27092480

Groundwater-Surface Water Interactions and Downstream Transport of Water, Heat, and Solutes in a Hydropeaked River

NASA Astrophysics Data System (ADS)

Ferencz, S. B.; Cardenas, M. B.; Neilson, B. T.; Watson, J.

2017-12-01

A majority of the world's largest river systems are regulated by dams. In addition to being used for water resources management and flood prevention, many large dams are also used for hydroelectric power generation. In the United States, dams account for 7% of domestic electricity, and hydropower accounts for 16% of worldwide electricity production. To help meet electricity demand during peak usage times, hydropower utilities often increase their releases of water during high demand periods. This practice, termed hydropeaking, can cause large transient flow regimes downstream of hydroelectric dams. These transient flow increases can result in order of magnitude daily fluctuations in discharge, and the released water can have different thermal and chemical properties than ambient river water. As hydropeaking releases travel downstream, the temporary rise in stage and increase in discharge can enhance surface water-groundwater (SW-GW) exchange between the river and its alluvial aquifer. This dam-induced SW-GW exchange, combined with hydrodynamic attenuation and heat exchange processes, result in complex responses downstream. The dam-regulated Lower Colorado River downstream of Austin, TX was used as a natural laboratory to observe SW-GW interactions and downstream transport of water, heat, and solutes under hydropeaking conditions. To characterize SW-GW interactions, well transects were installed in the banks of the river to observe exchanges between the river and alluvial aquifer. The well transects were installed at three different distances from the dam (15km, 35km, and 80km). At each well transect conductivity, temperature, and pressure sensors were deployed in the monitoring wells and in the channel. Additional conductivity and temperature sensors were deployed along the study reach to provide a more detailed record of heat and solute transport during hydropeaking releases. The field data spans over two months of daily dam releases that were punctuated by two large natural storm events. To our knowledge, this study is the first to use multiple downstream field sites to characterize how dam-induced SW-GW interactions and in-stream temperature and solute transport behave under hydropeaking conditions.

Towards Plasma-Based Water Purification: Challenges and Prospects for the Future

NASA Astrophysics Data System (ADS)

Foster, John

2016-10-01

Freshwater scarcity derived from climate change, pollution, and over-development has led to serious consideration for water reuse. Advanced water treatment technologies will be required to process wastewater slated for reuse. One new and emerging technology that could potentially address the removal micropollutants in both drinking water as well as wastewater slated for reuse is plasma-based water purification. Plasma in contact with liquid water generates reactive species that attack and ultimately mineralize organic contaminants in solution. This interaction takes place in a boundary layer centered at the plasma-liquid interface. An understanding of the physical processes taking place at this interface, though poorly understood, is key to the optimization of plasma water purifiers. High electric field conditions, large density gradients, plasma-driven chemistries, and fluid dynamic effects prevail in this multiphase region. The region is also the source function for longer-lived reactive species that ultimately treat the water. Here, we review the need for advanced water treatment methods and in the process, make the case for plasma-based methods. Additionally, we survey the basic methods of interacting plasma with liquid water (including a discussion of breakdown processes in water), the current state of understanding of the physical processes taking place at the plasma-liquid interface, and the role that these processes play in water purification. The development of diagnostics usable in this multiphase environment along modeling efforts aimed at elucidating physical processes taking place at the interface are also detailed. Key experiments that demonstrate the capability of plasma-based water treatment are also reviewed. The technical challenges to the implementation of plasma-based water reactors are also discussed. NSF CBET 1336375 and DOE DE-SC0001939.

Electronic structure and partial charge distribution of doxorubicin under different molecular environments

NASA Astrophysics Data System (ADS)

Poudel, Lokendra

Doxorubicin (trade name Adriamycin, abbreviated DOX) is a well-known an- thracyclic chemotherapeutic used in treating a variety of cancers including acute leukemia, lymphoma, multiple myeloma, and a range of stomach, lung, bladder, bone, breast, and ovarian cancers. The purpose of the present work is to study electronic structure, partial charge distribution and interaction energy of DOX under different environments. It provides a framework for better understanding of bioactivity of DOX with DNA. While in this work, we focus on DOX -- DNA interactions; the obtained knowledge could be translated to other drug -- target interactions or biomolecular interactions. The electronic structure and partial charge distribution of DOX in three dierent molecular environments: isolated, solvated, and intercalated into a DNA complex,were studied by rst principles density functional methods. It is shown that the addition of solvating water molecules to DOX and the proximity and interaction with DNA has a signicant impact on the electronic structure as well as the partial charge distribution. The calculated total partial charges for DOX in the three models are 0.0, +0.123 and -0.06 electrons for the isolated, solvated, and intercalated state, respectively. Furthermore, by using the more accurate ab initio partial charge values on every atom in the models, signicant improvement in estimating the DOX-DNA interaction energy is obtained in conjunction with the NAnoscale Molecular Dynamics (NAMD) code. The electronic structure of the DOX-DNA is further elucidated by resolving the total density of states (TDOS) into dierent functional groups of DOX, DNA, water, co-crystallized Spermine molecule, and Na ions. The surface partial charge distribution in the DOX-DNA is calculated and displayed graphically. We conclude that the presence of the solvent as well as the details of the interaction geometry matter greatly in the determination of the stability of the DOX complexion. Ab initio calculations on realistic models are an important step towards a more accurate description of biomolecular interaction and in the eventual understanding of long-range interactions in biomolecular systems.

A Compilation of Provisional Karst Geospatial Data for the Interior Low Plateaus Physiographic Region, Central United States

USGS Publications Warehouse

Taylor, Charles J.; Nelson, Hugh L.

2008-01-01

Geospatial data needed to visualize and evaluate the hydrogeologic framework and distribution of karst features in the Interior Low Plateaus physiographic region of the central United States were compiled during 2004-2007 as part of the Ground-Water Resources Program Karst Hydrology Initiative (KHI) project. Because of the potential usefulness to environmental and water-resources regulators, private consultants, academic researchers, and others, the geospatial data files created during the KHI project are being made available to the public as a provisional regional karst dataset. To enhance accessibility and visualization, the geospatial data files have been compiled as ESRI ArcReader data folders and user interactive Published Map Files (.pmf files), all of which are catalogued by the boundaries of surface watersheds using U.S. Geological Survey (USGS) eight-digit hydrologic unit codes (HUC-8s). Specific karst features included in the dataset include mapped sinkhole locations, sinking (or disappearing) streams, internally drained catchments, karst springs inventoried in the USGS National Water Information System (NWIS) database, relic stream valleys, and karst flow paths obtained from results of previously reported water-tracer tests.

Geological evidence for solid-state convection in Europa's ice shell.

PubMed

Pappalardo, R T; Head, J W; Greeley, R; Sullivan, R J; Pilcher, C; Schubert, G; Moore, W B; Carr, M H; Moore, J M; Belton, M J; Goldsby, D L

1998-01-22

The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.

Geological evidence for solid-state convection in Europa's ice shell

USGS Publications Warehouse

Pappalardo, R.T.; Head, J.W.; Greeley, R.; Sullivan, R.J.; Pilcher, C.; Schubert, G.; Moore, W.B.; Carr, M.H.; Moore, Johnnie N.; Belton, M.J.S.; Goldsby, D.L.

1998-01-01

The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.

Efficient photochemistry of coronene:water complexes

NASA Astrophysics Data System (ADS)

Noble, J. A.; Jouvet, C.; Aupetit, C.; Moudens, A.; Mascetti, J.

2017-03-01

The photochemistry of ices with polycyclic aromatic hydrocarbons (PAHs) has been extensively studied, but to date no investigation has been made of PAHs in interaction with low numbers (n< 4) of molecules of water. We performed photochemical matrix isolation studies of coronene:water complexes, probing the argon matrix with FTIR spectroscopy. We find that coronene readily reacts with water upon irradiation with a mercury vapour lamp to produce oxygenated PAH photoproducts, and we postulate a reaction mechanism via a charge transfer Rydberg state. This result suggests that oxygenated PAHs should be widely observed in regions of the ISM with sufficiently high water abundances, for example near the edges of molecular clouds where water molecules begin to form, but before icy layers are observed, that is at AV< 3. In order to explain the low derived observational abundances of oxygenated PAHs, additional destruction routes must be invoked.

Effect of Chitin Isolated from Crustaceans and Cephalopods on Denaturation of Fish Myofibrillar Protein and the State of Water during Frozen Storage

NASA Astrophysics Data System (ADS)

Yamashita, Yasumitsu; Zhang, Nong; Nozaki, Yukinori

The effect of chitin hydrolysate made from shell of crustaceans and cartilage of cephalopods on the denaturation and the state of water of lizard fish myofibrillar protein (Mf) during frozen storage at -250°C for 120 days were investigated. 5.0% chitin hydrolysate (dried matter) added Mf samples were frozen at -25°C and storage for 120 days, and the change of inactivation of Mf Ca-ATPase and the change of unfrozen water in Mf were examined during the frozen storage. The decrease of Mf Ca-ATPase during frozen storage were slow by addition of chitin hydrolysate. The amount of unfrozen water in Mf were increased by addition of chitin hydrolysate, and decreaced gradually during frozen storage. On the other hand, the amount of unfrozen water of the control were decreaced suddenly during frozen storage. Above results suggest that chitin hydrolysate has cryoprotective effect on Mf. It is guessed that the mechanism of cryoprotective effect of chitin hydrolysate may be caused by an interaction between hydration sphere of Mf and equatorial OH groups in the molecular structure of chitin hydrolysate.

Developing a tool to estimate water withdrawal and consumption in electricity generation in the United States.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, M.; Peng, J.; NE)

2011-02-24

Freshwater consumption for electricity generation is projected to increase dramatically in the next couple of decades in the United States. The increased demand is likely to further strain freshwater resources in regions where water has already become scarce. Meanwhile, the automotive industry has stepped up its research, development, and deployment efforts on electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs). Large-scale, escalated production of EVs and PHEVs nationwide would require increased electricity production, and so meeting the water demand becomes an even greater challenge. The goal of this study is to provide a baseline assessment of freshwater use inmore » electricity generation in the United States and at the state level. Freshwater withdrawal and consumption requirements for power generated from fossil, nonfossil, and renewable sources via various technologies and by use of different cooling systems are examined. A data inventory has been developed that compiles data from government statistics, reports, and literature issued by major research institutes. A spreadsheet-based model has been developed to conduct the estimates by means of a transparent and interactive process. The model further allows us to project future water withdrawal and consumption in electricity production under the forecasted increases in demand. This tool is intended to provide decision makers with the means to make a quick comparison among various fuel, technology, and cooling system options. The model output can be used to address water resource sustainability when considering new projects or expansion of existing plants.« less

The interaction with gold suppresses fiber-like conformations of the amyloid β (16-22) peptide

NASA Astrophysics Data System (ADS)

Bellucci, Luca; Ardèvol, Albert; Parrinello, Michele; Lutz, Helmut; Lu, Hao; Weidner, Tobias; Corni, Stefano

2016-04-01

Inorganic surfaces and nanoparticles can accelerate or inhibit the fibrillation process of proteins and peptides, including the biomedically relevant amyloid β peptide. However, the microscopic mechanisms that determine such an effect are still poorly understood. By means of large-scale, state-of-the-art enhanced sampling molecular dynamics simulations, here we identify an interaction mechanism between the segments 16-22 of the amyloid β peptide, known to be fibrillogenic by itself, and the Au(111) surface in water that leads to the suppression of fiber-like conformations from the peptide conformational ensemble. Moreover, thanks to advanced simulation analysis techniques, we characterize the conformational selection vs. induced fit nature of the gold effect. Our results disclose an inhibition mechanism that is rooted in the details of the microscopic peptide-surface interaction rather than in general phenomena such as peptide sequestration from the solution.Inorganic surfaces and nanoparticles can accelerate or inhibit the fibrillation process of proteins and peptides, including the biomedically relevant amyloid β peptide. However, the microscopic mechanisms that determine such an effect are still poorly understood. By means of large-scale, state-of-the-art enhanced sampling molecular dynamics simulations, here we identify an interaction mechanism between the segments 16-22 of the amyloid β peptide, known to be fibrillogenic by itself, and the Au(111) surface in water that leads to the suppression of fiber-like conformations from the peptide conformational ensemble. Moreover, thanks to advanced simulation analysis techniques, we characterize the conformational selection vs. induced fit nature of the gold effect. Our results disclose an inhibition mechanism that is rooted in the details of the microscopic peptide-surface interaction rather than in general phenomena such as peptide sequestration from the solution. Electronic supplementary information (ESI) available: Representative structures for the most populated conformational structures of Aβ16-22 on bulk and on the metal surface. Normalized distribution of the variable s defined as the sum of internal dihedral angles of the peptide in solution and at the gold/water interface. See DOI: 10.1039/C6NR01539E

In-pipe water quality monitoring in water supply systems under steady and unsteady state flow conditions: a quantitative assessment.

PubMed

Aisopou, Angeliki; Stoianov, Ivan; Graham, Nigel J D

2012-01-01

Monitoring the quality of drinking water from the treatment plant to the consumers tap is critical to ensure compliance with national standards and/or WHO guideline levels. There are a number of processes and factors affecting the water quality during transmission and distribution which are little understood. A significant obstacle for gaining a detailed knowledge of various physical and chemical processes and the effect of the hydraulic conditions on the water quality deterioration within water supply systems is the lack of reliable and low-cost (both capital and O & M) water quality sensors for continuous monitoring. This paper has two objectives. The first one is to present a detailed evaluation of the performance of a novel in-pipe multi-parameter sensor probe for reagent- and membrane-free continuous water quality monitoring in water supply systems. The second objective is to describe the results from experimental research which was conducted to acquire continuous water quality and high-frequency hydraulic data for the quantitative assessment of the water quality changes occurring under steady and unsteady-state flow conditions. The laboratory and field evaluation of the multi-parameter sensor probe showed that the sensors have a rapid dynamic response, average repeatability and unreliable accuracy. The uncertainties in the sensor data present significant challenges for the analysis and interpretation of the acquired data and their use for water quality modelling, decision support and control in operational systems. Notwithstanding these uncertainties, the unique data sets acquired from transmission and distribution systems demonstrated the deleterious effect of unsteady state flow conditions on various water quality parameters. These studies demonstrate: (i) the significant impact of the unsteady-state hydraulic conditions on the disinfectant residual, turbidity and colour caused by the re-suspension of sediments, scouring of biofilms and tubercles from the pipe and increased mixing, and the need for further experimental research to investigate these interactions; (ii) important advances in sensor technologies which provide unique opportunities to study both the dynamic hydraulic conditions and water quality changes in operational systems. The research in these two areas is critical to better understand and manage the water quality deterioration in ageing water transmission and distribution systems. Copyright © 2011 Elsevier Ltd. All rights reserved.

Choices Matter, but How Do We Model Them?

NASA Astrophysics Data System (ADS)

Brelsford, C.; Dumas, M.

2017-12-01

Quantifying interactions between social systems and the physical environment we live within has long been a major scientific challenge. Humans have had such a large influence on our environment that it is no longer reasonable to consider the behavior of an ecological or hydrological system from a purely `physical' perspective: imagining a system that excludes the influence of human choices and behavior. Understanding the role that human social choices play in the energy water nexus is crucial for developing accurate models in that space. The relatively new field of socio-hydrology is making progress towards understanding the role humans play in hydrological systems. While this fact is now widely recognized across the many academic fields that study water systems, we have yet to develop a coherent set of theories for how to model the behavior of these complex and highly interdependent socio-hydrological systems. How should we conceptualize hydrological systems as socio-ecological systems (i.e. system with variables, states, parameters, actors who can control certain variables and a sense of the desirability of states) within which the rigorous study of feedbacks becomes possible? This talk reviews the state of knowledge of how social decisions around water consumption, allocation, and transport influence and are influenced by the physical hydrology that water also moves within. We cover recent papers in socio-hydrology, engineering, water law, and institutional analysis. There have been several calls within socio-hydrology to model human social behavior endogenously along with the hydrology. These improvements are needed across a range of spatial and temporal scales. We suggest two potential strategies for coupled models that allow endogenous water consumption behavior: a social first model which looks for empirical relationships between water consumption and allocation choices and the hydrological state, and a hydrology first model in which we look for regularities in how water regimes influence behavior, regional economies, or allocation institutions.

SELMA mission: revealing the origin of lunar water

NASA Astrophysics Data System (ADS)

Barabash, Stas; Selma Team

2013-04-01

We propose a very low cost lunar mission to cover a poorly investigated inter-disciplinary area in the lunar science. The mission SELMA (Surface, Environment, and Lunar Magnetic Anomalies) investigates the interaction of the neutral and plasma environment with the lunar surface and the impact of this interaction on the surface composition, in the first hand, on the presence of water. The mission focuses on the fundamental question: What is the origin of the water in the lunar soil? The mission also addresses the questions: What are the lunar exosphere content and composition and how does the exosphere interact with the surface? How do the lunar magnetic anomalies interact with the solar wind and affect the surface? SELMA investigates the origin of the water in the lunar soil via simultaneous measurements of the OH/H2O abundance in the soil, the proton flux deposited to the surface, and transient changes in the exospheric gas content and composition. The water content in the surface is mapped via measurements of the 2700 - 3300 nm OH/H2O/ice absorption lines. The proton flux at the surface is measured remotely via backscattered hydrogen flux (energetic neutral atoms, ENAs). The exospheric gas content and composition and possible transient changes due to micrometeoroid influx or outgassing are monitored by a neutral gas mass spectrometer. Little is known about the tenuous lunar exosphere, its composition, structure, and relation to the plasma environment. The reasons for the present poor knowledge of the lunar exosphere is the difficulty of observations due to the low number densities, and the complexity of models due to the multiplicity of the mechanisms responsible for the input and loss of exospheric species. To investigate the lunar exosphere SELMA is equipped with state-of-the-art time-of-flight neutral gas mass spectrometer with unprecedented sensitivity and mass resolution. The Moon does not have a global magnetic field but possesses local magnetizations. The magnetizations interact with the solar wind plasma creating highly variable mini-magnetospheres affecting, through an as yet unknown mechanism, the surface visible albedo. The electrodynamical interaction is very complex being one of the fundamental solar wind interactions in the solar system. SELMA studies how the magnetic anomaly interact with the solar wind and surface via simultaneous measurements of 3D ion and electron distribution functions, the local magnetic field, solar wind flux variations on the surface through ENA imaging of the backscattered hydrogen flux, imaging in the visible range, and measuring the surface IR spectrum. The SELMA results will be of critical importance for the interpretation of data from Mercury to be collected by the ESA BepiColombo mission in 2020 - 2022. To address its scientific objectives SELMA carries a highly focused suite of instruments including an IR spectrometer, an ENA telescope, an ion and electron spectrometer, a neutral gas mass spectrometer, a magnetometer, and a visible camera. SELMA is a spinning platform to be inserted on a low maintenance quasi-frozen polar orbit of 30 km x 216 km by a dedicated launch and a solid state fuel kick stage. SELMA was proposed to ESA as a candidate for the S-class mission.

Sequential water molecule binding enthalpies for aqueous nanodrops containing a mono-, di- or trivalent ion and between 20 and 500 water molecules† †Electronic supplementary information (ESI) available: Detailed description of the experimental and computational modeling methods. Isolation, BIRD and UVPD sequence for [Ru(NH3)6]3+·(H2O)169–171, nanoESI spectra for 2+ and 3+ ions. Detailed description of the isotope distribution simulation program. Comparison between experimental and simulated 1+, 2+ and 3+ ion isotope distributions. Wavelength dependence of the deduced sequential binding enthalpies. Comparison of experimental UVPD binding enthalpies to the liquid drop model at different temperatures. Complete list of binding enthalpies and average number of water molecules lost upon UVPD. See DOI: 10.1039/c6sc04957e Click here for additional data file.

PubMed Central

Heiles, Sven; Cooper, Richard J.; DiTucci, Matthew J.

2017-01-01

Sequential water molecule binding enthalpies, ΔH n,n–1, are important for a detailed understanding of competitive interactions between ions, water and solute molecules, and how these interactions affect physical properties of ion-containing nanodrops that are important in aerosol chemistry. Water molecule binding enthalpies have been measured for small clusters of many different ions, but these values for ion-containing nanodrops containing more than 20 water molecules are scarce. Here, ΔH n,n–1 values are deduced from high-precision ultraviolet photodissociation (UVPD) measurements as a function of ion identity, charge state and cluster size between 20–500 water molecules and for ions with +1, +2 and +3 charges. The ΔH n,n–1 values are obtained from the number of water molecules lost upon photoexcitation at a known wavelength, and modeling of the release of energy into the translational, rotational and vibrational motions of the products. The ΔH n,n–1 values range from 36.82 to 50.21 kJ mol–1. For clusters containing more than ∼250 water molecules, the binding enthalpies are between the bulk heat of vaporization (44.8 kJ mol–1) and the sublimation enthalpy of bulk ice (51.0 kJ mol–1). These values depend on ion charge state for clusters with fewer than 150 water molecules, but there is a negligible dependence at larger size. There is a minimum in the ΔH n,n–1 values that depends on the cluster size and ion charge state, which can be attributed to the competing effects of ion solvation and surface energy. The experimental ΔH n,n–1 values can be fit to the Thomson liquid drop model (TLDM) using bulk ice parameters. By optimizing the surface tension and temperature change of the logarithmic partial pressure for the TLDM, the experimental sequential water molecule binding enthalpies can be fit with an accuracy of ±3.3 kJ mol–1 over the entire range of cluster sizes. PMID:28451364

Dredging and disposal of fine sediments in the state of Rio de Janeiro, Brazil.

PubMed

Barbosa, M C; de Souza Soares de Almeida, M

2001-07-30

Dredging is employed quite frequently in the state of Rio de Janeiro, especially for the installation and upkeep of commercial ports and rehabilitation of the hydraulic section of silted bodies of water. Until recently, all dredged material with no economic use was destined for marine disposal or stored at the edge of the water body. Since the 1990s, however, a new approach has been adopted for dredging as a result of pressure from the environmental organisations, encouraging closer interaction in Rio de Janeiro between the local and state public authorities and the universities on issues relating to licensing of this kind of activity. The recent experiments of the Civil and Ocean Engineering Programs of COPPE-UFRJ (Federal University of Rio de Janeiro) described herein are included in this context. The state of Rio de Janeiro has three bays, several coastal lagoon systems and a number of small and medium sized rivers in or close to urban areas, with a gentle slope as they near the sea. This is, then, a region highly susceptible to silting processes of water bodies, and therefore, to maintenance and/or environmental rehabilitation. As discussed in the article, fine and almost always organic sediments prevail, which is a considerable obstacle to the end disposal and possibility of reuse.

Visualizing water

NASA Astrophysics Data System (ADS)

Baart, F.; van Gils, A.; Hagenaars, G.; Donchyts, G.; Eisemann, E.; van Velzen, J. W.

2016-12-01

A compelling visualization is captivating, beautiful and narrative. Here we show how melding the skills of computer graphics, art, statistics, and environmental modeling can be used to generate innovative, attractive and very informative visualizations. We focus on the topic of visualizing forecasts and measurements of water (water level, waves, currents, density, and salinity). For the field of computer graphics and arts, water is an important topic because it occurs in many natural scenes. For environmental modeling and statistics, water is an important topic because the water is essential for transport, a healthy environment, fruitful agriculture, and a safe environment.The different disciplines take different approaches to visualizing water. In computer graphics, one focusses on creating water as realistic looking as possible. The focus on realistic perception (versus the focus on the physical balance pursued by environmental scientists) resulted in fascinating renderings, as seen in recent games and movies. Visualization techniques for statistical results have benefited from the advancement in design and journalism, resulting in enthralling infographics. The field of environmental modeling has absorbed advances in contemporary cartography as seen in the latest interactive data-driven maps. We systematically review the design emerging types of water visualizations. The examples that we analyze range from dynamically animated forecasts, interactive paintings, infographics, modern cartography to web-based photorealistic rendering. By characterizing the intended audience, the design choices, the scales (e.g. time, space), and the explorability we provide a set of guidelines and genres. The unique contributions of the different fields show how the innovations in the current state of the art of water visualization have benefited from inter-disciplinary collaborations.

Proton transfer from water to ketyl radical anion: Assessment of critical size of hydrated cluster and free energy barrier in solution from first principles simulations

NASA Astrophysics Data System (ADS)

Biswas, Sohag; Dasgupta, Teesta; Mallik, Bhabani S.

2016-09-01

We present the reactivity of an organic intermediate by studying the proton transfer process from water to ketyl radical anion using gas phase electronic structure calculations and the metadynamics method based first principles molecular dynamics (FPMD) simulations. Our results indicate that during the micro solvation of anion by water molecules systematically, the presence of minimum three water molecules in the gas phase cluster is sufficient to observe the proton transfer event. The analysis of trajectories obtained from initial FPMD simulation of an aqueous solution of the anion does not show any evident of complete transfer of the proton from water. The cooperativity of water molecules and the relatively weak anion-water interaction in liquid state prohibit the full release of the proton. Using biasing potential through first principles metadynamics simulations, we report the observation of proton transfer reaction from water to ketyl radical anion with a barrier height of 16.0 kJ/mol.

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG).

PubMed

Pehkonen, K S; Roos, Y H; Miao, S; Ross, R P; Stanton, C

2008-06-01

The frozen and dehydrated state transitions of lactose and trehalose were determined and studied as factors affecting the stability of probiotic bacteria to understand physicochemical aspects of protection against freezing and dehydration of probiotic cultures. Lactobacillus rhamnosus GG was frozen (-22 or -43 degrees C), freeze-dried and stored under controlled water vapour pressure (0%, 11%, 23% and 33% relative vapour pressure) conditions. Lactose, trehalose and their mixture (1 : 1) were used as protective media. These systems were confirmed to exhibit relatively similar state transition and water plasticization behaviour in freeze-concentrated and dehydrated states as determined by differential scanning calorimetry. Ice formation and dehydrated materials were studied using cold-stage microscopy and scanning electron microscopy. Trehalose and lactose-trehalose gave the most effective protection of cell viability as observed from colony forming units after freezing, dehydration and storage. Enhanced cell viability was observed when the freezing temperature was -43 degrees C. State transitions of protective media affect ice formation and cell viability in freeze-drying and storage. Formation of a maximally freeze-concentrated matrix with entrapped microbial cells is essential in freezing prior to freeze-drying. Freeze-drying must retain a solid amorphous state of protectant matrices. Freeze-dried matrices contain cells entrapped in the protective matrices in the freezing process. The retention of viability during storage seems to be controlled by water plasticization of the protectant matrix and possibly interactions of water with the dehydrated cells. Highest cell viability was obtained in glassy protective media. This study shows that physicochemical properties of protective media affect the stability of dehydrated cultures. Trehalose and lactose may be used in combination, which is particularly important for the stabilization of probiotic bacteria in dairy systems.

Ultrafast photoinduced dynamics of the 3,6-diaminoacridinium derivative ATTO 465 in solution.

PubMed

Arden-Jacob, Jutta; Drexhage, Karl-Heinz; Druzhinin, Sergey I; Ekimova, Maria; Flender, Oliver; Lenzer, Thomas; Oum, Kawon; Scholz, Mirko

2013-02-14

The excited state dynamics of the dye ATTO 465, a well-known fluorescence marker for biological applications, have been characterized in various solvents including THF, ethanol, methanol, water and the highly polar protic ionic liquid 2-hydroxyethylammonium formate (2-OH-EAF) by combining results from time-correlated single-photon counting (TCSPC) and ultrafast pump-supercontinuum probe (PSCP) spectroscopy as well as steady-state absorption and fluorescence. In water, 2-OH-EAF and two fluorinated alcohols, there is a pronounced blue-shift and broadening of the S(0) → S(1) absorption band and also a larger Stokes shift than in the other solvents, indicating a particular influence of hydrogen-bonding interactions. S(1) lifetimes from TCSPC at 25 °C range from 3.3 ns to 5.6 ns. An unusual increase in the S(1) lifetime with temperature is observed for ethanol and methanol, however water behaves in the opposite way. The behavior can be tentatively explained by a solvent- and temperature-dependent "proximity effect", where coupling of the close-lying S(1) and S(2) states influences the intramolecular relaxation rate of the dye. In addition, temperature-dependent complex equilibria of ATTO 465 with solvent molecules may influence the measured lifetimes. Several excited-state absorption (ESA) transitions are identified in the PSCP spectra, which are in good agreement with the position of the UV bands in the steady-state absorption spectra. Small shifts of the stimulated emission and ESA bands are consistent with solvation dynamics in the excited electronic state. An additional ~16 ps component in water, visible over the entire spectral range, is tentatively ascribed to a fast IC channel which is accessed by a fraction of ATTO 465 molecules.

Hydraulophones: Acoustic musical instruments and expressive user interfaces

NASA Astrophysics Data System (ADS)

Janzen, Ryan E.

Fluid flow creates an expansive range of acoustic possibilities, particularly in the case of water, which has unique turbulence and vortex shedding properties as compared with the air of ordinary wind instruments. Sound from water flow is explained with reference to a new class of musical instruments, hydraulophones, in which oscillation originates directly from matter in its liquid state. Several hydraulophones which were realized in practical form are described. A unique user-interface consisting of a row of water jets is presented, in terms of its expressiveness, tactility, responsiveness to derivatives and integrals of displacement, and in terms of the direct physical interaction between a user and the physical process of sound production. Signal processing algorithms are introduced, which extract further information from turbulent water flow, for industrial applications as well as musical applications.

Determination of the Self-organized Mesoporous Materials Sorption Capacity in Water Treatment Processes Using Mössbauer Spectroscopy

NASA Astrophysics Data System (ADS)

Feklistov, D. Yu.; Filippov, V. P.; Kurchatov, I. M.; Laguntsov, N. I.

Different approaches to water purification are considered. It is shown that for developing of effective purification methods in the different water treatment technologies special knowledge is necessary. This knowledge deals with physical-chemical processes of used reagents interaction with contaminating impurities. The obtaining of the necessary data on physics-chemical processes such as the formation of chemical compounds of iron, the change in valence state of iron, adsorption and absorption pollutants are analyzed. The usage of iron compounds as a cleaners and the water treatment from the iron pollutant are the events, in which Mössbauer spectroscopy allows to determine not only the chemical changes, but also to obtain quantitative data on the reaction products and on the sizes of reaction products and their quantities.

Surface-water Interface Induces Conformational Changes Critical for Protein Adsorption: Implications for Monolayer Formation of EAS Hydrophobin

PubMed Central

Ley, Kamron; Christofferson, Andrew; Penna, Matthew; Winkler, Dave; Maclaughlin, Shane; Yarovsky, Irene

2015-01-01

The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin. PMID:26636091

Surface-water Interface Induces Conformational Changes Critical for Protein Adsorption: Implications for Monolayer Formation of EAS Hydrophobin.

PubMed

Ley, Kamron; Christofferson, Andrew; Penna, Matthew; Winkler, Dave; Maclaughlin, Shane; Yarovsky, Irene

2015-01-01

The class I hydrophobin EAS is part of a family of small, amphiphilic fungal proteins best known for their ability to self-assemble into stable monolayers that modify the hydrophobicity of a surface to facilitate further microbial growth. These proteins have attracted increasing attention for industrial and biomedical applications, with the aim of designing surfaces that have the potential to maintain their clean state by resisting non-specific protein binding. To gain a better understanding of this process, we have employed all-atom molecular dynamics to study initial stages of the spontaneous adsorption of monomeric EAS hydrophobin on fully hydroxylated silica, a commonly used industrial and biomedical substrate. Particular interest has been paid to the Cys3-Cys4 loop, which has been shown to exhibit disruptive behavior in solution, and the Cys7-Cys8 loop, which is believed to be involved in the aggregation of EAS hydrophobin at interfaces. Specific and water mediated interactions with the surface were also analyzed. We have identified two possible binding motifs, one which allows unfolding of the Cys7-Cys8 loop due to the surfactant-like behavior of the Cys3-Cys4 loop, and another which has limited unfolding due to the Cys3-Cys4 loop remaining disordered in solution. We have also identified intermittent interactions with water which mediate the protein adsorption to the surface, as well as longer lasting interactions which control the diffusion of water around the adsorption site. These results have shown that EAS behaves in a similar way at the air-water and surface-water interfaces, and have also highlighted the need for hydrophilic ligand functionalization of the silica surface in order to prevent the adsorption of EAS hydrophobin.

Shell preservation of Limacina inflata (Pteropoda) in surface sediments from the Central and South Atlantic Ocean: a new proxy to determine the aragonite saturation state of water masses

NASA Astrophysics Data System (ADS)

Gerhardt, Sabine; Henrich, Rüdiger

2001-08-01

Over 300 surface sediment samples from the Central and South Atlantic Ocean and the Caribbean Sea were investigated for the preservation state of the aragonitic test of Limacina inflata. Results are displayed in spatial distribution maps and are plotted against cross-sections of vertical water mass configurations, illustrating the relationship between preservation state, saturation state of the overlying waters, and overall water mass distribution. The microscopic investigation of L. inflata (adults) yielded the Limacina dissolution index (LDX), and revealed three regional dissolution patterns. In the western Atlantic Ocean, sedimentary preservation states correspond to saturation states in the overlying waters. Poor preservation is found within intermediate water masses of southern origin (i.e. Antarctic intermediate water (AAIW), upper circumpolar water (UCDW)), which are distinctly aragonite-corrosive, whereas good preservation is observed within the surface waters above and within the upper North Atlantic deep water (UNADW) beneath the AAIW. In the eastern Atlantic Ocean, in particular along the African continental margin, the LDX fails in most cases (i.e. less than 10 tests of L. inflata per sample were found). This is most probably due to extensive "metabolic" aragonite dissolution at the sediment-water interface combined with a reduced abundance of L. inflata in the surface waters. In the Caribbean Sea, a more complex preservation pattern is observed because of the interaction between different water masses, which invade the Caribbean basins through several channels, and varying input of bank-derived fine aragonite and magnesian calcite material. The solubility of aragonite increases with increasing pressure, but aragonite dissolution in the sediments does not simply increase with water depth. Worse preservation is found in intermediate water depths following an S-shaped curve. As a result, two aragonite lysoclines are observed, one above the other. In four depth transects, we show that the western Atlantic and Caribbean LDX records resemble surficial calcium carbonate data and δ13C and carbonate ion concentration profiles in the water column. Moreover, preservation of L. inflata within AAIW and UCDW improves significantly to the north, whereas carbonate corrosiveness diminishes due to increased mixing of AAIW and UNADW. The close relationship between LDX values and aragonite contents in the sediments shows much promise for the quantification of the aragonite loss under the influence of different water masses. LDX failure and uncertainties may be attributed to (1) aragonite dissolution due to bottom water corrosiveness, (2) aragonite dissolution due to additional CO 2 release into the bottom water by the degradation of organic matter based on an enhanced supply of organic matter into the sediment, (3) variations in the distribution of L. inflata and hence a lack of supply into the sediment, (4) dilution of the sediments and hence a lack of tests of L. inflata, or (5) redeposition of sediment particles.

Fluorescent Phthalocyanine Assembly Distinguishes Chiral Isomers of Different Types of Amino Acids and Sugars.

PubMed

Jiang, Yuying; Liu, Chenxi; Wang, Xiqian; Wang, Tianyu; Jiang, Jianzhuang

2017-07-25

The functions of some natural supramolecular architectures, such as ribosomes, are dependent on the recognition of different types of chiral biomolecules. However, the recognition of different types of chiral molecules (multiobject chiral recognition), such as amino acids and sugars, by independent and identically artificial supramolecular assembly, was rarely achieved. In this article, simple amphiphilic achiral phthalocyanine was found to form supramolecular chiral assemblies with charged water-soluble polymers upon host-guest interactions at the air/water interface. Among these systems, one identical phthalocyanine/poly(l-lysine) assembly not only can distinguish enantiomers of different amino acids but also can recognize several epimers of monose. The chiral recognitions were achieved by comparing either the steady-state fluorescence intensity or fluorescence quenching rate of phthalocyanine/poly(l-lysine) assemblies, before and after interaction with different small chiral molecules. It was demonstrated that the interactions between poly(l-lysine) and different small chiral molecules could change the aggregation of phthalocyanines. And the sensitivity of fluorescence and the excellent multiobject chiral recognition properties of the phthalocyanine/poly(l-lysine) assembly are dependent on the subtle molecular packing mode and the cooperation of different noncovalent interactions.

Antagonistic Microbial Interactions: Contributions and Potential Applications for Controlling Pathogens in the Aquatic Systems

PubMed Central

Feichtmayer, Judith; Deng, Li; Griebler, Christian

2017-01-01

Despite the active and intense treatment of wastewater, pathogenic microorganisms and viruses are frequently introduced into the aquatic environment. For most human pathogens, however, this is a rather hostile place, where starvation, continuous inactivation, and decay generally occur, rather than successful reproduction. Nevertheless, a great diversity of the pathogenic microorganisms can be detected, in particular, in the surface waters receiving wastewater. Pathogen survival depends majorly on abiotic factors such as irradiation, changes in water ionic strength, temperature, and redox state. In addition, inactivation is enhanced by the biotic interactions in the environment. Although knowledge of the antagonistic biotic interactions has been available since a long time, certain underlying processes and mechanisms still remain unclear. Others are well-appreciated and increasingly are applied to the present research. Our review compiles and discusses the presently known biotic interactions between autochthonous microbes and pathogens introduced into the aquatic environment, including protozoan grazing, virus-induced bacterial cell lysis, antimicrobial substances, and predatory bacteria. An overview is provided on the present knowledge, as well as on the obvious research gaps. Individual processes that appear promising for future applications in the aquatic environment are presented and discussed. PMID:29184541

Theoretical investigation of gas-phase molecular complex formation between 2-hydroxy thiophenol and a water molecule.

PubMed

Kumar Deb, Debojit; Sarkar, Biplab

2017-01-18

The torsional potential of OH and SH rotations in 2-hydroxy thiophenol is systematically studied using the MP2 ab initio method. The outcome of state-of-the-art calculations is used in the investigation of the structures and conformational preferences of 2-hydroxy thiophenol and aims at further interaction studies with a gas phase water molecule. SCS-MP2 and CCSD(T) complete basis set (CBS) limit interaction energies for these complexes are presented. The SCS-MP2/CBS limit is achieved using various two-point extrapolation methods with aug-cc-pVDZ and aug-cc-pVTZ basis sets. The CCSD(T) correction term is determined as the difference between CCSD(T) and SCS-MP2 interaction energies calculated using a smaller basis set. The effect of counterpoise correction on the extrapolation to the CBS limit is discussed. The performance of DFT based wB97XD, M06-2X and B3LYP-D3 functionals is tested against the benchmark energy from ab initio calculations. Hydrogen bond interactions are characterized by carrying out QTAIM, NCIPLOT, NBO and SAPT analyses.

Study of water dynamics in the soaking, steaming, and solid-state fermentation of glutinous rice by LF-NMR: a novel monitoring approach.

PubMed

Li, Teng; Tu, Chuanhai; Rui, Xin; Gao, Yangwen; Li, Wei; Wang, Kun; Xiao, Yu; Dong, Mingsheng

2015-04-01

Solid-state fermentation (SSF) of starchy grain is a traditional technique for food and alcoholic beverage production in East Asia. In the present study, low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of water dynamics and microstructure alternations during the soaking, steaming, and SSF of glutinous rice as a rapid real-time monitoring method. Three different proton fractions with different mobilities were identified based on the degree of interaction between biopolymers and water. Soaking and steaming significantly changed the proton distribution of the sample. The different phases of SSF were reflected by the T2 parameters. In addition, the variations in the T2 parameters were explained by the microstructure changes of rice induced by SSF. The fermentation time and T2 parameters were sigmoidally correlated. Thus, LF-NMR may be an effective real-time monitoring method for SSF in starch systems.

Spatial pattern analysis of cruise ship-humpback whale interactions in and near Glacier Bay National Park, Alaska.

PubMed

Harris, Karin; Gende, Scott M; Logsdon, Miles G; Klinger, Terrie

2012-01-01

Understanding interactions between large ships and large whales is important to estimate risks posed to whales by ships. The coastal waters of Alaska are a summer feeding area for humpback whales (Megaptera novaeangliae) as well as a prominent destination for large cruise ships. Lethal collisions between cruise ships and humpback whales have occurred throughout Alaska, including in Glacier Bay National Park (GBNP). Although the National Park Service (NPS) establishes quotas and operating requirements for cruise ships within GBNP in part to minimize ship-whale collisions, no study has quantified ship-whale interactions in the park or in state waters where ship traffic is unregulated. In 2008 and 2009, an observer was placed on ships during 49 different cruises that included entry into GBNP to record distance and bearing of whales that surfaced within 1 km of the ship's bow. A relative coordinate system was developed in ArcGIS to model the frequency of whale surface events using kernel density. A total of 514 whale surface events were recorded. Although ship-whale interactions were common within GBNP, whales frequently surfaced in front of the bow in waters immediately adjacent to the park (west Icy Strait) where cruise ship traffic is not regulated by the NPS. When ships transited at speeds >13 knots, whales frequently surfaced closer to the ship's midline and ship's bow in contrast to speeds slower than 13 knots. Our findings confirm that ship speed is an effective mitigation measure for protecting whales and should be applied to other areas where ship-whale interactions are common.

Spatial Pattern Analysis of Cruise Ship-Humpback Whale Interactions in and Near Glacier Bay National Park, Alaska

NASA Astrophysics Data System (ADS)

Harris, Karin; Gende, Scott M.; Logsdon, Miles G.; Klinger, Terrie

2012-01-01

Understanding interactions between large ships and large whales is important to estimate risks posed to whales by ships. The coastal waters of Alaska are a summer feeding area for humpback whales ( Megaptera novaeangliae) as well as a prominent destination for large cruise ships. Lethal collisions between cruise ships and humpback whales have occurred throughout Alaska, including in Glacier Bay National Park (GBNP). Although the National Park Service (NPS) establishes quotas and operating requirements for cruise ships within GBNP in part to minimize ship-whale collisions, no study has quantified ship-whale interactions in the park or in state waters where ship traffic is unregulated. In 2008 and 2009, an observer was placed on ships during 49 different cruises that included entry into GBNP to record distance and bearing of whales that surfaced within 1 km of the ship's bow. A relative coordinate system was developed in ArcGIS to model the frequency of whale surface events using kernel density. A total of 514 whale surface events were recorded. Although ship-whale interactions were common within GBNP, whales frequently surfaced in front of the bow in waters immediately adjacent to the park (west Icy Strait) where cruise ship traffic is not regulated by the NPS. When ships transited at speeds >13 knots, whales frequently surfaced closer to the ship's midline and ship's bow in contrast to speeds slower than 13 knots. Our findings confirm that ship speed is an effective mitigation measure for protecting whales and should be applied to other areas where ship-whale interactions are common.

Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

PubMed Central

Hoffmann, Herbert C.; Debowski, Marta; Müller, Philipp; Paasch, Silvia; Senkovska, Irena; Kaskel, Stefan; Brunner, Eike

2012-01-01

Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field.

Colorado State University Center for Geosciences/Atmospheric Research (CG/AR)

DTIC Science & Technology

2013-02-01

Precipitable Water observations and to extract uncertainty estimates. Gave a video teleconference presentation titled “Global Precipitation Products...of Atmospheric Chemistry and Physics (An Interactive Open Access Journal of the European Geosciences Union), following revisions in response to...Army Research Laboratory in Adelphi, Maryland on Tuesday, August 2. Dr. Stanley Kidder gave a video teleconference presentation titled “Global

Improving aerosol interaction with clouds and precipitation in a regional chemical weather modeling system

NASA Astrophysics Data System (ADS)

Zhou, C.; Zhang, X.; Gong, S.

2015-12-01

A comprehensive aerosol-cloud-precipitation interaction (ACI) scheme has been developed under CMA chemical weather modeling system GRAPES/CUACE. Calculated by a sectional aerosol activation scheme based on the information of size and mass from CUACE and the thermal-dynamic and humid states from the weather model GRAPES at each time step, the cloud condensation nuclei (CCN) is fed online interactively into a two-moment cloud scheme (WDM6) and a convective parameterization to drive the cloud physics and precipitation formation processes. The modeling system has been applied to study the ACI for January 2013 when several persistent haze-fog events and eight precipitation events occurred. The results show that interactive aerosols with the WDM6 in GRAPES/CUACE obviously increase the total cloud water, liquid water content and cloud droplet number concentrations while decrease the mean diameter of cloud droplets with varying magnitudes of the changes in each case and region. These interactive micro-physical properties of clouds improve the calculation of their collection growth rates in some regions and hence the precipitation rate and distributions in the model, showing 24% to 48% enhancements of TS scoring for 6-h precipitation in almost all regions. The interactive aerosols with the WDM6 also reduce the regional mean bias of temperature by 3 °C during certain precipitation events, but the monthly means bias is only reduced by about 0.3°C.

Idealized Cloud-System Resolving Modeling for Tropical Convection Studies

NASA Astrophysics Data System (ADS)

Anber, Usama M.

A three-dimensional limited-domain Cloud-Resolving Model (CRM) is used in idealized settings to study the interaction between tropical convection and the large scale dynamics. The model domain is doubly periodic and the large-scale circulation is parameterized using the Weak Temperature Gradient (WTG) Approximation and Damped Gravity Wave (DGW) methods. The model simulations fall into two main categories: simulations with a prescribed radiative cooling profile, and others in which radiative cooling profile interacts with clouds and water vapor. For experiments with a prescribed radiative cooling profile, radiative heating is taken constant in the vertical in the troposphere. First, the effect of turbulent surface fluxes and radiative cooling on tropical deep convection is studied. In the precipitating equilibria, an increment in surface fluxes produces a greater increase in precipitation than an equal increment in column-integrated radiative heating. The gross moist stability remains close to constant over a wide range of forcings. With dry initial conditions, the system exhibits hysteresis, and maintains a dry state with for a wide range of net energy inputs to the atmospheric column under WTG. However, for the same forcings the system admits a rainy state when initialized with moist conditions, and thus multiple equilibria exist under WTG. When the net forcing is increased enough that simulations, which begin dry, eventually develop precipitation. DGW, on the other hand, does not have the tendency to develop multiple equilibria under the same conditions. The effect of vertical wind shear on tropical deep convection is also studied. The strength and depth of the shear layer are varied as control parameters. Surface fluxes are prescribed. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This non-monotonic dependence of rainfall on shear is observed when the imposed surface fluxes are moderate. For larger surface fluxes, convection in the unsheared basic state is already strongly organized, but increasing wind shear still leads to increasing rainfall. In addition to surface rainfall, the impacts of shear on the parameterized large-scale vertical velocity, convective mass fluxes, cloud fraction, and momentum transport are also discussed. For experiments with interactive radiative cooling profile, the effect of cloud-radiation interaction on cumulus ensemble is examined in sheared and unsheared environments with both fixed and interactive sea surface temperature (SST). For fixed SST, interactive radiation, when compared to simulations in which radiative profile has the same magnitude and vertical shape but does not interact with clouds or water vapor, is found to suppress mean precipitation by inducing strong descent in the lower troposphere, increasing the gross moist stability. For interactive SST, using a slab ocean mixed layer, there exists a shear strength above which the system becomes unstable and develops oscillatory behavior. Oscillations have periods of wet precipitating states followed by periods of dry non-precipitating states. The frequencies of oscillations are intraseasonal to subseasonal, depending on the mixed layer depth. Finally, the model is coupled to a land surface model with fully interactive radiation and surface fluxes to study the diurnal and seasonal radiation and water cycles in the Amazon basin. The model successfully captures the afternoon precipitation and cloud cover peak and the greater latent heat flux in the dry season for the first time; two major biases in GCMs with implications for correct estimates of evaporation and gross primary production in the Amazon. One of the key findings is that the fog layer near the surface in the west season is crucial for determining the surface energy budget and precipitation. This suggests that features on the diurnal time scale can significantly impact climate on the seasonal time scale.

A Finite-Volume approach for compressible single- and two-phase flows in flexible pipelines with fluid-structure interaction

NASA Astrophysics Data System (ADS)

Daude, F.; Galon, P.

2018-06-01

A Finite-Volume scheme for the numerical computations of compressible single- and two-phase flows in flexible pipelines is proposed based on an approximate Godunov-type approach. The spatial discretization is here obtained using the HLLC scheme. In addition, the numerical treatment of abrupt changes in area and network including several pipelines connected at junctions is also considered. The proposed approach is based on the integral form of the governing equations making it possible to tackle general equations of state. A coupled approach for the resolution of fluid-structure interaction of compressible fluid flowing in flexible pipes is considered. The structural problem is solved using Euler-Bernoulli beam finite elements. The present Finite-Volume method is applied to ideal gas and two-phase steam-water based on the Homogeneous Equilibrium Model (HEM) in conjunction with a tabulated equation of state in order to demonstrate its ability to tackle general equations of state. The extensive application of the scheme for both shock tube and other transient flow problems demonstrates its capability to resolve such problems accurately and robustly. Finally, the proposed 1-D fluid-structure interaction model appears to be computationally efficient.

Dynamic Mechanism of a Fluorinated Oxime Reactivator Unbinding from AChE Gorge in Polarizable Water.

PubMed

Pathak, Arup K; Bandyopadhyay, Tusar

2018-04-12

A well-tempered metadynamics simulation is performed to study the unbinding process of a fluorinated oxime (FHI-6) drug from the active-site gorge of acetylcholinesterase enzyme in a polarizable water medium. Cation-π interactions and water bridge and hydrogen bridge formations between the protein and the drug molecule are found to strongly influence the unbinding process, forming basins and barriers along the gorge pathway. Distinct unbinding pathways are found when FHI-6 was compared with its recently reported nonfluorinated analogue, HI-6. For example, because of permanent positive charges on both the pyridinium rings of HI-6, it exhibits the minimum in the potential of mean force of the unbinding process in the gorge mouth (where the peripheral anion site, PAS, of the enzyme is located), which is largely caused by cation-π interactions. However, the same interaction, both in the catalytic active-site (CAS) and PAS regions, is found to be greatly enhanced in its lipophilic fluorinated analogue, FHI-6, causing a deep potential energy minimum in the bound state. This may render FHI-6 to be held more firmly in the CAS region of the gorge, as is also evidenced from the microkinetics of unbinding transitions, measured through a combination of metadynamics and hyperdynamics simulations.

Probing the Role of Active Site Water in the Sesquiterpene Cyclization Reaction Catalyzed by Aristolochene Synthase.

PubMed

Chen, Mengbin; Chou, Wayne K W; Al-Lami, Naeemah; Faraldos, Juan A; Allemann, Rudolf K; Cane, David E; Christianson, David W

2016-05-24

Aristolochene synthase (ATAS) is a high-fidelity terpenoid cyclase that converts farnesyl diphosphate exclusively into the bicyclic hydrocarbon aristolochene. Previously determined crystal structures of ATAS complexes revealed trapped active site water molecules that could potentially interact with catalytic intermediates: water "w" hydrogen bonds with S303 and N299, water molecules "w1" and "w2" hydrogen bond with Q151, and a fourth water molecule coordinates to the Mg(2+)C ion. There is no obvious role for water in the ATAS mechanism because the enzyme exclusively generates a hydrocarbon product. Thus, these water molecules are tightly controlled so that they cannot react with carbocation intermediates. Steady-state kinetics and product distribution analyses of eight ATAS mutants designed to perturb interactions with active site water molecules (S303A, S303H, S303D, N299A, N299L, N299A/S303A, Q151H, and Q151E) indicate relatively modest effects on catalysis but significant effects on sesquiterpene product distributions. X-ray crystal structures of S303A, N299A, N299A/S303A, and Q151H mutants reveal minimal perturbation of active site solvent structure. Seven of the eight mutants generate farnesol and nerolidol, possibly resulting from addition of the Mg(2+)C-bound water molecule to the initially formed farnesyl cation, but no products are generated that would suggest enhanced reactivity of other active site water molecules. However, intermediate germacrene A tends to accumulate in these mutants. Thus, apart from the possible reactivity of Mg(2+)C-bound water, active site water molecules in ATAS are not directly involved in the chemistry of catalysis but instead contribute to the template that governs the conformation of the flexible substrate and carbocation intermediates.

Simulated water budgets and ground-water/surface-water interactions in Bushkill and parts of Monocacy Creek watersheds, Northampton County, Pennsylvania: A preliminary study with identification of data needs

USGS Publications Warehouse

Risser, Dennis W.

2006-01-01

This report, prepared in cooperation with the Department of Environmental Protection, Office of Mineral Resources Management, provides a preliminary analysis of water budgets and generalized ground-water/surface-water interactions for Bushkill and parts of Monocacy Creek watersheds in Northampton County, Pa., by use of a ground-water flow model. Bushkill Creek watershed was selected for study because it has areas of rapid growth, ground-water withdrawals from a quarry, and proposed stream-channel modifications, all of which have the potential for altering ground-water budgets and the interaction between ground water and streams. Preliminary 2-dimensional, steady-state simulations of ground-water flow by the use of MODFLOW are presented to show the status of work through September 2005 and help guide ongoing data collection in Bushkill Creek watershed. Simulations were conducted for (1) predevelopment conditions, (2) a water table lowered for quarry operations, and (3) anthropogenic changes in hydraulic conductivity of the streambed and aquifer. Preliminary results indicated under predevelopment conditions, the divide between the Bushkill and Monocacy Creek ground-water basins may not have been coincident with the topographic divide and as much as 14 percent of the ground-water discharge to Bushkill Creek may have originated from recharge in the Monocacy Creek watershed. For simulated predevelopment conditions, Schoeneck Creek and parts of Monocacy Creek were dry, but Bushkill Creek was gaining throughout all reaches. Simulated lowering of the deepest quarry sump to an altitude of 147 feet for quarry operations caused ground-water recharge and streamflow leakage to be diverted to the quarry throughout about 14 square miles and caused reaches of Bushkill and Little Bushkill Creeks to change from gaining to losing streams. Lowering the deepest quarry sump to an altitude of 100 feet caused simulated ground-water discharge to the quarry to increase about 4 cubic feet per second. Raising the deepest sump to an altitude of 200 feet caused the simulated discharge to the quarry to decrease about 14 cubic feet per second.Decreasing the hydraulic conductivity of the streambed of Bushkill Creek in the reach of large losses of flow caused simulated ground-water levels to decline and ground-water discharge to a quarry to decrease from 74 to 45 cubic feet per second.Decreasing the hydraulic conductivity of a hypothesized highly transmissive zone with a plug of relatively impermeable material caused ground-water levels to increase east of the plug and decline west of the plug, and decreased the discharge to a quarry from 74 to 53 cubic feet per second. Preliminary results of the study have significant limitations, which need to be recognized by the user. The results demonstrated the usefulness of ground-water modeling with available data sets, but as more data become available through field studies, a more complete evaluation could be conducted of the preliminary assumptions in the conceptual model, model sensitivity, and effects of boundary conditions. Additional streamflow and ground-water-level measurements would be needed to better quantify recharge and aquifer properties, particularly the anisotropy of carbonate rocks. Measurements of streamflow losses at average, steady-state hydrologic conditions could provide a more accurate estimate of ground-water recharge from this source, which directly affects water budgets and contributing areas simulated by the model.

Cooperative effects in the structuring of fluoride water clusters: Ab initio hybrid quantum mechanical/molecular mechanical model incorporating polarizable fluctuating charge solvent

NASA Astrophysics Data System (ADS)

Bryce, Richard A.; Vincent, Mark A.; Malcolm, Nathaniel O. J.; Hillier, Ian H.; Burton, Neil A.

1998-08-01

A new hybrid quantum mechanical/molecular mechanical model of solvation is developed and used to describe the structure and dynamics of small fluoride/water clusters, using an ab initio wave function to model the ion and a fluctuating charge potential to model the waters. Appropriate parameters for the water-water and fluoride-water interactions are derived, with the fluoride anion being described by density functional theory and a large Gaussian basis. The role of solvent polarization in determining the structure and energetics of F(H2O)4- clusters is investigated, predicting a slightly greater stability of the interior compared to the surface structure, in agreement with ab initio studies. An extended Lagrangian treatment of the polarizable water, in which the water atomic charges fluctuate dynamically, is used to study the dynamics of F(H2O)4- cluster. A simulation using a fixed solvent charge distribution indicates principally interior, solvated states for the cluster. However, a preponderance of trisolvated configurations is observed using the polarizable model at 300 K, which involves only three direct fluoride-water hydrogen bonds. Ab initio calculations confirm this trisolvated species as a thermally accessible state at room temperature, in addition to the tetrasolvated interior and surface structures. Extension of this polarizable water model to fluoride clusters with five and six waters gave less satisfactory agreement with experimental energies and with ab initio geometries. However, our results do suggest that a quantitative model of solvent polarization is fundamental for an accurate understanding of the properties of anionic water clusters.

An agent-based hydroeconomic model to evaluate water policies in Jordan

NASA Astrophysics Data System (ADS)

Yoon, J.; Gorelick, S.

2014-12-01

Modern water systems can be characterized by a complex network of institutional and private actors that represent competing sectors and interests. Identifying solutions to enhance water security in such systems calls for analysis that can adequately account for this level of complexity and interaction. Our work focuses on the development of a hierarchical, multi-agent, hydroeconomic model that attempts to realistically represent complex interactions between hydrologic and multi-faceted human systems. The model is applied to Jordan, one of the most water-poor countries in the world. In recent years, the water crisis in Jordan has escalated due to an ongoing drought and influx of refugees from regional conflicts. We adopt a modular approach in which biophysical modules simulate natural and engineering phenomena, and human modules represent behavior at multiple scales of decision making. The human modules employ agent-based modeling, in which agents act as autonomous decision makers at the transboundary, state, organizational, and user levels. A systematic nomenclature and conceptual framework is used to characterize model agents and modules. Concepts from the Unified Modeling Language (UML) are adopted to promote clear conceptualization of model classes and process sequencing, establishing a foundation for full deployment of the integrated model in a scalable object-oriented programming environment. Although the framework is applied to the Jordanian water context, it is generalizable to other regional human-natural freshwater supply systems.

Conceptual design for the National Water Information System

USGS Publications Warehouse

Edwards, Melvin D.; Putnam, Arthur L.; Hutchison, Norman E.

1986-01-01

The Water Resources Division of the U.S. Geological Survey began the design and development of a National Water Information System (NWIS) in 1983. The NWIS will replace and integrate the existing data systems of the National Water Data Storage and Retrieval System, National Water Data Exchange, National Water-Use Information Program, and Water Resources Scientific Information Center. The NWIS has been designed as an interactive, distributed data system. The software system has been designed in a modular manner which integrates existing software functions and allows multiple use of software modules. The data base has been designed as a relational data model that allows integrated storage of the existing water data, water-use data, and water-data indexing information by using a common relational data base management system. The NWIS will be operated on microcomputers located in each of the Water Resources Division's District offices and many of its State, subdistrict, and field offices. The microcomputers will be linked together through a national telecommunication network maintained by the U. S. Geological Survey. The NWIS is scheduled to be placed in operation in 1990.

Effect of Interactive River Routing on North Atlantic Overturning in a Simulation of the last Deglaciation

NASA Astrophysics Data System (ADS)

Mikolajewicz, Uwe; Ziemen, Florian; Kapsch, Marie; Meccia, Virna

2017-04-01

One of the major challenges in climate modeling is the simulation of glacial-interglacial transitions. A few models of intermediate complexity have been successful in simulating the last termination. Complex atmosphere-ocean general circulation models (AOGCMs) with prescribed ice sheets are able to yield realistic climate changes. Here we present results from our first attempt to simulate a substantial part of the last glacial cycle with an AOGCM coupled interactively with a state-of-the-art ice sheet model. The ECHAM5/MPIOM AOGCM is interactively coupled to the dynamical ice sheet model PISM and the dynamical vegetation model LPJ. The model is integrated from the late Glacial into the Holocene using insolation and greenhouse gas concentrations as transient forcing. To make the long simulations feasible, the atmosphere is accelerated by a factor of 10 relative to the other components using a periodical-synchronous coupling technique. The land sea mask remains fixed at the LGM state. River routing and surface elevation are calculated interactively. A mini-ensemble with different initial conditions is performed. Additionally, one fully synchronously simulation, without acceleration in the atmosphere, is run. In all simulations the northern hemisphere deglaciation starts between 18 and 17 kyr BP, consistent with the onset of global warming. The model produces Heinrich event like variability. These rapid ice discharge events have a strong impact on the North Atlantic meridional overturning circulation (NAMOC). The interactive river routing has a strong impact on the simulated NAMOC during the deglaciation. The retreat of the Laurentide Ice Sheet together with the depressed topography due to the former ice load leads to a redirection of the river routes.. In particular, the discharge route for runoff from the melting southwestern Laurentide shifts from the Gulf of Mexico to the Arctic. The consequence is a rapid reduction/suppression of the North Atlantic deep water (NADW) formation. When the Laurentide Ice Sheet retreats from the Hudson Strait, this becomes the new drainage route. Hence, fresh water is released into the Labrador Sea and is less effective in suppressing the deep water formation in the North Atlantic. As a consequence, the NADW formation recovers within a few decades. Our results show the potential importance of interactive river routing for rapid changes in NAMOC strength during the deglaciation.

Apparent Resistivity and Estimated Interaction Potential of Surface Water and Groundwater along Selected Canals and Streams in the Elkhorn-Loup Model Study Area, North-Central Nebraska, 2006-07

USGS Publications Warehouse

Teeple, Andrew; Vrabel, Joseph; Kress, Wade H.; Cannia, James C.

2009-01-01

In 2005, the State of Nebraska adopted new legislation that in part requires local Natural Resources Districts to include the effect of groundwater use on surface-water systems in their groundwater management plan. In response the U.S. Geological Survey, in cooperation with the Upper Elkhorn, Lower Elkhorn, Upper Loup, Lower Loup, Middle Niobrara, Lower Niobrara, Lewis and Clark, and Lower Platte North Natural Resources Districts, did a study during 2006-07 to investigate the surface-water and groundwater interaction within a 79,800-square-kilometer area in north-central Nebraska. To determine how streambed materials affect surface-water and groundwater interaction, surface geophysical and lithologic data were integrated at four sites to characterize the hydrogeologic conditions within the study area. Frequency-domain electromagnetic and waterborne direct- current resistivity profiles were collected to map the near-surface hydrogeologic conditions along sections of Ainsworth Canal near Ainsworth, Nebraska; Mirdan and Geranium Canals near Ord, Nebraska; North Loup River near Ord, Nebraska; and Middle Loup River near Thedford, Nebraska. Lithologic data were collected from test holes at each site to aid interpretation of the geophysical data. Geostatistical analysis incorporating the spatial variability of resistivity was used to account for the effect of lithologic heterogeneity on effective hydraulic permeability. The geostatistical analysis and lithologic data descriptions were used to make an interpretation of the hydrogeologic system and derive estimates of surface-water/groundwater interaction potential within the canals and streambeds. The estimated interaction potential at the Ainsworth Canal site and the Mirdan and Geranium Canal site is generally low to moderately low. The sediment textures at nearby test holes typically were silt and clay and fine-to-medium sand. The apparent resistivity values for these sites ranged from 2 to 120 ohm-meters. The vertical and horizontal variability of the apparent resistivity data were consistently low. Low resistive variability indicates little lithologic heterogeneity for either canal site. The surface-water/groundwater interaction-potential estimates are in agreement with the narrow frequency distribution of resistivity, low apparent resistivities, low spatial heterogeneity, and test-hole grain-size ranges. The estimated surface-water/groundwater interaction potential at the North Loup and Middle Loup River sites is moderate to moderately high. The sediment textures at nearby test holes were predominantly fine, medium, and coarse sand with some silt and silty to sandy clay. The apparent resistivity values for these sites ranged from 34 to 1,338 ohm-meters. The vertical variability of the resistivity data was moderately high. The horizontal variability at these sites is low to moderately low. The higher resistive variability at these sites indicates generally greater lithologic heterogeneity than at either the Ainsworth Canal site or the Mirdan and Geranium Canal site. The surface-water/groundwater interaction-potential estimates are in agreement with the generally moderate to high apparent resistivity, the greater spatial heterogeneity, and the variable lithologic texture. A higher interaction potential as compared to the canal sites is expected because of the higher subsurface resistivity and greater lithologic heterogeneity.

Hydrographs Showing Groundwater Level Changes for Selected Wells in the Chambers-Clover Creek Watershed and Vicinity, Pierce County, Washington

USGS Publications Warehouse

Justin, G.B.; Julich, R.; Payne, K.L.

2009-01-01

Selected groundwater level hydrographs for the Chambers-Clover Creek watershed (CCCW) and vicinity, Washington, are presented in an interactive web-based map to illustrate changes in groundwater levels in and near the CCCW on a monthly and seasonal basis. Hydrographs are linked to points corresponding to the well location on an interactive map of the study area. Groundwater level data and well information from Federal, State, and local agencies were obtained from the U.S. Geological Survey National Water Information System (NWIS), Groundwater Site Inventory (GWSI) System.

Structure and dynamics of cationic membrane peptides and proteins: Insights from solid-state NMR

PubMed Central

Hong, Mei; Su, Yongchao

2011-01-01

Many membrane peptides and protein domains contain functionally important cationic Arg and Lys residues, whose insertion into the hydrophobic interior of the lipid bilayer encounters significant energy barriers. To understand how these cationic molecules overcome the free energy barrier to insert into the lipid membrane, we have used solid-state NMR spectroscopy to determine the membrane-bound topology of these peptides. A versatile array of solid-state NMR experiments now readily yields the conformation, dynamics, orientation, depth of insertion, and site-specific protein–lipid interactions of these molecules. We summarize key findings of several Arg-rich membrane peptides, including β-sheet antimicrobial peptides, unstructured cell-penetrating peptides, and the voltage-sensing helix of voltage-gated potassium channels. Our results indicate the central role of guanidinium-phosphate and guanidinium-water interactions in dictating the structural topology of these cationic molecules in the lipid membrane, which in turn account for the mechanisms of this functionally diverse class of membrane peptides. PMID:21344534

Quantifying human impact on hydrological drought using an Earth System Model

NASA Astrophysics Data System (ADS)

van Huijgevoort, Marjolein; Chaney, Nathaniel; Malyshev, Sergey; Shevliakova, Elena; Milly, Chris

2017-04-01

Predicting the human impact on the present and future hydrological cycle remains a significant scientific challenge. Anthropogenic impact includes water management practices like diverting water for irrigation, abstraction of groundwater, and reservoirs. Hydrological extremes, in particular, are heavily affected by water management practices, due to the existing stress on the system during droughts and floods. Therefore, to prepare adaptation plans for hydrological extremes in the future, it is essential to account for water management and other human influences in Earth System Models. In this study we have implemented water management practices in the state-of-the-art GFDL land model, which includes terrestrial water, energy, and carbon balances. Both irrigation practices and reservoirs have been added in the land surface model component of the model. Irrigation amounts are determined from the soil water balance, the evaporative demand of the vegetation and fractional coverage of croplands. The resulting water demand is fulfilled by abstractions from surface water and groundwater. Reservoir outflow is dynamically coupled to the downstream water demand and available reservoir storage. Retrospective model simulations over the contiguous United States indicate a strong human influence on hydrological drought. A water management attribution analysis shows a significant impact on the water availability, mostly in the Midwest of the United States and California. Implementation of reservoirs alters the flow regime, thereby decreasing the short-term drought impact, however, in the case of multi-year drought, impacts are delayed due to the dependency on the reservoir outflow. Irrigation, on the other hand, decreases the water availability in rivers due to increased evapotranspiration leading to a higher drought impact. The average increase in evapotranspiration amounted up to 2 mm/day for cropland areas in California and Texas. Overall, the results show the importance of including water management in global scale models. This new modelling framework can be used to understand how humans will impact future water availability, water scarcity, and drought. Next steps will include coupled model simulations to investigate the human impact on feedbacks in land-atmosphere interactions.

Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability

NASA Astrophysics Data System (ADS)

Zhou, Shu-Ya; Ma, Shui-Xian; Cheng, Hui-Lin; Yang, Li-Juan; Chen, Wen; Yin, Yan-Qing; Shi, Yi-Min; Yang, Xiao-Dong

2014-01-01

The inclusion complexation behavior, characterization and binding ability of pinocembrin with β-cyclodextrin (β-CD) and its derivative 2-hydroxypropyl-β-cyclodextrin (HPβCD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

Towards First Principles-Based Prediction of Highly Accurate Electrochemical Pourbaix Diagrams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Zhenhua; Chan, Maria K. Y.; Zhao, Zhi-Jian

2015-08-13

Electrochemical potential/pH (Pourbaix) diagrams underpin many aqueous electrochemical processes and are central to the identification of stable phases of metals for processes ranging from electrocatalysis to corrosion. Even though standard DFT calculations are potentially powerful tools for the prediction of such diagrams, inherent errors in the description of transition metal (hydroxy)oxides, together with neglect of van der Waals interactions, have limited the reliability of such predictions for even the simplest pure metal bulk compounds, and corresponding predictions for more complex alloy or surface structures are even more challenging. In the present work, through synergistic use of a Hubbard U correction,more » a state-of-the-art dispersion correction, and a water-based bulk reference state for the calculations, these errors are systematically corrected. The approach describes the weak binding that occurs between hydroxyl-containing functional groups in certain compounds in Pourbaix diagrams, corrects for self-interaction errors in transition metal compounds, and reduces residual errors on oxygen atoms by preserving a consistent oxidation state between the reference state, water, and the relevant bulk phases. The strong performance is illustrated on a series of bulk transition metal (Mn, Fe, Co and Ni) hydroxides, oxyhydroxides, binary, and ternary oxides, where the corresponding thermodynamics of redox and (de)hydration are described with standard errors of 0.04 eV per (reaction) formula unit. The approach further preserves accurate descriptions of the overall thermodynamics of electrochemically-relevant bulk reactions, such as water formation, which is an essential condition for facilitating accurate analysis of reaction energies for electrochemical processes on surfaces. The overall generality and transferability of the scheme suggests that it may find useful application in the construction of a broad array of electrochemical phase diagrams, including both bulk Pourbaix diagrams and surface phase diagrams of interest for corrosion and electrocatalysis.« less

Developing models that analyze the economic/environmental trade-offs implicit in water resource management

NASA Astrophysics Data System (ADS)

Howitt, R. E.

2016-12-01

Hydro-economic models have been used to analyze optimal supply management and groundwater use for the past 25 years. They are characterized by an objective function that usually maximizes economic measures such as consumer and producer surplus subject to hydrologic equations of motion or water distribution systems. The hydrologic and economic components are sometimes fully integrated. Alternatively they may use an iterative interactive process. Environmental considerations have been included in hydro-economic models as inequality constraints. Representing environmental requirements as constraints is a rigid approximation of the range of management alternatives that could be used to implement environmental objectives. The next generation of hydro-economic models, currently being developed, require that the environmental alternatives be represented by continuous or semi-continuous functions which relate water resource use allocated to the environment with the probabilities of achieving environmental objectives. These functions will be generated by process models of environmental and biological systems which are now advanced to the state that they can realistically represent environmental systems and flexibility to interact with economic models. Examples are crop growth models, climate modeling, and biological models of forest, fish, and fauna systems. These process models can represent environmental outcomes in a form that is similar to economic production functions. When combined with economic models the interacting process models can reproduce a range of trade-offs between economic and environmental objectives, and thus optimize social value of many water and environmental resources. Some examples of this next-generation of hydro-enviro- economic models are reviewed. In these models implicit production functions for environmental goods are combined with hydrologic equations of motion and economic response functions. We discuss models that show interaction between environmental goods and agricultural production, and others that address alternative climate change policies, or habitat provision.

Evolution of Hydro-systems: The 500-Year Challenge

NASA Astrophysics Data System (ADS)

Vörösmarty, C. J.; Band, L.; Lettenmaier, D. P.; Vogel, R. M.; Green, M. B.; Hermans, C.

2008-12-01

We take as our starting point the tenet that humans are rapidly embedding themselves into the basic character of the water cycle, through a myriad of processes including direct water abstraction and flow diversion, land cover change, pollution, destruction of aquatic biodiversity, and climate change as part of a broad transformation and co-option of natural ecosystem services by society. Given this modern-day reality, it is now difficult to view hydrology as a purely nature-dominated science. Hydraulic engineering, land use and land cover change, and protecting society from the vagaries of climate all figure prominently in any discussion of the state and dynamics of the contemporary water cycle. Traditional initial and boundary conditions for hydrologic problems are no longer applicable in heavily populated or economically developing parts of the world. Initial and boundary conditions are instead dependent on a myriad of legacy effects associated with human decision-making, economics, governance, politics, culture, and even religion that may have taken place in times long gone and in settings far upstream of a particular downstream area of interest. Reconstructing time series of human-water cycle interactions and establishing their connectivity over time and space can afford insight into the co-evolution of biogeophysical and social dynamics with hydrologic cycle state, its variability, and trajectories. It also provides an important opportunity to break down traditional disciplinary boundaries associated with water and environmental studies more generally. The Northeast Corridor of the U.S. provides an ideal setting for testing these notions, and a millennial-scale perspective affords us the opportunity to quantify and assess the evolution of human-water interactions from the time of first European settlement into the 21st century. Such an assessment provides the necessary benchmark against which we can improve our understanding of the modern evolution of highly engineered water and land systems, and gives us a perspective on unfolding strategic water issues into the remainder of this century. This talk will present an overview of the rationale, modes of execution, and early results emerging from an NSF-funded hydrologic synthesis prototype effort.

Ultrasonic evidence of hydrophobic interactions. Effect of ultrasound on benzoin condensation and some other reactions in aqueous ethanol.

PubMed

Tuulmets, Ants; Hagu, Hannes; Salmar, Siim; Cravotto, Giancarlo; Järv, Jaak

2007-03-29

The kinetics of KCN-catalyzed benzoin condensation of benzaldehyde in water and ethanol-water binary mixtures was investigated both under ultrasound at 22 kHz and without sonication. Thermodynamic activation parameters were calculated from kinetic data obtained at 35, 50, and 65 degrees C. Evidence that ultrasound can retard reactions is reported and hence a direct proof that sonochemical processes occur in the bulk solution. Former results and literature data for ester hydrolyses and tert-butyl chloride solvolysis are involved in the discussion. A quantitative relationship between sonication effects and the hydrophobicity of reagents is presented for the first time. Ultrasound affects hydrophobic interactions with the solvent, which are not manifested in conventional kinetics. When it suppresses the stabilization of the encounter complexes between reagents, sonication hinders the reaction but accelerates it when it perturbs the hydrophobic stabilization of the ground state of a reagent.

Hydrogeologic Characteristics of the St. Croix River Basin, Minnesota and Wisconsin: Implications for the Susceptibility of Ground Water to Potential Contamination

USGS Publications Warehouse

Juckem, Paul F.

2007-01-01

Population growth in the St. Croix River Basin in Minnesota and Wisconsin has intensified concerns of county resource managers and the National Park Service, which is charged with protecting the St. Croix National Scenic Riverway, about the potential for ground-water contamination in the basin. This report describes a previously developed method that was adapted to illustrate potential ground-water-contamination susceptibility in the St. Croix River Basin. The report also gives an estimate of ground-water-residence time and surface-water/ground-water interaction as related to natural attenuation and movement of contaminants in five tributary basins. A ground-water-contamination-susceptibility map was adapted from a state-wide map of Wisconsin to the St. Croix River Basin by use of well-driller construction records and regional maps of aquifer properties in Minnesota and Wisconsin. Measures of various subsurface properties were combined to generate a spatial index of susceptibility. The subjective index method developed for the State of Wisconsin by Schmidt (1987) was not derived from analyses of water-quality data or physical processes. Nonetheless, it was adapted for this report to furnish a seamless map across state boundaries that would be familiar to many resource managers. Following this method, areas most susceptible to contamination appear to have coarse-grained sediments (sands or gravels) and shallow water tables or are underlain by carbonate-bedrock aquifers. The least susceptible areas appear to have fine-grained sediments and deep water tables. If an aquifer becomes contaminated, the ground-water-residence time can affect potential natural attenuation along the ground-water-flow path. Mean basin ground-water-residence times were computed for the Apple, Kettle, Kinnickinnic, Snake and Sunrise River Basins, which are tributary basins to the St. Croix Basin, by use of average aquifer properties of saturated thickness, porosity, and recharge rates. The Apple River Basin had the shortest mean ground-water-residence times (20-120 years), owing largely to the moderate saturated thickness and high recharge rate in the basin. The Kinnickinnic and Sunrise River Basins had the longest mean residence times (60-350 and 70-390 years, respectively) chiefly because of the relatively large saturated thickness of the basins. Owing to limitations of the residence-time calculations, actual ground-water-residence times will vary around the mean values within each basin and may range from days or weeks in karst carbonate aquifers to millennia in deep confined sandstone aquifers. Areas of relatively short residence time (less than the median residence time in each basin) were identified by use of ground-water-flow models for each of the five tributary basins. Results of simulations show that these areas, in which contaminants may have relatively less time for natural attenuation along the short flow paths, generally occur near streams and rivers where ground water discharges to the surface. Finally, the ground-water-flow models were used to simulate ground-water/surface-water interaction in the five tributary basins. Results of simulations show that some lakes and reservoirs leak surface water into the ground-water-flow system on their downgradient side, where the surface-water outflow has been restricted by a dam or a naturally constricted outlet. These locations are noteworthy because contaminated surface waters could potentially enter the ground-water-flow system at these locations.

Projected effects of proposed chloride-control projects on shallow ground water; preliminary results for the Wichita River basin, Texas

USGS Publications Warehouse

Garza, Sergio

1983-01-01

Two-dimensional mathematical computer models were developed for aquifer simulation of: (1) Steady-state conditions in a fresh-water system and (2) transient conditions in a brine- fresh-water system where the density effects of the brine are considered. The main results 'of projecting the effects of the proposed Truscott Brine Lake on the fresh-water aquifer are: (1) Hydraulic head rises of 5 to 40 feet would be confined to areas near the proposed dam and along the lake shoreline, and (2) migration of salt water downstream from the dam generally would be limited to less than 1 mile and apparently would not reach equilibrium during the 100-year duration of the project. The modeling efforts did not include possible effects related to hydrodynamic dispersion in the brine- fresh-water system. Possible changes in the hydraulic conductivity of the aquifer, due to physical and chemical interactions in the brine and fresh-water environments, also were not considered.

Interactions of water quality and integrated groundwater management: Examples from the United States and Europe: Chapter 14

USGS Publications Warehouse

Warner, Kelly L.; Barataud, Fabienne; Hunt, Randall J.; Benoit, Marc; Anglade, Juliette; Borchardt, Mark A.

2015-01-01

Groundwater is available in many parts of the world, but the quality of the water may limit its use. Contaminants can limit the use of groundwater through concerns associated with human health, aquatic health, economic costs, or even societal perception. Given this broad range of concerns, this chapter focuses on examples of how water quality issues influence integrated groundwater management. One example evaluates the importance of a naturally occurring contaminant Arsenic (As) for drinking water supply, one explores issues resulting from agricultural activities on the land surface and factors that influence related groundwater management, and the last examines unique issues that result from human-introduced viral pathogens for groundwater-derived drinking water vulnerability. The examples underscore how integrated groundwater management lies at the intersections of environmental characterization, engineering constraints, societal needs, and human perception of acceptable water quality. As such, water quality factors can be a key driver for societal decision making.

High-resolution Continental Scale Land Surface Model incorporating Land-water Management in United States

NASA Astrophysics Data System (ADS)

Shin, S.; Pokhrel, Y. N.

2016-12-01

Land surface models have been used to assess water resources sustainability under changing Earth environment and increasing human water needs. Overwhelming observational records indicate that human activities have ubiquitous and pertinent effects on the hydrologic cycle; however, they have been crudely represented in large scale land surface models. In this study, we enhance an integrated continental-scale land hydrology model named Leaf-Hydro-Flood to better represent land-water management. The model is implemented at high resolution (5km grids) over the continental US. Surface water and groundwater are withdrawn based on actual practices. Newly added irrigation, water diversion, and dam operation schemes allow better simulations of stream flows, evapotranspiration, and infiltration. Results of various hydrologic fluxes and stores from two sets of simulation (one with and the other without human activities) are compared over a range of river basin and aquifer scales. The improved simulations of land hydrology have potential to build consistent modeling framework for human-water-climate interactions.

WaterNet:The NASA Water Cycle Solutions Network

NASA Astrophysics Data System (ADS)

Belvedere, D. R.; Houser, P. R.; Pozzi, W.; Imam, B.; Schiffer, R.; Schlosser, C. A.; Gupta, H.; Martinez, G.; Lopez, V.; Vorosmarty, C.; Fekete, B.; Matthews, D.; Lawford, R.; Welty, C.; Seck, A.

2008-12-01

Water is essential to life and directly impacts and constrains society's welfare, progress, and sustainable growth, and is continuously being transformed by climate change, erosion, pollution, and engineering. Projections of the effects of such factors will remain speculative until more effective global prediction systems and applications are implemented. NASA's unique role is to use its view from space to improve water and energy cycle monitoring and prediction, and has taken steps to collaborate and improve interoperability with existing networks and nodes of research organizations, operational agencies, science communities, and private industry. WaterNet is a Solutions Network, devoted to the identification and recommendation of candidate solutions that propose ways in which water-cycle related NASA research results can be skillfully applied by partner agencies, international organizations, state, and local governments. It is designed to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend NASA research results to augment Decision Support Tools that address national needs.

Numerical-simulation and conjunctive-management models of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system, Rhode Island

USGS Publications Warehouse

Barlow, Paul M.; Dickerman, David C.

2001-01-01

This report describes the development, application, and evaluation of numerical-simulation and conjunctive-management models of the Hunt-Annaquatucket-Pettaquamscutt stream-aquifer system in central Rhode Island. Steady-state transient numerical models were developed to improve the understanding of the hydrologic budget of the system, the interaction of ground-water and surface-water components of the system, and the contributing areas and sources of water to supply wells in the system. The numerical models were developed and calibrated on the basis of hydrologic data collected during this and previous investigations. These data include lithologic information for the aquifer; hydraulic properties of aquifer and streambed materials; recharge to the aquifer; water levels measured in wells, ponds, and streambed piezometers; streamflow measurements for various streams within the system; and ground-water withdrawal rates from, and wastewater discharge to, the aquifer.

Assessment of Effectiveness of Geologic Isolation Systems. Variable thickness transient ground-water flow model. Volume 2. Users' manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reisenauer, A.E.

1979-12-01

A system of computer codes to aid in the preparation and evaluation of ground-water model input, as well as in the computer codes and auxillary programs developed and adapted for use in modeling major ground-water aquifers is described. The ground-water model is interactive, rather than a batch-type model. Interactive models have been demonstrated to be superior to batch in the ground-water field. For example, looking through reams of numerical lists can be avoided with the much superior graphical output forms or summary type numerical output. The system of computer codes permits the flexibility to develop rapidly the model-required data filesmore » from engineering data and geologic maps, as well as efficiently manipulating the voluminous data generated. Central to these codes is the Ground-water Model, which given the boundary value problem, produces either the steady-state or transient time plane solutions. A sizeable part of the codes available provide rapid evaluation of the results. Besides contouring the new water potentials, the model allows graphical review of streamlines of flow, travel times, and detailed comparisons of surfaces or points at designated wells. Use of the graphics scopes provide immediate, but temporary displays which can be used for evaluation of input and output and which can be reproduced easily on hard copy devices, such as a line printer, Calcomp plotter and image photographs.« less

Theoretical and experimental investigation of drug-polymer interaction and miscibility and its impact on drug supersaturation in aqueous medium.

PubMed

Baghel, Shrawan; Cathcart, Helen; O'Reilly, Niall J

2016-10-01

Amorphous solid dispersions (ASDs) have the potential to offer higher apparent solubility and bioavailability of BCS class II drugs. Knowledge of the solid state drug-polymer solubility/miscibility and their mutual interaction are fundamental requirements for the effective design and development of such systems. To this end, we have carried out a comprehensive investigation of various ASD systems of dipyridamole and cinnarizine in polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) at different drug loadings. Theoretical and experimental examinations (by implementing binary and ternary Flory-Huggins (F-H) theory) related to drug-polymer interaction/miscibility including solubility parameter approach, melting point depression method, phase diagram, drug-polymer interaction in the presence of moisture and the effect of drug loading on interaction parameter were performed. The information obtained from this study was used to predict the stability of ASDs at different drug loadings and under different thermal and moisture conditions. Thermal and moisture sorption analysis not only provided the composition-dependent interaction parameter but also predicted the composition dependent miscibility. DPM-PVP, DPM-PAA and CNZ-PAA systems have shown molecular level mixing over the complete range of drug loading. For CNZ-PVP, the presence of a single Tg at lower drug loadings (10, 20 and 35%w/w) indicates the formation of solid solution. However, drug recrystallization was observed for samples with higher drug weight fractions (50 and 65%w/w). Finally, the role of polymer in maintaining drug supersaturation has also been explored. It has been found that drug-polymer combinations capable of hydrogen-bonding in the solution state (DPM-PVP, DPM-PAA and CNZ-PAA) are more effective in preventing drug crystallization compared to the drug-polymer systems without such interaction (CNZ-PVP). The DPM-PAA system outperformed all other ASDs in various stability conditions (dry-state, in the presence of moisture and in solution state), which was attributed to the drug's low crystallization tendency, the strong DPM-PAA interaction, the robustness of this interaction against moisture or water and the ability of PAA in maintaining DPM supersaturation. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantum-rotor-induced polarization.

PubMed

Meier, Benno

2018-07-01

Quantum-rotor-induced polarization is closely related to para-hydrogen-induced polarization. In both cases, the hyperpolarized spin order derives from rotational interaction and the Pauli principle by which the symmetry of the rotational ground state dictates the symmetry of the associated nuclear spin state. In quantum-rotor-induced polarization, there may be several spin states associated with the rotational ground state, and the hyperpolarization is typically generated by hetero-nuclear cross-relaxation. This review discusses preconditions for quantum-rotor-induced polarization for both the 1-dimensional methyl rotor and the asymmetric rotor H 2 17 O@C 60 , that is, a single water molecule encapsulated in fullerene C 60 . Experimental results are presented for both rotors. Copyright © 2018 John Wiley & Sons, Ltd.

Water Availability--The Connection Between Water Use and Quality

USGS Publications Warehouse

Hirsch, Robert M.; Hamilton, Pixie A.; Miller, Timothy L.; Myers, Donna N.

2008-01-01

Water availability has become a high priority in the United States, in large part because competition for water is becoming more intense across the Nation. Population growth in many areas competes with demands for water to support irrigation and power production. Cities, farms, and power plants compete for water needed by aquatic ecosystems to support their minimum flow requirements. At the same time, naturally occurring and human-related contaminants from chemical use, land use, and wastewater and industrial discharge are introduced into our waters and diminish its quality. The fact that degraded quality limits the availability and suitability of water for critical uses is a well-known reality in many communities. What may be less understood, but equally true, is that our everyday use of water can significantly affect water quality, and thus its availability. Landscape features (such as geology, soils, and vegetation) along with water-use practices (such as ground-water withdrawals and irrigation) govern water availability because, together, they affect the movement of chemical compounds over the land and in the subsurface. Understanding the interactions of human activities with natural sources and the landscape is critical to effectively managing water and sustaining water availability in the future.

Theoretical investigation of interaction of sorbitol molecules with alcohol dehydrogenase in aqueous solution using molecular dynamics simulation.

PubMed

Bahrami, Homayoon; Zahedi, Mansour; Moosavi-Movahedi, Ali Akbar; Azizian, Homa; Amanlou, Massoud

2011-03-01

The nature of protein-sorbitol-water interaction in solution at the molecular level, has been investigated using molecular dynamics simulations. In order to do this task, two molecular dynamics simulations of the protein ADH in solution at room temperature have been carried out, one in the presence (about 0.9 M) and another in the absence of sorbitol. The results show that the sorbitol molecules cluster and move toward the protein, and form hydrogen bonds with protein. Also, coating by sorbitol reduces the conformational fluctuations of the protein compared to the sorbitol-free system. Thus, it is concluded that at moderate concentration of sorbitol solution, sorbitol molecules interact with ADH via many H-bonds that prevent the protein folding. In fact, at more concentrated sorbitol solution, water and sorbitol molecules accumulate around the protein surface and form a continuous space-filling network to reduce the protein flexibility. Namely, in such solution, sorbitol molecules can stabilize a misfolded state of ADH, and prevent the protein from folding to its native structure.

Understanding the Interaction of Pluronics L61 and L64 with a DOPC Lipid Bilayer: An Atomistic Molecular Dynamics Study

DOE PAGES

Ileri Ercan, Nazar; Stroeve, Pieter; Tringe, Joseph W.; ...

2016-09-13

In this paper, we investigate the interactions of Pluronics L61 and L64 with a dioleylphosphatidylcholine (DOPC) lipid bilayer by atomistic molecular dynamics simulations using the all-atom OPLS force field. Our results show that the initial configuration of the polymer with respect to the bilayer determines its final conformation within the bilayer. When the polymer is initially placed at the lipid/water interface, we observe partial insertion of the polymer in a U-shaped conformation. On the other hand, when the polymer is centered at the bilayer, it stabilizes to a transmembrane state, which facilitates water transport across the bilayer. We show thatmore » membrane thickness decreases while its fluidity increases in the presence of Pluronics. When the polymer concentration inside the bilayer is high, pore formation is initiated with L64. Finally, our results show good agreement with existing experimental data and reveal that the hydrophilic/lipophilic balance of the polymer plays a critical role in the interaction mechanisms as well as in the dynamics of Pluronics with and within the bilayer.« less

Water dynamics on ice and hydrate lattices studied by second-order central-line stimulated-echo oxygen-17 nuclear magnetic resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adjei-Acheamfour, Mischa; Tilly, Julius F.; Beerwerth, Joachim

Oxygen-17 stimulated-echo spectroscopy is a novel nuclear magnetic resonance (NMR) technique that allows one to investigate the time scale and geometry of ultraslow molecular motions in materials containing oxygen. The method is based on detecting orientationally encoded frequency changes within oxygen’s central-transition NMR line that are caused by second-order quadrupolar interactions. In addition to the latter, the present theoretical analysis of various two-pulse echo and stimulated-echo pulse sequences takes also heteronuclear dipolar interactions into account. As an experimental example, the ultraslow water motion in polycrystals of tetrahydrofuran clathrate hydrate is studied via two-time oxygen-17 stimulated-echo correlation functions. The resulting correlationmore » times and those of hexagonal ice are similar to those from previous deuteron NMR measurements. Calculations of the echo functions’ final-state correlations for various motional models are compared with the experimental data of the clathrate hydrate. It is found that a six-site model including the oxygen-proton dipolar interaction describes the present results.« less

Water-vapor foreign-continuum absorption in the 8-12 and 3-5 μm atmospheric windows

NASA Astrophysics Data System (ADS)

Klimeshina, T. E.; Rodimova, O. B.

2015-08-01

The frequency and temperature dependence of the water vapor-nitrogen continuum in the 8-12 and 3-5 μm spectral regions obtained experimentally by CAVIAR and NIST is described with the use of the line contour constructed on the basis of asymptotic line shape theory. The parameters of the theory found from fitting the calculated values of the absorption coefficient to the pertinent experimental data enter into the expression for the classical potential describing the center-of-mass motion of interacting molecules and into the expression for the quantum potential of two interacting molecules. The frequency behavior of the line wing contours appears to depend on the band the lines of which make a major contribution to the absorption in a given spectral interval. The absorption coefficients in the wings of the band in question calculated with the line contours obtained for other bands are outside of experimental errors. The distinction in the line wing behavior may be explained by the difference in the quantum energies of molecules interacting in different vibrational states.

Swelling properties of montmorillonite and beidellite clay minerals from molecular simulation: Comparison of temperature interlayer cation, and charge location effects

DOE PAGES

Teich-McGoldrick, Stephanie L.; Greathouse, Jeffery A.; Jove-Colon, Carlos F.; ...

2015-08-27

In this study, the swelling properties of smectite clay minerals are relevant to many engineering applications including environmental remediation, repository design for nuclear waste disposal, borehole stability in drilling operations, and additives for numerous industrial processes and commercial products. We used molecular dynamics and grand canonical Monte Carlo simulations to study the effects of layer charge location, interlayer cation, and temperature on intracrystalline swelling of montmorillonite and beidellite clay minerals. For a beidellite model with layer charge exclusively in the tetrahedral sheet, strong ion–surface interactions shift the onset of the two-layer hydrate to higher water contents. In contrast, for amore » montmorillonite model with layer charge exclusively in the octahedral sheet, weaker ion–surface interactions result in the formation of fully hydrated ions (two-layer hydrate) at much lower water contents. Clay hydration enthalpies and interlayer atomic density profiles are consistent with the swelling results. Water adsorption isotherms from grand canonical Monte Carlo simulations are used to relate interlayer hydration states to relative humidity, in good agreement with experimental findings.« less

Biluminescence via Fluorescence and Persistent Phosphorescence in Amorphous Organic Donor(D4)-Acceptor(A) Conjugates, and Application in Data Security Protection.

PubMed

Bhatia, Harsh; Bhattacharjee, Indranil; Ray, Debdas

2018-06-25

Purely organic biluminescent materials are of great interest due to the involvement of both singlet and long-lived triplet emissions, which have been used in bio-imaging and organic light-emitting diodes. We show two molecules 3,4,5,6-tetraphenyloxy-phthlonitrile (POP) and 3,4,5,6-tetrakis-p-tolyloxy-phthalonitrile (TOP), in which POP was found to exhibit fluorescence and persistent room-temperature green phosphorescence (pRTGP) in the amorphous and crystal states. Both POP and TOP show aggregation induced emission in tetrahydrofuran-water mixture. We found in single crystal X-ray analysis that intra-and inter molecular lp(O)•••π interactions along with (π(C=C)•••π(C≡N), hydrogen bond (H-B), and C-H•••π interactions induce head-to-tail slipped-stacked arrangement in POP. In addition, X-ray structure of TOP with slipped-stack arrangement induced by only (π(C=C)•••π(C≡N) and H-B interactions, shows dim afterglow only in crystals. These indicate that more number of non-covalent interactions may reinforce relatively efficient inter system crossing that leads to pRTGP even in the amorphous state of POP. Given the unique green afterglow feature in amorphous state of POP, document security protection application is achievable.

Effects of sucrose concentration and water deprivation on Pavlovian conditioning and responding for conditioned reinforcement.

PubMed

Tabbara, Rayane I; Maddux, Jean-Marie N; Beharry, Priscilla F; Iannuzzi, Jessica; Chaudhri, Nadia

2016-04-01

An appetitive Pavlovian conditioned stimulus (CS) can predict an unconditioned stimulus (US) and acquire incentive salience. We tested the hypothesis that US intensity and motivational state of the subject would influence Pavlovian learning and impact the attribution of incentive salience to an appetitive Pavlovian CS. To this end, we examined the effects of sucrose concentration and water deprivation on the acquisition of Pavlovian conditioning and responding for a conditioned reinforcer. Male Long-Evans rats (Harlan; 220-240 g) receiving 3% (3S) or 20% (20S) sucrose were either non-water deprived or given water for 1 hr per day. During Pavlovian conditioning sessions, half the rats in each concentration and deprivation condition received a 10-s CS paired with 0.2 ml of sucrose (16 trials/session; 3.2 ml/session). The remainder received unpaired CS and US presentations. Entries into a port where sucrose was delivered were recorded. Next, responding for conditioned reinforcement was tested, wherein pressing an active lever produced the CS and pressing an inactive lever had no consequences. CS-elicited port entries increased, and latency to the first CS-elicited port entry decreased across sessions in paired groups. Water deprivation augmented these effects, whereas sucrose concentration had no significant impact on behavior. Responding for conditioned reinforcement was observed in the 20S water-deprived, paired group. Thus, water deprivation can facilitate the acquisition of Pavlovian conditioning, potentially by enhancing motivational state, and a high-intensity US and a high motivational state can interact to heighten the attribution of incentive salience to an appetitive Pavlovian CS. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Relationship between β-relaxation and structural stability of lysozyme: Microscopic insight on thermostabilization mechanism by trehalose from Raman spectroscopy experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hédoux, Alain, E-mail: alain.hedoux@univ-lille1.fr; Paccou, Laurent; Guinet, Yannick

Raman investigations were carried out in the low-frequency and amide I regions on lysozyme aqueous solutions in absence and presence of trehalose. Raman spectroscopy gives the unique opportunity to analyze the protein and solvent dynamics in the low-frequency range while monitoring the unfolding process by capturing the spectrum of the amide I band. From the analysis of the quasielastic intensity, a dynamic change is firstly observed in a highly hydrated protein, around 70 °C, and interpreted in relation with the denaturation mechanism of the protein. The use of heavy water and partly deuterated trehalose gives clear information on protein–trehalose interactions inmore » the native state of lysozyme (at room temperature) and during the thermal denaturation process of lysozyme. At room temperature, it was found that trehalose is preferentially excluded from the protein surface, and has a main effect on the tetrahedral local order of water molecules corresponding to a stiffening of the H-bond network in the solvent. The consequence is a significant reduction of the amplitude of fast relaxational motions, inducing a less marked dynamic transition shifted toward the high temperatures. Upon heating, interaction between trehalose and lysozyme is detected during the solvent penetration within the protein, i.e., while the native globular state softens into a molten globule (MG) state. Addition of trehalose reduces the protein flexibility in the MG state, improving the structural stability of the protein, and inhibiting the protein aggregation.« less

Characterization of Hydrophobic Interactions of Polymers with Water and Phospholipid Membranes Using Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Drenscko, Mihaela

Polymers and lipid membranes are both essential soft materials. The structure and hydrophobicity/hydrophilicity of polymers, as well as the solvent they are embedded in, ultimately determines their size and shape. Understating the variation of shape of the polymer as well as its interactions with model biological membranes can assist in understanding the biocompatibility of the polymer itself. Computer simulations, in particular molecular dynamics, can aid in characterization of the interaction of polymers with solvent, as well as polymers with model membranes. In this thesis, molecular dynamics serve to describe polymer interactions with a solvent (water) and with a lipid membrane. To begin with, we characterize the hydrophobic collapse of single polystyrene chains in water using molecular dynamics simulations. Specifically, we calculate the potential of mean force for the collapse of a single polystyrene chain in water using metadynamics, comparing the results between all atomistic with coarse-grained molecular simulation. We next explore the scaling behavior of the collapsed globular shape at the minimum energy configuration, characterized by the radius of gyration, as a function of chain length. The exponent is close to one third, consistent with that predicted for a polymer chain in bad solvent. We also explore the scaling behavior of the Solvent Accessible Surface Area (SASA) as a function of chain length, finding a similar exponent for both all-atomistic and coarse-grained simulations. Furthermore, calculation of the local water density as a function of chain length near the minimum energy configuration suggests that intermediate chain lengths are more likely to form dewetted states, as compared to shorter or longer chain lengths. Next, in order to investigate the molecular interactions between single hydrophobic polymer chains and lipids in biological membranes and at lipid membrane/solvent interface, we perform a series of molecular dynamics simulations of small membranes using all atomistic and coarse-grained methods. The molecular interaction between common polymer chains used in biomedical applications and the cell membrane is unknown. This interaction may affect the biocompatibility of the polymer chains. Molecular dynamics simulations offer an emerging tool to characterize the interaction between common degradable polymer chains used in biomedical applications, such as polycaprolactone, and model cell membranes. We systematically characterize with long-time all-atomistic molecular dynamics simulations the interaction between single polycaprolactone chains of varying chain lengths with a model phospholipid membrane. We find that the length of polymer chain greatly affects the nature of interaction with the membrane, as well as the membrane properties. Furthermore, we next utilize advanced sampling techniques in molecular dynamics to characterize the two-dimensional free energy surface for the interaction of varying polymer chain lengths (short, intermediate, and long) with model cell membranes. We find that the free energy minimum shifts from the membrane-water interface to the hydrophobic core of the phospholipid membrane as a function of chain length. These results can be used to design polymer chain lengths and chemistries to optimize their interaction with cell membranes at the molecular level.

Ground-water recharge in the arid and semiarid southwestern United States - Climatic and geologic framework: Chapter A in Ground-water recharge in the arid and semiarid southwestern United States (Professional Paper 1703)

USGS Publications Warehouse

Stonestrom, David A.; Harrill, James R.; Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Niño and Pacific Decadal Oscillations strongly but irregularly control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of multidecadal droughts unlike any in the modern instrumental record. Anthropogenically induced climate change likely will reduce ground-water recharge through diminished snowpack at higher elevations, and perhaps through increased drought. Future changes in El Niño and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Land-use modifications influence ground-water recharge directly through vegetation, irrigation, and impermeable area, and indirectly through climate change. High ranges bounding the study area—the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east—provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions.

Time-resolved energy transfer in DNA sequence detection using water-soluble conjugated polymers: the role of electrostatic and hydrophobic interactions.

PubMed

Xu, Qing-Hua; Gaylord, Brent S; Wang, Shu; Bazan, Guillermo C; Moses, Daniel; Heeger, Alan J

2004-08-10

We have investigated the energy transfer processes in DNA sequence detection by using cationic conjugated polymers and peptide nucleic acid (PNA) probes with ultrafast pump-dump-emission spectroscopy. Pump-dump-emission spectroscopy provides femtosecond temporal resolution and high sensitivity and avoids interference from the solvent response. The energy transfer from donor (the conjugated polymer) to acceptor (a fluorescent molecule attached to a PNA terminus) has been time resolved. The results indicate that both electrostatic and hydrophobic interactions contribute to the formation of cationic conjugated polymers/PNA-C/DNA complexes. The two interactions result in two different binding conformations. This picture is supported by the average donor-acceptor separations as estimated from time-resolved and steady-state measurements. Electrostatic interactions dominate at low concentrations and in mixed solvents.

Time-resolved energy transfer in DNA sequence detection using water-soluble conjugated polymers: The role of electrostatic and hydrophobic interactions

PubMed Central

Xu, Qing-Hua; Gaylord, Brent S.; Wang, Shu; Bazan, Guillermo C.; Moses, Daniel; Heeger, Alan J.

2004-01-01

We have investigated the energy transfer processes in DNA sequence detection by using cationic conjugated polymers and peptide nucleic acid (PNA) probes with ultrafast pump-dump-emission spectroscopy. Pump-dump-emission spectroscopy provides femtosecond temporal resolution and high sensitivity and avoids interference from the solvent response. The energy transfer from donor (the conjugated polymer) to acceptor (a fluorescent molecule attached to a PNA terminus) has been time resolved. The results indicate that both electrostatic and hydrophobic interactions contribute to the formation of cationic conjugated polymers/PNA-C/DNA complexes. The two interactions result in two different binding conformations. This picture is supported by the average donor–acceptor separations as estimated from time-resolved and steady-state measurements. Electrostatic interactions dominate at low concentrations and in mixed solvents. PMID:15282375

Simulation of the Regional Ground-Water-Flow System and Ground-Water/Surface-Water Interaction in the Rock River Basin, Wisconsin

USGS Publications Warehouse

Juckem, Paul F.

2009-01-01

A regional, two-dimensional, areal ground-water-flow model was developed to simulate the ground-water-flow system and ground-water/surface-water interaction in the Rock River Basin. The model was developed by the U.S. Geological Survey (USGS), in cooperation with the Rock River Coalition. The objectives of the regional model were to improve understanding of the ground-water-flow system and to develop a tool suitable for evaluating the effects of potential regional water-management programs. The computer code GFLOW was used because of the ease with which the model can simulate ground-water/surface-water interactions, provide a framework for simulating regional ground-water-flow systems, and be refined in a stepwise fashion to incorporate new data and simulate ground-water-flow patterns at multiple scales. The ground-water-flow model described in this report simulates the major hydrogeologic features of the modeled area, including bedrock and surficial aquifers, ground-water/surface-water interactions, and ground-water withdrawals from high-capacity wells. The steady-state model treats the ground-water-flow system as a single layer with hydraulic conductivity and base elevation zones that reflect the distribution of lithologic groups above the Precambrian bedrock and a regionally significant confining unit, the Maquoketa Formation. In the eastern part of the Basin where the shale-rich Maquoketa Formation is present, deep ground-water flow in the sandstone aquifer below the Maquoketa Formation was not simulated directly, but flow into this aquifer was incorporated into the GFLOW model from previous work in southeastern Wisconsin. Recharge was constrained primarily by stream base-flow estimates and was applied uniformly within zones guided by regional infiltration estimates for soils. The model includes average ground-water withdrawals from 1997 to 2006 for municipal wells and from 1997 to 2005 for high-capacity irrigation, industrial, and commercial wells. In addition, the model routes tributary base flow through the river network to the Rock River. The parameter-estimation code PEST was linked to the GFLOW model to select the combination of parameter values best able to match more than 8,000 water-level measurements and base-flow estimates at 9 streamgages. Results from the calibrated GFLOW model show simulated (1) ground-water-flow directions, (2) ground-water/surface-water interactions, as depicted in a map of gaining and losing river and lake sections, (3) ground-water contributing areas for selected tributary rivers, and (4) areas of relatively local ground water captured by rivers. Ground-water flow patterns are controlled primarily by river geometries, with most river sections gaining water from the ground-water-flow system; losing sections are most common on the downgradient shore of lakes and reservoirs or near major pumping centers. Ground-water contributing areas to tributary rivers generally coincide with surface watersheds; however the locations of ground-water divides are controlled by the water table, whereas surface-water divides are controlled by surface topography. Finally, areas of relatively local ground water captured by rivers generally extend upgradient from rivers but are modified by the regional flow pattern, such that these areas tend to shift toward regional ground-water divides for relatively small rivers. It is important to recognize the limitations of this regional-scale model. Heterogeneities in subsurface properties and in recharge rates are considered only at a very broad scale (miles to tens of miles). No account is taken of vertical variations in properties or pumping rates, and no provision is made to account for stacked ground-water-flow systems that have different flow patterns at different depths. Small-scale flow systems (hundreds to thousands of feet) associated with minor water bodies are not considered; as a result, the model is not currently designed for simulating site-specifi

Watershed Scale Analysis of Groundwater Surface Water Interactions and Its Application to Conjunctive Management under Climatic and Anthropogenic Stresses over the US Sunbelt

NASA Astrophysics Data System (ADS)

Seo, Seung Beom

Although water is one of the most essential natural resources, human activities have been exerting pressure on water resources. In order to reduce these stresses on water resources, two key issues threatening water resources sustainability - interaction between surface water and groundwater resources and groundwater withdrawal impacts of streamflow depletion - were investigated in this study. First, a systematic decomposition procedure was proposed for quantifying the errors arising from various sources in the model chain in projecting the changes in hydrologic attributes using near-term climate change projections. Apart from the unexplained changes by GCMs, the process of customizing GCM projections to watershed scale through a model chain - spatial downscaling, temporal disaggregation and hydrologic model - also introduces errors, thereby limiting the ability to explain the observed changes in hydrologic variability. Towards this, we first propose metrics for quantifying the errors arising from different steps in the model chain in explaining the observed changes in hydrologic variables (streamflow, groundwater). The proposed metrics are then evaluated using a detailed retrospective analyses in projecting the changes in streamflow and groundwater attributes in four target basins that span across a diverse hydroclimatic regimes over the US Sunbelt. Our analyses focused on quantifying the dominant sources of errors in projecting the changes in eight hydrologic variables - mean and variability of seasonal streamflow, mean and variability of 3-day peak seasonal streamflow, mean and variability of 7-day low seasonal streamflow and mean and standard deviation of groundwater depth - over four target basins using an Penn state Integrated Hydrologic Model (PIHM) between the period 1956-1980 and 1981-2005. Retrospective analyses show that small/humid (large/arid) basins show increased (reduced) uncertainty in projecting the changes in hydrologic attributes. Further, changes in error due to GCMs primarily account for the unexplained changes in mean and variability of seasonal streamflow. On the other hand, the changes in error due to temporal disaggregation and hydrologic model account for the inability to explain the observed changes in mean and variability of seasonal extremes. Thus, the proposed metrics provide insights on how the error in explaining the observed changes being propagated through the model under different hydroclimatic regimes. To understand interaction between surface water and groundwater resources, transient pumping impacts on streamflow and groundwater level were analyzed by imposing shortterm pumping scenarios under historic drought conditions. Since surface water and groundwater systems are fully coupled and integrated systems, increased groundwater withdrawal during drought may reduce baseflow into the stream and prolong both systems' recovery from drought. Towards this, we proposed an uncertainty framework to understand the resiliency of groundwater and surface water systems using a fully-coupled hydrologic model under transient pumping. Using this framework, we quantified the restoration time of surface water and groundwater systems and also estimated the changes in the state variables after pumping. Groundwater pumping impacts over the watershed were also analyzed under different pumping volumes and different potential climate scenarios. Our analyses show that groundwater restoration time is more sensitive to changes in pumping volumes as opposed to changes in climate. After the cessation of pumping, streamflow recovers quickly in comparison to groundwater. Pumping impacts on other state variables are also discussed. Given that surface water and groundwater are inter-connected, optimal management of the both resources should be considered to improve the watershed resiliency under drought. Subsequently, conjunctive use of surface water and groundwater has been considered as an effective approach to mitigate water shortage problems that are primarily caused by a drought. It is found that appropriate use of groundwater withdrawal was able to reduce water scarcity in surface water resources in drought condition. Besides, recovery time constraint was embedded in the management model so that trade-off between minimizing water scarcity and maximizing sustainability on groundwater was successfully addressed.

Dielectric Relaxation of Water and Water-Plasticized Biomolecules in Relation to Cellular Water Organization, Cytoplasmic Viscosity, and Desiccation Tolerance in Recalcitrant Seed Tissues1

PubMed Central

Sun, Wendell Q.

2000-01-01

To understand the relationship between the organization of cellular water, molecular interactions, and desiccation tolerance, dielectric behaviors of water and water-plasticized biomolecules in red oak (Quercus rubra) seeds were studied during dehydration. The thermally stimulated current study showed three dielectric dispersions: (a) the relaxation of loosely-bound water and small polar groups, (b) the relaxation of tightly-bound water, carbohydrate chains, large polar groups of macromolecules, and (c) the “freezing in” of molecular mobility (glassy state). Seven discrete hydration levels (water contents of 1.40, 0.55, 0.41, 0.31, 0.21, 0.13, and 0.08 g/g dry weight, corresponding to −1.5, −8, −11, −14, −24, −74, and −195 MPa, respectively) were identified according to the changes in thermodynamic and dielectric properties of water and water-plasticized biomolecules during dehydration. The implications of intracellular water organization for desiccation tolerance were discussed. Cytoplasmic viscosity increased exponentially at water content < 0.40 g/g dry weight, which was correlated with the great relaxation slowdown of water-plasticized biomolecules, supporting a role for viscosity in metabolic shutdown during dehydration. PMID:11080297

Effect of Soil Washing for Lead and Zinc Removal on Soil Hydraulic Properties

NASA Astrophysics Data System (ADS)

Kammerer, Gerhard; Zupanc, Vesna; Gluhar, Simon; Lestan, Domen

2017-04-01

Soil washing as a metal pollution remediation process, especially part with intensive mixing of the soil slurry and soil compression after de-watering, significantly deteriorates physical properties of soil compared to those of non-remediated soil. Furthermore, changed physical characteristics of remediated soil influence interaction of plant roots with soil system and affect soil water regime. Remediated soils showed significant differences to their original state in water retention properties and changed structure due to the influence of artificial structure created during remediation process. Disturbed and undisturbed soil samples of remediated and original soils were analyzed. We evaluated soil hydraulic properties as a possible constraint for re-establishing soil structure and soil fertility after the remediation procedure.

Impact of Asian Aerosols on Precipitation Over California: An Observational and Model Based Approach

NASA Technical Reports Server (NTRS)

Naeger, Aaron R.; Molthan, Andrew L.; Zavodsky, Bradley T.; Creamean, Jessie M.

2015-01-01

Dust and pollution emissions from Asia are often transported across the Pacific Ocean to over the western United States. Therefore, it is essential to fully understand the impact of these aerosols on clouds and precipitation forming over the eastern Pacific and western United States, especially during atmospheric river events that account for up to half of California's annual precipitation and can lead to widespread flooding. In order for numerical modeling simulations to accurately represent the present and future regional climate of the western United States, we must account for the aerosol-cloud-precipitation interactions associated with Asian dust and pollution aerosols. Therefore, we have constructed a detailed study utilizing multi-sensor satellite observations, NOAA-led field campaign measurements, and targeted numerical modeling studies where Asian aerosols interacted with cloud and precipitation processes over the western United States. In particular, we utilize aerosol optical depth retrievals from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS), NOAA Geostationary Operational Environmental Satellite (GOES-11), and Japan Meteorological Agency (JMA) Multi-functional Transport Satellite (MTSAT) to effectively detect and monitor the trans-Pacific transport of Asian dust and pollution. The aerosol optical depth (AOD) retrievals are used in assimilating the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) in order to provide the model with an accurate representation of the aerosol spatial distribution across the Pacific. We conduct WRF-Chem model simulations of several cold-season atmospheric river events that interacted with Asian aerosols and brought significant precipitation over California during February-March 2011 when the NOAA CalWater field campaign was ongoing. The CalWater field campaign consisted of aircraft and surface measurements of aerosol and precipitation processes that help extensively validate our WRF-Chem model simulations. After validating the capability of the WRF-Chem in realistically simulating the aerosol-cloud precipitation interactions, we conduct sensitivity studies where the AOD is doubled to diagnose whether an increasing concentration of Asian aerosols over the western United States will lead to further impacts on the cloud and precipitation processes over California. We also perform sensitivity studies where the aerosols will be partitioned into dust-only and pollution-only in order to separate the impacts of the differing Asian aerosol species. The results of our WRF-Chem model simulations aim to show that the trans-Pacific transport of Asian aerosols influence the precipitation associated with atmospheric river events that can ultimately impact the regional climate of the western United States. 1 University

Effects of fertilization and three years of throughfall reduction on leaf physiology of loblolly pine

Treesearch

Charles J. Pell; Lisa J. Samuelson

2016-01-01

Climate models project decreased soil water availability in the southeastern United States, which may impact loblolly pine (Pinus taeda L.) productivity. In conjunction with an interdisciplinary project known as PINEMAP, the objective of this study was to investigate the interactive effects of fertilization and a 30 percent reduction in throughfall on physiological...

Colors after the Storms

NASA Image and Video Library

2015-10-26

Damaging heavy rains fell on South Carolina in the southeastern United States at the beginning of October 2015. Much of that water had, by mid October, flowed into the Atlantic Ocean bringing with it heavy loads of sediment, nutrients, and dissolved organic material. The above VIIRS image shows the runoff as it interacts with ocean currents on October 15, 2015. Credit: NASA/Goddard/SuomiNPP/VIIRS via NASA's OceanColor

Coliform and metal contamination in Lago de Colina, a recreational water body in Chihuahua State, Mexico.

PubMed

Rubio-Arias, Hector; Rey, Nora I; Quintana, Rey M; Nevarez, G Virginia; Palacios, Oskar

2011-06-01

Lago de Colina (Colina Lake) is located about 180 km south of the city of Chihuahua (Mexico), and during the Semana Santa (Holy Week) vacation period its recreational use is high. The objective of this study was to quantify coliform and heavy metal levels in this water body before and after the Holy Week vacation period in 2010. Twenty sampling points were randomly selected and two water samples were collected at each point near the surface (0.30 m) and at 1 m depth. After the Holy Week vacation the same twenty points were sampled at the same depths. Therefore, a total 80 water samples were analyzed for fecal and total coliforms and levels of the following metals: Al, As, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Si and Zn. It was hypothesized that domestic tourism contaminated this water body, and as a consequence, could have a negative impact on visitor health. An analysis of variance (ANOVA) study was performed for each element and its interactions considering a factorial design where factor A was sample date and factor B was sample depth. Fecal coliforms were only detected at eight sampling points in the first week, but after Holy Week, both fecal and total coliforms were detected at most sampling points. The concentrations of Al, B, Na, Ni and Se were only statistically different for factor A. The levels of Cr, Cu, K and Mg was different for both date and depth, but the dual factor interaction was not significant. The amount of Ca and Zn was statistically different due to date, depth and their interaction. No significant differences were found for any factor or the interaction for the elements As, Fe and Mn. Because of the consistent results, it is concluded that local tourism is contaminating the recreational area of Colina Lake, Chihuahua, Mexico.

Coliform and Metal Contamination in Lago de Colina, a Recreational Water Body in Chihuahua State, Mexico

PubMed Central

Rubio-Arias, Hector; Rey, Nora I.; Quintana, Rey M.; Nevarez, G. Virginia; Palacios, Oskar

2011-01-01

Lago de Colina (Colina Lake) is located about 180 km south of the city of Chihuahua (Mexico), and during the Semana Santa (Holy Week) vacation period its recreational use is high. The objective of this study was to quantify coliform and heavy metal levels in this water body before and after the Holy Week vacation period in 2010. Twenty sampling points were randomly selected and two water samples were collected at each point near the surface (0.30 m) and at 1 m depth. After the Holy Week vacation the same twenty points were sampled at the same depths. Therefore, a total 80 water samples were analyzed for fecal and total coliforms and levels of the following metals: Al, As, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Si and Zn. It was hypothesized that domestic tourism contaminated this water body, and as a consequence, could have a negative impact on visitor health. An analysis of variance (ANOVA) study was performed for each element and its interactions considering a factorial design where factor A was sample date and factor B was sample depth. Fecal coliforms were only detected at eight sampling points in the first week, but after Holy Week, both fecal and total coliforms were detected at most sampling points. The concentrations of Al, B, Na, Ni and Se were only statistically different for factor A. The levels of Cr, Cu, K and Mg was different for both date and depth, but the dual factor interaction was not significant. The amount of Ca and Zn was statistically different due to date, depth and their interaction. No significant differences were found for any factor or the interaction for the elements As, Fe and Mn. Because of the consistent results, it is concluded that local tourism is contaminating the recreational area of Colina Lake, Chihuahua, Mexico. PMID:21776236

On the nature of the solvated electron in ice Ih.

PubMed

de Koning, Maurice; Fazzio, Adalberto; da Silva, Antônio José Roque; Antonelli, Alex

2016-02-14

The water-solvated excess electron (EE) is a key chemical agent whose hallmark signature, its asymmetric optical absorption spectrum, continues to be a topic of debate. While nearly all investigation has focused on the liquid-water solvent, the fact that the crystalline-water solvated EE shows a very similar visible absorption pattern has remained largely unexplored. Here, we present spin-polarized density-functional theory calculations subject to periodic boundary conditions of the interplay between an EE and a number of intrinsic lattice defects in ice Ih. Our results show that the optical absorption signatures in the presence of three unsaturated hydrogen bonds (HB) are very similar to those observed experimentally. Its low-energy side can be attributed to transitions between the EE ground state and a single localized excited level, in a picture that is different from that for the liquid solvent, where this portion has been associated with hydrogen-like s → p excitations. The blue tail, on the other hand, relates to transitions between the EE ground state and delocalized excited states, which is in line with the bound-to-continuum transition interpretations for the EE in liquid water. Finally, we find that, depending on the number of dangling HBs participating in the EE trap, its charge density may spontaneously break the spin degeneracy through exchange interactions with the surrounding electrons, displaying the many-electron quantum nature of the EE problem in ice Ih.

Theoretical and experimental studies of water interaction in acetate based ionic liquids.

PubMed

Shi, Wei; Damodaran, Krishnan; Nulwala, Hunaid B; Luebke, David R

2012-12-05

Water interactions in 1-ethyl-3-methylimidazolium acetate ([emim][CH(3)COO]) were studied utilizing classical and ab initio simulation methods. The self-diffusivities for water and the ionic liquid (IL) were studied experimentally using pulse field gradient NMR spectroscopy and correlated with computational results. Water forms hydrogen bonding networks with the ionic liquid, and depending on the concentration of water, there are profound effects on the self-diffusivities of the various species. Both simulation and experiments show that the self-diffusivities for species in the water-[emim][CH(3)COO] system exhibit minima at 40-50 mol% water. Water interaction with the [CH(3)COO](-) anion predominates over the water-water and water-cation interactions at most water concentrations. Simulations further indicate that decreasing water-[CH(3)COO](-) interaction will increase the IL and water self-diffusivities. Self-diffusivities in the water-IL systems are dependent upon the cation in a complex way. Water interactions with [P(4444)][CH(3)COO] are reduced compared to [emim][CH(3)COO]. The [P(4444)](+) cation is bulkier than the [emim](+) cation and has a smaller self-diffusivity, but when water was introduced to [P(4444)] [CH(3)COO], the water-[CH(3)COO](-) hydrogen bonding network in the [P(4444)][CH(3)COO] was much smaller than the one observed in [emim][CH(3)COO].

Enhancement of Thermodynamic Gas-Phase Acidity and Basicity of Water by Means of Secondary Interactions.

PubMed

Montero-Campillo, M Merced; Alkorta, Ibon; Elguero, Jose

2018-06-26

A series of A···water, B···water complexes (A = acid, B =base) are studied at the G4 level of theory to show that water acidity or basicity can be modulated by non-covalent interactions. Protic and non-protic acids interacting with water form hydrogen bonds or other kind of non-covalent interactions, respectively, that may dramatically change the acidity of water up to almost 360 kJ·mol-1 in terms of enthalpy. Similarly, hydrogen bonds responsible for the interaction between typical small nitrogen-containing Lewis bases and water can enhance the proton affinity of water by almost 300 kJ·mol-1. Our results reveal that these large enhancements are linearly related with the binding energy of the charged complexes, and are determined by the Lewis acid-base properties of the molecule involved in the interaction, allowing a quite precise modulation of the corresponding acid-base properties of water. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Supercooled and glassy water: Metastable liquid(s), amorphous solid(s), and a no-man’s land

PubMed Central

Handle, Philip H.; Sciortino, Francesco

2017-01-01

We review the recent research on supercooled and glassy water, focusing on the possible origins of its complex behavior. We stress the central role played by the strong directionality of the water–water interaction and by the competition between local energy, local entropy, and local density. In this context we discuss the phenomenon of polyamorphism (i.e., the existence of more than one disordered solid state), emphasizing both the role of the preparation protocols and the transformation between the different disordered ices. Finally, we present the ongoing debate on the possibility of linking polyamorphism with a liquid–liquid transition that could take place in the no-man’s land, the temperature–pressure window in which homogeneous nucleation prevents the investigation of water in its metastable liquid form. PMID:29133419

On the interaction of vortices and internal waves in the dead-water problem

NASA Astrophysics Data System (ADS)

Hester, Eric

2017-11-01

Dead water refers to a mysterious increase in resistance experienced by boats in density-stratified waters. The problem has been documented since ancient times, and studied scientifically for over a century. These investigations have revealed the role of internal waves in generating drag. However, analytical approaches neglect important vortex dynamics, which experiments fail to visualise. For the first time, we study the phenomenon using state-of-the-art numerical simulations. We reproduce the effect and show it is greatest in strongly nonlinear regimes poorly modelled by current theory. The most exciting development found a new trailing vortex coupled to the boat. This robust structure is consistent with sailors accounts, but has been missed in previous scientific studies. We expect these results to lead to actionable ways to mitigate dead water in the real world.

Physical solid-state properties and dissolution of sustained-release matrices of polyvinylacetate.

PubMed

Gonzalez Novoa, Gelsys Ananay; Heinämäki, Jyrki; Mirza, Sabir; Antikainen, Osmo; Colarte, Antonio Iraizoz; Paz, Alberto Suzarte; Yliruusi, Jouko

2005-02-01

Solid-state compatibility and in vitro dissolution of direct-compressed sustained-release matrices of polyvinylacetate (PVAc) and polyvinylpyrrolidone (PVP) containing ibuprofen as a model drug were studied. Polyvinylalcohol (PVA) was used as an alternative water-soluble polymer to PVP. Differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) were used for characterizing solid-state polymer-polymer and drug-polymer interactions. The mechanical treatment for preparing physical mixtures of polyvinyl polymers and the drug (i.e. simple blending or stressed cogrinding) was shown not to affect the physical state of the drug and the polymers. With the drug-polymer mixtures the endothermic effect due to drug melting was always evident, but a considerable modification of the melting point of the drug in physical binary mixtures (drug:PVP) was observed, suggesting some interaction between the two. On the other hand, the lack of a significant shift of the melting endothermic peak of the drug in physical tertiary drug-polymer mixtures revealed no evidence of solid-state interaction between the drug and the present polymers. Sustained-release dissolution profiles were achieved from the direct-compressed matrices made from powder mixtures of the drug and PVAc combined with PVP, and the proportion of PVAc in the mixture clearly altered the drug release profiles in vitro. The drug release from the present matrix systems is controlled by both diffusion of the drug through the hydrate matrix and the erosion of the matrix itself.

Modeling stream-groundwater interactions and associated groundwater salinization in an urban floodplain

NASA Astrophysics Data System (ADS)

Ledford, S. H.; Lautz, L.

2014-12-01

The salinization of freshwater in the Northeastern United States from road salt application is well documented by the observed long-term increases in chloride concentrations in groundwater over the last fifty years. However, the processes controlling exchange of chloride between surface water and groundwater have not been fully investigated, particularly in urban streams where stream-groundwater interactions can be reduced due to bank armoring and channelization. Our research builds on previous findings that showed the potential for an urban riparian floodplain to buffer seasonal changes in chloride concentrations in an urban stream, resulting in smaller annual ranges of chloride in areas with intact riparian floodplains. A reach of Meadowbrook Creek, in Syracuse, New York, that is disconnected from the groundwater had large seasonal shifts in chloride concentration, varying from 2173 mg/L Cl- in the winter to 161.2 mg/L Cl- in the summer. This is in contrast to a downstream reach of the stream that receives groundwater discharge from a riparian floodplain, where chloride concentrations ranged from 657.0 mg/L in the winter to 252.0 mg/L in the summer. We originally hypothesized that winter snowmelt events caused overbank flooding of saline surface water, which recharged the floodplain groundwater, causing salinization. This saline water was then slowly discharged as baseflow throughout the year and was replaced with freshwater overbank events in the summer. However, a three dimensional model of the floodplain created using Visual MODFLOW indicates that surface water-groundwater interactions, such as hyporheic exchange, may have a greater control on winter salt input than overbank events, while summer flooding recharges the aquifer with freshwater. The model was compared to riparian aquifer samples collected from May 2013 until June 2014 to qualitatively study the impact of different types of surface water-groundwater interactions (e.g. groundwater recharge and discharge, hyporheic interaction) on salt storage and to identify the mechanisms by which urban riparian floodplains buffer seasonal variability of stream chloride concentrations in urban systems impacted by road salt.

The effect of water absorption on the dielectric properties of polyethylene hexagonal boron nitride nanocomposites

NASA Astrophysics Data System (ADS)

Ayoob, Raed; Alhabill, Fuad N.; Andritsch, Thomas; Vaughan, Alun S.

2018-02-01

The effect of water absorption on the dielectric response of polyethylene/hexagonal boron nitride nanocomposites has been studied by dielectric spectroscopy. The nanocomposites have been prepared with hBN concentrations ranging from 2 wt% to 30 wt%. Fourier transform infrared spectroscopy and thermogravimetric analysis revealed a very small amount of hydroxyl groups on the surface of hBN. Mass loss measurements showed that the nanocomposites did not absorb any water under ambient and dry conditions while there was some water absorption under wet conditions. The dielectric spectroscopy results showed a broad relaxation peak, indicative of different states of water with water shells of different thickness, which moved to higher frequencies with increasing water content. However, the dielectric losses were significantly lower than the losses reported in the literature of nanocomposites under wet conditions. In addition, all the absorbed water was successfully removed under vacuum conditions which demonstrated that the interactions between the water and the nanocomposites were very weak, due to the hydrophobic nature of the hBN surface. This is a highly useful property, when considering these materials for applications in electrical insulation.

The role of reproductive plant traits and biotic interactions in the dynamics of semi-arid plant communities.

PubMed

Pueyo, Y; Kéfi, S; Díaz-Sierra, R; Alados, C L; Rietkerk, M

2010-12-01

The dynamics of semi-arid plant communities are determined by the interplay between competition and facilitation among plants. The sign and strength of these biotic interactions depend on plant traits. However, the relationships between plant traits and biotic interactions, and the consequences for plant communities are still poorly understood. Our objective here was to investigate, with a modelling approach, the role of plant reproductive traits on biotic interactions, and the consequences for processes such as plant succession and invasion. The dynamics of two plant types were modelled with a spatially-explicit integrodifferential model: (1) a plant with seed dispersal (colonizer of bare soil) and (2) a plant with local vegetative propagation (local competitor). Both plant types were involved in facilitation due to a local positive feedback between vegetation biomass and soil water availability, which promoted establishment and growth. Plants in the system also competed for limited water. The efficiency in water acquisition (dependent on reproductive and growth plant traits) determined which plant type dominated the community at the steady state. Facilitative interactions between plant types also played an important role in the community dynamics, promoting establishment in the driest conditions and recovery from low biomass. Plants with vegetative propagation took advantage of the ability of seed dispersers to establish on bare soil from a low initial biomass. Seed dispersers were good invaders, maintained high biomass at intermediate and high rainfall and showed a high ability in taking profit from the positive feedback originated by plants with vegetative propagation under the driest conditions. However, seed dispersers lost competitiveness with an increasing investment in fecundity. All together, our results showed that reproductive plant traits can affect the balance between facilitative and competitive interactions. Understanding this effect of plant traits on biotic interactions provides insights in processes such as plant succession and shrub encroachment. Copyright © 2010 Elsevier Inc. All rights reserved.

A quantum mechanical study of water adsorption on the (110) surfaces of rutile SnO₂ and TiO₂: investigating the effects of intermolecular interactions using hybrid-exchange density functional theory.

PubMed

Patel, M; Sanches, F F; Mallia, G; Harrison, N M

2014-10-21

Periodic hybrid-exchange density functional theory calculations are used to explore the first layer of water at model oxide surfaces, which is an important step for understanding the photocatalytic reactions involved in solar water splitting. By comparing the structure and properties of SnO2(110) and TiO2(110) surfaces in contact with water, the effects of structural and electronic differences on the water chemistry are examined. The dissociative adsorption mode at low coverage (1/7 ML) up to monolayer coverage (1 ML) on both SnO2 and TiO2(110) surfaces is analysed. To investigate further the intermolecular interactions between adjacent adsorbates, monolayer adsorption on each surface is explored in terms of binding energies and bond lengths. Analysis of the water adsorption geometry and energetics shows that the relative stability of water adsorption on SnO2(110) is governed largely by the strength of the chemisorption and hydrogen bonds at the surface of the adsorbate-substrate system. However on TiO2(110), a more complicated scenario of the first layer of water on its surface arises in which there is an interplay between chemisorption, hydrogen bonding and adsorbate-induced atomic displacements in the surface. Furthermore the projected density of states of each surface in contact with a mixture of adsorbed water molecules and adsorbed hydroxyls is presented and sheds some light on the nature of the crystalline chemical bonds as well as on why adsorbed water has often been reported to be unstable on rutile SnO2(110).

Diaminoethane adsorption and water substitution on hydrated TiO2: a thermochemical study based on first-principles calculations.

PubMed

Hémeryck, Anne; Motta, Alessandro; Swiatowska, Jolanta; Pereira-Nabais, Catarina; Marcus, Philippe; Costa, Dominique

2013-07-14

Epoxy-amines are used as structural adhesives deposited on Ti. The amine adhesion to a Ti surface depends highly on the surface state (oxidation, hydroxylation). Amines may adsorb above preadsorbed water molecules or substitute them to bind directly to surface Ti(4+) Lewis acid sites. The adsorption of a model amine molecule, diaminoethane (DAE), on a model surface, hydrated TiO2-anatase (101) surface, is investigated using Density Functional Theory including Dispersive forces (DFT-D) calculations. DAE adsorption and water substitution by DAE are exothermic processes and turn nearly isoenergetic at high coverage with adsorption-substitution energies around -0.3 eV (including dispersion forces and ZPE). Complementary ab initio molecular dynamics studies also suggest that the formation of an amine-water interaction induces water desorption from the surface at room temperature, a preliminary step towards the amine-Ti bond formation. An atomistic thermodynamic approach is developed to evaluate the interfacial free energy balance of both processes (adsorption and substitution). The main contributions to the energetic balance are dispersive interactions between molecules and the surface on the exergonic side, translational and rotational entropic contributions on the endergonic one. The substitution process is stabilized by 0.55 eV versus the adsorption one when free solvation, rotational and vibrational energies are considered. The main contribution to this free energy gain is due to water solvation. The calculations suggest that in toluene solvent with a water concentration of 10(-4) M or less, a full DAE layer replaces a preadsorbed water layer for a threshold concentration of DAE ≥ 0.1 M.

Hyperresolution Global Land Surface Modeling: Meeting a Grand Challenge for Monitoring Earth's Terrestrial Water

NASA Technical Reports Server (NTRS)

Wood, Eric F.; Roundy, Joshua K.; Troy, Tara J.; van Beek, L. P. H.; Bierkens, Marc F. P.; 4 Blyth, Eleanor; de Roo, Ad; Doell. Petra; Ek, Mike; Famiglietti, James;

Hyperresolution global land surface modeling: Meeting a grand challenge for monitoring Earth's terrestrial water

NASA Astrophysics Data System (ADS)

Wood, Eric F.; Roundy, Joshua K.; Troy, Tara J.; van Beek, L. P. H.; Bierkens, Marc F. P.; Blyth, Eleanor; de Roo, Ad; DöLl, Petra; Ek, Mike; Famiglietti, James; Gochis, David; van de Giesen, Nick; Houser, Paul; Jaffé, Peter R.; Kollet, Stefan; Lehner, Bernhard; Lettenmaier, Dennis P.; Peters-Lidard, Christa; Sivapalan, Murugesu; Sheffield, Justin; Wade, Andrew; Whitehead, Paul

2011-05-01

Monitoring Earth's terrestrial water conditions is critically important to many hydrological applications such as global food production; assessing water resources sustainability; and flood, drought, and climate change prediction. These needs have motivated the development of pilot monitoring and prediction systems for terrestrial hydrologic and vegetative states, but to date only at the rather coarse spatial resolutions (˜10-100 km) over continental to global domains. Adequately addressing critical water cycle science questions and applications requires systems that are implemented globally at much higher resolutions, on the order of 1 km, resolutions referred to as hyperresolution in the context of global land surface models. This opinion paper sets forth the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles. We discuss six major challenges in developing a system: improved representation of surface-subsurface interactions due to fine-scale topography and vegetation; improved representation of land-atmospheric interactions and resulting spatial information on soil moisture and evapotranspiration; inclusion of water quality as part of the biogeochemical cycle; representation of human impacts from water management; utilizing massively parallel computer systems and recent computational advances in solving hyperresolution models that will have up to 109 unknowns; and developing the required in situ and remote sensing global data sets. We deem the development of a global hyperresolution model for monitoring the terrestrial water, energy, and biogeochemical cycles a "grand challenge" to the community, and we call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort.

Ultramafic Terranes and Associated Springs as Analogs for Mars and Early Earth

NASA Technical Reports Server (NTRS)

Blake, David; Schulte, Mitch; Cullings, Ken; DeVincezi, D. (Technical Monitor)

2002-01-01

Putative extinct or extant Martian organisms, like their terrestrial counterparts, must adopt metabolic strategies based on the environments in which they live. In order for organisms to derive metabolic energy from the natural environment (Martian or terrestrial), a state of thermodynamic disequilibrium must exist. The most widespread environment of chemical disequilibrium on present-day Earth results from the interaction of mafic rocks of the ocean crust with liquid water. Such environments were even more pervasive and important on the Archean Earth due to increased geothermal heat flow and the absence of widespread continental crust formation. The composition of the lower crust and upper mantle of the Earth is essentially the-same as that of Mars, and the early histories of these two planets are similar. It follows that a knowledge of the mineralogy, water-rock chemistry and microbial ecology of Earth's oceanic crust could be of great value in devising a search strategy for evidence of past or present life on Mars. In some tectonic regimes, cross-sections of lower oceanic crust and upper mantle are exposed on land as so-called "ophiolite suites." Such is the case in the state of California (USA) as a result of its location adjacent to active plate margins. These mafic and ultramafic rocks contain numerous springs that offer an easily accessible field laboratory for studying water/rock interactions and the microbial communities that are supported by the resulting geochemical energy. A preliminary screen of Archaean biodiversity was conducted in a cold spring located in a presently serpentinizing ultramafic terrane. PCR and phylogenetic analysis of partial 16s rRNA, sequences were performed on water and sediment samples. Archaea of recent phylogenetic origin were detected with sequences nearly identical to those of organisms living in ultra-high pH lakes of Africa.

Ecophysiological response to seasonal variations in water availability in the arborescent, endemic plant Vellozia gigantea.

PubMed

Morales, Melanie; Garcia, Queila S; Munné-Bosch, Sergi

2015-03-01

The physiological response of plants growing in their natural habitat is strongly determined by seasonal variations in environmental conditions and the interaction of abiotic and biotic stresses. Here, leaf water and nutrient contents, changes in cellular redox state and endogenous levels of stress-related phytohormones (abscisic acid (ABA), salicylic acid and jasmonates) were examined during the rainy and dry season in Vellozia gigantea, an endemic species growing at high elevations in the rupestrian fields of the Espinhaço Range in Brazil. Enhanced stomatal closure and increased ABA levels during the dry season were associated with an efficient control of leaf water content. Moreover, reductions in 12-oxo-phytodienoic acid (OPDA) levels during the dry season were observed, while levels of other jasmonates, such as jasmonic acid and jasmonoyl-isoleucine, were not affected. Changes in ABA and OPDA levels correlated with endogenous concentrations of iron and silicon, hydrogen peroxide, and vitamin E, thus indicating complex interactions between water and nutrient contents, changes in cellular redox state and endogenous hormone concentrations. Results also suggested crosstalk between activation of mechanisms for drought stress tolerance (as mediated by ABA) and biotic stress resistance (mediated by jasmonates), in which vitamin E levels may serve as a control point. It is concluded that, aside from a tight ABA-associated regulation of stomatal closure during the dry season, crosstalk between activation of abiotic and biotic defences, and nutrient accumulation in leaves may be important modulators of plant stress responses in plants growing in their natural habitat. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effects of lengthscales and attractions on the collapse of hydrophobic polymers in water

PubMed Central

Athawale, Manoj V.; Goel, Gaurav; Ghosh, Tuhin; Truskett, Thomas M.; Garde, Shekhar

2007-01-01

We present results from extensive molecular dynamics simulations of collapse transitions of hydrophobic polymers in explicit water focused on understanding effects of lengthscale of the hydrophobic surface and of attractive interactions on folding. Hydrophobic polymers display parabolic, protein-like, temperature-dependent free energy of unfolding. Folded states of small attractive polymers are marginally stable at 300 K and can be unfolded by heating or cooling. Increasing the lengthscale or decreasing the polymer–water attractions stabilizes folded states significantly, the former dominated by the hydration contribution. That hydration contribution can be described by the surface tension model, ΔG = γ(T)ΔA, where the surface tension, γ, is lengthscale-dependent and decreases monotonically with temperature. The resulting variation of the hydration entropy with polymer lengthscale is consistent with theoretical predictions of Huang and Chandler [Huang DM, Chandler D (2000) Proc Natl Acad Sci USA 97:8324–8327] that explain the blurring of entropy convergence observed in protein folding thermodynamics. Analysis of water structure shows that the polymer–water hydrophobic interface is soft and weakly dewetted, and is characterized by enhanced interfacial density fluctuations. Formation of this interface, which induces polymer folding, is strongly opposed by enthalpy and favored by entropy, similar to the vapor–liquid interface. PMID:17215352

Detecting and monitoring water stress states in maize crops using spectral ratios obtained in the photosynthetic domain

NASA Astrophysics Data System (ADS)

Baranoski, Gladimir V. G.; Van Leeuwen, Spencer R.

2017-07-01

The reliable detection and monitoring of changes in the water status of crops composed of plants like maize, a highly adaptable C4 species in large demand for both food and biofuel production, are longstanding remote sensing goals. Existing procedures employed to achieve these goals rely predominantly on the spectral signatures of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. It has been suggested that such procedures could be implemented using subsurface reflectance to transmittance ratios obtained in the visible (photosynthetic) domain with the assistance of polarization devices. However, the experiments leading to this proposition were performed on detached maize leaves, which were not influenced by the whole (living) plant's adaptation mechanisms to water stress. In this work, we employ predictive simulations of light-leaf interactions in the photosynthetic domain to demonstrate that the living specimens' physiological responses to dehydration stress should be taken into account in this context. Our findings also indicate that a reflectance to transmittance ratio obtained in the photosynthetic domain at a lower angle of incidence without the use of polarization devices may represent a cost-effective alternative for the assessment of water stress states in maize crops.

Ion specific effects: decoupling ion-ion and ion-water interactions

PubMed Central

Song, Jinsuk; Kang, Tae Hui; Kim, Mahn Won; Han, Songi

2015-01-01

Ion-specific effects in aqueous solution, known as the Hofmeister effect is prevalent in diverse systems ranging from pure ionic to complex protein solutions. The objective of this paper is to explicitly demonstrate how complex ion-ion and ion-water interactions manifest themselves in the Hofmeister effects, based on a series of recent experimental observation. These effects are not considered in the classical description of ion effects, such as the Deryaguin-Landau-Verwey-Overbeek (DLVO) theory that, likely for that reason, fail to describe the origin of the phenomenological Hofmeister effect. However, given that models considering the basic forces of electrostatic and van der Waals interactions can offer rationalization for the core experimental observations, a universal interaction model stands a chance to be developed. In this perspective, we separately derive the contribution from ion-ion electrostatic interaction and ion-water interaction from second harmonic generation (SHG) data at the air-ion solution interface, which yields an estimate of ion-water interactions in solution. Hofmeister ion effects observed on biological solutes in solution should be similarly influenced by contributions from ion-ion and ion-water interactions, where the same ion-water interaction parameters derived from SHG data at the air-ion solution interface could be applicable. A key experimental data set available from solution systems to probe ion-water interaction is the modulation of water diffusion dynamics near ions in bulk ion solution, as well as near biological liposome surfaces. It is obtained from Overhauser dynamic nuclear polarization (ODNP), a nuclear magnetic resonance (NMR) relaxometry technique. The surface water diffusivity is influenced by the contribution from ion-water interactions, both from localized surface charges and adsorbed ions, although the relative contribution of the former is larger on liposome surfaces. In this perspective, ion-water interaction energy values derived from experimental data for various ions are compared with theoretical values in the literature. Ultimately, quantifying ion-induced changes in surface energy for the purpose of developing valid theoretical models for ion-water interaction, will be critical to rationalizing the Hofmeister effect. PMID:25761273

State Dependent Valuation: The Effect of Deprivation on Risk Preferences

PubMed Central

Levy, Dino J.; Thavikulwat, Amalie C.; Glimcher, Paul W.

2013-01-01

The internal state of an organism affects its choices. Previous studies in various non-human animals have demonstrated a complex, and in some cases non-monotonic, interaction between internal state and risk preferences. Our aim was to examine the systematic effects of deprivation on human decision-making across various reward types. Using both a non-parametric approach and a classical economic analysis, we asked whether the risk attitudes of human subjects towards money, food and water rewards would change as a function of their internal metabolic state. Our findings replicate some previous work suggesting that, on average, humans become more risk tolerant in their monetary decisions, as they get hungry. However, our specific approach allowed us to make two novel observations about the complex interaction between internal state and risk preferences. First, we found that the change in risk attitude induced by food deprivation is a general phenomenon, affecting attitudes towards both monetary and consumable rewards. But much more importantly, our data indicate that rather than each subject becoming more risk tolerant as previously hypothesized based on averaging across subjects, we found that as a population of human subjects becomes food deprived the heterogeneity of their risk attitudes collapses towards a fixed point. Thus subjects who show high-risk aversion while satiated shift towards moderate risk aversion when deprived but subjects who are risk tolerant become more risk averse. These findings demonstrate a more complicated interaction between internal state and risk preferences and raise some interesting implications for both day-to-day decisions and financial market structures. PMID:23358126

State dependent valuation: the effect of deprivation on risk preferences.

PubMed

Levy, Dino J; Thavikulwat, Amalie C; Glimcher, Paul W

2013-01-01

The internal state of an organism affects its choices. Previous studies in various non-human animals have demonstrated a complex, and in some cases non-monotonic, interaction between internal state and risk preferences. Our aim was to examine the systematic effects of deprivation on human decision-making across various reward types. Using both a non-parametric approach and a classical economic analysis, we asked whether the risk attitudes of human subjects towards money, food and water rewards would change as a function of their internal metabolic state. Our findings replicate some previous work suggesting that, on average, humans become more risk tolerant in their monetary decisions, as they get hungry. However, our specific approach allowed us to make two novel observations about the complex interaction between internal state and risk preferences. First, we found that the change in risk attitude induced by food deprivation is a general phenomenon, affecting attitudes towards both monetary and consumable rewards. But much more importantly, our data indicate that rather than each subject becoming more risk tolerant as previously hypothesized based on averaging across subjects, we found that as a population of human subjects becomes food deprived the heterogeneity of their risk attitudes collapses towards a fixed point. Thus subjects who show high-risk aversion while satiated shift towards moderate risk aversion when deprived but subjects who are risk tolerant become more risk averse. These findings demonstrate a more complicated interaction between internal state and risk preferences and raise some interesting implications for both day-to-day decisions and financial market structures.

Ground and excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters: Insight into the electronic structure of the [Fe(H2O)6]2+ – [Fe(H2O)6]3+ complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miliordos, Evangelos; Xantheas, Sotiris S.

We report the ground and low lying electronically excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters using multi-configuration electronic structure theory. In particular, we have constructed the Potential Energy Curves (PECs) with respect to the iron-oxygen distance when removing all water ligands at the same time from the cluster minima and established their correlation to the long range dissociation channels. Due to the fact that both the second and third ionization potentials of iron are larger than the one for water, the ground state products asymptotically correlate with dissociation channels that are repulsive in nature at large separations as theymore » contain at least one H2O+ fragment and a positive metal center. The most stable equilibrium structures emanate – via intersections and/or avoided crossings – from the channels consisting of the lowest electronic states of Fe2+(5D; 3d6) or Fe3+(6S; 3d5) and six neutral water molecules. Upon hydration, the ground state of Fe2+(H2O)6 is a triply (5Tg) degenerate one with the doubly (5Eg) degenerate state lying slightly higher in energy. Similarly, Fe3+(H2O)6 has a ground state of 6Ag symmetry under Th symmetry. We furthermore examine a multitude of electronically excited states of many possible spin multiplicities, and report the optimized geometries for several selected states. The PECs for those cases are characterized by a high density of states. Focusing on the ground and the first few excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters, we studied their mutual interaction in the gas phase. We obtained the optimal geometries of the Fe2+(H2O)6 – Fe3+(H2O)6 gas phase complex for different Fe–Fe distances. For distances shorter than 6.0 Å, the water molecules in the respective first solvation shells located between the two metal centers were found to interact via weak hydrogen bonds. We examined a total of ten electronic states for this complex, including those corresponding to the electron transfer (ET) from the ferrous to the ferric ion. The ET process is discussed and a possible path via a quasi-symmetric transition state is suggested. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.« less

An analytical derivation of MC-SCF vibrational wave functions for the quantum dynamical simulation of multiple proton transfer reactions: Initial application to protonated water chains

NASA Astrophysics Data System (ADS)

Drukker, Karen; Hammes-Schiffer, Sharon

1997-07-01

This paper presents an analytical derivation of a multiconfigurational self-consistent-field (MC-SCF) solution of the time-independent Schrödinger equation for nuclear motion (i.e. vibrational modes). This variational MC-SCF method is designed for the mixed quantum/classical molecular dynamics simulation of multiple proton transfer reactions, where the transferring protons are treated quantum mechanically while the remaining degrees of freedom are treated classically. This paper presents a proof that the Hellmann-Feynman forces on the classical degrees of freedom are identical to the exact forces (i.e. the Pulay corrections vanish) when this MC-SCF method is used with an appropriate choice of basis functions. This new MC-SCF method is applied to multiple proton transfer in a protonated chain of three hydrogen-bonded water molecules. The ground state and the first three excited state energies and the ground state forces agree well with full configuration interaction calculations. Sample trajectories are obtained using adiabatic molecular dynamics methods, and nonadiabatic effects are found to be insignificant for these sample trajectories. The accuracy of the excited states will enable this MC-SCF method to be used in conjunction with nonadiabatic molecular dynamics methods. This application differs from previous work in that it is a real-time quantum dynamical nonequilibrium simulation of multiple proton transfer in a chain of water molecules.

Using stable isotopes to resolve eco-hydrological dynamics of soil-plant-atmosphere feedbacks

NASA Astrophysics Data System (ADS)

Dubbert, M.; Piayda, A.; Kübert, A.; Cuntz, M.; Werner, C.

2016-12-01

Water is the main driver of ecosystem productivity in most terrestrial ecosystems worldwide. Extreme events are predicted to increase in frequency in many regions and dynamic responses in soil-vegetation-atmosphere feedbacks play a privotal role in understanding the ecosystem water balance and functioning. In this regard, more interdisciplinary approaches, bridging hydrology, ecophysiology and atmospheric sciences are needed and particularly water stable isotopes are a powerful tracer of water transfer in soils and at the soil-plant interface (Werner and Dubbert 2016). Here, we present observations 2 different ecosystems. Water fluxes, atmospheric concentrations and their isotopic compositions were measured using laser spectroscopy. Soil moisture and its isotopic composition in several depths as well as further water sources in the ecosystem were monitored throughout the year. Using these isotopic approaches we disentangled soil-plant-atmosphere feedback processes controlling the ecosystem water cycle including vegetation effects on soil water infiltration and distribution, event water use of vegetation and soil fluxes, vegetational soil water uptake depths plasticity and partitioning of ecosystem water fluxes. In this regard, we review current strategies of ET partitioning and highlight pitfalls in the presented strategies (Dubbert et al. 2013, Dubbert et al.2014a). We demonstrate that vegetation strongly influenced water cycling, altering infiltration and distribution of precipitation. In conclusion, application of stable water isotope tracers delivers a process based understanding of interactions between soil, understorey and trees governing ecosystem water cycling necessary for prediction of climate change impact on ecosystem productivity and vulnerability. ReferencesDubbert, M. et al. (2013): Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. Journal of Hydrology Dubbert, M. et al. (2014a): Oxygen isotope signatures of transpired water vapor: the role of isotopic non-steady-state transpiration under natural conditions. New Phytologist. Werner, C. and Dubbert, M. (2016): Resolving rapid dynamics of soil-plant-atmosphere interactions. New Phytologist.

Mediating Water Temperature Increases Due to Livestock and Global Change in High Elevation Meadow Streams of the Golden Trout Wilderness

PubMed Central

Nusslé, Sébastien; Matthews, Kathleen R.; Carlson, Stephanie M.

2015-01-01

Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two “resting” meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a “resting” state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change. PMID:26565706

Mediating Water Temperature Increases Due to Livestock and Global Change in High Elevation Meadow Streams of the Golden Trout Wilderness.

PubMed

Nusslé, Sébastien; Matthews, Kathleen R; Carlson, Stephanie M

2015-01-01

Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two "resting" meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a "resting" state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

Entrainment and cloud evaporation deduced from the stable isotope chemistry of clouds during ORACLES

NASA Astrophysics Data System (ADS)

Noone, D.; Henze, D.; Rainwater, B.; Toohey, D. W.

2017-12-01

The magnitude of the influence of biomass burning aerosols on cloud and rain processes is controlled by a series of processes which are difficult to measure directly. A consequence of this limitation is the emergence of significant uncertainty in the representation of cloud-aerosol interactions in models and the resulting cloud radiative forcing. Interaction between cloud and the regional atmosphere causes evaporation, and the rate of evaporation at cloud top is controlled in part by entrainment of air from above which exposes saturated cloud air to drier conditions. Similarly, the size of cloud droplets also controls evaporation rates, which in turn is linked to the abundance of condensation nuclei. To quantify the dependence of cloud properties on biomass burning aerosols the dynamic relationship between evaporation, drop size and entrainment on aerosol state, is evaluated for stratiform clouds in the southeast Atlantic Ocean. These clouds are seasonally exposed to biomass burning plumes from agricultural fires in southern Africa. Measurements of the stable isotope ratios of cloud water and total water are used to deduce the disequilibrium responsible for evaporation within clouds. Disequilibrium is identified by the relationship between hydrogen and oxygen isotope ratios of water vapor and cloud water in and near clouds. To obtain the needed information, a custom-built, dual inlet system was deployed alongside isotopic gas analyzers on the NASA Orion aircraft as part of the Observations of Aerosols above Clouds and their Interactions (ORACLES) campaign. The sampling system obtains both total water and cloud liquid content for the population of droplets above 7 micrometer diameter. The thermodynamic modeling required to convert the observed equilibrium and kinetic isotopic is linked to evaporation and entrainment is described, and the performance of the measurement system is discussed.

Ecosystem variability in the offshore northeastern Chukchi Sea

NASA Astrophysics Data System (ADS)

Blanchard, Arny L.; Day, Robert H.; Gall, Adrian E.; Aerts, Lisanne A. M.; Delarue, Julien; Dobbins, Elizabeth L.; Hopcroft, Russell R.; Questel, Jennifer M.; Weingartner, Thomas J.; Wisdom, Sheyna S.

2017-12-01

Understanding influences of cumulative effects from multiple stressors in marine ecosystems requires an understanding of the sources for and scales of variability. A multidisciplinary ecosystem study in the offshore northeastern Chukchi Sea during 2008-2013 investigated the variability of the study area's two adjacent sub-ecosystems: a pelagic system influenced by interannual and/or seasonal temporal variation at large, oceanographic (regional) scales, and a benthic-associated system more influenced by small-scale spatial variations. Variability in zooplankton communities reflected interannual oceanographic differences in waters advected northward from the Bering Sea, whereas variation in benthic communities was associated with seafloor and bottom-water characteristics. Variations in the planktivorous seabird community were correlated with prey distributions, whereas interaction effects in ANOVA for walruses were related to declines of sea-ice. Long-term shifts in seabird distributions were also related to changes in sea-ice distributions that led to more open water. Although characteristics of the lower trophic-level animals within sub-ecosystems result from oceanographic variations and interactions with seafloor topography, distributions of apex predators were related to sea-ice as a feeding platform (walruses) or to its absence (i.e., open water) for feeding (seabirds). The stability of prey resources appears to be a key factor in mediating predator interactions with other ocean characteristics. Seabirds reliant on highly-variable zooplankton prey show long-term changes as open water increases, whereas walruses taking benthic prey in biomass hotspots respond to sea-ice changes in the short-term. A better understanding of how variability scales up from prey to predators and how prey resource stability (including how critical prey respond to environmental changes over space and time) might be altered by climate and anthropogenic stressors is essential to predicting the future state of both the Chukchi and other arctic systems.

Water's Interfacial Hydrogen Bonding Structure Reveals the Effective Strength of Surface-Water Interactions.

PubMed

Shin, Sucheol; Willard, Adam P

2018-06-05

We combine all-atom molecular dynamics simulations with a mean field model of interfacial hydrogen bonding to analyze the effect of surface-water interactions on the structural and energetic properties of the liquid water interface. We show that the molecular structure of water at a weakly interacting ( i.e., hydrophobic) surface is resistant to change unless the strength of surface-water interactions are above a certain threshold. We find that below this threshold water's interfacial structure is homogeneous and insensitive to the details of the disordered surface, however, above this threshold water's interfacial structure is heterogeneous. Despite this heterogeneity, we demonstrate that the equilibrium distribution of molecular orientations can be used to quantify the energetic component of the surface-water interactions that contribute specifically to modifying the interfacial hydrogen bonding network. We identify this specific energetic component as a new measure of hydrophilicity, which we refer to as the intrinsic hydropathy.

Cellulosic biofuels from crop residue and groundwater extraction in the US Plains: the case of Nebraska.

PubMed

Sesmero, Juan P

2014-11-01

This study develops a model of crop residue (i.e. stover) supply and derived demand for irrigation water accounting for non-linear effects of soil organic matter on soil's water holding capacity. The model is calibrated for typical conditions in central Nebraska, United States, and identifies potential interactions between water and biofuel policies. The price offered for feedstock by a cost-minimizing plant facing that stover supply response is calculated. Results indicate that as biofuel production volumes increase, soil carbon depletion per unit of biofuel produced decreases. Consumption of groundwater per unit of biofuel produced first decreases and then increases (after a threshold of 363 dam(3) of biofuels per year) due to plants' increased reliance on the extensive margin for additional biomass. The analysis reveals a tension between biofuel and water policies. As biofuel production raises the economic benefits of relaxing water conservation policies (measured by the "shadow price" of water) increase. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cold Water Vapor in the Barnard 5 Molecular Cloud

NASA Technical Reports Server (NTRS)

Wirstrom, E. S.; Charnley, S. B.; Persson, C. M.; Buckle, J. V.; Cordiner, M. A.; Takakuwa, S.

2014-01-01

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold ((is) approximately 10 K) water vapor has been detected-L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work-likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

Water clustering in glassy polymers.

PubMed

Davis, Eric M; Elabd, Yossef A

2013-09-12

In this study, water solubility and water clustering in several glassy polymers, including poly(methyl methacrylate) (PMMA), poly(styrene) (PS), and poly(vinylpyrrolidone) (PVP), were measured using both quartz spring microbalance (QSM) and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Specifically, QSM was used to determine water solubility, while FTIR-ATR spectroscopy provided a direct, molecular-level measurement of water clustering. The Flory-Huggins theory was employed to obtain a measure of water-polymer interaction and water solubility, through both prediction and regression, where the theory failed to predict water solubility in both PMMA and PVP. Furthermore, a comparison of water clustering between direct FTIR-ATR spectroscopy measurements and predictions from the Zimm-Lundberg clustering analysis produced contradictory results. The failure of the Flory-Huggins theory and Zimm-Lundberg clustering analysis to describe water solubility and water clustering, respectively, in these glassy polymers is in part due to the equilibrium constraints under which these models are derived in contrast to the nonequilibrium state of glassy polymers. Additionally, FTIR-ATR spectroscopy results were compared to temperature-dependent diffusivity data, where a correlation between the activation energy for diffusion and the measured water clustering was observed.

Mechanisms of protein stabilization and prevention of protein aggregation by glycerol.

PubMed

Vagenende, Vincent; Yap, Miranda G S; Trout, Bernhardt L

2009-11-24

The stability of proteins in aqueous solution is routinely enhanced by cosolvents such as glycerol. Glycerol is known to shift the native protein ensemble to more compact states. Glycerol also inhibits protein aggregation during the refolding of many proteins. However, mechanistic insight into protein stabilization and prevention of protein aggregation by glycerol is still lacking. In this study, we derive mechanisms of glycerol-induced protein stabilization by combining the thermodynamic framework of preferential interactions with molecular-level insight into solvent-protein interactions gained from molecular simulations. Contrary to the common conception that preferential hydration of proteins in polyol/water mixtures is determined by the molecular size of the polyol and the surface area of the protein, we present evidence that preferential hydration of proteins in glycerol/water mixtures mainly originates from electrostatic interactions that induce orientations of glycerol molecules at the protein surface such that glycerol is further excluded. These interactions shift the native protein toward more compact conformations. Moreover, glycerol preferentially interacts with large patches of contiguous hydrophobicity where glycerol acts as an amphiphilic interface between the hydrophobic surface and the polar solvent. Accordingly, we propose that glycerol prevents protein aggregation by inhibiting protein unfolding and by stabilizing aggregation-prone intermediates through preferential interactions with hydrophobic surface regions that favor amphiphilic interface orientations of glycerol. These mechanisms agree well with experimental data available in the literature, and we discuss the extent to which these mechanisms apply to other cosolvents, including polyols, arginine, and urea.

Replica-exchange molecular dynamics simulations of cellulose solvated in water and in the ionic liquid 1-butyl-3-methylimidazolium chloride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mostofian, Barmak; Cheng, Xiaolin; Smith, Jeremy C.

2014-09-02

Ionic liquids have become a popular solvent for cellulose pretreatment in biorefineries due to their efficiency in dissolution and their reusability. Understanding the interactions between cations, anions, and cellulose is key to the development of better solvents and the improvement of pretreatment conditions. While previous studies described the interactions between ionic liquids and cellulose fibers, shedding light on the initial stages of the cellulose dissolution process, we study the end state of that process by exploring the structure and dynamics of a single cellulose decamer solvated in 1-butyl-3-methyl-imidazolium chloride (BmimCl) and in water using replica-exchange molecular dynamics. In both solvents,more » global structural features of the cellulose chain are similar. However, analyses of local structural properties show that cellulose explores greater conformational variability in the ionic liquid than in water. For instance, in BmimCl the cellulose intramolecular hydrogen bond O3H'••• O5 is disrupted more often resulting in greater flexibility of the solute. Our results indicate that the cellulose chain is more dynamic in BmimCl than in water, which may play a role in the favorable dissolution of cellulose in the ionic liquid. Here, the calculation of the configurational entropy of the cellulose decamer confirms its higher conformational flexibility in BmimCl than in water at elevated temperatures.« less

Photophysical study of the interaction between ZnO nanoparticles and globular protein bovine serum albumin in solution and in a layer-by-layer self-assembled film

NASA Astrophysics Data System (ADS)

Hansda, Chaitali; Maiti, Pradip; Singha, Tanmoy; Pal, Manisha; Hussain, Syed Arshad; Paul, Sharmistha; Paul, Pabitra Kumar

2018-10-01

In this study, we investigated the spectroscopic properties of the water-soluble globular protein bovine serum albumin (BSA) while interacting with zinc oxide (ZnO) semiconductor nanoparticles (NPs) in aqueous medium and in a ZnO/BSA layer-by-layer (LbL) self-assembled film fabricated on poly (acrylic acid) (PAA)-coated quartz or a Si substrate via electrostatic interactions. BSA formed a ground state complex due to its interaction with ZnO NPs, which was confirmed by ultraviolet-visible absorption, and steady state and time-resolved fluorescence emission spectroscopic techniques. However, due to its interaction with ZnO, the photophysical properties of BSA depend significantly on the concentration of ZnO NPs in the mixed solution. The quenching of the fluorescence intensity of BSA in the presence of ZnO NPs was due to the interaction between ZnO and BSA, and the formation of their stable ground state complex, as well as energy transfer from the excited BSA to ZnO NPs in the complex nano-bioconjugated species. Multilayer growth of the ZnO/BSA LbL self-assembled film on the quartz substrate was confirmed by monitoring the characteristic absorption band of BSA (280 nm), where the nature of the film growth depends on the number of bilayers deposited on the quartz substrate. BSA formed a well-ordered molecular network-type morphology due to its adsorption onto the surface of the ZnO nanostructure in the backbone of the PAA-coated Si substrate in the LbL film according to atomic force microscopic study. The as-synthesized ZnO NPs were characterized by field emission scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering techniques.

Strong CH/O interactions between polycyclic aromatic hydrocarbons and water: Influence of aromatic system size.

PubMed

Veljković, Dušan Ž

2018-03-01

Energies of CH/O interactions between water molecule and polycyclic aromatic hydrocarbons with a different number of aromatic rings were calculated using ab initio calculations at MP2/cc-PVTZ level. Results show that an additional aromatic ring in structure of polycyclic aromatic hydrocarbons significantly strengthens CH/O interactions. Calculated interaction energies in optimized structures of the most stable tetracene/water complex is -2.27 kcal/mol, anthracene/water is -2.13 kcal/mol and naphthalene/water is -1.97 kcal/mol. These interactions are stronger than CH/O contacts in benzene/water complex (-1.44 kcal/mol) while CH/O contacts in tetracene/water complex are even stronger than CH/O contacts in pyridine/water complexes (-2.21 kcal/mol). Electrostatic potential maps for different polycyclic aromatic hydrocarbons were calculated and used to explain trends in the energies of interactions. Copyright © 2017 Elsevier Inc. All rights reserved.

Intra- and intermolecular interaction inducing pyramidalization on both sides of a proline dipeptide during isomerization: an ab initio QM/MM molecular dynamics simulation study in explicit water.

PubMed

Yonezawa, Yasushige; Nakata, Kazuto; Sakakura, Kota; Takada, Toshikazu; Nakamura, Haruki

2009-04-01

The cis-trans isomerization of the peptide bond preceding a proline plays important roles in protein folding and biological function. Although many experimental and theoretical studies have been done, the mechanism has not yet been clearly elucidated. We studied the cis-trans isomerization of the proline dipeptide (Ace-Pro-NMe) in explicit water by molecular dynamics simulations using a combined potential derived from ab initio quantum mechanics and empirical molecular mechanics. We obtained the free energy landscape during the isomerization by using the umbrella sampling method. The free energy landscape is in good accordance with previous experimental and theoretical values. We observed that in the middle of the isomerization, the prolyl nitrogen transiently takes pyramidal conformations in two polarized directions and that, simultaneously, the prolyl C-N bond extends. We show that these geometrical changes cooperatively transform the prolyl nitrogen from a sp(2)-hybridized electronic state into a sp(3)-hybridized one, and thus realize a transition state that reduces the rotational barriers separating the cis- and trans-states. We also found that the hydration of the prolyl nitrogen stabilizes the negative pyramidal conformation, while an intramolecular interaction mainly stabilizes the positive one. Fluctuations in the polarity and magnitude of the pyramidal conformation during the isomerization are interpreted as a competition between the hydrogen-bonding partners for the prolyl nitrogen between different sides of the pyrrolidine ring.

A Two-Tailed Phosphopeptide Crystallizes to Form a Lamellar Structure.

PubMed

Pellach, Michal; Mondal, Sudipta; Harlos, Karl; Mance, Deni; Baldus, Marc; Gazit, Ehud; Shimon, Linda J W

2017-03-13

The crystal structure of a designed phospholipid-inspired amphiphilic phosphopeptide at 0.8 Å resolution is presented. The phosphorylated β-hairpin peptide crystallizes to form a lamellar structure that is stabilized by intra- and intermolecular hydrogen bonding, including an extended β-sheet structure, as well as aromatic interactions. This first reported crystal structure of a two-tailed peptidic bilayer reveals similarities in thickness to a typical phospholipid bilayer. However, water molecules interact with the phosphopeptide in the hydrophilic region of the lattice. Additionally, solid-state NMR was used to demonstrate correlation between the crystal structure and supramolecular nanostructures. The phosphopeptide was shown to self-assemble into semi-elliptical nanosheets, and solid-state NMR provides insight into the self-assembly mechanisms. This work brings a new dimension to the structural study of biomimetic amphiphilic peptides with determination of molecular organization at the atomic level. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heat transfer from nanoparticles: a corresponding state analysis.

PubMed

Merabia, Samy; Shenogin, Sergei; Joly, Laurent; Keblinski, Pawel; Barrat, Jean-Louis

2009-09-08

In this contribution, we study situations in which nanoparticles in a fluid are strongly heated, generating high heat fluxes. This situation is relevant to experiments in which a fluid is locally heated by using selective absorption of radiation by solid particles. We first study this situation for different types of molecular interactions, using models for gold particles suspended in octane and in water. As already reported in experiments, very high heat fluxes and temperature elevations (leading eventually to particle destruction) can be observed in such situations. We show that a very simple modeling based on Lennard-Jones (LJ) interactions captures the essential features of such experiments and that the results for various liquids can be mapped onto the LJ case, provided a physically justified (corresponding state) choice of parameters is made. Physically, the possibility of sustaining very high heat fluxes is related to the strong curvature of the interface that inhibits the formation of an insulating vapor film.

Stochastic simulation of ecohydrological interactions between vegetation and groundwater

NASA Astrophysics Data System (ADS)

Dwelle, M. C.; Ivanov, V. Y.; Sargsyan, K.

2017-12-01

The complex interactions between groundwater and vegetation in the Amazon rainforest may yield vital ecophysiological interactions in specific landscape niches such as buffering plant water stress during dry season or suppression of water uptake due to anoxic conditions. Representation of such processes is greatly impacted by both external and internal sources of uncertainty: inaccurate data and subjective choice of model representation. The models that can simulate these processes are complex and computationally expensive, and therefore make it difficult to address uncertainty using traditional methods. We use the ecohydrologic model tRIBS+VEGGIE and a novel uncertainty quantification framework applied to the ZF2 watershed near Manaus, Brazil. We showcase the capability of this framework for stochastic simulation of vegetation-hydrology dynamics. This framework is useful for simulation with internal and external stochasticity, but this work will focus on internal variability of groundwater depth distribution and model parameterizations. We demonstrate the capability of this framework to make inferences on uncertain states of groundwater depth from limited in situ data, and how the realizations of these inferences affect the ecohydrological interactions between groundwater dynamics and vegetation function. We place an emphasis on the probabilistic representation of quantities of interest and how this impacts the understanding and interpretation of the dynamics at the groundwater-vegetation interface.

CW EPR parameters reveal cytochrome P450 ligand binding modes.

PubMed

Lockart, Molly M; Rodriguez, Carlo A; Atkins, William M; Bowman, Michael K

2018-06-01

Cytochrome P450 (CYP) monoxygenses utilize heme cofactors to catalyze oxidation reactions. They play a critical role in metabolism of many classes of drugs, are an attractive target for drug development, and mediate several prominent drug interactions. Many substrates and inhibitors alter the spin state of the ferric heme by displacing the heme's axial water ligand in the resting enzyme to yield a five-coordinate iron complex, or they replace the axial water to yield a nitrogen-ligated six-coordinate iron complex, which are traditionally assigned by UV-vis spectroscopy. However, crystal structures and recent pulsed electron paramagnetic resonance (EPR) studies find a few cases where molecules hydrogen bond to the axial water. The water-bridged drug-H 2 O-heme has UV-vis spectra similar to nitrogen-ligated, six-coordinate complexes, but are closer to "reverse type I" complexes described in older liteature. Here, pulsed and continuous wave (CW) EPR demonstrate that water-bridged complexes are remarkably common among a range of nitrogenous drugs or drug fragments that bind to CYP3A4 or CYP2C9. Principal component analysis reveals a distinct clustering of CW EPR spectral parameters for water-bridged complexes. CW EPR reveals heterogeneous mixtures of ligated states, including multiple directly-coordinated complexes and water-bridged complexes. These results suggest that water-bridged complexes are under-represented in CYP structural databases and can have energies similar to other ligation modes. The data indicates that water-bridged binding modes can be identified and distinguished from directly-coordinated binding by CW EPR. Copyright © 2018 Elsevier Inc. All rights reserved.

Reorientation Motion and Preferential Interactions of a Peptide in Denaturants and Osmolyte.

PubMed

Jas, Gouri S; Rentchler, Eric C; Słowicka, Agnieszka M; Hermansen, John R; Johnson, Carey K; Middaugh, C Russell; Kuczera, Krzysztof

2016-03-31

Fluorescence anisotropy decay measurements and all atom molecular dynamics simulations are used to characterize the orientational motion and preferential interaction of a peptide, N-acetyl-tryptophan-amide (NATA) containing two peptide bonds, in aqueous, urea, guanidinium chloride (GdmCl), and proline solution. Anisotropy decay measurements as a function of temperature and concentration showed moderate slowing of reorientations in urea and GdmCl and very strong slowing in proline solution, relative to water. These effects deviate significantly from simple proportionality of peptide tumbling time to solvent viscosity, leading to the investigation of microscopic preferential interaction behavior through molecular dynamics simulations. Examination of the interactions of denaturants and osmolyte with the peptide backbone uncovers the presence of strongest interaction with urea, intermediate with proline, and weakest with GdmCl. In contrast, the strongest preferential solvation of the peptide side chain is by the nonpolar part of the proline zwitterion, followed by urea, and GdmCl. Interestingly, the local density of urea around the side chain is higher, but the GdmCl distribution is more organized. Thus, the computed preferential solvation of the side chain by the denaturants and osmolyte can account for the trend in reorientation rates. Analysis of water structure and its dynamics uncovered underlying differences between urea, GdmCl, and proline. Urea exerted the smallest perturbation of water behavior. GdmCl had a larger effect on water, slowing kinetics and stabilizing interactions. Proline had the largest overall interactions, exhibiting a strong stabilizing effect on both water-water and water-peptide hydrogen bonds. The results for this elementary peptide system demonstrate significant differences in microscopic behavior of the examined solvent environments. For the commonly used denaturants, urea tends to form disorganized local aggregates around the peptide groups and has little influence on water, while GdmCl only forms specific interactions with the side chain and tends to destabilize water structure. The protective osmolyte proline has the strongest and most specific interactions with the tryptophan side chain, and also stabilizes both water-water and water-peptide hydrogen bonds. Our results strongly suggest protein or peptide denaturation triggered by urea occurs by direct interaction, whereas GdmCl interacts favorably with side chains and destabilizes peptide-water hydrogen bonds. The stabilization of biopolymers by an osmolyte such as proline is governed by favorable preferential interaction with the side chains and stabilization of water.

Surface and Groundwater Interactions: Cikapundung Bandung, Kanal Banjir Timur Semarang and Cisadane Tangerang

NASA Astrophysics Data System (ADS)

Irawan, D. E.; Sulistyawati, E.; Midori, A. A.; Faisal, B.; Darul, A.; Agustin, A.

2018-04-01

In most Asia countries, the riverbank area is mostly inhabited by the low-income population, due to the shortage of formal housing. Most of the settlement areas are not equipped with proper sanitation system. Hence, the water quality gets lower over time with the increasing number of inhabitants around the riverbank. Th water quality gets worse with the close hydrological connection between surface water and the shallow groundwater. We compare the state of water quality based on our three case studies: Cikapundung Bandung, Kanal Banjir Timur Semarang, and Cisadane Tangerang. In each location, we gathered the following data: water level measurements, water flow mapping, and water quality samples. Then we make maps to evaluate existing status. The comparison will be made based on the physical and chemical properties that we get from the field. On all locations, we find very close interactions between surface water and groundwater. The hydrological connections are different in direction from upstream to downstream: gaining stream, combined stream or perched stream, and losing stream. However different river gradient gives a slightly different length of hydrological zonations. All samples show a high bicarbonate from rain water, the dissolution of carbonate minerals from the rocks and soils, and also organic species from microbial activities, which induced by domestic wastes. However, we need to make a carbonate balance calculation to break down the components. All samples also have high nitrate and nitrite concentration which come from domestic waste along the river and fertilizer from the rice fields upstream (only in Cikapundung river). For further research, we suggest chemical modeling to break up the contamination components and possible sources.

DETECTION OF EXTREMELY BROAD WATER EMISSION FROM THE MOLECULAR CLOUD INTERACTING SUPERNOVA REMNANT G349.7+0.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rho, J.; Hewitt, J. W.; Boogert, A.

2015-10-10

We performed Herschel HIFI, PACS, and SPIRE observations toward the molecular cloud interacting supernova remnant G349.7+0.2. An extremely broad emission line was detected at 557 GHz from the ground state transition 1{sub 10}-1{sub 01} of ortho-water. This water line can be separated into three velocity components with widths of 144, 27, and 4 km s{sup −1}. The 144 km s{sup −1} component is the broadest water line detected to date in the literature. This extremely broad line width shows the importance of probing shock dynamics. PACS observations revealed three additional ortho-water lines, as well as numerous high-J carbon monoxide (CO)more » lines. No para-water lines were detected. The extremely broad water line is indicative of a high velocity shock, which is supported by the observed CO rotational diagram that was reproduced with a J-shock model with a density of 10{sup 4} cm{sup −3} and a shock velocity of 80 km s{sup −1}. Two far-infrared fine-structure lines, [O i] at 145 μm and [C ii] line at 157 μm, are also consistent with the high velocity J-shock model. The extremely broad water line could be simply from short-lived molecules that have not been destroyed in high velocity J-shocks; however, it may be from more complicated geometry such as high-velocity water bullets or a shell expanding in high velocity. We estimate the CO and H{sub 2}O densities, column densities, and temperatures by comparison with RADEX and detailed shock models.« less

Ionizing power and nucleophilicity in water in oil AOT-based microemulsions.

PubMed

García-Río, Luis; Hervella, Pablo; Leis, José Ramón

2005-08-16

A study was carried out on the solvolysis of substituted phenyl chloroformates in AOT/isooctane/water microemulsions. (AOT is the sodium salt of bis(2-ethyhexyl)sulfosuccinate.) The results obtained have been interpreted by taking into account the distribution of the chloroformates between the continuous medium and the interface of the microemulsions, where the reactions take place. The values obtained for the rate constant in the interface, k(i), decreases as the water content of the microemulsions increases, as a consequence of the decrease in its nucleophilic capacity. This behavior is consistent with a rate-determining step of water addition to the carbonyl group. The values of k(i) allow us to obtain the slopes of the Hammett correlations at the interface of the microemulsions, rho = 2.25, whose values are greater than those obtained in an aqueous medium, rho = 0.82. This increase in the Hammett slope is similar to that observed in ethanol/water mixtures and is a consequence of a variation in the structure of the transition state of the reaction where there is a smaller extension of the expulsion of the leaving group. The values of the rate constants at the interface of the microemulsions have allowed us, by means of the Grunwald-Winstein equation, to obtain the solvent ionizing power and the nucleophilicity of the solvent. The values obtained for Y(Cl) increase together with the water content of the microemulsion, whereas the values of N(T) decrease. These variations are a consequence of the interaction between the AOT headgroups and the interfacial water, where the water molecules act like electronic acceptors. The intensity of this interaction is greater if the system has a small water content, which explains the variation of Y(Cl) and N(T).

The search for and analysis of direct samples of early Solar System aqueous fluids.

PubMed

Zolensky, Michael E; Bodnar, Robert J; Yurimoto, Hisayoshi; Itoh, Shoichi; Fries, Marc; Steele, Andrew; Chan, Queenie H-S; Tsuchiyama, Akira; Kebukawa, Yoko; Ito, Motoo

2017-05-28

We describe the current state of the search for direct, surviving samples of early, inner Solar System fluids-fluid inclusions in meteorites. Meteoritic aqueous fluid inclusions are not rare, but they are very tiny and their characterization is at the state of the art for most analytical techniques. Meteoritic fluid inclusions offer us a unique opportunity to study early Solar System brines in the laboratory. Inclusion-by-inclusion analyses of the trapped fluids in carefully selected samples will, in the immediate future, provide us detailed information on the evolution of fluids as they interacted with anhydrous solid materials. Thus, real data can replace calculated fluid compositions in thermochemical calculations of the evolution of water and aqueous reactions in comets, asteroids, moons and the terrestrial planets.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'. © 2017 The Author(s).

Two Active Site Divalent Ions in the Crystal Structure of the Hammerhead Ribozyme Bound to a Transition State Analogue.

PubMed

Mir, Aamir; Golden, Barbara L

2016-02-02

The crystal structure of the hammerhead ribozyme bound to the pentavalent transition state analogue vanadate reveals significant rearrangements relative to the previously determined structures. The active site contracts, bringing G10.1 closer to the cleavage site and repositioning a divalent metal ion such that it could, ultimately, interact directly with the scissile phosphate. This ion could also position a water molecule to serve as a general acid in the cleavage reaction. A second divalent ion is observed coordinated to O6 of G12. This metal ion is well-placed to help tune the pKA of G12. On the basis of this crystal structure as well as a wealth of biochemical studies, we propose a mechanism in which G12 serves as the general base and a magnesium-bound water serves as a general acid.

Spectral Analysis of the Wake behind a Helicopter Rotor Hub

NASA Astrophysics Data System (ADS)

Petrin, Christopher; Reich, David; Schmitz, Sven; Elbing, Brian

2016-11-01

A scaled model of a notional helicopter rotor hub was tested in the 48" Garfield Thomas Water Tunnel at the Applied Research Laboratory Penn State. LDV and PIV measurements in the far-wake consistently showed a six-per-revolution flow structure, in addition to stronger two- and four-per-revolution structures. These six-per-revolution structures persisted into the far-field, and have no direct geometric counterpart on the hub model. The current study will examine the Reynolds number dependence of these structures and present higher-order statistics of the turbulence within the wake. In addition, current activity using the EFPL Large Water Tunnel at Oklahoma State University will be presented. This effort uses a more canonical configuration to identify the source for these six-per-revolution structures, which are assumed to be a non-linear interaction between the two- and four-per-revolution structures.

Two active site divalent ions in the crystal structure of the hammerhead ribozyme bound to a transition state analogue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mir, Aamir; Golden, Barbara L.

2015-11-09

The crystal structure of the hammerhead ribozyme bound to the pentavalent transition state analogue vanadate reveals significant rearrangements relative to the previously determined structures. The active site contracts, bringing G10.1 closer to the cleavage site and repositioning a divalent metal ion such that it could, ultimately, interact directly with the scissile phosphate. This ion could also position a water molecule to serve as a general acid in the cleavage reaction. A second divalent ion is observed coordinated to O6 of G12. This metal ion is well-placed to help tune the p K A of G12. Finally, on the basis ofmore » this crystal structure as well as a wealth of biochemical studies, in this paper we propose a mechanism in which G12 serves as the general base and a magnesium-bound water serves as a general acid.« less

Terahertz vibration-rotation-tunneling (VRT) spectroscopy of the d6-water trimer: Complete characterization of the 2.94 THz torsional band ( kn = ±2 1 ← 0 0)

NASA Astrophysics Data System (ADS)

Han, Jia-xiang; Takahashi, Lynelle K.; Lin, Wei; Lee, Eddy; Keutsch, Frank N.; Saykally, Richard J.

2006-06-01

We report the measurement and analysis of the complete perpendicular kn = ±2 1 ← 0 0 (D 2O) 3 torsional band (origin 2940.9376(3) GHz), the upper state of which is the highest-energy (98.09912 cm -1) torsional state yet observed. All known torsional transitions were included in a new global analysis of the six observed torsional bands, using the effective Hamiltonians derived by van der Avoird et al. [M. R. Viant, M. G. Brown, J. D. Cruzan, R. J. Saykally, M. Geleijns, A. van der Avoird, J. Chem. Phys. 110 (1999) 4369; A. van der Avoird, E. H. T. Olthof, P. E. S. Wormer, J. Chem. Phys. 105 (1996) 8034]. The experimental results will facilitate the descriptions of three-body interactions in water intermolecular potential energy surfaces (IPSs).

A New Poisson-Nernst-Planck Model with Ion-Water Interactions for Charge Transport in Ion Channels.

PubMed

Chen, Duan

2016-08-01

In this work, we propose a new Poisson-Nernst-Planck (PNP) model with ion-water interactions for biological charge transport in ion channels. Due to narrow geometries of these membrane proteins, ion-water interaction is critical for both dielectric property of water molecules in channel pore and transport dynamics of mobile ions. We model the ion-water interaction energy based on realistic experimental observations in an efficient mean-field approach. Variation of a total energy functional of the biological system yields a new PNP-type continuum model. Numerical simulations show that the proposed model with ion-water interaction energy has the new features that quantitatively describe dielectric properties of water molecules in narrow pores and are possible to model the selectivity of some ion channels.

Theoretical modeling of the absorption spectrum of aqueous riboflavin

NASA Astrophysics Data System (ADS)

Zanetti-Polzi, Laura; Aschi, Massimiliano; Daidone, Isabella; Amadei, Andrea

2017-02-01

In this study we report the modeling of the absorption spectrum of riboflavin in water using a hybrid quantum/classical mechanical approach, the MD-PMM methodology. By means of MD-PMM calculations, with which the effect of riboflavin internal motions and of solvent interactions on the spectroscopic properties can be explicitly taken into account, we obtain an absorption spectrum in very good agreement with the experimental spectrum. In particular, the calculated peak maxima show a consistent improvement with respect to previous computational approaches. Moreover, the calculations show that the interaction with the environment may cause a relevant recombination of the gas-phase electronic states.

Surface characterization of U(AlxSi1-x)3 alloy and its interaction with O2 and H2O, at room temperature

NASA Astrophysics Data System (ADS)

Matmor, M.; Cohen, S.; Rafailov, G.; Vaknin, M.; Shamir, N.; Gouder, T.; Zalkind, S.

2018-02-01

Surface characterization and the interactions of U(AlxSi1-x)3 alloy (x = 0.57) with oxygen and water vapor were studied, utilizing X-Ray Photoelectron Spectroscopy and Direct Recoil Spectrometry, at room temperature. The U 4f spectrum of U(AlxSi1-x)3 alloy exhibits weak correlation satellites, suggesting an itinerant description of the U 5f states for this compound. The Al and Si 2p lines are chemically shifted to lower binding energies. Exposing the alloy to oxygen and water vapor results in oxidation of mainly the uranium and aluminum components, while silicon is only slightly oxidized. Oxygen was found to be a stronger oxidizer than water vapor and the trend is consistent with the more negative enthalpies of formation of metal oxides produced by the O2 reaction, as compared to H2O. During oxygen exposure, fast oxidation occurs by oxide islands nucleation and lateral growth, followed by oxidation of the sub-surface, up to ∼4 nm, at 1000 L exposure. Water initially reacts with the surface by full dissociation and oxide islands formation, which is then covered by hydroxides. Only a minor increase in the oxide thickness of up to ∼2.5 nm, was observed after coalescence.

Coupled impacts of climate and land use change across a river-lake continuum: insights from an integrated assessment model of Lake Champlain’s Missisquoi Basin, 2000-2040

NASA Astrophysics Data System (ADS)

Zia, Asim; Bomblies, Arne; Schroth, Andrew W.; Koliba, Christopher; Isles, Peter D. F.; Tsai, Yushiou; Mohammed, Ibrahim N.; Bucini, Gabriela; Clemins, Patrick J.; Turnbull, Scott; Rodgers, Morgan; Hamed, Ahmed; Beckage, Brian; Winter, Jonathan; Adair, Carol; Galford, Gillian L.; Rizzo, Donna; Van Houten, Judith

2016-11-01

Global climate change (GCC) is projected to bring higher-intensity precipitation and higher-variability temperature regimes to the Northeastern United States. The interactive effects of GCC with anthropogenic land use and land cover changes (LULCCs) are unknown for watershed level hydrological dynamics and nutrient fluxes to freshwater lakes. Increased nutrient fluxes can promote harmful algal blooms, also exacerbated by warmer water temperatures due to GCC. To address the complex interactions of climate, land and humans, we developed a cascading integrated assessment model to test the impacts of GCC and LULCC on the hydrological regime, water temperature, water quality, bloom duration and severity through 2040 in transnational Lake Champlain’s Missisquoi Bay. Temperature and precipitation inputs were statistically downscaled from four global circulation models (GCMs) for three Representative Concentration Pathways. An agent-based model was used to generate four LULCC scenarios. Combined climate and LULCC scenarios drove a distributed hydrological model to estimate river discharge and nutrient input to the lake. Lake nutrient dynamics were simulated with a 3D hydrodynamic-biogeochemical model. We find accelerated GCC could drastically limit land management options to maintain water quality, but the nature and severity of this impact varies dramatically by GCM and GCC scenario.

Structural effects of Cu(II)-coordination in the octapeptide region of the human prion protein.

PubMed

Riihimäki, Eva-Stina; Martínez, José Manuel; Kloo, Lars

2008-05-14

The copper-binding ability of the prion protein is thought to be central to its function. The structural effects of copper coordination in the octapeptide region of the human prion protein have been investigated by molecular dynamics simulations. Simulations were performed with the apo state, in order to investigate the behavior of the region without copper ions, as well as with the octapeptide region in the presence of copper ions. While the structure of the apo state is greatly influenced by the interaction between the rings in the histidine, tryptophan and proline residues, the region shows evidence of highly ordered coordination sites in the presence of copper ions. The position of the tryptophan indole ring is stabilized by cation-pi interactions. Two stable orientations of the indole ring with respect to the equatorial coordination plane of copper were observed, which showed that the indole ring can reside on both sides of the coordination plane. The interaction with the indole ring was found to occur without a mediating axial water molecule.

Structure and Electronic Spectra of Purine-Methyl Viologen Charge Transfer Complexes

PubMed Central

Jalilov, Almaz S.; Patwardhan, Sameer; Singh, Arunoday; Simeon, Tomekia; Sarjeant, Amy A.; Schatz, George C.; Lewis, Frederick D.

2014-01-01

The structure and properties of the electron donor-acceptor complexes formed between methyl viologen (MV) and purine nucleosides and nucleotides in water and the solid state have been investigated using a combination of experimental and theoretical methods. Solution studies were performed using UV-vis and 1H NMR spectroscopy. Theoretical calculations were performed within the framework of density functional theory (DFT). Energy decomposition analysis indicates that dispersion and induction (charge-transfer) interactions dominate the total binding energy, whereas electrostatic interactions are largely repulsive. The appearance of charge transfer bands in the absorption spectra of the complexes are well described by time-dependent (TD) DFT and are further explained in terms of the redox properties of purine monomers and solvation effects. Crystal structures are reported for complexes of methyl viologen with the purines 2′-deoxyguanosine 3′-monophosphate GMP (DAD′DAD′ type) and 7-deazaguanosine zG (DAD′ADAD′ type). Comparison of the structures determined in the solid state and by theoretical methods in solution provides valuable insights into the nature of charge-transfer interactions involving purine bases as electron donors. PMID:24294996

Bound Water at Protein-Protein Interfaces: Partners, Roles and Hydrophobic Bubbles as a Conserved Motif

PubMed Central

Ahmed, Mostafa H.; Spyrakis, Francesca; Cozzini, Pietro; Tripathi, Parijat K.; Mozzarelli, Andrea; Scarsdale, J. Neel; Safo, Martin A.; Kellogg, Glen E.

2011-01-01

Background There is a great interest in understanding and exploiting protein-protein associations as new routes for treating human disease. However, these associations are difficult to structurally characterize or model although the number of X-ray structures for protein-protein complexes is expanding. One feature of these complexes that has received little attention is the role of water molecules in the interfacial region. Methodology A data set of 4741 water molecules abstracted from 179 high-resolution (≤ 2.30 Å) X-ray crystal structures of protein-protein complexes was analyzed with a suite of modeling tools based on the HINT forcefield and hydrogen-bonding geometry. A metric termed Relevance was used to classify the general roles of the water molecules. Results The water molecules were found to be involved in: a) (bridging) interactions with both proteins (21%), b) favorable interactions with only one protein (53%), and c) no interactions with either protein (26%). This trend is shown to be independent of the crystallographic resolution. Interactions with residue backbones are consistent for all classes and account for 21.5% of all interactions. Interactions with polar residues are significantly more common for the first group and interactions with non-polar residues dominate the last group. Waters interacting with both proteins stabilize on average the proteins' interaction (−0.46 kcal mol−1), but the overall average contribution of a single water to the protein-protein interaction energy is unfavorable (+0.03 kcal mol−1). Analysis of the waters without favorable interactions with either protein suggests that this is a conserved phenomenon: 42% of these waters have SASA ≤ 10 Å2 and are thus largely buried, and 69% of these are within predominantly hydrophobic environments or “hydrophobic bubbles”. Such water molecules may have an important biological purpose in mediating protein-protein interactions. PMID:21961043

Structural interactions between lipids, water and S1-S4 voltage-sensing domains.

PubMed

Krepkiy, Dmitriy; Gawrisch, Klaus; Swartz, Kenton J

2012-11-02

Membrane proteins serve crucial signaling and transport functions, yet relatively little is known about their structures in membrane environments or how lipids interact with these proteins. For voltage-activated ion channels, X-ray structures suggest that the mobile voltage-sensing S4 helix would be exposed to the membrane, and functional studies reveal that lipid modification can profoundly alter channel activity. Here, we use solid-state NMR to investigate structural interactions of lipids and water with S1-S4 voltage-sensing domains and to explore whether lipids influence the structure of the protein. Our results demonstrate that S1-S4 domains exhibit extensive interactions with lipids and that these domains are heavily hydrated when embedded in a membrane. We also find evidence for preferential interactions of anionic lipids with S1-S4 domains and that these interactions have lifetimes on the timescale of ≤ 10(-3)s. Arg residues within S1-S4 domains are well hydrated and are positioned in close proximity to lipids, exhibiting local interactions with both lipid headgroups and acyl chains. Comparative studies with a positively charged lipid lacking a phosphodiester group reveal that this lipid modification has only modest effects on the structure and hydration of S1-S4 domains. Taken together, our results demonstrate that Arg residues in S1-S4 voltage-sensing domains reside in close proximity to the hydrophobic interior of the membrane yet are well hydrated, a requirement for carrying charge and driving protein motions in response to changes in membrane voltage. Published by Elsevier Ltd.

Structural interactions between lipids, water and S1-S4 voltage-sensing domains

PubMed Central

Krepkiy, Dmitriy; Gawrisch, Klaus; Swartz, Kenton J.

2012-01-01

Membrane proteins serve crucial signaling and transport functions, yet relatively little is known about their structures in membrane environments or how lipids interact with these proteins. For voltage-activated ion channels, X-ray structures suggest that the mobile voltage-sensing S4 helix would be exposed to the membrane, and functional studies reveal that lipid modification can profoundly alter channel activity. Here we use solid-state NMR to investigate structural interactions of lipids and water with S1-S4 voltage-sensing domains, and to explore whether lipids influence the structure of the protein. Our results demonstrate that S1-S4 domains exhibit extensive interactions with lipids, and that these domains are heavily hydrated when embedded in a membrane. We also find evidence for preferential interactions of anionic lipids with S1-S4 domains, and that these interactions have lifetimes on the timescale of 10−3s. Arg residues within S1-S4 domains are well-hydrated and are positioned in close proximity to lipids, exhibiting local interactions with both lipid head groups and acyl chains. Comparative studies with a positively charged lipid lacking a phosphodiester group reveal that this lipid modification has only modest effects on the structure and hydration of S1-S4 domains. Taken together, our results demonstrate that Arg residues in S1-S4 voltage-sensing domains reside in close proximity to the hydrophobic interior of the membrane, yet are well-hydrated, a requirement for carrying charge and driving protein motions in response to changes in membrane voltage. PMID:22858867

Probing membrane protein structure using water polarization transfer solid-state NMR.

PubMed

Williams, Jonathan K; Hong, Mei

2014-10-01

Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected (1)H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. Copyright © 2014 Elsevier Inc. All rights reserved.

Toward an atomistic description of the urea-denatured state of proteins.

PubMed

Candotti, Michela; Esteban-Martín, Santiago; Salvatella, Xavier; Orozco, Modesto

2013-04-09

We present here the characterization of the structural, dynamics, and energetics of properties of the urea-denatured state of ubiquitin, a small prototypical soluble protein. By combining state-of-the-art molecular dynamics simulations with NMR and small-angle X-ray scattering data, we were able to: (i) define the unfolded state ensemble, (ii) understand the energetics stabilizing unfolded structures in urea, (iii) describe the dedifferential nature of the interactions of the fully unfolded proteins with urea and water, and (iv) characterize the early stages of protein refolding when chemically denatured proteins are transferred to native conditions. The results presented herein are unique in providing a complete picture of the chemically unfolded state of proteins and contribute to deciphering the mechanisms that stabilize the native state of proteins, as well as those that maintain them unfolded in the presence of urea.

Toward an atomistic description of the urea-denatured state of proteins

PubMed Central

Candotti, Michela; Esteban-Martín, Santiago; Salvatella, Xavier; Orozco, Modesto

2013-01-01

We present here the characterization of the structural, dynamics, and energetics of properties of the urea-denatured state of ubiquitin, a small prototypical soluble protein. By combining state-of-the-art molecular dynamics simulations with NMR and small-angle X-ray scattering data, we were able to: (i) define the unfolded state ensemble, (ii) understand the energetics stabilizing unfolded structures in urea, (iii) describe the dedifferential nature of the interactions of the fully unfolded proteins with urea and water, and (iv) characterize the early stages of protein refolding when chemically denatured proteins are transferred to native conditions. The results presented herein are unique in providing a complete picture of the chemically unfolded state of proteins and contribute to deciphering the mechanisms that stabilize the native state of proteins, as well as those that maintain them unfolded in the presence of urea. PMID:23536295

CalSimHydro Tool - A Web-based interactive tool for the CalSim 3.0 Hydrology Prepropessor

NASA Astrophysics Data System (ADS)

Li, P.; Stough, T.; Vu, Q.; Granger, S. L.; Jones, D. J.; Ferreira, I.; Chen, Z.

2011-12-01

CalSimHydro, the CalSim 3.0 Hydrology Preprocessor, is an application designed to automate the various steps in the computation of hydrologic inputs for CalSim 3.0, a water resources planning model developed jointly by California State Department of Water Resources and United States Bureau of Reclamation, Mid-Pacific Region. CalSimHydro consists of a five-step FORTRAN based program that runs the individual models in succession passing information from one model to the next and aggregating data as required by each model. The final product of CalSimHydro is an updated CalSim 3.0 state variable (SV) DSS input file. CalSimHydro consists of (1) a Rainfall-Runoff Model to compute monthly infiltration, (2) a Soil moisture and demand calculator (IDC) that estimates surface runoff, deep percolation, and water demands for natural vegetation cover and various crops other than rice, (3) a Rice Water Use Model to compute the water demands, deep percolation, irrigation return flow, and runoff from precipitation for the rice fields, (4) a Refuge Water Use Model that simulates the ponding operations for managed wetlands, and (5) a Data Aggregation and Transfer Module to aggregate the outputs from the above modules and transfer them to the CalSim SV input file. In this presentation, we describe a web-based user interface for CalSimHydro using Google Earth Plug-In. The CalSimHydro tool allows users to - interact with geo-referenced layers of the Water Budget Areas (WBA) and Demand Units (DU) displayed over the Sacramento Valley, - view the input parameters of the hydrology preprocessor for a selected WBA or DU in a time series plot or a tabular form, - edit the values of the input parameters in the table or by downloading a spreadsheet of the selected parameter in a selected time range, - run the CalSimHydro modules in the backend server and notify the user when the job is done, - visualize the model output and compare it with a base run result, - download the output SV file to be used to run CalSim 3.0. The CalSimHydro tool streamlines the complicated steps to configure and run the hydrology preprocessor by providing a user-friendly visual interface and back-end services to validate user inputs and manage the model execution. It is a powerful addition to the new CalSim 3.0 system.

Hydrolytic Unzipping of Boron Nitride Nanotubes in Nitric Acid.

PubMed

Kim, Dukeun; Muramatsu, Hiroyuki; Kim, Yoong Ahm

2017-12-01

Boron nitride nanoribbons (BNNRs) have very attractive electrical and optical properties due to their unique edge states and width-related properties. Herein, for the first time, BNNRs were produced by a simple reflux of boron nitride nanotubes (BNNTs) in nitric acid containing water, which had led to unzipped sidewalls through hydrolysis. Their high reactivity that originated from edges was verified via a strong interaction with methylene blue.

Baseflow response to climate variability induced droughts in the Apalachicola-Chattahoochee-Flint River Basin, U.S.A.

NASA Astrophysics Data System (ADS)

Singh, Sarmistha; Srivastava, Puneet; Abebe, Ash; Mitra, Subhasis

2015-09-01

Droughts have been a major factor leading to the Tri-State Water Wars in the southeastern United States. One of the primary issues related to the conflict is the reduction in baseflow levels in the Flint River during droughts. This affects the availability of freshwater resources to support the endangered mussel species in the Flint and Apalachicola Rivers and threatens the shellfish industry in the Apalachicola Bay. Study of large-scale climate phenomena as well as the interactions of interannual with decadal and multidecadal oceanic-atmospheric phenomena can provide valuable information regarding regional climatic conditions such as droughts and their impact on water resources. This study was conducted to quantify the impacts of climate variability cycles on baseflow levels in the Flint River. The individual and coupled impacts of the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO) on baseflow were quantified. The non-parametric Joint Rank Fit (JRFit) procedure was used to provide a robust test of the significance of interactions between the phases of ENSO-PDO, ENSO-AMO and ENSO-NAO baseflows. Simple-main effect comparisons were also performed using the JRFit model to estimate significant difference between the positive and negative phase baseflows of PDO, AMO and NAO associated with El Niño or La Niña phases. The results indicate that the phases of ENSO, AMO and NAO significantly affect baseflows in the Flint River. Interaction tests showed that the PDO and AMO phases modulate ENSO phase baseflows. La Niña associated with positive phases of PDO and AMO resulted in greater decrease in baseflow levels of approximately 28% and 33%, respectively. However, La Niña associated with negative phase of AMO showed above normal baseflows. The results illustrate the importance of coupled analyses of climate variability by providing a better understanding of the severity of droughts and their impact on baseflows. The results obtained from this study can be used by water managers in the region as a guide for the issuance of drought severity-based water restrictions.

Recent Upgrades to the NASA Ames Mars General Circulation Model: Applications to Mars' Water Cycle

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, M. A.; Haberle, R. M.; Montmessin, F.; Wilson, R. J.; Schaeffer, J.

2008-09-01

We report on recent improvements to the NASA Ames Mars general circulation model (GCM), a robust 3D climate-modeling tool that is state-of-the-art in terms of its physics parameterizations and subgrid-scale processes, and which can be applied to investigate physical and dynamical processes of the present (and past) Mars climate system. The most recent version (gcm2.1, v.24) of the Ames Mars GCM utilizes a more generalized radiation code (based on a two-stream approximation with correlated k's); an updated transport scheme (van Leer formulation); a cloud microphysics scheme that assumes a log-normal particle size distribution whose first two moments are treated as atmospheric tracers, and which includes the nucleation, growth and sedimentation of ice crystals. Atmospheric aerosols (e.g., dust and water-ice) can either be radiatively active or inactive. We apply this version of the Ames GCM to investigate key aspects of the present water cycle on Mars. Atmospheric dust is partially interactive in our simulations; namely, the radiation code "sees" a prescribed distribution that follows the MGS thermal emission spectrometer (TES) year-one measurements with a self-consistent vertical depth scale that varies with season. The cloud microphysics code interacts with a transported dust tracer column whose surface source is adjusted to maintain the TES distribution. The model is run from an initially dry state with a better representation of the north residual cap (NRC) which accounts for both surface-ice and bare-soil components. A seasonally repeatable water cycle is obtained within five Mars years. Our sub-grid scale representation of the NRC provides for a more realistic flux of moisture to the atmosphere and a much drier water cycle consistent with recent spacecraft observations (e.g., Mars Express PFS, corrected MGS/TES) compared to models that assume a spatially uniform and homogeneous north residual polar cap.

Femtosecond dynamics of a cardiotonic medicine (milrinone) in neutral water

NASA Astrophysics Data System (ADS)

Gil, M.; Douhal, A.

2006-09-01

Milrinone is a medicine used to attenuate heart attack disease. Understanding its interaction with water is of importance for the knowledge of its stability and related phenomena. This intimate information requires the unraveling of the dynamics under the physiological conditions. Here we report the first study of ultrafast processes of this medicine. We show that S 2 relaxation of the keto structure (K) occurs in ˜150 fs and the intramolecular-charge transfer reaction in less than 100 fs to produce a relaxed CT-K state. An observed ˜10 ps decay is assigned to vibrational relaxation/cooling and twisting in the formed CT-K.

A Classroom Simulation of Water-Rock Interaction for Upper-Level Geochemistry Courses.

ERIC Educational Resources Information Center

Cercone, Karen Rose

1988-01-01

Describes a simple hands-on model of water-rock interaction that can be constructed in the classroom using styrofoam bowls and foil-wrapped candies. This interactive simulation allows students to vary the factors which control water-rock interaction and to obtain immediate results. (Author/CW)

Is Superhydrophobicity Equal to Underwater Superaerophilicity: Regulating the Gas Behavior on Superaerophilic Surface via Hydrophilic Defects.

PubMed

Cao, Moyuan; Li, Zhe; Ma, Hongyu; Geng, Hui; Yu, Cunming; Jiang, Lei

2018-06-20

Superhydrophobic surfaces have long been considered as superaerophilic surfaces while being placed in the aqueous environment. However, versatile gas/solid interacting phenomena were reported by utilizing different superhydrophobic substrates, indicating that these two wetting states cannot be simply equated. Herein, we demonstrate how the hydrophilic defects on the superhydrophobic track manipulate the underwater gas delivery, without deteriorating the water repellency of the surface in air. The versatile gas-transporting processes can be achieved on the defected superhydrophobic surfaces; on the contrary, in air, a water droplet is able to roll on those surfaces indistinguishably. Results show that the different media pressures applied on the two wetting states determine the diversified fluid-delivering phenomena; that is, the pressure-induced hydrophilic defects act as a gas barrier to regulate the bubble motion behavior under water. Through the rational incorporation of hydrophilic defects, a series of gas-transporting behaviors are achieved purposively, for example, gas film delivery, bubble transporting, and anisotropic bubble gating, which proves the feasibility of this underwater air-controlling strategy.

Recent advances in understanding the interaction of groundwater and surface water

USGS Publications Warehouse

Winter, Thomas C.

1995-01-01

The most common image of the interaction of groundwater and surface water is that of the interaction of streams with a contiguous alluvial aquifer. This type of system has been the focus of study for more than 100 years, from the work of Boussinesq (1877) to the present, and stream-aquifer interaction continues to be the most common topic of papers discussing the interaction of groundwater and surface water. However, groundwater and surface water interact in a wide variety of landscapes from alpine to coastal. Within these landscapes, ground-water systems range in scale from local to regional, and the types of surface water include streams, lakes, wetlands, and oceans. Given the broad spectrum of the topic of groundwater and surface water interaction, an overview of studies of this topic could be organized according to surface water type, landscape type, scale of hydrologic systems, or field and analytical methods. All these factors are discussed, but this paper is organized according to landscape type because of the great increase in studies of the interaction of groundwater and surface water in landscapes other than riverine systems in the last 15 years. Furthermore, discussing studies by landscape type facilitates comparison of methods and results from different geologic and climatic settings. The general landscapes discussed are mountain terrane, riverine systems, coastal terrane, hummocky terrane, and karst terrane.

Direct measurements of the interactions between clathrate hydrate particles and water droplets.

PubMed

Liu, Chenwei; Li, Mingzhong; Zhang, Guodong; Koh, Carolyn A

2015-08-14

Clathrate hydrate particle agglomeration is often considered to be one of the key limiting factors in plug formation. The hydrate particle-water interaction can play a critical role in describing hydrate agglomeration, yet is severely underexplored. Therefore, this work investigates the interactions between water droplets and cyclopentane hydrate particles using a micromechanical force (MMF) apparatus. Specifically, the effect of contact time, temperature/subcooling, contact area, and the addition of Sorbitane monooleate (Span 80) surfactant on the water droplet-hydrate particle interaction behavior are studied. The measurements indicate that hydrate formation during the measurement would increase the water-hydrate interaction force significantly. The results also indicate that the contact time, subcooling and concentration of cyclopentane, which determine the hydrate formation rate and hydrate amount, will affect the hydrate-water interaction force. In addition, the interaction forces also increase with the water-hydrate contact area. The addition of Span 80 surfactant induces a change in the hydrate morphology and renders the interfaces stable versus unstable (leading to coalescence), and the contact force can affect the hydrate-water interaction behavior significantly. Compared with the hydrate-hydrate cohesion force (measured in cyclopentane), the hydrate-water adhesion force is an order of magnitude larger. These new measurements can help to provide new and critical insights into the hydrate agglomeration process and potential strategies to control this process.

Modeling non-steady state radioisotope transport in the vadose zone--A case study using uranium isotopes at Pena Blanca, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ku, T. L.; Luo, S.; Goldstein, S. J.

2009-06-01

Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leadsmore » to a linear relationship between reciprocal U concentration and {sup 234}U/{sup 238}U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and {alpha}-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Pena Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced {sup 234}U/{sup 238}U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using {sup 234}U/{sup 238}U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.« less

Modeling non-steady state radioisotope transport in the vadose zone - A case study using uranium isotopes at Peña Blanca, Mexico

NASA Astrophysics Data System (ADS)

Ku, T. L.; Luo, S.; Goldstein, S. J.; Murrell, M. T.; Chu, W. L.; Dobson, P. F.

2009-10-01

Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leads to a linear relationship between reciprocal U concentration and 234U/ 238U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and α-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Peña Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced 234U/ 238U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using 234U/ 238U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.

Delineation of spatial-temporal patterns of groundwater/surface-water interaction along a river reach (Aa River, Belgium) with transient thermal modeling

NASA Astrophysics Data System (ADS)

Anibas, Christian; Tolche, Abebe Debele; Ghysels, Gert; Nossent, Jiri; Schneidewind, Uwe; Huysmans, Marijke; Batelaan, Okke

2018-05-01

Among the advances made in analytical and numerical analysis methods to quantify groundwater/surface-water interaction, one methodology that stands out is the use of heat as an environmental tracer. A large data set of river and riverbed temperature profiles from the Aa River in Belgium has been used to examine the spatial-temporal variations of groundwater/surface-water interaction. Exchange fluxes were calculated with the numerical heat-transport code STRIVE. The code was applied in transient mode to overcome previous limitations of steady-state analysis, and allowed for the calculation of model quality. In autumn and winter the mean exchange fluxes reached -90 mm d-1, while in spring and early summer fluxes were -42 mm d-1. Predominantly gaining conditions occurred along the river reach; however, in a few areas the direction of flow changed in time. The river banks showed elevated fluxes up to a factor of 3 compared to the center of the river. Higher fluxes were detected in the upstream section of the reach. Due to the influence of exchange fluxes along the river banks, larger temporal variations were found in the downstream section. The exchange fluxes at the river banks seemed more driven by variable local exchange flows, while the center of the river was dominated by deep and steady regional groundwater flows. These spatial and temporal differences in groundwater/surface-water exchange show the importance of long-term investigations on the driving forces of hyporheic processes across different scales.

The origins of femtomolar protein-ligand binding: hydrogen-bond cooperativity and desolvation energetics in the biotin-(strept)avidin binding site.

PubMed

DeChancie, Jason; Houk, K N

2007-05-02

The unusually strong reversible binding of biotin by avidin and streptavidin has been investigated by density functional and MP2 ab initio quantum mechanical methods. The solvation of biotin by water has also been studied through QM/MM/MC calculations. The ureido moiety of biotin in the bound state hydrogen bonds to five residues, three to the carbonyl oxygen and one for each--NH group. These five hydrogen bonds act cooperatively, leading to stabilization that is larger than the sum of individual hydrogen-bonding energies. The charged aspartate is the key residue that provides the driving force for cooperativity in the hydrogen-bonding network for both avidin and streptavidin by greatly polarizing the urea of biotin. If the residue is removed, the network is disrupted, and the attenuation of the energetic contributions from the neighboring residues results in significant reduction of cooperative interactions. Aspartate is directly hydrogen-bonded with biotin in streptavidin and is one residue removed in avidin. The hydrogen-bonding groups in streptavidin are computed to give larger cooperative hydrogen-bonding effects than avidin. However, the net gain in electrostatic binding energy is predicted to favor the avidin-bicyclic urea complex due to the relatively large penalty for desolvation of the streptavidin binding site (specifically expulsion of bound water molecules). QM/MM/MC calculations involving biotin and the ureido moiety in aqueous solution, featuring PDDG/PM3, show that water interactions with the bicyclic urea are much weaker than (strept)avidin interactions due to relatively low polarization of the urea group in water.

Modelling of chemical degradation of blended cement-based materials by leaching cycles with Callovo-Oxfordian porewater

NASA Astrophysics Data System (ADS)

Olmeda, Javier; Henocq, Pierre; Giffaut, Eric; Grivé, Mireia

2017-06-01

The present work describes a thermodynamic model based on pore water replacement cycles to simulate the chemical evolution of blended cement (BFS + FA) by interaction with external Callovo-Oxfordian (COx) pore water. In the framework of the radioactive waste management, the characterization of the radionuclide behaviour (solubility/speciation, adsorption) in cementitious materials needs to be done for several chemical degradation states (I to IV). In particular, in the context of the deep geological radioactive waste disposal project (Cigéo), cement-based materials will be chemically evolved with time in contact with the host-rock (COx formation). The objective of this study is to provide an equilibrium solution composition for each degradation state for a CEM-V cement-based material to support the adsorption and diffusion experiments reproducing any state of degradation. Calculations have been performed at 25 °C using the geochemical code PhreeqC and an up-to-date thermodynamic database (ThermoChimie v.9.0.b) coupled to SIT approach for ionic strength correction. The model replicates experimental data with accuracy. The approach followed in this study eases the analysis of the chemical evolution in both aqueous and solid phase to obtain a fast assessment of the geochemical effects associated to an external water intrusion of variable composition on concrete structures.

Water quality responses to the interaction between surface water and groundwater along the Songhua River, NE China

NASA Astrophysics Data System (ADS)

Teng, Yanguo; Hu, Bin; Zheng, Jieqiong; Wang, Jinsheng; Zhai, Yuanzheng; Zhu, Chen

2018-03-01

Investigation of surface water and groundwater interaction (SW-GW interaction) provides basic information for regional water-resource protection, management, and development. In this survey of a 10-km-wide area along both sides of the Songhua River, northeast China, the hydrogeochemical responses to different SW-GW interactions were studied. Three types of SW-GW interactions were identified—"recharge", "discharge", and "flow-through"—according to the hydraulic connection between the surface water and groundwater. The single factor index, principal component analysis, and hierarchical cluster analysis of the hydrogeochemistry and pollutant data illuminated the hydrogeochemical response to the various SW-GW interactions. Clear SW-GW interactions along the Songhua River were revealed: (1) upstream in the study area, groundwater usually discharges into the surface water, (2) groundwater is recharged by surface water downstream, and (3) discharge and flow-through coexist in between. Statistical analysis indicated that the degree of hydrogeochemical response in different types of hydraulic connection varied, being clear in recharge and flow-through modes, and less obvious in discharge mode. During the interaction process, dilution, adsorption, redox reactions, nitrification, denitrification, and biodegradation contributed to the pollutant concentration and affected hydrogeochemical response in the hyporheic zone.

Anisotropy of the water-carbon interaction: molecular simulations of water in low-diameter carbon nanotubes.

PubMed

Pérez-Hernández, Guillermo; Schmidt, Burkhard

2013-04-14

Effective Lennard-Jones models for the water-carbon interaction are derived from existing high-level ab initio calculations of water adsorbed on graphene models. The resulting potential energy well (εCO + 2εCH ≈ 1 kJ mol(-1)) is deeper than most of the previously used values in the literature on water in carbon nanotubes (CNTs). Moreover, a substantial anisotropy of the water-carbon interaction (εCO ≈ 2εCH) is obtained, which is neglected in most of the literature. We systematically investigate the effect of this anisotropy on structure and dynamics of TIP5P water confined in narrow, single-walled CNTs by means of molecular dynamics simulations for T = 300 K. While for isotropic models water usually forms one-dimensional, ordered chains inside (6,6) CNTs, we find frequent chain ruptures in simulations with medium to strongly anisotropic potentials. Here, the water molecules tend to form denser clusters displaying a liquid-like behaviour, allowing for self-diffusion along the CNT axis, in contrast to all previous simulations employing spherical (εCH = 0) interaction models. For (7,7) CNTs we observe structures close to trigonal, helical ice nanotubes which exhibit a non-monotonous dependence on the anisotropy of the water-carbon interaction. Both for vanishing and for large values of εCH we find increased fluctuations leading to a more liquid-like behaviour, with enhanced axial diffusion. In contrast, structure and dynamics of water inside (8,8) CNTs are found to be almost independent of the anisotropy of the underlying potential, which is attributed to the higher stability of the non-helical fivefold water prisms. We predict this situation to also prevail for larger CNTs, as the influence of the water-water interaction dominates over that of the water-carbon interaction.

Interaction of cold-water aquifers with exploited reservoirs of the Cerro Prieto geothermal system

USGS Publications Warehouse

Truesdell, Alfred; Lippmann, Marcelo

1990-01-01

Cerro Prieto geothermal reservoirs tend to exhibit good hydraulic communication with adjacent cool groundwater aquifers. Under natural state conditions the hot fluids mix with the surrounding colder waters along the margins of the geothermal system, or discharge to shallow levels by flowing up fault L. In response to exploitation reservoir pressures decrease, leading to changes in the fluid flow pattern in the system and to groundwater influx. The various Cerro Prieto reservoirs have responded differently to production, showing localized near-well or generalized boiling, depending on their access to cool-water recharge. Significant cooling by dilution with groundwater has only been observed in wells located near the edges of the field. In general, entry of cool water at Cerro Prieto is beneficial because it tends to maintain reservoir pressures, restrict boiling, and lengthen the life and productivity of wells.

The current state of Socio-hydrology

NASA Astrophysics Data System (ADS)

Sivapalan, Murugesu; Viglione, Alberto; Di Baldassarre, Giuliano; Pande, Saket

2016-04-01

Socio-hydrology was introduced 4 years ago into the scientific lexicon, and elicited several reactions about the meaning and originality of the concept. However, there has also been much activity triggered by the original paper, including further commentaries that clarified the definitions, and several papers that acted on the definitions, and through them further clarified and illustrated the meaning and usefulness of socio-hydrology for understanding coupled human-water systems and underpinning sustainable water management. This presentation discusses how useful these recent studies have been towards the need for socio-hydrology to explain phenomena, such as rise and decline of human population or food production in water scarce basins ('pendulum swing'), the levee effect, small scale farmer suicides, anthropogenic droughts, etc… We also discuss its foundation as a Science, its similarities and dissimilarities with other fields that study human-water interactions, such as hydro-sociology and hydro-economics, its foundation as a Science, current gaps and the challenges that lie ahead.

Molybdenum disulfide and water interaction parameters

NASA Astrophysics Data System (ADS)

Heiranian, Mohammad; Wu, Yanbin; Aluru, Narayana R.

2017-09-01

Understanding the interaction between water and molybdenum disulfide (MoS2) is of crucial importance to investigate the physics of various applications involving MoS2 and water interfaces. An accurate force field is required to describe water and MoS2 interactions. In this work, water-MoS2 force field parameters are derived using the high-accuracy random phase approximation (RPA) method and validated by comparing to experiments. The parameters obtained from the RPA method result in water-MoS2 interface properties (solid-liquid work of adhesion) in good comparison to the experimental measurements. An accurate description of MoS2-water interaction will facilitate the study of MoS2 in applications such as DNA sequencing, sea water desalination, and power generation.

Genotype by watering regime interaction in cultivated tomato: lessons from linkage mapping and gene expression.

PubMed

Albert, Elise; Gricourt, Justine; Bertin, Nadia; Bonnefoi, Julien; Pateyron, Stéphanie; Tamby, Jean-Philippe; Bitton, Frédérique; Causse, Mathilde

2016-02-01

In tomato, genotype by watering interaction resulted from genotype re-ranking more than scale changes. Interactive QTLs according to watering regime were detected. Differentially expressed genes were identified in some intervals. As a result of climate change, drought will increasingly limit crop production in the future. Studying genotype by watering regime interactions is necessary to improve plant adaptation to low water availability. In cultivated tomato (Solanum lycopersicum L.), extensively grown in dry areas, well-mastered water deficits can stimulate metabolite production, increasing plant defenses and concentration of compounds involved in fruit quality, at the same time. However, few tomato Quantitative Trait Loci (QTLs) and genes involved in response to drought are identified or only in wild species. In this study, we phenotyped a population of 119 recombinant inbred lines derived from a cross between a cherry tomato and a large fruit tomato, grown in greenhouse under two watering regimes, in two locations. A large genetic variability was measured for 19 plant and fruit traits, under the two watering treatments. Highly significant genotype by watering regime interactions were detected and resulted from re-ranking more than scale changes. The population was genotyped for 679 SNP markers to develop a genetic map. In total, 56 QTLs were identified among which 11 were interactive between watering regimes. These later mainly exhibited antagonist effects according to watering treatment. Variation in gene expression in leaves of parental accessions revealed 2259 differentially expressed genes, among which candidate genes presenting sequence polymorphisms were identified under two main interactive QTLs. Our results provide knowledge about the genetic control of genotype by watering regime interactions in cultivated tomato and the possible use of deficit irrigation to improve tomato quality.

A simulation-optimization model for effective water resources management in the coastal zone

NASA Astrophysics Data System (ADS)

Spanoudaki, Katerina; Kampanis, Nikolaos

2015-04-01

Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater mathematical models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. However, most integrated surface water-groundwater models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated surface water-groundwater model IRENE (Spanoudaki et al., 2009; Spanoudaki, 2010) has been modified in order to simulate surface water-groundwater flow and salinity interactions in the coastal zone. IRENE, in its original form, couples the 3D shallow water equations to the equations describing 3D saturated groundwater flow of constant density. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection-diffusion equation describing the fate and transport of contaminants introduced in a 3D turbulent flow field to the partial differential equation describing the fate and transport of contaminants in 3D transient groundwater flow systems. The model has been further developed to include the effects of density variations on surface water and groundwater flow, while the already built-in solute transport capabilities are used to simulate salinity interactions. The refined model is based on the finite volume method using a cell-centred structured grid, providing thus flexibility and accuracy in simulating irregular boundary geometries. For addressing water resources management problems, simulation models are usually externally coupled with optimisation-based management models. However this usually requires a very large number of iterations between the optimisation and simulation models in order to obtain the optimal management solution. As an alternative approach, for improved computational efficiency, an Artificial Neural Network (ANN) is trained as an approximate simulator of IRENE. The trained ANN is then linked to a Genetic Algorithm (GA) based optimisation model for managing salinisation problems in the coastal zone. The linked simulation-optimisation model is applied to a hypothetical study area for performance evaluation. Acknowledgement The work presented in this paper has been funded by the Greek State Scholarships Foundation (IKY), Fellowships of Excellence for Postdoctoral Studies (Siemens Program), 'A simulation-optimization model for assessing the best practices for the protection of surface water and groundwater in the coastal zone', (2013 - 2015). References Spanoudaki, K., Stamou, A.I. and Nanou-Giannarou, A. (2009). Development and verification of a 3-D integrated surface water-groundwater model. Journal of Hydrology, 375 (3-4), 410-427. Spanoudaki, K. (2010). Integrated numerical modelling of surface water groundwater systems (in Greek). Ph.D. Thesis, National Technical University of Athens, Greece.

Calculation of molecular excitation rates

NASA Technical Reports Server (NTRS)

Flynn, George

1993-01-01

State-to-state collisional excitation rates for interstellar molecules observed by radio astronomers continue to be required to interpret observed line intensities in terms of local temperatures and densities. A problem of particular interest is collisional excitation of water which is important for modeling the observed interstellar masers. In earlier work supported by a different NASA Grant, excitation of water in collisions with He atoms was studied; after many years of successively more refined calculations that problem now seems to be well understood, and discrepancies with earlier experimental data for related (pressure broadening) phenomena are believed to reflect experimental errors. Because of interstellar abundances, excitation by H2, the dominant interstellar species, is much more important than excitation by He, although it has been argued that rates for excitation by these are similar. Under the current grant theoretical study of this problem has begun which is greatly complicated by the additional degrees of freedom which must be included both in determining the interaction potential and also in the molecular scattering calculation. We have now computed the interaction forces for nearly a thousand molecular geometries and are close to having an acceptable global fit to these points which is necessary for the molecular dynamics calculations. Also, extensive modifications have been made to the molecular scattering code, MOLSCAT. These included coding the rotational basis sets and coupling matrix elements required for collisions of an asymmetric top with a linear rotor. A new method for numerical solution of the coupled equations has been incorporated. Because of the long-ranged nature of the water-hydrogen interaction it is necessary to integrate the equations to rather large intermolecular separations, and the integration methods previously available in MOLSCAT are not ideal for such cases. However, the method used by Alexander in his HIBRIDON code is particularly suited for such cases. We have obtained this code and incorporated that part which solves the coupled differential equations as an option in the MOLSCAT program.

Interaction of Technology Adoption Constraints and Multi-level Policy Coherence at the Energy-Food Nexus

NASA Astrophysics Data System (ADS)

Gerst, M.; Cox, M. E.; Laser, M.; Locke, K. A.; Kapuscinski, A. R.

2017-12-01

Policy- and decision-making at the food-energy-water (FEW) nexus entails additional complexities due to the multi-objective nature of FEW socio-technical systems: policies and decisions meant to improve one facet of the nexus might be less beneficial, or even detrimental, to achieving goals for other facets. In addition, implementing policies and decisions may be more difficult due to increasing coordination required among stakeholders across each nexus facet. We highlight these issues in an economic, material/energy flow, and institutional assessment of dairy farms that produce power from anaerobic digestion of cow manure. This socio-technical system is an example of an integrated food-energy system (IFES), which co-produces food and energy. In the case of dairy farms, water is also a significant consideration because cow manure, if improperly managed, can negatively impact water bodies. Our assessment asks the questions (i) of whether or not adopting an IFES improves farm resilience under potential economic and environment futures and (ii) how decisions, policies, and information can best be tailored to the FEW nexus. Our study consists of semi-structured interviews of 60 farms split between the US states of New York and Vermont, both of which have enacted policies to encourage digester adoption. Each interview asks farmers about their material and energy flows, costs, and decision-making process for adopting (or not) an anaerobic digester. In addition, farmers are asked questions about challenges and barriers they might have faced and future drivers of change. Preliminary results highlight important interactions between policy and decision-making. Foremost, an analysis of policy cohesion shows that environmental objectives cross sectors and governance levels, as state-level greenhouse gas mitigation policies interact with federal-level nutrient management policies. This form of potential policy incoherence may introduce additional problems that hinder digester adoption and operation because technology options might be constrained and information needs may be too great for farmer's to consider adopting a digester.

Experimental and numerical modelling of surface water-groundwater flow and pollution interactions under tidal forcing

NASA Astrophysics Data System (ADS)

Spanoudaki, Katerina; Bockelmann-Evans, Bettina; Schaefer, Florian; Kampanis, Nikolaos; Nanou-Giannarou, Aikaterini; Stamou, Anastasios; Falconer, Roger

2015-04-01

Surface water and groundwater are integral components of the hydrologic continuum and the interaction between them affects both their quantity and quality. However, surface water and groundwater are often considered as two separate systems and are analysed independently. This separation is partly due to the different time scales, which apply in surface water and groundwater flows and partly due to the difficulties in measuring and modelling their interactions (Winter et al., 1998). Coastal areas in particular are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes. Accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands, for example, requires the use of integrated surface water-groundwater models. In the past few decades a large number of mathematical models and field methods have been developed in order to quantify the interaction between groundwater and hydraulically connected surface water bodies. Field studies may provide the best data (Hughes, 1995) but are usually expensive and involve too many parameters. In addition, the interpretation of field measurements and linking with modelling tools often proves to be difficult. In contrast, experimental studies are less expensive and provide controlled data. However, experimental studies of surface water-groundwater interaction are less frequently encountered in the literature than filed studies (e.g. Ebrahimi et al., 2007; Kuan et al., 2012; Sparks et al., 2013). To this end, an experimental model has been constructed at the Hyder Hydraulics Laboratory at Cardiff University to enable measurements to be made of groundwater transport through a sand embankment between a tidal water body such as an estuary and a non-tidal water body such as a wetland. The transport behaviour of a conservative tracer was studied for a constant water level on the wetland side of the embankment, while running a continuous tide on the coastal side. The integrated surface water-groundwater numerical model IRENE (Spanoudaki et al., 2009, Spanoudaki, 2010) was also used in the study, with the numerical model predictions being compared with experimental results, which provide a valuable database for model calibration and validation. IRENE couples the 3D, non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of hydrostatic pressure distribution, to the equations describing 3D saturated groundwater flow of constant density. The model uses the finite volume method with a cell-centered structured grid providing thus flexibility and accuracy in simulating irregular boundary geometries. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection-diffusion equation describing the fate and transport of contaminants introduced in a 3D turbulent flow field to the partial differential equation describing the fate and transport of contaminants in 3D transient groundwater flow systems. References Ebrahimi, K., Falconer, R.A. and Lin B. (2007). Flow and solute fluxes in integrated wetland and coastal systems. Environmental Modelling and Software, 22 (9), 1337-1348. Hughes, S.A. (1995). Physical Modelling and Laboratory Techniques in Coastal Engineering. World Scientific Publishing Co. Pte. Ltd., Singapore. Kuan, W.K., Jin, G., Xin, P., Robinson, C. Gibbes, B. and Li. L. (2012). Tidal influence on seawater intrusion in unconfined coastal aquifers. Water Resources Research, 48 (2), doi:10.1029/2011WR010678. Spanoudaki, K., Stamou, A.I. and Nanou-Giannarou, A. (2009). Development and verification of a 3-D integrated surface water-groundwater model. Journal of Hydrology, 375 (3-4), 410-427. Spanoudaki, K. (2010). Integrated numerical modelling of surface water groundwater systems (in Greek). Ph.D. Thesis, National Technical University of Athens, Greece. Sparks, T. D., Bockelmann-Evans, B. N. and Falconer, R. A. (2013). Laboratory Validation of an Integrated Surface Water- Groundwater Model. Journal of Water Resource and Protection, 5, 377-394. Winter, T.C., Harvey, J.W., Franke, O.L. and Alley, W.M., 1998. Groundwater and surface water - A single resource. USGS, Circular 1139.

On the Fluctuations that Order and Frustrate Liquid Water

NASA Astrophysics Data System (ADS)

Limmer, David Tyler

At ambient conditions, water sits close to phase coexistence with its crystal. More so than in many other materials, this fact is manifested in the fluctuations that maintain a large degree of local order in the liquid. These fluctuations and how they result in long-ranged order, or its absence, are emergent features of many interacting molecules. Their study therefore requires using the tools of statistical mechanics for their their systematic understanding. In this dissertation we develop such an understanding. In particular, we focus on collective behavior that emerges in liquid and solid water. At room temperatures, the thermophysical properties of water are quantified and rationalized with simple molecular models. A key feature of these models is the correct characterization of the competition between entropic forces of packing and the energetic preference for tetrahedral order. At cold temperatures, the properties of ice surfaces are studied with statistical field theory. The theory we develop for the long wavelength features of ice interfaces allows us to explain the existence of a premelting layer on the surface of ice and the stability of ice in confinement. In between these extremes, the dynamics of supercooled water are considered. A detailed theory for the early stages of coarsening is developed and used to explain the peculiar observation of a transient second liquid state of water. When coarsening dynamics are arrested, the result is the formation of a glassy states of water. We show that out-of-equilibrium the phase diagram for supercooled water exhibits a rich amount of structure, including a triple point between two glass phases of water and the liquid. At the end, we explore possible technological implications for the interplay between ordering and frustration in studies of water at metal interfaces.

Water use characteristics of black mangrove (Avicennia germinans) communities along an ecotone with marsh at a northern geographical limit

USGS Publications Warehouse

Krauss, Ken W.; McKee, Karen L.; Hester, Mark W.

2014-01-01

Mangroves are expanding into warm temperate-zone salt marsh communities in several locations globally. Although scientists have discovered that expansion might have modest effects on ecosystem functioning, water use characteristics have not been assessed relative to this transition. We measured early growing season sapflow (Js) and leaf transpiration (Tr) in Avicennia germinans at a latitudinal limit along the northern Gulf of Mexico (Louisiana, United States) under both flooded and drained states and used these data to scale vegetation water use responses in comparison with Spartina alterniflora. We discovered strong convergence when using either Js or Tr for determining individual tree water use, indicating tight connection between transpiration and xylem water movement in small Avicennia trees. When Tr data were combined with leaf area indices for the region with the use of three separate approaches, we determined that Avicennia stands use approximately 1·0–1·3 mm d–1 less water than Spartina marsh. Differences were only significant with the use of two of the three approaches, but are suggestive of net conservation of water as Avicennia expands into Spartina marshes at this location. Average Js for Avicennia trees was not influenced by flooding, but maximum Js was greater when sites were flooded. Avicennia and Spartina closest to open water (shoreline) used more water than interior locations of the same assemblages by an average of 1·3 mm d−1. Lower water use by Avicennia may indicate a greater overall resilience to drought relative to Spartina, such that aperiodic drought may interact with warmer winter temperatures to facilitate expansion of Avicennia in some years.

A Web-Based GIS for Reporting Water Usage in the High Plains Underground Water Conservation District

NASA Astrophysics Data System (ADS)

Jia, M.; Deeds, N.; Winckler, M.

2012-12-01

The High Plains Underground Water Conservation District (HPWD) is the largest and oldest of the Texas water conservation districts, and oversees approximately 1.7 million irrigated acres. Recent rule changes have motivated HPWD to develop a more automated system to allow owners and operators to report well locations, meter locations, meter readings, the association between meters and wells, and contiguous acres. INTERA, Inc. has developed a web-based interactive system for HPWD water users to report water usage and for the district to better manage its water resources. The HPWD web management system utilizes state-of-the-art GIS techniques, including cloud-based Amazon EC2 virtual machine, ArcGIS Server, ArcSDE and ArcGIS Viewer for Flex, to support web-based water use management. The system enables users to navigate to their area of interest using a well-established base-map and perform a variety of operations and inquiries against their spatial features. The application currently has six components: user privilege management, property management, water meter registration, area registration, meter-well association and water use report. The system is composed of two main databases: spatial database and non-spatial database. With the help of Adobe Flex application at the front end and ArcGIS Server as the middle-ware, the spatial feature geometry and attributes update will be reflected immediately in the back end. As a result, property owners, along with the HPWD staff, collaborate together to weave the fabric of the spatial database. Interactions between the spatial and non-spatial databases are established by Windows Communication Foundation (WCF) services to record water-use report, user-property associations, owner-area associations, as well as meter-well associations. Mobile capabilities will be enabled in the near future for field workers to collect data and synchronize them to the spatial database. The entire solution is built on a highly scalable cloud server to dynamically allocate the computational resources so as to reduce the cost on security and hardware maintenance. In addition to the default capabilities provided by ESRI, customizations include 1) enabling interactions between spatial and non-spatial databases, 2) providing role-based feature editing, 3) dynamically filtering spatial features on the map based on user accounts and 4) comprehensive data validation.

Using hydraulic modeling to simulate human interactions with water resources in an Omani irrigation system

NASA Astrophysics Data System (ADS)

Xanthopoulou, Themis; Ertsen, Maurits; Düring, Bleda; Kolen, Jan

2017-04-01

In the dry Southern Oman, more than a thousand years ago, a large water system that connected the mountain mass with the coastal region was constructed. Its length (up to 30 km) and the fact that the coastal region has a rich groundwater aquifer create confusion as to why the system was initially built. Nonetheless, it was abandoned a couple of centuries later only to be partially revived by small farming communities in the 17th to 18th century. The focus of our research is one of the irrigation systems that used the water conveyed from the large water system. Not much is known about these small irrigation systems functioning in the Wadi Al Jizzi of the greater Sohar region. There are no written records and we can only make guesses about the way the systems were managed based on ethnographical studies and the traditional Omani techniques. On the other hand, the good preservation state of the canals offers a great opportunity for hydraulic reconstruction of irrigation events. More than that, the material remains suggest and at the same time limit the ways in which humans interacted with the system and the water resources of the region. All irrigation activities and some daily activities had to be realized through the canal system and only if the canal system permits it these actions would have been feasible. We created a conceptual model of irrigation that includes the human agent and feedback mechanisms through hydraulics and then we simulated irrigation events using the Sobek software. Scenarios and sensibility analysis were used to address the unknown aspects of the system. Our research yielded insights about the way the farming community interacted with the larger water system, the levels of co-ordination and co-operation required for successful irrigation and the predisposition of conflict and power relations.

Hyperspectral remote sensing and long term monitoring reveal watershed-estuary ecosystem interactions

NASA Astrophysics Data System (ADS)

Hestir, E. L.; Schoellhamer, D. H.; Santos, M. J.; Greenberg, J. A.; Morgan-King, T.; Khanna, S.; Ustin, S.

2016-02-01

Estuarine ecosystems and their biogeochemical processes are extremely vulnerable to climate and environmental changes, and are threatened by sea level rise and upstream activities such as land use/land cover and hydrological changes. Despite the recognized threat to estuaries, most aspects of how change will affect estuaries are not well understood due to the poorly resolved understanding of the complex physical, chemical and biological processes and their interactions in estuarine systems. Remote sensing technologies such as high spectral resolution optical systems enable measurements of key environmental parameters needed to establish baseline conditions and improve modeling efforts. The San Francisco Bay-Delta is a highly modified estuary system in a state of ecological crisis due to the numerous threats to its sustainability. In this study, we used a combination of hyperspectral remote sensing and long-term in situ monitoring records to investigate how water clarity has been responding to extreme climatic events, anthropogenic watershed disturbances, and submerged aquatic vegetation (SAV) invasions. From the long-term turbidity monitoring record, we found that water clarity underwent significant increasing step changes associated with sediment depletion and El Nino-extreme run-off events. Hyperspectral remote sensing data revealed that invasive submerged aquatic pant species have facultative C3 and C4-like photosynthetic pathways that give them a competitive advantage under the changing water clarity conditions of the Bay-Delta system. We postulate that this adaptation facilitated the rapid expansion of SAV following the significant step changes in increasing water clarity caused by watershed disturbances and the 1982-1983 El Nino events. Using SAV maps from hyperspectral remote sensing, we estimate that SAV-water clarity feedbacks were responsible for 20-70% of the increasing water clarity trend in the Bay-Delta. Ongoing and future developments in airborne and global mapping hyperspectral satellite missions will enable full canopy-to-benthos characterization of estuarine ecosystems. When coupled with synoptic watershed measurements, these will improve understanding of watershed-estuary interactions for improved sustainable management.

The Odd Power of Dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Peng

2014-12-01

In ancient China, water has been regarded as one of the five vital components of life. It has been observed that water has many fascinating properties: water is ‘soft’ yet it can penetrate a hard rock; water is ‘pure’ yet it can tolerate other beings. Because of its unique properties, water is often associated with good quality and has been given the highest praise by Laozi in his book Tao Te Ching saying: the highest/best quality that one can have is being like water. However, little did people understand why and how water possesses such fascinating properties. Modern scientific developmentsmore » made people realize that the macroscopic liquid water is made of a large number of water molecules held together via a network of hydrogen bonds. And those wonderful properties of water are merely the macroscopic manifestations of the interactions between water molecules and other molecules. For example, the dissolving ability of water is due to the fact that the interaction between a water molecule and the other molecular species is stronger than the interactions among their own molecular species. In fact the interactions between any two molecules are governed by the same physics and are termed intermolecular interaction (or intermolecular forces in some literature, although technically ‘force’ is incorrect usage here). Although the very existence of the intermolecular interactions is easily proved, e.g. the mere presence of the solid phase of matter, and scientists today have recognized that the seemingly weak intermolecular interactions essentially hold the world together through a delicate and cooperative process, the theoretical understanding of various intermolecular interactions is still far from satisfactory. On the practical side, theoreticians need to balance computational cost and accuracy. Because of the relatively small magnitudes of the intermolecular interactions, errors that appear tiny compared to the usual chemical (covalent) bonding may change conclusions qualitatively. High-level ab initio methods including explicit description of electron correlation can achieve the desired accuracy at very high computational cost. (Chapter 5 and 6) However the cooperative network of hundreds of thousands of molecules that reflects the true power of intermolecular interactions cannot be modeled easily by ab initio methods. Deeper understanding of intermolecular interactions yields better theoretical models; better theoretical models facilitate and even deepen the understanding of intermolecular interactions. With the aforementioned motivation in mind, a significant portion of this dissertation is dedicated to developing a method to describe the intermolecular interactions accurately with affordable computational resources.« less

Statistical Mechanical Model for Adsorption Coupled with SAFT-VR Mie Equation of State.

PubMed

Franco, Luís F M; Economou, Ioannis G; Castier, Marcelo

2017-10-24

We extend the SAFT-VR Mie equation of state to calculate adsorption isotherms by considering explicitly the residual energy due to the confinement effect. Assuming a square-well potential for the fluid-solid interactions, the structure imposed by the fluid-solid interface is calculated using two different approaches: an empirical expression proposed by Travalloni et al. ( Chem. Eng. Sci. 65 , 3088 - 3099 , 2010 ), and a new theoretical expression derived by applying the mean value theorem. Adopting the SAFT-VR Mie ( Lafitte et al. J. Chem. Phys. , 139 , 154504 , 2013 ) equation of state to describe the fluid-fluid interactions, and solving the phase equilibrium criteria, we calculate adsorption isotherms for light hydrocarbons adsorbed in a carbon molecular sieve and for carbon dioxide, nitrogen, and water adsorbed in a zeolite. Good results are obtained from the model using either approach. Nonetheless, the theoretical expression seems to correlate better the experimental data than the empirical one, possibly implying that a more reliable way to describe the structure ensures a better description of the thermodynamic behavior.

The gating cycle of a K+ channel at atomic resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuello, Luis G.; Cortes, D. Marien; Perozo, Eduardo

C-type inactivation in potassium channels helps fine-tune long-term channel activity through conformational changes at the selectivity filter. Here, through the use of cross-linked constitutively open constructs, we determined the structures of KcsA’s mutants that stabilize the selectivity filter in its conductive (E71A, at 2.25 Å) and deep C-type inactivated (Y82A at 2.4 Å) conformations. These structural snapshots represent KcsA’s transient open-conductive (O/O) and the stable open deep C-type inactivated states (O/I), respectively. The present structures provide an unprecedented view of the selectivity filter backbone in its collapsed deep C-type inactivated conformation, highlighting the close interactions with structural waters and themore » local allosteric interactions that couple activation and inactivation gating. Together with the structures associated with the closed-inactivated state (C/I) and in the well-known closed conductive state (C/O), this work recapitulates, at atomic resolution, the key conformational changes of a potassium channel pore domain as it progresses along its gating cycle.« less

Hybrid Quantum Mechanics/Molecular Mechanics/Coarse Grained Modeling: A Triple-Resolution Approach for Biomolecular Systems.

PubMed

Sokkar, Pandian; Boulanger, Eliot; Thiel, Walter; Sanchez-Garcia, Elsa

2015-04-14

We present a hybrid quantum mechanics/molecular mechanics/coarse-grained (QM/MM/CG) multiresolution approach for solvated biomolecular systems. The chemically important active-site region is treated at the QM level. The biomolecular environment is described by an atomistic MM force field, and the solvent is modeled with the CG Martini force field using standard or polarizable (pol-CG) water. Interactions within the QM, MM, and CG regions, and between the QM and MM regions, are treated in the usual manner, whereas the CG-MM and CG-QM interactions are evaluated using the virtual sites approach. The accuracy and efficiency of our implementation is tested for two enzymes, chorismate mutase (CM) and p-hydroxybenzoate hydroxylase (PHBH). In CM, the QM/MM/CG potential energy scans along the reaction coordinate yield reaction energies that are too large, both for the standard and polarizable Martini CG water models, which can be attributed to adverse effects of using large CG water beads. The inclusion of an atomistic MM water layer (10 Å for uncharged CG water and 5 Å for polarizable CG water) around the QM region improves the energy profiles compared to the reference QM/MM calculations. In analogous QM/MM/CG calculations on PHBH, the use of the pol-CG description for the outer water does not affect the stabilization of the highly charged FADHOOH-pOHB transition state compared to the fully atomistic QM/MM calculations. Detailed performance analysis in a glycine-water model system indicates that computation times for QM energy and gradient evaluations at the density functional level are typically reduced by 40-70% for QM/MM/CG relative to fully atomistic QM/MM calculations.

Spectral induced polarization of the three-phase system CO2 - brine - sand under reservoir conditions

NASA Astrophysics Data System (ADS)

Börner, Jana H.; Herdegen, Volker; Repke, Jens-Uwe; Spitzer, Klaus

2017-01-01

The spectral complex conductivity of a water-bearing sand during interaction with carbon dioxide (CO2) is influenced by multiple, simultaneous processes. These processes include partial saturation due to the replacement of conductive pore water with CO2 and chemical interaction of the reactive CO2 with the bulk fluid and the grain-water interface. We present a laboratory study on the spectral induced polarization of water-bearing sands during exposure to and flow-through by CO2. Conductivity spectra were measured successfully at pressures up to 30 MPa and 80 °C during active flow and at steady-state conditions concentrating on the frequency range between 0.0014 and 100 Hz. The frequency range between 0.1 and 100 Hz turned out to be most indicative for potential monitoring applications. The presented data show that the impact of CO2 on the electrolytic conductivity may be covered by a model for pore-water conductivity, which depends on salinity, pressure and temperature and has been derived from earlier investigations of the pore-water phase. The new data covering the three-phase system CO2-brine-sand further show that chemical interaction causes a reduction of surface conductivity by almost 20 per cent, which could be related to the low pH-value in the acidic environment due to CO2 dissolution and the dissociation of carbonic acid. The quantification of the total CO2 effect may be used as a correction during monitoring of a sequestration in terms of saturation. We show that this leads to a correct reconstruction of fluid saturation from electrical measurements. In addition, an indicator for changes of the inner surface area, which is related to mineral dissolution or precipitation processes, can be computed from the imaginary part of conductivity. The low frequency range between 0.0014 and 0.1 Hz shows additional characteristics, which deviate from the behaviour at higher frequencies. A Debye decomposition approach is applied to isolate the feature dominating the data at low frequencies. We conclude from our study that electrical conductivity is not only a highly sensitive indicator for CO2 saturation in pore space. When it is measured in its full spectral and complex form it contains additional information on the chemical state of the system, which holds the potential of getting access to both saturation and interface properties with one monitoring method.

Probing the interactions between ionic liquids and water: experimental and quantum chemical approach.

PubMed

Khan, Imran; Kurnia, Kiki A; Mutelet, Fabrice; Pinho, Simão P; Coutinho, João A P

2014-02-20

For an adequate choice or design of ionic liquids, the knowledge of their interaction with other solutes and solvents is an essential feature for predicting the reactivity and selectivity of systems involving these compounds. In this work, the activity coefficient of water in several imidazolium-based ionic liquids with the common cation 1-butyl-3-methylimidazolium was measured at 298.2 K. To contribute to a deeper insight into the interaction between ionic liquids and water, COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies. The results showed good agreement between experimental and predicted activity coefficient of water in ionic liquids and that the interaction of water and ionic liquids was strongly influenced by the hydrogen bonding of the anion with water. Accordingly, the intensity of interaction of the anions with water can be ranked as the following: [CF3SO3](-) < [SCN](-) < [TFA](-) < Br(-) < [TOS](-) < Cl(-) < [CH3SO3](-) [DMP](-) < [Ac](-). In addition, fluorination and aromatization of anions are shown to reduce their interaction with water. The effect of temperature on the activity coefficient of water at infinite dilution was measured by inverse gas chromatography and predicted by COSMO-RS. Further analysis based on COSMO-RS provided information on the nature of hydrogen bonding between water and anion as well as the possibility of anion-water complex formation.

From hydration repulsion to dry adhesion between asymmetric hydrophilic and hydrophobic surfaces

PubMed Central

Kanduč, Matej; Netz, Roland R.

2015-01-01

Using all-atom molecular dynamics (MD) simulations at constant water chemical potential in combination with basic theoretical arguments, we study hydration-induced interactions between two overall charge-neutral yet polar planar surfaces with different wetting properties. Whether the water film between the two surfaces becomes unstable below a threshold separation and cavitation gives rise to long-range attraction, depends on the sum of the two individual surface contact angles. Consequently, cavitation-induced attraction also occurs for a mildly hydrophilic surface interacting with a very hydrophobic surface. If both surfaces are very hydrophilic, hydration repulsion dominates at small separations and direct attractive force contribution can—if strong enough—give rise to wet adhesion in this case. In between the regimes of cavitation-induced attraction and hydration repulsion we find a narrow range of contact angle combinations where the surfaces adhere at contact in the absence of cavitation. This dry adhesion regime is driven by direct surface–surface interactions. We derive simple laws for the cavitation transition as well as for the transition between hydration repulsion and dry adhesion, which favorably compare with simulation results in a generic adhesion state diagram as a function of the two surface contact angles. PMID:26392526

Gulf of Mexico Loop Current Interactions with the West Florida Shelf and its Influence on Harmful Algae Blooms

NASA Astrophysics Data System (ADS)

Liu, Y.; Weisberg, R. H.

2016-02-01

Interactions of the Loop Current (LC) system with the West Florida Shelf (WFS) are examined using 20+ years (1993 - 2015) of Ssalto/Duacs multi-mission altimetry data in the eastern Gulf of Mexico. Characteristic patterns of LC system sea surface height and surface geostrophic currents are extracted by an unsupervised neural network, Self-Organizing Map, along with their frequencies of occurrence. These current patterns suggest linkages with harmful algae bloom occurrences as recorded by in situ K. brevis cell counts. It is argued that LC system interactions with the shelf slope play an important role in WFS ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly important when the LC impinges on the southwest corner of the WFS slope, thereby impacting shallow water isobaths and setting the entire shelf circulation into motion. If such conditions persist, then deeper ocean waters with elevated nutrient content may broach the shelf and be transported landward. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology.

Free-energy analysis of the electron-density fluctuation in the quantum-mechanical/molecular-mechanical simulation combined with the theory of energy representation.

PubMed

Matubayasi, Nobuyuki; Takahashi, Hideaki

2012-01-28

The relationship is investigated for QM/MM (quantum-mechanical/molecular-mechanical) systems between the fluctuations of the electronic state of the QM subsystem and of the solvation effect due to the QM-MM interaction. The free-energy change due to the electron-density fluctuation around its average is highlighted, and is evaluated through an approximate functional formulated in terms of distribution functions of the many-body coupling (pairwise non-additive) part of the QM-MM interaction energy. A set of QM/MM simulations are conducted in MM water solvent for QM water solute in ambient and supercritical conditions and for QM glycine solute in the neutral and zwitterionic forms. The variation of the electronic distortion energy of the QM solute in the course of QM/MM simulation is then shown to be compensated by the corresponding variation of the free energy of solvation. The solvation free energy conditioned by the electronic distortion energy is further analyzed with its components. It is found that the many-body contribution is essentially equal between the free energy and the average sum of solute-solvent interaction energy. © 2012 American Institute of Physics

Assessing fit, interplay, and scale: Aligning governance and information for improved water management in a changing climate

NASA Astrophysics Data System (ADS)

Kirchhoff, C.; Dilling, L.

2011-12-01

Water managers have long experienced the challenges of managing water resources in a variable climate. However, climate change has the potential to reshape the experiential landscape by, for example, increasing the intensity and duration of droughts, shifting precipitation timing and amounts, and changing sea levels. Given the uncertainty in evaluating potential climate risks as well as future water availability and water demands, scholars suggest water managers employ more flexible and adaptive science-based management to manage uncertainty (NRC 2009). While such an approach is appropriate, for adaptive science-based management to be effective both governance and information must be concordant across three measures: fit, interplay and scale (Young 2002)(Note 1). Our research relies on interviews of state water managers and related experts (n=50) and documentary analysis in five U.S. states to understand the drivers and constraints to improving water resource planning and decision-making in a changing climate using an assessment of fit, interplay and scale as an evaluative framework. We apply this framework to assess and compare how water managers plan and respond to current or anticipated water resource challenges within each state. We hypothesize that better alignment between the data and management framework and the water resource problem improves water managers' facility to understand (via available, relevant, timely information) and respond appropriately (through institutional response mechanisms). In addition, better alignment between governance mechanisms (between the scope of the problem and identified appropriate responses) improves water management. Moreover, because many of the management challenges analyzed in this study concern present day issues with scarcity brought on by a combination of growth and drought, better alignment of fit, interplay, and scale today will enable and prepare water managers to be more successful in adapting to climate change impacts in the long-term. Note 1: For the purposes of this research, the problem of fit deals with the level of concordance between the natural and human systems while interplay involves how institutional arrangements interact both horizontally and vertically. Lastly, scale considers both spatial and temporal alignment of the physical systems and management structure. For example, to manage water resources effectively in a changing climate suggests having information that informs short-term and long-term changes and having institutional arrangements that seek understanding across temporal scales and facilitate responses based on information available (Young 2002).

Hydrostatic pressure effect on PNIPAM cononsolvency in water-methanol solutions.

PubMed

Pica, Andrea; Graziano, Giuseppe

2017-12-01

When methanol is added to water at room temperature and 1atm, poly (N-isopropylacrylamide), PNIPAM, undergoes a coil-to-globule collapse transition. This intriguing phenomenon is called cononsolvency. Spectroscopic measurements have shown that application of high hydrostatic pressure destroys PNIPAM cononsolvency in water-methanol solutions. We have developed a theoretical approach that identifies the decrease in solvent-excluded volume effect as the driving force of PNIPAM collapse on increasing the temperature. The same approach indicates that cononsolvency, at room temperature and P=1atm, is caused by the inability of PNIPAM to make all the attractive energetic interactions that it could be engaged in, due to competition between water and methanol molecules. The present analysis suggests that high hydrostatic pressure destroys cononsolvency because the coil state becomes more compact, and the quantity measuring PNIPAM-solvent attractions increases in magnitude due to the solution density increase, and the ability of small water molecules to substitute methanol molecules on PNIPAM surface. Copyright © 2017 Elsevier B.V. All rights reserved.

Entropic factors provide unusual reactivity and selectivity in epoxide-opening reactions promoted by water

PubMed Central

Byers, Jeffery A.; Jamison, Timothy F.

2013-01-01

Despite the myriad of selective enzymatic reactions that occur in water, chemists have rarely capitalized on the unique properties of this medium to govern selectivity in reactions. Here we report detailed mechanistic investigations of a water-promoted reaction that displays high selectivity for what is generally a disfavored product. A combination of structural and kinetic data indicates not only that synergy between substrate and water suppresses undesired pathways but also that water promotes the desired pathway by stabilizing charge in the transition state, facilitating proton transfer, doubly activating the substrate for reaction, and perhaps most remarkably, reorganizing the substrate into a reactive conformation that leads to the observed product. This approach serves as an outline for a general strategy of exploiting solvent-solute interactions to achieve unusual reactivity in chemical reactions. These findings may also have implications in the biosynthesis of the ladder polyether natural products, such as the brevetoxins and ciguatoxins. PMID:24046369