Science.gov

Sample records for liquid water polymorphism

  1. Liquid polymorphism, order-disorder transitions and anomalous a Monte Carlo study of the Bell-Lavis model for water

    E-print Network

    Barbosa, Marcia C. B.

    APS/PRE Liquid polymorphism, order-disorder transitions and anomalous behavior: a Monte Carlo study for liquid water is investigated through numerical simulations. The lattice- gas model on a triangular and a loosely bonded high density phase. We show that the model liquid-liquid transition is continuous

  2. Investigating the dependence of polymorphic liquid-liquid transitions on the concentration of amphiphiles in water

    NASA Astrophysics Data System (ADS)

    Mirgorod, Yu. A.

    2015-01-01

    A way of identifying polymorphic transitions via the hydrolysis of S-decylisothiuronium chloride and other properties of water in solutions of amphiphiles is described. Features of amphiphile transitions (smoothness, micelle bistability, solubilization hysteresis, the autooscillation of micelles, and fluctuations in the extensive properties of a water and micelle nanosystem ensemble) are discussed.

  3. Liquid polymorphism and density anomaly in a three-dimensional associating lattice gas

    E-print Network

    Barbosa, Marcia C. B.

    Liquid polymorphism and density anomaly in a three-dimensional associating lattice gas Mauricio the presence of two liquid phase, two critical points and density anomaly. PACS numbers: 1 #12;I. INTRODUCTION Water is an anomalous substance in many respects. Most liquids contract upon cooling

  4. Cloud Liquid Water Measurements

    E-print Network

    Delene, David J.

    Water Content Probe Coil is heated to given temperature ~185 °C. Coil supplies energy in the form of Vaporization · cw - Specific Heat of Water · Tv - Boiling Temperature of Water · Ta ­ Ambient Temperature #12 of Vaporization · cw - Specific Heat of Water · Tv ­ Water Boiling Temperature Solve for Liquid Water Content · P

  5. Liquid polymorphism, order-disorder transitions and anomalous behavior: A Monte Carlo study of the Bell-Lavis model for water

    NASA Astrophysics Data System (ADS)

    Fiore, Carlos E.; Szortyka, Marcia M.; Barbosa, Marcia C.; Henriques, Vera B.

    2009-10-01

    The Bell-Lavis model for liquid water is investigated through numerical simulations. The lattice-gas model on a triangular lattice presents orientational states and is known to present a highly bonded low density phase and a loosely bonded high density phase. We show that the model liquid-liquid transition is continuous, in contradiction with mean-field results on the Husimi cactus and from the cluster variational method. We define an order parameter which allows interpretation of the transition as an order-disorder transition of the bond network. Our results indicate that the order-disorder transition is in the Ising universality class. Previous proposal of an Ehrenfest second order transition is discarded. A detailed investigation of anomalous properties has also been undertaken. The line of density maxima in the HDL phase is stabilized by fluctuations, absent in the mean-field solution.

  6. Water: The Strangest Liquid

    SciTech Connect

    Nilsson, Anders

    2009-02-24

    Water, H2O, is familiar to everyone - it shapes our bodies and our planet. But despite its abundance, water has remained a mystery, exhibiting many strange properties that are still not understood. Why does the liquid have an unusually large capacity to store heat? And why is it denser than ice? Now, using the intense X-ray beams from particle accelerators, investigations into water are leading to fundamental discoveries about the structure and arrangement of water molecules. This lecture will elucidate the many mysteries of water and discuss current studies that are revolutionizing the way we see and understand one of the most fundamental substances of life.

  7. Supercooled liquid water Estimation Tool

    Energy Science and Technology Software Center (ESTSC)

    2012-05-04

    The Cloud Supercooled liquid water Estimation Tool (SEET) is a user driven Graphical User Interface (GUI) that estimates cloud supercooled liquid water (SLW) content in terms of vertical column and total mass from Moderate resolution Imaging Supercooled liquid water Estimation Tool Spectroradiometer (MODIS) spatially derived cloud products and realistic vertical cloud parameterizations that are user defined. It also contains functions for post-processing of the resulting data in tabular and graphical form.

  8. Liquid Polymorphism and Double Criticality in a Lattice Gas Vera B. Henriques,1,

    E-print Network

    Barbosa, Marcia C. B.

    Liquid Polymorphism and Double Criticality in a Lattice Gas Model Vera B. Henriques,1, Nara diagrams of a simple model for an associating liquid proposed previously. Our two-dimensional lattice model decreases, a smooth disappearance of the double criticality occurs. Possible connections to liquid-liquid

  9. Nonamphiphilic assembly in water: polymorphic nature, thread structure, and thermodynamic incompatibility.

    PubMed

    Wu, Lei; Lal, Jyotsana; Simon, Karen A; Burton, Erik A; Luk, Yan-Yeung

    2009-06-01

    Self-assembly of large quantities of entirely water-soluble molecules is entropically challenging. In this work, we describe the design and synthesis of water-soluble aromatic (dichromonyl) molecules that can form nonamphiphilic assemblies and the so-called chromonic liquid crystal phase in water. We discover a new molecule, 5'DSCG-diviol, that exhibits a large birefringent phase, and we show that the formation of this unique class of nonamphiphilic lyotropic liquid crystal shares enormous similarity to the polymorphism observed for crystal formation. Small-angle neutron scattering (SANS) revealed a concentration-independent rod-shaped assembly at concentrations below and above the formation of liquid crystal phase. Adding a small percentage of monoanionic aromatic molecules to the liquid crystal resulted in the elimination of the liquid crystal phase, but addition of dianionic aromatic molecules retained the liquid crystal phase. Together, these results suggest a new assembly structure for nonamphiphilic molecules in water, which is comprised of long threads of small molecules connected by salt bridges stacked over aromatic groups, with the molecular threads heavily hydrated with solvent water. Furthermore, mixing molecules with different structures can result in new liquid crystalline materials, or in segregation of the molecules into different solvation volumes, each of which contains only one type of molecule. The unusual thermodynamic incompatibility of entirely water-soluble molecules also supports the model of molecular threads, in which two polymer-like assemblies do not mix. PMID:19422237

  10. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  11. Static heterogeneities in liquid water

    NASA Astrophysics Data System (ADS)

    Stanley, H. Eugene; Buldyrev, Sergey V.; Giovambattista, Nicolas

    2004-10-01

    The thermodynamic behavior of water seems to be closely related to static heterogeneities. These static heterogeneities are related to the local structure of water molecules, and when properly characterized, may offer an economical explanation of thermodynamic data. The key feature of liquid water is not so much that the existence of hydrogen bonds, first pointed out by Linus Pauling, but rather the local geometry of the liquid molecules is not spherical or oblong but tetrahedral. In the consideration of static heterogeneities, this local geometry is critical. Recent experiments suggested more than one phase of amorphous solid water, while simulations suggest that one of these phases is metastable with respect to another, so that in fact there are only two stable phases.

  12. Aqua Reticulata: topology of liquid water networks

    E-print Network

    Hyde, Stephen

    at oxygen vertices (the net nodes), with four edges at each vertex. second, liquid water is a mixture of two145 VI Aqua Reticulata: topology of liquid water networks Stephen T. Hyde department of Applied explored the notion of structure at the atomic scale in liquid water.1 While not the earliest attempt

  13. Polymorphs

    E-print Network

    Prankerd, Richard

    2006-10-26

    the higher melting point and the higher heat capacity (at fixed T), they are enantiotropically related ? The Cp value is more difficult to measure From Lohani and Grant, Thermodynamics of polymorphs, in Hilfiker, Polymorphism, Wiley-VCH (2005) Ch. 2 9 17....vcp.monash.edu.au Polymorphism Richard J. Prankerd, PhD Department of Pharmaceutics Faculty of Pharmacy Monash University Melbourne AUSTRALIA www.vcp.monash.edu.au Solid State Stability 2 Seminar overview ? Literature ? Definition ? Thermodynamics ? Importance in pharmaceuticals...

  14. II. Properties of Water 1. Ice and Liquid water structure

    E-print Network

    Frey, Terry

    .6: Five Critical Properties of Water 1. Ice and liquid water structure Temperature 0°C Temperature > 0°C water ·Water is liquid at a relatively high temperature > 0°C required to raise temperature of 1 g of water by 1°C (1 calorie, 1 cal) Large bodies of water stabilize

  15. The Boson peak in confined water: An experimental investigation of the liquid-liquid phase transition hypothesis

    NASA Astrophysics Data System (ADS)

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Wang, Zhe; Chen, Sow-Hsin

    2015-10-01

    The Boson peak (BP) of deeply cooled confined water is studied by using inelastic neutron scattering (INS) in a large interval of the ( P, T) phase plane. By taking into account the different behavior of such a collective vibrational mode in both strong and fragile glasses as well as in glass-forming materials, we were able to determine the Widom line that characterizes supercooled bulk water within the frame of the liquid-liquid phase transition (LLPT) hypothesis. The peak frequency and width of the BP correlated with the water polymorphism of the LLPT scenario, allowing us to distinguish the "low-density liquid" (LDL) and "high-density liquid" (HDL) phases in deeply cooled bulk water.Moreover, the BP properties afford a further confirmation of theWidom line temperature T W as the ( P, T) locus in which the local structure of water transforms from a predominately LDL form to a predominately HDL form.

  16. Geomorphologic evidence for liquid water

    USGS Publications Warehouse

    Masson, P.; Carr, M.H.; Costard, F.; Greeley, R.; Hauber, E.; Jaumann, R.

    2001-01-01

    Besides Earth, Mars is the only planet with a record of resurfacing processes and environmental circumstances that indicate the past operation of a hydrologic cycle. However the present-day conditions on Mars are far apart of supporting liquid water on the surface. Although the large-scale morphology of the Martian channels and valleys show remarkable similarities with fluid-eroded features on Earth, there are major differences in their size, small-scale morphology, inner channel structure and source regions indicating that the erosion on Mars has its own characteristic genesis and evolution. The different landforms related to fluvial, glacial and periglacial activities, their relations with volcanism, and the chronology of water-related processes, are presented.

  17. Density Fluctuations in Liquid Water

    NASA Astrophysics Data System (ADS)

    English, Niall J.; Tse, John S.

    2011-01-01

    The density distributions and fluctuations in grids of varying size in liquid water at ambient pressure, both above the freezing point and in the supercooled state, are analyzed from the trajectories obtained from large-scale molecular dynamics simulations. It is found that the occurrence of low- and high-density regions (LDL and HDL) is transient and their respective residence times are dependent on the size of the simulated system. The spatial extent of density-density correlation is found to be within 7 Å or less. The temporal existence of LDL and HDL arises as a result of natural density fluctuations of an equilibrium system. The density of bulk water at ambient conditions is homogenous.

  18. Liquid Water on Early Mars

    NASA Technical Reports Server (NTRS)

    Davis, Wanda L.; McKay, Christopher P.

    1994-01-01

    We have used a simple climate model to determine the duration of liquid water habitats on early Mars following up on the previous work of McKay and Davis. We used the weathering model of Pollack et al. to compute the pressure and temperature evolution of the atmosphere. We included the variability of the solar luminosity. Recent results which have considered the influence of CO2 condensation suggest that Mars could not have been kept warm (above 0 C) with only a dense CO2 atmosphere. New stellar evolution theories have suggested a more massive early sun to explain the lithium depletion in the sun and predict a warmer climate for early Mars. We have therefore modified the model of McKay and Davis to include the effects of CO2 condensation and the effect of a more massive early sun. Here we present the results of these additional effects on the duration of liquid water habitats on early Mars. We find that the increased luminosity suggested for the early sun when mass loss is taken into account can provide a climate on early Mars that results in fluvial features existing over 500 million years.

  19. Water: A Complex Liquid Marcia C. Barbosa

    E-print Network

    Liu, I-Shih

    Water: A Complex Liquid Marcia C. Barbosa #12;What is the mistery? Why should we care? What;What is the mistery? M. Chaplin, Water structure and science (2010). Such a simple liquid 69 anomalies;Compressibility water: Speedy, Angell, JCP 65, 351 (76) toluene: Minassian, Bouzar, Alba, JPC 92, 487 (88) KT

  20. Proton Electrodynamics in Liquid Water

    E-print Network

    A. A. Volkov; V. G. Artemov; A. V. Pronin

    2013-02-20

    The dielectric spectrum of liquid water, $10^{4} - 10^{11}$ Hz, is interpreted in terms of diffusion of charges, formed as a result of self-ionization of H$_{2}$O molecules. This approach explains the Debye relaxation and the dc conductivity as two manifestations of this diffusion. The Debye relaxation is due to the charge diffusion with a fast recombination rate, $1/\\tau_{2}$, while the dc conductivity is a manifestation of the diffusion with a much slower recombination rate, $1/\\tau_{1}$. Applying a simple model based on Brownian-like diffusion, we find $\\tau_{2} \\simeq 10^{-11}$ s and $\\tau_{1} \\simeq 10^{-6}$ s, and the concentrations of the charge carriers, involved in each of the two processes, $N_{2} \\simeq 5 \\times 10^{26}$ m$^{-3}$ and $N_{1} \\simeq 10^{14}$ m$^{-3}$. Further, we relate $N_{2}$ and $N_{1}$ to the total concentration of H$_{3}$O$^{+}$--OH$^{-}$ pairs and to the pH index, respectively, and find the lifetime of a single water molecule, $\\tau_{0} \\simeq 10^{-9}$ s. Finally, we show that the high permittivity of water results mostly from flickering of separated charges, rather than from reorientations of intact molecular dipoles.

  1. Spin-liquid polymorphism in a correlated electron system on the threshold of superconductivity.

    PubMed

    Zaliznyak, Igor; Savici, Andrei T; Lumsden, Mark; Tsvelik, Alexei; Hu, Rongwei; Petrovic, Cedomir

    2015-08-18

    We report neutron scattering measurements which reveal spin-liquid polymorphism in an "11" iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe(1-x)(S,Se)(x). We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. Our results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike. PMID:26240327

  2. Spin liquid polymorphism in a correlated electron system on the threshold of superconductivity

    DOE PAGESBeta

    Zalinznyak, Igor; Savici, Andrei T.; Lumsden, Mark D.; Tsvelik, Alexei; Hu, Rongwei; Petrovic, Cedomir

    2015-08-18

    We report neutron scattering measurements which reveal spin-liquid polymorphism in an “11” iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We also observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other ismore »the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid–liquid phase transformation between these states, in the electronic spin system of FeTe1-x(S,Se)x. We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. These results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike.« less

  3. Proton Electrodynamics in Liquid Water

    E-print Network

    Volkov, A A; Pronin, A V

    2013-01-01

    The dielectric spectrum of liquid water, $10^{4} - 10^{11}$ Hz, is interpreted in terms of diffusion of charges, formed as a result of self-ionization of H$_{2}$O molecules. This approach explains the Debye relaxation and the dc conductivity as two manifestations of this diffusion. The Debye relaxation is due to the charge diffusion with a fast recombination rate, $1/\\tau_{2}$, while the dc conductivity is a manifestation of the diffusion with a much slower recombination rate, $1/\\tau_{1}$. Applying a simple model based on Brownian-like diffusion, we find $\\tau_{2} \\simeq 10^{-11}$ s and $\\tau_{1} \\simeq 10^{-6}$ s, and the concentrations of the charge carriers, involved in each of the two processes, $N_{2} \\simeq 5 \\times 10^{26}$ m$^{-3}$ and $N_{1} \\simeq 10^{14}$ m$^{-3}$. Further, we relate $N_{2}$ and $N_{1}$ to the total concentration of H$_{3}$O$^{+}$--OH$^{-}$ pairs and to the pH index, respectively, and find the lifetime of a single water molecule, $\\tau_{0} \\simeq 10^{-9}$ s. Finally, we show that ...

  4. PH-Induced Nanosegregation of Ritonavir to Lyotropic Liquid Crystal of Higher Solubility Than Crystalline Polymorphs

    SciTech Connect

    Rodriguez-Spong, B.; Acciacca, A.; Fleisher, D.; Rodriguez-Hornedo, N.

    2009-05-27

    Birefringent spherical vesicles of ritonavir (RTV) are formed by increasing the pH of aqueous solutions from 1 to 3 or to 7 and by addition of water to ethanol solutions at room temperature. Increasing the pH creates supersaturation levels of 30--400. Upon this change in pH, the solutions become translucent, implying that some kind of RTV assembly was formed. Small spherical vesicles of narrow size distribution are detectable only after a few hours by optical microscopy. The vesicles show similar X-ray diffraction patterns and differential scanning calorimetry (DSC) behavior to amorphous RTV prepared by melt-quenching crystalline RTV. Examination by polarized optical microscopy suggests that these are lyotropic liquid crystalline (LLC) assemblies. Small-angle X-ray scattering and synchrotron X-ray diffraction further support the presence of orientational order that is associated with a nematic structure. RTV self-organizes into various phases as a result of the supersaturation created in aqueous solutions. The LLC vesicles do not fuse but slowly transform to the polymorphs of RTV (in days), Form I and finally Form II. Amorphous RTV in aqueous suspension also undergoes a transformation to a mesophase of similar morphology. Transformation pathways are consistent with measured dissolution rates and solubilities: amorphous > LLC >> Form I > Form II. The dissolution and solubility of LLC is slightly lower than that of the amorphous phase and about 20 times higher than that of Form II. RTV also self-assembles at the air/water interface as indicated by the decrease in surface tension of aqueous solutions. This behavior is similar to that of amphiphilic molecules that induce LLC formation.

  5. Electrokinetic Power Generation from Liquid Water Microjets

    SciTech Connect

    Duffin, Andrew M.; Saykally, Richard J.

    2008-02-15

    Although electrokinetic effects are not new, only recently have they been investigated for possible use in energy conversion devices. We have recently reported the electrokinetic generation of molecular hydrogen from rapidly flowing liquid water microjets [Duffin et al. JPCC 2007, 111, 12031]. Here, we describe the use of liquid water microjets for direct conversion of electrokinetic energy to electrical power. Previous studies of electrokinetic power production have reported low efficiencies ({approx}3%), limited by back conduction of ions at the surface and in the bulk liquid. Liquid microjets eliminate energy dissipation due to back conduction and, measuring only at the jet target, yield conversion efficiencies exceeding 10%.

  6. Global cloud liquid water path simulations

    SciTech Connect

    Lemus, L.; Rikus, L.; Martin, C.; Platt, R.

    1997-01-01

    A new parameterization of cloud liquid water and ice content has been included in the Bureau of Meteorology Global Assimilation and Prediction System. The cloud liquid water content is derived from the mean cloud temperatures in the model using an empirical relationship based on observations. The results from perpetual January and July simulations are presented and show that the total cloud water path steadily decreases toward high latitudes, with two relative maxima at midlatitudes and a peak at low latitudes. To validate the scheme, the simulated fields need to be processed to produce liquid water paths that can be directly compared with the corresponding field derived from Special Sensor Microwave/Imager (SSM/I) data. This requires the identification of cloud ice water content within the parameterization and a prescription to account for the treatment of strongly precipitating subgrid-scale cloud. The resultant cloud liquid water paths agree qualitatively with the SSM/I data but show some systematic errors that are attributed to corresponding errors in the model`s simulation of cloud amounts. Given that a more quantitative validation requires substantial improvement in the model`s diagnostic cloud scheme, the comparison with the SSM/I data indicates that the cloud water path, derived from the cloud liquid water content parameterization introduced in this paper, is consistent with the observations and can be usefully incorporated in the prediction system. 40 refs., 11 figs., 1 tab.

  7. Evidence for Liquid Water on Comets

    NASA Technical Reports Server (NTRS)

    Sheldon, Robert; Hoover, Richard

    2005-01-01

    We have reexamined the arguments for the existence of liquid water on comets, and believe that recent cometary flybys along with pre-Giotto data support its presence on short-period comets. Liquid water would affect cometary dynamics, leaving distinct signatures in precession, orbital dynamics, and potential splitting of comets. Liquid water geysers would affect cometary atmosphere, dust evolution, and non-gravitational forces that perturb the orbit. Liquid water would affect the composition of both the interior and exterior of the comet, producing geologic effects consistent with recent flyby photographs. And most importantly, liquid water suppork the growth of lifeforms, which would make a comet a biofriendly incubator for interplanetary transport. The major objection against liquid water is the necessity of a pressure vessel to prevent sublimation into space. We discuss how such a pressure vessel could naturally evolve as a pristine comet makes its first journey inside the orbit of Mars, and suggest that this type of vessel was observed by Giotto, Deep Space I, and Stardust.

  8. Water in Olivine and its High-Pressure Polymorphs

    NASA Astrophysics Data System (ADS)

    Thomas, S. M.; Jacobsen, S. D.; Bina, C. R.; Reichart, P.; Moser, M.; Dollinger, G.; Hauri, E. H.

    2014-12-01

    Theory and high-pressure experiments imply a significant water storage capacity of nominally anhydrous minerals (NAMs), such as olivine, wadsleyite and ringwoodite, composing the Earth's upper mantle and transition zone to a depth of 660 km. The presence of water, dissolved as OH into such nominally anhydrous high-pressure silicates, notably influences phase relations, melting behavior, conductivity, elasticity, viscosity and rheology. The first direct evidence for hydration of the transition zone has recently been reported by Pearson et al. (2014) and Schmandt et al. (2014). Knowledge of absolute water contents in NAMs is essential for modeling the Earth's interior water cycle. To take advantage of IR spectroscopy as highly sensitive water quantification tool, mineral-specific absorption coefficients are required. Such calibration constants can be derived from hydrogen concentrations determined by independent techniques, such as secondary ion mass spectrometry (SIMS), Raman spectroscopy or proton-proton(pp)-scattering. Broad beam pp-scattering has been performed on double-polished mm-sized mineral platelets (Thomas et al. 2008), but until recently analysis was not feasible for smaller samples synthetized in high-pressure apparati. Here we present first results from pp-scattering microscopy studies on ?m-sized single crystals of hydrous olivine, wadsleyite and ringwoodite, which were synthesized at various pressure-temperature conditions in a multi-anvil press. The method allows us to quantify 3D distributions of atomic hydrogen in ?m dimensions. These self-calibrating measurements were carried out at the nuclear microprobe SNAKE at the Munich tandem accelerator lab using a 25 MeV proton microbeam. We provide hydrogen depth-profiles, hydrogen maps and H2O concentrations. Pp-scattering data and results from independent Raman and SIMS analyses are in good agreement. Water contents for a set of high-pressure polymorphs with varying Fe-concentrations range from 0.8 wt% to 2.5 wt% H2O. From experimental data for Fo83, Fo87, Fo90 and Fo100 compositions we calculate mineral-specific absorption coefficients for the quantification of H2O using IR-spectroscopy, compare them with previously estimated values and discuss IR calibrations for major phases of the Earth's mantle.

  9. Properties of Water Confined in Ionic Liquids

    PubMed Central

    Saihara, Koji; Yoshimura, Yukihiro; Ohta, Soichi; Shimizu, Akio

    2015-01-01

    The varying states of water confined in the nano-domain structures of typical room temperature ionic liquids (ILs) were investigated by 1H NMR and by measurements of self-diffusion coefficients while systematically varying the IL cations and anions. The NMR peaks for water in BF4-based ILs were clearly split, indicating the presence of two discrete states of confined water (H2O and HOD). Proton and/or deuterium exchange rate among the water molecules was very slowly in the water-pocket. Notably, no significant changes were observed in the chemical shifts of the ILs. Self-diffusion coefficient results showed that water molecules exhibit a similar degree of mobility, although their diffusion rate is one order of magnitude faster than that of the IL cations and anions. These findings provide information on a completely new type of confinement, that of liquid water in soft matter. PMID:26024339

  10. Liquid Water Oceans in Ice Giants

    E-print Network

    Sloane J. Wiktorowicz; Andrew P. Ingersoll

    2006-09-26

    Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean existing in the hydrogen-rich region between the cloud tops and deep interior. Starting from an assumed temperature at a given upper tropospheric pressure (the photosphere), we follow a moist adiabat downward. The mixing ratio of water to hydrogen in the gas phase is small in the photosphere and increases with depth. The mixing ratio in the condensed phase is near unity in the photosphere and decreases with depth; this gives two possible outcomes. If at some pressure level the mixing ratio of water in the gas phase is equal to that in the deep interior, then that level is the cloud base. Alternately, if the mixing ratio of water in the condensed phase reaches that in the deep interior, then the surface of a liquid ocean will occur. We find that Neptune is both too warm (photospheric temperature too high) and too dry (mixing ratio of water in the deep interior too low) for liquid oceans to exist at present. To have a liquid ocean, Neptune's deep interior water to gas ratio would have to be higher than current models allow, and the density at 19 kbar would have to be ~ 0.8 g/cm^3. Such a high density is inconsistent with gravitational data obtained during the Voyager flyby. As Neptune cools, the probability of a liquid ocean increases. Extrasolar "hot Neptunes," which presumably migrate inward toward their parent stars, cannot harbor liquid water oceans unless they have lost almost all of the hydrogen and helium from their deep interiors.

  11. Liquid water: The helical perspective of structure

    NASA Astrophysics Data System (ADS)

    Lozynski, Marek

    2015-07-01

    The structure of water, especially the bulk liquid, is a fundamental question. We show that the infinite network of perfectly tetragonal oxygen atoms in ice Ih can be converted into the helical geometry, retaining the four-fold connectivity but being non-tetrahedral with respect to neighboring oxygen atoms. Thus, liquid water appears as a racemic mixture of two types of discrete, helical clusters of water molecules joined tightly together by two types of hydrogen bonds, which are very similar in all cluster entities.

  12. Liquid chromatographic determination of water

    DOEpatents

    Fortier, N.E.; Fritz, J.S.

    1990-11-13

    A sensitive method for the determination of water in the presence of common interferences is presented. The detection system is based on the effect of water on the equilibrium which results from the reaction aryl aldehydes, such as cinnamaldehyde and methanol in the eluent to form cinnamaldehyde dimethylacetal, plus water. This equilibrium is shifted in a catalytic atmosphere of a hydrogen ion form past column reactor. The extent of the shift and the resulting change in absorbance are proportional to the amount of water present. 1 fig.

  13. Liquid chromatographic determination of water

    DOEpatents

    Fortier, Nancy E. (Fairfield, OH); Fritz, James S. (Ames, IA)

    1990-11-13

    A sensitive method for the determination of water in the presence of common interferences is presented. The detection system is based on the effect of water on the equilibrium which results from the reaction aryl aldehydes, such as cinnamaldehyde and methanol in the eluent to form cinnamaldehyde dimethylacetal, plus water. This equilibrium is shifted in a catalytic atmosphere of a hydrogen ion form past column reactor. The extent of the shift and the resulting change in absorbance are proportional to the amount of water present.

  14. Liquid Water Oceans in Ice Giants

    NASA Technical Reports Server (NTRS)

    Wiktorowicz, Sloane J.; Ingersoll, Andrew P.

    2007-01-01

    Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean existing in the hydrogen-rich region between the cloud tops and deep interior. Starting from an assumed temperature at a given upper tropospheric pressure (the photosphere), we follow a moist adiabat downward. The mixing ratio of water to hydrogen in the gas phase is small in the photosphere and increases with depth. The mixing ratio in the condensed phase is near unity in the photosphere and decreases with depth; this gives two possible outcomes. If at some pressure level the mixing ratio of water in the gas phase is equal to that in the deep interior, then that level is the cloud base. The gas below the cloud base has constant mixing ratio. Alternately, if the mixing ratio of water in the condensed phase reaches that in the deep interior, then the surface of a liquid ocean will occur. Below this ocean surface, the mixing ratio of water will be constant. A cloud base occurs when the photospheric temperature is high. For a family of ice giants with different photospheric temperatures, the cooler ice giants will have warmer cloud bases. For an ice giant with a cool enough photospheric temperature, the cloud base will exist at the critical temperature. For still cooler ice giants, ocean surfaces will result. A high mixing ratio of water in the deep interior favors a liquid ocean. We find that Neptune is both too warm (photospheric temperature too high) and too dry (mixing ratio of water in the deep interior too low) for liquid oceans to exist at present. To have a liquid ocean, Neptune s deep interior water to gas ratio would have to be higher than current models allow, and the density at 19 kbar would have to be approx. equal to 0.8 g/cu cm. Such a high density is inconsistent with gravitational data obtained during the Voyager flyby. In our model, Neptune s water cloud base occurs around 660 K and 11 kbar, and the density there is consistent with Voyager gravitational data. As Neptune cools, the probability of a liquid ocean increases. Extrasolar "hot Neptunes," which presumably migrate inward toward their parent stars, cannot harbor liquid water oceans unless they have lost almost all of the hydrogen and helium from their deep interiors.

  15. Water Contaminant Mitigation in Ionic Liquid Propellant

    NASA Technical Reports Server (NTRS)

    Conroy, David; Ziemer, John

    2009-01-01

    Appropriate system and operational requirements are needed in order to ensure mission success without unnecessary cost. Purity requirements applied to thruster propellants may flow down to materials and operations as well as the propellant preparation itself. Colloid electrospray thrusters function by applying a large potential to a room temperature liquid propellant (such as an ionic liquid), inducing formation of a Taylor cone. Ions and droplets are ejected from the Taylor cone and accelerated through a strong electric field. Electrospray thrusters are highly efficient, precise, scaleable, and demonstrate low thrust noise. Ionic liquid propellants have excellent properties for use as electrospray propellants, but can be hampered by impurities, owing to their solvent capabilities. Of foremost concern is the water content, which can result from exposure to atmosphere. Even hydrophobic ionic liquids have been shown to absorb water from the air. In order to mitigate the risks of bubble formation in feed systems caused by water content of the ionic liquid propellant, physical properties of the ionic liquid EMI-Im are analyzed. The effects of surface tension, material wetting, physisorption, and geometric details of the flow manifold and electrospray emitters are explored. Results are compared to laboratory test data.

  16. Remote sensing of liquid water target operations

    SciTech Connect

    Ferrieri, R.A.; Alexoff, D.L.; Schlyer, D.J.

    1993-12-31

    One of the key considerations in the design of automated liquid water target systems for reliable {sup 18}F{sup {minus}} production is the inclusion of adequate sensing devices for remote feedback of individual process operation status. The process operations needed to generate, extract and deliver {sup 18}F{sup {minus}} to the Hot Lab for subsequent chemistry are not very complex. These involve configuring target valves for access during loading of enriched water, filling the target with water, reconfiguring the target valves so that it is sealed during irradiation, and finally emptying the target contents after irradiation. At the lowest level of remote sensing of these operations is the act of determining whether target valves are actually in their correct configuration for a specific step. Sensing the filling or emptying status of the target is perhaps the most crucial feedback for reliable target performance. Sensing the presence, or absence, of liquid water can be accomplished by measuring some physical property of the substance in that phase. The use of electrical conductivity meters is one method we have discussed in the past in relation to the remote sensing of metal cations to determine the presence of water. Likewise, refractive index is another property of water that can be harnessed for sensing the liquid`s presence. The performance of an optical sensor in the BNL JSW beamline for routine production of {sup 18}F{sup {minus}} is discussed.

  17. Vapor deposition of water on graphitic surfaces: formation of amorphous ice, bilayer ice, ice I, and liquid water.

    PubMed

    Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria

    2014-11-14

    Carbonaceous surfaces are a major source of atmospheric particles and could play an important role in the formation of ice. Here we investigate through molecular simulations the stability, metastability, and molecular pathways of deposition of amorphous ice, bilayer ice, and ice I from water vapor on graphitic and atomless Lennard-Jones surfaces as a function of temperature. We find that bilayer ice is the most stable ice polymorph for small cluster sizes, nevertheless it can grow metastable well above its region of thermodynamic stability. In agreement with experiments, the simulations predict that on increasing temperature the outcome of water deposition is amorphous ice, bilayer ice, ice I, and liquid water. The deposition nucleation of bilayer ice and ice I is preceded by the formation of small liquid clusters, which have two wetting states: bilayer pancake-like (wetting) at small cluster size and droplet-like (non-wetting) at larger cluster size. The wetting state of liquid clusters determines which ice polymorph is nucleated: bilayer ice nucleates from wetting bilayer liquid clusters and ice I from non-wetting liquid clusters. The maximum temperature for nucleation of bilayer ice on flat surfaces, T(B)(max) is given by the maximum temperature for which liquid water clusters reach the equilibrium melting line of bilayer ice as wetting bilayer clusters. Increasing water-surface attraction stabilizes the pancake-like wetting state of liquid clusters leading to larger T(B)(max) for the flat non-hydrogen bonding surfaces of this study. The findings of this study should be of relevance for the understanding of ice formation by deposition mode on carbonaceous atmospheric particles, including soot. PMID:25399173

  18. Vapor deposition of water on graphitic surfaces: Formation of amorphous ice, bilayer ice, ice I, and liquid water

    SciTech Connect

    Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria

    2014-11-14

    Carbonaceous surfaces are a major source of atmospheric particles and could play an important role in the formation of ice. Here we investigate through molecular simulations the stability, metastability, and molecular pathways of deposition of amorphous ice, bilayer ice, and ice I from water vapor on graphitic and atomless Lennard-Jones surfaces as a function of temperature. We find that bilayer ice is the most stable ice polymorph for small cluster sizes, nevertheless it can grow metastable well above its region of thermodynamic stability. In agreement with experiments, the simulations predict that on increasing temperature the outcome of water deposition is amorphous ice, bilayer ice, ice I, and liquid water. The deposition nucleation of bilayer ice and ice I is preceded by the formation of small liquid clusters, which have two wetting states: bilayer pancake-like (wetting) at small cluster size and droplet-like (non-wetting) at larger cluster size. The wetting state of liquid clusters determines which ice polymorph is nucleated: bilayer ice nucleates from wetting bilayer liquid clusters and ice I from non-wetting liquid clusters. The maximum temperature for nucleation of bilayer ice on flat surfaces, T{sub B}{sup max} is given by the maximum temperature for which liquid water clusters reach the equilibrium melting line of bilayer ice as wetting bilayer clusters. Increasing water-surface attraction stabilizes the pancake-like wetting state of liquid clusters leading to larger T{sub B}{sup max} for the flat non-hydrogen bonding surfaces of this study. The findings of this study should be of relevance for the understanding of ice formation by deposition mode on carbonaceous atmospheric particles, including soot.

  19. Planetary protection and liquid water on Mars

    NASA Astrophysics Data System (ADS)

    Lobitz, B. M.; McKay, C. P.

    An important component of the Planetary Protection Program is the assessment of the potential habitability of extraterrestrial locations for Earth microbes inadvertently carried there. It is imperative that the most accurate assessment of extraterrestrial habitability be made. This is particularly urgent for the surface of Mars because many missions are planned to explore various environments on Mars in the near future. Upcoming missions to Mars will be radio-thermal generating system-powered. These heat sources will modify the microclimate and its habitability for extant life, especially in the event that such a platform crashes on the martian surface. This is particularly urgent for the surface of Mars because many missions are planned to explore various environments on Mars in the near future. Because the goal of many of these missions is directly tied to the search for evidence of life, it is not surprising that the locations of interest are those most likely to provide a habitat for life. This change could hinder or aid extant life or provide an abode for Earth organisms to survive under these modified martian conditions. The key requirement for habitability is the presence of liquid water. One source of water for these organisms could be from snowmelt from water-rich snow deposits. These snowmelts could provide episodic liquid water for life in the past or the present. It is interesting therefore to consider the effect of an RTG if placed on surface ice in the polar regions of Mars. For liquid water to be present on Mars three requirements must be met: 1) the pressure must be above the boiling point of water, the lowest boiling point possible is the triple point (610 Pa). 2) The temperature of the water must be above the freezing point but below the boiling point. 3) There must be a source of water. The study reported here is composed of three related tasks: 1) Assess the locations on Mars where natural conditions sustain an environment in which liquid water could be stable. 2) Identify locations on Mars where ground ice or seasonal ice deposits are present in locations where conditions allow for liquid water stability. 3) Identify locations where ground ice is present and where an artificial heat source from a spacecraft or lander would generate liquid water. The first task used MOLA high resolution data and the Viking Lander surface pressure measurements to compute the expected surface pressure through the martian year. This result was then coupled with direct measurements of temperature from Mars Global Surveyor TES to determine possible sites for liquid water. We found considerable regions on Mars in which liquid water - if present - would be stable for short time periods. These regions were then combined with observed ground ice locations that could be sources of liquid water (task 2). Modifications to the microclimate temperature regime due to an RTG on the surface were then considered in task 3 based on heat transfer modeling results to determine how much and where the stability regions were affected.

  20. Liquid-liquid phase transitions and water-like anomalies in liquids

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik

    In this thesis we employ computer simulations and statistical physics to understand the origin of liquid-liquid phase transitions and their relationship with anomalies typical of liquid water. Compared with other liquids, water has many anomalies. For example the density anomaly: when water is cooled below 4 °C the density decreases rather than increases. This and other anomalies have also been found to occur in a few other one-component liquids, sometimes in conjunction with the existence of a liquid-liquid phase transition (LLPT) between a low-density liquid (LDL) and a high-density liquid (HDL). Using simple models we explain how these anomalies arise from the presence of two competing length scales. As a specific example we investigate the cut ramp potential, where we show the importance of "competition" in this context, and how one length scale can sometimes be zero. When there is a clear energetic preference for either LDL or HDL for all pressures and temperatures, then there is insufficient competition between the two liquid structures and no anomalies occur. From the simple models it also follows that anomalies can occur without the presence of a LLPT and vice versa. It remains therefore unclear if water has a LLPT that ends in a liquid-liquid critical point (LLCP), a hypothesis that was first proposed based on simulations of the ST2 water model. We confirm the existence of a LLCP in this model using finite size scaling and the Challa-Landau-Binder parameter, and show that the LLPT is not a liquid-crystal transition, as has recently been suggested. Previous research has indicated the possible existence of a LLCP in liquid silica. We perform a detailed analysis of two different silica models (WAC and BKS) at temperatures much lower than was previously simulated. Within the accessible temperature range we find no LLCP in either model, although in the case of WAC potential it is closely approached. We compare our results with those obtained for other tetrahedral liquids and conclude that insufficient "stiffness" in the Si-O-Si bond angle might be responsible for the absence of a LLCP.

  1. Ultrasound-assisted modulation of concomitant polymorphism of curcumin during liquid antisolvent precipitation.

    PubMed

    Thorat, Alpana A; Dalvi, Sameer V

    2016-05-01

    Curcumin polymorphs were found to precipitate concomitantly during liquid antisolvent precipitation. While, commercially available curcumin exists in a monoclinic form, the curcumin particles when precipitated in presence of additives and ultrasound were either found to be the mixtures of orthorhombic (Form 3) and monoclinic form (Form 1) or were found to be in orthorhombic form (Form 3) or monoclinic form (Form 1). The experimentally observed particle morphologies did not match clearly with the predicted BFDH morphologies of curcumin and the experimentally observed morphologies were more elongated as compared to the predicted BFDH morphologies. At lower ultrasonic irradiation times, the monoclinic form (Form 1) was found to dominate the mixture of particles. However, an increase in ultrasonic irradiation time was found to increase the percentage of orthorhombic form (Form 3) in the particles indicating that the increase in ultrasonic energy facilitates formation of orthorhombic form over the monoclinic form, irrespective of the additive used. These results therefore suggest that the ultrasonic energy can be effectively used to manipulate the polymorphic outcome of the precipitation. PMID:26703200

  2. Core-softened Fluids, Water-like Anomalies and the Liquid-Liquid Critical Points

    E-print Network

    Barbosa, Marcia C. B.

    PREPRINT Core-softened Fluids, Water-like Anomalies and the Liquid-Liquid Critical Points Evy simulations are used to examine the relationship between water-like anoma- lies and the liquid-liquid critical of the shoulder well is chosen so that the resulting potential reproduces the oxygen-oxygen radial distribution

  3. Dispersion corrected RPBE studies of liquid water.

    PubMed

    Forster-Tonigold, Katrin; Groß, Axel

    2014-08-14

    The structure of liquid water has been addressed by ab initio molecular dynamics simulations based on density functional theory. Exchange-correlation effects have been described by the popular PBE and RPBE functionals within the generalized gradient approximation as these functionals also yield satisfactory results for metals which is important to model electrochemical interfaces from first principles. In addition, dispersive interactions are included by using dispersion-corrected schemes. It turns out that the dispersion-corrected RPBE functional reproduces liquid water properties quite well in contrast to the PBE functional. This is caused by the replacement of the over-estimated directional hydrogen-bonding in the PBE functional by non-directional dispersive interactions. PMID:25134582

  4. The Structure, Density, and Local Environment Distribution in Ab Initio Liquid Water

    NASA Astrophysics Data System (ADS)

    Santra, Biswajit; Distasio, Robert A., Jr.; Wu, Xifan; Car, Roberto

    2014-03-01

    We have performed extensive ab initio molecular dynamics (AIMD) simulations of liquid water at ambient conditions in the canonical (NVT) and isothermal-isobaric (NPT) ensembles to understand the individual and collective importance of exact exchange, van der Waals interactions, and nuclear quantum effects on the structural properties of liquid water. AIMD simulations which include these effects result in oxygen-oxygen radial distribution functions which are in excellent agreement with experiments and a liquid water structure having an equilibrium density within 1% of the experimental value of 1 g/cm3. A detailed analysis of the distribution of local structure in ambient liquid water has revealed that the inherent potential energy surface is bimodal with respect to high- and low-density molecular environments, consistent with the existence of polymorphism in the amorphous phases of water. With these findings in mind, the methodology presented herein overcomes the well-known limitations of semi-local density functional theory (GGA-DFT) providing a detailed and accurate microscopic description of ambient liquid water. DOE: DE-SC0008626, DOE: DE-SC0005180, NSF: CHE-0956500.

  5. Liquid water and active resurfacing on Europa

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.; Reynolds, R. T.; Cassen, P. M.; Peale, S. J.

    1983-01-01

    Arguments for recent resurfacing of Europa by H2O from a liquid layer are presented, based on new interpretations of recent spacecraft and earth-based observations and revised theoretical calculations. The heat flow in the core and shell due to tidal forces is discussed, and considerations of viscosity and convection in the interior are found to imply water retention in the outer 60 km or so of the silicates, forming a layer of water/ice many tens of km thick. The outer ice crust is considered to be too thin to support heat transport rates sufficient to freeze the underlying water. Observational evidence for the calculations would consist of an insulating layer of frosts derived from water boiling up between cracks in the surface crust. Evidence for the existence of such a frost layer, including the photometric function of Europa and the deposits of sulfur on the trailing hemisphere, is discussed.

  6. Local Environment Distribution in Ab Initio Liquid Water

    NASA Astrophysics Data System (ADS)

    Santra, Biswajit; Distasio, Robert A., Jr.; Car, Roberto

    2013-03-01

    We have analyzed the distribution of local environments in liquid water at ambient conditions and its inherent potential energy surface (IPES) based on state-of-the-art ab initio molecular dynamics simulations performed on 128 molecules implementing hybrid PBE0 exchange [PRB 79, 085102 (2009)] and van der Waals (vdW) interactions [PRL 102, 073005 (2009)]. The local environments of molecules are characterized in terms of the local structure index (LSI) [JCP 104, 7671 (1996)] which is able to distinguish high- and low-density molecular environments. In agreement with simulations based on model potentials, we find that the distribution of LSI is unimodal at ambient conditions and bimodal in the IPES, consistent with the existence of polymorphism in amorphous phases of water. At ambient conditions spatial LSI fluctuations extend up to ~7 Å and their dynamical correlation decays on a time scale of ~3 ps, as found for density fluctuations in a recent study [PRL 106, 037801 (2011)]. DOE: DE-SC0008626, DOE: DE-SC0005180, NSF: CHE-0956500

  7. Thermodynamics of ice nucleation in liquid water.

    PubMed

    Wang, Xin; Wang, Shui; Xu, Qinzhi; Mi, Jianguo

    2015-01-29

    We present a density functional theory approach to investigate the thermodynamics of ice nucleation in supercooled water. Within the theoretical framework, the free-energy functional is constructed by the direct correlation function of oxygen-oxygen of the equilibrium water, and the function is derived from the reference interaction site model in consideration of the interactions of hydrogen-hydrogen, hydrogen-oxygen, and oxygen-oxygen. The equilibrium properties, including vapor-liquid and liquid-solid phase equilibria, local structure of hexagonal ice crystal, and interfacial structure and tension of water-ice are calculated in advance to examine the basis for the theory. The predicted phase equilibria and the water-ice surface tension are in good agreement with the experimental data. In particular, the critical nucleus radius and free-energy barrier during ice nucleation are predicted. The critical radius is similar to the simulation value, suggesting that the current theoretical approach is suitable in describing the thermodynamic properties of ice crystallization. PMID:25546012

  8. liquid water path estimates in marine stratus 1.Introduction

    E-print Network

    Zuidema, Paquita

    liquid water path estimates in marine stratus P.Zuidema 1.Introduction Marine boundary-layer liquid,both liquid and dry. To date,the impact of microwave model improvements upon LWPs retrieved within marine the R/V Ron Brown.3 gaseous absorption models,and 3 liquid dielectric models are evaluated

  9. Metastable liquid-liquid transition in a molecular model of water

    NASA Astrophysics Data System (ADS)

    Palmer, Jeremy C.; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2014-06-01

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in the ST2 model of water, and point to the separation of time scales between crystallization and relaxation as being crucial for enabling it.

  10. Metastable liquid-liquid transition in a molecular model of water.

    PubMed

    Palmer, Jeremy C; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-06-19

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in the ST2 model of water, and point to the separation of time scales between crystallization and relaxation as being crucial for enabling it. PMID:24943954

  11. Liquid-liquid equilibrium of cholinium-derived bistriflimide ionic liquids with water and octanol.

    PubMed

    Costa, Anabela J L; Soromenho, Mário R C; Shimizu, Karina; Marrucho, Isabel M; Esperança, José M S S; Canongia Lopes, J N; Rebelo, Luís Paulo N

    2012-08-01

    The liquid-liquid equilibria of mixtures of cholinum-based ionic liquids (N-alkyl-N,N-dimethylhydroxyethylammonium bis(trifluoromethane)sulfonylimide, [N(11n2OH)][Ntf(2)], n = 1, 2, 3, 4, and 5) plus water or 1-octanol were investigated at atmospheric pressure over the entire composition range. The experiments were conducted between 265 and 385 K using the cloud-point method. The systems exhibit phase diagrams consistent with the existence of upper critical solution temperatures. The solubility of [N(1 1 n 2OH)][Ntf(2)] in water is lower for cations with longer alkyl side chains (larger n values). The corresponding trend in the octanol mixtures is reversed. The ([N(1 1 1 2OH)][Ntf(2)] + water + octanol) ternary system shows triple liquid-liquid immiscibility at room temperature and atmospheric pressure. A combined analytic/synthetic method was used to estimate the corresponding phase diagram under those conditions. Auxiliary molecular dynamics simulation data were used to interpret the experimental results at a molecular level. PMID:22770438

  12. PERMEABILITY OF SOILS TO FOUR ORGANIC LIQUIDS AND WATER

    EPA Science Inventory

    Saturated hydraulic conductivities and intrinsic permeabilities were evaluated for eight contrasting soils with four organic liquids and water. The organic liquids were kerosene, ethylene glycol, isopropyl alcohol and xylene. Intrinsic permeability for any given soil varied inver...

  13. Liquid-liquid transition in ST2 water

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Palmer, Jeremy C.; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2012-12-01

    We use the weighted histogram analysis method [S. Kumar, D. Bouzida, R. H. Swendsen, P. A. Kollman, and J. M. Rosenberg, J. Comput. Chem. 13, 1011 (1992), 10.1002/jcc.540130812] to calculate the free energy surface of the ST2 model of water as a function of density and bond-orientational order. We perform our calculations at deeply supercooled conditions (T = 228.6 K, P = 2.2 kbar; T = 235 K, P = 2.2 kbar) and focus our attention on the region of bond-orientational order that is relevant to disordered phases. We find a first-order transition between a low-density liquid (LDL, ? ? 0.9 g/cc) and a high-density liquid (HDL, ? ? 1.15 g/cc), confirming our earlier sampling of the free energy surface of this model as a function of density [Y. Liu, A. Z. Panagiotopoulos, and P. G. Debenedetti, J. Chem. Phys. 131, 104508 (2009), 10.1063/1.3229892]. We demonstrate the disappearance of the LDL basin at high pressure and of the HDL basin at low pressure, in agreement with independent simulations of the system's equation of state. Consistency between directly computed and reweighted free energies, as well as between free energy surfaces computed using different thermodynamic starting conditions, confirms proper equilibrium sampling. Diffusion and structural relaxation calculations demonstrate that equilibration of the LDL phase, which exhibits slow dynamics, is attained in the course of the simulations. Repeated flipping between the LDL and HDL phases in the course of long molecular dynamics runs provides further evidence of a phase transition. We use the Ewald summation with vacuum boundary conditions to calculate long-ranged Coulombic interactions and show that conducting boundary conditions lead to unphysical behavior at low temperatures.

  14. Evidence for Recent Liquid Water on Mars

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Newton Crater is a large basin formed by an asteroid impact that probably occurred more than 3 billion years ago. It is approximately 287 kilometers (178 miles) across. The picture shown here (top) highlights the north wall of a specific, smaller crater located in the southwestern quarter of Newton Crater (above). The crater of interest was also formed by an impact; it is about 7 km (4.4 mi) across, which is about 7 times bigger than the famous Meteor Crater in northern Arizona in North America. The north wall of the small crater has many narrow gullies eroded into it. These are hypothesized to have been formed by flowing water and debris flows. Debris transported with the water created lobed and finger-like deposits at the base of the crater wall where it intersects the floor (bottom center top image). Many of the finger-like deposits have small channels indicating that a liquid, most likely water, flowed in these areas. Hundreds of individual water and debris flow events might have occurred to create the scene shown here. Each outburst of water from higher up on the crater slopes would have constituted a competition between evaporation, freezing, and gravity. The individual deposits at the ends of channels in this MOC image mosaic were used to get a rough estimate of the minimum amount of water that might be involved in each flow event. This is done first by assuming that the deposits are like debris flows on Earth. In a debris flow, no less than about 10% (and no more than 30%) of their volume is water. Second, the volume of an apron deposit is estimated by measuring the area covered in the MOC image and multiplying it by a conservative estimate of thickness, 2 meters (6.5 feet). For a flow containing only 10% water, these estimates conservatively suggest that about 2.5 million liters (660,000 gallons) of water are involved in each event; this is enough to fill about 7 community-sized swimming pools or enough to supply 20 people with their water needs for a year. The Mars Orbiter Camera (MOC) high resolution view is located near 41.1S, 159.8W and is a mosaic of three different pictures acquired between January and May 2000. The MOC scene is illuminated from the left; north is up.

  15. Simulation of the intermolecular vibrational spectra of liquid water and water clusters

    E-print Network

    Mukamel, Shaul

    are believed to be as follows:3 The 60 cm-' peak results from the bending of the hydrogen bonds between waterSimulation of the intermolecular vibrational spectra of liquid water and water clusters Wayne B and infrared spectra of liquid water and water clusters in the frequency range O-1000 cm-`. The librational

  16. Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data

    E-print Network

    Ruf, Christopher

    Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data S, zonal, and regional scale histories of overocean integrated water vapor (IWV) and cloud liquid water, J. Teixeira, S. Desai, W. Lu, E. Fetzer, C. Ruf, X. Huang, and Y. Yung (2009), Ocean water vapor

  17. Interactions between water and 1-butyl-1-methylpyrrolidinium ionic liquids

    NASA Astrophysics Data System (ADS)

    Fadeeva, Tatiana A.; Husson, Pascale; DeVine, Jessalyn A.; Costa Gomes, Margarida F.; Greenbaum, Steven G.; Castner, Edward W.

    2015-08-01

    We report experimental results on the diffusivity of water in two ionic liquids obtained using the pulsed-gradient spin-echo NMR method. Both ionic liquids have the same cation, 1-butyl-1-methylpyrrolidinium, but different trifluoromethyl-containing anions. One has a strongly hydrophobic anion, bis(trifluoromethylsulfonyl)amide, while the second has a hydrophilic anion, trifluoromethylsulfonate. Transport of water in these ionic liquids is much faster than would be predicted from hydrodynamic laws, indicating that the neutral water molecules experience a very different friction than the anions and cations at the molecular level. Temperature-dependent viscosities, conductivities, and densities are reported as a function of water concentration to further analyze the properties of the ionic liquid-water mixtures. These results on the properties of water in ionic liquids should be of interest to researchers in diverse areas ranging from separations, solubilizing biomass and energy technologies.

  18. Liquid-liquid equilibria of fuel oxygenate + water + hydrocarbon mixtures. 3: Effect of temperature

    SciTech Connect

    Wagner, G.; Sandler, S.I.

    1995-09-01

    The authors have measured the ternary liquid-liquid equilibria of water + ethanol mixtures with, separately, 2,2,4-trimethylpentane and toluene at 5 and 40 C, water + tert-amyl alcohol (TAOH) mixtures with, separately, toluene and hexane at 5 and 40 C, and of water + TAOH + pentane mixtures at 5 C. The ethanol-containing systems exhibit type 1 liquid-liquid phase behavior, and the TAOH-containing systems exhibit type 2 behavior. These data, together with the data they have previously reported at 25 C, provide information on how the liquid-liquid equilibria of these systems change as a function of temperature. While the addition of ethanol is found to increase the solubility of hydrocarbons in the aqueous phase, the concentration of the hydrocarbon in the water-rich phase decreases with increasing temperature. With the exception of hydrocarbon in the water-rich phase, the experimental data could be correlated quite well with either the UNIQUAC or NRTL models. For most of the systems considered here the predictions of the phase behavior with the liquid-liquid UNIFAC group-contribution model are only qualitatively correct. However, the liquid-liquid UNIFAC model erroneously predicts type 2 phase behavior to occur for water + ethanol + 2,2,4-trimethylpentane system at 5 C.

  19. Isotope effects in liquid water by infrared spectroscopy. IV. No free OH groups in liquid water

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2010-10-01

    The presence of free OH (OH not H-bonded) in bulk water is a key element for the determination of its molecular structure. The OH covalent bond infrared (IR) absorption is highly sensitive to the molecular environment. For this reason, IR spectroscopy is used for the determination of free OH. A workable definition of this is obtained with methanol (MeOH) in hexane where minute quantities of free OH are present. These absorb at 3654 cm-1 (a 27 cm-1 redshift from the gas position) with a full width at half height of 35 cm-1. The IR spectrum of water between room temperature and 95 °C does not display such a band near 3650 cm-1. This indicates that we do not see, in the IR spectra, the "free" OH group. From this we conclude that it is not present in liquid water at least down to the 1000 ppm level which is the limit of detectivity of our spectrometer. Other spectroscopic considerations of methanol and water in acetonitrile solutions indicate that weak H-bonds are also not present in liquid water.

  20. Evidence for Recent Liquid Water on Mars

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image, acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in May 2000 shows numerous examples of martian gullies that all start--or head--in a specific layer roughly a hundred meters beneath the surface of Mars. These features are located on the south-facing wall of a trough in the Gorgonum Chaos region, an area found to have many examples of gullies proposed to have formed by seepage and runoff of liquid water in recent martian times. The layer from which the gullies emanate has recessed backward to form an overhang beneath a harder layer of rock. The larger gullies have formed an alcove--an area above the overhang from which debris has collapsed to leave a dark-toned scar. Below the layer of seepage is found a dark, narrow channel that runs down the slope to an apron of debris. The small, bright, parallel features at the base of the cliff at the center-right of the picture is a series of large windblown ripples. Although the dark tone of the alcoves and channels in this image is not likely to be the result of wet ground (the contrast in this image has been enhanced), it does suggest that water has seeped out of the ground and moved down the slope quite recently. Sharp contrasts between dark and light areas are hard to maintain on Mars for very long periods of time because dust tends to coat surfaces and reduce brightness differences. To keep dust from settling on a surface, it has to have undergone some process of erosion (wind, landslides, water runoff) relatively recently. There is no way to know how recent this activity was, but educated guesses center between a few to tens of years, and it is entirely possible that the area shown in this image has water seeping out of the ground today. Centered near 37.9S, 170.2W, sunlight illuminates the MOC image from the upper left, north is toward the upper right. The context view above is from the Viking 1 orbiter and was acquired in 1977. The Viking picture is illuminated from the upper right; north is up. The small white box in the context frame shows the location of the high resolution MOC view.

  1. Liquid-liquid and vapor-liquid phase equilibria for 1-butanol + water + 2-propanol at ambient pressure

    SciTech Connect

    Aicher, T.; Bamberger, T.; Schluender, E.U.

    1995-05-01

    The liquid-liquid and the vapor-liquid phase equilibria of the ternary system 1-butanol + water + 2-propanol have been measured at ambient pressure. Compositions along the binodal curve have been determined gravimetrically at 0, 20, 50, and 60 C. The lines were determined for 0, 20, and 60 C. The data were compared to reported measurements at 80 C. Furthermore, the vapor-liquid equilibrium at ambient pressure has been measured for both one-phase and two-phase liquid mixtures using a recirculation still proposed by Roeck and Sieg.

  2. Polymersomes with ionic liquid interiors dispersed in water.

    PubMed

    Bai, Zhifeng; Lodge, Timothy P

    2010-11-17

    We describe polymersomes with ionic liquid interiors dispersed in water. The vesicles are prepared via a simple and spontaneous migration of poly(butadiene-b-ethylene oxide) (PB-PEO) block copolymer vesicles from a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), to water at room temperature. As PB is insoluble in both water and [EMIM][TFSI] and PEO is well solvated in both media, the vesicles feature a PB membrane with PEO brushes forming both interior and exterior coronas. The robust and stable PB-PEO vesicles migrate across the liquid-liquid interface with their ionic liquid interiors intact and form a stabilized aqueous dispersion of vesicles enclosing microscopic ionic liquid pools. The nanostructure of the vesicles with ionic liquid interiors dispersed in water is characterized by direct visualization using cryogenic transmission electron microscopy. Upon heating, the vesicles can be quantitatively transferred back to [EMIM][TFSI], thus enabling facile recovery. The reversible transport capability of the shuttle system is demonstrated by the use of distinct hydrophobic dyes, which are selectively and simultaneously loaded in the vesicle membrane and interior. Furthermore, the fluorescence of the loaded dyes in the vesicles enables probing of the microenvironment of the vesicular ionic liquid interior through solvatochromism and direct imaging of the vesicles using laser scanning confocal microscopy. This vesicle system is of particular interest as a nanocarrier or nanoreactor for reactions, catalysis, and separations using ionic liquids. PMID:20964305

  3. Thermoluminescence dosimetry measurements of brachytherapy sources in liquid water

    SciTech Connect

    Tailor, Ramesh; Tolani, Naresh; Ibbott, Geoffrey S.

    2008-09-15

    Radiation therapy dose measurements are customarily performed in liquid water. The characterization of brachytherapy sources is, however, generally based on measurements made with thermoluminescence dosimeters (TLDs), for which contact with water may lead to erroneous readings. Consequently, most dosimetry parameters reported in the literature have been based on measurements in water-equivalent plastics, such as Solid Water. These previous reports employed a correction factor to transfer the dose measurements from a plastic phantom to liquid water. The correction factor most often was based on Monte Carlo calculations. The process of measuring in a water-equivalent plastic phantom whose exact composition may be different from published specifications, then correcting the results to a water medium leads to increased uncertainty in the results. A system has been designed to enable measurements with TLDs in liquid water. This system, which includes jigs to support water-tight capsules of lithium fluoride in configurations suitable for measuring several dosimetric parameters, was used to determine the correction factor from water-equivalent plastic to water. Measurements of several {sup 125}I and {sup 131}Cs prostate brachytherapy sources in liquid water and in a Solid Water phantom demonstrated a correction factor of 1.039{+-}0.005 at 1 cm distance. These measurements are in good agreement with a published value of this correction factor for an {sup 125}I source.

  4. Rhabdomyolysis After Out-of-Water Exercise in an Elite Adolescent Water Polo Player Carrying the IL-6 174C Allele Single-Nucleotide Polymorphism.

    PubMed

    Eliakim, Alon; Ben Zaken, Sigal; Meckel, Yoav; Yamin, Chen; Dror, Nitzan; Nemet, Dan

    2015-12-01

    Eliakim, A, Ben Zaken, S, Meckel, Y, Yamin, C, Dror, N, and Nemet, D. Rhabdomyolysis after out-of-water exercise in an elite adolescent water polo player carrying the IL-6 174C allele single-nucleotide polymorphism. J Strength Cond Res 29(12): 3506-3508, 2015-We present an adolescent elite water polo player who despite a genetic predisposition to develop exercise-induced severe muscle damage due to carrying the IL-6 174C allele single-nucleotide polymorphism, developed acute rhabdomyolysis only after a vigorous out-of-water training, suggesting that water polo training may be more suitable for genetically predisposed athletes. PMID:25970495

  5. Glass–liquid transition of water at high pressure

    PubMed Central

    Andersson, Ove

    2011-01-01

    The knowledge of the existence of liquid water under extreme conditions and its concomitant properties are important in many fields of science. Glassy water has previously been prepared by hyperquenching micron-sized droplets of liquid water and vapor deposition on a cold substrate (ASW), and its transformation to an ultraviscous liquid form has been reported on heating. A densified amorphous solid form of water, high-density amorphous ice (HDA), has also been made by collapsing the structure of ice at pressures above 1 GPa and temperatures below approximately 140 K, but a corresponding liquid phase has not been detected. Here we report results of heat capacity Cp and thermal conductivity, in situ, measurements, which are consistent with a reversible transition from annealed HDA to ultraviscous high-density liquid water at 1 GPa and 140 K. On heating of HDA, the Cp increases abruptly by (3.4 ± 0.2) J mol-1 K-1 before crystallization starts at (153 ± 1) K. This is larger than the Cp rise at the glass to liquid transition of annealed ASW at 1 atm, which suggests the existence of liquid water under these extreme conditions. PMID:21690361

  6. Onset of ice VII phase during ps laser pulse propagation through liquid water

    NASA Astrophysics Data System (ADS)

    Paturi, Prem Kiran; Vaddapally, Rakesh Kumar; Acrhem Team

    2015-06-01

    Water dominantly present in liquid state on earth gets transformed to crystalline polymorphs under different dynamic loading conditions. Out of 15 different crystalline phases discovered till date, ice VII is observed to be stable over wide pressure (2-63 GPa) and temperature (>273 K) ranges. We present the onset of ice VII phase at low threshold of 2 mJ/pulse during 30 ps (532 nm, 10 Hz) laser pulse induced shock propagating through liquid water. Role of input pulse energy on the evolution of Stoke's and anti-Stoke's Raman shift of the dominant A1g mode of ice VII, filamentation, free-electrons, plasma shielding is presented. The H-bond network rearrangement, electron ion energy transfer time coinciding with the excitation pulse duration supported by the filamentation and plasma shielding of the ps laser pulses reduced the threshold of ice VII structure formation. Filamentation and the plasma shielding have shown the localized creation and sustenance of ice VII structure in liquid water over 3 mm length and 50 ?m area of cross-section. The work is supported by Defence Research and Developement Organization, India through Grants-in-Aid Program.

  7. VAPOR + LIQUID EQUILIBRIUM OF WATER, CARBON DIOXIDE, AND THE BINARY SYSTEM WATER + CARBON DIOXIDE FROM

    E-print Network

    VAPOR + LIQUID EQUILIBRIUM OF WATER, CARBON DIOXIDE, AND THE BINARY SYSTEM WATER + CARBON DIOXIDE the vapor-liquid equilibrium of water (between 323 and 573 K), carbon dioxide (between 230 and 290 K) and their binary mixtures (between 348 and 393 K). The properties of supercritical carbon dioxide were determined

  8. Space Station Water Processor Mostly Liquid Separator (MLS)

    NASA Technical Reports Server (NTRS)

    Lanzarone, Anthony

    1995-01-01

    This report presents the results of the development testing conducted under this contract to the Space Station Water Processor (WP) Mostly Liquid Separator (MLS). The MLS units built and modified during this testing demonstrated acceptable air/water separation results in a variety of water conditions with inlet flow rates ranging from 60 - 960 LB/hr.

  9. Factors that Determine Zeolite Stability in Hot Liquid Water.

    PubMed

    Zhang, Lu; Chen, Kuizhi; Chen, Banghao; White, Jeffery L; Resasco, Daniel E

    2015-09-16

    The susceptibility of zeolites to hot liquid water may hamper their full utilization in aqueous phase processes, such as those involved in biomass conversion and upgrading reactions. Interactions of zeolites with water strongly depend on the presence of hydrophilic moieties including Brønsted acid sites (BAS), extraframework cations, and silanol defects, which facilitate wetting of the surface. However, it is not clear which of these moieties are responsible for the susceptibility of zeolites to liquid water. Previous studies have offered contradictory explanations because the role of each of these characteristics has not been investigated independently. In this work, a systematic comparison has been attempted by relating crystallinity losses to the variation of each of the five zeolite characteristics that may influence their stability in liquid water, including number of BAS, Si-O-Si bonds, framework type, silanol defects, and extraframework Al. In this study, we have systematically monitored the crystallinity changes of a series of HY, H-ZSM-5, and H-? zeolite samples with varying Si/Al ratio, density of BAS, zeolite structure, and density of silanol defects upon exposure to liquid water at 200 °C. The results of this comparison unambiguously indicate that the density of silanol defects plays the most crucial role in determining susceptibility of zeolites to hot liquid water. By functionalizing the silanol defects with organosilanes, the hydrophobicity of defective zeolite is increased and the tolerance to hot liquid water is significantly enhanced. PMID:26301890

  10. Southern Hemisphere Craters on Mars with Possible Liquid Water

    NASA Astrophysics Data System (ADS)

    Lobitz, B. M.; McKay, C. P.; Averner, M. M.

    2003-05-01

    Russell Crater (54.5S, 12.5E) is a 200-km crater in the southern highlands of Mars. While the carter rim is about 1.5 km in elevation, the crater surface is at 0 km elevation and hence the pressure there is above the triple point of liquid water (0.61 kPa). Using MOLA high resolution data and the Viking lander surface pressure measurements we have computed the expected pressure in craters in the southern hemisphere through the martian year. We have coupled this with direct measurements of temperature from TES to determine possible sites for liquid water in crater bottoms. We compare the distribution of sites for liquid water stability with the distribution of gullies. MOC or THEMIS images of these crater bottoms potentially can reveal surface morphology that confirm the presence of liquid water in these craters. This work was supported in part by NASA's Fundamental Space Biology Program.

  11. Spectroscopic investigations of hydrogen bond dynamics in liquid water

    E-print Network

    Fecko, Christopher J., 1975-

    2004-01-01

    Many of the remarkable physical and chemical properties of liquid water are due to the strong influence hydrogen bonds have on its microscopic dynamics. However, because of the fast timescales involved, there are relatively ...

  12. Adsorbed water and thin liquid films on Mars

    NASA Astrophysics Data System (ADS)

    Boxe, C. S.; Hand, K. P.; Nealson, K. H.; Yung, Y. L.; Yen, A. S.; Saiz-Lopez, A.

    2012-07-01

    At present, bulk liquid water on the surface and near-subsurface of Mars does not exist due to the scarcity of condensed- and gas-phase water, pressure and temperature constraints. Given that the nuclei of soil and ice, that is, the soil solid and ice lattice, respectively, are coated with adsorbed and/or thin liquid films of water well below 273 K and the availability of water limits biological activity, we quantify lower and upper limits for the thickness of such adsorbed/water films on the surface of the Martian regolith and for subsurface ice. These limits were calculated based on experimental and theoretical data for pure water ice and water ice containing impurities, where water ice containing impurities exhibit thin liquid film enhancements, ranging from 3 to 90. Close to the cold limit of water stability (i.e. 273 K), thin liquid film thicknesses at the surface of the Martian regolith is 0.06 nm (pure water ice) and ranges from 0.2 to 5 nm (water ice with impurities). An adsorbed water layer of 0.06 nm implies a dessicated surface as the thickness of one monolayer of water is 0.3 nm but represents 0.001-0.02% of the Martian atmospheric water vapour inventory. Taking into account the specific surface area (SSA) of surface-soil (i.e. top 1 mm of regolith and 0.06 nm adsorbed water layer), shows Martian surface-soil may contain interfacial water that represents 6-66% of the upper- and lower-limit atmospheric water vapour inventory and almost four times and 33%, the lower- and upper-limit Martian atmospheric water vapour inventory. Similarly, taking the SSA of Martian soil, the top 1 mm or regolith at 5 nm thin liquid water thickness, yields 1.10×1013 and 6.50×1013 litres of waters, respectively, 55-325 times larger than Mars' atmospheric water vapour inventory. Film thicknesses of 0.2 and 5 nm represent 2.3×104-1.5×106 litres of water, which is 6.0×10-7-4.0×10-4%, respectively, of a 10 pr ?m water vapour column, and 3.0×10-6-4.0×10-4% and 6.0×10-6-8.0×10-4%, respectively, of the Martian atmospheric water vapour inventory. Thin liquid film thicknesses on/in subsurface ice were investigated via two scenarios: (i) under the idealistic case where it is assumed that the diurnal thermal wave is equal to the temperature of ice tens of centimetres below the surface, allowing for such ice to experience temperatures close to 273 K and (ii) under the, likely, realistic scenario where the diurnal thermal wave allows for the maximum subsurface ice temperature of 235 K at 1 m depth between 30°N and 30°S. Scenario 1 yields thin liquid film thicknesses ranging from 11 to 90 nm; these amounts represent 4×106-3.0×107 litres of water. For pure water ice, Scenario 2 reveals that the thickness of thin liquid films contained on/within Martian subsurface is less than 1.2 nm, several molecular layers thick. Conversely, via the effect of impurities at 235 K allows for a thin liquid film thickness on/within subsurface ice of 0.5 nm, corresponding to 6.0×104 litres of water. The existence of thin films on Mars is supported by data from the Mars Exploration Rovers (MERs) Spirit and Opportunity's Alpha Proton X-ray Spectrometer instrumentation, which have detected increased levels of bromine beneath the immediate surface, suggestive of the mobilization of soluble salts by thin films of liquid water towards local cold traps. These findings show that biological activity on the Martian surface and subsurface is not limited by nanometre dimensions of available water.

  13. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    NASA Astrophysics Data System (ADS)

    Yu, Tang-Qing; Chen, Pei-Yang; Chen, Ming; Samanta, Amit; Vanden-Eijnden, Eric; Tuckerman, Mark

    2014-06-01

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency.

  14. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    SciTech Connect

    Yu, Tang-Qing Vanden-Eijnden, Eric; Chen, Pei-Yang; Chen, Ming; Samanta, Amit; Tuckerman, Mark

    2014-06-07

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency.

  15. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    PubMed Central

    Yu, Tang-Qing; Chen, Pei-Yang; Chen, Ming; Samanta, Amit; Vanden-Eijnden, Eric; Tuckerman, Mark

    2014-01-01

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency. PMID:24907992

  16. Ice-Crystal Fallstreaks from Supercooled Liquid Water Parent Clouds

    NASA Technical Reports Server (NTRS)

    Campbell, James R.; O'C. Starr, David; Welton, Ellsworth J.; Spinhirne, James D.; Ferrare, Richard A.

    2003-01-01

    On 31 December 2001, ice-crystal fallstreaks (e.g., cirrus uncinus, or colloquially "Mare's Tails") from supercooled liquid water parent clouds were observed by ground-based lidars pointed vertically from the Atmospheric Radiation Measurement Southern Great Plains (SGP) facility near Lamont, Oklahoma. The incidence of liquid phase cloud with apparent ice-phase precipitation is investigated. Scenarios for mixed-phase particle nucleation, and fallstreak formation and sustenance are discussed. The observations are unique in the context of the historical reverence given to the commonly observed c h s uncinus fallstreak (wholly ice) versus this seemingly contradictory coincidence of liquid water begetting ice-crystal streaks.

  17. Process for blending coal with water immiscible liquid

    DOEpatents

    Heavin, Leonard J. (Olympia, WA); King, Edward E. (Gig Harbor, WA); Milliron, Dennis L. (Lacey, WA)

    1982-10-26

    A continuous process for blending coal with a water immiscible liquid produces a uniform, pumpable slurry. Pulverized raw feed coal and preferably a coal derived, water immiscible liquid are continuously fed to a blending zone (12 and 18) in which coal particles and liquid are intimately admixed and advanced in substantially plug flow to form a first slurry. The first slurry is withdrawn from the blending zone (12 and 18) and fed to a mixing zone (24) where it is mixed with a hot slurry to form the pumpable slurry. A portion of the pumpable slurry is continuously recycled to the blending zone (12 and 18) for mixing with the feed coal.

  18. Evidence for Recent Liquid Water on Mars

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Gullies eroded into the wall of a meteor impact crater in Noachis Terra. This high resolution view (top left) from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) shows channels and associated aprons of debris that are interpreted to have formed by groundwater seepage, surface runoff, and debris flow. The lack of small craters superimposed on the channels and apron deposits indicates that these features are geologically young. It is possible that these gullies indicate that liquid water is present within the martian subsurface today. The MOC image was acquired on September 28, 1999. The scene covers an area approximately 3 kilometers (1.9 miles) wide by 6.7 km (4.1 mi) high (note, the aspect ratio is 1.5 to 1.0). Sunlight illuminates this area from the upper left. The image is located near 54.8S, 342.5W. The context image (above) shows the location of the MOC image on the south-facing wall of an impact crater approximately 20 kilometers (12 miles) in diameter. The context picture was obtained by the Viking 1 orbiter in 1980 and is illuminated from the upper left. The large mound on the floor of the crater in the context view is a sand dune field. The Mars Orbiter Camera high resolution images are taken black-and-white (grayscale); the color seen here has been synthesized from the colors of Mars observed by the MOC wide angle cameras and by the Viking Orbiters in the late 1970s. A brief description of how the color was generated: The MOC narrow angle camera only takes grayscale (black and white) pictures. To create the color versions seen here, we have taken much lower resolution red and blue images acquired by the MOC's wide angle cameras, and by the Viking Orbiter cameras in the 1970s, synthesized a green image by averaging red and blue, and created a pallete of colors that represent the range of colors on Mars. We then use a relationship that correlates color and brightness to assign a color to each gray level. This is only a crude approximation of martian color. It is likely Mars would not look like this to a human observer at Mars.

  19. Water: The Liquid of Life. Fifth Grade.

    ERIC Educational Resources Information Center

    Illinois State Environmental Protection Agency, Springfield.

    These materials are for use by elementary and middle school teachers in the state of Illinois. This document contains five modules for teaching water conservation. Topics include: (1) "Life Depends on Water,""What is Water?" and "The Hydrologic Cycle"; (2) "The Treatment of Drinking Water"; (3) "Wastewater Treatment"; (4) "Earth's Closed…

  20. Confinement effects on the liquid-liquid phase transition and anomalous properties of a monatomic water-like liquid.

    PubMed

    Sun, Gang; Giovambattista, Nicolas; Xu, Limei

    2015-12-28

    We use molecular dynamics simulations to study the effects of confinement on the phase behavior of a water-like monatomic liquid that exhibits a liquid-liquid phase transition (LLPT) and a liquid-liquid critical point (LLCP). The liquid is confined between parallel walls and we focus on the effects of wall separation and surface chemistry (solvophobicity/solvophilicity) on the location of the LLCP, temperature of maximum density (TMD) line, and loci of compressibility maxima (CM). It is found that, independently of the surface solvophobicity/solvophilicity, the LLCP, TMD, and CM lines shift rapidly towards higher pressures and lower temperatures as the wall separation is reduced. It follows that the effects of confinement on the TMD and CM lines are indicative of the confinement effects on the LLCP/LLPT. Confinement effects are observable already when the liquid particles form ?15 layers between the walls. For the case of water, this corresponds to a separation of ?4-5 nm between the surfaces, larger than the confining dimension of the nanopores commonly used to study the hypothesized LLPT in confined water. Hence, our results suggest that such experiments should not be interpreted in terms of the phase diagrams proposed for bulk water. PMID:26723688

  1. Liquid Water in the Extremely Shallow Martian Subsurface

    NASA Technical Reports Server (NTRS)

    Pavlov, A.; Shivak, J. N.

    2012-01-01

    Availability of liquid water is one of the major constraints for the potential Martian biosphere. Although liquid water is unstable on the surface of Mars due to low atmospheric pressures, it has been suggested that liquid films of water could be present in the Martian soil. Here we explored a possibility of the liquid water formation in the extremely shallow (1-3 cm) subsurface layer under low atmospheric pressures (0.1-10 mbar) and low ("Martian") surface temperatures (approx.-50 C-0 C). We used a new Goddard Martian simulation chamber to demonstrate that even in the clean frozen soil with temperatures as low as -25C the amount of mobile water can reach several percents. We also showed that during brief periods of simulated daylight warming the shallow subsurface ice sublimates, the water vapor diffuses through porous surface layer of soil temporarily producing supersaturated conditions in the soil, which leads to the formation of additional liquid water. Our results suggest that despite cold temperatures and low atmospheric pressures, Martian soil just several cm below the surface can be habitable.

  2. Liquid polymorphism, density anomaly and H-bond disruption in an associating lattice gases

    E-print Network

    Aline Balladares; Vera B. Henriques; Marcia C. Barbosa

    2006-09-21

    We have investigated the effects of either distorting hydrogen bonds or removing proton degeneracy on the thermodynamic properties of a minimal model for associating liquids. The presence of two liquid phases and a density anomaly is unaffected in both cases. Increasing the degeneracy of bonded structures leads to lower temperature critical points and a steeper liquid-liquid coexistence line, implying a low density liquid of larger entropy. Analysis of the hydrogen bond net accross the phase diagram indicates that the density anomaly is accompanied by a steep reduction of hydrogen bond density, which introduces a restriction on a correlation which has been preconized long ago. This feature is present independent of bond distortion or of the presence of proton entropy.

  3. Order parameter defining liquid-liquid transition in water

    NASA Astrophysics Data System (ADS)

    Grigera, J. Raul; Chara, Osvaldo; McCarthy, Andres

    2011-03-01

    Water presents both open tetrahedral and compact hexagonal structures. Although several order parameters have been proposed to quantify this, all of them are only applicable to data produced by simulation. We present an order parameter (Pr) that is calculated from the radial distribution function g (r) , also available from experiment. We hereby extract the tetrahedral and hexagonal components from the g (r) , each one reconstructed as the sum of a Freundlich distribution for the first peak, two subsequent Gaussian distributions, and a sigmoidal to account for the rest. The order parameter can be calculated from the relative contribution of tetrahedral over hexagonal contribution. We obtained the Pr for SPC/E water model from molecular dynamics simulations of water at different pressures and temperatures. At 300K, the pressure in which both, tetrahedral and hexagonal contributions become equal (Pr = 0), a structural crossover is found in the vicinity of 2kbar, close to the pressure at which the `'anomalous'' behavior manifests. Having computed Pr for this wide range of pressure and temperature we then calculate the HDL spinodal, the coexistence line, the second critical point, and the Widom line. Supported by CONICET, UNLP, and CIC Prov.BsAs.

  4. Sound propagation in liquid water: The puzzle continues Francesco Sciortino

    E-print Network

    Sciortino, Francesco

    Sound propagation in liquid water: The puzzle continues Francesco Sciortino CRS4, Centro di Ricerca; accepted 16 November 1993) Experimental and simulation studies of sound propagation in water have observed, at large wave vectors k (k > 0.25 A-`), a longitudinal sound mode with a velocity of about 3500 m/s, more

  5. Searching for liquid water in Europa by using surface observatories.

    PubMed

    Khurana, Krishan K; Kivelson, Margaret G; Russell, Christopher T

    2002-01-01

    Liquid water, as far as we know, is an indispensable ingredient of life. Therefore, locating reservoirs of liquid water in extraterrestrial bodies is a necessary prerequisite to searching for life. Recent geological and geophysical observations from the Galileo spacecraft, though not unambiguous, hint at the possibility of a subsurface ocean in the Jovian moon Europa. After summarizing present evidence for liquid water in Europa, we show that electromagnetic and seismic observations made from as few as two surface observatories comprising a magnetometer and a seismometer offer the best hope of unambiguous characterization of the three-dimensional structure of the ocean and the deeper interior of this icy moon. The observatories would also help us infer the composition of the icy crust and the ocean water. PMID:12449858

  6. The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water. II

    SciTech Connect

    Limmer, David T.; Chandler, David

    2013-06-07

    This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys.135, 134503 (2011) and preprint http://arxiv.org/abs/arXiv:1107.0337 (2011)]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, Stillinger-Weber silicon, and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate using both analytical theory and computer simulation. For the latter, we describe robust methods for computing reversible free energy surfaces, and we consider effects of electrostatic boundary conditions. We show that sensible alterations of models and boundary conditions produce no qualitative changes in low-temperature phase behaviors of these systems, only marginal changes in equations of state. On the other hand, we show that altering sampling time scales can produce large and qualitative non-equilibrium effects. Recent reports of evidence of a liquid-liquid critical point in computer simulations of supercooled water are considered in this light.

  7. Structure and Depletion at Fluorocarbon and Hydrocarbon/Water Liquid/Liquid Interfaces

    SciTech Connect

    Kashimoto,K.; Yoon, J.; Hou, B.; Chen, C.; Lin, B.; Aratono, M.; Takiue, T.; Schlossman, M.

    2008-01-01

    The results of x-ray reflectivity studies of two oil/water (liquid/liquid) interfaces are inconsistent with recent predictions of the presence of a vaporlike depletion region at hydrophobic/aqueous interfaces. One of the oils, perfluorohexane, is a fluorocarbon whose superhydrophobic interface with water provides a stringent test for the presence of a depletion layer. The other oil, heptane, is a hydrocarbon and, therefore, is more relevant to the study of biomolecular hydrophobicity. These results are consistent with the subangstrom proximity of water to soft hydrophobic materials.

  8. A Mechanism for Recent Production of Liquid Water on Mars

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Bridges, N. T.

    2003-01-01

    Though Mars is a cold, dry planet, with respect to the thermal stability of liquid water at low altitudes it is not terribly different from comparably cold places on Earth. In dry air such water would evaporate faster on Mars, at a rate comparable to a 60 C hot spring on Earth, but the heat loss associated with that evaporation would be mitigated by the poor thermal convection in the thin Martian air. Even at higher altitudes where the atmospheric pressure does not reach the triple point of water, liquid water might theoretically exist in a low-vapor pressure form such as wet soil, in a briny solution, or simply under a layer of dust or snow. The theoretical stability of liquid water does not suggest its occurrence, either on Mars or in Antarctica. In fact, global models have suggested that locations capable of providing sufficient heat for melting are, precisely for that reason, too dry for water to be present. However, the temperature of irregular local structures such as trenches or craters can be markedly warmer than those of the uniform surfaces of global models. The work described here suggests a plausible scenario in which seasonal liquid water might be produced locally, in sheltered locations, through a process of condensation, cold-trapping, buffering, and melting. While the amounts produced in the present climate would be small, copious amounts of meltwater may have been produced at other phases of the orbital cycle, as recently as 20,000 years ago.

  9. Ion transport through a water-organic solvent liquid-liquid interface: a simulation study.

    PubMed

    Holmberg, Nico; Sammalkorpi, Maria; Laasonen, Kari

    2014-06-01

    Ion interactions and partitioning at the water-organic solvent interface and the solvation characteristics have been characterized by molecular dynamics simulations. More precisely, we study sodium cation transport through water-cyclohexane, water-1,2-dichloroethane, and water-pentanol interfaces, providing a systematic characterization of the ion interfacial behavior including barriers against entering the organic phase as well as characterization of the interfaces in the presence of the ions. We find a sodium depletion zone at the liquid-liquid interface and persistent hydration of the cation when entering the organic phase. The barrier against the cation entering the organic phase and ion hydration depend strongly on specific characteristics of the organic solvent. The strength of both barrier and hydration shell binding (persistence of the cation hydration) go with the polarity and the surface tension at the interface, that is, both decrease in order cyclohexane-water > 1,2-dichloroethane-water > pentanol-water. However, the size of the hydration shell measured in water molecules bound by the cation entering the less polar phase behaves oppositely, with the cation carrying most water to the pentanol phase and a much smaller in size, but very tightly bound water shell to cyclohexane. We discuss the implications of the observations for ion transport through the interface of immiscible or poorly miscible liquids and for materials of confined ion transport such as ion conduction membranes or biological ion channel activity. PMID:24814815

  10. Electronic Structure of Liquid Water and a Platinum Surface

    E-print Network

    Tamblyn, Isaac

    2014-01-01

    Many-body perturbation theory within the G$_0$W$_0$ approximation is used to determine molecular orbital level alignment at a liquid water/Pt(111) interface generated through $ab~ initio$ molecular dynamics. Molecular orbital energy levels are shown to depend both on the position of H$_2$O molecules within the liquid relative to the surface and the details of their local bonding environment. Standard density functional theory calculations disagree qualitatively with level alignment predicted by many-body perturbation theory.

  11. Liquid Polyamorphism: Some Unsolved Puzzles of Water in Bulk, Nanoconfined, and Biological Environments

    E-print Network

    Stanley, H. Eugene

    Liquid Polyamorphism: Some Unsolved Puzzles of Water in Bulk, Nanoconfined, and Biological of the liquid-liquid critical point in (i) Two models of water, TIP5P and ST2, which display a first order liquid-liquid phase transition at low temperatures; (ii) the Jagla model, a spherically symmetric two

  12. 17 novel polymorphic microsatellite markers for the giant water bug, Abedus herberti (Belostomatidae).

    PubMed

    Daly-Engel, T S; Smith, R L; Finn, D S; Knoderbane, M E; Phillipsen, I C; Lytle, D A

    2012-12-01

    The giant water bug (Abedus herberti) is a large flightless insect that is a keystone predator in aridland aquatic habitats. Extended droughts, possibly due to climate change and groundwater pumping, are causing once-perennial aquatic habitats to dry, resulting in serious conservation concern for some populations. A. herberti also exhibits exclusive male parental care, which has made it a model organism for studying mating systems evolution. Here we describe 17 novel polymorphic microsatellite loci developed for A. herberti. Number of alleles per locus ranged from 2 to 15, and average observed and expected heterozygosities were 0.579 and 0.697, respectively. These loci can successfully resolve both population genetic structure among sites separated by 3-100 km (F ST = 0.08-0.21, P < 0.0001), and divergent mating strategies within local populations, making them highly useful for conservation genetics studies of this vulnerable species. PMID:24077753

  13. Local Structure Analysis in $Ab$ $Initio$ Liquid Water

    E-print Network

    Biswajit Santra; Robert A. DiStasio Jr.; Fausto Martelli; Roberto Car

    2015-02-27

    Within the framework of density functional theory, the inclusion of exact exchange and non-local van der Waals/dispersion (vdW) interactions is crucial for predicting a microscopic structure of ambient liquid water that quantitatively agrees with experiment. In this work, we have used the local structure index (LSI) order parameter to analyze the local structure in such highly accurate $ab$ $initio$ liquid water. At ambient conditions, the LSI probability distribution, P($I$), was unimodal with most water molecules characterized by more disordered high-density-like local environments. With thermal excitations removed, the resultant bimodal P($I$) in the inherent potential energy surface (IPES) exhibited a 3:1 ratio between high- and low-density-like molecules, with the latter forming small connected clusters amid the predominant population. By considering the spatial correlations and hydrogen bond network topologies $among$ water molecules with the same LSI identities, we demonstrate that the signatures of the experimentally observed low- (LDA) and high-density (HDA) amorphous phases of ice are present in the IPES of ambient liquid water. Analysis of the LSI autocorrelation function uncovered a persistence time of $\\sim$ 4 ps---a finding consistent with the fact that natural thermal fluctuations are responsible for transitions between these distinct yet transient local aqueous environments in ambient liquid water.

  14. Liquid marble and water droplet interactions and stability.

    PubMed

    Ueno, Kazuyuki; Bournival, Ghislain; Wanless, Erica J; Nakayama, Saori; Giakoumatos, Emma C; Nakamura, Yoshinobu; Fujii, Syuji

    2015-10-21

    The interactions between two individual water droplets were investigated in air using a combination of coalescence rig and high speed video camera. This combination allows the visualization of droplet coalescence dynamics with millisecond resolution which provides information on droplet stability. Bare water droplets coalesced rapidly upon contact, while droplet stability was achieved by coating the droplets with polystyrene particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] hairs (PDEA-PS particles) to form liquid marbles. The asymmetric interaction of a water droplet (pH 3 or 10) armoured with the PDEA-PS particles (liquid marble) with a bare droplet at pH 3 exhibited intermediate stability with coalescence observed following an induction time. The induction time was longer for the pH 10 liquid marble, where the PDEA-PS particles have a hydrophobic surface, than in the case of a pH 3 liquid marble, where the PDEA-PS particles have a hydrophilic surface. Furthermore, film formation of PDEA-PS particles on the liquid marble surface with toluene vapour confirmed capsule formation which prevented coalescence with the neighbouring water droplet instead wetting the capsule upon contact within 3 milliseconds. This study illuminates the stability of individual particle-stabilized droplets and has potential impact on processes and formulations which involve their interaction. PMID:26296006

  15. Self-Assembly and Orientation of Hydrogen-Bonded Oligothiophene Polymorphs at Liquid?Membrane?Liquid Interfaces

    SciTech Connect

    Tevis, Ian D.; Palmer, Liam C.; Herman, David J.; Murray, Ian P.; Stone, David A.; Stupp, Samuel I.

    2012-03-15

    One of the challenges in organic systems with semiconducting function is the achievement of molecular orientation over large scales. We report here on the use of self-assembly kinetics to control long-range orientation of a quarterthiophene derivative designed to combine intermolecular {pi}-{pi} stacking and hydrogen bonding among amide groups. Assembly of these molecules in the solution phase is prevented by the hydrogen-bond-accepting solvent tetrahydrofuran, whereas formation of H-aggregates is facilitated in toluene. Rapid evaporation of solvent in a solution of the quarterthiophene in a 2:1:1 mixture of 1,4-dioxane/tetrahydrofuran/toluene leads to self-assembly of kinetically trapped mats of bundled fibers. In great contrast, slow drying in a toluene atmosphere leads to the homogeneous nucleation and growth of ordered structures shaped as rhombohedra or hexagonal prisms depending on concentration. Furthermore, exceedingly slow delivery of toluene from a high molecular weight polymer solution into the system through a porous aluminum oxide membrane results in the growth of highly oriented hexagonal prisms perpendicular to the interface. The amide groups of the compound likely adsorb onto the polar aluminum oxide surface and direct the self-assembly pathway toward heterogeneous nucleation and growth to form hexagonal prisms. We propose that the oriented prismatic polymorph results from the synergy of surface interactions rooted in hydrogen bonding on the solid membrane and the slow kinetics of self-assembly. These observations demonstrate how self-assembly conditions can be used to guide the supramolecular energy landscape to generate vastly different structures. These fundamental principles allowed us to grow oriented prismatic assemblies on transparent indium-doped tin oxide electrodes, which are of interest in organic electronics.

  16. Solid-liquid critical behavior of water in nanopores.

    PubMed

    Mochizuki, Kenji; Koga, Kenichiro

    2015-07-01

    Nanoconfined liquid water can transform into low-dimensional ices whose crystalline structures are dissimilar to any bulk ices and whose melting point may significantly rise with reducing the pore size, as revealed by computer simulation and confirmed by experiment. One of the intriguing, and as yet unresolved, questions concerns the observation that the liquid water may transform into a low-dimensional ice either via a first-order phase change or without any discontinuity in thermodynamic and dynamic properties, which suggests the existence of solid-liquid critical points in this class of nanoconfined systems. Here we explore the phase behavior of a model of water in carbon nanotubes in the temperature-pressure-diameter space by molecular dynamics simulation and provide unambiguous evidence to support solid-liquid critical phenomena of nanoconfined water. Solid-liquid first-order phase boundaries are determined by tracing spontaneous phase separation at various temperatures. All of the boundaries eventually cease to exist at the critical points and there appear loci of response function maxima, or the Widom lines, extending to the supercritical region. The finite-size scaling analysis of the density distribution supports the presence of both first-order and continuous phase changes between solid and liquid. At around the Widom line, there are microscopic domains of two phases, and continuous solid-liquid phase changes occur in such a way that the domains of one phase grow and those of the other evanesce as the thermodynamic state departs from the Widom line. PMID:26100904

  17. Resurfacing of Ganymede by Liquid-Water Volcanism

    NASA Technical Reports Server (NTRS)

    Showman, A. P.; Mosqueira, I.; Head, J. W., III

    2004-01-01

    A long-popular model for producing Ganymede s bright terrain involves flooding of low-lying graben with liquid water, slush, or warm, soft ice. The model suffers from major problems, however, including the absence of obvious near-surface heat sources, the negative buoyancy of liquid water, and the lack of a mechanism for confining the flows to graben floors. We show that topography - such as a global set of graben - causes subsurface (a hydrostatic) pressure gradients that can "suck" subsurface liquid water upward onto the floors of topographic lows (graben). As the low areas become full, the pressure gradients disappear and the resurfacing ceases. This provides an explanation for the observed straight dark-bright terrain boundaries: water cannot overflow the graben, so surfacing rarely embays craters and other rough topography. Subsurface liquid water must exist for the scenario to exist, of course, and is plausibly provided by tidal heating during an ancient orbital resonance. This abstract is a summary of Showman et al. recently submitted to Icarus.

  18. Entropy of Liquid Water from Ab Initio Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Spanu, Leonardo; Zhang, Cui; Galli, Giulia

    2012-02-01

    The debate on the structural properties of water has been mostly based on the calculation of pair correlation functions. However, the simulation of thermodynamic and spectroscopic quantities may be of great relevance for the characterization of liquid water properties. We have computed the entropy of liquid water using a two-phase thermodynamic model and trajectories generated by ab initio molecular dynamics simulations [1]. In an attempt to better understand the performance of several density functionals in simulating liquid water, we have performed ab initio molecular dynamics using semilocal, hybrid [2] and van der Waals density functionals [3]. We show that in all cases, at the experimental equilibrium density and at temperatures in the vicinity of 300 K, the computed entropies are underestimated, with respect to experiment, and the liquid exhibits a degree of tetrahedral order higher than in experiments. We also discuss computational strategies to simulate spectroscopic properties of water, including infrared and Raman spectra.[4pt] [1] C.Zhang, L.Spanu and G.Galli, J.Phys.Chem. B 2011 (in press)[0pt] [2] C.Zhang, D.Donadio, F.Gygi and G.Galli, J. Chem. Theory Comput. 7, 1443 (2011)[0pt] [3] C.Zhang, J.Wu, G.Galli and F.Gygi, J. Chem. Theory Comput. 7, 3061 (2011)

  19. Satellite Remote Sensing of the Liquid Water Sensitivity in Water Clouds

    NASA Technical Reports Server (NTRS)

    Han, Qing-Yuan; Rossow, William B.; Welch, Ronald; Zeng, Jane; Jansen, James E. (Technical Monitor)

    2001-01-01

    In estimation of the aerosol indirect effect, cloud liquid water path is considered either constant (Twomey effect) or increasing with enhanced droplet number concentrations (drizzle-suppression effect, or Albrecht effect) if cloud microphysics is the prevailing mechanism during the aerosol-cloud interactions. On the other hand, if cloud thermodynamics and dynamics are considered, the cloud liquid water path may be decreased with increasing droplet number concentration, which is predicted by model calculations and observed in ship-track and urban influence studies. This study is to examine the different responses of cloud liquid water path to changes of cloud droplet number concentration. Satellite data (January, April, July and October 1987) are used to retrieve the cloud liquid water sensitivity, defined as the changes of liquid water path versus changes of column droplet number concentrations. The results of a global survey reveal that 1) in at least one third of the cases the cloud liquid water sensitivity is negative, and the regional and seasonal variations of the negative liquid water sensitivity are consistent with other observations; 2) cloud droplet sizes are always inversely proportional to column droplet number concentrations. Our results suggest that an increase of cloud droplet number concentration leads to reduced cloud droplet size and enhanced evaporation, which weakens the coupling between water clouds and boundary layer in warm zones, decreases water supply from surface and desiccates cloud liquid water. Our results also suggest that the current evaluations of negative aerosol indirect forcing by global climate models (GCM), which are based on Twomey effect or Albrecht effect, may be overestimated.

  20. Coherent structures in liquid water close to hydrophilic surfaces

    NASA Astrophysics Data System (ADS)

    Del Giudice, Emilio; Tedeschi, Alberto; Vitiello, Giuseppe; Voeikov, Vladimir

    2013-06-01

    Quantum Electrodynamics (QED) predicts the occurrence of a number of coherent dynamical phenomena in liquid water. In the present paper we focus our attention on the joint coherent oscillation of the almost free electrons produced by the coherent oscillation of the electron clouds of water molecules, which has been described in previous publications, and of the negative electric charges lying on the solid surfaces wet by water. This joint coherent oscillation gives rise to a number of phenomenological consequences which are found to exist in the physical reality and coincide with the layers of Exclusion Zone (EZ) water experimentally observed close to hydrophilic surfaces.

  1. Local Structure Analysis in $Ab$ $Initio$ Liquid Water

    E-print Network

    Santra, Biswajit; Martelli, Fausto; Car, Roberto

    2015-01-01

    Within the framework of density functional theory, the inclusion of exact exchange and non-local van der Waals/dispersion (vdW) interactions is crucial for predicting a microscopic structure of ambient liquid water that quantitatively agrees with experiment. In this work, we have used the local structure index (LSI) order parameter to analyze the local structure in such highly accurate $ab$ $initio$ liquid water. At ambient conditions, the LSI probability distribution, P($I$), was unimodal with most water molecules characterized by more disordered high-density-like local environments. With thermal excitations removed, the resultant bimodal P($I$) in the inherent potential energy surface (IPES) exhibited a 3:1 ratio between high- and low-density-like molecules, with the latter forming small connected clusters amid the predominant population. By considering the spatial correlations and hydrogen bond network topologies $among$ water molecules with the same LSI identities, we demonstrate that the signatures of th...

  2. Chiral Ordering in Supercooled Liquid Water and Amorphous Ice

    NASA Astrophysics Data System (ADS)

    Matsumoto, Masakazu; Yagasaki, Takuma; Tanaka, Hideki

    2015-11-01

    The emergence of homochiral domains in supercooled liquid water is presented using molecular dynamics simulations. An individual water molecule possesses neither a chiral center nor a twisted conformation that can cause spontaneous chiral resolution. However, an aggregation of water molecules will naturally give rise to a collective chirality. Such homochiral domains possess obvious topological and geometrical orders and are energetically more stable than the average. However, homochiral domains cannot grow into macroscopic homogeneous structures due to geometrical frustrations arising from their icosahedral local order. Homochiral domains are the major constituent of supercooled liquid water and the origin of heterogeneity in that substance, and are expected to be enhanced in low-density amorphous ice at lower temperatures.

  3. Updated model for dielectric response function of liquid water

    PubMed Central

    Dingfelder, Michael

    2013-01-01

    A modified and updated version of the model of the dielectric response function of liquid water as currently implemented in the PARTRAC code is presented. The updated version takes advantage of the newer experimental information from the Sendai group and implements some improvements in modeling and usability. PMID:23415106

  4. Confirmation of enhanced anion concentration at the liquid water surface

    E-print Network

    Cohen, Ronald C.

    anions to reside at the surface, whereas the cations and non-polar- izable anions remain in the interiorConfirmation of enhanced anion concentration at the liquid water surface Poul B. Petersen, Richard anions. Here we present the first direct experimental veri- fication of this prediction. Enhanced azide ð

  5. Aircraft Measurements of Cloud Liquid Water Content using the Forward

    E-print Network

    Delene, David J.

    ) On the Right Wing of the Citation Research Aircraft #12;The beam splitter divides the scattered light onto twoAircraft Measurements of Cloud Liquid Water Content using the Forward Scattering Spectrometer Probe*DOF*BD*(Tc/Ts) TAS ­ Aircraft True Air Speed (~100 m/s) DOF ­ FSSP Depth of Field (~2.9 mm) BD ­ Laser Beam Diameter

  6. Molecular dynamics of the water liquid-vapor interface

    NASA Technical Reports Server (NTRS)

    Wilson, M. A.; Pohorille, A.; Pratt, L. R.; MacElroy, R. D. (Principal Investigator)

    1987-01-01

    The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C2 nu molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 +/- 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

  7. Dynamics of Isolated Water Molecules in a Sea of Ions in a Room Temperature Ionic Liquid

    E-print Network

    Fayer, Michael D.

    Dynamics of Isolated Water Molecules in a Sea of Ions in a Room Temperature Ionic Liquid Daryl B. In such studies, water interacts with ions but also with a large number of other water molecules. Room temperature that are liquids at room temperature. Because RTILs are themselves liquids, it is possible to study water

  8. Glass transition in biomolecules and the liquid-liquid critical point of water

    E-print Network

    P. Kumar; Z. Yan; L. Xu; M. G. Mazza; S. V. Buldyrev; S. -H. Chen; S. Sastry; H. E. Stanley

    2006-08-28

    Using molecular dynamics simulations, we investigate the relation between the dynamic transitions of biomolecules (lysozyme and DNA) and the dynamic and thermodynamic properties of hydration water. We find that the dynamic transition of the macromolecules, sometimes called a ``protein glass transition'', occurs at the temperature of dynamic crossover in the diffusivity of hydration water, and also coincides with the maxima of the isobaric specific heat $C_P$ and the temperature derivative of the orientational order parameter. We relate these findings to the hypothesis of a liquid-liquid critical point in water. Our simulations are consistent with the possibility that the protein glass transition results from crossing the Widom line, which is defined as the locus of correlation length maxima emanating from the hypothesized second critical point of water.

  9. Polymorphism and polyamorphism in bilayer water confined to slit nanopore under high pressure

    PubMed Central

    Bai, Jaeil; Zeng, Xiao Cheng

    2012-01-01

    A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I–ice XIV) and at least 3 glassy forms of water, namely, low-density amorphous, high-density amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7–9 Å apart, numerous bilayer (BL) ices (or polymorphs) can arise [e.g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on graphene/Pt(111) substrate has been achieved experimentally. Herein, we report computer simulation evidence of pressure-induced amorphization from BL-ice I to BL-amorphous and then to BL-VHDA2 at 250 K and 3 GPa. In particular, BL-VHDA2 can transform into BL-VHDA1 via decompression from 3 to 1.5 GPa at 250 K. This phenomenon of 2D polyamorphic transition is akin to the pressure-induced amorphization in 3D ice (e.g., from hexagonal ice to HDA and then to VHDA via isobaric annealing). Moreover, when the BL-ice I is compressed instantly to 6 GPa, a new very-high-density BL ice is formed. This new phase of BL ice can be viewed as an array of square ice nanotubes. Insights obtained from pressure-induced amorphization and crystallization of confined water offer a guide with which to seek a thermodynamic path to grow a new form of methane clathrate whose BL ice framework exhibits the Archimedean 4?82 (square-octagon) pattern. PMID:23236178

  10. Interfacial water - the only liquid water in the upper martian subsurface

    NASA Astrophysics Data System (ADS)

    Möhlmann, Diedrich

    It is shown, after introducing the physics of liquid water on and in the upper surface of Mars, that interfacial water is the only liquid water on present days Mars. Water ice on a mineral surface is not generally stable. A microscopic liquid layer of "undercooled" liquid water must in a large range of temperatures evolve between ice and mineral due to the attractive van der Waals forces driven pressure, acting upon the ice. This pressure is followed by a freezing point depression, which may let the water liquid down to temperatures of about 180 K on Mars. This is the only liquid water, what can be expected to exist, at least temporarily, on recent Mars. The physics behind and the resulting "band of possible liquid water" between minimum liquidus temperature and the slightly higher frost point temperature in the p-T-parameter-space is described by a "Sandwich-model" with layers of ice (top), liquid water (in between) and a mineral surface (bottom). It is shown that the thickness or number of mono-layers of the interfacial water depends on temperature and atmospheric relative humidity. The maximum value of mono-layers is reached directly below the frost point temperature. The derived equations for the sandwich model fit well to a known phenomenological relation between thickness of the liquid layer and relative humidity. The curvature of grain surfaces is shown to have no remarkable effects for particles in the µm-range and larger. The freezing point depression for van der Waals force governed interfacial water is shown to depend on the value of the Hamaker constant, on the latent heat of solidification, on the mass density of water ice, and on the thickness of the liquid layer. This relation fits well to a known phenomenological relation between freezing point depression and thickness of the liquid layer. The derived equation shows that the lower limiting temperature of the liquid phase reaches about 180 K under martian conditions having an atmospheric water content of around 10 pr µm. Furthermore, an "Equilibrium moisture content" (EMC)/"Equilibrium Relative Humidity" (ERH) relation for the water content of martian soil has been derived, which relates, for equilibrium conditions, soil water content and atmospheric relative humidity. This relation indicates that the content of liquid interfacial water in the upper surface of Mars can reach up to 10% by weight and more in course of saturation during night hours, and it can be of about 2 % by weight during the dry daytime hours. The application of the results of the sandwich-model to thermo-physical conditions on Mars shows that the thickness of frost-layers, which can evolve over several hours on cooling surface parts of Mars, is for low latitudes typically of the order or a few tenths of one millimetre or less. This is in agreement with observations. Physical, as rheological, and chemical, as photo-catalytic, and hypothetical biological consequences of the presence of undercooled liquid interfacial water in the upper martian surface are discussed.

  11. Probing Hydrophilic Interface of Solid/Liquid-Water by Nanoultrasonics

    PubMed Central

    Mante, Pierre-Adrien; Chen, Chien-Cheng; Wen, Yu-Chieh; Chen, Hui-Yuan; Yang, Szu-Chi; Huang, Yu-Ru; -Ju Chen, I.; Chen, Yun-Wen; Gusev, Vitalyi; Chen, Miin-Jang; Kuo, Jer-Lai; Sheu, Jinn-Kong; Sun, Chi-Kuang

    2014-01-01

    Despite the numerous devoted studies, water at solid interfaces remains puzzling. An ongoing debate concerns the nature of interfacial water at a hydrophilic surface, whether it is more solid-like, ice-like, or liquid-like. To answer this question, a complete picture of the distribution of the water molecule structure and molecular interactions has to be obtained in a non-invasive way and on an ultrafast time scale. We developed a new experimental technique that extends the classical acoustic technique to the molecular level. Using nanoacoustic waves with a femtosecond pulsewidth and an ångström resolution to noninvasively diagnose the hydration structure distribution at ambient solid/water interface, we performed a complete mapping of the viscoelastic properties and of the density in the whole interfacial water region at hydrophilic surfaces. Our results suggest that water in the interfacial region possesses mixed properties and that the different pictures obtained up to now can be unified. Moreover, we discuss the effect of the interfacial water structure on the abnormal thermal transport properties of solid/liquid interfaces. PMID:25176017

  12. Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

    SciTech Connect

    Bignell, L. J.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; Rosero, R.; Vigdor, S.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-10-19

    Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % and 1.31 ± 0.59 % after ? 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.

  13. Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

    DOE PAGESBeta

    Bignell, L. J.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; Rosero, R.; Vigdor, S.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-10-19

    Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % andmore »1.31 ± 0.59 % after ? 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.« less

  14. Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

    NASA Astrophysics Data System (ADS)

    Bignell, L. J.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; Rosero, R.; Vigdor, S.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-10-01

    Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % and 1.31 ± 0.59 % after 0? 80 Gy of proton dose, respectively. Whilst some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.

  15. Water Tank with Capillary Air/Liquid Separation

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Smith, Frederick; Edeen, Gregg; Almlie, Jay C.

    2010-01-01

    A bladderless water tank (see figure) has been developed that contains capillary devices that allow it to be filled and emptied, as needed, in microgravity. When filled with water, the tank shields human occupants of a spacecraft against cosmic radiation. A membrane that is permeable by air but is hydrophobic (neither wettable nor permeable by liquid water) covers one inside surface of the tank. Grooves between the surface and the membrane allow air to flow through vent holes in the surface as the tank is filled or drained. A margin of wettable surface surrounds the edges of the membrane, and all the other inside tank surfaces are also wettable. A fill/drain port is located in one corner of the tank and is covered with a hydrophilic membrane. As filling begins, water runs from the hydrophilic membrane into the corner fillets of the tank walls. Continued filling in the absence of gravity will result in a single contiguous air bubble that will be vented through the hydrophobic membrane. The bubble will be reduced in size until it becomes spherical and smaller than the tank thickness. Draining the tank reverses the process. Air is introduced through the hydrophobic membrane, and liquid continuity is maintained with the fill/drain port through the corner fillets. Even after the tank is emptied, as long as the suction pressure on the hydrophilic membrane does not exceed its bubble point, no air will be drawn into the liquid line.

  16. Freezing of liquid water under combined compression and electric fields

    NASA Astrophysics Data System (ADS)

    Stafford, S.; Bland, S.; Dolan, D.; Eakins, D.; Institute of Shock Physics Collaboration; Sandia National Labs Collaboration

    2013-06-01

    The melt curves of materials hold rich information concerning phase stability, coexistence, and other kinetics, typically studied through heating and cooling. Compression-induced solidification exposes new kinetics, yet is a practical challenge due to adiabatic heating. Water has a large heat capacity and many solid phases, making it a good candidate for compression freezing. Optical transmission measurements and high-speed imaging have demonstrated that water can freeze on nanosecond time scales. Being highly polar, freezing in water is strongly influenced by electric fields at atmospheric pressure. However, the role of external electric fields in freezing has yet to be determined at high pressure. We present experimental and theoretical results from our attempts to transform liquid water into solid ice under rapid compression. To minimize heating, samples are quasi-isentropically compressed via multiple shock or ramp wave compression. An external electric field applied to the sample imparts local order to the system, influencing solidification onset and growth. Classical molecular dynamic simulations show significant ordering effects at V/nm field strength, well above the dielectric strength of water. We present work that to address this issue. Freezing of liquid water under combined compression and electric fields.

  17. Reaction of catalytic oxidation by liquid water and its application to waste water purification

    SciTech Connect

    Ioffe, I.I.; Rubinskaya, E.V.

    1997-06-01

    In this paper the results of experiments and some considerations of theoretical and practical problems devoted to a new type of chemical reaction--oxidation of organic substances by liquid water with the aid of noble metal catalyst--are given. Some problems of application such as reaction to self-purification of industrial waste waters are also considered.

  18. Liquid water transport in fuel cell gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bazylak, Aimy Ming Jii

    Liquid water management has a major impact on the performance and durability of the polymer electrolyte membrane fuel cell (PEMFC). The gas diffusion layer (GDL) of a PEMFC provides pathways for mass, heat, and electronic transport to and from the catalyst layers and bipolar plates. When the GDL becomes flooded with liquid water, the PEMFC undergoes mass transport losses that can lead to decreased performance and durability. The work presented in this thesis includes contributions that provide insight into liquid water transport behaviour in and on the surface of the GDL, as well as insight into how future GDLs could be designed to enhance water management. The effects of compression on liquid water transport in the GDL and on the microstructure of the GDL are presented. It was found that compressed regions of the GDL provided preferential locations for water breakthrough, while scanning electron microscopy (SEM) imaging revealed irreversible damage to the GDL due to compression at typical fuel cell assembly pressures. The dynamic behaviour of droplet emergence and detachment in a simulated gas flow channel are also presented. It was found that on an initially dry and hydrophobic GDL, small droplets emerged and detached quickly from the GDL surface. However, over time, this water transport regime transitioned into that of slug formation and channel flooding. It was observed that after being exposed to a saturated environment, the GDL surface became increasingly prone to droplet pinning, which ultimately hindered droplet detachment and encouraged slug formation. A pore network model featuring invasion percolation with trapping was employed to evaluate the breakthrough pattern predictions of designed porous media. These designed pore networks consisted of randomized porous media with applied diagonal and radial gradients. Experimental microfluidic pore networks provided validation for the designed networks. Diagonal biasing provided a means of directing water transport in the pore network, while radially biased networks provided the additional feature of reducing the overall network saturation. Since directed water transport and reduced saturation are both beneficial for the PEMFC GDL, it was proposed that biasing of this nature could be applied to improved GDL designs. Lastly, recommendations for future extensions of this research are proposed at the end of this thesis.

  19. Ultrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x-ray spectroscopy

    E-print Network

    in living organisms exploit and depend on the un- usual properties of water. Liquid water can be regardedUltrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water

  20. Water Phase Diagram Is Significantly Altered by Imidazolium Ionic Liquid.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2014-05-15

    We report unusually large changes in the boiling temperature, saturated vapor pressure, and structure of the liquid-vapor interface for a range of 1-butyl-3-methyl tetrafluoroborate, [C4C1IM][BF4]-water mixtures. Even modest molar fractions of [C4C1IM][BF4] significantly affect the phase behavior of water, as represented, for instance, by strong negative deviations from Raoult's law, extending far beyond the standard descriptions. The investigation was carried out using classical molecular dynamics employing a specifically refined force field. The changes in the liquid-vapor interface and saturated vapor pressures are discussed at the atomistic resolution. The reported results guide the search for novel scientific and technological applications of ion-molecular systems. PMID:26270356

  1. Characterization and Modeling of a Water-based Liquid Scintillator

    E-print Network

    Lindsey J. Bignell; Dmitriy Beznosko; Milind V. Diwan; Sunej Hans; David E. Jaffe; Steven Kettell; Richard Rosero; Harry W. Themann; Brett Viren; Elizabeth Worcester; Minfang Yeh; Chao Zhang

    2015-10-22

    We have characterised Water-based Liquid Scintillator (WbLS) using low energy protons, UV-VIS absorbance, and fluorescence spectroscopy. We have also developed and validated a simulation model that describes the behaviour of WbLS in our detector configurations for proton beam energies of 2 GeV, 475 MeV, and 210 MeV and for two WbLS compositions. Our results have enabled us to estimate the light yield and ionisation quenching of WbLS, as well as to understand the influence of the wavelength shifting of Cerenkov light on our measurements. These results are relevant to the suitability of water-based liquid scintillator materials for next generation intensity frontier experiments.

  2. Characterization and Modeling of a Water-based Liquid Scintillator

    E-print Network

    Lindsey J. Bignell; Dmitriy Beznosko; Milind V. Diwan; Sunej Hans; David E. Jaffe; Steven Kettell; Richard Rosero; Harry W. Themann; Brett Viren; Elizabeth Worcester; Minfang Yeh; Chao Zhang

    2015-11-30

    We have characterised Water-based Liquid Scintillator (WbLS) using low energy protons, UV-VIS absorbance, and fluorescence spectroscopy. We have also developed and validated a simulation model that describes the behaviour of WbLS in our detector configurations for proton beam energies of 2 GeV, 475 MeV, and 210 MeV and for two WbLS compositions. Our results have enabled us to estimate the light yield and ionisation quenching of WbLS, as well as to understand the influence of the wavelength shifting of Cerenkov light on our measurements. These results are relevant to the suitability of water-based liquid scintillator materials for next generation intensity frontier experiments.

  3. Characterization and Modeling of a Water-based Liquid Scintillator

    E-print Network

    Bignell, Lindsey J; Diwan, Milind V; Hans, Sunej; Jaffe, David E; Kettell, Steven; Rosero, Richard; Themann, Harry W; Viren, Brett; Worcester, Elizabeth; Yeh, Minfang; Zhang, Chao

    2015-01-01

    We have characterised Water-based Liquid Scintillator (WbLS) using low energy protons, UV-VIS absorbance, and fluorescence spectroscopy. We have also developed and validated a simulation model that describes the behaviour of WbLS in our detector configurations for proton beam energies of 2 GeV, 475 MeV, and 210 MeV and for two WbLS compositions. Our results have enabled us to estimate the light yield and ionisation quenching of WbLS, as well as to understand the influence of the wavelength shifting of Cerenkov light on our measurements. These results are relevant to the suitability of water-based liquid scintillator materials for next generation intensity frontier experiments.

  4. Liquid Water and Thermal Activity of Enceladus' South Polar Terrain

    NASA Astrophysics Data System (ADS)

    Besserer, J.; Tobie, G.; Choblet, G.; Cadek, O.; Sotin, C.

    2008-12-01

    The endogenic activity on Enceladus is only located on a specific region at the south pole, from which jets of water vapor and ice particles have been observed. Heat power required to sustain such an activity over geologic timescales remains problematic. In a recent study, we show that only interior models with a liquid water layer at depth can explain the observed magnitude of dissipation and its particular location at the south pole (Tobie et al., Icarus, 2008). Here, we investigate the thermal stability of a localized liquid water reservoir at the rock-ice interface by performing simulations of thermal convection in three-dimensional spherical geometry. Preliminary results indicate that a total power ranging between 2.4 GW and 8 GW, comparable to the typical tidal dissipation value expected in the south polar region, is required to sustain a localized liquid zone. We are currently coupling our 3D viscoelastic tidal dissipation model to the 3D thermal convection code in order to precisely determine the associated tidal dissipation field. Preliminary results will be presented. In parallel, we investigate the likelihood of short resurfacing events by incorporating a self-lubricating, simple damage rheology using a 2D cartesian version of the code. When stress accumulation leads to the rupture of the lithosphere, a heat flow of about 200 mW.m-2, comparable to the values observed over the south pole, is observed during a relatively short period of time (< 500 kyr).

  5. Thermally driven electrokinetic energy conversion with liquid water microjets

    NASA Astrophysics Data System (ADS)

    Lam, Royce K.; Gamlieli, Zach; Harris, Stephen J.; Saykally, Richard J.

    2015-11-01

    A goal of current energy research is to design systems and devices that can efficiently exploit waste heat and utilize solar or geothermal heat energy for electrical power generation. We demonstrate a novel technique exploiting water's large coefficient of thermal expansion, wherein modest thermal gradients produce the requisite high pressure for driving fast-flowing liquid water microjets, which can effect the direct conversion of the kinetic energy into electricity and gaseous hydrogen. Waste heat in thermoelectric generating plants and combustion engines, as well as solar and geothermal energy could be used to drive these systems.

  6. Measuring Low Concentrations of Liquid Water in Soil

    NASA Technical Reports Server (NTRS)

    Buehler, Martin

    2009-01-01

    An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquidwater and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The apparatus is a special-purpose impedance spectrometer: Its design is based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and, hence, the magnitude of impedance decreases) with increasing water content.

  7. Looking for the rainbow on exoplanets covered by liquid and icy water clouds

    E-print Network

    Karalidi, T; Hovenier, J W

    2012-01-01

    Looking for the primary rainbow in starlight that is reflected by exoplanets appears to be a promising method to search for liquid water clouds in exoplanetary atmospheres. Ice water clouds, that consist of water crystals instead of water droplets, could potentially mask the rainbow feature in the planetary signal by covering liquid water clouds. Here, we investigate the strength of the rainbow feature for exoplanets that have liquid and icy water clouds in their atmosphere, and calculate the rainbow feature for a realistic cloud coverage of Earth. We calculate flux and polarization signals of starlight that is reflected by horizontally and vertically inhomogeneous Earth--like exoplanets, covered by patchy clouds consisting of liquid water droplets or water ice crystals. The planetary surfaces are black. On a planet with a significant coverage of liquid water clouds only, the total flux signal shows a weak rainbow feature. Any coverage of the liquid water clouds by ice clouds, however, dampens the rainbow fea...

  8. Transient liquid water and water activity at Gale crater on Mars

    NASA Astrophysics Data System (ADS)

    Martín-Torres, F. Javier; Zorzano, María-Paz; Valentín-Serrano, Patricia; Harri, Ari-Matti; Genzer, Maria; Kemppinen, Osku; Rivera-Valentin, Edgard G.; Jun, Insoo; Wray, James; Bo Madsen, Morten; Goetz, Walter; McEwen, Alfred S.; Hardgrove, Craig; Renno, Nilton; Chevrier, Vincent F.; Mischna, Michael; Navarro-González, Rafael; Martínez-Frías, Jesús; Conrad, Pamela; McConnochie, Tim; Cockell, Charles; Berger, Gilles; R. Vasavada, Ashwin; Sumner, Dawn; Vaniman, David

    2015-05-01

    Water is a requirement for life as we know it. Indirect evidence of transient liquid water has been observed from orbiter on equatorial Mars, in contrast with expectations from large-scale climate models. The presence of perchlorate salts, which have been detected at Gale crater on equatorial Mars by the Curiosity rover, lowers the freezing temperature of water. Moreover, perchlorates can form stable hydrated compounds and liquid solutions by absorbing atmospheric water vapour through deliquescence. Here we analyse relative humidity, air temperature and ground temperature data from the Curiosity rover at Gale crater and find that the observations support the formation of night-time transient liquid brines in the uppermost 5 cm of the subsurface that then evaporate after sunrise. We also find that changes in the hydration state of salts within the uppermost 15 cm of the subsurface, as measured by Curiosity, are consistent with an active exchange of water at the atmosphere-soil interface. However, the water activity and temperature are probably too low to support terrestrial organisms. Perchlorates are widespread on the surface of Mars and we expect that liquid brines are abundant beyond equatorial regions where atmospheric humidity is higher and temperatures are lower.

  9. Tuning the Liquid-Liquid Transition by Modulating the Hydrogen-Bond Angular Flexibility in a Model for Water

    NASA Astrophysics Data System (ADS)

    Smallenburg, Frank; Sciortino, Francesco

    2015-07-01

    We propose a simple extension of the well known ST2 model for water [F. H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)] that allows for a continuous modification of the hydrogen-bond angular flexibility. We show that the bond flexibility affects the relative thermodynamic stability of the liquid and of the hexagonal (or cubic) ice. On increasing the flexibility, the liquid-liquid critical point, which in the original ST2 model is located in the no-man's land (i.e., the region where ice is the thermodynamically stable phase) progressively moves to a temperature where the liquid is more stable than ice. Our study definitively proves that the liquid-liquid transition in the ST2 model is a genuine phenomenon, of high relevance in all tetrahedral network-forming liquids, including water.

  10. Transformation of acidic poorly water soluble drugs into ionic liquids.

    PubMed

    Balk, Anja; Wiest, Johannes; Widmer, Toni; Galli, Bruno; Holzgrabe, Ulrike; Meinel, Lorenz

    2015-08-01

    Poor water solubility of active pharmaceutical ingredients (API) is a major challenge in drug development impairing bioavailability and therapeutic benefit. This study is addressing the possibility to tailor pharmaceutical and physical properties of APIs by transforming these into tetrabutylphosphonium (TBP) salts, including the generation of ionic liquids (IL). Therefore, poorly water soluble acidic APIs (Diclofenac, Ibuprofen, Ketoprofen, Naproxen, Sulfadiazine, Sulfamethoxazole, and Tolbutamide) were converted into TBP ILs or low melting salts and compared to the corresponding sodium salts. Free acids and TBP salts were characterized by NMR and IR spectroscopy, DSC and XRPD, DVS and dissolution rate measurements, release profiles, and saturation concentration measurements. TBP salts had lower melting points and glass transition temperatures and dissolution rates were improved up to a factor of 1000 as compared to the corresponding free acid. An increase in dissolution rates was at the expense of increased hygroscopicity. In conclusion, the creation of TBP ionic liquids or solid salts from APIs is a valuable concept addressing dissolution and solubility challenges of poorly water soluble acidic compounds. The data suggested that tailor-made counterions may substantially expand the formulation scientist's armamentarium to meet challenges of poorly water soluble drugs. PMID:25976317

  11. Ab initio liquid water from PBE0 hybrid functional simulations

    NASA Astrophysics Data System (ADS)

    Li, Zhaofeng; Wu, Xifan; Car, Roberto

    2010-03-01

    For reasons of computational efficiency, so far most ab initio molecular dynamics simulations of liquid water have been based on semi-local density functional approximations, such as PBE and BLYP. These approaches yield a liquid structure that, albeit qualitatively correct, is overstructured compared to experiment, even after nuclear quantum effects have been taken into account.footnotetextJ. A. Morrone and R. Car, Phys. Rev. Lett. 101, 017801(2008) A major cause of this inaccuracy is the delocalization error associated to semi-local density functional approximations, which, as a consequence, overestimate slightly the hydrogen bond strength in the liquid. In this work we adopt the PBE0 hybrid functional approximation, which, by mixing a fraction of exact (Hartree-Fock) exchange, reduces significantly the delocalization error of semi-local functionals. Our approach is based on a numerically efficient order-N implementation of exact exchange.footnotetextX. Wu, A. Selloni, and R. Car, Phys. Rev. B 79, 085102(2009) We find that PBE0 systematically improves the agreement of the simulated liquid with experiment. Our conclusion is substantiated by the calculated radial distribution functions, H-bond statistics, and molecular dipole distribution.

  12. Gas-Liquid Coexistence in the Primitive Model for Water

    E-print Network

    F. Romano; P. Tartaglia; F. Sciortino

    2007-05-08

    We evaluate the location of the gas-liquid coexistence line and of the associated critical point for the primitive model for water (PMW), introduced by Kolafa and Nezbeda [J. Kolafa and I. Nezbeda, Mol. Phys. 61, 161 (1987)]. Besides being a simple model for a molecular network forming liquid, the PMW is representative of patchy proteins and novel colloidal particles interacting with localized directional short-range attractions. We show that the gas-liquid phase separation is metastable, i.e. it takes place in the region of the phase diagram where the crystal phase is thermodynamically favored, as in the case of articles interacting via short-range attractive spherical potentials. Differently from spherical potentials, we do not observe crystallization close to the critical point. The region of gas-liquid instability of this patchy model is significantly reduced as compared to equivalent models of spherically interacting particles, confirming the possibility of observing kinetic arrest in an homogeneous sample driven by bonding as opposed to packing.

  13. Fractionation of sugar cane with hot, compressed, liquid water

    SciTech Connect

    Allen, S.G.; Kam, L.C.; Zemann, A.J.; Antal, M.J. Jr.

    1996-08-01

    Sugar-cane bagasse and leaves (10--15 g oven-dry basis) were fractionated without size reduction by a rapid (45 s to 4 min), immersed percolation using only hot (190--230 C), compressed (P > P{sub sat}), liquid water (0.6--1.2 kg). Over 50% of the biomass could be solubilized. All of the hemicellulose, together with much of the acid-insoluble lignin in the bagasse (>60%), was solubilized, while less than 10% of the cellulose entered the liquid phase. Moreover, recovery of the hemicellulose as monomeric sugars (after a mild posthydrolysis) exceeded 80%. Less than 5% of the hemicellulose was converted to furfural. Percolation beyond that needed to immerse the biomass in hot liquid water did not result in increased solubilization. The yield of lignocellulosic residue was also not sensitive to the form of the sugar cane used (bagasse or leaves) or its moisture content (8--50%). Commercial applications for this fractionation process include the pretreatment of lignocellulosics for bioconversion to ethanol and the production of pulp and paper products.

  14. Liquid water and organics in Comets: implications for exobiology

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, J. T.; Wickramasinghe, N. C.; Wallis, M. K.

    2009-10-01

    Liquid water in comets, once considered impossible, now appears to be almost certain. New evidence has come from the discovery of clay minerals in comet Tempel 1, which compliments the indirect evidence in aqueous alteration of carbonaceous chondrites. Infrared spectral indication of clay is confirmed by modelling data in the 8-40 ?m and 8-12 ?m wavebands on the basis of mixtures of clays and organics. Radiogenic heating producing liquid water cores in freshly formed comets appears more likely on current evidence for solar system formation. A second possibility investigated here is transient melting in comets in the inner solar system, where thin crusts of asphalt-like material, formed due to solar processing and becoming hot in the daytime, can cause melting of sub-surface icy material a few centimetres deep. Supposing comets were seeded with microbes at the time of their formation from pre-solar material, there would be plenty of time for exponential amplification and evolution within the liquid interior and in the transient ponds or lakes formed as the outer layers are stripped away via sublimation.

  15. Development of a liquid-fed water resistojet

    NASA Technical Reports Server (NTRS)

    Morren, W. Earl; Stone, James R.

    1988-01-01

    A concept for a forced-flow once-through water vaporizer for application to resistojet thrusters was evaluated as an element of a laboratory model thruster and tested to investigate its operating characteristics. The vaporizer design concept employs flow swirling to attach the liquid flow to the boiler chamber wall, providing for separation of the two liquid phases. This vaporizer was modified with a nozzle and a centrally-located heater to facilitate vaporization, superheating, and expansion of the propellant, allowing it to function as a resistojet. Performance was measured at thrust levels ranging from 170 to 360 mN and at power levels ranging from 443 to 192 W. Maximum measured specific impulse was 192 sec.

  16. Development of a liquid-fed water resistojet

    NASA Technical Reports Server (NTRS)

    Morren, W. Earl; Stone, James R.

    1988-01-01

    A concept for a forced-flow once-through water vaporizer for application to resistojet thrusters was evaluated as an element of a laboratory model thruster and tested to investigate its operating characteristics. The vaporizer design concept employs flow swirling to attach the liquid flow to the boiler chamber wall, providing for separation of the two liquid phases. This vaporizer was modified with a nozzle and a centrally-located heater to facilitatite vaporization, superheating, and expansion of the propellant, allowing it to function as a resistojet. Performance was measured at thrust levels ranging from 170 to 360 mN and at power levels ranging from 443 to 192 W. Maximum measured specific impulse was 192 sec.

  17. Liquid-liquid coexistence and crystallization in supercooled ST2 water

    NASA Astrophysics Data System (ADS)

    Martelli, Fausto; Palmer, Jeremy; Debenedetti, Pablo; Car, Roberto

    2014-03-01

    We have computed the free energy landscape of ST2 water in the supercooled regime (228.6 K and 2.4 kbar) using several state-of-the-art computational techniques, including umbrella sampling and metadynamics. Such results conclusively demonstrate coexistence between two liquid phases, a high-density liquid (HDL) and a low-density liquid (HDL), which are metastable with respect to cubic ice. We show that the three phases have distinct structural features characterized by the local structure index and ring statistics. We also find that ice nucleation, should it occur, does so from the low-density liquid. Interestingly, we find that the number of 6-member rings increases monotonically along the path from HDL to LDL, while non-monotonic behavior is observed near the saddle point along the LDL-ice Ic path. This behavior indicates a complex re-arrangement of the H-bond network, followed by progressive crystallization. DOE: DE-SC0008626 (F. M. and R.C.)

  18. Diurnal cycle of liquid water path over the subtropical and tropical oceans

    E-print Network

    Wood, Robert

    Diurnal cycle of liquid water path over the subtropical and tropical oceans R. Wood, C. S.1029/ 2002GL015371, 2002. 1. Introduction [2] The diurnal cycle of cloud cover and liquid water has important; revised 26 June 2002; accepted 11 July 2002; published XX Month 2002. [1] The diurnal cycle of liquid

  19. Gibbs free energy of liquid water derived from infrared measurements.

    PubMed

    Bergonzi, Isabelle; Mercury, Lionel; Brubach, Jean-Blaise; Roy, Pascale

    2014-12-01

    Infrared spectra of pure liquid water were recorded from 20 cm(-1) to 4000 cm(-1) at temperatures ranging from 263 K to 363 K. The evolution of connectivity, libration, bending and OH stretching bands as a function of temperature follows the evolution of the inter-molecular dynamics, and so gives insight into the internal energy averaged over the measurement time and space. A partition function, which takes into account the inter-molecular and intra-molecular modes of vibration of water, all variable with the molecular networking, was developed to convert this vibrational absorption behavior of water into its macroscopic Gibbs free energy, assuming the vibrational energy to feature most of the water energy. Calculated Gibbs free energies along the thermal range are in close agreement with the literature values up to 318 K. Above this temperature, contributions specific to the non H-bonded molecules must be involved to closely fit the thermodynamics of water. We discussed this temperature threshold in relation to the well-known isosbestic point. Generally speaking, our approach is valuable to convert the IR molecular data into mean field properties, a quantitative basis to predict how water behaves in natural or industrial settings. PMID:25319142

  20. Gas hydrate inhibition by perturbation of liquid water structure

    PubMed Central

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-01-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates. PMID:26082291

  1. Gas hydrate inhibition by perturbation of liquid water structure

    NASA Astrophysics Data System (ADS)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  2. Gas hydrate inhibition by perturbation of liquid water structure.

    PubMed

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-01-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates. PMID:26082291

  3. Deeply-cooled water under strong confinement: neutron scattering investigations and the liquid-liquid critical point hypothesis.

    PubMed

    Bertrand, Christopher E; Zhang, Yang; Chen, Sow-Hsin

    2013-01-21

    We present an overview of recent experimental investigations into the properties of strongly-confined water below the bulk freezing temperature. Under strong confinement, the crystallization of water is completely suppressed and the behavior of the confined liquid state can be measured at temperatures and pressures that are inaccessible to the bulk liquid. We focus on two phenomena that have recently been discovered in strongly confined water: the density minimum and the fragile-to-strong dynamic crossover. All experimental results seem to indicate that confined water undergoes a unique kind of transition below the bulk homogeneous nucleation limit. Much of the recent work on deeply-cooled water under strong confinement has been motivated by the liquid-liquid critical point (LLCP) hypothesis. We discuss this hypothesis in the context of the various experimental findings. PMID:23184078

  4. Identification of dimethoate-containing water using partitioned dispersive liquid-liquid microextraction coupled with near-infrared spectroscopy.

    PubMed

    Zhang, Ming; Geng, Ying; Xiang, Bingren

    2011-01-01

    A simple, rapid and efficient extraction procedure, partitioned dispersive liquid-liquid microextraction, has been developed in combination with near-infrared spectroscopy for the extraction and discrimination of dimethoate from aqueous samples. For this technique, the appropriate mixture of extraction solvent (CCl(4)) and disperser solvent (THF) was utilized. Partial least squares discriminant analysis was applied to build the model with several pre-process methods over the wavenumber regions between 7100 cm(-1) to 7300 cm(-1). The best model gave satisfactory classification accuracy, 98.6% for calibration set (n=74) and 97.6% for prediction set (n=42), using preprocessing of standard normal variate followed by Savitzky-Golay first derivative. The method was successfully applied to bottled water, tap water, lake water and farm water samples. The results demonstrated the possibility of near-infrared spectroscopy after partitioned dispersive liquid-liquid microextraction for the identification of water contaminated by dimethoate. PMID:21628987

  5. Cloud and rain liquid water statistics in the CHUVA campaign

    NASA Astrophysics Data System (ADS)

    Calheiros, Alan J. P.; Machado, Luiz A. T.

    2014-07-01

    The purpose of this study is to present statistics related to the integration of cloud and rain liquid water and the profiles for different cloud types and regimes. From 2010 to 2012, the CHUVA project collected information regarding cloud and rain characteristics in different precipitation regimes in Brazil. CHUVA had four field campaigns between 2010 and 2011, located in the North, Northeast and Southeast regions of Brazil, covering the semi-arid, Amazon, coastal and mountain regions. The synergy of several instruments allowed us to classify rain events and describe the cloud processes regionally. Microwave radiometers, LiDAR, radar, and disdrometers were employed in this study. The rain type classification was made using vertical profiles of reflectivity (VPR) and polarimetric variables from dual polarization radar (XPOL). The integrated liquid water (ILWC) for non-precipitating clouds was retrieved with a microwave ground-based radiometer using a neural network. For rainy conditions, the profiles from the rain liquid water content (LWCR) and their integrated (ILWR) properties were estimated by Micro Rain Radar (MRR) and XPOL VPRs. For non-precipitating clouds, the ILWC values were larger for the sites in tropical regions, in particular near the coast, than for Southeast Brazil. For rainy cases, distinct LWCR profiles were observed for different rain classifications and regions. The differences are small for low rain rates and a distinction between different rainfall regimes is more evident for high rain rates. Vale and Belém clouds present the deepest layers and largest convective rain rates. The clouds in the Southeast region of Brazil (Vale do Paraíba) and North region (Belém) showed the largest reflectivity in the mixed and glaciated layers, respectively. In contrast, the Northeast coastal site (e.g. Fortaleza) showed larger values in the warm part of the clouds. Several analyses are presented, describing the cloud processes and the differences among the cloud types, rain rates and regions.

  6. Spin states of para-water and ortho-water molecule in gas and liquid phases

    E-print Network

    V. K. Konyukhov

    2009-09-23

    Spin degrees of freedom of water molecule in gas and liquid state were investigated in order to provide a reasonable answer about the unsolved problem of a long-term behavior of water spin isomers. The approach used involves an assumption that molecules change their spin state from a pure state to a mixed one when they interact with some sorts of adsorbent surface. Some models and conceptions of the quantum information processing were used.

  7. The structural origin of anomalous properties of liquid water.

    PubMed

    Nilsson, Anders; Pettersson, Lars G M

    2015-01-01

    Water is unique in its number of unusual, often called anomalous, properties. When hot it is a normal simple liquid; however, close to ambient temperatures properties, such as the compressibility, begin to deviate and do so increasingly on further cooling. Clearly, these emerging properties are connected to its ability to form up to four well-defined hydrogen bonds allowing for different local structural arrangements. A wealth of new data from various experiments and simulations has recently become available. When taken together they point to a heterogeneous picture with fluctuations between two classes of local structural environments developing on temperature-dependent length scales. PMID:26643439

  8. The structural origin of anomalous properties of liquid water

    PubMed Central

    Nilsson, Anders; Pettersson, Lars G. M.

    2015-01-01

    Water is unique in its number of unusual, often called anomalous, properties. When hot it is a normal simple liquid; however, close to ambient temperatures properties, such as the compressibility, begin to deviate and do so increasingly on further cooling. Clearly, these emerging properties are connected to its ability to form up to four well-defined hydrogen bonds allowing for different local structural arrangements. A wealth of new data from various experiments and simulations has recently become available. When taken together they point to a heterogeneous picture with fluctuations between two classes of local structural environments developing on temperature-dependent length scales. PMID:26643439

  9. Investigation of a liquid-fed water resistojet plume

    NASA Technical Reports Server (NTRS)

    Manzella, D. H.; Carney, L. M.

    1989-01-01

    Measurements of mass flux and flow angle were taken throughout the forward flow region of the exhaust of a liquid-fed water resistojet using a quartz crystal microbalance (QCM). The resistojet operated at a mass flow rate of 0.1 g/s with a power input of 330 Watts. Measured values were compared to theoretical predictions obtained by employing a source flow approximation. Excellent agreement between predicted and measured mass flux values was attained; however, this agreement was highly dependent on knowledge of nozzle flow conditions. Measurements of the temperature at which the exhaust condensed on the QCM were obtained as a function of incident mass flux.

  10. The Effect of Xuefuzhuyu Oral Liquid on Aspirin Resistance and Its Association with rs5911, rs5787, and rs3842788 Gene Polymorphisms

    PubMed Central

    Xue, Mei; Yang, Lin; Kou, Na; Miao, Yu; Wang, Mingming; Zhao, Quanli; Ren, Junhua; Zhang, Shaoyan; Shi, Dazhuo; Chen, Keji

    2015-01-01

    Aspirin should be continued indefinitely in patients after interventional therapy, but 10% to 40% of patients experience recurrent vascular events despite adequate aspirin therapy, a condition known as aspirin resistance (AR). Xuefuzhuyu oral liquid, derived from the classic recipe Xuefuzhuyu decoction, has been well documented to inhibit platelet aggregation and to improve hemorheology. The aims of this study were to investigate the effects of Xuefuzhuyu oral liquid on AR in patients with chronic stable angina after percutaneous coronary intervention (PCI) and the possible genetic markers related to the drug response. 43 patients diagnosed as having aspirin resistance or semi-resistance were randomly divided into control and treatment groups after screening 207 stable CHD patients. Platelet aggregation rate was determined using turbidimetry. Three single nucleotide polymorphisms in COX-1 (rs5787, rs3842788) and GP IIb (rs5911) were genotyped in whole blood samples using ABI PRISM 7900 HT Fast Real-Time instrument and ABI PRISM 3730 DNA Sequencer. The results showed that Xuefuzhuyu oral liquid could effectively improve blood stasis syndrome and AR by inhibiting ADP-induced platelet aggregation and that patients with the rs5911 genetic variant exhibited better drug response upon treatment with Xuefuzhuyu oral liquid, which suggests Xuefuzhuyu oral liquid as a new possible drug for the prevention of AR. PMID:26495016

  11. Distribution of binding energies of a water molecule in the water liquid-vapor interface

    SciTech Connect

    Chempath, Shaji; Pratt, Lawrence R

    2008-01-01

    Distributions of binding energies of a water molecule in the water liquid-vapor interface are obtained on the basis of molecular simulation with the SPC/E model of water. These binding energies together with the observed interfacial density profile are used to test a minimally conditioned Gaussian quasi-chemical statistical thermodynamic theory. Binding energy distributions for water molecules in that interfacial region clearly exhibit a composite structure. A minimally conditioned Gaussian quasi-chemical model that is accurate for the free energy of bulk liquid water breaks down for water molecules in the liquid-vapor interfacial region. This breakdown is associated with the fact that this minimally conditioned Gaussian model would be inaccurate for the statistical thermodynamics of a dilute gas. Aggressive conditioning greatly improves the performance of that Gaussian quasi-chemical model. The analogy between the Gaussian quasi-chemical model and dielectric models of hydration free energies suggests that naive dielectric models without the conditioning features of quasi-chemical theory will be unreliable for these interfacial problems. Multi-Gaussian models that address the composite nature of the binding energy distributions observed in the interfacial region might provide a mechanism for correcting dielectric models for practical applications.

  12. ETV REPORT AND VERIFICATION STATEMENT; EVALUATION OF LOBO LIQUIDS RINSE WATER RECOVERY SYSTEM

    EPA Science Inventory

    The Lobo Liquids Rinse Water Recovery System (Lobo Liquids system) was tested, under actual production conditions, processing metal finishing wastewater, at Gull Industries in Houston, Texas. The verification test evaluated the ability of the ion exchange (IX) treatment system t...

  13. Innovative Strategy on Hydrogen Evolution Reaction Utilizing Activated Liquid Water

    NASA Astrophysics Data System (ADS)

    Hwang, Bing-Joe; Chen, Hsiao-Chien; Mai, Fu-Der; Tsai, Hui-Yen; Yang, Chih-Ping; Rick, John; Liu, Yu-Chuan

    2015-11-01

    Splitting water for hydrogen production using light, or electrical energy, is the most developed ‘green technique’. For increasing efficiency in hydrogen production, currently, the most exciting and thriving strategies are focused on efficient and inexpensive catalysts. Here, we report an innovative idea for efficient hydrogen evolution reaction (HER) utilizing plasmon-activated liquid water with reduced hydrogen-bonded structure by hot electron transfer. This strategy is effective for all HERs in acidic, basic and neutral systems, photocatalytic system with a g-C3N4 (graphite carbon nitride) electrode, as well as in an inert system with an ITO (indium tin oxide) electrode. Compared to deionized water, the efficiency of HER increases by 48% based on activated water ex situ on a Pt electrode. Increase in energy efficiency from activated water is 18% at a specific current yield of ?20?mA in situ on a nanoscale-granulated Au electrode. Moreover, the onset potential of ?0.023?V vs RHE was very close to the thermodynamic potential of the HER (0?V). The measured current density at the corresponding overpotential for HER in an acidic system was higher than any data previously reported in the literature. This approach establishes a new vista in clean green energy production.

  14. Innovative Strategy on Hydrogen Evolution Reaction Utilizing Activated Liquid Water.

    PubMed

    Hwang, Bing-Joe; Chen, Hsiao-Chien; Mai, Fu-Der; Tsai, Hui-Yen; Yang, Chih-Ping; Rick, John; Liu, Yu-Chuan

    2015-01-01

    Splitting water for hydrogen production using light, or electrical energy, is the most developed 'green technique'. For increasing efficiency in hydrogen production, currently, the most exciting and thriving strategies are focused on efficient and inexpensive catalysts. Here, we report an innovative idea for efficient hydrogen evolution reaction (HER) utilizing plasmon-activated liquid water with reduced hydrogen-bonded structure by hot electron transfer. This strategy is effective for all HERs in acidic, basic and neutral systems, photocatalytic system with a g-C3N4 (graphite carbon nitride) electrode, as well as in an inert system with an ITO (indium tin oxide) electrode. Compared to deionized water, the efficiency of HER increases by 48% based on activated water ex situ on a Pt electrode. Increase in energy efficiency from activated water is 18% at a specific current yield of -20?mA in situ on a nanoscale-granulated Au electrode. Moreover, the onset potential of -0.023?V vs RHE was very close to the thermodynamic potential of the HER (0?V). The measured current density at the corresponding overpotential for HER in an acidic system was higher than any data previously reported in the literature. This approach establishes a new vista in clean green energy production. PMID:26541371

  15. Innovative Strategy on Hydrogen Evolution Reaction Utilizing Activated Liquid Water

    PubMed Central

    Hwang, Bing-Joe; Chen, Hsiao-Chien; Mai, Fu-Der; Tsai, Hui-Yen; Yang, Chih-Ping; Rick, John; Liu, Yu-Chuan

    2015-01-01

    Splitting water for hydrogen production using light, or electrical energy, is the most developed ‘green technique’. For increasing efficiency in hydrogen production, currently, the most exciting and thriving strategies are focused on efficient and inexpensive catalysts. Here, we report an innovative idea for efficient hydrogen evolution reaction (HER) utilizing plasmon-activated liquid water with reduced hydrogen-bonded structure by hot electron transfer. This strategy is effective for all HERs in acidic, basic and neutral systems, photocatalytic system with a g-C3N4 (graphite carbon nitride) electrode, as well as in an inert system with an ITO (indium tin oxide) electrode. Compared to deionized water, the efficiency of HER increases by 48% based on activated water ex situ on a Pt electrode. Increase in energy efficiency from activated water is 18% at a specific current yield of ?20?mA in situ on a nanoscale-granulated Au electrode. Moreover, the onset potential of ?0.023?V vs RHE was very close to the thermodynamic potential of the HER (0?V). The measured current density at the corresponding overpotential for HER in an acidic system was higher than any data previously reported in the literature. This approach establishes a new vista in clean green energy production. PMID:26541371

  16. Gas and liquid measurements in air-water bubbly flows

    SciTech Connect

    Zhou, X.; Doup, B.; Sun, X.

    2012-07-01

    Local measurements of gas- and liquid-phase flow parameters are conducted in an air-water two-phase flow loop. The test section is a vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. The measurements are performed at z/D = 10. The gas-phase measurements are performed using a four-sensor conductivity probe. The data taken from this probe are processed using a signal processing program to yield radial profiles of the void fraction, bubble velocity, and interfacial area concentration. The velocity measurements of the liquid-phase are performed using a state-of-the-art Particle Image Velocimetry (PIV) system. The raw PIV images are acquired using fluorescent particles and an optical filtration device. Image processing is used to remove noise in the raw PIV images. The statistical cross correlation is introduced to determine the axial velocity field and turbulence intensity of the liquid-phase. Measurements are currently being performed at z/D = 32 to provide a more complete data set. These data can be used for computational fluid dynamic model development and validation. (authors)

  17. Photochemical Water Oxidation by Crystalline Polymorphs of Manganese Oxides: Structural Requirements for Catalysis

    E-print Network

    Garfunkel, Eric

    on the five known structural polymorphs of MnO2. We have adapted literature synthesis methods to obtain pure dye photo-oxidant system. No Ru was absorbed on the catalyst surface as observed by XPS and EDX was found exclusively for (distorted) cubic phases, Mn2O3 (bixbyite), Mn3O4 (hausmannite), and -MnO2 (spinel

  18. LIQUID AND GAS CHROMATOGRAPHIC ANALYSIS OF DIETHYL PHTHALATE IN WATER AND SEDIMENT

    EPA Science Inventory

    Diethyl phthalate was determined in water and sediment by high performance liquid chromatography (HPLC) and in water by gas-liquid chromatography with electron capture detection (GLC-ECD). Water samples were extracted with hexane, using a high-speed homogenizer-ultrasonic apparat...

  19. Regime based investigation of the second aerosol indirect effect for liquid water clouds using satellite data

    NASA Astrophysics Data System (ADS)

    Unglaub, Claudia; Quaas, Johannes

    2015-04-01

    Anthropogenic aerosols may affect cloud micro physical processes and subsequently cloud liquid water path via the so-called "second aerosol indirect effects". To obtain a better quantification of such effects the variability of the liquid water path is investigated to study the sensitivity of liquid water clouds to perturbations in the cloud droplet number concentration. For the statistical analysis the A-Train satellite constellation CCCM data product is used. We will analyze the ISCCP cloud class based correlation between the satellite-derived liquid water path and cloud droplet number concentration for liquid water clouds. Furthermore a possible new cloud classification for the high resolution CCCM data set will be presented. The goal of these studies is a better understanding and the assessment of the radiative forcing by the second aerosol indirect effects on liquid water clouds.

  20. Bond orientational ordering in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization

    E-print Network

    Hajime Tanaka

    2013-07-02

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases the complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is most poorly understood. We argue that it is crucial for a better understanding of liquid to recognize that a liquid generally has a tendency to have local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing low local free-energy configuration, which is bond orientational order parameter in many cases, in addition to density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena are also discussed.

  1. Temporal changes in endmember abundances, liquid water and water vapor over vegetation at Jasper Ridge

    NASA Technical Reports Server (NTRS)

    Roberts, Dar A.; Green, Robert O.; Sabol, Donald E.; Adams, John B.

    1993-01-01

    Imaging spectrometry offers a new way of deriving ecological information about vegetation communities from remote sensing. Applications include derivation of canopy chemistry, measurement of column atmospheric water vapor and liquid water, improved detectability of materials, more accurate estimation of green vegetation cover and discrimination of spectrally distinct green leaf, non-photosynthetic vegetation (NPV: litter, wood, bark, etc.) and shade spectra associated with different vegetation communities. Much of our emphasis has been on interpreting Airborne Visible/Infrared Imaging Spectrometry (AVIRIS) data spectral mixtures. Two approaches have been used, simple models, where the data are treated as a mixture of 3 to 4 laboratory/field measured spectra, known as reference endmembers (EM's), applied uniformly to the whole image, to more complex models where both the number of EM's and the types of EM's vary on a per-pixel basis. Where simple models are applied, materials, such as NPV, which are spectrally similar to soils, can be discriminated on the basis of residual spectra. One key aspect is that the data are calibrated to reflectance and modeled as mixtures of reference EM's, permitting temporal comparison of EM fractions, independent of scene location or data type. In previous studies the calibration was performed using a modified-empirical line calibration, assuming a uniform atmosphere across the scene. In this study, a Modtran-based calibration approach was used to map liquid water and atmospheric water vapor and retrieve surface reflectance from three AVIRIS scenes acquired in 1992 over the Jasper Ridge Biological Preserve. The data were acquired on June 2nd, September 4th and October 6th. Reflectance images were analyzed as spectral mixtures of reference EM's using a simple 4 EM model. Atmospheric water vapor derived from Modtran was compared to elevation, and community type. Liquid water was compare to the abundance of NPV, Shade and Green Vegetation (VG) for select sites to determine whether a relationship existed, and under what conditions the relationship broke down. Temporal trends in endmember fractions, liquid water and atmospheric water vapor were investigated also. The combination of spectral mixture analysis and the Modtran based atmospheric/liquid water models was used to develop a unique vegetation community description.

  2. Determination of phthalate esters in water samples by ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography.

    PubMed

    Zhang, Hui; Chen, Xiaoqing; Jiang, Xinyu

    2011-03-01

    A novel method, termed ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction (IL-CIA-DLLME), combined with high-performance liquid chromatography (HPLC) was developed for the determination of three phthalate esters in water samples. Several important parameters influencing the IL-CIA-DLLME extraction efficiency, such as the type of extraction and disperser solvent, the volume of extraction and disperser solvent, temperature, extraction time and salt effect, were investigated. Under optimal extraction conditions, the enrichment factors and extraction recoveries ranged from 174 to 212 and 69.9 to 84.8%, respectively. Excellent linearity with coefficients of correlation from 0.9968 to 0.9994 was observed in the concentration range of 2-100 ng mL(-1). The repeatability of the proposed method expressed as relative standard deviations ranged from 2.2 to 3.7% (n=5). Limits of detection were between 0.68 and 1.36 ng mL(-1). Good relative recoveries for phthalate esters in tap, bottled mineral and river water samples were obtained in the ranges of 91.5-98.1%, 92.4-99.2% and 90.1-96.8%, respectively. Thus, the proposed method has excellent potential for the determination of phthalate esters in the environmental field. PMID:21338769

  3. Simulated liquid water and visibility in stratiform boundary-layer clouds over sloping terrain

    SciTech Connect

    Tjernstroem, M. )

    1993-04-01

    The amount of liquid water in stratus clouds or fog is discussed from the point of view of estimating visibility variations in areas with complex terrain. The average vertical profile of liquid water from numerical simulations with a higher-order closure mesoscale model is examined, and runs with the model for moderately complex terrain are utilized to estimate the of low-level liquid water content variability and thus, indirectly, the variations in horizontal visibility along a slope. 37 refs., 11 figs.

  4. Influence of liquid water and water vapor on antimisting kerosene (AMK)

    NASA Technical Reports Server (NTRS)

    Yavrouian, A. H.; Sarolouki, M.; Sarohia, V.

    1983-01-01

    Experiments have been performed to evaluate the compatibility of liquid water and water vapor with antimisting kerosenes (AMK) containing polymer additive FM-9 developed by Imperial Chemical Industries. This effort consists of the determination of water solubility in AMK, influence of water on restoration (degradation) of AMK, and effect of water on standard AMK quality control methods. The principal conclusions of this investigation are: (1) the uptake of water in AMK critically depends upon the degree of agitation and can be as high as 1300 ppm at 20 C, (2) more than 250 to 300 ppm of water in AMK causes an insoluble second phase to form. The amount of this second phase depends on fuel temperature, agitation, degree of restoration (degradation) and the water content of the fuel, (3) laboratory scale experiments indicate precipitate formation when water vapor comes in contact with cold fuel surfaces at a much lower level of water (125 to 150 ppm), (4) precipitate formation is very pronounced in these experiments where humid air is percolated through a cold fuel (-20 C), (5) laboratory tests further indicate that water droplet settling time is markedly reduced in AMK as compared to jet A, (6) limited low temperature testing down to -30 C under laboratory conditions indicates the formation of stable, transparent gels.

  5. Effects of water in film boiling over liquid-metal melts

    SciTech Connect

    Greene, G.; Finfrock, C.; Burson, S.B.

    1986-01-01

    Speculation concerning the effects of an overlying pool of boiling water on a molten LWR core/concrete interaction varying widely and range from no effect other than a source of steam to complete quenching of the debris. In the effort to quantify the effects, the experimental investigation to be described was initiated. Liquid-liquid boiling experiments have been performed with H/sub 2/O and liquid-metal melts in the 100-series test matrix (runs 121, 126, 127) and the VE test matrix. Some of the pre-explosion unstable film boiling data as well as observations from the explosive series have been previously reported. It was observed that water boiling on liquid-metal melts was unstable with respect to disturbances, and that liquid-liquid contacts were occurring at the boiling interface well into the film boiling superheat regime. The presence of these liquid-liquid contacts in film boiling was substantiated by photographic observations in transparent test sections. Narrow liquid-metal jets were observed to spike upward into the boiling water pool above, smearing out the interface between the two fluids into a mixing zone of water and liquid metal. The thickness of this mixing zone appeared from visual observations to be in the range of 1 to 2 cm. It is not presently clear what physical phenomena were responsible for this behavior; however, liquid-solid contacts as well as liquid-liquid contacts in the film boiling regime will be investigated in a future test series.

  6. Use of Spacecraft Data to Drive Regions on Mars where Liquid Water would be Stable

    NASA Technical Reports Server (NTRS)

    Lobitz, Brad; Wood, Byron L.; Averner, Maurice M.; McKay, Christopher P.; MacElroy, Robert D.

    2001-01-01

    Combining Viking pressure and temperature data with Mars Orbital Laser Altimeter (MOLA) topography data we have computed the fraction of the martian year during which pressure and temperature allow for liquid water to be stable on the martian surface. We find that liquid water would be stable within the Hellas and Argyre basin and over the northern lowlands equatorward of about 40 degrees. The location with the maximum period of stable conditions for liquid water is in the southeastern portion of Utopia Planitia where 34% of the year liquid water would be stable if it was present. Locations of stability appear to correlate with the distribution of valley networks.

  7. Thermodynamic constraint on the cloud liquid water feedback in climate models

    NASA Technical Reports Server (NTRS)

    Betts, Alan K.; HARSHVARDHAN

    1987-01-01

    The cloud liquid water feedback in climate models consists of the increase (decrease) in optical depth of clouds resulting from higher (lower) liquid water contents that might accompany tropospheric warming (cooling). The change in cloud liquid water with temperature is shown to depend on the rate of change of the slope of the moist adiabat with respect to temperature, and it is a strong function of temperature. The value of this rate of change in the tropics is about half that in mid and high latitudes and is much less than the value obtained by assuming that liquid water scales with the saturation mixing ratio.

  8. Detachment of Liquid-Water Droplets from Gas-Diffusion Layers

    SciTech Connect

    Das, Prodip K.; Grippin, Adam; Weber, Adam Z.

    2011-07-01

    A critical issue for optimal water management in proton-exchange-membrane fuel cells at lower temperatures is the removal of liquid water from the cell. This pathway is intimately linked with the phenomena of liquid-water droplet removal from surface of the gas-diffusion layer and into the flow channel. Thus, a good understanding of liquid-water transport and droplet growth and detachment from the gas-diffusion layer is critical. In this study, liquid-water droplet growth and detachment on the gas-diffusion layer surfaces are investigated experimentally to improve the understating of water transport through and removal from gas-diffusion layers. An experiment using a sliding-angle measurement is designed and used to quantify and directly measure the adhesion force for liquid-water droplets, and to understand the droplets? growth and detachment from the gas-diffusion layers.

  9. The oxygen isotope partition function ratio of water and the structure of liquid water

    USGS Publications Warehouse

    O'Neil, J.R.; Adami, L.H.

    1969-01-01

    By means of the CO2-equilibration technique, the temperature dependence and absolute values of the oxygen isotope partition function ratio of liquid water have been determined, often at 1?? intervals, from -2 to 85??. A linear relationship between In (Q2/Q1) (H2O) and T-1 was obtained that is explicable in terms of the Bigeleisen-Mayer theory of isotopic fractionation. The data are incompatible with conventional, multicomponent mixture models of water because liquid water behaves isotopically as a singly structured homogeneous substance over the entire temperature range studied. A two-species model of water is proposed in which approximately 30% of the hydrogen bonds in ice are broken on melting at 0?? and in which this per cent of monomer changes by only a small amount over the entire liquid range. Because of the high precision and the fundamental property determined, the isotopic fractionation technique is particularly well suited to the detection of thermal anomalies. No anomalies were observed and those previously reported are ascribed to under-estimates of experimental error.

  10. Monte Carlo simulation of electron dynamics in liquid water

    NASA Astrophysics Data System (ADS)

    Huthmacher, Klaus; Herzwurm, André; Gnewuch, Michael; Ritter, Klaus; Rethfeld, Baerbel

    2015-07-01

    We present a stochastic model for the energy loss of low-energy electrons (<100 eV) in water in the liquid phase. More precisely, we treat the electrons as independent particles and are thus able to model the time evolution of the kinetic energy of a single electron as a so-called pure jump process. Free electrons are created due to irradiation of an extreme ultraviolet femtosecond laser pulse. In our model, free electrons may interact with water molecules via elastic scattering and impact ionization. Moreover, we present numerical results for the kinetic energy of electrons during and after laser irradiation. Furthermore, we distinguish between primary and secondary electrons, where the latter are created by impact ionization. The numerical results show that creation of secondary electrons due to impact ionization occurs almost entirely during laser irradiation. After irradiation, only a small amount of the laser pulse energy remains in the electron system, while the majority is stored in holes of water molecules.

  11. Onset of simple liquid behaviour in modified water models

    SciTech Connect

    Prasad, Saurav; Chakravarty, Charusita

    2014-04-28

    The transition to simple liquid behaviour is studied in a set of modified hybrid water models where the potential energy contribution of the Lennard-Jones dispersion-repulsion contribution is progressively enhanced relative to the electrostatic contribution. Characteristics of simple liquid behaviour that indicate the extent to which a given system can be mapped onto an inverse power law fluid are examined, including configurational energy-virial correlations, functional form of temperature dependence of the excess entropy along isochores, and thermodynamic and excess entropy scaling of diffusivities. As the Lennard-Jones contribution to the potential energy function increases, the strength of the configurational energy-virial correlations increases. The Rosenfeld-Tarazona temperature dependence of the excess entropy is found to hold for the range of state points studied here for all the hybrid models, regardless of the degree of correlating character. Thermodynamic scaling is found to hold for weakly polar fluids with a moderate degree of energy-virial correlations. Rosenfeld-scaling of transport properties is found not to be necessarily linked with the strength of energy-virial correlations but may hold for systems with poor thermodynamic scaling if diffusivities and excess entropies show correlated departures from the isomorph-invariant behaviour characteristic of approximate inverse power law fluids. The state-point dependence of the configurational energy-virial correlation coefficient and the implications for thermodynamic and excess entropy scalings are considered.

  12. Influence of gravity on the collective molecular dynamics of liquid water: the case of the floating water bridge

    E-print Network

    Emilio Del Giudice; Giuseppe Vitiello

    2010-09-29

    Quantum electrodynamics (QED) produces a picture of liquid water as a mixture of a low density coherent phase and an high density non-coherent phase. Consequently, the Archimedes principle prescribes that, within a gravitational field, liquid water should be made up, at surface, mainly of the coherent fraction, which becomes a cage where the gas-like non-coherent fraction is trapped, acquiring a non-vanishing pressure (vapor tension). Therefore, it is possible to probe the QED picture by observing the behavior of liquid water under reduced gravity conditions. The floating water bridge could be a useful test model.

  13. A single-bond approach to orientation-dependent interactions and its implications for liquid water

    E-print Network

    favorable and thus increase appreciably in size as the liquid is cooled towards its freezing point. This has. If the liquid is cooled below its freezing point without crystallization super- cooled , many of its physical prA single-bond approach to orientation-dependent interactions and its implications for liquid water

  14. Liquid-vapor interface, cavitation, and the phase diagram of water Frdric Caupin

    E-print Network

    Caupin, Frédéric

    near a SL. It was later understood 2 that a liquid-gas SL was unlikely to exist at positive pressure point. The SL can, however, end at negative pressure by meeting a liquid-solid spinodal see Ref. 2Liquid-vapor interface, cavitation, and the phase diagram of water Frédéric Caupin Laboratoire de

  15. Spectral Density of Cloud Liquid Water Content at High Frequencies.

    NASA Astrophysics Data System (ADS)

    Gerber, H.; Jensen, J. B.; Davis, A. B.; Marshak, A.; Wiscombe, W. J.

    2001-03-01

    Aircraft measurements of liquid water content (LWC) made at sampling frequencies of 1 and 2 kHz with a particle volume monitor (PVM) probe from horizontal traverses in stratocumulus clouds during the Southern Ocean Cloud Experiment and cumulus clouds during the Small Cumulus Microphysics Study are described. The spectral density of the LWC measurements is calculated and compared to the 5/3 scaling law. The effect of PVM sampling noise is found to be small in most cases. Most measurements follow approximately the 5/3 law until cloud scales decrease below about 5 m in length. Below this length LWC variance can exceed that predicted by the 5/3 law. It is suggested that the enhanced LWC variance at small scales is related to entrainment of environmental air into the clouds, which changes primarily the droplet concentration.

  16. Electrokinetic Hydrogen Generation from Liquid WaterMicrojets

    SciTech Connect

    Duffin, Andrew M.; Saykally, Richard J.

    2007-05-31

    We describe a method for generating molecular hydrogen directly from the charge separation effected via rapid flow of liquid water through a metal orifice, wherein the input energy is the hydrostatic pressure times the volume flow rate. Both electrokinetic currents and hydrogen production rates are shown to follow simple equations derived from the overlap of the fluid velocity gradient and the anisotropic charge distribution resulting from selective adsorption of hydroxide ions to the nozzle surface. Pressure-driven fluid flow shears away the charge balancing hydronium ions from the diffuse double layer and carries them out of the aperture. Downstream neutralization of the excess protons at a grounded target electrode produces gaseous hydrogen molecules. The hydrogen production efficiency is currently very low (ca. 10-6) for a single cylindrical jet, but can be improved with design changes.

  17. Conversion of lignocellulosics pretreated with liquid hot water to ethanol

    SciTech Connect

    Walsum, G.P. van; Laser, M.S.; Lynd, L.R.

    1996-12-31

    Lignocellulosic materials pretreated using liquid hot water (LHW) (220{degrees}C, 5 MPa, 120 s) were fermented to ethanol by batch simultaneous saccharification and fermentation (SSF) using Saccharomyces cerevisiae in the presence of Trichoderma reesei cellulose. SSF of sugarcane bagasse (as received), aspen chips (smallest dimension 3 mm), and mixed hardwood flour (-60 +70 mesh) resulted in 90% conversion to ethanol in 2-5 d at enzyme loadings of 15-30 FPU/g. In most cases, 90% of the final conversion was achieved within 75 h of inoculation. Comminution of the pretreated substrates did not affect the conversion to ethanol. The hydrolysate produced from the LHW pretreatment showed slight inhibition of batch growth of S. cerevisiae. Solids pretreated at a concentration of 100 g/L were as reactive as those pretreated at a lower concentration, provided that the temperature was maintained at 220{degrees}C. 51 refs., 3 figs., 4 tabs.

  18. Liquid water in snowing clouds: Implications for satellite remote sensing of snowfall

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Liu, Guosheng; Seo, Eun-Kyoung; Fu, Yunfei

    2013-09-01

    To study the impact of cloud liquid water on passive microwave snowfall remote sensing, we analyzed 4 years of liquid water path data retrieved from microwave radiometer on Aqua satellite that are collocated with CloudSat snowfall observations. Results showed that cloud liquid water commonly occurs in snowing clouds (2-m air temperature lower than 2 °C); about 72% of these clouds have a retrieved liquid water path greater than 0. The mean liquid water path for all snowing clouds is about 74 g m- 2, higher for horizontally extended clouds (70-100 g m- 2) and lower for isolated (~ 50 g m- 2). There is a clear tendency that snowing clouds are less likely to contain liquid water as 2-m air temperature decreases. However, the variation of the mode values of liquid water path with 2-m air temperature seems to be cloud type dependent, particularly for colder environment with 2-m air temperature lower than 263 K. On average, larger values of liquid water path occur when near-surface radar reflectivity ranges from - 10 to 0 dBZ, corresponding to relatively weak snowfall of 0.02 to 0.15 mm h- 1, rather than to the heaviest snowfall observed. The impact of cloud liquid water on passive microwave satellite remote sensing of snowfall has been investigated using radiative transfer simulations. It is concluded that for frequencies higher than 80 GHz the brightness temperature warming caused by cloud liquid water emission has a similar magnitude to the brightness temperature cooling caused by snowflakes' scattering. Therefore, while ice scattering is the primary signature for retrieving snowfall, it is equally important to take into account the impact by cloud liquid water when developing snowfall retrieval algorithms using high-frequency satellite observations.

  19. Thermodynamic Analysis of the Two-Liquid Model for Anomalies of Water, HDL-LDL Fluctuations, and Liquid-Liquid Transition.

    PubMed

    Johari, G P; Teixeira, J

    2015-11-01

    After reviewing the protocol-dependent properties of HDA, which thermally anneals to LDA, and the data gap over an unusually large T-range between HDA, LDA, and water, we investigate whether or not, despite HDA's ill-defined state and distinction from a glass, the HDL-LDL fluctuations view of the two-liquid model can explain water's anomalous behavior. An analysis of the density, ?, compressibility, ?, heat capacity, Cp, and thermal conductivity, ?, of water over a monotonic (continuous) path bridging this data gap shows the following: (i) Such a path between ?water at 320 K and ?HDA yields an untenable thermal expansion coefficient of water. (ii) There is neither a continuous path between ?water at 353 K and ?HDA, nor between Cp,water at 363 K and Cp,HDA. (iii) The same value of ?water, of ?water, or of Cp,water at two temperatures separated by a maxima or a minima is incompatible with the HDL-LDL fluctuations view. (iv) ?LDA at ?140 K is about twice that of ? water at 253 K. (v) ?HDA at 120 K is incompatible with ?water at T > 320 K. Thus, there is an internal inconsistency between the thermodynamics of HDA seen as a glass and that of water seen as an HDL-LDL mixture, which is incompatible with both the HDL-LDL fluctuations view and the liquid-liquid transition. PMID:26436324

  20. Expected magnitude of the aerosol shortwave indirect effect in springtime Arctic liquid water clouds

    E-print Network

    Expected magnitude of the aerosol shortwave indirect effect in springtime Arctic liquid water the expected magnitude of the diurnally-averaged shortwave aerosol first indirect effect in Arctic liquid water surface cooling by the first indirect effect is comparable in magnitude to the longwave surface heating

  1. A Fixed Point Charge Model for Water Optimized to the Vapor-Liquid Coexistence Properties

    E-print Network

    A Fixed Point Charge Model for Water Optimized to the Vapor-Liquid Coexistence Properties Jeffrey R@ipst.umd.edu #12;1 Abstract A new fixed-point charge potential model for water has been developed, targeting the accurate prediction of the vapor-liquid coexistence properties over a broad temperature range. The model

  2. Evidence for liquid water during the high-density to low-density amorphous ice transition

    E-print Network

    Gruner, Sol M.

    distinct forms of supercooled water: high-density liquid (HDL) and low-density liquid (LDL) water (8). In the singularity-free hypothesis, HDL transforms continuously to LDL. In the LL critical point theory, HDL undergoes a first-order phase transition to LDL (8). However, experimental study of the HDL­LDL phase

  3. ASSESSMENT OF THE LIQUID WATER CONTENT OF SUMMERTIME AEROSOL IN THE SOUTHEAST UNITED STATES

    EPA Science Inventory

    The concentration of aerosol liquid water mass represents an important parameter for understanding the physical properties of PM2.5 in the atmosphere. Increases in ambient relative humidity can increase aerosol liquid water and thus the composite particle mass and particle volu...

  4. Network analysis of proton transfer in liquid water

    SciTech Connect

    Shevchuk, Roman; Rao, Francesco; Agmon, Noam

    2014-06-28

    Proton transfer in macromolecular systems is a fascinating yet elusive process. In the last ten years, molecular simulations have shown to be a useful tool to unveil the atomistic mechanism. Notwithstanding, the large number of degrees of freedom involved make the accurate description of the process very hard even for the case of proton diffusion in bulk water. Here, multi-state empirical valence bond molecular dynamics simulations in conjunction with complex network analysis are applied to study proton transfer in liquid water. Making use of a transition network formalism, this approach takes into account the time evolution of several coordinates simultaneously. Our results provide evidence for a strong dependence of proton transfer on the length of the hydrogen bond solvating the Zundel complex, with proton transfer enhancement as shorter bonds are formed at the acceptor site. We identify six major states (nodes) on the network leading from the “special pair” to a more symmetric Zundel complex required for transferring the proton. Moreover, the second solvation shell specifically rearranges to promote the transfer, reiterating the idea that solvation beyond the first shell of the Zundel complex plays a crucial role in the process.

  5. Direct determination of chlorophenols in water samples through ultrasound-assisted hollow fiber liquid-liquid-liquid microextraction on-line coupled with high-performance liquid chromatography.

    PubMed

    Chao, Yu-Ying; Tu, Yi-Ming; Jian, Zhi-Xuan; Wang, Hsaio-Wen; Huang, Yeou-Lih

    2013-01-01

    In this study we on-line coupled hollow fiber liquid-liquid-liquid microextraction (HF-LLLME), assisted by an ultrasonic probe, with high-performance liquid chromatography (HPLC). In this approach, the target analytes - 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 2,6-dichlorophenol (2,6-DCP), and 3,4-dichlorophenol (3,4-DCP) - were extracted into a hollow fiber (HF) supported liquid membrane (SLM) and then back-extracted into the acceptor solution in the lumen of the HF. Next, the acceptor solution was withdrawn on-line into the HPLC sample loop connected to the HF and then injected directly into the HPLC system for analysis. We found that the chlorophenols (CPs) could diffuse quickly through two sequential extraction interfaces - the donor phase - SLM and the SLM - acceptor phase - under the assistance of an ultrasonic probe. Ultrasonication provided effective mixing of the extracted boundary layers with the bulk of the sample and it increased the driving forces for mass transfer, thereby enhancing the extraction kinetics and leading to rapid enrichment of the target analytes. We studied the effects of various parameters on the extraction efficiency, viz. the nature of the SLM and acceptor phase, the compositions of the donor and acceptor phases, the fiber length, the stirring rate, the ion strength, the sample temperature, the sonication conditions, and the perfusion flow rate. This on-line extraction method exhibited linearity (r(2)?0.998), sensitivity (limits of detection: 0.03-0.05 ?g L(-1)), and precision (RSD%?4.8), allowing the sensitive, simple, and rapid determination of CPs in aqueous solutions and water samples with a sampling time of just 2 min. PMID:23237709

  6. Model for the structure of the liquid water network

    SciTech Connect

    Grunwald, E.

    1986-09-17

    The state of a water molecule in liquid water is defined by its time-average network environment. Two states are characterized. State A is the familiar four-coordinated state of the Bernal-Fowler model with tetrahedral hydrogen bonds. State B is five-coordinated. Reexamination of the static dielectric constant by the method of Oster and Kirkwood confirms the marked polar character of the four-coordinated state but shows that the five-coordinated state is only about half as polar. Explicit five-coordinated models are proposed which are consistent with polarity and satisfy constraints of symmetry and hydrogen-bond stoichiometry. The potential energy due to the dipole-dipole interaction of the central water molecule with its time-average solvent network is derived without additional parameters. This permits prediction of barriers to rotation, frequencies for hindered rotation and liberation in the network, and ..delta..H/sub A,B/ and ..delta..S/sub A,B/. The results are in substantial agreement with relevant experiments. In particular, the barriers to rotation permit a consistent interpretation of the dielectric relaxation spectrum. The relative importance of the two states varies predictably with the property being examined, and this can account for some of the schizophrenia of aqueous properties. Since the two-state model is based on time-average network configurations, it does not apply when the time scale of observation is short compared to network frequencies, i.e., at infrared frequencies where continuum models may be successful.

  7. Evidence for Recent Liquid Water on Mars: Gullies

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Gully landforms proposed to have been caused by geologically-recent seepage and runoff of liquid water on Mars are found in the most unlikely places. They typically occur in areas that are quite cold, well below freezing all year round. Like the old adage about moss on trees, nearly all of them form on slopes that face away from sunlight. Most of the gullies occur at latitudes between 30 and 70. The highest latitude at which martian gullies have been found is around 70-75 S on the walls of pits developed in the south polar pitted plains. If you were at this same latitude on Earth, you would be in Antarctica. This region spends much of the winter--which lasts approximately 6 months on Mars--in darkness and at temperatures cold enough to freeze carbon dioxide (around -130C or -200F). Nevertheless, gullies with very sharp, deep, v-shaped channels are seen on the pit walls. Based upon the locations of the tops of the channels on the slope shown here, the inferred site of liquid seepage is located at a layer in the pit wall about 1/3 of the way down from the top of the MOC image. The channels start wide and taper downslope. The area above the channels is layered and has been eroded by mass movement dry avalanching of debris--to form a pattern of chutes and ridges on the upper slope of the pit wall. The top layer appears to have many boulders in it (each about the size of a small house), these boulders are left behind on the upper slopes of the pit wall as debris is removed.

  8. Hybrid liquid metal-water cooling system for heat dissipation of high power density microdevices

    NASA Astrophysics Data System (ADS)

    Deng, Yueguang; Liu, Jing

    2010-12-01

    The recent decades have witnessed a remarkable advancement of very large scale integrated circuits (VLSI) and electronic equipments in micro-electronic industry. Meanwhile, the ever increasing power density of microdevices leads to the tough issue that thermal management becomes rather hard to solve. Conventional water cooling is widely used, but the convective coefficient is not high enough. Liquid metal owns much higher convective coefficient and has been identified as an effective coolant recently, but the high cost greatly precludes its large scale utilization. In this paper, a hybrid liquid metal-water cooling system which combines the advantages of both water and liquid metal cooling was proposed and demonstrated. By utilizing a liquid metal "heat spreader" in front of the water cooling module, this system not only owns more excellent cooling capability than that based on water alone, but also has much lower initial cost compared with absolute liquid metal cooling system. A series of experiments under different operation conditions have been performed to evaluate the cooling performance of this hybrid system. The compared results with absolute water cooling and liquid metal cooling system showed that the cooling capability of the new system is competitive with absolute liquid metal cooling, but the initial cost could be much lower. The theoretical thermal resistance model and economic feasibility also have been analyzed and discussed, which shows that the hybrid liquid metal-water cooling system is quite feasible and useful.

  9. Effects of water in film boiling over liquid metal melts

    SciTech Connect

    Greene, G.A.; Finfrock, C.; Burson, S.B.

    1986-01-01

    Liquid-liquid boiling experiments have been performed with H/sub 2/O and liquid metal melts in the 100-series test matrix (Runs 121, 126, 127) and the VE test matrix. Some of the pre-explosion unstable film boiling data as well as observations from the explosive series have been previously reported.

  10. Elucidating through-plane liquid water profile in a polymer electrolyte membrane fuel cell.

    SciTech Connect

    Wang, Yun; Chen, Ken Shuang

    2010-10-01

    In this paper, a numerical model incorporating micro-porous layers (MPLs) is presented for simulating water transport within the gas diffusion layers (GDLs) and MPLs as well as across their interfaces in a polymer electrolyte membrane (PEM) fuel cell. One-dimensional analysis is conducted to investigate the impacts of MPL and GDL properties on the liquid-water profile across the anode GDL-MPL and cathode MPL-GDL regions. Furthermore, two-dimensional numerical simulations that take MPLs into account are also carried out to elucidate liquid water transport, particularly through-plane liquid-water profile in a PEM fuel cell. Results from case studies are presented.

  11. Pressurized oceans and the eruption of liquid water on Europa and Enceladus

    E-print Network

    Manga, Michael

    expansion of water as it freezes from the top increases pressure in the water confined below the ice. We and Pressurization of Water: A Demonstration [6] In order to show that freezing from the surface-down will increase is very small. In order to freeze water at the surface, liquid nitrogen is poured into a plastic cup

  12. REVIEW ARTICLE: The high-frequency dynamics of liquid water

    NASA Astrophysics Data System (ADS)

    Ruocco, Giancarlo; Sette, Francesco

    1999-06-01

    This article is dedicated to reviewing the recent inelastic x-ray scattering (IXS) work on the high-frequency collective dynamics in liquid water. The results obtained with the IXS technique are directly compared with existing ones from inelastic neutron scattering (INS) and molecular dynamics simulation investigations that were carried out with the aim of achieving an understanding of the collective properties of water at the microscopic level. The IXS work has made it possible to demonstrate experimentally the existence, in the range of exchange momentum (Q) examined (1-10 nm-1), of two branches of collective modes: one linearly dispersing with Q (with the apparent sound velocity of icons/Journals/Common/approx" ALT="approx" ALIGN="TOP"/>3200 m s-1) and the other at almost constant energy (5-7 meV). It has been possible to show that the dispersing branch originates from an upwards bend of the ordinary sound branch observed in low-frequency measurements. The study of this sound velocity dispersion, marking a transition from the ordinary sound, co, to the `fast' sound, cicons/Journals/Common/infty" ALT="infty" ALIGN="MIDDLE"/>, as a function of temperature, has made it possible to relate the origin of this phenomenon to a structural relaxation process, which presents many analogies with those observed for glass-forming systems. The possibility of estimating from the IXS data the value of the relaxation time, icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, as a function of temperature leads to a relating of the relaxation process to the structural rearrangements induced by the making and breaking of hydrogen bonds. In this framework, it is then possible to recognize a hydrodynamical `normal' regime, i.e. one for which the density fluctuations have a period of oscillation that is on a timescale that is long with respect to icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, and a solid-like regime in the opposite limit. In the latter regime, the density fluctuations `feel' the liquid as frozen and the sound velocity is much higher: this is `fast' sound, whose velocity is equivalent to the sound velocity found in crystalline ice Ih.

  13. Liquid-liquid phase transition model incorporating evidence for ferroelectric state near the lambda-point anomaly in supercooled water

    E-print Network

    Peter O. Fedichev; Leonid I. Menshikov

    2012-01-30

    We propose a unified model combining the first-order liquid-liquid and the second-order ferroelectric phase transitions models and explaining various features of the $\\lambda$-point of liquid water within a single theoretical framework. It becomes clear within the proposed model that not only does the long-range dipole-dipole interaction of water molecules yield a large value of dielectric constant $\\epsilon$ at room temperatures, our analysis shows that the large dipole moment of the water molecules also leads to a ferroelectric phase transition at a temperature close to the lambda-point. Our more refined model suggests that the phase transition occurs only in the low density component of the liquid and is the origin of the singularity of the dielectric constant recently observed in experiments with supercooled liquid water at temperature T~233K. This combined model agrees well with nearly every available set of experiments and explains most of the well-known and even recently obtained results of MD simulations.

  14. Dissociative ionization of liquid water induced by vibrational overtone excitation

    SciTech Connect

    Natzle, W.C.

    1983-03-01

    Photochemistry of vibrationally activated ground electronic state liquid water to produce H/sup +/ and OH/sup -/ ions has been initiated by pulsed, single-photon excitation of overtone and combination transitions. Transient conductivity measurements were used to determine quantum yields as a function of photon energy, isotopic composition, and temperature. The equilibrium relaxation rate following perturbation by the vibrationally activated reaction was also measured as a function of temperature reaction and isotopic composition. In H/sub 2/O, the quantum yield at 283 +- 1 K varies from 2 x 10/sup -9/ to 4 x 10/sup -5/ for wave numbers between 7605 and 18140 cm/sup -1/. In D/sub 2/O, the dependence of quantum yield on wavelength has the same qualitative shape as for H/sub 2/O, but is shifted to lower quantum yields. The position of a minimum in the quantum yield versus hydrogen mole fraction curve is consistent with a lower quantum yield for excitation of HOD in D/sub 2/O than for excitation of D/sub 2/O. The ionic recombination distance of 5.8 +- 0.5 A is constant within experimental error with temperature in H/sub 2/O and with isotopic composition at 25 +- 1/sup 0/C.

  15. Microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid for the determination of sulfonamides in environmental water samples.

    PubMed

    Song, Ying; Wu, Lijie; Lu, Chunmei; Li, Na; Hu, Mingzhu; Wang, Ziming

    2014-12-01

    An easy, quick, and green method, microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid, was first developed and applied to the extraction of sulfonamides in environmental water samples. 1-Ethy-3-methylimidazolium hexafluorophosphate, which is a solid-state ionic liquid at room temperature, was used as extraction solvent in the present method. After microwave irradiation for 90 s, the solid-state ionic liquid was melted into liquid phase and used to finish the extraction of the analytes. The ionic liquid and sample matrix can be separated by freezing and centrifuging. Several experimental parameters, including amount of extraction solvent, microwave power and irradiation time, pH of sample solution, and ionic strength, were investigated and optimized. Under the optimum experimental conditions, good linearity was observed in the range of 2.00-400.00 ?g/L with the correlation coefficients ranging from 0.9995 to 0.9999. The limits of detection for sulfathiazole, sulfachlorpyridazine, sulfamethoxazole, and sulfaphenazole were 0.39, 0.33, 0.62, and 0.85 ?g/L, respectively. When the present method was applied to the analysis of environmental water samples, the recoveries of the analytes ranged from 75.09 to 115.78% and relative standard deviations were lower than 11.89%. PMID:25271847

  16. Balancing local order and long-ranged interactions in the molecular theory of liquid water

    NASA Astrophysics Data System (ADS)

    Shah, J. K.; Asthagiri, D.; Pratt, L. R.; Paulaitis, M. E.

    2007-10-01

    A molecular theory of liquid water is identified and studied on the basis of computer simulation of the TIP3P model of liquid water. This theory would be exact for models of liquid water in which the intermolecular interactions vanish outside a finite spatial range, and therefore provides a precise analysis tool for investigating the effects of longer-ranged intermolecular interactions. We show how local order can be introduced through quasichemical theory. Long-ranged interactions are characterized generally by a conditional distribution of binding energies, and this formulation is interpreted as a regularization of the primitive statistical thermodynamic problem. These binding-energy distributions for liquid water are observed to be unimodal. The Gaussian approximation proposed is remarkably successful in predicting the Gibbs free energy and the molar entropy of liquid water, as judged by comparison with numerically exact results. The remaining discrepancies are subtle quantitative problems that do have significant consequences for the thermodynamic properties that distinguish water from many other liquids. The basic subtlety of liquid water is found then in the competition of several effects which must be quantitatively balanced for realistic results.

  17. Nimbus 7 SMMR derived seasonal variations in the water vapor, liquid water, and surface winds over the global oceans

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Short, D. A.

    1984-01-01

    A study based on monthly mean maps of atmospheric water vapor, liquid water, and surface wind derived from Nimbus-7 SMMR over the oceans for 13 months, is examined. A discussion of the retrieval technique used to derive the parameters is presented. The seasonal changes in the strength and position of several of the parameter features are revealed by the December 1978 and June 1979 maps. Zonal averages of the water vapor, liquid water, and surface wind for December and June are compared with information derived from conventional measurements and the results are presented in graphs.

  18. Estimated accuracy of ground-based liquid water measurements during FIRE

    NASA Technical Reports Server (NTRS)

    Snider, Jack B.

    1990-01-01

    Since on goal of the First ISCCP Regional Experiment (FIRE) project is to improve our understanding of the relationships between cloud microphysics and cloud reflectivity, it is important that the accuracy of remote liquid measurements by microwave radiometry be thoroughly understood. The question is particularly relevant since the uncertainty in the absolute value of the radiometric liquid measurement is greatest at low liquid water contents (less than 0.1 mm). However it should be stressed that although uncertainty exists in the absolute value of liquid, it is well known that the observed radiometric signal is proportional to the amount of liquid in the antenna beam. As a result, changes in amounts of liquid are known to greater accuracy than the absolute value, which may contain a bias. Here, an assessment of the liquid measurement accuracy attained at San Nicolas Island (SNI) is presented. The vapor and liquid water data shown were computed from the radiometric brightness temperatures using statistical retrieval algorithms. The retrieval coefficients were derived from the 69 soundings made by Colorado State University during the SNI observations. Sources of error in the vapor and liquid measurements include cross-talk in the retrieval algorithms (not a factor at low liquid contents), uncertainties in the brightness temperature measurement, and uncertainties in the vapor and liquid attenuation coefficients. The relative importance of these errors is discussed. For the retrieval of path-integrated liquid water, the greatest uncertainty is caused by the temperature dependence of the absorption at microwave frequencies. As a result, the accuracy of statistical retrieval of liquid depends to large measure upon how representative the a priori radiosonde data are of the conditions prevailing during the measurements. The microwave radiometer measurements at SNI were supplemented by an infrared (IR) radiometer modified for measurement of cloud-base temperature. Thus, the IR system provides the means to incorporate continuous measurements of the liquid temperature into the retrieval process.

  19. Explaining ionic liquid water solubility in terms of cation and anion hydrophobicity.

    PubMed

    Ranke, Johannes; Othman, Alaa; Fan, Ping; Müller, Anja

    2009-03-01

    The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities. PMID:19399248

  20. Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

    PubMed Central

    Ranke, Johannes; Othman, Alaa; Fan, Ping; Müller, Anja

    2009-01-01

    The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities. PMID:19399248

  1. Small-scale experimental study of vaporization flux of liquid nitrogen released on water.

    PubMed

    Gopalaswami, Nirupama; Olewski, Tomasz; Véchot, Luc N; Mannan, M Sam

    2015-10-30

    A small-scale experimental study was conducted using liquid nitrogen to investigate the convective heat transfer behavior of cryogenic liquids released on water. The experiment was performed by spilling five different amounts of liquid nitrogen at different release rates and initial water temperatures. The vaporization mass fluxes of liquid nitrogen were determined directly from the mass loss measured during the experiment. A variation of initial vaporization fluxes and a subsequent shift in heat transfer mechanism were observed with changes in initial water temperature. The initial vaporization fluxes were directly dependent on the liquid nitrogen spill rate. The heat flux from water to liquid nitrogen determined from experimental data was validated with two theoretical correlations for convective boiling. It was also observed from validation with correlations that liquid nitrogen was found to be predominantly in the film boiling regime. The substantial results provide a suitable procedure for predicting the heat flux from water to cryogenic liquids that is required for source term modeling. PMID:25935406

  2. Water-saving liquid-gas conditioning system

    DOEpatents

    Martin, Christopher; Zhuang, Ye

    2014-01-14

    A method for treating a process gas with a liquid comprises contacting a process gas with a hygroscopic working fluid in order to remove a constituent from the process gas. A system for treating a process gas with a liquid comprises a hygroscopic working fluid comprising a component adapted to absorb or react with a constituent of a process gas, and a liquid-gas contactor for contacting the working fluid and the process gas, wherein the constituent is removed from the process gas within the liquid-gas contactor.

  3. Degassifying and mixing apparatus for liquids. [potable water for spacecraft

    NASA Technical Reports Server (NTRS)

    Yamauchi, S. T. (inventor)

    1983-01-01

    An apparatus for degassing a liquid comprises a containment vessel a liquid pump and a header assembly (12) within the containment vessel in a volume above the reservoir of the liquid. The pump draws from this reservoir and outputs to the header assembly, the latter being constructed to return the liquid to the reservoir in the form of a number of stacked, vertically spaced, concentric, conical cascades via orifices. A vacuum source provides a partial vacuum in the containment vessel to enhance the degassing process.

  4. Rich polymorphism of a rod-like liquid crystal (8CB) confined in two types of unidirectional nanopores

    NASA Astrophysics Data System (ADS)

    Guégan, R.; Morineau, D.; Lefort, R.; Béziel, W.; Guendouz, M.; Noirez, L.; Henschel, A.; Huber, P.

    2008-07-01

    We present a neutron and X-rays scattering study of the phase transitions of 4-n-octyl-4' -cyanobiphenyl (8CB) confined in unidirectional nanopores of porous alumina and porous silicon (PSi) membranes with an average diameter of 30nm. Spatial confinement reveals a rich polymorphism, with at least four different low temperature phases in addition to the smectic A phase. The structural study as a function of thermal treatments and conditions of spatial confinement allows us to get insights into the formation of these phases and their relative stability. It gives the first description of the complete phase behavior of 8CB confined in PSi and provides a direct comparison with results obtained in bulk conditions and in similar geometric conditions of confinement but with reduced quenched disorder effects using alumina anopore membranes.

  5. On the collective network of ionic liquid/water mixtures. IV. Kinetic and rotational depolarization

    NASA Astrophysics Data System (ADS)

    Schröder, Christian; Sega, Marcello; Schmollngruber, Michael; Gailberger, Elias; Braun, Daniel; Steinhauser, Othmar

    2014-05-01

    Dielectric spectroscopy is a measure of the collective Coulomb interaction in liquid systems. Adding ionic liquids to an aqueous solution results in a decrease of the static value of the generalized dielectric constant which cannot be attributed to kinetic depolarization models characterized by the static conductivity and rotational relaxation constant. However, a dipolar Poisson-Boltzmann model computing the water depolarization in the proximity of ions is not only successful for simple electrolytes but also in case of molecular ionic liquids. Moreover, our simple geometric hydration model is also capable to explain the dielectric depolarization. Both models compute the dielectric constant of water and obtain the overall dielectric constant by averaging the values of its components, water and the ionic liquid, weighted by their volume occupancies. In this sense, aqueous ionic liquid mixtures seem to behave like polar mixtures.

  6. Lorentz force in water: evidence that hydronium cyclotron resonance enhances polymorphism.

    PubMed

    D'Emilia, E; Giuliani, L; Lisi, A; Ledda, M; Grimaldi, S; Montagnier, L; Liboff, A R

    2015-12-01

    There is an ongoing question regarding the structure forming capabilities of water at ambient temperatures. To probe for different structures, we studied effects in pure water following magnetic field exposures corresponding to the ion cyclotron resonance of H3O(+). Included were measurements of conductivity and pH. We find that under ion cyclotron resonance (ICR) stimulation, water undergoes a transition to a form that is hydroxonium-like, with the subsequent emission of a transient 48.5?Hz magnetic signal, in the absence of any other measurable field. Our results indicate that hydronium resonance stimulation alters the structure of water, enhancing the concentration of EZ-water. These results are not only consistent with Del Giudice's model of electromagnetically coherent domains, but they can also be interpreted to show that these domains exist in quantized spin states. PMID:25020009

  7. Coating permits use of strain gage in water and liquid hydrogen

    NASA Technical Reports Server (NTRS)

    Berven, B. B.

    1966-01-01

    Strain gage installation covered with a three-layer coating of commercial materials makes measurements in water and liquid hydrogen. It consists of a selected foil strain gage bonded with a modified commercial heat-curring epoxy cement. The outer protective layer of the gage installation may develop cracks when immersed in liquid hydrogen.

  8. Nuclear magnetic resonance in water solutions of inorganic salts in vitreous and liquid states

    SciTech Connect

    Lundin, A. G. Koryavko, N. A.; Chichikov, S. A.

    2013-05-15

    Peculiarities of the behavior of water solutions of inorganic salts at temperatures of {approx}(120-150) K are examined. At these temperatures the solutions are in the vitreous state. At higher temperatures (up to 240 K) the solutions may be in metastable liquid, crystalline, or usual liquid states.

  9. Elucidating the mechanism of selective ion adsorption to the liquid water surface

    E-print Network

    Cohen, Ronald C.

    and solubility, enzyme activity) (16, 17), as embodied in the famous Hofmeister series of relative lyotropic ion solution to the liquid/vapor interface was measured as a function of temperature by resonant UV second of temperature-dependent adsorption free energy for a prototypical inorganic ion at the liquid water surface

  10. Park City/ANS 1 ANALYSIS OF LIQUID CRYOGEN-WATER EXPERIMENTS WITH THE MELCOR CODE

    E-print Network

    California at Los Angeles, University of

    Park City/ANS 1 ANALYSIS OF LIQUID CRYOGEN-WATER EXPERIMENTS WITH THE MELCOR CODE R.C. Duckworth, J are processes involving significant energy exchange between a hot and colder, more volatile liquid structures and cryogenic materials (i.e., helium and nitrogen) required for magnet cooling have

  11. Transient Liquid Water as a Mechanism for Induration of Soil Crusts on Mars

    NASA Astrophysics Data System (ADS)

    Landis, G. A.; Blaney, D.; Cabrol, N.; Clark, B. C.; Farmer, J.; Grotzinger, J.; Greeley, R.; McLennan, S. M.; Richter, L.; Yen, A.; Mer Athena Science Team

    2004-03-01

    We propose two alternative models to account for the origin of cemented Martian soils, or duricrusts, involving the action of transient liquid water films to mediate adhesion and cementation of grains.

  12. Water World's weirdest Liquid wants to be two of them: Does it succeed at negative pressure

    E-print Network

    Angell, C. Austen

    the second liquid phase lies hidden behind a "crystallization curtain" at positive pressures, we will argue by sophisticated techniques. 1 Speedy, R. J. & Angell, C. A. Isothermal Compressibility of Supercooled Water

  13. Excited state dynamics of liquid water: Insight from the dissociation reaction following two-photon excitation

    E-print Network

    Elles, Christopher G.; Shkrob, Ilya A.; Crowell, Robert A.; Bradforth, Stephen E.

    2007-04-25

    The authors use transient absorption spectroscopy to monitor the ionization and dissociation products following two-photon excitation of pure liquid water. The primary decay mechanism changes from dissociation at an excitation energy of 8.3e...

  14. Dielectric signatures of adsorbed and salty liquid water at the Phoenix landing site, Mars

    E-print Network

    Stillman, David E.

    with precipitation by freezing following a prior epoch of high obliquity. The evaporation of diurnal briny meltwater per- chlorates were discovered in the regolith [Hecht et al., 2009]. Liquid saline water droplets

  15. Use of switchable hydrophilicity solvents for the homogeneous liquid-liquid microextraction of triazine herbicides from environmental water samples.

    PubMed

    Lasarte-Aragonés, Guillermo; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

    2015-03-01

    A homogeneous liquid-liquid microextraction alternative, based on the use of switchable hydrophilicity solvents, is presented. The extraction technique makes use of 125 ?L of a water-immiscible solvent (N,N-dimethylcyclohexylamine) that can be solubilized in the aqueous phase in 1:1 ratio using CO2 as a reagent. After the extraction, phase separation is induced by the addition of sodium hydroxide that produces a change on the ionization state of the amine, and centrifugation was not necessary. The extraction technique has been optimized and characterized using the determination of triazine herbicides by gas chromatography with mass spectrometry in water samples. The presence of metallic ions in environmental waters as interferents is easily avoided by the addition of ethylenediaminetetraacetic acid before the microextraction procedure. The proposed method allows the determination of the target analytes at the low microgram per liter range with good precision (relative standard deviation lower than 12.5%). PMID:25641871

  16. Ab initio calculation of the electronic absorption spectrum of liquid water

    NASA Astrophysics Data System (ADS)

    Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa

    2014-04-01

    The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

  17. Ab initio calculation of the electronic absorption spectrum of liquid water

    SciTech Connect

    Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa; Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa; Instituto de Física da Universidade de São Paulo, CP 66318, 05314-970 São Paulo, SP

    2014-04-28

    The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O–H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

  18. Premelted liquid water in frozen soils and its interaction with bio-molecules

    NASA Astrophysics Data System (ADS)

    Hansen-Goos, H.; Wettlaufer, J. S.

    2011-12-01

    While liquid water in bulk is unstable on the surface of Mars, there is a possibility for the persistence of thin films of liquid water in the Martian regolith as a result of interfacial forces between the interstitial ice and the soil grains even below the bulk melting temperature. This is referred to as premelting. We present a calculation of the liquid fraction of frozen soils which takes into account premelting in combination with the effect of ionic impurities and the curvature induced freezing point depression (Gibbs-Thomson effect). We introduce a revised density functional theory which accurately treats a simple model for confined liquid water. We use the theory to study how biological matter (antifreeze proteins in particular) inside a narrow liquid cavity in ice interacts with the surrounding ice-water interface. Because in this case the interface is concave and hence the Gibbs-Thomson effect is antagonistic to the liquid phase, the protein-ice interaction is responsible for the persistence of liquid water.

  19. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water

    PubMed Central

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-01-01

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, . Here we report a universal water-content, , dependence of for aqueous solutions. Solutions with vitrify/devitrify at a constant temperature, , referring to freeze-concentrated phase with left behind ice crystallization. Those solutions with totally vitrify at under conventional cooling/heating process though, of the samples annealed at temperatures?? to effectively evoke ice recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of by annealing is attributable to freeze-concentrated phase of solutions instead of ‘liquid II phase of water’. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution. PMID:26503911

  20. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water

    NASA Astrophysics Data System (ADS)

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-10-01

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, . Here we report a universal water-content, , dependence of for aqueous solutions. Solutions with vitrify/devitrify at a constant temperature, , referring to freeze-concentrated phase with left behind ice crystallization. Those solutions with totally vitrify at under conventional cooling/heating process though, of the samples annealed at temperatures?? to effectively evoke ice recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of by annealing is attributable to freeze-concentrated phase of solutions instead of ‘liquid II phase of water’. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.

  1. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water.

    PubMed

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-01-01

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, . Here we report a universal water-content, , dependence of for aqueous solutions. Solutions with vitrify/devitrify at a constant temperature, , referring to freeze-concentrated phase with left behind ice crystallization. Those solutions with totally vitrify at under conventional cooling/heating process though, of the samples annealed at temperatures?? to effectively evoke ice recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of by annealing is attributable to freeze-concentrated phase of solutions instead of 'liquid II phase of water'. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution. PMID:26503911

  2. Divergent trend in density versus viscosity of ionic liquid/water mixtures: a molecular view from guanidinium ionic liquids.

    PubMed

    Singh, Akhil Pratap; Gardas, Ramesh L; Senapati, Sanjib

    2015-09-23

    Ionic liquids (ILs) have shown great potential in the dissolution and stability of biomolecules when a low-to-moderate quantity of water is added. Hence, determining the thermophysical properties and understanding these novel mixtures at the molecular level are of both fundamental and practical importance. In this context, here we report the synthesis of two nontoxic guanidinium cation based ILs, tetramethylguanidinium benzoate [TMG][BEN] and tetramethylguanidinium salicylate [TMG][SAL], and present a detailed comparison of their thermophysical properties in the presence of water. The results show that the [TMG][SAL]/water mixtures have higher density and higher apparent molar volume, but a lower viscosity and higher compressibility than the [TNG][BEN]/water mixtures. The measured viscosity and compressibility data are explained from ab initio quantum mechanical calculations and liquid-phase molecular dynamics simulations, where salicylate anions of denser [TMG][SAL]/water were found to exist as isolated ions due to intramolecular H-bonding. On the contrary, intermolecular H-bonding among the benzoate anions and their strong tendency to form an extended H-bonding network with water made [TMG][BEN]/water solutions more viscous and less compressible. This study shows the importance of probing these emerging solvents at the molecular-to-atomic level, which could be helpful in their optimal usage for task-specific applications. PMID:26347332

  3. Hydrothermal decomposition of liquid crystal in subcritical water.

    PubMed

    Zhuang, Xuning; He, Wenzhi; Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao

    2014-04-30

    Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4'-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H2O2 supply, pH value 6, temperature 275°C and reaction time 5 min, 97.6% of 4-octoxy-4'-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment. PMID:24632487

  4. Nuclear tanker producing liquid fuels from air and water

    E-print Network

    Galle-Bishop, John Michael

    2011-01-01

    Emerging technologies in CO? air capture, high temperature electrolysis, microchannel catalytic conversion, and Generation IV reactor plant systems have the potential to create a shipboard liquid fuel production system ...

  5. Polymer formulation for removing hydrogen and liquid water from an enclosed space

    DOEpatents

    Shepodd, Timothy J. (Livermore, CA)

    2006-02-21

    This invention describes a solution to the particular problem of liquid water formation in hydrogen getters exposed to quantities of oxygen. Water formation is usually desired because the recombination reaction removes hydrogen without affecting gettering capacity and the oxygen removal reduces the chances for a hydrogen explosion once free oxygen is essentially removed. The present invention describes a getter incorporating a polyacrylate compound that can absorb up to 500% of its own weight in liquid water without significantly affecting its hydrogen gettering/recombination properties, but that also is insensitive to water vapor.

  6. Void-Assisted Ion-Paired Proton Transfer at Water–Ionic Liquid Interfaces

    PubMed Central

    de Eulate, Eva Alvarez; Silvester, Debbie S; Arrigan, Damien W M

    2015-01-01

    At the water–trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate ([P14,6,6,6][FAP]) ionic liquid interface, the unusual electrochemical transfer behavior of protons (H+) and deuterium ions (D+) was identified. Alkali metal cations (such as Li+, Na+, K+) did not undergo this transfer. H+/D+ transfers were assisted by the hydrophobic counter anion of the ionic liquid, [FAP]?, resulting in the formation of a mixed capacitive layer from the filling of the latent voids within the anisotropic ionic liquid structure. This phenomenon could impact areas such as proton-coupled electron transfers, fuel cells, and hydrogen storage where ionic liquids are used as aprotic solvents. PMID:26489692

  7. Case Studies of Water Vapor and Surface Liquid Water from AVIRIS Data Measured Over Denver, CO and Death Valley, CA

    NASA Technical Reports Server (NTRS)

    Gao, B.-C.; Kierein-Young, K. S.; Goetz, A. F. H.; Westwater, E. R.; Stankov, B. B.; Birkenheuer, D.

    1991-01-01

    High spatial resolution column atmospheric water vapor amounts and equivalent liquid water thicknesses of surface targets are retrieved from spectral data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). The retrievals are made using a nonlinear least squares curve fitting technique. Two case studies from AVIRIS data acquired over Denver-Platteville area, Colorado and over Death Valley, California are presented. The column water vapor values derived from AVIRIS data over the Denver-Platteville area are compared with those obtained from radiosondes, ground level upward-looking microwave radiometers, and geostationary satellite measurements. The column water vapor image shows spatial variation patterns related to the passage of a weather front system. The column water vapor amounts derived from AVIRIS data over Death Valley decrease with increasing surface elevation. The derived liquid water image clearly shows surface drainage patterns.

  8. CREDO analysis: a comparison of liquid metal and water valve reliabilities

    SciTech Connect

    Painter, S L; Knee, H E; Humphrys, B

    1985-01-01

    In this paper, data from the Centralized Reliability Data Organization (CREDO) are used to calculate failure rates and unscheduled maintenance frequencies for liquid metal valves. These failure rates and unscheduled maintenance frequencies are then compared to those calculated for valves from light water reactors. The liquid metal valves showed, in general, failure rates and unscheduled maintenance frequencies that are significantly lower than those of water valves (sometimes as much as an order of magnitude). Two possible reasons for the trend of lower failure rates and maintenance frequencies for liquid metal valves are then discussed.

  9. Simulation of water vapor condensation on LOX droplet surface using liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Powell, Eugene A.

    1988-01-01

    The formation of ice or water layers on liquid oxygen (LOX) droplets in the Space Shuttle Main Engine (SSME) environment was investigated. Formulation of such ice/water layers is indicated by phase-equilibrium considerations under conditions of high partial pressure of water vapor (steam) and low LOX droplet temperature prevailing in the SSME preburner or main chamber. An experimental investigation was begun using liquid nitrogen as a LOX simulant. A monodisperse liquid nitrogen droplet generator was developed which uses an acoustic driver to force the stream of liquid emerging from a capillary tube to break up into a stream of regularly space uniformly sized spherical droplets. The atmospheric pressure liquid nitrogen in the droplet generator reservoir was cooled below its boiling point to prevent two phase flow from occurring in the capillary tube. An existing steam chamber was modified for injection of liquid nitrogen droplets into atmospheric pressure superheated steam. The droplets were imaged using a stroboscopic video system and a laser shadowgraphy system. Several tests were conducted in which liquid nitrogen droplets were injected into the steam chamber. Under conditions of periodic droplet formation, images of 600 micron diameter liquid nitrogen droplets were obtained with the stroboscopic video systems.

  10. Density fluctuations and dielectric constant of water in low and high density liquid states

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik; Zhang, Cui; Galli, Giulia A.; Franzese, Giancarlo; Stanley, H. Eugene

    2012-02-01

    The hypothesis of a liquid-liquid critical point (LLCP) in the phase diagram of water, though first published many years ago, still remains the subject of a heated debate. According to this hypothesis there exists a critical point near T 244 K, and P 215 MPa, located at the end of a coexistence line between a high density liquid (HDL) and a low density liquid state (LDL). The LLCP lies below the homogenous nucleation temperature of water and it has so far remained inaccessible to experiments. We study a model of water exhibiting a liquid-liquid phase transition (that is a liquid interacting through the ST2 potential) and investigate the properties of dipolar fluctuations as a function of density, in the HDL and LDL. We find an interesting correlation between the macroscopic dielectric constants and the densities of the two liquids in the vicinity of the critical point, and we discuss possible implications for measurements close to the region where the LLCP may be located.

  11. Liquid-vapor equilibrium isotopic fractionation of water: How well can classical water models predict it?

    NASA Astrophysics Data System (ADS)

    Chialvo, Ariel A.; Horita, Juske

    2009-03-01

    The liquid-vapor equilibrium isotopic fractionation of water is determined by molecular-based simulation, via Gibbs ensemble Monte Carlo and isothermal-isochoric molecular dynamics involving two radically different but realistic models, the extended simple point charge, and the Gaussian charge polarizable models. The predicted temperature dependence of the liquid-vapor equilibrium isotopic fractionation factors for H2O18/H2O16, H2O17/H2O16, and H2H1O16/H21O16 are compared against the most accurate experimental datasets to assess the ability of these intermolecular potential models to describe quantum effects according to the Kirkwood-Wigner free energy perturbation ?2-expansion. Predictions of the vapor pressure isotopic effect for the H2O18/H2O16 and H2O17/H2O16 pairs are also presented in comparison with experimental data and two recently proposed thermodynamic modeling approaches. Finally, the simulation results are used to discuss some approximations behind the microscopic interpretation of isotopic fractionation based on the underlying rototranslational coupling.

  12. Three types of liquid water in icy surfaces of celestial bodies

    NASA Astrophysics Data System (ADS)

    Möhlmann, D.

    2011-08-01

    It is shown that, at temperatures far below the triple point and under appropriate conditions, liquid water can stably or temporarily exist in upper ice-covered surfaces of planetary bodies (like Mars) in three different types: undercooled interfacial water (due to freezing point depression by van der Waals forces and "premelting"), water in brines (due to freezing point depression in solutions), and sub-surface melt water (due to a solid-state greenhouse effect driven heating). The physics behind and the related conditions for these liquid waters to evolve and to exist, and possibly related consequences, are discussed. These calculations are mainly made in view of the possible presence of these sub-surface liquids in the upper surface of the present Mars.

  13. Distribution of aquifers, liquid-waste impoundments, and municipal water-supply sources, Massachusetts

    USGS Publications Warehouse

    Delaney, David F.; Maevsky, Anthony

    1980-01-01

    Impoundments of liquid waste are potential sources of ground-water contamination in Massachusetts. The map report, at a scale of 1 inch equals 4 miles, shows the idstribution of aquifers and the locations of municipal water-supply sources and known liquid-waste impoundments. Ground water, an important source of municipal water supply, is produced from shallow sand and gravel aquifers that are generally unconfined, less than 200 feet thick, and yield less than 2,000 gallons per minute to individual wells. These aquifers commonly occupy lowlands and stream valleys and are most extensive in eastern Massachusetts. Surface impoundments of liquid waste are commonly located over these aquifers. These impoundments may leak and allow waste to infiltrate underlying aquifers and alter their water quality. (USGS)

  14. Brillouin-scattering study of liquid-glass transitions in ternary mixtures of water, trehalose, and an ionic liquid

    NASA Astrophysics Data System (ADS)

    Takayama, Haruki; Shibata, Tomohiko; Ishii, Takahiro; Kojima, Seiji

    2013-04-01

    Ternary mixtures of water, sugar, and ionic liquid have been studied as new candidates for bioprotectants. To clarify the elastic properties and relaxation dynamics of the supercooled liquid and glassy states at low temperatures, the liquid-glass transitions were investigated by using a micro-Brillouin-scattering technique. The refractive index was measured accurately as a function of content and temperature to determine the sound velocity and the attenuation from Brillouin frequency shift and peak width. The relaxation times of structural relaxations related to liquidglass transitions were determined as functions of temperature. The Meyer-Neldel rule was found to hold for the activation energy and the prefactor of the Arrhenius law for the relaxation time.

  15. September 11, 2013 17:26 WSPC -Proceedings Trim Size: 9in x 6in perspectives Polyamorphism and polymorphism of a confined water

    E-print Network

    Franzese, Giancarlo

    in order to answer fundamental questions related to the origin of its anomalies and to predict new testable.11 Water is undoubtedly the most important liquid for life as we know it. More than 60% of the human water. Then we study a many-body model for a water monolayer confined between hydrophobic plates

  16. Identification of single nucleotide polymorphism markers associated with bacterial cold water disease resistance and spleen size in rainbow trout

    PubMed Central

    Liu, Sixin; Vallejo, Roger L.; Palti, Yniv; Gao, Guangtu; Marancik, David P.; Hernandez, Alvaro G.; Wiens, Gregory D.

    2015-01-01

    Bacterial cold water disease (BCWD) is one of the frequent causes of elevated mortality in salmonid aquaculture. Previously, we identified and validated microsatellites on chromosome Omy19 associated with QTL (quantitative trait loci) for BCWD resistance and spleen size in rainbow trout. Recently, SNPs (single nucleotide polymorphism) have become the markers of choice for genetic analyses in rainbow trout as they are highly abundant, cost-effective and are amenable for high throughput genotyping. The objective of this study was to identify SNP markers associated with BCWD resistance and spleen size using both genome-wide association studies (GWAS) and linkage-based QTL mapping approaches. A total of 298 offspring from the two half-sib families used in our previous study to validate the significant BCWD QTL on chromosome Omy19 were genotyped with RAD-seq (restriction-site-associated DNA sequencing), and 7,849 informative SNPs were identified. Based on GWAS, 18 SNPs associated with BCWD resistance and 20 SNPs associated with spleen size were identified. Linkage-based QTL mapping revealed three significant QTL for BCWD resistance. In addition to the previously validated dam-derived QTL on chromosome Omy19, two significant BCWD QTL derived from the sires were identified on chromosomes Omy8 and Omy25, respectively. A sire-derived significant QTL for spleen size on chromosome Omy2 was detected. The SNP markers reported in this study will facilitate fine mapping to identify positional candidate genes for BCWD resistance in rainbow trout. PMID:26442114

  17. Selective extraction of copper, mercury, silver and palladium ionsfrom water using hydrophobic ionic liquids.

    SciTech Connect

    Papaiconomou, Nicolas; Lee, Jong-Min; Salminen, Justin; VonStosch, Moritz; Prausnitz, John M.

    2007-06-25

    Extraction of dilute metal ions from water was performed near room temperature with a variety of ionic liquids. Distribution coefficients are reported for fourteen metal ions extracted with ionic liquids containing cations 1-octyl-4-methylpyridinium [4MOPYR]{sup +}, 1-methyl-1-octylpyrrolidinium [MOPYRRO]{sup +} or 1-methyl-1-octylpiperidinium [MOPIP]{sup +}, and anions tetrafluoroborate [BF{sub 4}]{sup +}, trifluoromethyl sulfonate [TfO]{sup +} or nonafluorobutyl sulfonate [NfO]{sup +}. Ionic liquids containing octylpyridinium cations are very good for extracting mercury ions. However, other metal ions were not significantly extracted by any of these ionic liquids. Extractions were also performed with four new task-specific ionic liquids. Such liquids containing a disulfide functional group are efficient and selective for mercury and copper, whereas those containing a nitrile functional group are efficient and selective for silver and palladium.

  18. Ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction and derivatization of sulfonamides in river water, honey, milk, and animal plasma.

    PubMed

    Xu, Xu; Su, Rui; Zhao, Xin; Liu, Zhuang; Zhang, Yupu; Li, Dan; Li, Xueyuan; Zhang, Hanqi; Wang, Ziming

    2011-11-30

    The ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction (IL-based MADLLME) and derivatization was applied for the pretreatment of six sulfonamides (SAs) prior to the determination by high-performance liquid chromatography (HPLC). By adding methanol (disperser), fluorescamine solution (derivatization reagent) and ionic liquid (extraction solvent) into sample, extraction, derivatization, and preconcentration were continuously performed. Several experimental parameters, such as the type and volume of extraction solvent, the type and volume of disperser, amount of derivatization reagent, microwave power, microwave irradiation time, pH of sample solution, and ionic strength were investigated and optimized. When the microwave power was 240 W, the analytes could be derivatized and extracted simultaneously within 90 s. The proposed method was applied to the analysis of river water, honey, milk, and pig plasma samples, and the recoveries of analytes obtained were in the range of 95.0-110.8, 95.4-106.3, 95.0-108.3, and 95.7-107.7, respectively. The relative standard deviations varied between 1.5% and 7.3% (n=5). The results showed that the proposed method was a rapid, convenient and feasible method for the determination of SAs in liquid samples. PMID:22027124

  19. Liquid Water Cloud Measurements Using the Raman Lidar Technique: Current Understanding and Future Research Needs

    NASA Technical Reports Server (NTRS)

    Tetsu, Sakai; Whiteman, David N.; Russo, Felicita; Turner, David D.; Veselovskii, Igor; Melfi, S. Harvey; Nagai, Tomohiro; Mano, Yuzo

    2013-01-01

    This paper describes recent work in the Raman lidar liquid water cloud measurement technique. The range-resolved spectral measurements at the National Aeronautics and Space Administration Goddard Space Flight Center indicate that the Raman backscattering spectra measured in and below low clouds agree well with theoretical spectra for vapor and liquid water. The calibration coefficients of the liquid water measurement for the Raman lidar at the Atmospheric Radiation Measurement Program Southern Great Plains site of the U.S. Department of Energy were determined by comparison with the liquid water path (LWP) obtained with Atmospheric Emitted Radiance Interferometer (AERI) and the liquid water content (LWC) obtained with the millimeter wavelength cloud radar and water vapor radiometer (MMCR-WVR) together. These comparisons were used to estimate the Raman liquid water cross-sectional value. The results indicate a bias consistent with an effective liquid water Raman cross-sectional value that is 28%-46% lower than published, which may be explained by the fact that the difference in the detectors' sensitivity has not been accounted for. The LWP of a thin altostratus cloud showed good qualitative agreement between lidar retrievals and AERI. However, the overall ensemble of comparisons of LWP showed considerable scatter, possibly because of the different fields of view of the instruments, the 350-m distance between the instruments, and the horizontal inhomogeneity of the clouds. The LWC profiles for a thick stratus cloud showed agreement between lidar retrievals andMMCR-WVR between the cloud base and 150m above that where the optical depth was less than 3. Areas requiring further research in this technique are discussed.

  20. Drilling to Extract Liquid Water on Mars: Feasible and Worth the Investment

    NASA Technical Reports Server (NTRS)

    Stoker, C.

    2004-01-01

    A critical application for the success of the Exploration Mission is developing cost effective means to extract resources from the Moon and Mars needed to support human exploration. Water is the most important resource in this regard, providing a critical life support consumable, the starting product of energy rich propellants, energy storage media (e.g. fuel cells), and a reagent used in virtually all manufacturing processes. Water is adsorbed and chemically bound in Mars soils, ice is present near the Martian surface at high latitudes, and water vapor is a minor atmospheric constituent, but extracting meaningful quantities requires large complex mechanical systems, massive feedstock handling, and large energy inputs. Liquid water aquifers are almost certain to be found at a depth of several kilometers on Mars based on our understanding of the average subsurface thermal gradient, and geological evidence from recent Mars missions suggests liquid water may be present much closer to the surface at some locations. The discovery of hundreds of recent water-carved gullies on Mars indicates liquid water can be found at depths of 200-500 meters in many locations. Drilling to obtain liquid water via pumping is therefore feasible and could lower the cost and improve the return of Mars exploration more than any other ISRU technology on the horizon. On the Moon, water ice may be found in quantity in permanently shadowed regions near the poles.

  1. The vibrational spectrum of water in liquid alkanes.

    PubMed Central

    Conrad, M P; Strauss, H L

    1985-01-01

    The water wire hypothesis of hydrogen-ion transport in lipid bilayers has prompted a search for water aggregates in bulk hydrocarbons. The asymmetric stretching vibration of the water dissolved in n-decane and in a number of other alkanes and alkenes has been observed. The water band in the alkanes is very wide and fits to the results of a J-diffusion calculation for the water rotation. This implies that the water is freely rotating between collisions with the solvent and certainly not hydrogen bonded to anything. The existence of water aggregates is thus most unlikely. In contrast, water in an alkene is hydrogen bonded to the solvent molecules (although not to other water molecules) and shows an entirely different spectrum. PMID:4016205

  2. Thermodynamics of open networks: Ordering and entropy in NaAlSiO4 glass, liquid, and polymorphs

    USGS Publications Warehouse

    Richet, P.; Robie, R.A.; Rogez, J.; Hemingway, B.S.; Courtial, P.; Tequi, C.

    1990-01-01

    The thermodynamic properties of carnegieite and NaAlSiO4 glass and liquid have been investigated through Cp determinations from 10 to 1800 K and solution-calorimetry measurements. The relative entropies S298-S0 of carnegieite and NaAlSiO4 glass are 118.7 and 124.8 J/mol K, respectively. The low-high carnegieite transition has been observed at 966 K with an enthalpy of transition of 8.1??0.3 kJ/mol, and the enthalpy of fusion of carnegieite at the congruent melting point of 1799 K is 21.7??3 kJ/mol. These results are consistent with the reported temperature of the nepheline-carnegieite transition and available thermodynamic data for nepheline. The entropy of quenched NaAlSiO4 glass at 0 K is 9.7??2 J/mol K and indicates considerable ordering among AlO4 and SiO4 tetrahedra. In the liquid state, progressive, temperature-induced Si, Al disordering could account for the high configurational heat capacity. Finally, the differences between the entropies and heat capacities of nepheline and carnegieite do not seem to conform to current polyhedral modeling of these properties ?? 1990 Springer-Verlag.

  3. Screen-printed electrode based electrochemical detector coupled with ionic liquid dispersive liquid-liquid microextraction and microvolume back-extraction for determination of mercury in water samples.

    PubMed

    Fernández, Elena; Vidal, Lorena; Martín-Yerga, Daniel; Blanco, María del Carmen; Canals, Antonio; Costa-García, Agustín

    2015-04-01

    A novel approach is presented, whereby gold nanostructured screen-printed carbon electrodes (SPCnAuEs) are combined with in-situ ionic liquid formation dispersive liquid-liquid microextraction (in-situ IL-DLLME) and microvolume back-extraction for the determination of mercury in water samples. In-situ IL-DLLME is based on a simple metathesis reaction between a water-miscible IL and a salt to form a water-immiscible IL into sample solution. Mercury complex with ammonium pyrrolidinedithiocarbamate is extracted from sample solution into the water-immiscible IL formed in-situ. Then, an ultrasound-assisted procedure is employed to back-extract the mercury into 10 µL of a 4 M HCl aqueous solution, which is finally analyzed using SPCnAuEs. Sample preparation methodology was optimized using a multivariate optimization strategy. Under optimized conditions, a linear range between 0.5 and 10 µg L(-1) was obtained with a correlation coefficient of 0.997 for six calibration points. The limit of detection obtained was 0.2 µg L(-1), which is lower than the threshold value established by the Environmental Protection Agency and European Union (i.e., 2 µg L(-1) and 1 µg L(-1), respectively). The repeatability of the proposed method was evaluated at two different spiking levels (3 and 10 µg L(-1)) and a coefficient of variation of 13% was obtained in both cases. The performance of the proposed methodology was evaluated in real-world water samples including tap water, bottled water, river water and industrial wastewater. Relative recoveries between 95% and 108% were obtained. PMID:25640123

  4. Are nanometric films of liquid undercooled interfacial water bio-relevant?

    PubMed

    Möhlmann, Diedrich T F

    2009-06-01

    It is known that life processes below the melting point temperature can actively evolve and establish in micrometer-sized (and larger) veins and structures in ice and permafrost soil, filled with unfrozen water. Thermodynamic arguments and experimental results indicate the existence of much smaller nanometer sized thin films of undercooled liquid interfacial (ULI) water on surfaces of micrometer sized and larger mineral particles and microbes in icy environments far below the melting point temperature. This liquid interfacial water can be described in terms of a freezing point depression, which is due to the interfacial pressure of van der Waals forces. The physics behind the possibly also life supporting capability of nanometric films of undercooled liquid interfacial water, which also can "mantle" the surfaces of the much larger and micrometer-sized microbes, is discussed. As described, biological processes do not necessarily have to proceed in the "bulk" of the thin interfacial water, as in "vinical" water and in the micrometer sized veins e.g., but they can be supported or are even made possible already by covering thin mantles of liquid interfacial water. These can provide liquid water for metabolic processes and act as carrier for the necessary transport of nutrients and waste. ULI water supports two different and possibly biologically relevant transport processes: 2D molecular diffusion in the interfacial film, and flow-like due to regelation. ULI-water, which is "lost" by transport into microbes, e.g., will be refilled from the neighbouring ice. In this way, the nanometric liquid environment of microbes in ULI-water is comparable to that of microbes in bulk water. Another probably also biologically relevant property of ULI is, depending on the hydrophobic or hydrophilic character of the surfaces, that it is of lower density (LDL) or higher density (HDL) than bulk water. Furthermore, capillary effects and ions in ULI-water solutions can support, enhance, and stabilize the formation of layers of interfacial water. A more detailed future investigation of the possible support of life processes by nanometric ULI water in ice is a challenge to current cryomicrobiology. Related results of Rivkina et al. [22] indeed indicate that life processes can remain active at water contents corresponding to about or less than two monolayers of ULI water. PMID:19444970

  5. Liquid water dynamics in unsaturated snow: the role of lateral flow

    NASA Astrophysics Data System (ADS)

    Marshall, H. P.; Heilig, A.; Evans, S.; Robertson, M. E.; Hetrick, H. F.; Eiriksson, D.; Dean, J.; Karlson, A.; Hedrick, A. R.; Bradford, J.; McNamara, J. P.; Flores, A. N.; Kohn, M. J.; Rodriguez, C.

    2014-12-01

    The movement of liquid water in unsaturated snow is a complex and highly heterogeneous process, due to positive feedback mechanisms that lead to distinct flow pathways. A combination of gravitational and capillary forces, combined with small scale spatial variability, causes liquid water to concentrate into sub-meter vertical channels and along stratigraphic boundaries that lead to complicated patterns of volumetric water content. Hydraulic conductivity increases significantly with liquid water content, leading to preferential flow along established pathways. We designed controlled experiments to explore the role of slope-parallel flow of liquid water in unsaturated snow, along layer boundaries, to improve understanding of potential lateral mass redistribution during rapid melt and rain-on-snow events on ice sheets, glaciers and in seasonal snow. We characterized snow structure and monitored the spatiotemporal distribution of liquid water during snowmelt and rain-on-snow events using high-resolution radars, micropenetrometry, near-infrared and time-lapse photography, in-situ dielectric probes, and stable isotopes. We used the seasonal snowpack as a natural laboratory, and collected water outflow with lysimeter arrays designed to quantify the amount of water moving laterally. A co-located full energy-balance weather station provides forcing inputs for modeling, and the degree of lateral flow is also evaluated by monitoring the evolution of soil moisture with a permenantly installed ERT array and multiple dielectric probes in the soil at the base of the snowpack. Improved understanding of liquid water dynamics in unsaturated snow and firn is required for accurate modeling of the percolation zone mass balance on ice sheets and polar glaciers, the timing of wet snow avalanches, and flooding caused by mid-winter rain on seasonal snow.

  6. FEATURE ARTICLE Investigations of the Structure and Hydrogen Bonding of Water Molecules at Liquid

    E-print Network

    Richmond, Geraldine L.

    FEATURE ARTICLE Investigations of the Structure and Hydrogen Bonding of Water Molecules at Liquid of Chemistry, UniVersity of Oregon, Eugene, Oregon 97403 ReceiVed: December 30, 1997; In Final Form: March 12, 1998 The structure and hydrogen bonding of water molecules provides this unique solvent with properties

  7. Determination of cloud liquid water distribution using 3D cloud tomography

    E-print Network

    , but they provide a less direct measurement of cloud water content (since radar reflectivity depends strongly techniques like cloud radar [Hogan et al., 2005] with rapid scanning capability seem promisingDetermination of cloud liquid water distribution using 3D cloud tomography Dong Huang,1 Yangang Liu

  8. Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons.

    PubMed

    Qiu, Hu; Zeng, Xiao Cheng; Guo, Wanlin

    2015-10-27

    Phase behavior and the associated phase transition of water within inhomogeneous nanoconfinement are investigated using molecular dynamics simulations. The nanoconfinement is constructed by a flat bottom plate and a convex top plate. At 300 K, the confined water can be viewed as a coexistence of monolayer, bilayer, and trilayer liquid domains to accommodate the inhomogeneous confinement. With increasing liquid density, the confined water with uneven layers transforms separately into two-dimensional ice crystals with unchanged layer number and rhombic in-plane symmetry for oxygen atoms. The monolayer water undergoes the transition first into a puckered ice nanoribbon, and the bilayer water transforms into a rhombic ice nanoribbon next, followed by the transition of trilayer water into a trilayer ice nanoribbon. The sequential localized liquid-to-solid transition within the inhomogeneous confinement can also be achieved by gradually decreasing the temperature at low liquid densities. These findings of phase behaviors of water under the inhomogeneous nanoconfinement not only extend the phase diagram of confined water but also have implications for realistic nanofluidic systems and microporous materials. PMID:26348704

  9. Raman Thermometry Measurements of Free Evaporation from Liquid Water Droplets

    E-print Network

    Cohen, Ronald C.

    - ments of the temperature profile across the surface of a rapidly evaporating liquid-vapor interface exhibited a discontinuous temperature increase, wherein the vapor directly above the surface was as much than or equal to that of the surface.1,3 In fact, an elevated vapor temperature suggests there exists

  10. Mesoscopic modeling of liquid water transport in polymer electrolyte fuel cells

    SciTech Connect

    Mukherjee, Partha P; Wang, Chao Yang

    2008-01-01

    A key performance limitation in polymer electrolyte fuel cells (PEFC), manifested in terms of mass transport loss, originates from liquid water transport and resulting flooding phenomena in the constituent components. Liquid water leads to the coverage of the electrochemically active sites in the catalyst layer (CL) rendering reduced catalytic activity and blockage of the available pore space in the porous CL and fibrous gas diffusion layer (GDL) resulting in hindered oxygen transport to the active reaction sites. The cathode CL and the GDL therefore playa major role in the mass transport loss and hence in the water management of a PEFC. In this article, we present the development of a mesoscopic modeling formalism coupled with realistic microstructural delineation to study the profound influence of the pore structure and surface wettability on liquid water transport and interfacial dynamics in the PEFC catalyst layer and gas diffusion layer.

  11. Dosimetric characterization of a {sup 131}Cs brachytherapy source by thermoluminescence dosimetry in liquid water

    SciTech Connect

    Tailor, Ramesh; Ibbott, Geoffrey; Lampe, Stephanie; Bivens Warren, Whitney; Tolani, Naresh

    2008-12-15

    Dosimetry measurements of a {sup 131}Cs brachytherapy source have been performed in liquid water employing thermoluminescence dosimeters. A search of the literature reveals that this is the first time a complete set of dosimetric parameters for a brachytherapy ''seed'' source has been measured in liquid water. This method avoids the medium correction uncertainties introduced by the use of water-equivalent plastic phantoms. To assure confidence in the results, four different sources were employed for each parameter measured, and measurements were performed multiple times. The measured dosimetric parameters presented here are based on the AAPM Task Group 43 formalism. The dose-rate constant measured in liquid water was (1.063{+-}0.023) cGy h{sup -1} U{sup -1} and was based on the air-kerma strength standard for this source established by the National Institute of Standards and Technology. Measured values for the 2D anisotropy function and the radial dose function are presented.

  12. Formation of Martian Gullies by the Flow of Simultaneously Freezing and Boiling Liquid Water

    NASA Technical Reports Server (NTRS)

    Heldmann, Jennifer L.; Mellon, Michael T.; Toon, Owen B.; Pollard, Wayne H.; Mellon, Michael T.; Pitlick, John; McKay, Christopher P.; Andersen, Dale T.

    2004-01-01

    Geomorphic evidence suggests that recent gullies on Mars were formed by fluvial activity. The Martian gully features are significant because their existence implies the presence of liquid water near the surface on Mars in geologically recent times. Irrespective of the ultimate source of the fluid carving the gullies, we seek to understand the behavior of this fluid after it reaches the Martian surface. We find that, contrary to popular belief, the fluvially-carved Martian gullies require formation conditions such as now occur on Mars, outside of the temperature-pressure stability regime of liquid water. Mars Global Surveyor observations of gully length and our modeling of water stability are consistent with gully formation from the action of pure liquid water that is simultaneously boiling and freezing.

  13. Photoelectron spectroscopy of liquid water, some alcohols, and pure nonane in free micro jets

    NASA Astrophysics Data System (ADS)

    Faubel, Manfred; Steiner, Björn; Toennies, J. Peter

    1997-06-01

    The recently developed technique of accessing volatile liquids in a high vacuum environment by using a very thin liquid jet is implemented to carry out the first measurements of photoelectron spectra of pure liquid water, methanol, ethanol, 1-propanol, 1-butanol, and benzyl alcohol as well as of liquid n-nonane. The apparatus, which consists of a commercial hemispherical (10 cm mean radius) electron analyzer and a hollow cathode discharge He I light source is described in detail and the problems of the sampling of the photoelectrons in such an environment are discussed. For water and most of the alcohols up to six different electronic bands could be resolved. The spectra of 1-butanol and n-nonane show two weakly discernable peaks from which the threshold ionization potential could be determined. A deconvolution of the photoelectron spectra is used to extract ionization potentials of individual molecular bands of molecules near the surface of the liquid and shifts of the order of 1 eV compared to the gas phase are observed. A molecular orientation for water molecules at the surface of liquid water is inferred from a comparison of the relative band strengths with the gas phase. Similar effects are also observed for some of the alcohols. The results are discussed in terms of a simple "Born-solvation" model.

  14. Glass Transition in Biomolecules and the Liquid-Liquid Critical Point of Water Pradeep Kumar,1

    E-print Network

    Buldyrev, Sergey

    such as isobaric specific heat CP and isothermal compressibility have maxima as functions of temperature crystallization of bulk water. It was found that water remains unfrozen in hydrophilic nanopores for T > 200 K [19

  15. Interactions between liquid-water and gas-diffusion layers in polymer-electrolyte fuel cells

    DOE PAGESBeta

    Das, Prodip K.; Santamaria, Anthony D.; Weber, Adam Z.

    2015-06-11

    Over the past few decades, a significant amount of research on polymer-electrolyte fuel cells (PEFCs) has been conducted to improve performance and durability while reducing the cost of fuel cell systems. However, the cost associated with the platinum (Pt) catalyst remains a barrier to their commercialization and PEFC durability standards have yet to be established. An effective path toward reducing PEFC cost is making the catalyst layers (CLs) thinner thus reducing expensive Pt content. The limit of thin CLs is high gas-transport resistance and the performance of these CLs is sensitive to the operating temperature due to their inherent lowmore »water uptake capacity, which results in higher sensitivity to liquid-water flooding and reduced durability. Therefore, reducing PEFC's cost by decreasing Pt content and improving PEFC's performance and durability by managing liquid-water are still challenging and open topics of research. An overlooked aspect nowadays of PEFC water management is the gas-diffusion layer (GDL). While it is known that GDL's properties can impact performance, typically it is not seen as a critical component. In this work, we present data showing the importance of GDLs in terms of water removal and management while also exploring the interactions between liquid-water and GDL surfaces. The critical interface of GDL and gas-flow-channel in the presence of liquid-water was examined through systematic studies of adhesion forces as a function of water-injection rate for various GDLs of varying thickness. GDL properties (breakthrough pressure and adhesion force) were measured experimentally under a host of test conditions. Specifically, the effects of GDL hydrophobic (PTFE) content, thickness, and water-injection rate were examined to identify trends that may be beneficial to the design of liquid-water management strategies and next-generation GDL materials for PEFCs.« less

  16. Interactions between liquid-water and gas-diffusion layers in polymer-electrolyte fuel cells

    SciTech Connect

    Das, Prodip K.; Santamaria, Anthony D.; Weber, Adam Z.

    2015-06-11

    Over the past few decades, a significant amount of research on polymer-electrolyte fuel cells (PEFCs) has been conducted to improve performance and durability while reducing the cost of fuel cell systems. However, the cost associated with the platinum (Pt) catalyst remains a barrier to their commercialization and PEFC durability standards have yet to be established. An effective path toward reducing PEFC cost is making the catalyst layers (CLs) thinner thus reducing expensive Pt content. The limit of thin CLs is high gas-transport resistance and the performance of these CLs is sensitive to the operating temperature due to their inherent low water uptake capacity, which results in higher sensitivity to liquid-water flooding and reduced durability. Therefore, reducing PEFC's cost by decreasing Pt content and improving PEFC's performance and durability by managing liquid-water are still challenging and open topics of research. An overlooked aspect nowadays of PEFC water management is the gas-diffusion layer (GDL). While it is known that GDL's properties can impact performance, typically it is not seen as a critical component. In this work, we present data showing the importance of GDLs in terms of water removal and management while also exploring the interactions between liquid-water and GDL surfaces. The critical interface of GDL and gas-flow-channel in the presence of liquid-water was examined through systematic studies of adhesion forces as a function of water-injection rate for various GDLs of varying thickness. GDL properties (breakthrough pressure and adhesion force) were measured experimentally under a host of test conditions. Specifically, the effects of GDL hydrophobic (PTFE) content, thickness, and water-injection rate were examined to identify trends that may be beneficial to the design of liquid-water management strategies and next-generation GDL materials for PEFCs.

  17. Liquid Water Transport in the Reactant Channels of Proton Exchange Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Banerjee, Rupak

    Water management has been identified as a critical issue in the development of PEM fuel cells for automotive applications. Water is present inside the PEM fuel cell in three phases, i.e. liquid phase, vapor phase and mist phase. Liquid water in the reactant channels causes flooding of the cell and blocks the transport of reactants to the reaction sites at the catalyst layer. Understanding the behavior of liquid water in the reactant channels would allow us to devise improved strategies for removing liquid water from the reactant channels. In situ fuel cell tests have been performed to identify and diagnose operating conditions which result in the flooding of the fuel cell. A relationship has been identified between the liquid water present in the reactant channels and the cell performance. A novel diagnostic technique has been established which utilizes the pressure drop multiplier in the reactant channels to predict the flooding of the cell or the drying-out of the membrane. An ex-situ study has been undertaken to quantify the liquid water present in the reactant channels. A new parameter, the Area Coverage Ratio (ACR), has been defined to identify the interfacial area of the reactant channel which is blocked for reactant transport by the presence of liquid water. A parametric study has been conducted to study the effect of changing temperature and the inlet relative humidity on the ACR. The ACR decreases with increase in current density as the gas flow rates increase, removing water more efficiently. With increase in temperature, the ACR decreases rapidly, such that by 60°C, there is no significant ACR to be reported. Inlet relative humidity of the gases does change the saturation of the gases in the channel, but did not show any significant effect on the ACR. Automotive powertrains, which is the target for this work, are continuously faced with transient changes. Water management under transient operating conditions is significantly more challenging and has not been investigated in detail. This study begins to investigate the effects of changing operating conditions on liquid water transport through the reactant channels. It has been identified that rapidly increasing temperature leads to the dry-out of the membrane and rapidly cooling the cell below 55°C results in the start of cell flooding. In changing the operating load of the PEMFC, overshoot in the pressure drop in the reactant channel has been identified for the first time as part of this investigation. A parametric study has been conducted to identify the factors which influence this overshoot behavior.

  18. Conformational Heat Capacity of Liquid Biodegradable Polymers in the Absence and Presence Water

    NASA Astrophysics Data System (ADS)

    Pyda, Marek; Nowak-Pyda, Elzbieta

    2007-03-01

    The conformational heat capacity of biodegradable polymers such as amorphous poly(lactic acid) PLA and starch with and without water have been evaluated from a fit of experimental data to a one-dimensional Ising-like model for two discrete states, characterized by parameters linked to stiffness, cooperativity, and degeneracy. For the starch-water system the additional changes in the conformational heat capacity arise from the interaction of the carbohydrate chains with water. The liquid heat capacities at constant pressure Cp, of amorphous PLA and partially liquid state of starch, starch-water have been computed as the sum of vibrational, external, and conformational contributions. The vibrational contribution was calculated as the heat capacity arising from group and skeletal vibrations. The external contribution was estimated from experimental data of the thermal expansivity and compressibility in the liquid state. The experimental liquid Cp agrees with these calculations to better than ±3%. The calculated liquid Cp with the solid Cp was employed in the quantitative thermal analysis of the experimental Cp of biodegradable polymer PLA, starch, and starch-water. Supported by European Union, grant (MIRG-CT-2006-036558), Cargill Dow LLC

  19. Bulk volumetric liquid water content in a seasonal snowpack: modeling its dynamics in different climatic conditions

    NASA Astrophysics Data System (ADS)

    Avanzi, Francesco; Yamaguchi, Satoru; Hirashima, Hiroyuki; De Michele, Carlo

    2015-12-01

    We focus on the dynamics of volumetric liquid water content in seasonal snow covers. This is a key variable describing the fate of snowpacks during the melting season. However, its measurement and/or prediction by means of models at high spatial and temporal resolutions is still difficult due to both practical and theoretical reasons. To overcome these limitations in operational applications, we test the capability of a one-dimensional model to predict the dynamics of bulk volumetric liquid water content during a snow season. Multi-year data collected in three experimental sites in Japan are used as an evaluation. These sites are subjected to different climatic conditions. The model requires the calibration of one or two parameters, according to the degree of detail used. Either a simple temperature-index or a coupled melt-freeze temperature-index approach are considered to predict melting and/or melt-freeze dynamics of liquid water. Results show that, if melt-freeze dynamics are modeled, median absolute differences between data and predictions are consistently lower than 1 vol% at the sites where data of liquid water content are available. In addition, we find also that the model predicts correctly a dry condition in 80% of the observed cases at a site where calibration data are scarce. At the same site, observed isothermal conditions of the snow cover at 0 °C correspond to predictions of bulk volumetric liquid water content that are greater than 0.

  20. Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Miceli, Giacomo; de Gironcoli, Stefano; Pasquarello, Alfredo

    2015-01-01

    We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed analysis comprising the study of the partial radial distribution functions, various local order indices, the hydrogen-bond network, and the selfdiffusion coefficient. The explicit treatment of the van der Waals interactions leads to an overall improved description of liquid water.

  1. Isobaric first-principles molecular dynamics of liquid water with nonlocal van der Waals interactions.

    PubMed

    Miceli, Giacomo; de Gironcoli, Stefano; Pasquarello, Alfredo

    2015-01-21

    We investigate the structural properties of liquid water at near ambient conditions using first-principles molecular dynamics simulations based on a semilocal density functional augmented with nonlocal van der Waals interactions. The adopted scheme offers the advantage of simulating liquid water at essentially the same computational cost of standard semilocal functionals. Applied to the water dimer and to ice Ih, we find that the hydrogen-bond energy is only slightly enhanced compared to a standard semilocal functional. We simulate liquid water through molecular dynamics in the NpH statistical ensemble allowing for fluctuations of the system density. The structure of the liquid departs from that found with a semilocal functional leading to more compact structural arrangements. This indicates that the directionality of the hydrogen-bond interaction has a diminished role as compared to the overall attractions, as expected when dispersion interactions are accounted for. This is substantiated through a detailed analysis comprising the study of the partial radial distribution functions, various local order indices, the hydrogen-bond network, and the selfdiffusion coefficient. The explicit treatment of the van der Waals interactions leads to an overall improved description of liquid water. PMID:25612714

  2. Temperature and length scale dependence of solvophobic solvation in a single-site water-like liquid

    E-print Network

    Buldyrev, Sergey

    Temperature and length scale dependence of solvophobic solvation in a single-site water-like liquid, for both the Jagla liquid and water, we observe temperature-dependent enthalpy and entropy of solva- tion temperature. This feature of water-like solvation is distinct from the strictly positive and tempera- ture

  3. Supported liquid membrane-liquid chromatography-mass spectrometry analysis of cyanobacterial toxins in fresh water systems

    NASA Astrophysics Data System (ADS)

    Mbukwa, Elbert A.; Msagati, Titus A. M.; Mamba, Bhekie B.

    Harmful algal blooms (HABs) are increasingly becoming of great concern to water resources worldwide due to indiscriminate waste disposal habits resulting in water pollution and eutrophication. When cyanobacterial cells lyse (burst) they release toxins called microcystins (MCs) that are well known for their hepatotoxicity (causing liver damage) and have been found in eutrophic lakes, rivers, wastewater ponds and other water reservoirs. Prolonged exposure to low concentrated MCs are equally of health importance as they are known to be bioaccumulative and even at such low concentration do exhibit toxic effects to aquatic animals, wildlife and human liver cells. The application of common treatment processes for drinking water sourced from HABs infested reservoirs have the potential to cause algal cell lyses releasing low to higher amounts of MCs in finished water. Trace microcystins in water/tissue can be analyzed and quantified using Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) following solid-phase extraction (SPE) sample clean-up procedures. However, extracting MCs from algal samples which are rich in chlorophyll pigments and other organic matrices the SPE method suffers a number of drawbacks, including cartridge clogging, long procedural steps and use of larger volumes of extraction solvents. We applied a supported liquid membrane (SLM) based technique as an alternative sample clean-up method for LC-ESI-MS analysis of MCs from both water and algal cells. Four (4) MC variants (MC-RR, -YR, -LR and -WR) from lyophilized cells of Microcystis aeruginosa and water collected from a wastewater pond were identified) and quantified using LC-ESI-MS following a SLM extraction and liquid partitioning step, however, MC-WR was not detected from water extracts. Within 45 min of SLM extraction all studied MCs were extracted and pre-concentrated in approximately 15 ?L of an acceptor phase at an optimal pH 2.02 of the donor phase (sample). The highest total quantifiable intracellular and extracellular MCs were 37.039 ± 0.087 ?g/g DW and 5.123 ± 0.018 ?g/L, respectively. The concentrations of MC-RR were the highest from all samples studied recording maximum values of 21.579 ± 0.066 ?g/g DW and 3.199 ± 0.012 ?g/L for intracellular and extracellular quantities, respectively.

  4. Regional water implications of reducing oil imports with liquid transportation fuel alternatives in the United States.

    PubMed

    Jordaan, Sarah M; Diaz Anadon, Laura; Mielke, Erik; Schrag, Daniel P

    2013-01-01

    The Renewable Fuel Standard (RFS) is among the cornerstone policies created to increase U.S. energy independence by using biofuels. Although greenhouse gas emissions have played a role in shaping the RFS, water implications are less understood. We demonstrate a spatial, life cycle approach to estimate water consumption of transportation fuel scenarios, including a comparison to current water withdrawals and drought incidence by state. The water consumption and land footprint of six scenarios are compared to the RFS, including shale oil, coal-to-liquids, shale gas-to-liquids, corn ethanol, and cellulosic ethanol from switchgrass. The corn scenario is the most water and land intense option and is weighted toward drought-prone states. Fossil options and cellulosic ethanol require significantly less water and are weighted toward less drought-prone states. Coal-to-liquids is an exception, where water consumption is partially weighted toward drought-prone states. Results suggest that there may be considerable water and land impacts associated with meeting energy security goals through using only biofuels. Ultimately, water and land requirements may constrain energy security goals without careful planning, indicating that there is a need to better balance trade-offs. Our approach provides policymakers with a method to integrate federal policies with regional planning over various temporal and spatial scales. PMID:24047132

  5. Do protic ionic liquids and water display analogous behavior in terms of Hammett acidity function?

    NASA Astrophysics Data System (ADS)

    Shukla, Shashi Kant; Kumar, Anil

    2013-04-01

    We address an issue whether the strength of carboxylic acids in water is linear with respect to that in ionic liquids. Strength of carboxylic acids in water and different PILs using Hammett function (Ho) has revealed interesting linear correlation between the Ho function for all acids in PILs and PIL-water in spite of large structural and electronic differences. These observations suggest that different structural and electronic features of PILs and water behave analogously towards Ho. This linearity in Ho functions between PILs and PIL-water systems can be used to develop predictive method to calculate Ho values.

  6. Thermodynamic Evidence for Water as a Quantum Mechanical Liquid

    E-print Network

    A. Widom; J. Swain; S. Sivasubramanian; D. Drosdoff; Y. N. Srivastava

    2015-12-10

    We consider general theoretical models of water and in particular the nature of the motions of the hydrogen nuclei. If the motion of hydrogen nuclei is classical, then the thermodynamic pressure equation of state for heavy water wherein the hydrogen nuclei are deuterons is identical to the pressure equation of state for light water wherein the hydrogen nuclei are protons. Since the experimental thermodynamic phase diagram for light water is clearly measurably different from the experimental thermodynamic phase diagram for heavy water, one may deduce that the motions of hydrogen nuclei are quantum mechanical in nature. This conclusion is in physical agreement with a recent analysis of X-ray, neutron and deep inelastic neutron scattering data.

  7. A supramolecular structure insight for conversion property of cellulose in hot compressed water: Polymorphs and hydrogen bonds changes.

    PubMed

    Wang, Yan; Lian, Jie; Wan, Jinquan; Ma, Yongwen; Zhang, Yingshi

    2015-11-20

    Waste paper samples with different cellulose supramolecular structure were treated in hot compressed water (HCW) at 375°C and 22.5MPa within 200s to evaluate the specific effect mechanism of cellulose supramolecular structure on the conversion of waste paper to reusable resource. Although the distribution of liquid products and the oligosaccharides were related to reaction time, depolymerization and decrystallization of the cellulose, the characteristics absorption peak of cellulose from FTIR analysis and crystal structure of the cellulose detected in the residues with hydrolysis rate up 96.5% indicated crystal structure was the dominant factor that affect conversion behavior of waste paper. The conversion of cellulose I? to cellulose I? or cellulose I(?+?) in HCW demonstrated that the recrystallization occurred during the decrystallization of cellulose through the rearrangement of hydrogen bonds. PMID:26344260

  8. Measurement and Estimation of Organic-Liquid/Water Interfacial Areas for Several Natural Porous Media

    SciTech Connect

    Brusseau, M.L.; Narter, M.; Schnaar, G.; Marble, J.

    2009-06-01

    The objective of this study was to quantitatively characterize the impact of porous-medium texture on interfacial area between immiscible organic liquid and water residing within natural porous media. Synchrotron X-ray microtomography was used to obtain high-resolution, three-dimensional images of solid and liquid phases in packed columns. The image data were processed to generate quantitative measurements of organic-liquid/water interfacial area and of organic-liquid blob sizes. Ten porous media, comprising a range of median grain sizes, grain-size distributions, and geochemical properties, were used to evaluate the impact of porous-medium texture on interfacial area. The results show that fluid-normalized specific interfacial area (A{sub f}) and maximum specific interfacial area (A{sub m}) correlate very well to inverse median grain diameter. These functionalities were shown to result from a linear relationship between effective organic-liquid blob diameter and median grain diameter. These results provide the basis for a simple method for estimating specific organic-liquid/water interfacial area as a function of fluid saturation for a given porous medium. The availability of a method for which the only parameter needed is the simple-to-measure median grain diameter should be of great utility for a variety of applications.

  9. An analysis of molecular packing and chemical association in liquid water using quasichemical theory

    NASA Astrophysics Data System (ADS)

    Paliwal, A.; Asthagiri, D.; Pratt, L. R.; Ashbaugh, H. S.; Paulaitis, M. E.

    2006-06-01

    We calculate the hydration free energy of liquid TIP3P water at 298K and 1bar using a quasichemical theory framework in which interactions between a distinguished water molecule and the surrounding water molecules are partitioned into chemical associations with proximal (inner-shell) waters and classical electrostatic/dispersion interactions with the remaining (outer-shell) waters. The calculated free energy is found to be independent of this partitioning, as expected, and in excellent agreement with values derived from the literature. An analysis of the spatial distribution of inner-shell water molecules as a function of the inner-shell volume reveals that water molecules are preferentially excluded from the interior of large volumes as the occupancy number decreases. The driving force for water exclusion is formulated in terms of a free energy for rearranging inner-shell water molecules under the influence of the field exerted by outer-shell waters in order to accommodate one water molecule at the center. The results indicate a balance between chemical association and molecular packing in liquid water that becomes increasingly important as the inner-shell volume grows in size.

  10. X-ray absorption spectrum of liquid water from molecular dynamics simulations: Asymmetric model

    NASA Astrophysics Data System (ADS)

    Odelius, Michael; Cavalleri, Matteo; Nilsson, Anders; Pettersson, Lars G. M.

    2006-01-01

    We address the question of the local structure in liquid water by computing the x-ray absorption (XA) spectrum explicitly averaging over configurations from classical and Car-Parrinello molecular dynamics (MD) simulations. We confirm the prediction by Wernet [Science 304, 995 (2004)] that the resulting spectra are not representative for liquid water due to a too large fraction of molecules with two donating hydrogen bonds. The H-bond criterion given by Wernet is, however, not sufficient to predict the XA spectrum for general structures from MD simulations. Only by selecting specific single-donor MD configurations is it possible to represent the liquid water spectrum; this results in an improved and more restrictive geometrical connection between local structure and spectral features in the simulation. The configurations, with one strong and one weak donating hydrogen bond, need to be even more asymmetric than previously assumed. This bonding situation is strongly underrepresented in the simulations.

  11. Structure and Dynamics of Low-Density and High-Density Liquid Water at High Pressure.

    PubMed

    Fanetti, Samuele; Lapini, Andrea; Pagliai, Marco; Citroni, Margherita; Di Donato, Mariangela; Scandolo, Sandro; Righini, Roberto; Bini, Roberto

    2014-01-01

    Liquid water has a primary role in ruling life on Earth in a wide temperature and pressure range as well as a plethora of chemical, physical, geological, and environmental processes. Nevertheless, a full understanding of its dynamical and structural properties is still lacking. Water molecules are associated through hydrogen bonds, with the resulting extended network characterized by a local tetrahedral arrangement. Two different local structures of the liquid, called low-density (LDW) and high-density (HDW) water, have been identified to potentially affect many different chemical, biological, and physical processes. By combining diamond anvil cell technology, ultrafast pump-probe infrared spectroscopy, and classical molecular dynamics simulations, we show that the liquid structure and orientational dynamics are intimately connected, identifying the P-T range of the LDW and HDW regimes. The latter are defined in terms of the speeding up of the orientational dynamics, caused by the increasing probability of breaking and reforming the hydrogen bonds. PMID:26276206

  12. Short-range precipitation forecasts using assimilation of simulated satellite water vapor profiles and column cloud liquid water amounts

    NASA Technical Reports Server (NTRS)

    Wu, Xiaohua; Diak, George R.; Hayden, Cristopher M.; Young, John A.

    1995-01-01

    These observing system simulation experiments investigate the assimilation of satellite-observed water vapor and cloud liquid water data in the initialization of a limited-area primitive equations model with the goal of improving short-range precipitation forecasts. The assimilation procedure presented includes two aspects: specification of an initial cloud liquid water vertical distribution and diabatic initialization. The satellite data is simulated for the next generation of polar-orbiting satellite instruments, the Advanced Microwave Sounding Unit (AMSU) and the High-Resolution Infrared Sounder (HIRS), which are scheduled to be launched on the NOAA-K satellite in the mid-1990s. Based on cloud-top height and total column cloud liquid water amounts simulated for satellite data a diagnostic method is used to specify an initial cloud water vertical distribution and to modify the initial moisture distribution in cloudy areas. Using a diabatic initialization procedure, the associated latent heating profiles are directly assimilated into the numerical model. The initial heating is estimated by time averaging the latent heat release from convective and large-scale condensation during the early forecast stage after insertion of satellite-observed temperature, water vapor, and cloud water formation. The assimilation of satellite-observed moisture and cloud water, together withy three-mode diabatic initialization, significantly alleviates the model precipitation spinup problem, especially in the first 3 h of the forecast. Experimental forecasts indicate that the impact of satellite-observed temperature and water vapor profiles and cloud water alone in the initialization procedure shortens the spinup time for precipitation rates by 1-2 h and for regeneration of the areal coverage by 3 h. The diabatic initialization further reduces the precipitation spinup time (compared to adiabatic initialization) by 1 h.

  13. Formation of Martian Gullies by the Action of Liquid Water Flowing Under Current Martian Environmental Conditions

    NASA Technical Reports Server (NTRS)

    Heldmann, J. L.; Toon, O. B.; Pollard, W. H.; Mellon, M. T.; Pitlick, J.; McKay, C. P.; Andersen, D. T.

    2005-01-01

    Images from the Mars Orbiter Camera (MOC) on the Mars Global Surveyor (MGS) spacecraft show geologically young small-scale features resembling terrestrial water-carved gullies. An improved understanding of these features has the potential to reveal important information about the hydrological system on Mars, which is of general interest to the planetary science community as well as the field of astrobiology and the search for life on Mars. The young geologic age of these gullies is often thought to be a paradox because liquid water is unstable at the Martian surface. Current temperatures and pressures are generally below the triple point of water (273 K, 6.1 mbar) so that liquid water will spontaneously boil and/or freeze. We therefore examine the flow of water on Mars to determine what conditions are consistent with the observed features of the gullies.

  14. Dual spectrum neutron radiography: identification of phase transitions between frozen and liquid water.

    PubMed

    Biesdorf, J; Oberholzer, P; Bernauer, F; Kaestner, A; Vontobel, P; Lehmann, E H; Schmidt, T J; Boillat, P

    2014-06-20

    In this Letter, a new approach to distinguish liquid water and ice based on dual spectrum neutron radiography is presented. The distinction is based on arising differences between the cross section of water and ice in the cold energy range. As a significant portion of the energy spectrum of the ICON beam line at Paul Scherrer Institut is in the thermal energy range, no differences can be observed with the entire beam. Introducing a polycrystalline neutron filter (beryllium) inside the beam, neutrons above its cutoff energy are filtered out and the cold energy region is emphasized. Finally, a contrast of about 1.6% is obtained with our imaging setup between liquid water and ice. Based on this measurement concept, the temporal evolution of the aggregate state of water can be investigated without any prior knowledge of its thickness. Using this technique, we could unambiguously prove the production of supercooled water inside fuel cells with a direct measurement method. PMID:24996112

  15. Liquid water: A very complex fluid H EUGENE STANLEY

    E-print Network

    Stanley, H. Eugene

    -induced melting and decompression-induced melting lines of high-pressure forms of ice. We show how knowledge connected to the view that water, even above its melting temperature, is a transient gel with structural

  16. A liquid water management strategy for PEM fuel cell stacks

    E-print Network

    Van Nguyen, Trung; Knobbe, M. W.

    2003-02-25

    flow field uses the flow of gas for excess water removal, a deficient flow of gas causes the cell to become flooded. To alleviate this problem of unequal gas distribution, a method of sequentially exhausting each individual cell was developed...

  17. Liquid Water: Obtaining the right answer for the right reasons

    SciTech Connect

    Apra, Edoardo; Harrison, Robert J; de Jong, Wibe A; Rendell, Alistair P; Tipparaju, Vinod; Xantheas, Sotiris

    2009-01-01

    Water is ubiquitous on our planet and plays an essential role in many chemical and biological processes. Accurate models for water are crucial in understanding, controlling and predicting the physical and chemical properties of complex aqueous systems. Over the last few years we have been developing a molecular-level based approach for a macroscopic model for water that is based on the explicit description of the underlying intermolecular interactions between molecules in water clusters. In the absence of detailed experimental data for small water clusters, highly-accurate theoretical results are required to validate and parameterize model potentials. As an example of the benchmarks needed for the development of accurate models for the interaction between water molecules, for the most stable structure of (H$_2$O)$_{20}$ we ran a coupled-cluster calculation on the ORNL's Jaguar petaflop computer that used over 100 TB of memory for a sustained performance of 487 TFLOP/s (double precision) on 96,000 processors, lasting for 2 hours. By this summer we will have studied multiple structures of both (H$_2$O)$_{20}$ and (H$_2$O)$_{30}$ and completed basis set and other convergence studies and anticipate the sustained performance rising close to 1 PFLOP/s.

  18. Liquid Water: Obtaining the right answer for the right reasons

    SciTech Connect

    Apra, Edoardo; Rendell, Alistair P.; Harrison, Robert J.; Tipparaju, Vinod; De Jong, Wibe A.; Xantheas, Sotiris S.

    2009-11-14

    Water is ubiquitous on our planet and plays an essential role in many chemical and biological processes. Accurate models for water are crucial in understanding, controlling and predicting the physical and chemical properties of complex aqueous systems. Over the last few years we have been developing a molecular-level based approach for a macroscopic model for water that is based on the explicit description of the underlying intermolecular interactions between molecules in water clusters. In the absence of detailed experimental data for small water clusters, highly-accurate theoretical results are required to validate and parameterize model potentials. As an example of the benchmarks needed for the development of accurate models for the interaction between water molecules, for the most stable structure of (H2O)20 we ran a coupled-cluster calculation on the ORNL’s Jaguar petaflop computer that used over 100 TB of memory for a sustained performance of 487 TFLOP/s (double precision) on 96,000 processors, lasting for 2 hours. By this summer we will have studied multiple structures of both (H2O)20 and (H2O)30 and completed basis set and other convergence studies and anticipate the sustained performance rising close to 1 PFLOP/s.

  19. Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

    NASA Astrophysics Data System (ADS)

    Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas

    2014-03-01

    Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA).

  20. Heating-induced glass-glass and glass-liquid transformations in computer simulations of water.

    PubMed

    Chiu, Janet; Starr, Francis W; Giovambattista, Nicolas

    2014-03-21

    Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA). PMID:24655190

  1. Heating-induced glass-glass and glass-liquid transformations in computer simulations of water

    SciTech Connect

    Chiu, Janet; Giovambattista, Nicolas; Starr, Francis W.

    2014-03-21

    Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T “phase diagram” for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA)

  2. Growth of volcanic ash aggregates in the presence of liquid water and ice: an experimental approach

    NASA Astrophysics Data System (ADS)

    Van Eaton, Alexa R.; Muirhead, James D.; Wilson, Colin J. N.; Cimarelli, Corrado

    2012-11-01

    Key processes influencing the aggregation of volcanic ash and hydrometeors are examined with an experimental method employing vibratory pan aggregation. Mechanisms of aggregation in the presence of hail and ice pellets, liquid water (?30 wt%), and mixed water phases are investigated at temperatures of 18 and -20 °C. The experimentally generated aggregates, examined in hand sample, impregnated thin sections, SEM imagery, and X-ray microtomography, closely match natural examples from phreatomagmatic phases of the 27 ka Oruanui and 2010 Eyjafjallajökull eruptions. Laser diffraction particle size analysis of parent ash and aggregates is also used to calculate the first experimentally derived aggregation coefficients that account for changing liquid water contents and subzero temperatures. These indicate that dry conditions (<5-10 wt% liquid) promote strongly size selective collection of sub-63 ?m particles into aggregates (given by aggregation coefficients >1). In contrast, liquid-saturated conditions (>15-20 wt% liquid) promote less size selective processes. Crystalline ice was also capable of preferentially selecting volcanic ash <31 ?m under liquid-free conditions in a two-stage process of electrostatic attraction followed by ice sintering. However, this did not accumulate more than a monolayer of ash at the ice surface. These quantitative relationships may be used to predict the timescales and characteristics of aggregation, such as aggregate size spectra, densities, and constituent particle size characteristics, when the initial size distribution and water content of a volcanic cloud are known. The presence of an irregularly shaped, millimeter-scale vacuole at the center of natural aggregates was also replicated during interaction of ash and melting ice pellets, followed by sublimation. Fine-grained rims were formed by adding moist aggregates to a dry mixture of sub-31 ?m ash, which adhered by electrostatic forces and sparse liquid bridges. From this, we infer that the fine-grained outer layers of natural aggregates reflect recycled exposure of moist aggregates to regions of volcanic clouds that are relatively dry and dominated by <31 ?m ash.

  3. Associations between the polymorphisms of GSTT1, GSTM1 and methylation of arsenic in the residents exposed to low-level arsenic in drinking water in China.

    PubMed

    Yang, Jinyou; Yan, Li; Zhang, Min; Wang, Yijun; Wang, Chun; Xiang, Quanyong

    2015-07-01

    We carry out a study to analyze the relation between polymorphisms of GSTT1, GSTM1 and the capacity of arsenic methylation in a human population exposed to arsenic in drinking water. 230 randomly chose subjects were divided into four subgroups based on the arsenic levels, and then the associations between the polymorphisms of GSTT1, GSTM1 and methylation of arsenic were investigated. The levels of inorganic arsenic (iAs), monomethylated arsenic (MMA), dimethylated arsenic (DMA) and total arsenic (TAs) in urine were higher in males than that in females. Moreover, the levels of iAs and TAs in urine in the subjects with genotype of GSTM1(+) were significantly higher than those with GSTM1(-); the level of DMA in the subjects with GSTT1(+) and GSTM1(+) were higher than those with GSTT1(-) and GSTM1(-), although it is not statistically significant. Secondary methylation index (SMI) was significantly higher in the subjects with genotype of GSTT1(+) than those with GSTT1(-). The levels of TAs in urine, together with the genotypes of GSTT1/GSTM1 were associated with the levels of MMA and DMA. Our results suggested that the polymorphisms of GSTT1 and GSTM1 were associated with the methylation of arsenic, especially the levels of DMA and SMI. PMID:25876999

  4. Point observations of liquid water content in wet snow - investigating methodical, spatial and temporal aspects

    NASA Astrophysics Data System (ADS)

    Techel, F.; Pielmeier, C.

    2011-05-01

    Information about the volume and the spatial and temporal distribution of liquid water in snow is important for forecasting wet snow avalanches and for predicting melt-water run-off. The distribution of liquid water in snow is commonly estimated from point measurements using a "hand" squeeze test, or a dielectric device such as a "Snow Fork" or a "Denoth meter". Here we compare estimates of water content in the Swiss Alps made using the hand test to those made with a Snow Fork and a Denoth meter. Measurements were conducted in the Swiss Alps, mostly above tree line; more than 12 000 measurements were made at 85 locations over 30 days. Results show that the hand test generally over estimates the volumetric liquid water content. Estimates using the Snow Fork are generally 1 % higher than those derived from the Denoth meter. The measurements were also used to investigate temporal and small-scale spatial patterns of wetness. Results show that typically a single point measurement does not characterize the wetness of the surrounding snow. Large diurnal changes in wetness are common in the near-surface snow, and associated changes at depth were also observed. A single vertical profile of measurements is not sufficient to determine whether these changes were a result of a spatially homogeneous wetting front or caused by infiltration through pipes. Based on our observations, we suggest that three measurements at horizontal distances greater than 50 cm are needed to adequately characterize the distribution of liquid water through a snowpack. Further, we suggest a simplified classification scheme that includes five wetness patterns that incorporate both the vertical and horizontal distribution of liquid water in a snowpack.

  5. Vapor-liquid equilibria of the water + 1,3-propanediol and water + 1,3-propanediol + lithium bromide systems

    SciTech Connect

    Mun, S.Y.; Lee, H.

    1999-12-01

    Vapor-liquid equilibrium data of the water + 1,3-propanediol and water + 1,3-propanediol + lithium bromide systems were measured at 60, 160, 300, and 760 mmHg at temperatures ranging from 315 to 488 K. The apparatus used in this work is a modified still especially designed for the measurement of low-pressure VLE, in which both liquid and vapor are continuously recirculated. For the analysis of salt-containing solutions, a method incorporating refractometry and gravimetry was used. From the experimental measurements, the effect of lithium bromide on the VLE behavior of water + 1,3-propanediol was investigated. The experimental data of the salt-free system were successfully correlated using the Wilson, NRTL, and UNIQUAC models. In addition, the extended UNIQUAC model of Sander et al. was applied to the VLE calculation of salt-containing mixtures.

  6. On the existence and stability of liquid water on the surface of mars today

    NASA Technical Reports Server (NTRS)

    Kuznetz, L. H.; Gan, D. C.

    2002-01-01

    The recent discovery of high concentrations of hydrogen just below the surface of Mars' polar regions by Mars Odyssey has enlivened the debate about past or present life on Mars. The prevailing assumption prior to the discovery was that the liquid water essential for its existence is absent. That assumption was based largely on the calculation of heat and mass transfer coefficients or theoretical climate models. This research uses an experimental approach to determine the feasibility of liquid water under martian conditions, setting the stage for a more empirical approach to the question of life on Mars. Experiments were conducted in three parts: Liquid water's existence was confirmed by droplets observed under martian conditions in part 1; the evolution of frost melting on the surface of various rocks under martian conditions was observed in part 2; and the evaporation rate of water in Petri dishes under Mars-like conditions was determined and compared with the theoretical predictions of various investigators in part 3. The results led to the conclusion that liquid water can be stable for extended periods of time on the martian surface under present-day conditions.

  7. Remote sensing of total integrated water vapor, wind speed, and cloud liquid water over the ocean using the Special Sensor Microwave/Imager (SSM/I) 

    E-print Network

    Manning, Norman Willis William

    1997-01-01

    A modified D-matrix retrieval method is the basis of the refined total integrated water vapor (TIWV), total integrated cloud liquid water (CLW), and surface wind speed (WS) retrieval methods that are developed. The 85 GHZ polarization difference...

  8. Rheological properties of ammonia-water liquids and crystal-liquid slurries - Planetological applications

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.; Croft, S. K.; Lunine, J. I.; Lewis, J. S.

    1991-01-01

    The laboratory-measured viscosities of liquid mixtures representative of the variety of cryovolcanic substances of the icy satellites are presently noted to be much greater than could be expected on the assumption that end-member molecules are noninteractive; this observation is supported by others concerning molar volumes and vapor pressure relations, which indicate the presence of strong molecular-interaction forces that fundamentally affect the mixtures' physical properties. Since the rheological effects of partial crystallization parallel the characteristics of silicate lavas, icy satellite cryovolcanic morphologies are similarly interpretable with allowances for differences in surface gravities and lava densities.

  9. Monitoring of copper level in water and soil samples by using liquid-liquid extraction.

    PubMed

    Shrivas, Kamlesh

    2010-09-01

    A new, simple, sensitive, and selective spectrophotometric method for the determination of copper in water and soil samples has been demonstrated. The method is based on the reaction of Cu(I) with neocuproine (2,9-dimethyl-1, 10-phenanothroline) and extracted with N-phenyl benzimidoylthiourea in chloroform. The value of molar absorptivity of the complex in the term of Cu(I) is 1.45 x 10(5) L mol(-1)cm(-1) at lambda(max) 460 nm in chloroform. The detection limit of copper in water and soil is 2 ng mL(-1) and 4 ng g(-1), respectively. The method is free from the interference of the ions commonly found to be associated with the copper determination in water and soil samples. The application of the proposed method has been successfully tested for the determination of copper in different types of water and soil samples. PMID:19685273

  10. Point observations of liquid water content in natural snow - investigating methodical, spatial and temporal aspects

    NASA Astrophysics Data System (ADS)

    Techel, F.; Pielmeier, C.

    2010-10-01

    Information on the amount and distribution of liquid water in the snowpack is important for forecasting wet snow avalanches and predicting melt-water run-off. Considerable spatial and temporal variations of snowpack wetness exist. Currently, available information relies mostly on point observations. Often, the snow wetness is estimated manually using a hand test. However, quantitative measures are also applied. We compare the hand test to quantitative measurements and investigate temporal and small-scale spatial aspects of the snowpack wetness. For this, the liquid water content was measured using dielectric methods, with the Snow Fork and Denoth wetness instrument in the Swiss Alps, mostly above tree-line. More than 12 000 water content measurements were observed on 30 days in 85 locations. The qualitative hand test provides an indication of snowpack wetness, although snowpack wetness is often over-estimated and quantitative water content measurements are more reliable. If the measured water content is very low, it is unclear if the snow is dry or contains small quantities of liquid water. In particular during the initial melt-phase, when the snowpack is only partially wet, it is important to consider spatial aspects when interpreting point observations. One measurement taken at a certain measurement depth may significantly deviate in 10-20% of the cases from snowpack wetness in the surrounding snow. Not surprisingly, diurnal changes in snowpack wetness are significant in layers close to the snow surface. At depth, changes were noted within the course of a day. From a single vertical profile, it was often unclear if these changes were due to the heterogeneous nature of water infiltration. Based on our observations, we propose to repeat three measurements at horizontal distances greater than 50 cm. This approach provides representative snow wetness information for horizontal distances up to 5 m. Further, we suggest a simplified classification scheme of snowpack wetness by introducing five wetness types of the snowpack incorporating both vertical and horizontal liquid water content distribution.

  11. Microscopic origin of temporal heterogeneities in translational dynamics of liquid water

    NASA Astrophysics Data System (ADS)

    Mukherjee, Biswaroop

    2015-08-01

    Liquid water is known to reorient via a combination of large angular jumps (due to exchange of hydrogen bonding (H-bond) partners) and diffusive orientations. Translation of the molecule undergoing the orientational jump and its initial and final H-bond acceptors plays a key role in the microscopic reorientation process. Here, we partition the translational dynamics into those occurring during intervals when rotating water molecules (and their initial and final H-bonding partners) undergo orientational jump and those arising when molecules wait between consecutive orientational jumps. These intervals are chosen in such a way that none of the four possible H-bonds involving the chosen water molecule undergo an exchange process within its duration. Translational dynamics is analysed in terms of the distribution of particle displacements, van Hove functions, and its moments. We observe that the translational dynamics, calculated from molecular dynamics simulations of liquid water, is fastest during the orientational jumps and slowest during periods of waiting. The translational dynamics during all temporal intervals shows an intermediate behaviour. This is the microscopic origin of temporal dynamic heterogeneity in liquid water, which is mild at 300 K and systematically increases with supercooling. Study of such partitioned dynamics in supercooled water shows increased disparity in dynamics occurring in the two different types of intervals. Nature of the distribution of particle displacements in supercooled water is investigated and it reveals signatures non-Gaussian behaviour.

  12. Effect of simple solutes on the long range dipolar correlations in liquid water

    E-print Network

    Upayan Baul; J. Maruthi Pradeep Kanth; Ramesh Anishetty; Satyavani Vemparala

    2015-12-07

    Intermolecular correlations in liquid water at ambient conditions have generally been characterized through short range density fluctuations described through the atomic pair distribution functions (PDF). Recent numerical and experimental results have suggested that such a description of order or structure in liquid water is incomplete and there exists considerably longer ranged orientational correlations in water that can be studied through dipolar correlations. In this study, using large scale classical, atomistic molecular dynamics (MD) simulations using TIP4P-Ew and TIP3P models of water, we show that salts such as sodium chloride (NaCl), potassium chloride (KCl), caesium chloride (CsCl) and magnesium chloride (MgCl$_2$) have a long range effect on the dipolar correlations, which can not be explained by the notion of structure making and breaking by dissolved ions. The relative effects of cations on dipolar correlations are observed to be consistent with the well-known Hofmeister series. Observed effects are explained through orientational stratification of water molecules around ions, and their long range coupling to the global hydrogen bond network by virtue of the sum rule for water. The observations for single hydrophilic solutes are contrasted with the same for a single methane (CH$_4$) molecule. We observe that even a single small hydrophobe can result in enhancement of long range orientational correlations in liquid water,- contrary to the case of dissolved ions, which have been observed to have a reducing effect. The observations from this study are discussed in the context of hydrophobic effect.

  13. Application of dispersive liquid-liquid microextraction and high-performance liquid chromatography for the determination of three phthalate esters in water samples.

    PubMed

    Liang, Pei; Xu, Jing; Li, Qian

    2008-02-18

    A novel method, dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography-variable wavelength detector (HPLC-VWD), has been developed for the determination of three phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP)) in water samples. A mixture of extraction solvent (41 microL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) were rapidly injected into 5.0 mL aqueous sample for the formation of cloudy solution, the analytes in the sample were extracted into the fine droplets of CCl4. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by HPLC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 5 to 5000 ng mL(-1) for target analytes. The enrichment factors for DMP, DEP and DnBP were 45, 92 and 196, respectively, and the limits of detection were 1.8, 0.88 and 0.64 ng mL(-1), respectively. The relative standard deviations (R.S.D.) for the extraction of 10 ng mL(-1) of phthalate esters were in the range of 4.3-5.9% (n=7). Lake water, tap water and bottled mineral water samples were successfully analyzed using the proposed method. PMID:18243873

  14. Comment on "Structure and dynamics of liquid water on rutile TiO2(110)

    SciTech Connect

    Wesolowski, David J; Sofo, Jorge O.; Bandura, Andrei V.; Zhang, Zhan; Mamontov, Eugene; Predota, M.; Kumar, Nitin; Kubicki, James D.; Kent, Paul R; Vlcek, Lukas; Machesky, Michael L.; Fenter, Paul; Cummings, Peter T; Anovitz, Lawrence {Larry} M; Skelton, A A; Rosenqvist, Jorgen K

    2012-01-01

    Liu and co-workers [Phys. Rev. B 82, 161415 (2010)] discussed the long-standing debate regarding whether H2O molecules on the defect-free (110) surface of rutile ( -TiO2) sorb associatively, or there is dissociation of some or all first-layer water to produce hydroxyl surface sites. They conducted static density functional theory (DFT) and DFT molecular dynamics (DFT-MD) investigations using a range of cell configurations and functionals. We have reproduced their static DFT calculations of the influence of crystal slab thickness on water sorption energies. However, we disagree with several assertions made by these authors: (a) that second-layer water structuring and hydrogen bonding to surface oxygens and adsorbed water molecules are weak ; (b) that translational diffusion of water molecules in direct contact with the surface approaches that of bulk liquid water; and (c) that there is no dissociation of adsorbed water at this surface in contact with liquid water. These assertions directly contradict our publishedwork, which compared synchrotron x-ray crystal truncation rod, second harmonic generation, quasielastic neutron scattering, surface charge titration, and classical MD simulations of rutile (110) single-crystal surfaces and (110)-dominated powders in contact with bulk water, and (110)-dominated rutile nanoparticles with several monolayers of adsorbed water.

  15. Measurement of Rn-222 in water by absorption in polycarbonates and liquid scintillation counting

    NASA Astrophysics Data System (ADS)

    Mitev, K.; Dimitrova, I.; Zhivkova, V.; Georgiev, S.; Gerganov, G.; Pressyanov, D.; Boshkova, T.

    2012-06-01

    This work presents a new technique for measurement of activity concentrations of Rn-222 in water which is based on liquid scintillation counting (LSC) of polycarbonates exposed in the water. The polycarbonate material has high absorption ability to radon and when exposed in a radon-containing environment (air or water), it absorbs and concentrates radon in its volume. This property of the polycarbonate material is used for sampling 222Rn from the water. The main new element in this work is that it proposes the LSC technique for measurement of the radiation, emitted from the polycarbonate material. This radiation is due to the decay of the absorbed 222Rn and its progeny. Experimental results of LSC of polycarbonate granules and thin foils exposed in water with different activity concentrations of Rn-222 are presented. In all cases a very good linear correlation between the LS counting rate and the activity concentration of the water is found. The LSC of polycarbonates shows similar or even higher sensitivity in comparison to that of LSC of water. The estimated radon-in-water minimal detectable activity concentrations of the proposed method are similar or lower than those of the LSC and lower than those obtained by gamma spectrometry. The proposed method is simple, robust, inexpensive and avoids the need of taking water samples for laboratory analysis. It facilitates studies of the spatial distribution of 222Rn in water basins by exposure of polycarbonate specimens at different spots or depths and subsequent liquid scintillation counting.

  16. Experimental determination of cavitation thresholds in liquid water and mercury

    SciTech Connect

    Taleyarkhan, R.P.; West, C.D.; Moraga, F.

    1998-11-01

    An overview is provided on cavitation threshold measurement experiments for water and mercury. Various aspects to be considered that affect onset determination are discussed along with design specifications developed for construction of appropriate apparatus types. Both static and transient-cavitation effects were studied using radically different apparatus designs. Preliminary data are presented for cavitation thresholds for water and mercury over a range of temperatures in static and high-frequency environments. Implications and issues related to spallation neutron source target designs and operation are discussed.

  17. Estimating the lunar mantle water budget from phosphates: Complications associated with silicate-liquid-immiscibility

    NASA Astrophysics Data System (ADS)

    Pernet-Fisher, J. F.; Howarth, G. H.; Liu, Y.; Chen, Y.; Taylor, L. A.

    2014-11-01

    The discovery of water within the lunar mantle has broad implications for the formation of the Earth-Moon system, differentiation of the Moon, and the magmatic evolution of lunar basalts, as well as the highland rocks. Recently, there has been considerable interest in using combined water abundances and H-isotope systematics of lunar apatites from mare basalts to quantify the origin and extent of water within the Moon's mantle. However, the petrologic and geochemical conditions that govern apatite crystallization are not well-constrained, especially for high-FeO basaltic melts that crystallize at fO2 values below the iron-wüstite buffer. Apatites are typically located within the late-stage interstitial regions. In this contribution, we present detailed textural descriptions of late-stage inter-cumulus, residual-liquid pockets (i.e., mesostasis pockets), in order to understand the petrogenesis of lunar apatite. Results from five mare basalts demonstrate that the majority of the residual liquids in mesostasis regions have undergone silicate-liquid immiscibility (SLI) splitting into Si-K-rich (felsic) and Fe-rich (Fe-basaltic) conjugate liquids. We demonstrate the complexity of these residual liquids by documenting a wide range of water contents for apatites in several mesostasis pockets within a single mare basalt, a complexity common to many basalts. These data illustrate that individual apatite-hosting mesostasis pockets behave as independent sub-systems, even within a single rock. Furthermore, we present water concentrations for another phosphate phase, merrillite, indicating additional uncertainties during considerations of water partitioning into apatite. Fractional crystallization trends have been used in order to assess the conditions under which magmas are likely to undergo SLI. Predicted liquid lines of descent indicate that it is the late-stage residual liquids of lunar basalts with relatively low-Mg# (e.g., liquid field during crystallization, forming conjugate liquids that are chemically and mineralogically distinct. However, residual liquids for basaltic magmas with high-Mg# (e.g., >?50) may not intersect the two-liquid field depending upon the fractionation trends in the late-stage mesostasis pockets. For samples that undergo SLI, the apatite/melt-partition coefficients required for back-calculating water abundances of the parental melts are compromised by the generation of two populations of apatites-merrillites from conjugate immiscible liquids. This process highlights an important complexity inherent to all water back-calculations that use apatite, as this requires an additional set of partition coefficients. We emphasize that the complex petrologic nature and common development of SLI of apatite-bearing, late-stage mesostasis pockets have not been considered in published apatite-volatile data. These factors, in additional to other considerations, illustrate why water back-calculations to model the primary melts from such data must be viewed with caution.

  18. Investigation of Uranium Polymorphs

    SciTech Connect

    Sweet, Lucas E.; Henager, Charles H.; Hu, Shenyang Y.; Johnson, Timothy J.; Meier, David E.; Peper, Shane M.; Schwantes, Jon M.

    2011-08-01

    The UO3-water system is complex and has not been fully characterized, even though these species are common throughout the nuclear fuel cycle. As an example, most production schemes for UO3 result in a mixture of up to six or more different polymorphic phases, and small differences in these conditions will affect phase genesis that ultimately result in measureable changes to the end product. As a result, this feature of the UO3-water system may be useful as a means for determining process history. This research effort attempts to better characterize the UO3-water system with a variety of optical techniques for the purpose of developing some predictive capability for estimating process history in polymorphic phases of unknown origin. Three commercially relevant preparation methods for the production of UO3 were explored. Previously unreported low temperature routes to ?- and ?-UO3 were discovered. Raman and fluorescence spectroscopic libraries were established for pure and mixed polymorphic forms of UO3 in addition to the common hydrolysis products of UO3. An advantage of the sensitivity of optical fluorescence microscopy over XRD has been demonstrated. Preliminary aging studies of the ? and ? forms of UO3 have been conducted. In addition, development of a 3-D phase field model used to predict phase genesis of the system was initiated. Thermodynamic and structural constants that will feed the model have been gathered from the literature for most of the UO3 polymorphic phases.

  19. Nuclear quantum effects in liquid water from path-integral simulations using an ab initio force matching approach

    E-print Network

    Thomas Spura; Christopher John; Scott Habershon; Thomas D. Kühne

    2014-02-12

    We have applied path integral simulations, in combination with new ab initio based water potentials, to investigate nuclear quantum effects in liquid water. Because direct ab initio path integral simulations are computationally expensive, a flexible water model is parameterized by force-matching to density functional theory-based molecular dynamics simulations. The resulting effective potentials provide an inexpensive replacement for direct ab inito molecular dynamics simulations and allow efficient simulation of nuclear quantum effects. Static and dynamic properties of liquid water at ambient conditions are presented and the role of nuclear quantum effects, exchange-correlation functionals and dispersion corrections are discussed in regards to reproducing the experimental properties of liquid water.

  20. Water coordination structures and the excess free energy of the liquid

    E-print Network

    Merchant, Safir; Asthagiri, D

    2011-01-01

    For a distinguished water molecule, the solute water, we assess the contribution of each coordination state to its excess chemical potential, using a molecular aufbau approach. In this approach, we define a coordination sphere, the inner-shell, and separate the excess chemical potential into packing, outer-shell, and local chemical contributions; the coordination state is defined by the number of solvent water molecules within the coordination sphere. The packing term accounts for the free energy of creating a solute-free coordination sphere in the liquid. The outer-shell term accounts for the interaction of the solute with the fluid outside the coordination sphere and it is accurately described by a Gaussian model of hydration for coordination radii greater than the minimum of the oxygen-oxygen pair correlation function. Consistent with the conventional radial cut-off used for defining hydrogen-bonds in liquid water, theory helps identify a chemically meaningful coordination radius. The local chemical contri...

  1. Hydrogen bonds in liquid water are broken only fleetingly

    E-print Network

    Geissler, Phillip

    -bonded frequencies on the time scale of water's fastest intermolecular motions. Simulations of an atomistic model are tetrahedrally coordinated but appear to engage in 10% fewer hydrogen bonds than in ice. Support for this estimate comes broadly, from latent heats of melting and vaporization, from x-ray and neutron scattering

  2. Thermal signature reduction through liquid nitrogen and water injection 

    E-print Network

    Guarnieri, Jason Antonio

    2005-02-17

    to the flow rate of exhaust gases, producing a small temperature reduction in the exhaust but no infrared shielding. Second, water was injected at a flow rate of 13% of the flow of exhaust gases, producing a greater temperature reduction and some shielding...

  3. The Protein-Water Energy Seascape Protein molecules and liquid water are very different systems both

    E-print Network

    Doster, Wolfgang

    -range ordered, but long range diffusion allows it to flow, the essence of the liquid state. The energy landscape the properties of both systems. The protein landscape is modulated in time by density fluctuations in the liquid can be super- cooled until a glass transition interferes at 170 K. In such hydrated protein powders

  4. Proton transfer in liquid water confined inside graphene slabs

    NASA Astrophysics Data System (ADS)

    Tahat, Amani; Martí, Jordi

    2015-09-01

    The microscopic structure and dynamics of an excess proton in water constrained in narrow graphene slabs between 0.7 and 3.1 nm wide has been studied by means of a series of molecular dynamics simulations. Interaction of water and carbon with the proton species was modeled using a multistate empirical valence bond Hamiltonian model. The analysis of the effects of confinement on proton solvation structure and on its dynamical properties has been considered for varying densities. The system is organized in one interfacial and a bulk-like region, both of variable size. In the widest interplate separations, the lone proton shows a marked tendency to place itself in the bulk phase of the system, due to the repulsive interaction with the carbon atoms. However, as the system is compressed and the proton is forced to move to the vicinity of graphene walls it moves closer to the interface, producing a neat enhancement of the local structure. We found a marked slowdown of proton transfer when the separation of the two graphene plates is reduced. In the case of lowest distances between graphene plates (0.7 and 0.9 nm), only one or two water layers persist and the two-dimensional character of water structure becomes evident. By means of spectroscopical analysis, we observed the persistence of Zundel and Eigen structures in all cases, although at low interplate separations a signature frequency band around 2500 cm-1 suffers a blue shift and moves to characteristic values of asymmetric hydronium ion vibrations, indicating some unstability of the typical Zundel-Eigen moieties and their eventual conversion to a single hydronium species solvated by water.

  5. Determination of pentachlorophenol in water and aquifer sediments by high-performance liquid chromatography

    USGS Publications Warehouse

    Goerlitz, D.F.

    1981-01-01

    Methods for the determination of pentachlorophenol (PCP) in water and aquifer sediments are presented. Reverse-phase high-performance liquid chromotography employing ion suppression and gradient elution is used. PCP can be determined directly in water at a lower limit of detection Of 0.2 micrograms per liter. For extracts of sediment, PCP can be determined to a lower limit of 1.0 micrograms per kilogram.

  6. Interaction of a Long Alkyl Chain Protic Ionic Liquid and Water

    E-print Network

    Bodo, Enrico; Capitani, Francesco; Gontrani, Lorenzo; Leonelli, Francesca; Postorino, Paolo

    2014-01-01

    A combined experimental/theoretical approach has been used to investigate the role of water in modifying the microscopic interactions characterizing the optical response of butyl-ammonium nitrate (BAN) water solutions. Raman spectra, dominated by the signal from the protic ionic liquid, were collected as a function of the water content, and the corresponding spatial organization of the ionic couples, as well as their local arrangement with water molecules, was studied exploiting classical molecular dynamics calculations. High quality spectroscopic data, combined with a careful analysis, revealed that water affects the vibrational spectrum BAN in solution: as the water concentration is increased, peaks assigned to stretching modes show a frequency hardening together with a shape narrowing, whereas the opposite behavior is observed for peaks assigned to bending modes. Calculation results clearly show a nanometric spatial organization of the ionic couples that is not destroyed on increasing the water content at ...

  7. Communication: The Effect of Dispersion Corrections on the Melting Temperature of Liquid Water

    SciTech Connect

    Yoo, Soohaeng; Xantheas, Sotiris S.

    2011-03-28

    We report the results of the melting temperature (Tm) of liquid water for the Becke-Lee- Yang-Parr (BLYP) density functional including Dispersion corrections (BLYP-D) and the TTM3-F ab-initio based classical potential via constant pressure and constant enthalpy (NPH) ensemble molecular dynamics simulations of an ice Ih-liquid coexisting system. The inclusion of dispersion corrections to BLYP lowers the melting temperature of liquid water to Tm=360 K, which is a large improvement over the value of Tm > 400 K obtained with the original BLYP functional. The ab-initio based flexible, polarizable Thole-type model (TTM3-F) produces Tm=248 K from classical molecular dynamics simulations.

  8. Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data

    NASA Astrophysics Data System (ADS)

    Keihm, S.; Brown, S.; Teixeira, J.; Desai, S.; Lu, W.; Fetzer, E.; Ruf, C.; Huang, X.; Yung, Y.

    2009-09-01

    The continuous 1992-2005 data set of the TOPEX Microwave Radiometer (TMR) has been reprocessed to provide global, zonal, and regional scale histories of overocean integrated water vapor (IWV) and cloud liquid water (CLW). Results indicate well-defined trends in IWV on global and hemisphere scales, with values of 1.8 ± 0.4%/decade (60°S-60°N), 2.4 ± 0.4%/decade (0-60°N), and 1.0 ± 0.5%/decade (0-60°S). The uncertainties represent 1 standard deviation of the regressed slope parameter adjusted for lag 1 autocorrelation. These results are comparable to earlier results based on analyses of the multiinstrument SSM/I ocean measurements beginning in 1988. For the 1992-2005 interval, comparisons between SSM/I- and TMR-derived IWV trends show remarkable agreement, with global trends differing by less than 0.3%/decade, comparable to the statistical uncertainty level and about one-sixth of the global TMR-derived trend. Latitudinal and regional analyses of IWV trends show large variability about the global mean, with synoptic scale variations of IWV trends ranging from ˜-8 to +8%/decade. Averaged over 5° latitude bands the IWV trends reveal a near zero minimum in the Southern Tropical Pacific and maximum values of ˜4%/decade over the 30-40N latitude band. Comparisons with band latitude averaged SST data over the same 1992-2005 interval roughly match a delta_IWV/delta_SST trend scaling of ˜11%/K, consistent with previously observed tropical and midlatitude seasonal variability. TMR-derived CLW trends are fractionally comparable to the IWV trends. The CLW values are 1.5 ± 0.6%/decade (60°S-60°N), 2.0 ± 0.8%/decade (0-60°N), and 1.1 ± 0.8%/decade (0-60°S). When scaled to global mean CLW derived from SSM/I and compared seasonally, the TMR CLW variations exhibit excellent tracking with the SSM/I results. Unlike IWV, however, the CLW statistical uncertainties do not likely reflect the dominant error component in the retrieved trends. The 1992-2005 CLW trend estimates were particularly sensitive to short-term trends in the first and last 2 years of the TMR archive. Additional errors difficult to quantify include strong aliasing effects from precipitation cells and uncertainties in the radiative transfer models utilized in the generation of the TMR CLW algorithm.

  9. Simulations of the effects of water vapor, cloud liquid water, and ice on AMSU moisture channel brightness temperatures

    NASA Technical Reports Server (NTRS)

    Muller, Bradley M.; Fuelberg, Henry E.; Xiang, Xuwu

    1994-01-01

    Radiative transfer simulations are performed to determine how water vapor and nonprecipitating cloud liquid water and ice particles within typical midlatitude atmospheres affect brightness temperatures T(sub B)'s of moisture sounding channels used in the Advanced Microwave Sounding Unit (AMSU) and AMSU-like instruments. The purpose is to promote a general understanding of passive top-of-atmosphere T(sub B)'s for window frequencies at 23.8, 89.0, and 157.0 GHz, and water vapor frequencies at 176.31, 180.31, and 182.31 GHz by documenting specific examples. This is accomplished through detailed analyses of T(sub B)'s for idealized atmospheres, mostly representing temperate conditions over land. Cloud effects are considered in terms of five basic properties: droplet size distribution, phase, liquid or ice water content, altitude, and thickness. Effects on T(sub B) of changing surface emissivity also are addressed. The brightness temperature contribution functions are presented as an aid to physically interpreting AMSU T(sub B)'s. Both liquid and ice clouds impact the T(sub B)'s in a variety of ways. The T(sub B)'s at 23.8 and 89 GHz are more strongly affected by altostratus liquid clouds than by cirrus clouds for equivalent water paths. In contrast, channels near 157 and 183 GHz are more strongly affected by ice clouds. Higher clouds have a greater impact on 157- and 183-GHz T(sub B)'s than do lower clouds. Clouds depress T(sub B)'s of the higher-frequency channels by suppressing, but not necessarily obscuring, radiance contributions from below. Thus, T(sub B)'s are less closely associated with cloud-top temperatures than are IR radiometric temperatures. Water vapor alone accounts for up to 89% of the total attenuation by a midtropospheric liquid cloud for channels near 183 GHz. The Rayleigh approximation is found to be adequate for typical droplet size distributions; however, Mie scattering effects from liquid droplets become important for droplet size distribution functions with modal radii greater than 20 micrometers near 157 and 183 GHz, and greater than 30-40 micrometers at 89 GHz. This is due mainly to the relatively small concentrations of droplets much larger than the mode radius. Orographic clouds and tropical cumuli have been observed to contain droplet size distributions with mode radii in the 30-40 micrometers range. Thus, as new instruments bridge the gap between microwave and infrared to frequencies even higher than 183 GHz, radiative transfer modelers are cautioned to explicitly address scattering characteristics of such clouds.

  10. Dispersive liquid-liquid microextraction combined with graphite furnace atomic absorption spectrometry: ultra trace determination of cadmium in water samples.

    PubMed

    Zeini Jahromi, Elham; Bidari, Araz; Assadi, Yaghoub; Milani Hosseini, Mohammad Reza; Jamali, Mohammad Reza

    2007-03-01

    Dispersive liquid-liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 microL methanol (disperser solvent) containing 34 microL carbon tetrachloride (extraction solvent) and 0.00010 g ammonium pyrrolidine dithiocarbamate (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with ammonium pyrrolidine dithiocarbamate, and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then a 20 microL of sedimented phase containing enriched analyte was determined by GF AAS. Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 125 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the rage of 2-20 ng L(-1) with detection limit of 0.6 ng L(-1). The relative standard deviation (R.S.D.s) for ten replicate measurements of 20 ng L(-1) of cadmium was 3.5%. The relative recoveries of cadmium in tap, sea and rivers water samples at spiking level of 5 and 10 ng L(-1) are 108, 95, 87 and 98%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on-line liquid-liquid extraction, single drop microextraction (SDME), on-line solid phase extraction (SPE) and co-precipitation based on bibliographic data. Therefore, DLLME combined with GF AAS is a very simple, rapid and sensitive method, which requires low volume of sample (5.00 mL). PMID:17386679

  11. Are there Helium-like Protonic States of Individual Water Molecules in Liquid H2O?

    E-print Network

    Mueller-Herold, Ulrich

    2015-01-01

    Are there indications that individual H2O molecules in liquid water can loose their bent structure, i.e. that the protons give up their rigid angular correlation and behave largely uncorrelated, similar to electrons in the ground-state of helium? In agreement with the two-state picture of liquid water this would allow for the thermal coexistence of tetraedrically coordinated and spherical water molecules in the liquid. In the Hooke-Calogero model of a confined triatomic of XY2-type it is shown that energetically low-lying zero orbital-momentum states, which are bent if unconfined can change to helium-like shape under increasing confinement strength f. For the respective states this occurs at different values for f. It turns out that at f = 2.79 a bent and a helium-like state can thermally coexist. In order to characterize more precisely 'helium-like' angular correlation a maximum entropy estimate for the marginal correlation of electrons in the helium ground state is given. KEY WORDS: Liquid water, molecular ...

  12. Capillary Electrophoresis and Liquid Chromatography-Mass Spectrometry Analysis of Bisphenol A in Environmental Waters

    E-print Network

    Gosselin, Louis A.

    Capillary Electrophoresis and Liquid Chromatography-Mass Spectrometry Analysis of Bisphenol. Cheeptham Bisphenol A (BPA) and its structural analogues (BPF, BPS, BPP, BPZ, BADGE, BPAP, BPAF) are used water is from rivers and streams. Presence of bisphenols in the environment is crucial and use

  13. HIGH PRESSURE LIQUID CHROMATOGRAPHY TECHNIQUES FOR THE ISOLATION AND IDENTIFICATION OF ORGANICS IN DRINKING WATER EXTRACTS

    EPA Science Inventory

    Some of the potential of high pressure liquid chromatography (HPLC) for sample cleanup of drinking water extracts for later analysis by GC/MS is described. Co-eluting compounds or background can be eliminated, thus improving mass spectra identification of GC peaks and enabling th...

  14. A hydrological analysis of terrestrial and Martian gullies: Implications for liquid water on Mars

    NASA Astrophysics Data System (ADS)

    Hobbs, S. W.; Paull, D. J.; Clarke, J. D. A.

    2014-12-01

    Understanding the role and amounts of liquid water involved in Martian gully formation is critical in studies of the Martian hydrosphere and climate. We performed hydrological analyses using the Manning and Darcy-Weisbach equations in order to infer flow velocities and discharge rates from channels at two gully sites in Noachis Terra, Mars. The results of these analyses were compared with analogous hillside gullies in Australia. We found the velocities and discharge rates for the terrestrial gullies to be comparable to velocities and discharge rates of some small Martian gully channels. In contrast, velocity and discharge in some larger Martian gullies were almost an order of magnitude higher, equating with catastrophic flows on Earth. We postulate that the larger gully channels were more likely formed by a number of smaller flows in a similar manner observed in some terrestrial gullies, a scenario that does not require vast amounts of liquid water to be stable under Martian conditions. In addition, we found that post-fluvial channel widening may have acted on the Martian gullies, probably by dry mass wasting, leading to larger channels than were originally carved by liquid water. Future hydrological analyses of Martian gullies will lead to a greater understanding of the relative importance of dry mass wasting compared to liquid water erosion.

  15. Measurement of Liquid Water Accumulation in a PEMFC with Dead-Ended Anode

    E-print Network

    Stefanopoulou, Anna

    Measurement of Liquid Water Accumulation in a PEMFC with Dead-Ended Anode Jason B. Siegel,a, *,z electrolyte membrane fuel cell PEMFC with a dead-ended anode is observed using neutron imaging stoichiometric conditions. Operating the fuel cell under dead-ended anode conditions offers the oppor- tunity

  16. A Bayesian algorithm for the retrieval of liquid water cloud properties from microwave radiometer

    E-print Network

    radar reflectivity and dual-channel microwave brightness temperatures. The algorithm is based on Bayes the algorithm, we perform retrieval simulations using radar reflectivity and brightness temperatures simulated, clouds, radar, microwave radiometer, Bayes 1. Introduction [2] Liquid water boundary layer clouds

  17. Vapor-Liquid Equilibrium of Monoethanolamine/Piperazine/Water at 35 70 C

    E-print Network

    Rochelle, Gary T.

    Vapor-Liquid Equilibrium of Monoethanolamine/Piperazine/Water at 35 ­ 70 ºC Topical Report Prepared of Texas at Austin May 2006 #12;Dedication To my parents, John and Susan McLees. You believed in my every about my experimental methods from running the FTIR system to data analysis, and even the kinds

  18. Diurnal cycle of liquid water path over the subtropical and tropical oceans

    E-print Network

    Hartmann, Dennis

    , consistent with a diurnal cycle driven largely by cloud solar absorption. In deep convective regions. These diurnal variations, however, were not examined quantita- tively. Ciesielski et al. [2001] has examinedDiurnal cycle of liquid water path over the subtropical and tropical oceans R. Wood, C. S

  19. Elucidating the mechanism of selective ion adsorption to the liquid water surface

    E-print Network

    Geissler, Phillip

    of capillary waves and with a competition between ion hydration energy and the neat liquid's surface tension. air­water interface electrolyte solutions Hofmeister effects nonlinear spectroscopy The adsorption), dispersion forces (1, 20), interfacial roughness (13), and hydration free energy (15, 17, 21), although

  20. Water and a protic ionic liquid acted as refolding additives for chemically denatured enzymes.

    PubMed

    Attri, Pankaj; Venkatesu, P; Kumar, Anil

    2012-10-01

    In this communication, we present the ability of water and a protic ionic liquid, triethyl ammonium phosphate (TEAP) to act as refolding additives for the urea-induced chemical denaturated state of the two enzymes, ?-chymotrypsin and succinylated Con A. We show that the enzymatic activity is regained and in certain circumstances enhanced. PMID:22814381

  1. Dataset used to improve liquid water absorption models in the microwave

    SciTech Connect

    Turner, David

    2015-12-14

    Two datasets, one a compilation of laboratory data and one a compilation from three field sites, are provided here. These datasets provide measurements of the real and imaginary refractive indices and absorption as a function of cloud temperature. These datasets were used in the development of the new liquid water absorption model that was published in Turner et al. 2015.

  2. Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds

    NASA Technical Reports Server (NTRS)

    DelGenio, Anthony

    1999-01-01

    The uncertainty in the global climate sensitivity to an equilibrium doubling of carbon dioxide is often stated to be 1.5-4.5 K, largely due to uncertainties in cloud feedbacks. The lower end of this range is based on the assumption or prediction in some GCMs that cloud liquid water behaves adiabatically, thus implying that cloud optical thickness will increase in a warming climate if the physical thickness of clouds is invariant. Satellite observations of low-level cloud optical thickness and liquid water path have challenged this assumption, however, at low and middle latitudes. We attempt to explain the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurements (ARM) Cloud And Radiation Testbed (CART) site in the Southern Great Plains. We find that low cloud liquid water path is insensitive to temperature in winter but strongly decreases with temperature in summer. The latter occurs because surface relative humidity decreases with warming, causing cloud base to rise and clouds to geometrically thin. Meanwhile, inferred liquid water contents hardly vary with temperature, suggesting entrainment depletion. Physically, the temperature dependence appears to represent a transition from higher probabilities of stratified boundary layers at cold temperatures to a higher incidence of convective boundary layers at warm temperatures. The combination of our results and the earlier satellite findings imply that the minimum climate sensitivity should be revised upward from 1.5 K.

  3. IMPACT OF ORGANIC COMPOUNDS ON THE CONCENTRATIONS OF LIQUID WATER IN AMBIENT PM2.5

    EPA Science Inventory

    A field study was undertaken during the summer of 2000 to assess the impact of the presence of organic compounds on the liquid water concentrations of PM2.5 samples. The selected site, located in Research Triangle Park, North Carolina, was in a semi-rural environment with expe...

  4. New Mexico cloud super cooled liquid water survey final report 2009.

    SciTech Connect

    Beavis, Nick; Roskovensky, John K.; Ivey, Mark D.

    2010-02-01

    Los Alamos and Sandia National Laboratories are partners in an effort to survey the super-cooled liquid water in clouds over the state of New Mexico in a project sponsored by the New Mexico Small Business Assistance Program. This report summarizes the scientific work performed at Sandia National Laboratories during the 2009. In this second year of the project a practical methodology for estimating cloud super-cooled liquid water was created. This was accomplished through the analysis of certain MODIS sensor satellite derived cloud products and vetted parameterizations techniques. A software code was developed to analyze multiple cases automatically. The eighty-one storm events identified in the previous year effort from 2006-2007 were again the focus. Six derived MODIS products were obtained first through careful MODIS image evaluation. Both cloud and clear-sky properties from this dataset were determined over New Mexico. Sensitivity studies were performed that identified the parameters which most influenced the estimation of cloud super-cooled liquid water. Limited validation was undertaken to ensure the soundness of the cloud super-cooled estimates. Finally, a path forward was formulized to insure the successful completion of the initial scientific goals which include analyzing different of annual datasets, validation of the developed algorithm, and the creation of a user-friendly and interactive tool for estimating cloud super-cooled liquid water.

  5. Optical Kerr effect of liquid and supercooled water: the experimental and data analysis perspective.

    PubMed

    Taschin, A; Bartolini, P; Eramo, R; Righini, R; Torre, R

    2014-08-28

    The time-resolved optical Kerr effect spectroscopy (OKE) is a powerful experimental tool enabling accurate investigations of the dynamic phenomena in molecular liquids. We introduced innovative experimental and fitting procedures, that enable a safe deconvolution of sample response function from the instrumental function. This is a critical issue in order to measure the dynamics of liquid water. We report OKE data on water measuring intermolecular vibrations and the structural relaxation processes in an extended temperature range, inclusive of the supercooled states. The unpreceded data quality makes possible a solid comparison with few theoretical models: the multi-mode Brownian oscillator model, the Kubo's discrete random jump model, and the schematic mode-coupling model. All these models produce reasonable good fits of the OKE data of stable liquid water, i.e., over the freezing point. The features of water dynamics in the OKE data becomes unambiguous only at lower temperatures, i.e., for water in the metastable supercooled phase. We found that the schematic mode-coupling model provides the more rigorous and complete model for water dynamics, even if its intrinsic hydrodynamic approach does not give a direct access to the molecular information. PMID:25173021

  6. Initial evaluation of profiles of temperature, water vapor, and cloud liquid water from a new microwave profiling radiometer.

    SciTech Connect

    Liljegren, J. C.; Lesht, B. M.; Clothiaux, E. E.; Kato, S.

    2000-11-01

    To measure the vertical profiles of temperature and water vapor that are essential for modeling atmospheric processes, the Atmospheric Radiation Measurement (ARM) Program of the U. S. Department of Energy launches approximately 2600 radiosondes each year from its Southern Great Plains (SGP) facilities in Oklahoma and Kansas, USA. The annual cost of this effort exceeds $500,000 in materials and labor. Despite the expense, these soundings have a coarse temporal resolution and reporting interval compared with model time steps. In contrast, the radiation measurements used for model evaluations have temporal resolutions and reporting intervals of a few minutes at most. Conversely, radiosondes have a much higher vertical spatial resolution than most models can use. Modelers generally reduce the vertical resolution of the soundings by averaging over the vertical layers of the model. Recently, Radiometries Corporation (Boulder, Colorado, USA) developed a 12-channel, ground-based microwave radiometer capable of providing continuous, real-time vertical profiles of temperature, water vapor, and limited-resolution cloud liquid water from the surface to 10 km in nearly all weather conditions. The microwave radiometer profiler (MWRP) offers a much finer temporal resolution and reporting interval (about 10 minutes) than the radiosonde but a coarser vertical resolution that may be more appropriate for models. Profiles of temperature, water vapor, and cloud liquid water are obtained at 47 levels: from 0 to 1 km above ground level at 100-m intervals and from 1 to 10 km at 250-m intervals. The profiles are derived from the measured brightness temperatures with neural network retrieval. In Figure 1, profiles of temperature, water vapor, and cloud liquid water for 10 May 2000 are presented as time-height plots. MWRP profiles coincident with the 11:31 UTC (05:31 local) and 23:47 UTC (17:47 local) soundings for 10 May are presented in Figures 2 and 3, respectively. These profiles illustrate typical performance for temperature inversion and lapse conditions.

  7. Photochemical oxidation of water and reduction of polyoxometalate anions at interfaces of water with ionic liquids or diethylether.

    PubMed

    Bernardini, Gianluca; Wedd, Anthony G; Zhao, Chuan; Bond, Alan M

    2012-07-17

    Photoreduction of [P(2)W(18)O(62)](6-), [S(2)Mo(18)O(62)](4-), and [S(2)W(18)O(62)](4-) polyoxometalate anions (POMs) and oxidation of water occurs when water-ionic liquid and water-diethylether interfaces are irradiated with white light (275-750 nm) or sunlight. The ionic liquids (ILs) employed were aprotic ([Bmim]X; Bmim = (1-butyl-3-methylimidazolium, X = BF(4), PF(6)) and protic (DEAS = diethanolamine hydrogen sulphate; DEAP = diethanolamine hydrogen phosphate). Photochemical formation of reduced POMs at both thermodynamically stable and unstable water-IL interfaces led to their initial diffusion into the aqueous phase and subsequent extraction into the IL phase. The mass transport was monitored visually by color change and by steady-state voltammetry at microelectrodes placed near the interface and in the bulk solution phases. However, no diffusion into the organic phase was observed when [P(2)W(18)O(62)](6-) was photo-reduced at the water-diethylether interface. In all cases, water acted as the electron donor to give the overall process: 4POM + 2H(2)O + h? ? 4POM(-) + 4H(+) + O(2). However, more highly reduced POM species are likely to be generated as intermediates. The rate of diffusion of photo-generated POM(-) was dependent on the initial concentration of oxidized POM and the viscosity of the IL (or mixed phase system produced in cases in which the interface is thermodynamically unstable). In the water-DEAS system, the evolution of dioxygen was monitored in situ in the aqueous phase by using a Clark-type oxygen sensor. Differences in the structures of bulk and interfacial water are implicated in the activation of water. An analogous series of reactions occurred upon irradiation of solid POM salts in the presence of water vapor. PMID:22753501

  8. Mars Gully: No Mineral Trace of Liquid Water

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This image of the Centauri-Hellas Montes region was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 2107 UTC (4:07 p.m. EST) on Jan. 9, 2007, near 38.41 degrees south latitude, 96.81 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered is slightly wider than 10 kilometers (6.2 miles) at its narrowest point.

    Narrow gullies found on hills and crater walls in many mid-latitude regions of Mars have been interpreted previously as cut by geologically 'recent' running water, meaning water that flowed on Mars long after impact cratering, tectonic forces, volcanism or other processes created the underlying landforms. Some gullies even eroded into sand dunes, which would date their formation at thousands to millions of years ago, or less. In fact, Mars Orbiter Camera (MOC) images showed two of the gullies have bright deposits near their downslope ends - but those deposits were absent in images taken just a few years earlier. The bright deposits must have formed within the period 1999-2004.

    Has there been running water on Mars so recently? To address that question, CRISM and MRO's other instruments observed the bright gully deposits. CRISM's objective was to determine if the bright deposits contained salts left behind from water evaporating into Mars' thin air. The high-resolution imager's (HiRISE's) objective was to determine if the small-scale morphology was consistent with formation by running water.

    This CRISM image of a bright gully deposit was constructed by showing 2.53, 1.50, and 1.08 micrometer light in the red, green, and blue image planes. CRISM can just resolve the deposits (highlighted by arrows in the inset), which are only a few tens of meters (about 150 feet) across. The spectrum of the deposits barely differs from that of the surrounding material, and is just a little brighter. This difference could simply be explained by a slightly greater content of dust than in the surrounding soil. In contrast, older deposits elsewhere on Mars ( such as Valles Marineris) that do contain hydrated salts have distinctive spectral features near 1.9 and 3.0 microns. The gully deposits lack these features, and exhibit no evidence for water-deposited salts. Just-published HiRISE images of this and other bright gully deposits do not rule out water, but they do suggest that the bright deposits could also have formed by dust that slid downslope and accumulated in the gullies.

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.

  9. Interaction of a long alkyl chain protic ionic liquid and water.

    PubMed

    Bodo, Enrico; Mangialardo, Sara; Capitani, Francesco; Gontrani, Lorenzo; Leonelli, Francesca; Postorino, Paolo

    2014-05-28

    A combined experimental/theoretical approach has been used to investigate the role of water in modifying the microscopic interactions characterizing the optical response of 1-butyl-ammonium nitrate (BAN) water solutions. Raman spectra, dominated by the signal from the protic ionic liquid, were collected as a function of the water content, and the corresponding spatial organization of the ionic couples, as well as their local arrangement with water molecules, was studied exploiting classical molecular dynamics calculations. High quality spectroscopic data, combined with a careful analysis, revealed that water affects the vibrational spectrum BAN in solution: as the water concentration is increased, peaks assigned to stretching modes show a frequency hardening together with a shape narrowing, whereas the opposite behavior is observed for peaks assigned to bending modes. Calculation results clearly show a nanometric spatial organization of the ionic couples that is not destroyed on increasing the water content at least within an intermediate range. Our combined results show indeed that small water concentrations even increase the local order. Water molecules are located among ionic couples and are closer to the anion than the cation, as confirmed by the computation of the number of H-bonds which is greater for water-anion than for water-cation. The whole results set thus clarifies the microscopic scenario of the BAN-water interaction and underlines the main role of the extended hydrogen bond network among water molecules and nitrate anions. PMID:24880297

  10. Interaction of a long alkyl chain protic ionic liquid and water

    NASA Astrophysics Data System (ADS)

    Bodo, Enrico; Mangialardo, Sara; Capitani, Francesco; Gontrani, Lorenzo; Leonelli, Francesca; Postorino, Paolo

    2014-05-01

    A combined experimental/theoretical approach has been used to investigate the role of water in modifying the microscopic interactions characterizing the optical response of 1-butyl-ammonium nitrate (BAN) water solutions. Raman spectra, dominated by the signal from the protic ionic liquid, were collected as a function of the water content, and the corresponding spatial organization of the ionic couples, as well as their local arrangement with water molecules, was studied exploiting classical molecular dynamics calculations. High quality spectroscopic data, combined with a careful analysis, revealed that water affects the vibrational spectrum BAN in solution: as the water concentration is increased, peaks assigned to stretching modes show a frequency hardening together with a shape narrowing, whereas the opposite behavior is observed for peaks assigned to bending modes. Calculation results clearly show a nanometric spatial organization of the ionic couples that is not destroyed on increasing the water content at least within an intermediate range. Our combined results show indeed that small water concentrations even increase the local order. Water molecules are located among ionic couples and are closer to the anion than the cation, as confirmed by the computation of the number of H-bonds which is greater for water-anion than for water-cation. The whole results set thus clarifies the microscopic scenario of the BAN-water interaction and underlines the main role of the extended hydrogen bond network among water molecules and nitrate anions.

  11. Finite-size scaling investigation of the liquid-liquid critical point in ST2 water and its stability with respect to crystallization

    NASA Astrophysics Data System (ADS)

    Kesselring, T. A.; Lascaris, E.; Franzese, G.; Buldyrev, S. V.; Herrmann, H. J.; Stanley, H. E.

    2013-06-01

    The liquid-liquid critical point scenario of water hypothesizes the existence of two metastable liquid phases—low-density liquid (LDL) and high-density liquid (HDL)—deep within the supercooled region. The hypothesis originates from computer simulations of the ST2 water model, but the stability of the LDL phase with respect to the crystal is still being debated. We simulate supercooled ST2 water at constant pressure, constant temperature, and constant number of molecules N for N ? 729 and times up to 1 ?s. We observe clear differences between the two liquids, both structural and dynamical. Using several methods, including finite-size scaling, we confirm the presence of a liquid-liquid phase transition ending in a critical point. We find that the LDL is stable with respect to the crystal in 98% of our runs (we perform 372 runs for LDL or LDL-like states), and in 100% of our runs for the two largest system sizes (N = 512 and 729, for which we perform 136 runs for LDL or LDL-like states). In all these runs, tiny crystallites grow and then melt within 1 ?s. Only for N ? 343 we observe six events (over 236 runs for LDL or LDL-like states) of spontaneous crystallization after crystallites reach an estimated critical size of about 70 ± 10 molecules.

  12. Scattering of water from the glycerol liquid-vacuum interface

    NASA Technical Reports Server (NTRS)

    Benjamin, I.; Wilson, M. A.; Pohorille, A.; Nathanson, G. M.

    1995-01-01

    Molecular dynamics calculations of the scattering of D2O from the glycerol surface at different collision energies are reported. The results for the trapping probabilities and energy transfer are in good agreement with experiments. The calculations demonstrate that the strong attractive forces between these two strongly hydrogen bonding molecules have only a minor effect on the initial collision dynamics. The trapping probability is influenced to a significant extent by the repulsive hard sphere-like initial encounter with the corrugated surface and, only at a later stage, by the efficiency of energy flow in the multiple interactions between the water and the surface molecules.

  13. Preferential adsorption from liquid water-ethanol mixtures in alumina pores.

    PubMed

    Phan, Anh; Cole, David R; Striolo, Alberto

    2014-07-15

    The sorptivity, structure, and dynamics of liquid water-ethanol mixtures confined in alumina pores were studied by molecular dynamics simulations. Due to an effective stronger attraction between water and the alumina surface, our simulations show that water is preferentially adsorbed in alumina nanopores from bulk solutions of varying composition. These results are in good qualitative agreement with experimental data reported by Rao and Sircar (Adsorpt. Sci. Technol. 1993, 10, 93). Analysis of the simulated trajectories allows us to predict that water diffuses through the narrow pores more easily than ethanol, in part because of its smaller size. Our results suggest that ethanol has an antiplasticization effect on water within the narrow pores considered here, whereas it has a plasticization effect on water in the bulk. Rao and Sircar suggested that alumina could be used in concentration swing and/or concentration-thermal swing adsorption processes to separate water from ethanol. In addition, our results suggest the possibility of using alumina for manufacturing permselective membranes to produce anhydrous ethanol from liquid water-ethanol solutions. PMID:24933315

  14. Nanofluid of zinc oxide nanoparticles in ionic liquid for single drop liquid microextraction of fungicides in environmental waters prior to high performance liquid chromatographic analysis.

    PubMed

    Amde, Meseret; Tan, Zhi-Qiang; Liu, Rui; Liu, Jing-Fu

    2015-05-22

    Using a nanofluid obtained by dispersing ZnO nanoparticles (ZnO NPs) in 1-hexyl-3-methylimidazolium hexafluorophosphate, new single drop microextraction method was developed for simultaneous extraction of three fungicides (chlorothalonil, kresoxim-methyl and famoxadone) in water samples prior to their analysis by high performance liquid chromatography (HPLC-VWD). The parameters affecting the extraction efficiency such as amount of ZnO NPs in the nanofluid, solvent volume, extraction time, stirring rate, pH and ionic strength of the sample solution were optimized. Under the optimized conditions, the limits of detection were in the range of 0.13-0.19ng/mL, the precision of the method assessed with intra-day and inter-day relative standard deviations were <4.82% and <7.04%, respectively. The proposed method was successfully applied to determine the three fungicides in real water samples including lake water, river water, as well as effluent and influent of wastewater treatment plant, with recoveries in the range of 74.94-96.11% at 5ng/mL spiking level. Besides to being environmental friendly, the high enrichment factor and the data quality obtained with the proposed method demonstrated its potential for application in multi residue analysis of fungicides in actual water samples. PMID:25857539

  15. Effect of water on the carbon dioxide absorption by 1-alkyl-3-methylimidazolium acetate ionic liquids.

    PubMed

    Stevanovic, Stéphane; Podgoršek, Ajda; Pádua, Agilio A H; Costa Gomes, Margarida F

    2012-12-13

    The absorption of carbon dioxide by the pure ionic liquids 1-ethyl-3-methylimidazolium acetate ([C(1)C(2)Im][OAc]) and 1-butyl-3-methylimidazolium acetate ([C(1)C(4)Im][OAc]) was studied experimentally from 303 to 343 K. As expected, the mole fraction of absorbed carbon dioxide is high (0.16 at 303 K and 5.5 kPa and 0.19 at 303 and 9.6 KPa for [C(1)C(2)Im][OAc] and [C(1)C(4)Im][OAc], respectively), does not obey Henry's law, and is compatible with the chemisorption of the gas by the liquid. Evidence of a chemical reaction between the gas and the liquid was found both by NMR and by molecular simulation. In the presence of water, the properties of the liquid absorber significantly change, especially the viscosity that decreases by as much as 25% (to 78 mPa s) and 30% (to 262 mPa s) in the presence of 0.2 mol fraction of water for [C(1)C(2)Im][OAc] and [C(1)C(2)Im][OAc] at 303 K, respectively. The absorption of carbon dioxide decreases when the water concentration increases: a decrease of 83% in CO(2) absorption is found for [C(1)C(4)Im][OAc] with 0.6 mol fraction of water at 303 K. It is proved in this work, by combining experimental data with molecular simulation, that the presence of water not only renders the chemical reaction between the gas and the ionic liquid less favorable but also lowers the (physical) solubility of the gas as it competes by the same solvation sites of the ionic liquid. The lowering of the viscosity of the liquid absorbent largely compensates these apparent drawbacks and the mixtures of [C(1)C(2)Im][OAc] and [C(1)C(2)Im][OAc] with water seem promising to be used for carbon dioxide capture. PMID:23145571

  16. Molecular dynamics analysis of the velocity slip of a water and methanol liquid mixture

    NASA Astrophysics Data System (ADS)

    Nakaoka, Satoshi; Yamaguchi, Yasutaka; Omori, Takeshi; Kagawa, Masaru; Nakajima, Tadashi; Fujimura, Hideo

    2015-08-01

    The effect of methanol mixing on a nanoscale water flow was examined by using nonequilibrium molecular dynamics simulations of a Couette-type flow between nonpolarized smooth solid surfaces. Water and methanol molecules were uniformly mixed in the bulk, whereas at the solid-liquid interface methanol molecules showed a tendency to be adsorbed on the solid surface. Similar to a macroscale Couette flow, the shear stress exerted on the solid surface was equal to the shear stress in the liquid, showing that the mechanical balance holds in nanoscale. In addition, the shear stress in the liquid bulk was equal to the viscous stress which is a product of viscosity and velocity gradient. When more methanol molecules were adsorbed on the solid surface, the friction coefficient (FC) between solid and liquid was largely reduced with a small amount of methanol and that led to a remarkable decrease of the shear stress. The cause of the FC reduction was investigated in terms of the local rotational diffusion coefficient (RDC) near the solid surface, and it was shown that different from an existing model, the FC and local RDC were not simply inversely proportional to each other in the mixture system because the solid-liquid interfacial state was more complex.

  17. Ultrafast conversions between hydrogen bonded structures in liquid water observed by femtosecond x-ray spectroscopy

    SciTech Connect

    Wen, Haidan; Huse, Nils; Schoenlein, Robert W.; Lindenberg, Aaron M.

    2010-05-01

    We present the first femtosecond soft x-ray spectroscopy in liquids, enabling the observation of changes in hydrogen bond structures in water via core-hole excitation. The oxygen K-edge of vibrationally excited water is probed with femtosecond soft x-ray pulses, exploiting the relation between different water structures and distinct x-ray spectral features. After excitation of the intramolecular OH stretching vibration, characteristic x-ray absorption changes monitor the conversion of strongly hydrogen-bonded water structures to more disordered structures with weaker hydrogen-bonding described by a single subpicosecond time constant. The latter describes the thermalization time of vibrational excitations and defines the characteristic maximum rate with which nonequilibrium populations of more strongly hydrogen-bonded water structures convert to less-bonded ones. On short time scales, the relaxation of vibrational excitations leads to a transient high-pressure state and a transient absorption spectrum different from that of statically heated water.

  18. Liquid water transport characteristics of porous diffusion media in polymer electrolyte membrane fuel cells: A review

    NASA Astrophysics Data System (ADS)

    Liu, Xunliang; Peng, Fangyuan; Lou, Guofeng; Wen, Zhi

    2015-12-01

    Fundamental understanding of liquid water transport in gas diffusion media (GDM) is important to improve the material and structure design of polymer electrolyte membrane (PEM) fuel cells. Continuum methods of two-phase flow modeling facilitate to give more details of relevant information. The proper empirical correlations of liquid water transport properties, such as capillary characteristics, water relative permeability and effective contact angle, are crucial to two phase flow modeling and cell performance prediction. In this work, researches on these properties in the last decade are reviewed. Various efforts have been devoted to determine the water transport properties for GDMs. However, most of the experimental studies are ex-situ measurements. In-situ measurements for GDMs and extending techniques available to study the catalyst layer and the microporous layer will be further challenges. Using the Leverett-Udell correlation is not recommended for quantitative modeling. The reliable Leverett-type correlation for GDMs, with the inclusion of the cosine of effective contact angle, is desirable but hard to be established for modeling two-phase flow in GDMs. A comprehensive data set of liquid water transport properties is needed for various GDM materials under different PEM fuel cell operating conditions.

  19. PREFACE: Dynamic crossover phenomena in water and other glass-forming liquids Dynamic crossover phenomena in water and other glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin; Baglioni, Piero

    2012-02-01

    This special section has been inspired by the workshop on Dynamic Crossover Phenomena in Water and Other Glass-Forming Liquids, held during November 11-13, 2010 at Pensione Bencistà, Fiesole, Italy, a well-preserved 14th century Italian villa tucked high in the hills overlooking Florence. The meeting, an assembly of world renowned scientists, was organized as a special occasion to celebrate the 75th birthday of Professor Sow-Hsin Chen of MIT, a pioneer in several aspects of complex fluids and soft matter physics. The workshop covered a large variety of experimental and theoretical research topics of current interest related to dynamic crossover phenomena in water and, more generally, in other glass-forming liquids. The 30 invited speakers/lecturers and approximately 60 participants were a select group of prominent physicists and chemists from the USA, Europe, Asia and Mexico, who are actively working in the field. Some highlights of this special issue include the following works. Professor Yamaguchi's group and their collaborators present a neutron spin echo study of the coherent intermediate scattering function of heavy water confined in cylindrical pores of MCM-41-C10 silica material in the temperature range 190-298 K. They clearly show that a fragile-to-strong (FTS) dynamic crossover occurs at about 225 K. They attribute the FTS dynamic crossover to the formation of a tetrahedral-like structure, which is preserved in the bulk-like water confined to the central part of the cylindrical pores. Mamontov and Kolesnikov et al study the collective excitations in an aqueous solution of lithium chloride over a temperature range of 205-270 K using neutron and x-ray Rayleigh-Brillouin (coherent) scattering. They detect both the low-frequency and the high-frequency sounds known to exist in pure bulk water above the melting temperature. They also perform neutron (incoherent) and x-ray (coherent) elastic intensity scan measurements. Clear evidence of the crossover in the dynamics of the water molecules in the solution is observed in the single-particle relaxational dynamics in the ?eV (nanosecond) time scale, but not in the collective dynamics on the meV (picosecond) time scale. Mallamace et al discuss the dynamic crossover phenomenon in both bulk water and protein hydration water. They collect previous and new experimental data from different experimental techniques and molecular dynamic simulations, and are able to develop a unified picture for the different dynamical findings. Gallo et al present a MD study of confined water in MCM-41S-15 in order to test the applicability of Mode Coupling Theory (MCT) to the dynamics of the hydration water confined in the cylindrical pores of nominal diameter 15 Å. They find that the self dynamics of the hydration water is well described by MCT down to the crossover temperature TC. However, below TC the predictions of idealized MCT no longer apply, since hopping processes intervene and water turns into a strong liquid. Soper raises some questions as to the validity of the analysis method employed to determine the density of water confined in porous silica material MCM-41-S15 from recent neutron scattering experiments. Professors Stanley, Franzese and his collaborators describe an efficient Monte Carlo simulation of a coarse-grained model of water to study the phase diagram of a water monolayer confined in a fixed disordered matrix of hydrophobic nanoparticles between two hydrophobic plates. They find a drastic change of phase behavior of the confined water, such as shortening of the liquid-liquid phase transition line, upon increasing the concentration of the hydrophobic nano-particles. Sciortino and collaborators compute the equilibrium phase diagram of two simple models for patchy particles with three and five patches in a very broad range of pressure and temperature. The three-patch model produces a stable gas-liquid critical point. Yun Liu et al investigate, via small angle neutron scattering and neutron spin echo measurements, the effect of temperature on dynamic cluster formation of co

  20. Non-porous membrane-assisted liquid-liquid extraction of UV filter compounds from water samples.

    PubMed

    Rodil, Rosario; Schrader, Steffi; Moeder, Monika

    2009-06-12

    A method for the determination of nine UV filter compounds [benzophenone-3 (BP-3), isoamyl methoxycinnamate, 4-methylbenzylidene camphor, octocrylene (OC), butyl methoxydibenzoylmethane, ethylhexyl dimethyl p-aminobenzoate (OD-PABA), ethylhexyl methoxycinnamate (EHMC), ethylhexyl salicylate and homosalate] in water samples was developed and evaluated. The procedure includes non-porous membrane-assisted liquid-liquid extraction (MALLE) and LC-atmospheric pressure photoionization (APPI)-MS/MS. Membrane bags made of different polymeric materials were examined to enable a fast and simple extraction of the target analytes. Among the polymeric materials tested, low- and high-density polyethylene membranes proved to be well suited to adsorb the analytes from water samples. Finally, 2 cm length tailor-made membrane bags were prepared from low-density polyethylene in order to accommodate 100 microL of propanol. The fully optimised protocol provides recoveries from 76% to 101% and limits of detection (LOD) between 0.4 ng L(-1) (OD-PABA) and 16 ng L(-1) (EHMC). The interday repeatability of the whole protocol was below 18%. The effective separation of matrix molecules was proved by only marginal matrix influence during the APPI-MS analysis since no ion suppression effects were observed. During the extraction step, the influence of the matrix was only significant when non-treated wastewater was analysed. The analysis of lake water indicated the presence of seven UV filter compounds included in this study at concentrations between 40 ng L(-1) (BP-3) and 4381 ng L(-1) (OC). In non-treated wastewater several UV filters were also detected at concentration levels as high as 5322 ng L(-1) (OC). PMID:19419722

  1. Ultrafast vibrational and structural dynamics of the proton in liquid water.

    PubMed

    Woutersen, Sander; Bakker, Huib J

    2006-04-01

    The dynamical behavior of excess protons in liquid water is investigated using femtosecond vibrational pump-probe spectroscopy. By resonantly exciting the O-H+-stretching mode of the H9O4(+) (Eigen) hydration structure of the proton and probing the subsequent absorption change over a broad frequency range, the dynamics of the proton is observed in real time. The lifetime of the protonic stretching mode is found to be approximately 120 fs, shorter than for any other vibration in liquid water. We also observe the interconversion between the H9O4(+) (Eigen) and H5O2(+) (Zundel) hydration structures of the proton. This interconversion, which constitutes an essential step of proton transport in water, is found to occur on an extremely fast (< 100 fs) time scale. PMID:16712045

  2. Molecular characteristics of H2O in hydrate/ice/liquid water mixture

    NASA Astrophysics Data System (ADS)

    Li, Qibin; Tang, Qizhong; Peng, Tiefeng; Zhang, Xiaomin; Liu, Chao; Shi, Xiaoyang

    2015-09-01

    The interfacial properties of hydrate and its ambient play an important role in hydrate technique. In this paper, the molecular characteristics of H2O in hydrate/ice/liquid water mixture system are investigated based on molecular dynamics (MD) simulations. The structure I (sI) methane hydrate is partially heated to obtain the studied system. The properties including hydrogen bond, radial distribution function (RDF) and F3 order parameter (tetrahedral coordinated parameter of H2O) indicate that there is little difference of water structure in the hydrate region and ice/liquid water mixture region. The F4 order parameter (parameter based on H-O-O-H torsion angles of H2O) could be used to distinguish the different region. The value of F4 experiences the continuous change at interface between mixture region and hydrate region.

  3. The initial responses of hot liquid water released under low atmospheric pressures: Experimental insights

    NASA Astrophysics Data System (ADS)

    Bargery, Alistair Simon; Lane, Stephen J.; Barrett, Alexander; Wilson, Lionel; Gilbert, Jennie S.

    2010-11-01

    Experiments have been performed to simulate the shallow ascent and surface release of water and brines under low atmospheric pressure. Atmospheric pressure was treated as an independent variable and water temperature and vapor pressure were examined as a function of total pressure variation down to low pressures. The physical and thermal responses of water to reducing pressure were monitored with pressure transducers, temperature sensors and visible imaging. Data were obtained for pure water and for solutions with dissolved NaCl or CO 2. The experiments showed the pressure conditions under which the water remained liquid, underwent a rapid phase change to the gas state by boiling, and then solidified because of removal of latent heat. Liquid water is removed from phase equilibrium by decompression. Solid, liquid and gaseous water are present simultaneously, and not at the 611 Pa triple point, because dynamic interactions between the phases maintain unstable temperature gradients. After phase changes stop, the system reverts to equilibrium with its surroundings. Surface and shallow subsurface pressure conditions were simulated for Mars and the icy satellites of the outer Solar System. Freezing by evaporation in the absence of wind on Mars is shown to be unlikely for pure water at pressures greater than c. 670 Pa, and for saline solutions at pressures greater than c. 610 Pa. The physical nature of ice that forms depends on the salt content. Ice formed from saline water at pressures less than c. 610 Pa could be similar to terrestrial sea ice. Ice formed from pure water at pressures less than c. 100 Pa develops a low thermal conductivity and a 'honeycomb' structure created by sublimation. This ice could have a density as low as c. 450 kg m -3 and a thermal conductivity as low as 1.6 W m -1 K -1, and is highly reflective, more akin to snow than the clear ice from which it grew. The physical properties of ice formed from either pure or saline water at low pressures will act to reduce the surface temperature, and hence rate of sublimation, thereby prolonging the lifespan of any liquid water beneath.

  4. Improved sensitivity gas chromatography-mass spectrometry determination of parabens in waters using ionic liquids.

    PubMed

    Cacho, Juan Ignacio; Campillo, Natalia; Viñas, Pilar; Hernández-Córdoba, Manuel

    2016-01-01

    A new procedure for the introduction of ionic liquid samples in gas chromatography (GC) is proposed. This procedure, based on microvial insert thermal desorption, allows the direct analysis of the compounds preconcentrated by ionic liquid based liquid-liquid microextraction (IL-LLME) using the combination of a thermal desorption unit (TDU) and a programmed temperature vaporization injector (PTV). Two different IL-LLME methodologies, one based on the formation of a microdroplet emulsion by dispersive liquid-liquid microextraction (DLLME) and other through ultrasound-assisted emulsification microextraction (USAEME) were studied and evaluated. IL-DLLME proved advantageous and consequently, it was adopted for preconcentration purposes. This easy to apply approach was used for the determination of five parabens (methyl-, ethyl-, propyl-, butyl- and isobutyl paraben) in swimming pool waters, after in situ acetylation. The optimized conditions of TDU/PTV allowed the analytes contained in 20µL of the enriched IL to be transferred to the capillary column. Quantification of the samples was carried out against aqueous standards, and quantification limits of between 4.3 and 8.1ngL(-1) were obtained, depending on the compound. Concentrations of between 9 and 47ngL(-1) for some analytes were obtained in the analysis of ten samples. PMID:26695305

  5. MWRRET Value-Added Product: The Retrieval of Liquid Water Path and Precipitable Water Vapor from Microwave Radiometer (MWR) Datasets

    SciTech Connect

    KL Gaustad; DD Turner

    2007-09-30

    This report provides a short description of the Atmospheric Radiation Measurement (ARM) microwave radiometer (MWR) RETrievel (MWRRET) Value-Added Product (VAP) algorithm. This algorithm utilizes complimentary physical and statistical retrieval methods and applies brightness temperature offsets to reduce spurious liquid water path (LWP) bias in clear skies resulting in significantly improved precipitable water vapor (PWV) and LWP retrievals. We present a general overview of the technique, input parameters, output products, and describe data quality checks. A more complete discussion of the theory and results is given in Turner et al. (2007b).

  6. Linking Europa's plume activity to tides, tectonics, and liquid water

    E-print Network

    Rhoden, Alyssa R; Roth, Lorenz; Retherford, Kurt

    2015-01-01

    Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30 - 80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and...

  7. Cooperativity and hydrogen bond network lifetime in liquid water

    NASA Astrophysics Data System (ADS)

    Lamanna, R.; Floridi, G.; Cannistraro, S.

    1995-10-01

    The lifetime of the H bond network has been calculated as a function of temperature by a statistical five-species model for water in which the H bond cooperativity has been explicitly taken into account. While, on one hand, the Arrhenius behavior of the depolarized Rayleigh scattering data existing in an intermediate temperature region is well reproduced, the model predicts that the H bond lifetime diverges as the supercooled temperature limit is approached. The observed cooperative stabilization of the H bonds in tetracoordinated molecules occurring in the deep supercooled region, where this species becomes the most long-lived one, points out the tendency of the system to unavoidably approach ice rather than to reach a region of dynamical instability.

  8. Effects of water concentration on the structural and diffusion properties of imidazolium-based ionic liquid-water mixtures.

    PubMed

    Niazi, Amir A; Rabideau, Brooks D; Ismail, Ahmed E

    2013-02-01

    We have used molecular dynamics simulations to study the properties of three ionic liquid (IL)-water systems: 1-butyl-3-methylimidazolium chloride ([bmim]Cl), 1-ethyl-3-methylimidazolium acetate ([emim][Ac]), and 1,3-dimethylimidazolium dimethylphosphate ([dmim][DMP]). We observe the transition of those mixtures from pure IL to aqueous solution by analyzing the changes in important bulk properties (density) and structural and bonding properties (radial distribution functions, water clustering, hydrogen bonding, and cationic stacking) as well as dynamical properties (diffusion coefficients) at 12 different concentration samplings of each mixture, ranging from 0.0 to 99.95 mol % water. Our simulations revealed across all of the different structural, bonding, and dynamical properties major structural changes consistent with a transition from IL-water mixture to aqueous solution in all three ILs at water concentrations around 75 mol %. Among the structural changes observed were rapid increase in the frequency of hydrogen bonds, both water-water and water-anion. Similarly, at these critical concentrations, the water clusters formed begin to span the entire simulation box, rather than existing as isolated networks of molecules. At the same time, there is a sudden decrease in cationic stacking at the transition point, followed by a rapid increase near 90 mol % water. Finally, the diffusion coefficients of individual cations and anions show a rapid transition from rates consistent with diffusion in IL's to rates consistent with diffusion in water beginning at 75 mol % water. The location of this transition is consistent, for [bmim]Cl and [dmim][DMP], with the water concentration limit above which the ILs are unable to dissolve cellulose. PMID:23301701

  9. Ionic liquid-based zinc oxide nanofluid for vortex assisted liquid liquid microextraction of inorganic mercury in environmental waters prior to cold vapor atomic fluorescence spectroscopic detection.

    PubMed

    Amde, Meseret; Liu, Jing-Fu; Tan, Zhi-Qiang; Bekana, Deribachew

    2016-03-01

    Zinc oxide nanofluid (ZnO-NF) based vortex assisted liquid liquid microextraction (ZnO-NF VA-LLME) was developed and employed in extraction of inorganic mercury (Hg(2+)) in environmental water samples, followed by cold vapor atomic fluorescence spectrometry (CV-AFS). Unlike other dispersive liquid liquid microextraction techniques, ZnO-NF VA-LLME is free of volatile organic solvents and dispersive solvent consumption. Analytical signals were obtained without back-extraction from the ZnO-NF phase prior to CV-AFS determination. Some essential parameters of the ZnO-NF VA-LLME and cold vapor generation such as composition and volume of the nanofluid, vortexing time, pH of the sample solution, amount of the chelating agent, ionic strength and matrix interferences have been studied. Under optimal conditions, efficient extraction of 1ng/mL of Hg(2+) in 10mL of sample solution was achieved using 50?L of ZnO-NF. The enrichment factor before dilution, detection limits and limits of quantification of the method were about 190, 0.019 and 0.064ng/mL, respectively. The intra and inter days relative standard deviations (n=8) were found to be 4.6% and 7.8%, respectively, at 1ng/mL spiking level. The accuracy of the current method was also evaluated by the analysis of certified reference materials, and the measured Hg(2+) concentration of GBW08603 (9.6ng/mL) and GBW(E)080392 (8.9ng/mL) agreed well with their certified value (10ng/mL). The method was applied to the analysis of Hg(2+) in effluent, influent, lake and river water samples, with recoveries in the range of 79.8-92.8% and 83.6-106.1% at 1ng/mL and 5ng/mL spiking levels, respectively. Overall, ZnO-NF VA-LLME is fast, simple, cost-effective and environmentally friendly and it can be employed for efficient enrichment of the analyte from various water samples. PMID:26717850

  10. Nimbus 7 SMMR Derived Seasonal Variations in the Water Vapor, Liquid Water and Surface Winds over the Global Oceans

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Short, D. A.

    1984-01-01

    Monthly mean distributions of water vapor and liquid water contained in a vertical column of the atmosphere and the surface wind speed were derived from Nimbus Scanning Multichannel Microwave Radiometer (SMMR) observations over the global oceans for the period November 1978 to November 1979. The remote sensing techniques used to estimate these parameters from SMMR are presented to reveal the limitations, accuracies, and applicability of the satellite-derived information for climate studies. On a time scale of the order of a month, the distribution of atmospheric water vapor over the oceans is controlled by the sea surface temperature and the large scale atmospheric circulation. The monthly mean distribution of liquid water content in the atmosphere over the oceans closely reflects the precipitation patterns associated with the convectively and baroclinically active regions. Together with the remotely sensed surface wind speed that is causing the sea surface stress, the data collected reveal the manner in which the ocean-atmosphere system is operating. Prominent differences in the water vapor patterns from one year to the next, or from month to month, are associated with anomalies in the wind and geopotential height fields. In association with such circulation anomalies the precipitation patterns deduced from the meteorological network over adjacent continents also reveal anomalous distributions.

  11. Liquid Water Lakes on Mars Under Present-Day Conditions: Sustainability and Effects on the Subsurface

    NASA Astrophysics Data System (ADS)

    Goldspiel, Jules M.

    2015-11-01

    Decades of Mars exploration have produced ample evidence that aqueous environments once existed on the surface. Much evidence supports groundwater emergence as the source of liquid water on Mars [1-4]. However, cases have also been made for rainfall [5] and snow pack melts [6].Whatever the mechanism by which liquid water is emplaced on the surface of Mars, whether from groundwater seeps, atmospheric precipitation, or some combination of sources, this water would have collected in local topographic lows, and at least temporarily, would have created a local surface water system with dynamic thermal and hydrologic properties. Understanding the physical details of such aqueous systems is important for interpreting the past and present surface environments of Mars. It is also important for evaluating potential habitable zones on or near the surface.In conjunction with analysis of surface and core samples, valuable insight into likely past aqueous sites on Mars can be gained through modeling their formation and evolution. Toward that end, we built a 1D numerical model to follow the evolution of small bodies of liquid water on the surface of Mars. In the model, liquid water at different temperatures is supplied to the surface at different rates while the system is subjected to diurnally and seasonally varying environmental conditions. We recently simulated cases of cold (275 K) and warm (350 K) water collecting in a small depression on the floor of a mid southern latitude impact crater. When inflows create an initial pool > 3 m deep and infiltration can be neglected, we find that the interior of the pool can remain liquid over a full Mars year under the present cold and dry climate as an ice cover slowly thickens [7]. Here we present new results for the thermal and hydrologic evolution of surface water and the associated subsurface region for present-day conditions when infiltration of surface water into the subsurface is considered.[1] Pieri (1980) Science 210.[2] Carr (2006) The Surface of Mars.[3] Wray et al. (2011) J. Geophys. Res. 116.[4] Michalski et al. (2013) Nature Geosci. 6.[5] Craddock and Howard (2002) J. Geophys. Res. 107.[6] Clow (1987) Icarus 72.[7] Goldspiel (2015) Astrobio. Sci. Conf. Abs. 7110.

  12. The effect of the partial pressure of water vapor on the surface tension of the liquid water-air interface.

    PubMed

    Pérez-Díaz, José L; Álvarez-Valenzuela, Marco A; García-Prada, Juan C

    2012-09-01

    Precise measurements of the surface tension of water in air vs. humidity at 5, 10, 15, and 20 °C are shown. For constant temperature, surface tension decreases linearly for increasing humidity in air. These experimental data are in good agreement with a simple model based on Newton's laws here proposed. It is assumed that evaporating molecules of water are ejected from liquid to gas with a mean normal component of the speed of "ejection" greater than zero. A high humidity in the air reduces the net flow of evaporating water molecules lowering the effective surface tension on the drop. Therefore, just steam in air acts as an effective surfactant for the water-air interface. It can partially substitute chemical surfactants helping to reduce their environmental impact. PMID:22717083

  13. Thermally excited capillary waves at vapor/liquid interfaces of water-alcohol mixtures

    NASA Astrophysics Data System (ADS)

    Vaknin, David; Bu, Wei; Sung, Jaeho; Jeon, Yoonnam; Kim, Doseok

    2009-03-01

    The density profiles of liquid/vapor interfaces of water-alcohol (methanol, ethanol and propanol) mixtures were studied by surface-sensitive synchrotron x-ray scattering techniques. X-ray reflectivity and diffuse scattering measurements, from the pure and mixed liquids, were analyzed in the framework of capillary wave theory to address the characteristic length scales of the intrinsic roughness and the shortest capillary wavelength (alternatively, the upper wavevector cutoff in capillary wave theory). Our results establish that the intrinsic roughness is dominated by average interatomic distances. The extracted effective upper wavevector cutoff indicates capillary wave theory breaks down at distances of the order of bulk correlation lengths.

  14. Transient Numerical Modeling of the Combustion of Bi-Component Liquid Droplets: Methanol/Water Mixture

    NASA Technical Reports Server (NTRS)

    Marchese, A. J.; Dryer, F. L.

    1994-01-01

    This study shows that liquid mixtures of methanol and water are attractive candidates for microgravity droplet combustion experiments and associated numerical modeling. The gas phase chemistry for these droplet mixtures is conceptually simple, well understood and substantially validated. In addition, the thermodynamic and transport properties of the liquid mixture have also been well characterized. Furthermore, the results obtained in this study predict that the extinction of these droplets may be observable in ground-based drop to tower experiments. Such experiments will be conducted shortly followed by space-based experiments utilizing the NASA FSDC and DCE experiments.

  15. Formation of H-type liquid crystal dimer at air-water interface

    SciTech Connect

    Karthik, C. Gupta, Adbhut Joshi, Aditya Manjuladevi, V. Gupta, Raj Kumar; Varia, Mahesh C.; Kumar, Sandeep

    2014-04-24

    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.

  16. Communication: The effect of dispersion corrections on the melting temperature of liquid water

    NASA Astrophysics Data System (ADS)

    Yoo, Soohaeng; Xantheas, Sotiris S.

    2011-03-01

    The melting temperature (Tm) of liquid water with the Becke-Lee-Yang-Parr (BLYP) density functional including dispersion corrections (BLYP-D) and the Thole-type, version 3 (TTM3-F) ab-initio based flexible, polarizable classical potential is reported via constant pressure and constant enthalpy (NPH) molecular dynamics simulations of an ice Ih-liquid coexisting system. Dispersion corrections to BLYP lower Tm to about 360 K, a large improvement over the value of Tm > 400 K previously obtained with the original BLYP functional under the same simulation conditions. For TTM3-F, Tm = 248 K from classical molecular dynamics simulations.

  17. Determination of bromate in drinking water by ultraperformance liquid chromatography-tandem mass spectrometry.

    PubMed

    Alsohaimi, Ibrahim Hotan; Alothman, Zeid Abdullah; Khan, Mohammad Rizwan; Abdalla, Mohammad Abulhassan; Busquets, Rosa; Alomary, Ahmad Khodran

    2012-10-01

    Bromate is a byproduct formed as a result of disinfection of bromide-containing source water with ozone or hypochlorite. The International Agency for Research on Cancer has recognized bromate as a possible human carcinogen, thus it is essential to determine in drinking water. Present work highlights a development of sensitive and fast analytical method for bromate determination in drinking water by using ultraperformance liquid chromatography-tandem mass spectrometry. The quality parameters of the developed method were established, obtaining very low limit of detection (0.01 ng/mL), repeatability and reproducibility have been found to be less than 3% in terms of relative standard deviation when analyzing a bromate standard at 0.05 ?g/mL with 0.4 min analysis time. Developed method was applied for the analysis of metropolitan and bottled water from Saudi Arabia; 22 samples have been analyzed. Bromate was detected in the metropolitan water samples (from desalinization source) at concentrations ranging between 3.43 and 75.04 ng/mL and in the bottled water samples at concentrations ranging between 2.07 and 21.90 ng/mL. Moreover, in comparison to established analytical methods such as liquid chromatography-tandem mass spectrometry, the proposed method was found to be very sensitive, selective and rapid for the routine analysis of bromate at low level in drinking water. PMID:22815069

  18. Liquid Water Cloud Properties During the Polarimeter Definition Experiment (PODEX)

    NASA Technical Reports Server (NTRS)

    Alexandrov, Mikhail D.; Cairns, Brian; Wasilewski, Andrzei P.; Ackerman, Andrew S.; McGill, Matthew J.; Yorks, John E.; Hlavka, Dennis L.; Platnick, Steven; Arnold, George; Van Diedenhoven, Bastiaan; Chowdhary, Jacek; Ottaviani, Matteo; Knobelspiesse, Kirk D.

    2015-01-01

    We present retrievals of water cloud properties from the measurements made by the Research Scanning Polarimeter (RSP) during the Polarimeter Definition Experiment (PODEX) held between January 14 and February 6, 2013. The RSP was onboard the high-altitude NASA ER-2 aircraft based at NASA Dryden Aircraft Operation Facility in Palmdale, California. The retrieved cloud characteristics include cloud optical thickness, effective radius and variance of cloud droplet size distribution derived using a parameter-fitting technique, as well as the complete droplet size distribution function obtained by means of Rainbow Fourier Transform. Multi-modal size distributions are decomposed into several modes and the respective effective radii and variances are computed. The methodology used to produce the retrieval dataset is illustrated on the examples of a marine stratocumulus deck off California coast and stratus/fog over California's Central Valley. In the latter case the observed bimodal droplet size distributions were attributed to two-layer cloud structure. All retrieval data are available online from NASA GISS website.

  19. The liquid-liquid transition in supercooled ST2 water: a comparison between umbrella sampling and well-tempered metadynamics.

    PubMed

    Palmer, Jeremy C; Car, Roberto; Debenedetti, Pablo G

    2013-01-01

    We investigate the metastable phase behaviour of the ST2 water model under deeply supercooled conditions. The phase behaviour is examined using umbrella sampling (US) and well-tempered metadynamics (WT-MetaD) simulations to compute the reversible free energy surface parameterized by density and bond-orientation order. We find that free energy surfaces computed with both techniques clearly show two liquid phases in coexistence, in agreement with our earlier US and grand canonical Monte Carlo calculations [Y. Liu, J. C. Palmer, A. Z. Panagiotopoulos and P. G. Debenedetti, J Chem Phys, 2012, 137, 214505; Y. Liu, A. Z. Panagiotopoulos and P. G. Debenedetti, J Chem Phys, 2009, 131, 104508]. While we demonstrate that US and WT-MetaD produce consistent results, the latter technique is estimated to be more computationally efficient by an order of magnitude. As a result, we show that WT-MetaD can be used to study the finite-size scaling behaviour of the free energy barrier separating the two liquids for systems containing 192, 300 and 400 ST2 molecules. Although our results are consistent with the expected N(2/3) scaling law, we conclude that larger systems must be examined to provide conclusive evidence of a first-order phase transition and associated second critical point. PMID:24640486

  20. A novel vortex-assisted liquid-liquid microextraction approach using auxiliary solvent: Determination of iodide in mineral water samples.

    PubMed

    Zaruba, Serhii; Vishnikin, Andriy B; Andruch, Vasil

    2016-03-01

    A novel vortex-assisted liquid-liquid microextraction (VA-LLME) for determination of iodide was developed. The method includes the oxidation of iodide with iodate in the presence of hydrochloric acid followed by VA-LLME of the ion-pair formed between ICl2(-) and Astra Phloxine reagent (AP) and subsequent absorbance measurement at 555nm. The appropriate experimental conditions were investigated and found to be: 5mL of sample, 0.27molL(-)(1) HCl, 0.027mmolL(-1) KIO3 as the oxidation agent, 250?L of extraction mixture containing amyl acetate as the extraction solvent and carbon tetrachloride as the auxiliary solvent (1:1, v/v), 0.04mmolL(-1) AP reagent, vortex time: 20s at 3000rpm, centrifugation: 4min at 3000rpm. The calibration plot was linear in the range 16.9-169?g L(-1) of iodide, with a correlation coefficient (R(2)) of 0.996, and the relative standard deviation ranged from 1.9 to 5.7%. The limit of detection (LOD) and limit of quantification (LOQ) were 1.75 and 6.01?gL(-)(1) of iodide, respectively. The suggested procedure was applied for determination of iodide in real mineral water samples. PMID:26717821

  1. Water-in-ionic liquid microemulsion formation in solvent mixture of aprotic and protic imidazolium-based ionic liquids.

    PubMed

    Kusano, Takumi; Fujii, Kenta; Hashimoto, Kei; Shibayama, Mitsuhiro

    2014-10-14

    We report that water-in-ionic liquid microemulsions (MEs) are stably formed in an organic solvent-free system, i.e., a mixture of aprotic (aIL) and protic (pIL) imidazolium-based ionic liquids (ILs) containing the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT). Structural investigations using dynamic light, small-angle X-ray, and small-angle neutron scatterings were performed for MEs formed in mixtures of aprotic 1-octyl-3-methylimidazolium ([C8mIm(+)]) and protic 1-alkylimidazolium ([CnImH(+)], n = 4 or 8) IL with a common anion, bis(trifluoromethanesulfonyl)amide ([TFSA(-)]). It was found that the ME structure strongly depends on the mixing composition of the aIL/pIL in the medium. The ME size appreciably increases with increasing pIL content in both [C8mIm(+)][TFSA(-)]/[C8ImH(+)][TFSA(-)] and [C8mIm(+)][TFSA(-)]/[C4ImH(+)][TFSA(-)] mixtures. The size is larger for the n = 8 system than that for the n = 4 system. These results indicate that the shell part of MEs is composed of both AOT and pIL cation, and the ME size can be tuned by pIL content in the aIL/pIL mixtures. PMID:25226398

  2. Air-Assisted Liquid Liquid-Microextraction for the Analysis of Fungicides from Environmental Water and Juice Samples.

    PubMed

    Wu, Shiju; Jin, Tingting; Cheng, Jing; Zhou, Hongbin; Cheng, Min

    2015-07-01

    In this work, a rapid method based on air-assisted liquid liquid microextraction (AALLME) was developed for the determination of three fungicides (azoxystrobin, diethofencarb and pyrimethanil) in water and juice samples. A narrow-neck glass tube was made to facilitate collection of the low-density extractant. The mixture of extractant and sample solution is rapidly sucked into a 5-mL glass syringe and then is injected into the narrow-neck glass tube and the procedure is repeated six times. A homogeneous solution was formed and then with the continuous injection of air by a 20-mL glass syringe, phase separation happened and the extractant was collected on the top of the sample solution. No centrifugation separation step was involved. It took only 90 s to complete the pretreatment process. The influence of main factors on the extraction efficiency is studied. Under optimal conditions, enrichment factors for the three fungicides varied from 145 to 178. The limits of detection for azoxystrobin, diethofencarb and pyrimethanil were 0.08, 0.16 and 0.25 µg L(-1), respectively. Reasonable relative recoveries were varied from 72.3 to 108.0%. And satisfactory intra-assay (5.3-6.2%, n = 6) and inter-assay (6.8-9.3%, n = 6) precision illustrated good performance of the analytical procedure. PMID:25355900

  3. The Structure of Liquid Water Emerging from the Vibrational Spectroscopy: Interpretation with QED Theory

    E-print Network

    A. De Ninno; E. Del Giudice; L. Gamberale; A. Congiu Castellano

    2013-10-02

    We report an analysis of the stretching peak appearing in the IR experimental spectra of liquid water. In the literature, ATR-IR spectroscopic measurements were repeatedly performed in a wide range of temperature and gave rise to a lively debate among scientists. In particular a two components model related to H-bond complexes of different strength have been proposed in order to justify the existence of two types of molecules as it appears from the spectroscopic data. At the opposite, Molecular Dynamics simulations support a multistate (continuum) system of H bond having different strength giving rise to a (locally) tetrahedral description of liquid water. We will show that liquid water is a quantum two-level system according to the predictions of Quantum Electrodynamics (QED) and that several features (the asymmetric band profile, the existence of an isosbestic point and the modifications of the vibrational stretching band with the temperature) cannot be fully justified in the realm of a classical picture. In particular the differences of energy and entropy between the two phases are estimated from the experimental data and compared with the prediction of QED showing a remarkable agreement. The behavior of water near hydrophilic surfaces is also discussed and several feature of the so called Exclusion Zone observed by several authors are evaluated according to the two level system model.

  4. Transient Liquid Water as a Mechanism for Induration of Soil Crusts on Mars

    NASA Technical Reports Server (NTRS)

    Landis, G. A.; Blaney, D.; Cabrol, N.; Clark, B. C.; Farmer, J.; Grotzinger, J.; Greeley, R.; McLennan, S. M.; Richter, L.; Yen, A.

    2004-01-01

    The Viking and the Mars Exploration Rover missions observed that the surface of Mars is encrusted by a thinly cemented layer tagged as "duricrust". A hypothesis to explain the formation of duricrust on Mars should address not only the potential mechanisms by which these materials become cemented, but also the textural and compositional components of cemented Martian soils. Elemental analyzes at five sites on Mars show that these soils have sulfur content of up to 4%, and chlorine content of up to 1%. This is consistent with the presence of sulfates and halides as mineral cements. . For comparison, the rock "Adirondack" at the MER site, after the exterior layer was removed, had nearly five times lower sulfur and chlorine content , and the Martian meteorites have ten times lower sulfur and chlorine content, showing that the soil is highly enriched in the saltforming elements compared with rock.Here we propose two alternative models to account for the origin of these crusts, each requiring the action of transient liquid water films to mediate adhesion and cementation of grains. Two alternative versions of the transient water hypothesis are offered, a top down hypothesis that emphasizes the surface deposition of frost, melting and downward migration of liquid water and a bottom up alternative that proposes the presence of interstitial ice/brine, with the upward capillary migration of liquid water.

  5. Estimation of Interfacial Tension between Organic Liquid Mixtures and Water

    SciTech Connect

    Yoon, Hongkyu; Oostrom, Martinus; Werth, Charles J.

    2009-10-15

    Knowledge of IFT values for chemical mixtures helps guide the design and analysis of various processes, including NAPL remediation with surfactants or alcohol flushing, enhanced oil recovery, and chemical separation technologies, yet available literature values are sparse. A comprehensive comparison of thermodynamic and empirical models for estimating interfacial tension (IFT) of organic chemical mixtures with water is conducted, mainly focusing on chlorinated organic compounds for 14 ternary, three quaternary, and one quinary systems. Emphasis is placed on novel results for systems with three and four organic chemical compounds, and for systems with composite organic compounds like lard oil and mineral oil. Seven models are evaluated: the ideal and nonideal monolayer models (MLID and MLNID), the ideal and nonideal mutual solubility models (MSID and MSNID), an empirical model for ternary systems (EM), a linear mixing model based on mole fractions (LMMM), and a newly developed linear mixing model based on volume fractions of organic mixtures (LMMV) for higher order systems. The two ideal models (MLID and MSID) fit ternary systems of chlorinated organic compounds without surface active compounds relatively well. However, both ideal models did not perform well for the mixtures containing a surface active compound. However, for these systems, both the MLNID and MSNID models matched the IFT data well. It is shown that the MLNID model with a surface coverage value (0.00341 mmol/m2) obtained in this study can practically be used for chlorinated organic compounds. The LMMM results in poorer estimates of the IFT as the difference in IFT values of individual organic compounds in a mixture increases. The EM, with two fitting parameters, provided accurate results for all 14 ternary systems including composite organic compounds. The new LMMV method for quaternary and higher component systems was successfully tested. This study shows that the LMMV may be able to be used for higher component systems and it can be easily incorporated into compositional multiphase flow models using only parameters from ternary systems.

  6. Determination of selected azaarenes in water by bonded-phase extraction and liquid chromatography

    USGS Publications Warehouse

    Steinheimer, T.R.; Ondrus, M.G.

    1986-01-01

    A method for the rapid and simple quantitative determination of quinoline, isoquinoline, and five selected three-ring azaarenes in water has been developed. The azaarene fraction is separated from its carbon analogues on n-octadecyl packing material by edition with acidified water/acetonitrile. Concentration as great as 1000-fold is achieved readily. Instrumental analysis involves high-speed liquid chromatography on flexible-walled, wide-bore columns with fluorescence and ultraviolet detection at several wavelengths employing filter photometers in series. Method-validation data is provided as azaarene recovery efficiency from fortified samples. Distilled water, river water, contaminated ground water, and secondary-treatment effluent have been tested. Recoveries at part-per-billion levels are nearly quantitative for the three-ring compounds, but they decrease for quinoline and isoquinoline. ?? 1986 American Chemical Society.

  7. Understanding lignin treatment in dialkylimidazolium-based ionic liquid-water mixtures.

    PubMed

    Yan, Bing; Li, Kunlan; Wei, Ligang; Ma, Yingchong; Shao, Guolin; Zhao, Deyang; Wan, Wenying; Song, Lili

    2015-11-01

    The treatment of enzymatically hydrolyzed lignin (EHL) in dialkylimidazolium-based ionic liquid (IL)-water mixtures (50-100wt% IL content) was investigated at 150°C for 3h. pH, IL type, and IL content were found to greatly influence the degradation of lignin and the structure of regenerated lignin. 1-Butyl-3-methylimidazolium methylsulfonate-water mixtures with low pH facilitated lignin depolymerization but destroyed the regenerated lignin substructure. Regenerated lignin with low molecular weight and narrow polydispersity index (2.2-7.7) was obtained using a 1-butyl-3-methylimidazolium acetate-based system. Water addition inhibited lignin depolymerization at 50-100wt% IL content, except for 70wt% 1-butyl-3-methylimidazolium chloride-water mixture. Compared with pure IL treatment, obvious differences were observed in the breakdown of inter-unit linkages and ratio of syringyl to guaiacyl units in regenerated lignin with IL-water treatment. PMID:26282782

  8. How does confinement affect the structure and dynamics of water and other liquids?

    NASA Astrophysics Data System (ADS)

    Milischuk, Anatoli; Ladanyi, Branka

    2013-03-01

    We studied the effects of confinement on static and dynamical properties of liquids including water, acetonitrile, and benzene in amorphous silica nanopores in equilibrium with the bulk liquid at ambient conditions. The model pores are approximately cylindrical, with diameters ranging from 20 to 40 Å. The filled pores are prepared using grand canonical Monte Carlo simulation and molecular dynamics simulation is used to calculate liquid structure and dynamics. Our studies of dynamics included translational mean squared displacements, orientational time correlations, and survival probabilities in interfacial shells. We also studied polarizability anisotropy time correlations that are related to experimentally observed optical Kerr effect response functions. We found that there is layering and preferential orientational ordering of solvent molecules in the interfacial region. Molecular translational and rotational mobility is reduced in the layers near the interface. Confinement leads to slowdown of the polarizability anisotropy relaxation in agreement with experimental findings.

  9. In situ separation of root hydraulic redistribution of soil water from liquid and vapor transport

    SciTech Connect

    Warren, Jeffrey; Brooks, J Renee; Dragila, Maria; Meinzer, Rick

    2011-01-01

    Nocturnal increases in water potential ( ) and water content (WC) in the upper soil profile are often attributed to root water efflux into the soil, a process termed hydraulic lift or hydraulic redistribution (HR). We have previously reported HR values up to ~0.29 mm day-1 in the upper soil for a seasonally dry old-growth ponderosa pine site. However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the diurnal patterns in WC, confounding efforts to determine the actual magnitude of HR. In this study, we estimated liquid (Jl) and vapor (Jv) soil water fluxes and their impacts on quantifying HR in situ by applying existing data sets of , WC, temperature (T) and soil physical properties to soil water transport equations. Under moist conditions, Jl between layers was estimated to be larger than necessary to account for measured nocturnal increases in WC of upper soil layers. However, as soil drying progressed unsaturated hydraulic conductivity declined rapidly such that Jl was irrelevant (< 2E-06 cm hr-1 at 0-60 cm depths) to total water flux by early August. In surface soil at depths above 15 cm, large T fluctuations can impact Jv leading to uncertainty concerning the role, if any, of HR in nocturnal WC dynamics. Vapor flux was estimated to be the highest at the shallowest depths measured (20 - 30 cm) where it could contribute up to 40% of hourly increases in nocturnal soil moisture depending on thermal conditions. While both HR and net soil water flux between adjacent layers contribute to WC in the 15-65 cm soil layer, HR was the dominant process and accounted for at least 80% of the diurnal increases in WC. While the absolute magnitude of HR is not easily quantified, total diurnal fluctuations in upper soil water content can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total ecosystem water flux.

  10. Linking Europa's plume activity to tides, tectonics, and liquid water

    NASA Astrophysics Data System (ADS)

    Rhoden, Alyssa Rose; Hurford, Terry A.; Roth, Lorenz; Retherford, Kurt

    2015-06-01

    Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30-80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus. To do this, we determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa's orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. The addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across the fractures suggests that the plumes would be best observed earlier in the orbit (true anomaly ?120°). Our results indicate that Europa's plumes, if confirmed, differ in many respects from the Enceladean plumes and that either active fractures or volatile sources are rare.

  11. Sum-frequency generation analyses of the structure of water at amphoteric SAM-liquid water interfaces.

    PubMed

    Nomura, Kouji; Nakaji-Hirabayashi, Tadashi; Gemmei-Ide, Makoto; Kitano, Hiromi; Noguchi, Hidenori; Uosaki, Kohei

    2014-09-01

    Surfaces of both a cover glass and the flat plane of a semi-cylindrical quartz prism were modified with a mixture of positively and negatively charged silane coupling reagents (3-aminopropyltriethoxysilane (APTES) and 3-(trihydroxysilyl)propylmethylphosphonate (THPMP), respectively). The glass surface modified with a self-assembled monolayer (SAM) prepared at a mixing ratio of APTES:THPMP=4:6 was electrically almost neutral and was resistant to non-specific adsorption of proteins, whereas fibroblasts gradually adhered to an amphoteric (mixed) SAM surface probably due to its stiffness, though the number of adhered cells was relatively small. Sum frequency generation (SFG) spectra indicated that total intensity of the OH stretching region (3000-3600cm(-1)) for the amphoteric SAM-modified quartz immersed in liquid water was smaller than those for the positively and negatively charged SAM-modified quartz prisms and a bare quartz prism in contact with liquid water. These results suggested that water molecules at the interface of water and an amphoteric SAM-modified quartz prism are not strongly oriented in comparison with those at the interface of a lopsidedly charged SAM-modified quartz prism and bare quartz. The importance of charge neutralization for the anti-biofouling properties of solid materials was strongly suggested. PMID:25001187

  12. Remote measurements of ozone, water vapor and liquid water content, and vertical profiles of temperature in the lower troposphere

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Gary, B. L.; Shumate, M. S.

    1983-01-01

    Several advanced atmospheric remote sensing systems developed at the Jet Propulsion Laboratory were demonstrated under various field conditions to determine how useful they would be for general use by the California Air Resources Board and local air quality districts. One of the instruments reported on is the Laser Absorption Spectrometer (LAS). It has a pair of carbon dioxide lasers with a transmitter and receiver and can be flown in an aircraft to measure the column abundance of such gases as ozone. From an aircraft, it can be used to rapidly survey a large region. The LAS is usually operated from an aircraft, although it can also be used at a fixed location on the ground. Some tests were performed with the LAS to measure ozone over a 2-km horizontal path. Another system reported on is the Microwave Atmospheric Remote Sensing System (MARS). It is tuned to microwave emissions from water vapor, liquid water, and oxygen molecules (for atmospheric temperature). It can measure water vapor and liquid water in the line-of-sight, and can measure the vertical temperature profile.

  13. Characterization of the Local Structure in Liquid Water by Various Order Parameters.

    PubMed

    Duboué-Dijon, Elise; Laage, Damien

    2015-07-01

    A wide range of geometric order parameters have been suggested to characterize the local structure of liquid water and its tetrahedral arrangement, but their respective merits have remained elusive. Here, we consider a series of popular order parameters and analyze molecular dynamics simulations of water, in the bulk and in the hydration shell of a hydrophobic solute, at 298 and 260 K. We show that these parameters are weakly correlated and probe different distortions, for example the angular versus radial disorders. We first combine these complementary descriptions to analyze the structural rearrangements leading to the density maximum in liquid water. Our results reveal no sign of a heterogeneous mixture and show that the density maximum arises from the depletion in interstitial water molecules upon cooling. In the hydration shell of the hydrophobic moiety of propanol, the order parameters suggest that the water local structure is similar to that in the bulk, with only a very weak depletion in ordered configurations, thus confirming the absence of any iceberg-type structure. Finally, we show that the main structural fluctuations that affect water reorientation dynamics in the bulk are angular distortions, which we explain by the jump hydrogen-bond exchange mechanism. PMID:26054933

  14. Liquid-Water Uptake and Removal in PEM Fuel-Cell Components

    SciTech Connect

    Das, Prodip K.; Gunterman, Haluna P.; Kwong, Anthony; Weber, Adam Z.

    2011-09-23

    Management of liquid water is critical for optimal fuel-cell operation, especially at low temperatures. It is therefore important to understand the wetting properties and water holdup of the various fuel-cell layers. While the gas-diffusion layer is relatively hydrophobic and exhibits a strong intermediate wettability, the catalyst layer is predominantly hydrophilic. In addition, the water content of the ionomer in the catalyst layer is lower than that of the bulk membrane, and is affected by platinum surfaces. Liquid-water removal occurs through droplets on the surface of the gas-diffusion layer. In order to predict droplet instability and detachment, a force balance is used. While the pressure or drag force on the droplet can be derived, the adhesion or surface-tension force requires measurement using a sliding-angle approach. It is shown that droplets produced by forcing water through the gas-diffusion layer rather than placing them on top of it show much stronger adhesion forces owing to the contact to the subsurface water.

  15. Identification of Clathrate Hydrates, Hexagonal Ice, Cubic Ice, and Liquid Water in Simulations: the CHILL+ Algorithm.

    PubMed

    Nguyen, Andrew H; Molinero, Valeria

    2015-07-23

    Clathrate hydrates and ice I are the most abundant crystals of water. The study of their nucleation, growth, and decomposition using molecular simulations requires an accurate and efficient algorithm that distinguishes water molecules that belong to each of these crystals and the liquid phase. Existing algorithms identify ice or clathrates, but not both. This poses a challenge for cases in which ice and hydrate coexist, such as in the synthesis of clathrates from ice and the formation of ice from clathrates during self-preservation of methane hydrates. Here we present an efficient algorithm for the identification of clathrate hydrates, hexagonal ice, cubic ice, and liquid water in molecular simulations. CHILL+ uses the number of staggered and eclipsed water-water bonds to identify water molecules in cubic ice, hexagonal ice, and clathrate hydrate. CHILL+ is an extension of CHILL (Moore et al. Phys. Chem. Chem. Phys. 2010, 12, 4124-4134), which identifies hexagonal and cubic ice but not clathrates. In addition to the identification of hydrates, CHILL+ significantly improves the detection of hexagonal ice up to its melting point. We validate the use of CHILL+ for the identification of stacking faults in ice and the nucleation and growth of clathrate hydrates. To our knowledge, this is the first algorithm that allows for the simultaneous identification of ice and clathrate hydrates, and it does so in a way that is competitive with respect to existing methods used to identify any of these crystals. PMID:25389702

  16. Characterization of the Local Structure in Liquid Water by Various Order Parameters

    PubMed Central

    2015-01-01

    A wide range of geometric order parameters have been suggested to characterize the local structure of liquid water and its tetrahedral arrangement, but their respective merits have remained elusive. Here, we consider a series of popular order parameters and analyze molecular dynamics simulations of water, in the bulk and in the hydration shell of a hydrophobic solute, at 298 and 260 K. We show that these parameters are weakly correlated and probe different distortions, for example the angular versus radial disorders. We first combine these complementary descriptions to analyze the structural rearrangements leading to the density maximum in liquid water. Our results reveal no sign of a heterogeneous mixture and show that the density maximum arises from the depletion in interstitial water molecules upon cooling. In the hydration shell of the hydrophobic moiety of propanol, the order parameters suggest that the water local structure is similar to that in the bulk, with only a very weak depletion in ordered configurations, thus confirming the absence of any iceberg-type structure. Finally, we show that the main structural fluctuations that affect water reorientation dynamics in the bulk are angular distortions, which we explain by the jump hydrogen-bond exchange mechanism. PMID:26054933

  17. Prognostic precipitation with three liquid water classes in the ECHAM5-HAM GCM

    NASA Astrophysics Data System (ADS)

    Sant, V.; Posselt, R.; Lohmann, U.

    2015-08-01

    A new parameterization with three prognostic liquid water classes was implemented into the general circulation model (GCM) ECHAM5 with the aerosol module HAM in order to improve the global representation of rain formation in marine stratiform clouds. The additionally introduced drizzle class improves the physical representation of the droplet spectrum and, more importantly, improves the microphysical processes relevant for precipitation formation compared to the standard parameterization. In order to avoid a mismatch of the liquid and ice phase, a prognostic treatment of snow has been introduced too. This has a significant effect on the amount and altitude of ice clouds, which in turn affects not only the in- and outgoing radiation but also the parameterized collection rates. With the introduction of a prognostic precipitation scheme, a more realistic representation of both liquid and ice phase large-scale precipitation is achieved compared to a diagnostic treatment. An encouraging finding is that with the prognostic treatment the increase of the liquid water path in response to anthropogenic aerosols is reduced by about 25 %. Although the total net radiative forcing is decreased from -1.3±0.3 to -1.6±0.3 W m-2 from the control to the prognostic model version, the difference is within the interannual variability. Altogether the results suggest that the treatment of precipitation in global circulation models has not only a significant influence on the phase of clouds and their conversion rates, but also hints towards uncertainties related to a prognostic precipitation scheme.

  18. Covalency of hydrogen bonds in liquid water can be probed by proton nuclear magnetic resonance experiments

    PubMed Central

    Elgabarty, Hossam; Khaliullin, Rustam Z.; Kühne, Thomas D.

    2015-01-01

    The concept of covalency is widely used to describe the nature of intermolecular bonds, to explain their spectroscopic features and to rationalize their chemical behaviour. Unfortunately, the degree of covalency of an intermolecular bond cannot be directly measured in an experiment. Here we established a simple quantitative relationship between the calculated covalency of hydrogen bonds in liquid water and the anisotropy of the proton magnetic shielding tensor that can be measured experimentally. This relationship enabled us to quantify the degree of covalency of hydrogen bonds in liquid water using the experimentally measured anisotropy. We estimated that the amount of electron density transferred between molecules is on the order of 10??m while the stabilization energy due to this charge transfer is ?15?kJ?mol?1. The physical insight into the fundamental nature of hydrogen bonding provided in this work will facilitate new studies of intermolecular bonding in a variety of molecular systems. PMID:26370179

  19. Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo

    E-print Network

    Andrea Zen; Ye Luo; Guglielmo Mazzola; Leonardo Guidoni; Sandro Sorella

    2015-04-21

    Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous Density Functional Theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab-initio simulations of complex chemical systems.

  20. Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Zen, Andrea; Luo, Ye; Mazzola, Guglielmo; Guidoni, Leonardo; Sorella, Sandro

    2015-04-01

    Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems.

  1. The Effect of van der Waals Interactions on the Structure of Liquid Water.

    NASA Astrophysics Data System (ADS)

    Distasio, Robert, Jr.; Li, Zhaofeng; Car, Roberto

    2012-02-01

    In this work, we demonstrate the importance of including van der Waals (vdW) interactions in the theoretical prediction of the structure of liquid water. These effects are investigated by computing and analyzing the oxygen-oxygen, oxygen-hydrogen, and hydrogen-hydrogen radial distribution functions (RDFs) obtained from highly accurate ab initiomolecular dynamic simulations that explicitly account for vdW interactions. In particular, we utilize an efficient order(N) algorithmic implementation of the self-consistent energy and analytical forces of the density functional based vdW correction proposed by Tkatchenko and Scheffler (PRL 102, 073005 (2009)) to demonstrate the importance of vdW interactions in obtaining RDFs that are in close agreement with experiment. In addition, we also provide an analysis of finite size effects in vdW-based liquid water simulations as well as a comparison to several other competitive theoretical methods for treating vdW interactions.

  2. Computing the dielectric constant of liquid water at constant dielectric displacement

    E-print Network

    Zhang, Chao

    2015-01-01

    The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement D. The method to constrain the electric displacement is the finite temperature classical variant of the constant-D method developed by Stengel, Spaldin and Vanderbilt (Nat. Phys. 2009, 5: 304). There is also a modification of this scheme imposing fixed values of the macroscopic field E. The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at D = 0 and E = 0 and two from the variation of polarization with finite D and E. It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies however, with constant D calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polar...

  3. Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo

    SciTech Connect

    Zen, Andrea; Luo, Ye Mazzola, Guglielmo Sorella, Sandro; Guidoni, Leonardo

    2015-04-14

    Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems.

  4. Aggregation behavior and total miscibility of fluorinated ionic liquids in water.

    PubMed

    Pereiro, Ana B; Araújo, João M M; Teixeira, Fabiana S; Marrucho, Isabel M; Piñeiro, Manuel M; Rebelo, Luis Paulo N

    2015-02-01

    In this work, novel and nontoxic fluorinated ionic liquids (FILs) that are totally miscible in water and could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements, and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry, and surface tension measurements in order to study various thermodynamic and surface properties that demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures. PMID:25580898

  5. Shock Hugoniot equations of state for binary water-alcohol liquid mixtures

    NASA Astrophysics Data System (ADS)

    Moore, David; Bolme, Cynthia; Brown, Kathryn; McGrane, Shawn; Schulze, Peter

    2015-06-01

    Shock Hugoniot data were obtained using laser generated shock and ultrafast dynamic ellipsometry (UDE) methods for several non-ideal water-alcohol liquid mixtures, using methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and t-butanol (a.k.a., 2-methyl-2-propanol or tert-butanol). The sound speeds of the mixtures were obtained using Brillouin scattering when not available in the literature. The shock and particle velocities obtained from the UDE data were compared to expectations of the universal liquid Hugoniot (ULH) and to literature shock (plate impact) data where available. The shock Hugoniot trends for all these mixtures, represented as deviations from predictions of the ULH, versus fraction of alcohol are quite similar to each other and suggest that complex hydrogen bonding networks in water-alcohol mixtures alter the compressibility of the mixtures. Data and trends will be presented. LA-UR-15-20328.

  6. An eight-month sample of marine stratocumulus cloud fraction, albedo, and integrated liquid water

    NASA Technical Reports Server (NTRS)

    Fairall, C. W.; Hare, J. E.; Snider, J. B.

    1990-01-01

    Surface-meteorology and shortwave/longwave irradiance measurements taken on the northwest tip of San Nicolas Island off the coast of Southern California from March through October 1987 are analyzed. Experimental details are summarized, and shortwave cloud-radiation parameterization is outlined with emphasis on a shortwave algorithm. Frequency distributions indicate the stratocumulus clouds at the island have a cloud base on the order of 400 m, an integrated liquid water content of 75 g/sq m, and an albedo of 0.55 with substantial diurnal variations. The longwave parameterization for cloud fraction is also considered, and it is noted that using these models for downward longwave and shortwave irradiances, cloud fraction, integrated liquid water content, and albedo are deduced from the data.

  7. Photoinduced Four-State Three-Step Ordering Transformation of Photochromic Terthiophene at a Liquid/Solid Interface Based on Two Principles: Photochromism and Polymorphism.

    PubMed

    Yokoyama, Soichi; Hirose, Takashi; Matsuda, Kenji

    2015-06-16

    We have investigated photoinduced ordering transformation of a photochromic terthiophene derivative by scanning tunneling microscopy (STM) at the trichlorobenzene (TCB)/highly oriented pyrolytic graphite (HOPG) interface. The open-ring and annulated isomers of the terthiophene formed two-dimensional molecular orderings with different patterns while the closed-ring isomer did not form any ordering. The ordering of the open-ring isomer exhibited polymorphism depending on the concentration of supernatant solution. Upon UV light irradiation to a solution of the open-ring isomer or the closed-ring isomer, ordering composed of the annulated isomer was irreversibly formed. Upon visible light irradiation or thermal stimulus to the closed-ring isomer, the two kinds of polymorph composed of the open-ring isomer were formed due to the polymorphism. By controlling photochromism and polymorphism among four states made of three photochemical isomers, four-state three-step transformation was achieved by in situ photoirradiation from a solution of the closed-ring isomer (no ordering) into the ordering composed of the open-ring isomer (ordering ? and ?) followed by the orderings composed of the annulated isomer (ordering ?). PMID:26005903

  8. Low-Dimensional Water on Ru(0001); Model System for X-ray Absorption Spectroscopy Studies of Liquid Water

    SciTech Connect

    Nordlund, D.; Ogasawara, H.; Andersson, K.J.; Tatarkhanov, M.; Salmeron, M.; Pettersson, L. G. M.; Nilsson, A.

    2009-05-11

    We present an x-ray absorption spectroscopy results for fully broken to a complete H-bond network of water molecules on Ru(0001) by varying the morphology from isolated water molecules via two-dimensional clusters to a fully covered monolayer as probed by scanning tunneling microscopy. The sensitivity of x-ray absorption to the symmetry of H-bonding is further elucidated for the amino (-NH{sub 2}) group in glycine adsorbed on Cu(110) where the E-vector is parallel either to the NH donating an H-bond or to the non-H-bonded NH. The results give further evidence for the interpretation of the various spectral features of liquid water and for the general applicability of x-ray absorption spectroscopy to analyze H-bonded systems.

  9. Low-Dimensional Water on Ru(0001)Model System for X-ray Absorption Spectroscopy Studies of Liquid Water

    SciTech Connect

    Nordlund, D

    2012-02-14

    We present an x-ray absorption spectroscopy results for fully broken to a complete H-bond network of water molecules on Ru(0001) by varying the morphology from isolated water molecules via two-dimensional clusters to a fully covered monolayer as probed by scanning tunneling microscopy. The sensitivity of x-ray absorption to the symmetry of H-bonding is further elucidated for the amino (-NH{sub 2}) group in glycine adsorbed on Cu(110) where the E-vector is parallel either to the NH donating an H-bond or to the non-H-bonded NH. The results give further evidence for the interpretation of the various spectral features of liquid water and for the general applicability of x-ray absorption spectroscopy to analyze H-bonded systems.

  10. Influence of liquid density on the parametric shape instability of sonoluminescence bubbles in water and sulfuric acid

    NASA Astrophysics Data System (ADS)

    Godínez, F. A.; Navarrete, M.

    2011-07-01

    Parametric shape instability of sonoluminescing argon bubbles in water and aqueous H2SO4 was numerically analyzed considering gas and liquid density variations. The employed model couples Gilmore, Tait (liquid) and van der Waals (gas) equations to simulate radial dynamics and density changes, respectively. Shape stability-instability zones in the Pa-R0 space resulted from a linear stability analysis. For the argon-water and argon-water-acid systems, numerical results indicate a rapid rise in both gas and liquid densities during final stages of bubble implosion which result in a stabilizing effect on the parametric instability.

  11. Response of soybean rhizosphere communities to human hygiene water addition as determined by community level physiological profiling (CLPP) and terminal restriction fragment length polymorphism (TRFLP) analysis

    NASA Technical Reports Server (NTRS)

    Kerkhof, L.; Santoro, M.; Garland, J.

    2000-01-01

    In this report, we describe an experiment conducted at Kennedy Space Center in the biomass production chamber (BPC) using soybean plants for purification and processing of human hygiene water. Specifically, we tested whether it was possible to detect changes in the root-associated bacterial assemblage of the plants and ultimately to identify the specific microorganism(s) which differed when plants were exposed to hygiene water and other hydroponic media. Plants were grown in hydroponics media corresponding to four different treatments: control (Hoagland's solution), artificial gray water (Hoagland's+surfactant), filtered gray water collected from human subjects on site, and unfiltered gray water. Differences in rhizosphere microbial populations in all experimental treatments were observed when compared to the control treatment using both community level physiological profiles (BIOLOG) and molecular fingerprinting of 16S rRNA genes by terminal restriction fragment length polymorphism analysis (TRFLP). Furthermore, screening of a clonal library of 16S rRNA genes by TRFLP yielded nearly full length SSU genes associated with the various treatments. Most 16S rRNA genes were affiliated with the Klebsiella, Pseudomonas, Variovorax, Burkholderia, Bordetella and Isosphaera groups. This molecular approach demonstrated the ability to rapidly detect and identify microorganisms unique to experimental treatments and provides a means to fingerprint microbial communities in the biosystems being developed at NASA for optimizing advanced life support operations.

  12. How do hybrid functionals, dispersion interactions and quantum nuclei affect the structure of liquid water?

    NASA Astrophysics Data System (ADS)

    Li, Zhaofeng; Distasio, Robert A., Jr.; Car, Roberto; Wu, Xifan

    2011-03-01

    We report ab-initio molecular dynamics simulations of liquid water at STP and at the volume corresponding to experimental equilibrium density. These simulations are based on the hybrid functional PBE0 for the electrons and include approximate dispersion interactions according to Ref. Nuclear quantum corrections were included as estimated by Ref. We find that all of these components are important to significantly improve the agreement of the simulated structure with recent experimental analyses based on neutron and X-ray diffraction.

  13. IR and SFG vibrational spectroscopy of the water bend in the bulk liquid and at the liquid-vapor interface, respectively

    NASA Astrophysics Data System (ADS)

    Ni, Yicun; Skinner, J. L.

    2015-07-01

    Vibrational spectroscopy of the water bending mode has been investigated experimentally to study the structure of water in condensed phases. In the present work, we calculate the theoretical infrared (IR) and sum-frequency generation (SFG) spectra of the HOH bend in liquid water and at the water liquid/vapor interface using a mixed quantum/classical approach. Classical molecular dynamics simulation is performed by using a recently developed water model that explicitly includes three-body interactions and yields a better description of the water surface. Ab-initio-based transition frequency, dipole, polarizability, and intermolecular coupling maps are developed for the spectral calculations. The calculated IR and SFG spectra show good agreement with the experimental measurements. In the theoretical imaginary part of the SFG susceptibility for the water liquid/vapor interface, we find two features: a negative band centered at 1615 cm-1 and a positive band centered at 1670 cm-1. We analyze this spectrum in terms of the contributions from molecules in different hydrogen-bond classes to the SFG spectral density and also compare to SFG results for the OH stretch. SFG of the water bending mode provides a complementary picture of the heterogeneous hydrogen-bond configurations at the water surface.

  14. IR and SFG vibrational spectroscopy of the water bend in the bulk liquid and at the liquid-vapor interface, respectively.

    PubMed

    Ni, Yicun; Skinner, J L

    2015-07-01

    Vibrational spectroscopy of the water bending mode has been investigated experimentally to study the structure of water in condensed phases. In the present work, we calculate the theoretical infrared (IR) and sum-frequency generation (SFG) spectra of the HOH bend in liquid water and at the water liquid/vapor interface using a mixed quantum/classical approach. Classical molecular dynamics simulation is performed by using a recently developed water model that explicitly includes three-body interactions and yields a better description of the water surface. Ab-initio-based transition frequency, dipole, polarizability, and intermolecular coupling maps are developed for the spectral calculations. The calculated IR and SFG spectra show good agreement with the experimental measurements. In the theoretical imaginary part of the SFG susceptibility for the water liquid/vapor interface, we find two features: a negative band centered at 1615 cm(-1) and a positive band centered at 1670 cm(-1). We analyze this spectrum in terms of the contributions from molecules in different hydrogen-bond classes to the SFG spectral density and also compare to SFG results for the OH stretch. SFG of the water bending mode provides a complementary picture of the heterogeneous hydrogen-bond configurations at the water surface. PMID:26156483

  15. Analysis and Calibration of CRF Raman Lidar Cloud Liquid Water Measurements

    SciTech Connect

    Turner, D.D. Whiteman, D.N. Russo, F.

    2007-10-31

    The Atmospheric Radiation Measurement (ARM) Raman lidar (RL), located at the Southern Great Plains (SGP) Climate Research Facility (CRF), is a unique state-of-the-art active remote sensor that is able to measure profiles of water vapor, aerosol, and cloud properties at high temporal and vertical resolution throughout the diurnal cycle. In October 2005, the capability of the RL was extended by the addition of a new detection channel that is sensitive to the Raman scattering of liquid water. This new channel permits the system, in theory, to measure profiles of liquid water content (LWC) by the RL. To our knowledge, the ARM RL is the only operation lidar with this capability. The liquid water Raman backscattering cross-section is a relatively weak and spectrally broad feature, relative to the water vapor Raman backscatter signal. The wide bandpass required to achieve reasonable signal-to-noise in the liquid water channel essentially eliminates the ability to measure LWC profiles during the daytime in the presence of large solar background, and thus all LWC observations are nighttime only. Additionally, the wide bandpass increases the probability that other undesirable signals, such as fluorescence from aerosols, may contaminate the observation. The liquid water Raman cross-section has a small amount of overlap with the water vapor Raman cross-section, and thus there will be a small amount of ‘cross-talk’ between the two signals, with water vapor contributing a small amount of signal to the LWC observation. And finally, there is significant uncertainty in the actual strength of the liquid water Raman cross-section in the literature. The calibrated LWC profiles, together with the coincident cloud backscatter observations also made by the RL, can be used to derive profiles of cloud droplet effective radius. By combining these profiles of effective radius in the lower portion of the cloud with the aerosol extinction measurements made below the cloud by the RL, the first aerosol indirect effect can be investigated using a single instrument, thereby reducing the uncertainty associated with aligning the different sampling periods and fields of view of multiple instruments. We have applied a “first principles” calibration to the LWC profiles. This approach requires that the relative differences in optical efficiency between the water vapor and liquid water channels be known; this relative difference is easily computed using the efficiency values of the beam splitters and interference filters in the lidar that were provided by the vendors of these components. The first principles approach then transfers the calibration from the water vapor mixing ratio to the LWC using the difference in the optical efficiency and an interpolated value of the liquid water Raman cross section from the literature, and the better established water vapor Raman cross section. After accounting for all known error sources, the vertical integral of LWC was compared against a similar value retrieved from a co-located ground-based infrared radiometer. The RL and infrared radiometer have significantly different fields of view; thus to compare the two sensors the data were averaged to 5 min intervals where only cloudy samples were included in the average of each. While there is fair scatter in the data (r=0.47), there is also a clear indication of a positive correlation between the infrared and the RL values. The value of the slope of the regression is 0.49, which indicates a tendency of the RL measurements to underestimate the total liquid amount with respect to the infrared retrieval. Research continues to investigate the source of the bias, but the most likely candidate is the large uncertainty in the liquid water Raman cross-section as there have been no direct measurements made of this parameter at the lidar’s laser wavelength of 355 nm. The calibrated LWC profile was then used together with the cloud backscatter coefficient profile from the RL to derive profiles of cloud droplet effective radius and cloud droplet number density. These profiles o

  16. Interaction between Arsenic Exposure from Drinking Water and Genetic Polymorphisms on Cardiovascular Disease in Bangladesh: A Prospective Case-Cohort Study

    PubMed Central

    Wu, Fen; Jasmine, Farzana; Kibriya, Muhammad G.; Liu, Mengling; Cheng, Xin; Parvez, Faruque; Islam, Tariqul; Ahmed, Alauddin; Rakibuz-Zaman, Muhammad; Jiang, Jieying; Roy, Shantanu; Paul-Brutus, Rachelle; Slavkovich, Vesna; Islam, Tariqul; Levy, Diane; VanderWeele, Tyler J.; Pierce, Brandon L.; Graziano, Joseph H.; Ahsan, Habibul

    2015-01-01

    Background: Epidemiologic data on genetic susceptibility to cardiovascular effects of arsenic exposure from drinking water are limited. Objective: We investigated whether the association between well-water arsenic and cardiovascular disease (CVD) differed by 170 single nucleotide polymorphisms (SNPs) in 17 genes related to arsenic metabolism, oxidative stress, inflammation, and endothelial dysfunction. Method: We conducted a prospective case-cohort study nested in the Health Effects of Arsenic Longitudinal Study, with a random subcohort of 1,375 subjects and 447 incident fatal and nonfatal cases of CVD. Well-water arsenic was measured in 2000 at baseline. The CVD cases, 56 of which occurred in the subcohort, included 238 coronary heart disease cases, 165 stroke cases, and 44 deaths due to other CVD identified during follow-up from 2000 to 2012. Results: Of the 170 SNPs tested, multiplicative interactions between well-water arsenic and two SNPs, rs281432 in ICAM1 (padj = 0.0002) and rs3176867 in VCAM1 (padj = 0.035), were significant for CVD after adjustment for multiple testing. Compared with those with GC or CC genotype in rs281432 and lower well-water arsenic, the adjusted hazard ratio (aHR) for CVD was 1.82 (95% CI: 1.31, 2.54) for a 1-SD increase in well-water arsenic combined with the GG genotype, which was greater than expected given aHRs of 1.08 and 0.96 for separate effects of arsenic and the genotype alone, respectively. Similarly, the joint aHR for arsenic and the rs3176867 CC genotype was 1.34 (95% CI: 0.95, 1.87), greater than expected given aHRs for their separate effects of 1.02 and 0.84, respectively. Conclusions: Associations between CVD and arsenic exposure may be modified by genetic variants related to endothelial dysfunction. Citation: Wu F, Jasmine F, Kibriya MG, Liu M, Cheng X, Parvez F, Islam T, Ahmed A, Rakibuz-Zaman M, Jiang J, Roy S, Paul-Brutus R, Slavkovich V, Islam T, Levy D, VanderWeele TJ, Pierce BL, Graziano JH, Ahsan H, Chen Y. 2015. Interaction between arsenic exposure from drinking water and genetic polymorphisms on cardiovascular disease in Bangladesh: a prospective case-cohort study. Environ Health Perspect 123:451–457;?http://dx.doi.org/10.1289/ehp.1307883 PMID:25575156

  17. Liquid water from first principles: The importance of exact exchange, dispersion interactions, and nuclear quantum effects

    NASA Astrophysics Data System (ADS)

    Distasio, Robert; Li, Zhaofeng; Santra, Biswajit; Wu, Xifan; Car, Roberto

    2013-03-01

    Quantitative agreement between theory and experiment on the structure of liquid water at ambient conditions has been quite difficult to achieve to date. In this work, we report that highly accurate ab initio molecular dynamics simulations of liquid water that account for exact exchange (via the hybrid PBE0 functional [PRB 79, 085102 (2009)]), dispersion interactions [PRL 102, 073005 (2009)], and nuclear quantum effects (presently approximated by a 30K increase in the simulation temperature) result in excellent agreement with experiments [PRL 101, 065502 (2008)]. The importance of each of these effects in the theoretical prediction of the structure of liquid water will be demonstrated by a detailed comparative analysis of the predicted and experimental oxygen-oxygen radial distribution functions. In addition, we will discuss the connection between the experimentally observed scattering intensity, I(k), and the final radial distribution function, g(r), via the structure and form factors. This work was supported by NSF CHE-0956500, DOE-DE- SC0005180, and DOE: DE-SC0008626.

  18. Emissions Prediction and Measurement for Liquid-Fueled TVC Combustor with and without Water Injection

    NASA Technical Reports Server (NTRS)

    Brankovic, A.; Ryder, R. C., Jr.; Hendricks, R. C.; Liu, N.-S.; Shouse, D. T.; Roquemore, W. M.

    2005-01-01

    An investigation is performed to evaluate the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid-fueled combustor that uses water injection for control of pollutant emissions. The experiment consists of a multisector, liquid-fueled combustor rig operated at different inlet pressures and temperatures, and over a range of fuel/air and water/fuel ratios. Fuel can be injected directly into the main combustion airstream and into the cavities. Test rig performance is characterized by combustor exit quantities such as temperature and emissions measurements using rakes and overall pressure drop from upstream plenum to combustor exit. Visualization of the flame is performed using gray scale and color still photographs and high-frame-rate videos. CFD simulations are performed utilizing a methodology that includes computer-aided design (CAD) solid modeling of the geometry, parallel processing over networked computers, and graphical and quantitative post-processing. Physical models include liquid fuel droplet dynamics and evaporation, with combustion modeled using a hybrid finite-rate chemistry model developed for Jet-A fuel. CFD and experimental results are compared for cases with cavity-only fueling, while numerical studies of cavity and main fueling was also performed. Predicted and measured trends in combustor exit temperature, CO and NOx are in general agreement at the different water/fuel loading rates, although quantitative differences exist between the predictions and measurements.

  19. Molecular density functional theory for water with liquid-gas coexistence and correct pressure

    SciTech Connect

    Jeanmairet, Guillaume Levesque, Maximilien; Sergiievskyi, Volodymyr; Borgis, Daniel

    2015-04-21

    The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. The solvation free energy of small molecular solutes like n-alkanes and hard sphere solutes whose radii range from angstroms to nanometers is now in quantitative agreement with reference all atom simulations. The macroscopic liquid-gas surface tension predicted by the theory is comparable to experiments. This theory gives an alternative to the empirical hard sphere bridge correction used so far by several authors.

  20. Molecular density functional theory for water with liquid-gas coexistence and correct pressure

    NASA Astrophysics Data System (ADS)

    Jeanmairet, Guillaume; Levesque, Maximilien; Sergiievskyi, Volodymyr; Borgis, Daniel

    2015-04-01

    The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. The solvation free energy of small molecular solutes like n-alkanes and hard sphere solutes whose radii range from angstroms to nanometers is now in quantitative agreement with reference all atom simulations. The macroscopic liquid-gas surface tension predicted by the theory is comparable to experiments. This theory gives an alternative to the empirical hard sphere bridge correction used so far by several authors.

  1. On the Electronic Nature of the Surface Potential at the Vapor-Liquid Interface of Water

    SciTech Connect

    Kathmann, S M; Kuo, I; Mundy, C J

    2008-02-05

    The surface potential at the vapor-liquid interface of water is relevant to many areas of chemical physics. Measurement of the surface potential has been experimentally attempted many times, yet there has been little agreement as to its magnitude and sign (-1.1 to +0.5 mV). We present the first computation of the surface potential of water using ab initio molecular dynamics. We find that the surface potential {chi} = -18 mV with a maximum interfacial electric field = 8.9 x 10{sup 7} V/m. A comparison is made between our quantum mechanical results and those from previous molecular simulations. We find that explicit treatment of the electronic density makes a dramatic contribution to the electric properties of the vapor-liquid interface of water. The E-field can alter interfacial reactivity and transport while the surface potential can be used to determine the 'chemical' contribution to the real and electrochemical potentials for ionic transport through the vapor-liquid interface.

  2. Liquid Water on Enceladus from Observations of Ammonia and Ar-40 in the Plume

    NASA Technical Reports Server (NTRS)

    Waite, J. H., Jr.; Lewis, W. S.; Magee, B. A.; Lunine, J. I.; McKinnon, W. B.; Glein, C. R.; Mousis, O.; Young, D. T.; Brockwell, T.; Westlake, J.; Nguyen, M.-J.; Teolis, B. D.; Niemann, H. B.; McNutt, R. L., Jr.; Perry, M.; Ip, W.-H.

    2009-01-01

    Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell-as suggested most recently by the discovery of salts in E-ring particles derived from the plume-or warm ice that is heated, causing dissociation of clathrate hydrates. Here we report that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, Ar-40. The presence of ammonia provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate. We conclude, from the overall composition of the material, that the plume derives from both a liquid reservoir (or from ice that in recent geological time has been in contact with such a reservoir) as well as from degassing, volatile-charged ice. As part of a general comprehensive review of the midsize saturnian satellites at the conclusion of the prime Cassini mission, PI McKinnon and co-I Barr contributed to three review chapters.

  3. Acoustic strength of water and effect of ultrasound on the liquid-vapor phase diagram

    NASA Astrophysics Data System (ADS)

    Volkov, G. A.; Petrov, Yu. V.; Gruzdkov, A. A.

    2015-05-01

    The structure-time approach is used to develop an analytical model that makes it possible to predict the dependences of the acoustic cavitation threshold of water on temperature and background pressure. The calculated dependences are compared with the results of experiments carried out in the leading laboratories. It is demonstrated that the proposed approach allows the estimation of the effect of the acoustic field on the phase state of the substance under study. The calculated liquid-vapor phase curves for water in the presence of acoustic fields are presented.

  4. Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory

    SciTech Connect

    Nordlund, Dennis; Odelius, Michael; Bluhm, Hendrik; Ogasawara, Hirohito; Pettersson, Lars G.M.; Nilsson, Anders

    2008-04-29

    We present valence photoelectron emission spectra of liquid water in comparison with gas-phase water, ice close to the melting point, low temperature amorphous and crystalline ice. All aggregation states have major electronic structure changes relative to the free molecule, with rehybridization and development of bonding and anti-bonding states accompanying the hydrogen bond formation. Sensitivity to the local structural order, most prominent in the shape and splitting of the occupied 3a{sub 1} orbital, is understood from the electronic structure averaging over various geometrical structures, and reflects the local nature of the orbital interaction.

  5. Water clusters: Untangling the mysteries of the liquid, one molecule at a time

    PubMed Central

    Keutsch, Frank N.; Saykally, Richard J.

    2001-01-01

    Extensive terahertz laser vibration-rotation-tunneling spectra and mid-IR laser spectra have been compiled for several isotopomers of small (dimer through hexamer) water clusters. These data, in conjunction with new theoretical advances, quantify the structures, force fields, dipole moments, and hydrogen bond rearrangement dynamics in these clusters. This new information permits us to systematically untangle the intricacies associated with cooperative hydrogen bonding and promises to lead to a more complete molecular description of the liquid and solid phases of water, including an accurate universal force field. PMID:11535820

  6. Ultrafast dynamics of liquid water: Frequency fluctuations of the OH stretch and the HOH bend

    SciTech Connect

    Imoto, Sho; Xantheas, Sotiris S.; Saito, Shinji

    2013-07-28

    Frequency fluctuations of the OH stretch and the HOH bend in liquid water are reported from the third-order response function evaluated using the TTM3-F potential for water. The simulated two-dimensional infrared (IR) spectra of the OH stretch are similar to previously reported theoretical results. The present study suggests that the frequency fluctuation of the HOH bend is faster than that of the OH stretch. The ultrafast loss of the frequency correlation of the HOH bend is due to the strong couplings with the OH stretch as well as the intermolecular hydrogen bond bend.

  7. Determination of 226Ra and 224Ra in drinking waters by liquid scintillation counting.

    PubMed

    Manjón, G; Vioque, I; Moreno, H; García-Tenorio, R; García-León, M

    1997-04-01

    A method for the determination of Ra-isotopes in water samples has been developed. Ra is coprecipitated with Ba as sulphate. The precipitate is then dissolved with EDTA and counted with a liquid scintillation system after mixing with a scintillation cocktail. The study of the temporal evolution of the separated activity gives the isotopic composition of the sample, i.e. the 224Ra and 226Ra contribution to the total activity. The method has been applied to some Spanish drinking waters. PMID:9106993

  8. Satellite observation of winter season subsurface liquid melt water retention on the Greenland ice sheet using spectroradiometer and scatterometer data

    NASA Astrophysics Data System (ADS)

    Miller, J. Z.; Forster, R. R.; Long, D. G.; Brewer, S.

    2013-12-01

    The recently discovered perennial firn aquifer (PFA) represents a new glacier facie and a previously undefined liquid water storage mechanism on the Greenland ice sheet (GrIS). The current hypothesis suggests that at least two geophysical processes control the formation of the PFA: 1) high melt rates that saturate snow and firn layers with liquid water during the melt season, and 2) high snow accumulation rates that subsequently insulate this saturated layer allowing it to be retained in liquid form during the winter season. The PFA is potentially an important component in ice sheet mass and energy budget calculations, however, large-scale observations linking surface melt, subsurface liquid melt water retention, and the PFA currently do not exist. Satellite-borne spectroradiometers and scatterometers are frequently used to detect the presence of liquid water content over the GrIS. The sensor's penetration depth is dependent on the frequency (which determines wavelength) and time-varying geophysical properties (which determine absorption and scattering characteristics). At shorter spectral wavelengths, penetration depths are limited at the interface between the ice sheet surface and the atmosphere. Spectroradiometer-derived retrievals of liquid water content represent an integrated response on the order of a few millimeters. At longer microwave wavelengths (C- and Ku-band), penetration depths are increased. Scatterometer-derived retrievals of liquid water content represent an integrated response on the order of a few centimeters to several meters. We combine spectroradiometer data acquired from the Moderate Resolution Imaging Spectroradiometer aboard Terra and Aqua (MODIS) and C- and Ku-band scatterometer data acquired from MetOP-A (ASCAT) and OceanSAT-2 (OSCAT) to investigate the spatiotemporal variability of subsurface liquid water content on the GrIS. Penetration depth differences are exploited to distinguish between the detection of liquid water content controlled by surface heat flux and the detection of subsurface liquid water content controlled by the retention process. Surface freeze-up is identified using MODIS-derived ice surface temperatures. We then identify distinct microwave signatures suggesting the presence of subsurface liquid water content, characterize the stratigraphy and geophysical processes controlling the observed response, and derive a retrieval algorithm using a simple radiative transfer model. Over the 4 year time series (2009-2013), results indicate subsurface liquid melt water persists within Ku-band penetration depth up to ~1 month and within C-band penetration depth between ~1-5 months following surface-freeze-up. Detection occurs exclusively in regions where the PFA has previously been mapped using field (Arctic Circle Traverse) and airborne (IceBridge) observations and the spatial extent is consistent with regional climate model (RACMO2) simulations.

  9. Zero Liquid Discharge (ZLD) System for Flue-Gas Derived Water From Oxy-Combustion Process

    SciTech Connect

    Sivaram Harendra; Danylo Oryshchyn; Thomas Ochs; Stephen J. Gerdemann; John Clark

    2011-10-16

    Researchers at the National Energy Technology Laboratory (NETL) located in Albany, Oregon, have patented a process - Integrated Pollutant Removal (IPR) that uses off-the-shelf technology to produce a sequestration ready CO{sub 2} stream from an oxy-combustion power plant. Capturing CO{sub 2} from fossil-fuel combustion generates a significant water product which can be tapped for use in the power plant and its peripherals. Water condensed in the IPR{reg_sign} process may contain fly ash particles, sodium (from pH control), and sulfur species, as well as heavy metals, cations and anions. NETL is developing a treatment approach for zero liquid discharge while maximizing available heat from IPR. Current treatment-process steps being studied are flocculation/coagulation, for removal of cations and fine particles, and reverse osmosis, for anion removal as well as for scavenging the remaining cations. After reverse osmosis process steps, thermal evaporation and crystallization steps will be carried out in order to build the whole zero liquid discharge (ZLD) system for flue-gas condensed wastewater. Gypsum is the major product from crystallization process. Fast, in-line treatment of water for re-use in IPR seems to be one practical step for minimizing water treatment requirements for CO{sub 2} capture. The results obtained from above experiments are being used to build water treatment models.

  10. Thermoreversible partitioning of poly(ethylene oxide)s between water and a hydrophobic ionic liquid.

    PubMed

    Bai, Zhifeng; Nagy, Michael W; Zhao, Bin; Lodge, Timothy P

    2014-07-15

    We describe a poly(ethylene oxide) (PEO) homopolymer "shuttle" between water and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). PEO homopolymers with varying molecular weight transferred reversibly and quantitatively between water at room temperature and [EMIM][TFSI] at an elevated temperature. The temperature of the transfer from water to [EMIM][TFSI] shows a linear dependence on PEO molecular weight and a dependence on polymer concentration consistent with expectation based on Flory-Huggins theory. These results are also consistent with the previously observed lower critical solution temperature (LCST) behavior of PEO in water. Dynamic light scattering study of the concentration and temperature dependence of the swelling degree of PEO corona of polybutadiene (PB)-PEO block copolymer micelles indicates that the solvent quality of [EMIM][TFSI] for PEO remains essentially the same as a good solvent over the temperature range of the PEO shuttle. Fundamental understanding of the PEO shuttle is of significance in development of systems for phase transfer of reagents and reaction products between ionic liquids and water. PMID:24988141

  11. Requirements of first-principles calculations of X-ray absorption spectra of liquid water.

    PubMed

    Fransson, Thomas; Zhovtobriukh, Iurii; Coriani, Sonia; Wikfeldt, Kjartan T; Norman, Patrick; Pettersson, Lars G M

    2016-01-01

    A computational benchmark study on X-ray absorption spectra of water has been performed by means of transition-potential density functional theory (TP-DFT), damped time-dependent density functional theory (TDDFT), and damped coupled cluster (CC) linear response theory. For liquid water, using TDDFT with a tailored CAM-B3LYP functional and a polarizable embedding, we find that an embedding with over 2000 water molecules is required to fully converge spectral features for individual molecules, but a substantially smaller embedding can be used within averaging schemes. TP-DFT and TDDFT calculations on 100 MD structures demonstrate that TDDFT produces a spectrum with spectral features in good agreement with experiment, while it is more difficult to fully resolve the spectral features in the TP-DFT spectrum. Similar trends were also observed for calculations of bulk ice. In order to further establish the performance of these methods, small water clusters have been considered also at the CC2 and CCSD levels of theory. Issues regarding the basis set requirements for spectrum simulations of liquid water and the determination of gas-phase ionization potentials are also discussed. PMID:26619162

  12. Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

    SciTech Connect

    Lu, Qing; Kim, Jaegil; Straub, John E.; Farrell, James D.; Wales, David J.

    2014-11-14

    The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

  13. High-accuracy measurement of low-water-content in liquid using NIR spectral absorption method

    NASA Astrophysics Data System (ADS)

    Peng, Bao-Jin; Wan, Xu; Jin, Hong-Zhen; Zhao, Yong; Mao, He-Fa

    2005-01-01

    Water content measurement technologies are very important for quality inspection of food, medicine products, chemical products and many other industry fields. In recent years, requests for accurate low-water-content measurement in liquid are more and more exigent, and great interests have been shown from the research and experimental work. With the development and advancement of modern production and control technologies, more accurate water content technology is needed. In this paper, a novel experimental setup based on near-infrared (NIR) spectral technology and fiber-optic sensor (OFS) is presented. It has a good measurement accuracy about -/+ 0.01%, which is better, to our knowledge, than most other methods published until now. It has a high measurement resolution of 0.001% in the measurement range from zero to 0.05% for water-in-alcohol measurement, and the water-in-oil measurement is carried out as well. In addition, the advantages of this method also include pollution-free to the measured liquid, fast measurement and so on.

  14. Evaporation Rates for Liquid Water and Ice Under Current Martian Conditions

    NASA Technical Reports Server (NTRS)

    Sears, D. W. G.; Moore, S. R.; Meier, A.; Chittenden, J.; Kareev, M.; Farmer, C. B.

    2004-01-01

    A number of studies have been concerned with the evaporation rates under martian conditions in order to place limits on the possible survival time of both liquid water and ice exposed on the surface of Mars. Such studies also aid in assessing the efficacy of an overlying layer of dust or loose regolith material in providing a barrier to free evaporation and thus prolong the lifetime of water in locations where its availability to putative living organisms would be significant. A better quantitative understanding of the effects of phase changes of water in the near surface environment would also aid the evaluation of the possible role of water in the formation of currently observed features, such as gullies in cliff walls and relatively short-term changes in the albedo of small surface areas ('dark stains'). Laboratory measurements aimed at refinement of our knowledge of these values are described here. The establishment of accurate values for evaporation rates and their dependence on the physical conditions of temperature, pressure and energy input, is an important benchmark for the further investigation of the efficacy of barriers to free evaporation in providing a prolonged period of survival of the water, particularly as a liquid.

  15. Crystalline, liquid crystalline, and isotropic phases of sodium deoxycholate in water

    SciTech Connect

    Su, Ziyang; Luthra, Suman; Krzyzaniak, Joseph F.; Agra-Kooijman, Dena M.; Kumar, Satyendra; Byrn, Stephen R.; Shalaev, Evgenyi Y.

    2012-09-06

    Sodium deoxycholate (NaDC) is an important example of bile salts, representing systems with complex phase behavior involving both crystalline and mesophase structures. In this study, properties of NaDC-water mixtures were evaluated as a function of composition and temperature via X-ray diffraction with synchrotron (sXRD) and laboratory radiation sources, water sorption, polarized light, hot-stage microscopy, and freezing-point osmometry. Several phases were detected depending on the composition and temperature, including isotropic solution phase, liquid crystalline (LC) phase, crystalline hydrate, and ice. The LC phase was identified as hexagonal structure by sXRD, with up to 14 high-order reflections detected. The crystalline phase was found to be nonstoichiometric hydrate, based on XRD and water sorption data. The phase diagram of NaDC-water system has been refined based on both results of this study and other reports in literature.

  16. Solid/liquid phase diagram of the ammonium sulfate/succinic acid/water system.

    PubMed

    Pearson, Christian S; Beyer, Keith D

    2015-05-14

    We have studied the low-temperature phase diagram and water activities of the ammonium sulfate/succinic acid/water system using differential scanning calorimetry and infrared spectroscopy of thin films. Using the results from our experiments, we have mapped the solid/liquid ternary phase diagram, determined the water activities based on the freezing point depression, and determined the ice/succinic acid phase boundary as well as the ternary eutectic composition and temperature. We also compared our results to the predictions of the extended AIM aerosol thermodynamics model (E-AIM) and found good agreement for the ice melting points in the ice primary phase field of this system; however, differences were found with respect to succinic acid solubility temperatures. We also compared the results of this study with those of previous studies that we have published on ammonium sulfate/dicarboxylic acid/water systems. PMID:25431860

  17. Improved prediction of octanol-water partition coefficients from liquid-solute water solubilities and molar volumes

    USGS Publications Warehouse

    Chiou, C.T.; Schmedding, D.W.; Manes, M.

    2005-01-01

    A volume-fraction-based solvent-water partition model for dilute solutes, in which the partition coefficient shows a dependence on solute molar volume (V??), is adapted to predict the octanol-water partition coefficient (K ow) from the liquid or supercooled-liquid solute water solubility (Sw), or vice versa. The established correlation is tested for a wide range of industrial compounds and pesticides (e.g., halogenated aliphatic hydrocarbons, alkylbenzenes, halogenated benzenes, ethers, esters, PAHs, PCBs, organochlorines, organophosphates, carbamates, and amidesureas-triazines), which comprise a total of 215 test compounds spanning about 10 orders of magnitude in Sw and 8.5 orders of magnitude in Kow. Except for phenols and alcohols, which require special considerations of the Kow data, the correlation predicts the Kow within 0.1 log units for most compounds, much independent of the compound type or the magnitude in K ow. With reliable Sw and V data for compounds of interest, the correlation provides an effective means for either predicting the unavailable log Kow values or verifying the reliability of the reported log Kow data. ?? 2005 American Chemical Society.

  18. Ionic Liquid Films at the Water-Air Interface: Langmuir Isotherms of Tetra-alkylphosphonium-Based Ionic Liquids.

    PubMed

    Shimizu, Karina; Canongia Lopes, José N; Gonçalves da Silva, Amélia M P S

    2015-08-01

    The behavior of ionic liquids trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide and trihexyl(tetradecyl)phosphonium dicyanamide, [P6?6?6?14][Ntf2] and [P6 6 6 14][N(CN)2], respectively, at the water-air interface was investigated using the Langmuir trough technique. The obtained surface pressure versus mean molecular area (MMA) isotherms, ?-A, and surface potential versus MMA isotherms, ?V-A, show distinct interfacial behavior between the two systems. The results were interpreted at a molecular level using molecular dynamics simulations: the different compression regimes along the [P6 6 6 14][Ntf2] isotherm correspond to the self-organization of the ions at the water surface into compact and planar monolayers that coalesce at an MMA value of ca. 1.85 nm(2)/ion pair to form an expanded liquidlike layer. Upon further compression, the monolayer collapses at around 1.2 nm(2)/ion pair to yield a progressively thicker and less organized layer. These transitions are much more subdued in the [P6 6 6 14][N(CN)2] system because of the more hydrophilic nature of the dicyanamide anion. The numerical density profiles obtained from the MD simulation trajectories are also able to emphasize the very unusual packing of the four long alkyl side chains of the cation above and below the ionic layer that forms at the water surface. Such a distribution is also different for the two studied systems during the different compression regimes. PMID:26161843

  19. The Liquid-Water Oscillation in Modeling Boundary-Layer Cumuli with Third-Order Turbulence Closure Models

    NASA Technical Reports Server (NTRS)

    Cheng, A.; Xu, K.-M.; Golaz, J.-C.

    2004-01-01

    A hierarchy of third-order turbulence closure models are used to simulate boundary-layer cumuli in this study. An unrealistically strong liquid-water oscillation (LWO) is found in the fully prognostic model, which predicts all third moments. The LWO propagates from cloud base to cloud top with a speed of 1 m/s. The period of the oscillation is about 1000 s. Liquid-water buoyancy terms in the third-moment equations contribute to the LWO. The LWO mainly affects the vertical profiles of cloud fraction, mean liquid-water mixing ratio and the fluxes of liquid-water potential temperature and total water, but has less impact on the vertical profiles of other second-moments and third-moments. In order to minimize the LWO, a moderate large diffusion coefficient and a large turbulent dissipation at its originating level are needed. However, this approach distorts the vertical distributions of cloud fraction and liquid-water mixing ratio. A better approach is to parameterize liquid-water buoyancy more reasonably. A minimally prognostic model, which diagnoses all third moments except for vertical velocity, is shown to produce better results, compared to a fully prognostic model.

  20. Mechanisms of hydrogen bond formation between ionic liquids and cellulose and the influence of water content.

    PubMed

    Rabideau, Brooks D; Ismail, Ahmed E

    2015-02-28

    We study the dynamics of the formation of multiple hydrogen bonds between ionic liquid anions and cellulose using molecular dynamics simulations. We examine fifteen different ionic liquids composed of 1-alkyl-3-methylimidazolium cations ([Cnmim], n = 1, 2, 3, 4, 5) paired with either chloride, acetate or dimethylphosphate. We map the transitions of anions hydrogen bonded to cellulose into different bonding states. We find that increased tail length in the ionic liquids has only a very minor effect on these transitions, tending to slow the dynamics of the transitions and increasing the hydrogen bond lifetimes. Each anion can form up to four hydrogen bonds with cellulose. We find that this hydrogen bond "redundancy" leads to multiply bonded anions having lifetimes three to four times that of singly bound anions. Such redundant hydrogen bonds account for roughly half of all anion-cellulose hydrogen bonds. Additional simulations for [C2mim]Cl, [C2mim]Ac and [C2mim]DMP were performed at different water concentrations between 70 mol% and 90 mol%. It was found that water crowds the hydrogen bond-accepting sites of the anions, preventing interactions with cellulose. The more water that is present in the system, the more crowded these sites become. Thus, if a hydrogen bond between an anion and cellulose breaks, the likelihood that it will be replaced by a nearby water molecule increases as well. We show that the formation of these "redundant" hydrogen bonding states is greatly affected by the presence of water, leading to steep drops in hydrogen bonding between the anions and cellulose. PMID:25627658

  1. Estimating Entropy of Liquids from Atom-Atom Radial Distribution Functions: Silica, Beryllium Fluoride and Water

    E-print Network

    Ruchi Sharma; Manish Agarwal; Charusita Chakravarty

    2008-09-24

    Molecular dynamics simulations of water, liquid beryllium fluoride and silica melt are used to study the accuracy with which the entropy of ionic and molecular liquids can be estimated from atom-atom radial distribution function data. All three systems are known to display similar liquid-state thermodynamic and kinetic anomalies due to a region of anomalous excess entropy behaviour where entropy rises on isothermal compression. The pair correlation entropy is demonstrated to be sufficiently accurate that the density-temperature regime of anomalous behaviour as well as the strength of the entropy anomaly can be predicted reliably for both ionic melts as well as different rigid-body pair potentials for water. Errors in the total thermodynamic entropy for ionic melts due to the pair correlation approximation are of the order of 10% or less for most state points but can be significantly larger in the anomalous regime at very low temperatures. In the case of water, as expected given the rigid-body constraints for a molecular liquids, the pair correlation approximation causes significantly larger errors, between 20 and 30%, for most state points. Comparison of the excess entropy, Se, of ionic melts with the pair correlation entropy, S2, shows that the temperature dependence of Se is well described by T ??2=5 scaling across both the normal and anomalous regimes, unlike in the case of S2. As a function of density, the Se(rho) curves shows only a single maximum while the S2(rho) curves show both a maximum and a minimum. These differences in the behaviour of S2 and Se are due to the fact that the residual multiparticle entropy, delta(S) = Se - S2, shows a strong negative correlation with tetrahedral order in the anomalous regime.

  2. Polymorphism of the glucosyltransferase gene (ycjM) in Escherichia coli and its use for tracking human fecal pollution in water.

    PubMed

    Deng, Daiyong; Zhang, Ning; Xu, Dong; Reed, Mary; Liu, Fengjing; Zheng, Guolu

    2015-12-15

    This study examined polymorphism of the glucosyltransferase gene (ycjM) in fecal Escherichia coli isolates and evaluated the use of the sequence polymorphism for measuring human fecal pollution in water. Significant nucleotide variations were observed through comparative analysis of the ycjM sequences of 70 E. coli strains isolated from the feces of humans, domestic livestock, and wild animals. Three distinct types of ycjM sequences were found: universal-ycjM, human/chicken-ycjM, and human-ycjM. Using the human-ycjM sequences, both a polymerase chain reaction (PCR), Hycj-PCR and a quantitative PCR, Hycj-qPCR, were developed. As shown by the Hycj-PCR amplification, the human-ycjM marker appeared to be highly associated with the E. coli strains isolated from human feces, based on the analysis of 370 E. coli strains isolated from humans and seven other animal species. Similarly, the human-ycjM marker was highly linked with human feces, as demonstrated by the Hycj-PCR assay, when using 337 fecal DNA samples from 16 host animal sources, including both domestic and wild animals. Overall, the specificity and sensitivity of the human-ycjM marker for differentiating between the feces of humans and those of nonhuman groups were 99.7% and 100%, respectively; the prevalence of the marker appeared to be greater than 50% in the human-feces-associated E. coli population. In addition, our study showed that the quantification of human E. coli by the Hycj-qPCR was linearly correlated with the anthropogenic activity within a watershed. Our study suggests that this novel human-ycjM marker and the resulting PCR-based methods developed should be useful for measuring human-associated E. coli and human fecal pollution in water. PMID:26282760

  3. Bond orientational ordering in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization

    E-print Network

    Tanaka, Hajime

    2013-01-01

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases the complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is most poorly understood. We argue that it is crucial for a better understanding of liquid to recognize that a liquid generally has a tendency to have local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally expla...

  4. High-brightness water-window electron-impact liquid-jet microfocus source P. Skoglund,a

    E-print Network

    High-brightness water-window electron-impact liquid-jet microfocus source P. Skoglund,a U resulting in water-window oxygen line emission at 525 eV/2.36 nm with a brightness of 3.0 109 ph/ s m2 sr- tive target of the liquid-jet laser plasma3,5 has proven valu- able and it enabled the first high

  5. Water Reactivity in the Liquid and Supercritical CO2 Phase: Has Half the Story Been Neglected?

    SciTech Connect

    McGrail, B. Peter; Schaef, Herbert T.; Glezakou, Vassiliki Alexandra; Dang, Liem X.; Owen, Antionette T.

    2009-02-01

    Aqueous-phase mediated chemical reactions with dissolved CO2 have long been considered the principal if not only reactive process supporting mineralization reactions with basalt and other reactive reservoir rocks and caprocks in deep geologic sequestration systems. This is not surprising given the quite high solubility of CO2 in the aqueous phase and ample evidence from natural systems of the reactivity of CO2-charged waters with a variety of silicate minerals. In contrast, comparatively scant attention has been directed at reactivity of water solvated in liquid and supercritical CO2, with the exception of interest in the impacts of water in CO2 on the corrosion of pipeline steels. The results presented in this paper show that the most interesting and important aspects of water reactivity with metal and oxide surfaces of interest in geologic sequestration systems actually occurs in the liquid or supercritical CO2 phase. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  6. Experimental evidence for the formation of liquid saline water on Mars

    PubMed Central

    Fischer, Erik; Martínez, Germán M; Elliott, Harvey M; Rennó, Nilton O

    2014-01-01

    Evidence for deliquescence of perchlorate salts has been discovered in the Martian polar region while possible brine flows have been observed in the equatorial region. This appears to contradict the idea that bulk deliquescence is too slow to occur during the short periods of the Martian diurnal cycle during which conditions are favorable for it. We conduct laboratory experiments to study the formation of liquid brines at Mars environmental conditions. We find that when water vapor is the only source of water, bulk deliquescence of perchlorates is not rapid enough to occur during the short periods of the day during which the temperature is above the salts' eutectic value, and the humidity is above the salts' deliquescence value. However, when the salts are in contact with water ice, liquid brine forms in minutes, indicating that aqueous solutions could form temporarily where salts and ice coexist on the Martian surface and in the shallow subsurface. Key Points The formation of brines at Martian conditions was studied experimentally Bulk deliquescence from water vapor is too slow to occur diurnally on Mars Brines form in minutes when salts are placed in direct contact with ice PMID:25821267

  7. Seasonal and diurnal cycles of liquid water in snow—Measurements and modeling

    NASA Astrophysics Data System (ADS)

    Heilig, A.; Mitterer, C.; Schmid, L.; Wever, N.; Schweizer, J.; Marshall, H.-P.; Eisen, O.

    2015-10-01

    Evaluating and improving snow models and outflow predictions for hydrological applications is hindered by the lack of continuous data on bulk volumetric liquid water content (?w) and storage capacity of the melting snowpack. The combination of upward looking ground-penetrating radar and conventional snow height sensors enable continuous, nondestructive determinations of ?w in natural snow covers from first surficial wetting until shortly before melt out. We analyze diurnal and seasonal cycles of ?w for 4 years in a flat study site and for three melt seasons on slopes and evaluate model simulations for two different water transport schemes in the snow cover model SNOWPACK. Observed maximum increases in ?w during a day are below 1.7 vol % (90th percentile) at the flat site. Concerning seasonal characteristics of ?w, less than 10% of recorded data exceed 5 vol % at the flat site and 3.5 vol % at slopes. Both water transport schemes in SNOWPACK underestimate maximum ?w at the flat site systematically for all observed melt seasons, while simulated ?w maxima on slopes are accurate. Implementing observed changes in ?w per day in outflow predictions increases model performance toward higher agreement with lysimeter measurements. Hence, continuously monitoring ?w improves our understanding of liquid water percolation and retention in snow, which is highly relevant for several aspects of the cryosphere such as avalanche formation, catchment hydrology, and ice sheet mass balances.

  8. Molecular dynamics studies on the water mixtures of pharmaceutically important ionic liquid lidocaine HCl.

    PubMed

    Wojnarowska, Z; Grzybowska, K; Hawelek, L; Swiety-Pospiech, A; Masiewicz, E; Paluch, M; Sawicki, W; Chmielewska, A; Bujak, P; Markowski, J

    2012-05-01

    In this paper the molecular dynamics of a common local-anesthetic drug, lidocaine hydrochloride (LD-HCl), and its water mixtures were investigated. By means of broadband dielectric spectroscopy and calorimetric measurements it was shown that even a small addition of water causes a significant effect on the relaxation dynamics of analyzed protic ionic liquid. Apart from the two well-resolved relaxations (?- and ?-processes) and the ?-mode, identified as the JG-process, observed for anhydrous LD-HCl, a new relaxation peak (?) is visible in the dielectric spectra of aqueous mixtures of this drug. Additionally, the significant effect of the water on the glass transition temperature of LD-HCl was found. The sample characterized with mole fraction of water X(w) = 0.44 reveals the glass transition temperature T(g), 42 K lower than that of anhydrous material (307 K). Finally, it was shown that by amorphization of the hydrochloride salt of lidocaine it is possible to obtain its room temperature ionic liquid form. PMID:22424553

  9. Polymer Electrolyte Fuel Cells Membrane Hydration by Direct Liquid Water Contact

    SciTech Connect

    Wilson, M.S.; Zawodzinski, C.; Gottesfeld, S.

    1998-11-01

    An effective means of providing direct liquid hydration of the membrane tends to improve performance particularly of cells with thicker membranes or at elevated temperatures. Supplying the water to the membrane from the anode flow-field through the anode backing via wicks would appear to have advantages over delivering the water through the thickness of the membrane with regards to the uniformity and stability of the supply and the use of off-the-shelf membranes or MEAs. In addition to improving cell performance, an important contribution of direct liquid hydration approaches may be that the overall fuel cell system becomes simpler and more effective. The next steps in the evolution of this approach are a demonstration of the effectiveness of this technique with larger active area cells as well as the implementation of an internal flow-field water reservoir (to eliminate the injection method). Scale-up to larger cell sizes and the use of separate water channels within the anode flow-field is described.

  10. Volatile liquid hydrocarbons in waters of the Gulf of Mexico and Caribbean Sea

    SciTech Connect

    Sauer, T.C. Jr.

    1980-03-01

    Concentrations of volatile liquid hydrocarbons (VLH), C/sub 6/-C/sub 14/ hydrocarbons, were determined in 1977 in coastal, shelf, and open-ocean surface waters of the Gulf of Mexico and Caribbean Sea. In open-ocean, nonpetroleum-polluted surface water, VLH concentrations were 60 ng.liter/sup -1/ while in heavily polluted Louisiana shelf and coastal water values reached 500 ng.liter/sup -1/. Caribbean surface samples had very low concentrations, 30 ng.liter/sup -1/. The relationship between anthropogenic gaseous hydrocarbons and VLH was approximately linear. Aromatic VLH accounted for 60 to 85% of the total VLH in surface waters. Cycloalkane concentrations were < 1.0 ng.liter/sup -1/ in open ocean water, 60 to 100 ng.liter/sup -1/ in polluted water (20% of total VLH). Alkanes were 15 ng.liter/sup -1/ in open ocean water, 40 ng.liter/sup -1/ in polluted water. The concentrations of five major VLH compounds (aromatics) in water samples - benzene, toluene, ethylbenzene, m/sup -/, p-xylenes, and o-xylene (called BTX) - were sufficient to predict the total VLH. The empirically determined relationship is VLH (ng.liter/sup -1/) = 1.42 BTX (ng.liter/sup -1/); r = 0.96. Subsurface VLH concentrations in samples of polluted waters collected from depths of 50 m were only 35 to 40 ng.liter/sup -1/ below surface concentrations. Open ocean subsurface samples had concentrations of only 30 ng.liter/sup -1/ at 30 to 50-m depths, comparable to those of Caribbean surface water.

  11. Rapid determination of anilines in water samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop prior to gas chromatography-mass spectrometry.

    PubMed

    Diao, Chun-Peng; Wei, Chao-Hai

    2012-05-01

    A rapid, sensitive and environmentally friendly method for the analysis of 14 anilines in water samples by dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) prior to gas chromatography-mass spectrometry (GC-MS) was developed and optimized. In the proposed method, cyclohexane was used as the extraction solvent as its toxicity was much lower than that of the solvent usually used in dispersive liquid-liquid microextraction (DLLME). In the optimized conditions, the method exhibited good analytical performance. Based on a signal-to-noise ratio of 3, limits of detection for anilines were in the range of 0.07 to 0.29 ?g L(-1), and the linear range was 0.5-200 ?g L(-1) with regression coefficients (r(2)) higher than 0.9977. It was efficient for qualitative and quantitative analysis of anilines in water samples. The relative standard deviations varied from 2.9 to 8.6% depending on different compounds indicating good precision. Tap water and river water were selected for evaluating the application to real water samples. The relative recoveries of anilines for the two real samples spiked with 10 ?g L(-1) anilines were in the scope of 78.2-114.6% and 77.3-115.6%, respectively. PMID:22434272

  12. Molecular origin of the difference in the HOH bend of the IR spectra between liquid water and ice

    SciTech Connect

    Imoto, Sho; Xantheas, Sotiris S.; Saito, Shinji

    2013-02-07

    The intensity of the HOH bend in the IR spectrum of ice is significantly smaller than the corresponding one in liquid water. This difference in the IR intensities of the HOH bend in the two systems is investigated using MD simulations with the flexible, polarizable, ab-initio based TTM3-F model for water, a potential that correctly reproduces the experimentally observed increase of the HOH bend in liquid water and ice from the water monomer value. We have identified two factors that are responsible for the difference in the intensity of the HOH bend in liquid water and ice: (i) the decrease of the intensity of the HOH bend in ice caused by the strong anti-correlation between the permanent dipole moment of a molecule and the induced dipole moment of a neighboring hydrogen bond acceptor molecule and (ii) the weakening of this anti-correlation by the disordered hydrogen bond network in liquid water. The presence of the anti-correlation in ice is further confirmed by ab initio electronic structure calculations of water pentamer clusters extracted from the trajectories of the MD simulations for ice and liquid water.

  13. Method and apparatus for electrokinetic co-generation of hydrogen and electric power from liquid water microjets

    DOEpatents

    Saykally, Richard J; Duffin, Andrew M; Wilson, Kevin R; Rude, Bruce S

    2013-02-12

    A method and apparatus for producing both a gas and electrical power from a flowing liquid, the method comprising: a) providing a source liquid containing ions that when neutralized form a gas; b) providing a velocity to the source liquid relative to a solid material to form a charged liquid microjet, which subsequently breaks up into a droplet spay, the solid material forming a liquid-solid interface; and c) supplying electrons to the charged liquid by contacting a spray stream of the charged liquid with an electron source. In one embodiment, where the liquid is water, hydrogen gas is formed and a streaming current is generated. The apparatus comprises a source of pressurized liquid, a microjet nozzle, a conduit for delivering said liquid to said microjet nozzle, and a conductive metal target sufficiently spaced from said nozzle such that the jet stream produced by said microjet is discontinuous at said target. In one arrangement, with the metal nozzle and target electrically connected to ground, both hydrogen gas and a streaming current are generated at the target as it is impinged by the streaming, liquid spray microjet.

  14. Liquid water in small solar system bodies, and the possibilities for evolution of life

    NASA Astrophysics Data System (ADS)

    Sparks, D. W.; Tice, M. M.; Farrell, L.; McGary, R. S.

    2008-12-01

    Much attention has been focused on the few large satellites of Jupiter and Saturn that have evidence of interior layers of liquid water, and the possibility that they may be suitable habitats for life. For life to evolve in these regions, they would have to, at a minimum, produce the necessary chemical constituents to provide energy for building organic matter, be protected from temperature extremes and radiation, and last long enough for evolution to progress. The type of organisms that could form in such habitats could be similar to those that evolved in the pre-photosynthetic, anoxic early Earth. The probability of extra-terrestrial life evolving in our solar system would increase greatly if such suitable habitats had been more common. We examine the possibilities for suitable habitats in the more numerous set of moderate-sized (< 1000 km in diameter) ice-rich planetesimals that may populate the Asteroid Belt and Kuiper Belt. We modeled the thermal evolution of 200-1000 km planetesimals, assuming cold accretion of undifferentiated bodies comprised of a mixture of chondritic rock and water ice. The heat sources for these planetesimals are short- and long-lived radioactive isotopes, and the latent heat from hydration reactions. We vary the planetesimals initial size, surface temperature, ice/rock ratio and the 26Al content (which is very sensitive to the timing of accretion). Each modeled planetesimal undergoes a pulse of radioactive heating, followed by slow cooling. Some water from the melting ice phase migrates upward to form an "internal ocean" layer beneath a still frozen crust, while some water reacts with the remaining rock to form a hydrated silicate (serpentinized) core. In warmer planetesimals, these hydrated silicates can break-down, and a second phase of water production and migration occurs. If the frozen rock/ice crust becomes too thin, we assume that crustal overturn will result in loss of any underlying liquid. Many models produce liquid water layers lasting hundreds of millions of years. These water layers overlay a large core of serpentinzing silicate, which would be producing hydrogen, methane, sulfate and possibly complex organics to the water layer. We will explore the possible biogeochemical cycling that could develop in these systems.

  15. Evaluation of the rate of uptake of nitrogen dioxide by atmospheric and surface liquid water

    SciTech Connect

    Lee, Y.; Schwartz, S.E.

    1981-12-20

    The rate of uptake of NO/sub 2/ by liquid water according to (R1), 2NO/sub 2/(g)+H/sub 2/O(l)..-->..2H+NO/sub 3//sup -/+NO/sub 2//sup -/, is shown to be unaffected by O/sub 2/(0.2 atm). Hence the rate constant and Henry's law solubility constant of NO/sub 2/ previously obtained may be employed to evaluate the rates of aqueous phase reactions of NO/sub 2/ in the ambient atmosphere. Reactions (R1) and (R2), NO/sub 2/(g)+NO(g)+H/sub 2/O(l)..-->..2H/sup +/+2NO/sub 2//sup -/, are quite slow at representative atmospheric partial pressures and cloud liquid water content; the characteristic times range upward from 10/sup 3/--10/sup 4/ hours at 10/sup -7/ atm, increasing with decreasing partial pressures of the gases. Direct acidification of cloud liquid water by (R1) or (R2) is also unimportant. Catalytic enhancement of (R1) is potentially important for catalyst concentrations of order 10/sup -7/ M, assuming sufficiently fast rate constants (approx.10/sup 8/ M/sup -1/s/sup -1/). Iron-catalyzed reaction in particular, however, is found to be unimportant. Reaction of NO/sub 2/ with dissolved S(IV) is potentially important, based upon an assumed upper limit rate constant of 2.5 x 10/sup 7/ M/sup -1/ s/sup -1/. Deposition of NO/sub 2/ to surface (ocean or lake) water is shown to be controlled by aqueous phase mass transport and/or reaction and is much slower than heretofore assumed.

  16. Mutual solubilities between water and non-aromatic sulfonium-, ammonium- and phosphonium-hydrophobic ionic liquids.

    PubMed

    Kurnia, Kiki A; Quental, Maria V; Santos, Luís M N B F; Freire, Mara G; Coutinho, João A P

    2015-02-14

    Although previous studies attempted to characterize the liquid-liquid phase behaviour between water and ionic liquids (ILs), the impact of non-cyclic cations on the solubilities is poorly studied and yet to be understood. In this work, the mutual solubilities between water and ILs containing the anion bis(trifluoromethylsulfonyl)imide, [NTf2](-), combined with the cations diethylmethylsulfonium, [S221][NTf2], triethylsulfonium, [S222][NTf2], butyltrimethylammonium, [N4111][NTf2], tributylmethylammonium, [N4441][NTf2], methyltrioctylammonium, [N1888][NTf2], and methyltrioctylphosphonium, [P1888][NTf2], from (288.15 to 318.15) K and at 0.1 MPa, were experimentally measured and further compared with predictions from the COnductor-like Screening MOdel for Real Solvents (COSMO-RS). All the studied phase diagrams display an upper critical solution temperature (UCST). The binary system composed of [P1888][NTf2] exhibits the widest immiscibility gap, followed by [N18888][NTf2], [N4441][NTf2], [S222][NTf2], [N4111][NTf2], and [S221][NTf2]. The COSMO-RS is able to correctly predict the experimental UCST behaviour and the cation impact on the immiscibility regimes observed. Natural Population Analysis (NPA) calculations were additionally performed for the isolated cations in the gas phase indicating that the differences in the water-IL mutual miscibilities might not result only from the hydrophobicity of the cation (derived from the increase of the alkyl chains length) but also from the charge distribution of the central atom and attached methylene groups. This fact explains the enhanced solubility of ammonium-based ILs in water here identified. PMID:25583632

  17. Mutual solubilities between water and non-aromatic sulfonium-, ammonium- and phosphonium-hydrophobic ionic liquids

    PubMed Central

    Kurnia, Kiki A.; Quental, Maria V.; Santos, Luís M. N. B. F.; Freire, Mara G.; Coutinho, João A. P.

    2015-01-01

    Although previous studies attempted to characterize the liquid–liquid phase behaviour between water and ionic liquids (ILs), the impact of non-cyclic cations on the solubilities is poorly studied and yet to be understood. In this work, the mutual solubilities between water and ILs containing the anion bis(trifluoromethylsulfonyl)imide, [NTf2]?, combined with the cations diethylmethylsulfonium, [S221][NTf2], triethylsulfonium, [S222][NTf2], butyltrimethylammonium, [N4111][NTf2], tributylmethylammonium, [N4441][NTf2], methyltrioctylammonium, [N1888][NTf2], and methyltrioctylphosphonium, [P1888][NTf2], from (288.15 to 318.15) K and at 0.1 MPa, were experimentally measured and further compared with predictions from the COnductor-like Screening MOdel for Real Solvents (COSMO-RS). All the studied phase diagrams display an upper critical solution temperature (UCST). The binary system composed of [P1888][NTf2] exhibits the widest immiscibility gap, followed by [N18888][NTf2], [N4441][NTf2], [S222][NTf2], [N4111][NTf2], and [S221][NTf2]. The COSMO-RS is able to correctly predict the experimental UCST behaviour and the cation impact on the immiscibility regimes observed. Natural Population Analysis (NPA) calculations were additionally performed for the isolated cations in the gas phase indicating that the differences in the water–IL mutual miscibilities might not result only from the hydrophobicity of the cation (derived from the increase of the alkyl chains length) but also from the charge distribution of the central atom and attached methylene groups. This fact explains the enhanced solubility of ammonium-based ILs in water here identified. PMID:25583632

  18. Temperature and length scale dependence of solvophobic solvation in a single-site water-like liquid

    NASA Astrophysics Data System (ADS)

    Dowdle, John R.; Buldyrev, Sergey V.; Stanley, H. Eugene; Debenedetti, Pablo G.; Rossky, Peter J.

    2013-02-01

    The temperature and length scale dependence of solvation properties of spherical hard solvophobic solutes is investigated in the Jagla liquid, a simple liquid that consists of particles interacting via a spherically symmetric potential combining a hard core repulsion and a longer ranged soft core interaction, yet exhibits water-like anomalies. The results are compared with equivalent calculations for a model of a typical atomic liquid, the Lennard-Jones potential, and with predictions for hydrophobic solvation in water using the cavity equation of state and the extended simple point charge model. We find that the Jagla liquid captures the qualitative thermodynamic behavior of hydrophobic hydration as a function of temperature for both small and large length scale solutes. In particular, for both the Jagla liquid and water, we observe temperature-dependent enthalpy and entropy of solvation for all solute sizes as well as a negative solvation entropy for sufficiently small solutes at low temperature. This feature of water-like solvation is distinct from the strictly positive and temperature independent enthalpy and entropy of cavity solvation observed in the Lennard-Jones fluid. The results suggest that, compared to a simple liquid, it is the presence of a second thermally accessible repulsive energy scale, acting to increasingly favor larger separations for decreasing temperature, that is the essential characteristic of a liquid that favors low-density, open structures, and models hydrophobic hydration, and that it is the presence of this second energy scale that leads to the similarity in the behavior of water and the Jagla liquid. In addition, the Jagla liquid dewets surfaces of large radii of curvature less readily than the Lennard-Jones liquid, reflecting a greater flexibility or elasticity in the Jagla liquid structure than that of a typical liquid, a behavior also similar to that of water's hydrogen bonding network. The implications of the temperature and length scale dependence of solvation free energies in water-like liquids are explored with a simple model for the aggregation of solvophobic solutes. We show how aggregate stability depends upon the size of the aggregate and the size of its constituent solutes, and we relate this dependence to cold-induced destabilization phenomena such as the cold-induced denaturation of proteins.

  19. Solid/Liquid phase diagram of the ammonium sulfate/maleic acid/water system.

    PubMed

    Beyer, Keith D; Schroeder, Jason R; Pearson, Christian S

    2011-12-01

    We have studied the low temperature phase diagram and water activities of the ammonium sulfate/maleic acid/water system using differential scanning calorimetry and infrared spectroscopy of thin films. Using the results from our experiments, we have mapped the solid/liquid ternary phase diagram, determined the water activities based on the freezing point depression, and determined the ice/maleic acid phase boundary as well as the ternary eutectic composition and temperature. We also compare our results to the predictions of the extended AIM aerosol thermodynamics model and find good agreement for the ice melting points in the ice primary phase field of this system; however significant differences were found with respect to phase boundaries, maleic acid dissolution, and ammonium sulfate dissolution. PMID:22017680

  20. Advantages of liquid fluoride thorium reactor in comparison with light water reactor

    NASA Astrophysics Data System (ADS)

    Bahri, Che Nor Aniza Che Zainul; Majid, Amran Ab.; Al-Areqi, Wadeeah M.

    2015-04-01

    Liquid Fluoride Thorium Reactor (LFTR) is an innovative design for the thermal breeder reactor that has important potential benefits over the traditional reactor design. LFTR is fluoride based liquid fuel, that use the thorium dissolved in salt mixture of lithium fluoride and beryllium fluoride. Therefore, LFTR technology is fundamentally different from the solid fuel technology currently in use. Although the traditional nuclear reactor technology has been proven, it has perceptual problems with safety and nuclear waste products. The aim of this paper is to discuss the potential advantages of LFTR in three aspects such as safety, fuel efficiency and nuclear waste as an alternative energy generator in the future. Comparisons between LFTR and Light Water Reactor (LWR), on general principles of fuel cycle, resource availability, radiotoxicity and nuclear weapon proliferation shall be elaborated.

  1. Thermally excited capillary waves at vapor/liquid interfaces of water-alcohol mixtures

    E-print Network

    David Vaknin; Wei Bu; Jaeho Sung; Yoonnam Jeon; Doseok Kim

    2009-04-15

    The density profiles of liquid/vapor interfaces of water-alcohol (methanol, ethanol and propanol) mixtures were studied by surface sensitive synchrotron X-ray scattering techniques. X-ray reflectivity and diffuse scattering measurements, from the pure and mixed liquids, were analyzed in the framework of capillary-wave theory to address the characteristics length-scales of the intrinsic roughness and the shortest capillary-wavelength (alternatively, the upper wave-vector cutoff in capillary wave theory). Our results establish that the intrinsic roughness is dominated by average interatomic distances. The extracted effective upper wave-vector cutoff indicates capillary wave theory breaks-down at distances on order of bulk correlation lengths.

  2. Filling environmental data gaps with QSPR for ionic liquids: Modeling n-octanol/water coefficient.

    PubMed

    Rybinska, Anna; Sosnowska, Anita; Grzonkowska, Monika; Barycki, Maciej; Puzyn, Tomasz

    2016-02-13

    Ionic liquids (ILs) form a wide group of compounds characterized by specific properties that allow using ILs in different fields of science and industry. Regarding that the growing production and use of ionic liquids increase probability of their emission to the environment, it is important to estimate the ability of these compounds to spread in the environment. One of the most important parameters that allow evaluating environmental mobility of compound is n-octanol/water partition coefficient (KOW). Experimental measuring of the KOW values for a large number of compounds could be time consuming and costly. Instead, computational predictions are nowadays being used more often. The paper presents new Quantitative Structure-Property Relationship (QSPR) model that allows predicting the logarithmic values of KOW for 335 ILs, for which the experimentally measured values had been unavailable. We also estimated bioaccumulation potential and point out which group of ILs could have negative impact on environment. PMID:26530890

  3. A novel mechanism for the extraction of metals from water to ionic liquids.

    PubMed

    Janssen, Camiel H C; Sánchez, Antonio; Witkamp, Geert-Jan; Kobrak, Mark N

    2013-11-11

    We present a novel mechanism for the extraction of metals from aqueous phases to room-temperature ionic liquids (ILs) by use of a high-temperature salt as an extraction agent. The mechanism capitalizes on the fact that charged metal complexes are soluble in ILs; this allows for extraction of charged complexes rather than the neutral species, which are formed by conventional approaches. The use of a well-chosen extraction agent also suppresses the competing ion-exchange mechanism, thus preventing degradation of the ionic liquid. The approach permits the use of excess extractant to drive the recovery of metals in high yield. This work presents both a thermodynamic framework for understanding the approach and experimental verification of the process in a range of different ILs. The method has great potential value in the recovery of metals, water purification and nuclear materials processing. PMID:24590618

  4. Advantages of liquid fluoride thorium reactor in comparison with light water reactor

    SciTech Connect

    Bahri, Che Nor Aniza Che Zainul Majid, Amran Ab.; Al-Areqi, Wadeeah M.

    2015-04-29

    Liquid Fluoride Thorium Reactor (LFTR) is an innovative design for the thermal breeder reactor that has important potential benefits over the traditional reactor design. LFTR is fluoride based liquid fuel, that use the thorium dissolved in salt mixture of lithium fluoride and beryllium fluoride. Therefore, LFTR technology is fundamentally different from the solid fuel technology currently in use. Although the traditional nuclear reactor technology has been proven, it has perceptual problems with safety and nuclear waste products. The aim of this paper is to discuss the potential advantages of LFTR in three aspects such as safety, fuel efficiency and nuclear waste as an alternative energy generator in the future. Comparisons between LFTR and Light Water Reactor (LWR), on general principles of fuel cycle, resource availability, radiotoxicity and nuclear weapon proliferation shall be elaborated.

  5. Temperature and Length Scale Dependence of Solvophobic Solvation in a Single-site Water-like Liquid

    E-print Network

    John R. Dowdle; Sergey V. Buldyrev; H. Eugene Stanley; Pablo G. Debenedetti; Peter J. Rossky

    2012-11-01

    The temperature and length scale dependence of solvation properties of spherical hard solvophobic solutes is investigated in the Jagla liquid, a simple liquid that consists of particles interacting via a spherically symmetric potential combining a hard core repulsion and a longer ranged soft core interaction, yet exhibits water-like anomalies. The results are compared with equivalent calculations for a model of a typical atomic liquid, the Lennard-Jones (LJ) potential, and with predictions for hydrophobic solvation in water using the cavity equation of state and the extended simple point charge (SPC/E) model. We find that the Jagla liquid captures the qualitative thermodynamic behavior of hydrophobic hydration as a function of temperature for both small and large length scale solutes. In particular, for both the Jagla liquid and water, we observe temperature-dependent enthalpy and entropy of solvation for all solute sizes as well as a negative solvation entropy for sufficiently small solutes at low temperature. The results suggest that, compared to a simple liquid, it is the presence of a second thermally accessible repulsive energy scale, acting to increasingly favor larger separations for decreasing temperature, that is the essential characteristic of a liquid that favors low-density, open structures and models hydrophobic hydration, and that it is the presence of this second energy scale that leads to the similarity in the behavior of water and the Jagla liquid. The implications of the temperature and length scale dependence of solvation free energies in water-like liquids are explored with a simple model for the aggregation of solvophobic solutes. We show how aggregate stability depends upon the size of the aggregate and the size of its constituent solutes, and we relate this dependence to cold-induced destabilization phenomena such as the cold-induced denaturation of proteins.

  6. Theoretical study of the ionization of liquid water from its several initial orbitals by fast electron impact

    NASA Astrophysics Data System (ADS)

    de Sanctis, M. L.; Politis, M.-F.; Vuilleumier, R.; Stia, C. R.; Fojón, O. A.

    2015-08-01

    We theoretically study the single ionization of liquid water by energetic electrons through one active-electron first-order model. We analyze the angular ejected electron spectra corresponding to the most external orbitals 1B1, 2A1, 1B2 and 1A1 of a single water molecule. We work to create a realistic description of those orbitals corresponding to single molecules in the liquid phase. This goal is achieved by means of a Wannier orbital formalism. Multiple differential cross sections are computed and compared with previous calculations for both liquid and gas phases. In addition, our present results are integrated over all orientations and compared with experimental ones for randomly oriented vapour water molecules, as no experiments currently exist for the liquid phase. Moreover, we estimate the influence of the passive electrons on the reaction by means of a model potential.

  7. Method for reprocessing and recycling of aqueous rinsing liquids from car painting with water-based paints in automobile industry

    NASA Astrophysics Data System (ADS)

    Baumann, Walter; Dinglreiter, Udo

    2011-08-01

    In the paint processes of modern car plants the paint to be applied on the car bodies change after every few numbers. In order to avoid intermixtures of different lacquers the application systems has to be cleaned before every change by means of a rinsing liquid. Water based lacquers require water based cleaning agents. For these rinsing waters a new recycling process based on an evaporation process, a fractionated condensation and an after treatment of the condensates is described. The compatibility of the recycled system for lacquers is investigated. After a test with ten recycling loops no accumulation of harmful substances occurs. In comparison to original agents the recycled rinsing liquids show comparable or better cleaning abilities. The comparison of the energy consumption and the disposal of CO2 and of volatile organic compounds between the application of fresh rinsing liquid with disposal after usage and recycled rinsing liquid show major advantages of the recycling process.

  8. Experimental and theoretical investigation of water removal from DMAZ liquid fuel by an adsorption process

    NASA Astrophysics Data System (ADS)

    Ghanbari, Shahram; Vaferi, Behzad

    2015-07-01

    2-dimethylaminoethylazide (DMAZ) is a new liquid fuel that has made significant progress in bio/mono propellant rocket engines in recent years. Purification of DMAZ fuel by reducing its water content using various adsorbents including zeolites, calcium chloride and nano-particles is experimentally and theoretically investigated. The highest water adsorption of 92.6% from the DMAZ solution is obtained by the CaCl2 adsorbent within 10 min. Four different artificial neural networks (ANN) are examined to correlate an extent of removed water from the DMAZ solution to its affecting parameters. The performed regression analysis indicated that water initial concentration (WIC), adsorbent types, solution temperature, contact time and adsorbent dosage are the most important affecting variables for water sorption from the DMAZ solution. The accomplished statistical analysis demonstrated a multi-layer perceptron neural network (MLPNN) with seven hidden neurons and is the most accurate approach for modeling the considered task. The obtained results showed that the proposed MLPNN model could be successfully employed for accurate prediction of an amount of water removal from the DMAZ fuel solution by the adsorption process.

  9. Liquid chromatographic method for determining the concentration of bisazir in water

    USGS Publications Warehouse

    Scholefield, Ronald J.; Slaght, Karen S.; Allen, John L.

    1997-01-01

    Barrier dams, traps, and lampricides are the techniques currently used by the Great Lakes Fishery Commission to control sea lampreys (Petromyzon marinus) in the Great Lakes. To augment these control techniques, a sterile-male-release research program was initiated at the Lake Huron Biological Station. Male sea lampreys were sterilized by intraperitoneal injection of the chemical sterilant P,P-bis(1-aziridinyl)-N-methylphosphinothioic amide (bisazir). An analytical method was needed to quantitate the concentration of bisazir in water and to routinely verify that bisazir (>25 ?g/L) does not persist in the treated effluent discharged from the sterilization facility to Lake Huron. A rapid, accurate, and sensitive liquid chromatographic (LC) method was developed for determining bisazir in water. Bisazir was dissolved in Lake Huron water; extracted and concentrated on a C18 solid-phase extraction column; eluted with methanol; and quantitated by reversed-phase LC using a C18 column, a mobile phase of 70% water and 30% methanol (v/v), and UV detection (205 nm). Bisazir retention time was 7-8 min; total run time was about 20 min. Method detection limit for bisazir dissolved in Lake Huron water was about 15 ?g/L. Recovery from Lake Huron water fortified with bisazir at 100 ?g/L was 94% (95% confidence interval, 90.2-98.2%).

  10. Characterization of Super-Cooled Liquid Water Clouds Using the Research Scanning Polarimeter Measurements

    NASA Astrophysics Data System (ADS)

    Alexandrov, M. D.; Cairns, B.; van Diedenhoven, B.; Wasilewski, A. P.; Ackerman, A. S.

    2014-12-01

    Super-cooled liquid water (SCW) clouds, where liquid droplets exist at temperatures below 0oC, impact both the radiative budget and the development of precipitation. They also present an aviation hazard due to their role in aircraft icing. The two recent NASA's field campaigns POlarimeter Definition EXperiment (PODEX, based in Palmdale, California, January - February 2013) and Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS, based in Houston, Texas in August - September 2013) provided a unique opportunity to observe SCW clouds from the high-altitude airborne platform of NASA's ER-2 aircraft. We present an analysis of the measurements made by the Research Scanning Polarimeter (RSP) during these experiments. This instrument measures both polarized and total reflectance in 9 spectral channels with central wavelengths of 410, 470, 555, 670, 865, 960, 1590, 1880 and 2250 nm. The RSP is a scanning sensor taking samples at 0.8o intervals within 60o from nadir in both forward and backward directions. This unique high angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135o and 165o for every pixel independently. Simple parametric fitting algorithms applied to the polarized reflectance provide retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows us to retrieve the droplet size distribution itself. The latter is important in the case of SCW clouds, which often have complex spatial and microphysical structure. For example the measurements made on 22 September 2013 during SEAC4RS indicate a cloud that alternates between being in glaciated and liquid phases, with super-cooled liquid drops at altitudes as high as 10 km, which correspond to temperatures close to the homogeneous freezing temperature of pure water drops (about -38oC). The multi-modal droplet size distributions retrieved from RSP data in this case are consistent with the multi-layer cloud structure observed by correlative Cloud Profiling Lidar measurements.

  11. The first vadose zone partitioning interwell tracer test for nonaqueous phase liquid and water residual

    SciTech Connect

    Mariner, P.E.; Jin, M.; Studer, J.E.; Pope, G.A.

    1999-08-15

    In 1995, a partitioning interwell tracer test was conducted in the vadose zone beneath two buried organic liquid disposal trenches at Sandia National Laboratories in New Mexico. The purpose was to estimate the amount and distribution of trichloroethylene (TCE) trapped by capillary forces as residual dense nonaqueous phase liquid (DNAPL). Screened injection and extraction wells, placed 16.8 m apart, and two monitor wells with multilevel sampling capability allowed vertical testing from 3.0 to 24.4 m below ground surface. Seven tracers were injected, but the most useful tracers in the final analysis were sulfur hexafluoride (nonpartitioning), perfluoro-1,3,5-trimethylcyclohexane (TCE-partitioning), and difluoromethane (water-partitioning). Both a TCE-partitioning tracer and a water-partitioning tracer were needed to determine average TCE DNAPL saturation. Average saturations of DNAPL and water were measured to be 0.11 {+-} 0.02% and 23 {+-} 2.0%, respectively, in the shallow zone between 3.0 and 10.7 m. Monitor well data showed no evidence of DNAPL below a depth of 9 m. These results had important implications for remedial actions at the site.

  12. New Technique for Retrieving Liquid Water Path over Land using Satellite Microwave Observations

    SciTech Connect

    Deeter, M.N.; Vivekanandan, J.

    2005-03-18

    We present a new methodology for retrieving liquid water path over land using satellite microwave observations. As input, the technique exploits the Advanced Microwave Scanning Radiometer for earth observing plan (EOS) (AMSR-E) polarization-difference signals at 37 and 89 GHz. Regression analysis performed on model simulations indicates that over variable atmospheric and surface conditions the polarization-difference signals can be simply parameterized in terms of the surface emissivity polarization difference ({Delta}{var_epsilon}), surface temperature, liquid water path (LWP), and precipitable water vapor (PWV). The resulting polarization-difference parameterization (PDP) enables fast and direct (noniterative) retrievals of LWP with minimal requirements for ancillary data. Single- and dual-channel retrieval methods are described and demonstrated. Data gridding is used to reduce the effects of instrumental noise. The methodology is demonstrated using AMSR-E observations over the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site during a six day period in November and December, 2003. Single- and dual-channel retrieval results mostly agree with ground-based microwave retrievals of LWP to within approximately 0.04 mm.

  13. Measuring Snow Liquid Water Content with Low-Cost GPS Receivers

    PubMed Central

    Koch, Franziska; Prasch, Monika; Schmid, Lino; Schweizer, Jürg; Mauser, Wolfram

    2014-01-01

    The amount of liquid water in snow characterizes the wetness of a snowpack. Its temporal evolution plays an important role for wet-snow avalanche prediction, as well as the onset of meltwater release and water availability estimations within a river basin. However, it is still a challenge and a not yet satisfyingly solved issue to measure the liquid water content (LWC) in snow with conventional in situ and remote sensing techniques. We propose a new approach based on the attenuation of microwave radiation in the L-band emitted by the satellites of the Global Positioning System (GPS). For this purpose, we performed a continuous low-cost GPS measurement experiment at the Weissfluhjoch test site in Switzerland, during the snow melt period in 2013. As a measure of signal strength, we analyzed the carrier-to-noise power density ratio (C/N0) and developed a procedure to normalize these data. The bulk volumetric LWC was determined based on assumptions for attenuation, reflection and refraction of radiation in wet snow. The onset of melt, as well as daily melt-freeze cycles were clearly detected. The temporal evolution of the LWC was closely related to the meteorological and snow-hydrological data. Due to its non-destructive setup, its cost-efficiency and global availability, this approach has the potential to be implemented in distributed sensor networks for avalanche prediction or basin-wide melt onset measurements. PMID:25384007

  14. Liquid water on Mars - An energy balance climate model for CO2/H2O atmospheres

    NASA Technical Reports Server (NTRS)

    Hoffert, M. I.; Callegari, A. J.; Hsieh, C. T.; Ziegler, W.

    1981-01-01

    A simple climatic model is developed for a Mars atmosphere containing CO2 and sufficient liquid water to account for the observed hydrologic surface features by the existence of a CO2/H2O greenhouse effect. A latitude-resolved climate model originally devised for terrestrial climate studies is applied to Martian conditions, with the difference between absorbed solar flux and emitted long-wave flux to space per unit area attributed to the divergence of the meridional heat flux and the poleward heat flux assumed to equal the atmospheric eddy heat flux. The global mean energy balance is calculated as a function of atmospheric pressure to assess the CO2/H2O greenhouse liquid water hypothesis, and some latitude-resolved cases are examined in detail in order to clarify the role of atmospheric transport and temperature-albedo feedback. It is shown that the combined CO2/H2O greenhouse at plausible early surface pressures may account for climates hot enough to support a hydrological cycle and running water at present-day insolation and visible albedo levels.

  15. Determination of characteristic features of cloud liquid water from satellite microwave measurements

    SciTech Connect

    Guosheng Liu; Curry, J.A. )

    1993-03-20

    In this paper the authors present an algorithm for determining liquid water path (LWP) in clouds using satellite microwave measurements from the special sensor microwave/imager (SSM/I). This physically based algorithm is derived using the guidance of a 32-stream plane-parallel model of microwave radiative transfer in the cloudy atmosphere. Their investigation using both radiative transfer model and observed SSM/I data indicates that the retrieved LWP is sensitive to the emission temperature of the liquid water, to the presence of large hydrometeors, to the nonuniformity of the rainfall in the satellite field of view, and to the radiation from atmosphere and ocean. Therefore they have incorporated cloud temperature into their algorithm using ancillary infrared satellite data. To account for the effects of rainfall on the LWP retrievals, they use a threshold for the onset of precipitation to determine whether there is any precipitation in the satellite field of view. Two separate retrieval schemes are derived for non-precipitating and precipitating clouds. A clear-sky radiation scheme is developed to separate radiation of atmosphere and ocean from that of liquid water. This algorithm is indirectly validated by comparing retrieved values of LWP for clear versus cloudy situations. The retrievals are examined for regions in the tropical western Pacific Ocean, the North Atlantic Ocean, and the subtropical southeast Pacific Ocean. The retrievals obtained using their algorithm are also compared with simultaneous retrievals using other LWP algorithms described in the literature. The present algorithm is shown to perform consistently well in all three regions under all conditions. It is determined that features of their algorithm that result in more consistent global retrievals of LWP are inclusion of the tunable clear-sky scheme, estimation of cloud temperature using satellite infrared radiances, and consideration of precipitation. 31 refs., 20 figs., 3 tabs.

  16. Permeability of Rubbery and Glassy Membranes of Ionic Liquid Filled Polymersome Nanoreactors in Water.

    PubMed

    So, Soonyong; Yao, Letitia J; Lodge, Timothy P

    2015-12-01

    Nanoemulsion-like polymer vesicles (polymersomes) having ionic liquid interiors dispersed in water are attractive for nanoreactor applications. In a previous study, we demonstrated that small molecules could pass through rubbery polybutadiene membranes on a time scale of seconds, which is practical for chemical transformations. It is of interest to determine how sensitive the rate of transport is to temperature, particularly for membranes in the vicinity of the glass transition (Tg). In this work, the molecular exchange rate of 1-butylimidazole through glassy polystyrene (PS) bilayer membranes is investigated via pulsed field gradient nuclear magnetic resonance (PFG-NMR) over the temperature range from 25 to 70 °C. The vesicles were prepared by the cosolvent method in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([EMIM][TFSI]), and four different polystyrene-b-poly(ethylene oxide) (PS-PEO) diblock polymers with varying PS molecular weights were examined. The vesicles were transferred from the ionic liquid to water at room temperature to form nanoemulsion solutions of polymer vesicles in water. The exchange rate of 1-butylimidazole added to the aqueous solutions was observed under equilibrium conditions at each temperature. The exchange rate decreased as the membrane thickness increased, and the exchange rate through the glassy membranes was three to four times slower than through the rubbery polybutadiene membranes under the same experimental conditions. These results demonstrate that the permeability through nanosized membranes depends on both the dimension and chemistry of membrane-forming blocks. Furthermore, the exchange rate was investigated as a function of temperature in the vicinity of the Tg of PS-PEO membranes. The exchange rate, however, is not a strong function of the temperature in the vicinity of the membrane Tg, due to a combination of the nanoscopic dimension of the membrane, and some degree of solvent plasticization. PMID:26588106

  17. Electrochemical assessment of water|ionic liquid biphasic systems towards cesium extraction from nuclear waste.

    PubMed

    Stockmann, T Jane; Zhang, Jing; Montgomery, Anne-Marie; Ding, Zhifeng

    2014-04-22

    A room temperature ionic liquid (IL) composed of a quaternary alkylphosphonium (trihexyltetradecylphosphonium, P66614(+)) and tetrakis(pentafluorophenyl)borate anion (TB(-)) was employed within a water|P66614TB (w|P66614TB or w|IL) biphasic system to evaluate cesium ion extraction in comparison to that with a traditional water|organic solvent (w|o) combination. (137)Cs is a major contributor to the radioactivity of spent nuclear fuel as it leaves the reactor, and its extraction efficiency is therefore of considerable importance. The extraction was facilitated by the ligand octyl(phenyl)-N,N'-diisobutylcarbamoylphosphine oxide (CMPO) used in TRans-Uranium EXtraction processes and investigated through well established liquid|liquid electrochemistry. This study gave access to the metal ion to ligand (1:n) stoichiometry and overall complexation constant, ?, of the interfacial complexation reaction which were determined to be 1:3 and 1.6×10(11) at the w|P66614TB interface while the study at w|o elicited an n equal to 1 with ? equal to 86.5. Through a straightforward relationship, these complexation constant values were converted to distribution coefficients, ?(?), with the ligand concentrations studied for comparison to other studies present in the literature; the w|o and w|IL systems gave ?(?) of 2 and 8.2×10(7), respectively, indicating a higher overall extraction efficiency for the latter. For the w|o system, the metal ion-ligand stoichiometries were confirmed through isotopic distribution analysis of mass spectra obtained by the direct injection of an emulsified water-organic solvent mixture into an electron spray ionization mass spectrometer. PMID:24703212

  18. Topological hydrogen-bond definition to characterize the structure and dynamics of liquid water.

    PubMed

    Henchman, Richard H; Irudayam, Sheeba Jem

    2010-12-23

    A definition that equates a hydrogen bond topologically with a local energy well in the potential energy surface is used to study the structure and dynamics of liquid water. We demonstrate the robustness of this hydrogen-bond definition versus the many other definitions which use fixed, arbitrary parameters, do not account for variable molecular environments, and cannot effectively resolve transition states. Our topology definition unambiguously shows that most water molecules are double acceptors but sizable proportions are single or triple acceptors. Almost all hydrogens are found to take part in hydrogen bonds. Broken hydrogen bonds only form when two molecules try to form two hydrogen bonds between them. The double acceptors have tetrahedral geometry, lower potential energy, entropy, and density, and slower dynamics. The single and triple acceptors have trigonal and trigonal bipyramidal geometry and when considered together have higher density, potential energy, and entropy, faster dynamics, and a tendency to cluster. These calculations use an extended theory for the entropy of liquid water that takes into account the variable number of hydrogen bonds. Hydrogen-bond switching is shown to depend explicitly on the variable number of hydrogen bonds accepted and the presence of interstitial water molecules. Transition state theory indicates that the switching of hydrogen bonds is a mildly activated process, requiring only a moderate distortion of hydrogen bonds. Three main types of switching events are observed depending on whether the donor and acceptor are already sharing a hydrogen bond. The switch may proceed with no intermediate or via a bifurcated-oxygen or cyclic dimer, both of which have a broken hydrogen bond and symmetric and asymmetric forms. Switching is found to be strongly coupled to whole-molecule vibration, particularly for the more mobile single and triple acceptors. Our analysis suggests that even though water is heterogeneous in terms of the number of hydrogen bonds, the coupling between neighbors on various length and time scales brings about greater continuity in its properties. PMID:21114302

  19. ESTIMATION OF WATER SOLUBILITY AND OCTANOL/WATER PARTITION COEFFICIENT OF HYDROPHOBIC DYES - PART II. REVERSE-PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

    EPA Science Inventory

    Capacity factors were determined for 20 disperse and solvent dyes by a high performance liquid chromatographic method using methanol/water and a C-18 reverse-phase column. egression equations are given that establish relationships among capacity factors, water solubilities and oc...

  20. Onset of ice VII phase of liquid water: role of filamentation in stimulated Raman scattering.

    PubMed

    Rakesh Kumar, V; Prem Kiran, P

    2015-06-15

    Energy dependent evolution of Stokes and anti-Stokes lines of ice VII via forward stimulated Raman scattering (FSRS) during propagation of a 30 ps laser pulse through liquid water, confirming structural change over GPa pressure range, is studied. Self-focusing of the intense laser pulses is observed to ionize the medium generating free electrons that dominate the evolution of SRS signals. The confinement of plasma-generated free electrons by filamentation is observed to enhance the signature Raman modes of ice VII by reducing the SRS threshold. PMID:26076266

  1. Evaluation of liquid water measuring instruments in cold clouds sampled during FIRE. [First ISCCP Research Experiment

    NASA Technical Reports Server (NTRS)

    Heymsfield, Andrew J.; Miloshevich, Larry M.

    1989-01-01

    Airborne liquid water content (LWC) measurements were conducted with an icing detector and a forward-scattering spectrometer probe during 10 flights into cold clouds, as part of the First ISCCP Research Experiment (FIRE). The LWC measurements thus obtained compare favorably with those from the hot-wire probes in the range where LWC is above the detection limits of the latter; the hot-wire probes have detection thresholds about one order of magnitude higher than is possible with the icing detector and spectrometer probe. FIRE experiment data indicate that LWC should be taken into consideration in cloud studies at temperatures down to at least 35 C.

  2. Lyotropic chromonic liquid crystal semiconductors for water-solution processable organic electronics

    NASA Astrophysics Data System (ADS)

    Nazarenko, V. G.; Boiko, O. P.; Anisimov, M. I.; Kadashchuk, A. K.; Nastishin, Yu. A.; Golovin, A. B.; Lavrentovich, O. D.

    2010-12-01

    We propose lyotropic chromonic liquid crystals (LCLCs) as a distinct class of materials for organic electronics. In water, the chromonic molecules stack on top of each other into elongated aggregates that form orientationally ordered phases. The aligned aggregated structure is preserved when the material is deposited onto a substrate and dried. The dried LCLC films show a strongly anisotropic electric conductivity of semiconductor type. The field-effect carrier mobility measured along the molecular aggregates in unoptimized films of LCLC V20 is 0.03 cm2 V-1 s-1. Easy processibility, low cost, and high mobility demonstrate the potential of LCLCs for microelectronic applications.

  3. Ab-inito liquid water with hybrid functionals and dispersion interactions

    NASA Astrophysics Data System (ADS)

    Li, Zhaofeng; Wu, Xifan; Distasio, Robert, Jr.; Car, Roberto

    2012-02-01

    We report ab-initio molecular dynamics simulations of liquid water using the hybrid PBE0 functional plus self-consistent dispersion forces based on the scheme of Ref.ootnotetextA. Tkatchenko and M. Scheffler, Phys. Rev. Lett. 102, 073005 (2009). Simulations were performed at T=300K and at T=330K to approximately account for nuclear quantum effect on the oxygen-oxygen(O-O) RDF, as suggested by previous path integral simulations. Focusing on O-O RDF, we find that the combined effect of the hybrid functional and of the dispersion interactions significantly improves the agreement of the simulated structure with experiment.

  4. The determination of low levels of cobalt-60 in environmental waters by liquid scintillation counting

    USGS Publications Warehouse

    Claassen, H.C.

    1970-01-01

    A method for determination of cobalt-60 in waters at levels greater than 0.5 pCi per sample is presented. A modification of the method may be used to analyze fluvial sediments and soils. After the cobalt has been separated, first as the hydroxide and then as the thiocyanate complex in methyl isobutyl ketone, it is counted in a liquid scintillation system at 80% efficiency. Separation factors achieved for six isotopes are generally greater than 2,000. The time for a single analysis, exclusive of the counting and evaporation operations, is about 2 h. ?? 1970.

  5. Sub-Microsecond Temperature Measurement in Liquid Water Using Laser Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Alderfer, David W.; Herring, G. C.; Danehy, Paul M.; Mizukaki, Toshiharu; Takayama, Kazuyoshi

    2005-01-01

    Using laser-induced thermal acoustics, we demonstrate non-intrusive and remote sound speed and temperature measurements over the range 10 - 45 C in liquid water. Averaged accuracy of sound speed and temperature measurements (10 s) are 0.64 m/s and 0.45 C respectively. Single-shot precisions based on one standard deviation of 100 or greater samples range from 1 m/s to 16.5 m/s and 0.3 C to 9.5 C for sound speed and temperature measurements respectively. The time resolution of each single-shot measurement was 300 nsec.

  6. Vibrational and librational frequency coupling in stimulated scattering spectra of liquid water

    NASA Astrophysics Data System (ADS)

    Dorkenoo, K. D.; Rivoire, G.

    2002-02-01

    Evolution of the backward stimulated Raman spectrum in liquid water when the focusing point of the exciting beam is moved progressively in the bulk from the entrance surface to the bottom shows modulation structures. Proof has been made by using Fourier transform on the spectra that a low frequency structure is present when the focal point is near the entrance window. This structure coexists with a periodical high frequency structure when the focal point is moved inside the bulk. Propagative effects explain the high frequency modulation, while the low frequency modulation (quasi-period 20 cm-1) is explained by coupling of librational and vibrational molecular movements.

  7. Nanoparticle enhanced evaporation of liquids: A case study of silicone oil and water

    E-print Network

    Wenbin Zhang; Rong Shen; Kunquan Lu; Ailing Ji; Zexian Cao

    2012-10-23

    Evaporation is a fundamental physical phenomenon, of which many challenging questions remain unanswered. Enhanced evaporation of liquids in some occasions is of enormous practical significance. Here we report the enhanced evaporation of the nearly permanently stable silicone oil by dispersing with nanopariticles including CaTiO3, anatase and rutile TiO2. The results can inspire the research of atomistic mechanism for nanoparticle enhanced evaporation and exploration of evaporation control techniques for treatment of oil pollution and restoration of dirty water.

  8. Stimulated Raman scattering from ice-VIII by shock-induced compression in liquid water

    NASA Astrophysics Data System (ADS)

    Men, Zhiwei; Li, Zuowei; Zhou, Mi; Lu, Guohui; Zou, Bo; Li, Zhanlong; Sun, Chenglin

    2012-03-01

    Stimulated Raman scattering (SRS) from ice-VIII was investigated using shock-induced compression (SIC) generated by laser-induced breakdown in liquid water. Three backward SRS peaks of OH stretching vibrations and one backward SRS characteristic peak of lattice translation were observed. The SRS spectra indicated that the ice-VIII structure is formed by SIC, as the trajectory of the SIC passes through the stable pressure-temperature range of ice-VIII. The static electric field generated by electron jets protects proton-ordered structure. The laser-induced shock wave mechanism is also discussed.

  9. Lyotropic chromonic liquid crystal semiconductors for water-solution processable organic electronics

    E-print Network

    V. G. Nazarenko; O. P. Boiko; M. I. Anisimov; A. K. Kadashchuk; Yu. A. Nastishin; A. B. Golovin; O. D. Lavrentovich

    2011-01-04

    We propose lyotropic chromonic liquid crystals (LCLCs) as a distinct class of materials for organic electronics. In water, the chromonic molecules stack on top of each other into elongated aggregates that form orientationally ordered phases. The aligned aggregated structure is preserved when the material is deposited onto a substrate and dried. The dried LCLC films show a strongly anisotropic electric conductivity of semiconductor type. The field-effect carrier mobility measured along the molecular aggregates in unoptimized films of LCLC V20 is 0.03 cm^2 V^(-1) s^(-1). Easy processibility, low cost, and high mobility demonstrate the potential of LCLCs for microelectronic applications.

  10. Dielectric Properties of Ice and Liquid Water from First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Lu, Deyu; Gygi, François; Galli, Giulia

    2008-04-01

    We present a first-principles study of the static dielectric properties of ice and liquid water. The eigenmodes of the dielectric matrix ? are analyzed in terms of maximally localized dielectric functions similar, in their definition, to maximally localized Wannier orbitals obtained from Bloch eigenstates of the electronic Hamiltonian. We show that the lowest eigenmodes of ?-1 are localized in real space and can be separated into groups related to the screening of lone pairs, intra-, and intermolecular bonds, respectively. The local properties of the dielectric matrix can be conveniently exploited to build approximate dielectric matrices for efficient, yet accurate calculations of quasiparticle energies.

  11. Observations of cloud liquid water path over oceans: Optical and microwave remote sensing methods

    NASA Technical Reports Server (NTRS)

    Lin, Bing; Rossow, William B.

    1994-01-01

    Published estimates of cloud liquid water path (LWP) from satellite-measured microwave radiation show little agreement, even about the relative magnitudes of LWP in the tropics and midlatitudes. To understand these differences and to obtain more reliable estimate, optical and microwave LWP retrieval methods are compared using the International Satellite Cloud Climatology Project (ISCCP) and special sensor microwave/imager (SSM/I) data. Errors in microwave LWP retrieval associated with uncertainties in surface, atmosphere, and cloud properties are assessed. Sea surface temperature may not produce great LWP errors, if accurate contemporaneous measurements are used in the retrieval. An uncertainty of estimated near-surface wind speed as high as 2 m/s produces uncertainty in LWP of about 5 mg/sq cm. Cloud liquid water temperature has only a small effect on LWP retrievals (rms errors less than 2 mg/sq cm), if errors in the temperature are less than 5 C; however, such errors can produce spurious variations of LWP with latitude and season. Errors in atmospheric column water vapor (CWV) are strongly coupled with errors in LWP (for some retrieval methods) causing errors as large as 30 mg/sq cm. Because microwave radiation is much less sensitive to clouds with small LWP (less than 7 mg/sq cm) than visible wavelength radiation, the microwave results are very sensitive to the process used to separate clear and cloudy conditions. Different cloud detection sensitivities in different microwave retrieval methods bias estimated LWP values. Comparing ISCCP and SSM/I LWPs, we find that the two estimated values are consistent in global, zonal, and regional means for warm, nonprecipitating clouds, which have average LWP values of about 5 mg/sq cm and occur much more frequently than precipitating clouds. Ice water path (IWP) can be roughly estimated from the differences between ISCCP total water path and SSM/I LWP for cold, nonprecipitating clouds. IWP in the winter hemisphere is about 3 times the LWP but only half the LWP in the summer hemisphere. Precipitating clouds contribute significantly to monthly, zonal mean LWP values determined from microwave, especially in the intertropical convergence zone (ITCZ), because they have almost 10 times the liquid water (cloud plus precipitation) of nonprecipitating clouds on average. There are significant differences among microwave LWP estimates associated with the treatment of precipitating clouds.

  12. Evidence for Recent Liquid Water on Mars: Basic Features of Martian Gullies

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Water is the chief agent of weathering and erosion on Earth. Mars is a much drier, colder planet on which liquid water cannot exist very long at the surface because it will immediately begin to boil, evaporate, and freeze--all at the same time. However, new pictures from the Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) have provided an astonishing observation which suggests that liquid water may have played a role in shaping some recent gully-like features found on the slopes of various craters, troughs, and other depressions on the red planet.

    These pictures introduce the basic features of a martian gully. The figure on the left is an example from Mars, the figure on the right is a gully on Earth. In the Earth picture, rain water flowing under and seeping along the base of a recently-deposited volcanic ash layer has created the gully. For Mars, water is not actually seen but is inferred from the landforms and their similarity to examples on Earth.

    The landforms both on Earth and Mars are divided into three parts: the alcove, the channel, and the apron. Water seeps from between layers of rock on the wall of a cliff, crater, or other type of depression. The alcove forms above the site of seepage as water comes out of the ground and undermines the material from which it is seeping. The erosion of material at the site of seepage causes rock and debris on the slope above this area to collapse and slide downhill, creating the alcove.

    The channel forms from water and debris running down the slope from the seepage area. The point where the top of the channel meets the bottom of the alcove is, in many cases, the site where seepage is occurring. Channels are probably flushed-clean of debris from time to time by large flash floods of water released from behind an ice barrier that might form at the site of seepage during more quiescent times.

    The aprons are the down-slope deposits of ice and debris that were moved down the slope and through the channel. Whether any water--likely in the form of ice--persists in these deposits is unknown. The fact that the aprons do not go very far out onto the floors of craters and troughs (e.g., the foreground of the figure on the left) indicates that there is a limit as to how much water actually makes it to the bottom of the slope in liquid form. Most of the water by the time it reaches the bottom of the slope has probably either evaporated or frozen.

    The MOC image on the left was acquired July 3, 1999, and is located on the south-facing wall of an impact crater near 54.8oS, 342.5oW. The MOC image is illuminated from the upper left; north is toward the upper right. The MOC image covers an area 1.3 km (0.8 mi) wide by 2 km (1.2 mi) long. The pictures from the flank of the Mount St. Helens volcano in Washington (right; large image and inset) were taken by MGSMOC Principal Investigator, Michael C. Malin, in the 1980s after the eruptions of May 1980. They are illuminated from the left; note footprints on left side of the picture for scale, also note the colored bar, which is 30 cm (11.8 in) long.

  13. Determination of chloroacetanilide herbicide metabolites in water using high-performance liquid chromatography-diode array detection and high-performance liquid chromatography/mass spectrometry

    USGS Publications Warehouse

    Hostetler, K.A.; Thurman, E.M.

    2000-01-01

    Analytical methods using high-performance liquid chromatography-diode array detection (HPLC-DAD) and high-performance liquid chromatography/mass spectrometry (HPLC/MS) were developed for the analysis of the following chloroacetanilide herbicide metabolites in water: alachlor ethanesulfonic acid (ESA); alachlor oxanilic acid; acetochlor ESA; acetochlor oxanilic acid; metolachlor ESA; and metolachlor oxanilic acid. Good precision and accuracy were demonstrated for both the HPLC-DAD and HPLC/MS methods in reagent water, surface water, and ground water. The average HPLC-DAD recoveries of the chloroacetanilide herbicide metabolites from water samples spiked at 0.25, 0.5 and 2.0 ??g/l ranged from 84 to 112%, with relative standard deviations of 18% or less. The average HPLC/MS recoveries of the metabolites from water samples spiked at 0.05, 0.2 and 2.0 ??g/l ranged from 81 to 118%, with relative standard deviations of 20% or less. The limit of quantitation (LOQ) for all metabolites using the HPLC-DAD method was 0.20 ??g/l, whereas the LOQ using the HPLC/MS method was at 0.05 ??g/l. These metabolite-determination methods are valuable for acquiring information about water quality and the fate and transport of the parent chloroacetanilide herbicides in water. Copyright (C) 2000 Elsevier Science B.V.

  14. Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

    NASA Technical Reports Server (NTRS)

    DelGenio, Anthony

    1999-01-01

    Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning, is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types. At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.5C lower limit for the equilibrium global climate sensitivity to a doubling of CO2 which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

  15. Climatic Implications of the Observed Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains

    NASA Technical Reports Server (NTRS)

    DelGenio, Anthony D.; Wolf, Audrey B.

    1999-01-01

    Satellite observations of low-level clouds have challenged the assumption that adiabatic liquid water content combined with constant physical thickness will lead to a negative cloud optics feedback in a decadal climate change. We explore the reasons for the satellite results using four years of surface remote sensing data from the Atmospheric Radiation Measurement Program Cloud and Radiation Testbed site in the Southern Great Plains of the United States. We find that low cloud liquid water path is approximately invariant with temperature in winter but decreases strongly with temperature in summer, consistent with the satellite inferences at this latitude. This behavior occurs because liquid water content shows no detectable temperature dependence while cloud physical thickness decreases with warming. Thinning of clouds with warming is observed on seasonal, synoptic, and diurnal time scales; it is most obvious in the warm sectors of baroclinic waves. Although cloud top is observed to slightly descend with warming, the primary cause of thinning is the ascent of cloud base due to the reduction in surface relative humidity and the concomitant increase in the lifting condensation level of surface air. Low cloud liquid water path is not observed to be a continuous function of temperature. Rather, the behavior we observe is best explained as a transition in the frequency of occurrence of different boundary layer types: At cold temperatures, a mixture of stratified and convective boundary layers is observed, leading to a broad distribution of liquid water path values, while at warm temperatures, only convective boundary layers with small liquid water paths, some of them decoupled, are observed. Our results, combined with the earlier satellite inferences, imply that the commonly quoted 1.50 C lower limit for the equilibrium global climate sensitivity to a doubling of CO2, which is based on models with near-adiabatic liquid water behavior and constant physical thickness, should be revised upward.

  16. Urinary arsenic metabolism in a Western Chinese population exposed to high-dose inorganic arsenic in drinking water: Influence of ethnicity and genetic polymorphisms

    SciTech Connect

    Fu, Songbo; Wu, Jie; Li, Yuanyuan; Liu, Yan; Gao, Yanhui; Yao, Feifei; Qiu, Chuanying; Song, Li; Wu, Yu; Liao, Yongjian; Sun, Dianjun

    2014-01-01

    To investigate the differences in urinary arsenic metabolism patterns of individuals exposed to a high concentration of inorganic arsenic (iAs) in drinking water, an epidemiological investigation was conducted with 155 individuals living in a village where the arsenic concentration in the drinking water was 969 ?g/L. Blood and urine samples were collected from 66 individuals including 51 cases with skin lesions and 15 controls without skin lesions. The results showed that monomethylated arsenic (MMA), the percentage of MMA (%MMA) and the ratio of MMA to iAs (MMA/iAs) were significantly increased in patients with skin lesions as compared to controls, while dimethylated arsenic (DMA), the percentage of DMA (%DMA) and the ratio of DMA to MMA (DMA/MMA) were significantly reduced. The percent DMA of individuals with the Ala/Asp genotype of glutathione S-transferase omega 1 (GSTO1) was significantly lower than those with Ala/Ala. The percent MMA of individuals with the A2B/A2B genotype of arsenic (+ 3 oxidation state) methyltransferase (AS3MT) was significantly lower than those with AB/A2B. The iAs and total arsenic (tAs) content in the urine of a Tibetan population were significantly higher than that of Han and Hui ethnicities, whereas MMA/iAs was significantly lower than that of Han and Hui ethnicities. Our results showed that when exposed to the same arsenic environment, different individuals exhibited different urinary arsenic metabolism patterns. Gender and ethnicity affect these differences and above polymorphisms may be effectors too. - Highlights: • We first survey a village with high iAs content in the drinking water (969 ?g/L). • 90 villagers suffered typical skin lesions with a morbidity rate of 58%. • Cases exhibited higher %MMA and MMA/iAs, and lower %DMA and DMA/MMA than controls. • Gender and ethnicity affect the differences of iAs methylation metabolism levels. • GSTO1 and AS3MT gene polymorphisms may be factors too.

  17. ETHANOL, ACETIC ACID, AND WATER ADSORPTION FROM BINARY AND TERNARY LIQUID MIXTURES ON HIGH-SILICA ZEOLITES

    EPA Science Inventory

    Adsorption isotherms were measured for ethanol, acetic acid, and water adsorbed on high-silica ZSM-5 zeolite powder from binary and ternary liquid mixtures at room temperature. Ethanol and water adsorption on two high-silica ZSM-5 zeolites with different aluminum contents and a h...

  18. A cobalt(II) bis(salicylate)-based ionic liquid that shows thermoresponsive and selective water coordination

    SciTech Connect

    Kohno, Y; Cowan, MG; Masuda, M; Bhowmick, I; Shores, MP; Gin, DL; Noble, RD

    2014-01-01

    A metal-containing ionic liquid (MCIL) has been prepared in which the [CoII(salicylate)(2)](2-) anion is able to selectively coordinate two water molecules with a visible colour change, even in the presence of alcohols. Upon moderate heating or placement in vacuo, the hydrated MCIL undergoes reversible thermochromism by releasing the bound water molecules.

  19. 30 CFR 250.217 - What solid and liquid wastes and discharges information and cooling water intake information must...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... information and cooling water intake information must accompany the EP? 250.217 Section 250.217 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR... What solid and liquid wastes and discharges information and cooling water intake information...

  20. Interaction of Water Vapor with the Surfaces of Imidazolium-Based Ionic Liquid Nanoparticles and Thin Films

    E-print Network

    Nizkorodov, Sergey

    of imidazolium-based ILs with water.3,8-35 It is understood that both the cation and the anion have an effect ([CnMIM+ ], n = number of carbons on the linear alkyl chain) cations and various anions at room of absorbed water in ILs. INTRODUCTION Ionic liquids (ILs) are salts, typically composed of organic cations

  1. P2A.4 On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby Frisch

    E-print Network

    Zuidema, Paquita

    using cloud radars have been used to retrieve the effective radius from the reflectivity measurements water flux due to the cloud fall velocity can be evaluated using cloud radar reflectivity measurementsP2A.4 On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby

  2. Crack Extension in Hydraulic Fracturing of Shale Cores Using Viscous Oil, Water, and Liquid Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Bennour, Ziad; Ishida, Tsuyoshi; Nagaya, Yuya; Chen, Youqing; Nara, Yoshitaka; Chen, Qu; Sekine, Kotaro; Nagano, Yu

    2015-07-01

    We performed hydraulic fracturing experiments on cylindrical cores of anisotropic shale obtained by drilling normal to the sedimentary plane. Experiments were conducted under ambient condition and uniaxial stresses, using three types of fracturing fluid: viscous oil, water, and liquid carbon dioxide (L-CO2). In the experiments using water and oil, cracks extended along the loading direction normal to the sedimentary plane under the uniaxial loading and extended along the sedimentary plane without loading. These results suggest that the direction of crack extension is strongly affected by in situ stress conditions. Fluorescent microscopy revealed that hydraulic fracturing with viscous oil produced linear cracks with few branches, whereas that with water produced cracks with many branches inclining from the loading axis. Statistical analysis of P wave polarity of acoustic emission waveforms showed that viscous oil tended to induce Mode I fracture, whereas both water and L-CO2 tended to induce Mode II fracture. Crack extension upon injection of L-CO2 was independent of loading condition unlike extension for the other two fluids. This result seemed attributable to the low viscosity of L-CO2 and was consistent with previous observations for granite specimens that low-viscosity fluids like CO2 tend to induce widely extending cracks with many branches, with Mode II fractures being dominant. These features are more advantageous for shale gas production than those induced by injection of conventional slick water.

  3. Amphiphile micelle structures in the protic ionic liquid ethylammonium nitrate and water.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Caruso, Rachel A; Drummond, Calum J

    2015-01-01

    Micelles formed by amphiphiles in a protic ionic liquid (PIL), ethylammonium nitrate (EAN), were investigated using synchrotron small-angle X-ray scattering and contrasted with those that formed in water. The amphiphiles studied were cationic hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium bromide (HDPB) and nonionic poly(oxyethylene) (10) oleyl ether (Brij 97) and Pluronic ethylene oxide-propylene oxide-ethylene oxide block copolymer (P123). The scattering patterns were analyzed using spherical, core-shell, and cylindrical scattering models. The apparent micelle shape and size of the surfactants and the block copolymer in the PIL have been reported. At low amphiphile concentrations (<10 wt %) spherical micelles were preferentially formed for all the amphiphiles in EAN. The micelles formed by the two cationic amphiphiles in EAN and water were similar, though different scattering models were required predominantly due to the ionic nature of EAN. The two nonionic amphiphiles formed micelles with similar core radii in water and in EAN. However, the micelle shells composed of ethylene oxide groups fitted to a significantly thicker layer in water compared to EAN. At high concentrations (>10 wt %) in EAN and water, there was a preference for cylindrical micelles for CTAC, HDPB, and Brij 97; however, the P123 micelles remained spherical. PMID:25490177

  4. Cooperative versus dispersion effects: What is more important in an associated liquid such as water?

    NASA Astrophysics Data System (ADS)

    Kirchner, Barbara

    2005-11-01

    We implemented the quantum cluster equilibrium theory in our postprocessing program PEACEMAKER. This program may be run in conjunction with the very efficient vibrational frequency analysis code SNF and can therefore provide access to all electronic structure programs combined with this program. We applied the quantum cluster equilibrium theory in order to investigate the influence of a wide range of electronic structure models on the description of the liquid state. This investigation revealed much about the relevance of approximations in modern simulations of associated liquids such as water. While it is often claimed that the use of density-functional theory in condensed matter is leading to gravely erroneous results, we found that, contrary to these assertions, the exact exchange functional B3LYP and the gradient-corrected functional BP perform very well in combination with sizable basis sets as compared to second-order Møller-Plesset perturbation theory employing the same basis set. The use of density-functional theory with smaller basis sets does, in fact, lead to better results in the liquid state than the use of second-order Møller-Plesset perturbation theory in combination with these small basis sets. Most importantly, the neglect of cooperative effects disturbs a good description much more evenly if we apply second-order Møller-Plesset perturbation theory in combination with large basis sets than density-functional theory including cooperativity with smaller basis sets or Hartree-Fock using a very small basis set.

  5. Early Mars was wet but not warm: Erosion, fluvial features, liquid water habitats, and life below freezing

    NASA Technical Reports Server (NTRS)

    Mckay, C. P.; Davis, W. L.

    1993-01-01

    There is considerable evidence that Mars had liquid water early in its history and possibly at recurrent interval. It has generally been assumed that this implied that the climate was warmer as a result of a thicker CO2 atmosphere than at the present. However, recent models suggest that Mars may have had a thick atmosphere but may not have experienced mean annual temperatures above freezing. In this paper we report on models of liquid water formation and maintenance under temperatures well below freezing. Our studies are based on work in the north and south polar regions of Earth. Our results suggest that early Mars did have a thick atmosphere but precipitation and hence erosion was rare. Transient liquid water, formed under temperature extremes and maintained under thick ice covers, could account for the observed fluvial features. The main difference between the present climate and the early climate was that the total surface pressure was well above the triple point of water.

  6. Kinetics and mechanism of isobutene formation from t-butanol in hot liquid water

    SciTech Connect

    Xu, X.; Antal, M.J. Jr. . Dept. of Mechanical Engineering Univ. of Hawaii, Honolulu, HI )

    1994-09-01

    Isobutene is the only product of the uncatalyzed and acid-catalyzed dehydration of tert-butanol in compressed liquid water at 250 C. The uncatalyzed dehydration reaction is fast: equilibrium is established after about 30 s. Only one of many chemically-motivated kinetic models is able to fit all the experimental data. This model presumes a heterolytic dehydration mechanism that involves protonated alcohol, carbocation, di-tert-butyl ether, and protonated ether as intermediates. The model permits tert-butanol to dissociated as both an Arrhenius acid and a Bronsted acid while catalyzing its dehydration to isobutene. The pK[sub a] of tert-butanol at 250 C is predicted to be about 9, whereas its value at normal temperature and pressure is 18. This 10[sup 9] increase in the K[sub a] value of tert-butanol hints of the promising new world of reaction chemistry in near- and supercritical water.

  7. Reverse Monte Carlo investigations concerning recent isotopic substitution neutron diffraction data on liquid water

    E-print Network

    Pethes, Ildikó

    2015-01-01

    Although liquid water has been studied for many decades by (X-ray and neutron) diffraction measurements, new experimental results keep appearing, virtually every year. The reason for this is that neither X-ray, nor neutron diffraction data are trivial to correct and interpret for this essential substance. Since X-rays are somewhat insensitive to hydrogen, neutron diffraction with (most frequently, H/D) isotopic substitution is vital for investigating the most important feature in water: hydrogen bonding. Here, the two very recent sets of neutron diffraction data are considered, both exploiting the contrast between light and heavy hydrogen, $^1$H and $^2$H, in different ways. Reverse Monte Carlo structural modeling is applied for constructing large structural models that are as consistent as possible with all experimental information, both in real and reciprocal space. The method has also proven to be useful for revealing where possible small inconsistencies appear during primary data processing: for one neutr...

  8. Presence of carbamate pesticides in environmental waters from the northwest of Mexico: determination by liquid chromatography.

    PubMed

    García de Llasera, M P; Bernal-González, M

    2001-06-01

    A study on the presence of carbamate pesticides, namely aldicarb, aldicarb sulfoxide, baygon, benthiocarb, carbofuran, 3-hydroxycarbofuran, carbaryl, desmedipham, methiocarb, methomyl, thiodicarb, oxamyl, and propham was made in ground and surface waters from an agricultural zone of the Yaqui Valley located in northwest Mexico. Trace determinations were made by liquid chromatography (LC) with post-column fluorescence detection (EPA method 531.1) or LC-diode array UV detection coupled on-line to a solid-phase extraction (SPE) system and using a 13 x 4.6 mm i.d. precolumn and a 150 x 4.6 mm i.d. analytical column, both packed with a C18 silica. Results indicated that the level of contamination with methiocarb was 5.4 micrograms/L in a groundwater sample and that for 3-hydroxycarbofuran was 18 micrograms/L in a surface water sample. This study provides the basis for a future monitoring program. PMID:11337839

  9. Significantly enhancing enzymatic hydrolysis of rice straw after pretreatment using renewable ionic liquid-water mixtures.

    PubMed

    Hou, Xue-Dan; Li, Ning; Zong, Min-Hua

    2013-05-01

    Pretreatment of rice straw by using renewable cholinium lysine ionic liquid ([Ch][Lys] IL)-water mixtures and subsequent enzymatic hydrolysis of the residues were conducted in this work. There is a clear correlation between the delignification capacity of the pretreatment solvent and its basicity. After pretreatment, surface area and pore volume of rice straw increased significantly, which substantially improved polysaccharides accessibility to enzymes and thus enhanced polysaccharides digestion. By carefully controlling the pretreatment severity (IL content, temperature and duration), loss of readily extractable xylan could be minimized. The sugar yields of 81% for glucose and 48% for xylose were achieved in the enzymatic hydrolysis of rice straw after pretreatment with 20% [Ch][Lys]-water mixture at 90 °C for 1 h. This pretreatment process is highly promising for industrial application because of high sugar yields, low energy input, short pretreatment time, and being environmentally benign and highly tolerant to moisture. PMID:23567718

  10. Trends in Particle-phase Liquid Water Measurements During the Southern Oxidant and Aerosol Study

    NASA Astrophysics Data System (ADS)

    Nguyen, T. V.; Petters, M. D.; Carlton, A. G.; Suda, S.

    2013-12-01

    Particle-phase liquid water (H2Optcl) contributes to total aerosol mass concentrations. Previous studies established links between inorganic species, particle hygroscopicity, ambient relative humidity, and condensed phase liquid water. These relationships are also included in thermodynamic modules of atmospheric chemistry models. Conversely, relationships between H2Optcl and organic species are poorly understood, and there are few field measurements linking the two. In this study, we present in situ measurements of H2Optcl using a newly developed technique - the semi-volatile differential mobility analysis (SVDMA). Measurements were conducted June 1 - July 15, 2013, during the Southern Oxidant and Aerosol Study (SOAS) in the southeast U.S., a biogenically dominated and photochemically active environment impacted by anthropogenic pollution and known to contain high concentrations of organic aerosol mass. The SVDMA measures volume distributions of ambient atmospheric aerosols in three states: unperturbed, dried, and dried then re-humidified. Unperturbed measurements characterize the aerosol distribution at ambient conditions. For dry spectra, the sample is routed through a cold trap (?T = -30K) upstream of the DMA inlet. The total volume of water and semi-volatile organic compounds (SVOCs) lost during drying is quantified by differencing dry and unperturbed volumes from the integrated size spectra, while SVOC volumes are quantified by re-humidifying the sample and referencing to the unperturbed state. Results indicate that liquid water is an important contributor to ambient aerosol volume in the southeast U.S. during the early morning period when the relative humidity differential is largest. Measured H2Optcl volumes can be characterized by hygroscopicity parameter ? ranging from 0.2 to 0.3, which is consistent with a mix of hygroscopic organic and inorganic compounds. Both H2Optcl and ? peak in the early morning when ambient relative humidity is decreasing, suggesting that changes in aerosol composition may occur on short time scales. We also find that the unperturbed and the dried then re-humidified aerosol volumes do not exhibit statistically significant differences, demonstrating that either water-mediated partitioning of SVOCs is reversible or that the effect is smaller than the measurement uncertainty. These results will likely be useful in future improvements of chemical mechanisms in atmospheric photochemical models, enabling more accurate model predictions for climate and air quality.

  11. Probing Properties of Glassy Water and Other Liquids with Site Selective Spectroscopies

    SciTech Connect

    Nhan Chuong Dang

    2005-08-12

    The standard non-photochemical hole burning (NPHB) mechanism, which involves phonon-assisted tunneling in the electronically excited state, was originally proposed to explain the light-induced frequency change of chemically stable molecules in glassy solids at liquid helium temperatures by this research group more than two decades ago. The NPHB mechanism was then further elucidated and the concept of intrinsic to glass configurational relaxation processes as pre-mediating step to the hole burning process was introduced. The latter provided the theoretical basis for NPHB to evolve into a powerful tool probing the dynamics and nature of amorphous media, which aside from ''simple'' inorganic glasses may include also ''complex'' biological systems such as living cells and cancerous/normal tissues. Presented in this dissertation are the experimental and theoretical results of hole burning properties of aluminum phthalocyanine tetrasulphonate (APT) in several different matrices: (1) hyperquenched glassy water (HGW); (2) cubic ice (I{sub c}); and (3) water confined into poly(2-hydroxyethylmethacrylate) (poly-HEMA). In addition, results of photochemical hole burning (PHB) studies obtained for phthalocyanine tetrasulphonate (PcT) in HGW and free base phthalocyanine (Pc) in ortho-dichlorobenzene (DCB) glass are reported. The goal of this dissertation was to provide further evidence supporting the NPHB mechanism and to provide more insight that leads to a better understanding of the kinetic events (dynamics) in glasses, and various dynamical processes of different fluorescent chromorphores in various amorphous solids and the liquid that exist above the glass transition temperature (T{sub g}). The following issues are addressed in detail: (1) time evolution of hole being burned under different conditions and in different hole burning systems; (2) temperature dependent hole profile; and (3) the structure/dynamics of water in confined space, which has been studied, in part because of the importance of non-freezable water in biological systems.

  12. Computational studies of atmospherically-relevant chemical reactions in water clusters and on liquid water and ice surfaces.

    PubMed

    Gerber, R Benny; Varner, Mychel E; Hammerich, Audrey D; Riikonen, Sampsa; Murdachaew, Garold; Shemesh, Dorit; Finlayson-Pitts, Barbara J

    2015-02-17

    CONSPECTUS: Reactions on water and ice surfaces and in other aqueous media are ubiquitous in the atmosphere, but the microscopic mechanisms of most of these processes are as yet unknown. This Account examines recent progress in atomistic simulations of such reactions and the insights provided into mechanisms and interpretation of experiments. Illustrative examples are discussed. The main computational approaches employed are classical trajectory simulations using interaction potentials derived from quantum chemical methods. This comprises both ab initio molecular dynamics (AIMD) and semiempirical molecular dynamics (SEMD), the latter referring to semiempirical quantum chemical methods. Presented examples are as follows: (i) Reaction of the (NO(+))(NO3(-)) ion pair with a water cluster to produce the atmospherically important HONO and HNO3. The simulations show that a cluster with four water molecules describes the reaction. This provides a hydrogen-bonding network supporting the transition state. The reaction is triggered by thermal structural fluctuations, and ultrafast changes in atomic partial charges play a key role. This is an example where a reaction in a small cluster can provide a model for a corresponding bulk process. The results support the proposed mechanism for production of HONO by hydrolysis of NO2 (N2O4). (ii) The reactions of gaseous HCl with N2O4 and N2O5 on liquid water surfaces. Ionization of HCl at the water/air interface is followed by nucleophilic attack of Cl(-) on N2O4 or N2O5. Both reactions proceed by an SN2 mechanism. The products are ClNO and ClNO2, precursors of atmospheric atomic chlorine. Because this mechanism cannot result from a cluster too small for HCl ionization, an extended water film model was simulated. The results explain ClNO formation experiments. Predicted ClNO2 formation is less efficient. (iii) Ionization of acids at ice surfaces. No ionization is found on ideal crystalline surfaces, but the process is efficient on isolated defects where it involves formation of H3O(+)-acid anion contact ion pairs. This behavior is found in simulations of a model of the ice quasi-liquid layer corresponding to large defect concentrations in crystalline ice. The results are in accord with experiments. (iv) Ionization of acids on wet quartz. A monolayer of water on hydroxylated silica is ordered even at room temperature, but the surface lattice constant differs significantly from that of crystalline ice. The ionization processes of HCl and H2SO4 are of high yield and occur in a few picoseconds. The results are in accord with experimental spectroscopy. (v) Photochemical reactions on water and ice. These simulations require excited state quantum chemical methods. The electronic absorption spectrum of methyl hydroperoxide adsorbed on a large ice cluster is strongly blue-shifted relative to the isolated molecule. The measured and calculated adsorption band low-frequency tails are in agreement. A simple model of photodynamics assumes prompt electronic relaxation of the excited peroxide due to the ice surface. SEMD simulations support this, with the important finding that the photochemistry takes place mainly on the ground state. In conclusion, dynamics simulations using quantum chemical potentials are a useful tool in atmospheric chemistry of water media, capable of comparison with experiment. PMID:25647299

  13. Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump

    NASA Technical Reports Server (NTRS)

    Skelley, Stephen; Zoladz, Thomas

    1999-01-01

    As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6-blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Results showed excellent correlation between the predicted and experimentally measured pump head rise at low suction specific speeds. Likewise, only small circumferential variations in steady-state impeller exit and radial diffuser pressure distributions were observed from 80% to 120% of the design flow coefficient, matching the computational predictions and confirming that the integrated design approach has minimized any exit volute-induced distortions. The test article exhibited suction performance trends typically observed in inducer designs with virtually constant head rise with decreasing inlet pressure until complete pump head breakdown. Unfortunately, the net positive suction head at 3% head fall-off occurred far below that predicted at all tested flow coefficients, resulting in a negative net positive suction head margin at the design point in water. Additional testing to map the unsteady pressure environment was conducted and interesting rotating phenomena at the inducer inlet were observed. These rotating phenomena's cell numbers, direction, and speed were correlated with pump operating parameters. The impact of the unsteady phenomena and their corresponding energy losses on the unexpectedly poor pump performance is also discussed.

  14. Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump

    NASA Technical Reports Server (NTRS)

    Skelley, Stephen; Zoladz, Thomas

    2001-01-01

    As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6- blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Initial results showed acceptable correlation between the predicted and experimentally measured pump head rise at low suction specific speeds. Likewise, only small circumferential variations in steady-state were observed from 80% to 120% of the design flow coefficient, matching the computational predictions and confirming that the integrated design approach has minimized any exit volute-induced distortions. The test article exhibited suction performance trends typically observed in inducer designs with virtually constant head rise with decreasing inlet pressure until complete pump head breakdown. Unfortunately, the net positive suction head at 3% head fall-off occurred far below that predicted at all tested flow coefficients, resulting in a negative net positive suction head margin at the design point in water. Additional testing to map the unsteady pressure environment was conducted and cavitation-induced flow disturbances at the inducer inlet were observed. Two distinct disturbances were identified, one rotating and one stationary relative to the fixed frame of reference, while the transition from one regime to the next produced significant effects on the steady state pump performance. The impact of the unsteady phenomena and the corresponding energy losses on the unexpectedly poor pump performance is also discussed.

  15. Investigation of one inverse problem in case of modeling water areas with "liquid" boundaries

    NASA Astrophysics Data System (ADS)

    Sheloput, Tatiana; Agoshkov, Valery

    2015-04-01

    In hydrodynamics often appears the problem of modeling water areas (oceans, seas, rivers, etc.) with "liquid" boundaries. "Liquid" boundary means set of those parts of boundary where impermeability condition is broken (for example, straits, bays borders, estuaries, interfaces of oceans). Frequently such effects are ignored: for "liquid" boundaries the same conditions are used as for "solid" ones, "material boundary" approximation is applied [1]. Sometimes it is possible to interpolate the results received from models of bigger areas. Moreover, approximate estimates for boundary conditions are often used. However, those approximations are not always valid. Sometimes errors in boundary condition determination could lead to a significant decrease in the accuracy of the simulation results. In this work one way of considering the problem mentioned above is described. According to this way one inverse problem on reconstruction of boundary function in convection-reaction-diffusion equations which describe transfer of heat and salinity is solved. The work is based on theory of adjoint equations [2] and optimal control, as well as on common methodology of investigation inverse problems [3]. The work contains theoretical investigation and the results of computer simulation applied for the Baltic Sea. Moreover, conditions and restrictions that should be satisfied for solvability of the problem are entered and justified in the work. Submitted work could be applied for the solution of more complicated inverse problems and data assimilation problems in the areas with "liquid" boundaries; also it is a step for developing algorithms on computing level, speed, temperature and salinity that could be applied for real objects. References 1. A. E. Gill. Atmosphere-ocean dynamics. // London: Academic Press, 1982. 2. G. I. Marchuk. Adjoint equations. // Moscow: INM RAS, 2000, 175 p. (in Russian). 3. V.I. Agoshkov. The methods of optimal control and adjoint equations in problems of mathematical physics. // Moscow: INM RAS, 2003, 256 p. (in Russian).

  16. Isotopic mass-dependence of metal cation diffusion coefficients in liquid water

    SciTech Connect

    Bourg, I.C.; Richter, F.M.; Christensen, J.N.; Sposito, G.

    2009-01-11

    Isotope distributions in natural systems can be highly sensitive to the mass (m) dependence of solute diffusion coefficients (D) in liquid water. Isotope geochemistry studies routinely have assumed that this mass dependence either is negligible (as predicted by hydrodynamic theories) or follows a kinetic-theory-like inverse square root relationship (D {proportional_to} m{sup -0.5}). However, our recent experimental results and molecular dynamics (MD) simulations showed that the mass dependence of D is intermediate between hydrodynamic and kinetic theory predictions (D {proportional_to} m{sup -{beta}} with 0 {<=} {beta} < 0.2 for Li{sup +}, Cl{sup -}, Mg{sup 2+}, and the noble gases). In this paper, we present new MD simulations and experimental results for Na{sup +}, K{sup +}, Cs{sup +}, and Ca{sup 2+} that confirm the generality of the inverse power-law relation D {proportional_to} m{sup -{beta}}. Our new findings allow us to develop a general description of the influence of solute valence and radius on the mass dependence of D for monatomic solutes in liquid water. This mass dependence decreases with solute radius and with the magnitude of solute valence. Molecular-scale analysis of our MD simulation results reveals that these trends derive from the exponent {beta} being smallest for those solutes whose motions are most strongly coupled to solvent hydrodynamic modes.

  17. An economical dual hot-wire liquid water flux probe design

    NASA Astrophysics Data System (ADS)

    LeBoeuf, Richard L.; de Dios Rivera, Juan; de la Jara, Emilio

    2015-01-01

    The velocity, liquid water content (LWC) and their product, the liquid water flux (LWF), are of interest for research in environmental sciences, fog collection, and free-space communications. This paper provides a design for an economical dual hot-wire LWF probe, which enables the ground-based measurement of velocity, LWC and LWF. The design accounts for the droplet deposition efficiency, prong conduction, saturation and sensitivity. The operating mode and probe configurations are described. Two 125 ?m diameter, 5 cm long platinum wires having 2 and 50 °C wire to air temperature offsets would yield measurement uncertainties of about 6% for velocity and from 8 to 22% for the LWC and from 2 to 17% for the LWF given velocities in the range 2 to 8 m/s and LWC in the range 0.2 to 0.8 g/m3. The lower uncertainties correspond to higher LWF, which is of particular interest in fog collection projects. The recurring costs of the instrument's mechanical and electrical components would be about US 150 per unit. Therefore, the design presented herein is a viable option for large-scale sensor networks.

  18. Influence of water on the interfacial behavior of gallium liquid metal alloys.

    PubMed

    Khan, Mohammad R; Trlica, Chris; So, Ju-Hee; Valeri, Michael; Dickey, Michael D

    2014-12-24

    Eutectic gallium indium (EGaIn) is a promising liquid metal for a variety of electrical and optical applications that take advantage of its soft and fluid properties. The presence of a rapidly forming oxide skin on the surface of the metal causes it to stick to many surfaces, which limits the ability to easily reconfigure its shape on demand. This paper shows that water can provide an interfacial slip layer between EGaIn and other surfaces, which allows the metal to flow smoothly through capillaries and across surfaces without sticking. Rheological and surface characterization shows that the presence of water also changes the chemical composition of the oxide skin and weakens its mechanical strength, although not enough to allow the metal to flow freely in microchannels without the slip layer. The slip layer provides new opportunities to control and actuate liquid metal plugs in microchannels-including the use of continuous electrowetting-enabling new possibilities for shape reconfigurable electronics, sensors, actuators, and antennas. PMID:25469554

  19. A Monte Carlo program for the analysis of low-energy electron tracks in liquid water

    NASA Astrophysics Data System (ADS)

    Wiklund, Kristin; Fernández-Varea, José M.; Lind, Bengt K.

    2011-04-01

    A Monte Carlo code for the event-by-event simulation of electron transport in liquid water is presented. The code, written in C++, can accommodate different interaction models. Currently it implements cross sections for ionizing collisions calculated with the model developed by Dingfelder et al (1998 Radiat. Phys. Chem. 53 1-18, 2008 Radiat. Res. 169 584-94) and cross sections for elastic scattering computed within the static-exchange approximation (Salvat et al 2005 Comput. Phys. Commun. 165 157-90). The latter cross sections coincide with those recommended in ICRU Report 77 (2007). Other included interaction mechanisms are excitation by electron impact and dissociative attachment. The main characteristics of the code are summarized. Various track penetration parameters, including the detour factor, are defined as useful tools to quantify the geometrical extent of electron tracks in liquid water. Results obtained with the present microdosimetry code are given in the form of probability density functions for initial electron kinetic energies ranging from 0.1 to 10 keV. The sensitivity of the simulated distributions to the choice of alternative physics models has been briefly explored. The discrepancies with equivalent simulations reported by Wilson et al (2004 Radiat. Res. 161 591-6) stem from the adopted cross sections for elastic scattering, which determine largely the spatial evolution of low-energy electron tracks.

  20. Computing the dielectric constant of liquid water at constant dielectric displacement

    E-print Network

    Chao Zhang; Michiel Sprik

    2015-10-02

    The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement D. The method to constrain the electric displacement is the finite temperature classical variant of the constant-D method developed by Stengel, Spaldin and Vanderbilt (Nat. Phys. 2009, 5: 304). There is also a modification of this scheme imposing fixed values of the macroscopic field E. The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at D = 0 and E = 0 and two from the variation of polarization with finite D and E. It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies however, with constant D calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polarization accelerating constant D calculations.