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Sample records for liquid water polymorphism

  1. Are There Two Forms of Liquid Water?

    NASA Astrophysics Data System (ADS)

    Stanley, H. E.

    We will introduce some of the 73 documented anomalies of the most complex of liquids, water--focusing on recent progress in understanding these anomalies by combining information provided by recent experiments and simulations on water in bulk, nanoconfined and biological environments designed to test the hypothesis that liquid water has behavior consistent with the novel phenomenon of ``liquid polymorphism'' in that water can exist in two distinct phases [1]. We will also discuss very recent work on nanoconfined water anomalies as well as the apparently related, and highly unusual, behavior of water in biological environments. Finally, we will discuss how the general concept of liquid polymorphism is proving useful in understanding anomalies in other liquids, such as silicon, silica, and carbon, as well as metallic glasses, which have in common that they are characterized by two characteristic length scales in their interactions.This work has been supported by the NSF Chemistry Division grant CHE-1213217 and was performed in collaboration with, among others, C. A. Angell, S. V. Buldyrev, S.-H. Chen, D. Corradini, P. G. Debenedetti, G. Franzese, P. Kumar, E. Lascaris, F. Mallamace, O. Mishima, P. H. Poole, S. Sastry, F. Sciortino, and L. Xu. H. E. Stanley, Editor, Liquid Polymorphism, Vol. 152 in Advances in Chemical Physics, S. A. Rice, Series Editor (Wiley, New York, 2013).

  2. 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.

  3. Mars: occurrence of liquid water.

    PubMed

    Ingersoll, A P

    1970-05-22

    In the absence of juvenile liquid water, condensation of water vapor to ice and subsequent melting of ice are the only means of producing liquid water on the martian surface. However, the evaporation rate is so high that the available heat sources cannot melt pure ice. Liquid water is therefore limited to concentrated solutions of strongly deliquescent salts.

  4. The Structure and Dynamics of Monatomic Liquid Polymorphs; Case Studies in Cerium and Germanium

    NASA Astrophysics Data System (ADS)

    Cadien, Adam

    The study of liquid polymorphism is at the frontier of fundamental thermodynamics and materials science. Liquid polymorphism occurs when a single material has multiple structurally unique liquid phases. Water was the first substance suggested to exhibit multiple liquid phases, a number of monatomic semiconductors and metals have been found to exhibit similar characteristics since then. A better understanding of the liquid-liquid phase transition is needed to tackle problems in glass sciences, it is also relevant to geophysical studies of the Earth's core and mantle and has applications in nanotechnology. Computational methods are critical to developing a better understanding of liquids. Through simulation thermodynamic obstacles that hamper experiments can be artificially bypassed, metastable regions outside the equilibrium phase diagram can be accessed and all of the properties of the system are directly recorded. Computationally it is much simpler to iterate over a range of environmental variables such as temperature, pressure and composition, and measure a system's response. In this thesis ab-initio and semi-empirical approximations are used to accurately describe the complex many body interactions that take place in liquids. Two independent case studies of liquid polymorphism are presented here. The first is a stable liquid-liquid phase transition was found to occur in Cerium which was initially discovered through X-Ray diffraction experiments and later confirmed through simulation. This phase transition is predicted to end at a critical point. The second is a comprehensive study of the structure and dynamics of Germanium's many metastable amorphous and liquid phases. This is currently the largest ab-initio based study of the dynamics of Germanium's metastable liquid phases. Methods ranging from the mean square displacement to the van Hove function and intermediate scattering function are introduced and analyzed. The micro-structural characteristics are

  5. Is Every Transparent Liquid Water?

    NASA Astrophysics Data System (ADS)

    Hugerat, Muhamad; Basheer, Sobhi

    2001-08-01

    The accepted description for water in schools worldwide is a transparent and colorless liquid. Since students in lower grades (ages 8-13) often see warning signs "Do not drink this liquid--it is not water", we believe that presenting experiments that demonstrate the inadequacy of the accepted description for water would be beneficial for teachers and their students to practice in their schools. These activities provide simple experiments that introduce students to important characteristics of different compounds that have similar external appearance. The characteristics presented here include polarity, electric conductivity, color change due to presence of an acid-base indicator, and electrolysis.

  6. 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.

  7. Polymorphism, mesomorphism, and metastability of monoelaidin in excess water.

    PubMed Central

    Chung, H; Caffrey, M

    1995-01-01

    The polymorphic and metastable phase behavior of monoelaidin dry and in excess water was studied by using high-sensitivity differential scanning calorimetry and time-resolved x-ray diffraction in the temperature range of 4 degrees C to 60 degrees C. To overcome problems associated with a pronounced thermal history-dependent phase behavior, simultaneous calorimetry and time-resolved x-ray diffraction measurements were performed on individual samples. Monoelaidin/water samples were prepared at room temperature and stored at 4 degrees C for up to 1 week before measurement. The initial heating scan from 4 degrees C to 60 degrees C showed complex phase behavior with the sample in the lamellar crystalline (Lc0) and cubic (Im3m, Q229) phases at low and high temperatures, respectively. The Lc0 phase transforms to the lamellar liquid crystalline (L alpha) phase at 38 degrees C. At 45 degrees C, multiple unresolved lines appeared that coexisted with those from the L alpha phase in the low-angle region of the diffraction pattern that have been assigned previously to the so-called X phase (Caffrey, 1987, 1989). With further heating the X phase converts to the Im3m cubic phase. Regardless of previous thermal history, cooling calorimetric scans revealed a single exotherm at 22 degrees C, which was assigned to an L alpha+cubic (Im3m, Q229)-to-lamellar gel (L beta) phase transition. The response of the sample to a cooling followed by a reheating or isothermal protocol depended on the length of time the sample was incubated at 4 degrees C. A model is proposed that reconciles the complex polymorphic, mesomorphic, and metastability interrelationships observed with this lipid/water system. Dry monoelaidin exists in the lamellar crystalline (beta) phase in the 4 degrees C to 45 degrees C range. The beta phase transforms to a second lamellar crystalline polymorph identified as beta* at 45 degrees C that subsequently melts at 57 degrees C. The beta phase observed with dry monoelaidin is

  8. 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).

  9. 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.

  10. 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.

  11. Liquid Water, the ``Most Complex'' Liquid: New Results in Bulk, Nanoconfined, and Biological Environments

    NASA Astrophysics Data System (ADS)

    Stanley, H. Eugene

    2010-03-01

    We will introduce some of the 63 anomalies of the most complex of liquids, water. We will demonstrate some recent progress in understanding these anomalies by combining information provided by recent experiments and simulations on water in bulk, nanoconfined, and biological environments. We will interpret evidence from recent experiments designed to test the hypothesis that liquid water may display ``polymorphism'' in that it can exist in two different phases---and discuss recent work on water's transport anomalies [1] as well as the unusual behavior of water in biological environments [2]. Finally, we will discuss how the general concept of liquid polymorphism [3] is proving useful in understanding anomalies in other liquids, such as silicon, silica, and carbon, as well as metallic glasses, which have in common that they are characterized by two characteristic length scales in their interactions. This work was supported by NSF Chemistry Division, and carried out in collaboration with a number of colleagues, chief among whom are C. A. Angell, M. C. Barbosa, M. C. Bellissent, L. Bosio, F. Bruni, S. V. Buldyrev, M. Canpolat, S. -H. Chen, P. G. Debenedetti, U. Essmann,G. Franzese, A. Geiger, N. Giovambattista, S. Han, P. Kumar, E. La Nave,G. Malescio, F. Mallamace, M. G. Mazza, O. Mishima, P. Netz, P. H. Poole, P. J. Rossky, R. Sadr,S. Sastry, A. Scala, F. Sciortino, A. Skibinsky, F. W. Starr, K. C. Stokely J. Teixeira, L. Xu, and Z. Yan.[4pt] [1] L. Xu, F. Mallamace, Z. Yan, F. W. Starr, S. V. Buldyrev, and H. E. Stanley, ``Appearance of a Fractional Stokes-Einstein Relation in Water and a Structural Interpretation of Its Onset,'' Nature Physics 5, 565--569 (2009). [0pt] [2] P. Kumar, Z. Yan, L. Xu, M. G. Mazza, S. V. Buldyrev, S. -H. Chen. S. Sastry, and H. E. Stanley, ``Glass Transition in Biomolecules and the Liquid-Liquid Critical Point of Water,'' Phys. Rev. Lett. 97, 177802 (2006). [0pt] [3] H. E. Stanley, ed. , Liquid Polymorphism [Advances in Chemical Physics

  12. Depolarization of water in protic ionic liquids.

    PubMed

    Zahn, Stefan; Wendler, Katharina; Delle Site, Luigi; Kirchner, Barbara

    2011-09-07

    A mixture of the protic ionic liquid mono-methylammonium nitrate with 1.6 wt% water was investigated from Car-Parrinello molecular dynamics simulations. In contrast to imidazolium-based ionic liquids, the cation possesses strong directional hydrogen bonds to water and all hydrogen bonds in the mixture have a comparable strength. This results in a good incorporation of water into the hydrogen bond network of mono-methylammonium nitrate and a tetrahedral hydrogen bond coordination of water. Hence, one might expect a larger dipole moment of water in the investigated mixture compared to neat water due to the good hydrogen bond network incorporation and the charged vicinity of water in the protic ionic liquid. However, the opposite is observed pointing to strong electrostatic screening in protic ionic liquids. Additionally, the influence of water on the properties of the protic ionic liquid is discussed.

  13. 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.

  14. Raman lidar observations of cloud liquid water.

    PubMed

    Rizi, Vincenzo; Iarlori, Marco; Rocci, Giuseppe; Visconti, Guido

    2004-12-10

    We report the design and the performances of a Raman lidar for long-term monitoring of tropospheric aerosol backscattering and extinction coefficients, water vapor mixing ratio, and cloud liquid water. We focus on the system's capabilities of detecting Raman backscattering from cloud liquid water. After describing the system components, along with the current limitations and options for improvement, we report examples of observations in the case of low-level cumulus clouds. The measurements of the cloud liquid water content, as well as the estimations of the cloud droplet effective radii and number densities, obtained by combining the extinction coefficient and cloud water content within the clouds, are critically discussed.

  15. Dipolar correlations in liquid water

    SciTech Connect

    Zhang, Cui; Galli, Giulia

    2014-08-28

    We present an analysis of the dipolar correlations in water as a function of temperature and density and in the presence of simple ionic solutes, carried out using molecular dynamics simulations and empirical potentials. We show that the dipole-dipole correlation function of the liquid exhibits sizable oscillations over nanodomains of about 1.5 nm radius, with several isosbestic points as a function of temperature; the size of the nanodomains is nearly independent on temperature and density, between 240 and 400 K and 0.9 and 1.3 g/cm{sup 3}, but it is substantially affected by the presence of solvated ions. In the same range of thermodynamic conditions, the decay time (τ) of the system dipole moment varies by a factor of about 30 and 1.5, as a function of temperature and density, respectively. At 300 K, we observed a maximum in τ as a function of density, and a corresponding shallow maximum in the tetrahedral order parameter, in a range where the diffusion coefficient, the pressure and the dielectric constant increase monotonically.

  16. Photoresponsive liquid marbles and dry water.

    PubMed

    Tan, Tristan Tsai Yuan; Ahsan, Aniq; Reithofer, Michael R; Tay, Siok Wei; Tan, Sze Yu; Hor, Tzi Sum Andy; Chin, Jia Min; Chew, Benny Kia Jia; Wang, Xiaobai

    2014-04-01

    Stimuli-responsive liquid marbles for controlled release typically rely on organic moieties that require lengthy syntheses. We report herein a facile, one-step synthesis of hydrophobic and oleophobic TiO2 nanoparticles that display photoresponsive wettability. Water liquid marbles stabilized by these photoresponsive TiO2 particles were found to be stable when shielded from ultraviolet (UV) radiation; however, they quickly collapsed after being irradiated with 302 nm UV light. Oil- and organic-solvent-based liquid marbles could also be fabricated using oleophobic TiO2 nanoparticles and show similar UV-induced collapse. Finally, we demonstrated the formation of the micronized form of water liquid marbles, also known as dry water, by homogenization of the TiO2 nanoparticles with water. The TiO2 dry water displayed a similar photoresponse, whereby the micronized liquid marbles collapsed after irradiation and the dry water turned from a free-flowing powder to a paste. Hence, by exploiting the photoresponsive wettability of TiO2, we fabricated liquid marbles and dry water that display photoresponse and studied the conditions required for their collapse.

  17. Global Cloud Liquid Water Path Simulations(.

    NASA Astrophysics Data System (ADS)

    Lemus, Lilia; Rikus, Lawrie; 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.

  18. 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

  19. Water flow and fin shape polymorphism in coral reef fishes.

    PubMed

    Binning, Sandra A; Roche, Dominique G

    2015-03-01

    Water flow gradients have been linked to phenotypic differences and swimming performance across a variety of fish assemblages. However, the extent to which water motion shapes patterns of phenotypic divergence within species remains unknown. We tested the generality of the functional relationship between swimming morphology and water flow by exploring the extent of fin and body shape polymorphism in 12 widespread species from three families (Acanthuridae, Labridae, Pomacentridae) of pectoral-fin swimming (labriform) fishes living across localized wave exposure gradients. The pectoral fin shape of Labridae and Acanthuridae species was strongly related to wave exposure: individuals with more tapered, higher aspect ratio (AR) fins were found on windward reef crests, whereas individuals with rounder, lower AR fins were found on leeward, sheltered reefs. Three of seven Pomacentridae species showed similar trends, and pectoral fin shape was also strongly related to wave exposure in pomacentrids when fin aspect ratios of three species were compared across flow habitats at very small spatial scales (<100 m) along a reef profile (reef slope, crest, and back lagoon). Unlike fin shape, there were no intraspecific differences in fish body fineless ratio across habitats or depths. Contrary to our predictions, there was no pattern relating species' abundances to polymorphism across habitats (i.e., abundance was not higher at sites where morphology is better adapted to the environment). This suggests that there are behavioral and/or physiological mechanisms enabling some species to persist across flow habitats in the absence of morphological differences. We suggest that functional relationships between swimming morphology and water flow not only structure species assemblages, but are yet another important variable contributing to phenotypic differences within species. The close links between fin shape polymorphism and local water flow conditions appear to be important for

  20. Liquid chromatographic determination of water

    DOEpatents

    Fortier, Nancy E.; Fritz, James 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. 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.

  2. 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

  3. 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.

  4. 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.

  5. Water: A Tale of Two Liquids.

    PubMed

    Gallo, Paola; Amann-Winkel, Katrin; Angell, Charles Austen; Anisimov, Mikhail Alexeevich; Caupin, Frédéric; Chakravarty, Charusita; Lascaris, Erik; Loerting, Thomas; Panagiotopoulos, Athanassios Zois; Russo, John; Sellberg, Jonas Alexander; Stanley, Harry Eugene; Tanaka, Hajime; Vega, Carlos; Xu, Limei; Pettersson, Lars Gunnar Moody

    2016-07-13

    Water is the most abundant liquid on earth and also the substance with the largest number of anomalies in its properties. It is a prerequisite for life and as such a most important subject of current research in chemical physics and physical chemistry. In spite of its simplicity as a liquid, it has an enormously rich phase diagram where different types of ices, amorphous phases, and anomalies disclose a path that points to unique thermodynamics of its supercooled liquid state that still hides many unraveled secrets. In this review we describe the behavior of water in the regime from ambient conditions to the deeply supercooled region. The review describes simulations and experiments on this anomalous liquid. Several scenarios have been proposed to explain the anomalous properties that become strongly enhanced in the supercooled region. Among those, the second critical-point scenario has been investigated extensively, and at present most experimental evidence point to this scenario. Starting from very low temperatures, a coexistence line between a high-density amorphous phase and a low-density amorphous phase would continue in a coexistence line between a high-density and a low-density liquid phase terminating in a liquid-liquid critical point, LLCP. On approaching this LLCP from the one-phase region, a crossover in thermodynamics and dynamics can be found. This is discussed based on a picture of a temperature-dependent balance between a high-density liquid and a low-density liquid favored by, respectively, entropy and enthalpy, leading to a consistent picture of the thermodynamics of bulk water. Ice nucleation is also discussed, since this is what severely impedes experimental investigation of the vicinity of the proposed LLCP. Experimental investigation of stretched water, i.e., water at negative pressure, gives access to a different regime of the complex water diagram. Different ways to inhibit crystallization through confinement and aqueous solutions are

  6. 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.

  7. Human ACE gene polymorphism and distilled water induced cough

    PubMed Central

    Morice, A. H.; Turley, A. J.; Linton, T. K.

    1997-01-01

    BACKGROUND: Inhibitors of angiotensin converting enzyme (ACE) cause a non-productive cough. The insertion/deletion polymorphism of ACE was used as a genetic marker to investigate the relationship between ACE genotype and cough sensitivity. METHODS: A double blind cough challenge was performed in 66 normotensive subjects (34 men) of mean age 34.8 years (range 18-80) using aerosols of distilled water. The number of coughs during the one minute exposure to water was recorded. DNA samples from venous blood were amplified by the polymerase chain reaction and resolved on a 1% agarose gel. They were analysed for the presence of a polymorphism in intron 16 of the ACE gene consisting of an insertion (I) or deletion (D) of an Alu repetitive sequence 287 base pairs long. RESULTS: The distribution of genotypes was 20 II, 26 ID, and 20 DD. The cough response was significantly (p < 0.01) related to the ACE genotype, the mean number of coughs being 15.8, 11.3, and 9.6, respectively, in subjects with the II, ID, and DD genotypes. CONCLUSIONS: The observation that cough challenge is dependent on ACE genotype in normal subjects is evidence of a link between ACE activity and the cough reflex. 


 PMID:9059468

  8. 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

  9. 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.

  10. Liquid water habitats on early Mars

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Davis, Wanda L.

    1992-01-01

    Although the Viking results may indicate that Mars has no life today, the possibility exists that Mars may hold the best record of the events that led to the origin of life. There is direct geomorphological evidence that in the past Mars had large amounts of liquid water on its surface. Atmospheric models would suggest that this early period of hydrological activity was due to the presence of a thick atmosphere and the resulting warmer temperatures. From a biological perspective the existence of liquid water by itself motivates the question of the origin of life on Mars. From studies of the Earth's earliest biosphere, we know that by 3.5 Gyr ago life had originated on Earth and reached a fair degree of biological sophistication. Surface activity and erosion on Earth make it difficult to trace the history of life before the 3.5 Gyr timeframe. If Mars did maintain a clement environment for longer than it took for life to originate on Earth, then the question of the origin of life on Mars follows naturally. Based upon simple models of the evolution of the Martian climate, we divide the history of liquid water habitats on the Martian surface into four epochs based upon the atmospheric temperature and pressure.

  11. Photoelectron Emission Spectroscopy of Liquid Water.

    DTIC Science & Technology

    1981-04-01

    correlated to solvation free energies for H2O+(aq) and OH (aq)., DD ,FO*M 1473 EDITIOOF INOV so iS OBSOLETE Unclassified SECURITY CLASSIFICATION OF THIS PAGE...Photoelectron spectroscopy Reorganization free energy Water, liquid 20. ABSTRACT (Chlnw am ef We, aid* it nooe"mr and 1iEru’h hr 190k le 6) The threshold... energy Et a 10.06 eV (0.002 @V standard deviation) is detemined for phot~oelectron emission by litquid water and is correlated with Et a 8.45 eV for

  12. Separation of THF and water by room temperature ionic liquids.

    PubMed

    Hu, X; Yu, J; Liu, H

    2006-01-01

    Liquid-liquid equilibrium data are presented for mixtures of 1-(2-hydroxyethyl)-3-methylimidazolium chloride or tetrafluoroborate + tetrahydrofuran(THF) + water at 293.15 K. The data presented provides a valuable insight into how the environmentally friendly ionic liquid solvent can have the separation power of THF-water azeotropic systems. The sloping of the tie lines towards the THF vertex is investigated for mixtures of 1-(2-hydroxyethyl)-3-methylimidazolium chloride (or tetrafluoroborate) + THF + water. Selectivity values, derived from the tie line data, indicate that these two ionic liquids are suitable solvents for the liquid-liquid extraction of water from THF.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. Triplet correlation functions in liquid water

    NASA Astrophysics Data System (ADS)

    Dhabal, Debdas; Singh, Murari; Wikfeldt, Kjartan Thor; Chakravarty, Charusita

    2014-11-01

    Triplet correlations have been shown to play a crucial role in the transformation of simple liquids to anomalous tetrahedral fluids [M. Singh, D. Dhabal, A. H. Nguyen, V. Molinero, and C. Chakravarty, Phys. Rev. Lett. 112, 147801 (2014)]. Here we examine triplet correlation functions for water, arguably the most important tetrahedral liquid, under ambient conditions, using configurational ensembles derived from molecular dynamics (MD) simulations and reverse Monte Carlo (RMC) datasets fitted to experimental scattering data. Four different RMC data sets with widely varying hydrogen-bond topologies fitted to neutron and x-ray scattering data are considered [K. T. Wikfeldt, M. Leetmaa, M. P. Ljungberg, A. Nilsson, and L. G. M. Pettersson, J. Phys. Chem. B 113, 6246 (2009)]. Molecular dynamics simulations are performed for two rigid-body effective pair potentials (SPC/E and TIP4P/2005) and the monatomic water (mW) model. Triplet correlation functions are compared with other structural measures for tetrahedrality, such as the O-O-O angular distribution function and the local tetrahedral order distributions. In contrast to the pair correlation functions, which are identical for all the RMC ensembles, the O-O-O triplet correlation function can discriminate between ensembles with different degrees of tetrahedral network formation with the maximally symmetric, tetrahedral SYM dataset displaying distinct signatures of tetrahedrality similar to those obtained from atomistic simulations of the SPC/E model. Triplet correlations from the RMC datasets conform closely to the Kirkwood superposition approximation, while those from MD simulations show deviations within the first two neighbour shells. The possibilities for experimental estimation of triplet correlations of water and other tetrahedral liquids are discussed.

  18. Triplet correlation functions in liquid water

    SciTech Connect

    Dhabal, Debdas; Chakravarty, Charusita; Singh, Murari; Wikfeldt, Kjartan Thor

    2014-11-07

    Triplet correlations have been shown to play a crucial role in the transformation of simple liquids to anomalous tetrahedral fluids [M. Singh, D. Dhabal, A. H. Nguyen, V. Molinero, and C. Chakravarty, Phys. Rev. Lett. 112, 147801 (2014)]. Here we examine triplet correlation functions for water, arguably the most important tetrahedral liquid, under ambient conditions, using configurational ensembles derived from molecular dynamics (MD) simulations and reverse Monte Carlo (RMC) datasets fitted to experimental scattering data. Four different RMC data sets with widely varying hydrogen-bond topologies fitted to neutron and x-ray scattering data are considered [K. T. Wikfeldt, M. Leetmaa, M. P. Ljungberg, A. Nilsson, and L. G. M. Pettersson, J. Phys. Chem. B 113, 6246 (2009)]. Molecular dynamics simulations are performed for two rigid-body effective pair potentials (SPC/E and TIP4P/2005) and the monatomic water (mW) model. Triplet correlation functions are compared with other structural measures for tetrahedrality, such as the O–O–O angular distribution function and the local tetrahedral order distributions. In contrast to the pair correlation functions, which are identical for all the RMC ensembles, the O–O–O triplet correlation function can discriminate between ensembles with different degrees of tetrahedral network formation with the maximally symmetric, tetrahedral SYM dataset displaying distinct signatures of tetrahedrality similar to those obtained from atomistic simulations of the SPC/E model. Triplet correlations from the RMC datasets conform closely to the Kirkwood superposition approximation, while those from MD simulations show deviations within the first two neighbour shells. The possibilities for experimental estimation of triplet correlations of water and other tetrahedral liquids are discussed.

  19. 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 μm-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 μm 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

  20. 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, ρ ≈ 0.9 g/cc) and a high-density liquid (HDL, ρ ≈ 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.

  1. Determination of four heterocyclic insecticides by ionic liquid dispersive liquid-liquid microextraction in water samples.

    PubMed

    Liu, Yu; Zhao, Ercheng; Zhu, Wentao; Gao, Haixiang; Zhou, Zhiqiang

    2009-02-06

    A novel microextraction method termed ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) combining high-performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of insecticides in water samples. Four heterocyclic insecticides (fipronil, chlorfenapyr, buprofezin, and hexythiazox) were selected as the model compounds for validating this new method. This technique combines extraction and concentration of the analytes into one step, and the ionic liquid was used instead of a volatile organic solvent as the extraction solvent. Several important parameters influencing the IL-DLLME extraction efficiency such as the volume of extraction solvent, the type and volume of disperser solvent, extraction time, centrifugation time, salt effect as well as acid addition were investigated. Under the optimized conditions, good enrichment factors (209-276) and accepted recoveries (79-110%) were obtained for the extraction of the target analytes in water samples. The calibration curves were linear with correlation coefficient ranged from 0.9947 to 0.9973 in the concentration level of 2-100 microg/L, and the relative standard deviations (RSDs, n=5) were 4.5-10.7%. The limits of detection for the four insecticides were 0.53-1.28 microg/L at a signal-to-noise ratio (S/N) of 3.

  2. Liquid water sill emplacement on Europa?

    NASA Astrophysics Data System (ADS)

    Craft, K.; Patterson, G. W.; Lowell, R. P.

    2013-12-01

    Recent work has suggested that lithospheric flexure and flanking fractures observed along some ridges on Europa are best explained by the initial presence of a shallow liquid water sill. The emplacement of a sill suggests certain conditions existed that were favorable to water flow from the ocean to the subsurface, stresses that allowed horizontal fracturing for sill emplacement, and liquid water replenishment to enable a sill lifetime of ~ 1000s of years. Here, we investigate whether these conditions could occur and result in sill formation. Previous models of the stresses resulting from ice shell thickening on Europa indicated that fractures can initiate within the shell and propagate both upward toward the surface and downward to the ice-ocean interface. For an ~10 km thick ice shell, we determined that flow velocities for ocean water driven up a vertical fracture by the release of lithostatic pressures are adequate for reaching the subsurface before freezing occurs (LPSC #3033). We propose the next step for sill emplacement could occur through horizontal fracturing. Nominally, the stress field in a material under lithostatic load is conducive to vertical crack propagation. However, factors exist that can cause the stress field to change and propagate cracks horizontally. Seismically imaged terrestrial sills beneath mid-ocean ridges often occur in areas with extensive cracking and/or faulting, suggesting crack interactions may play a key role. Through application of a finite element program, we modeled four stress changing mechanisms and the resulting fracture propagation in a 10 km thick ice shell on Europa: (1) mechanical layering, (2) shallow cracks to the surface, (3) deep cracks from the ocean-ice interface and (4) shallow and deep cracks combined. Results determined that all mechanisms cause some turn in propagation direction, with Model 4 (both shallow and deep cracks) enabling the greatest turn to ~ horizontal. The horizontal extent of the fracture

  3. Polarized View of Supercooled Liquid Water Clouds

    NASA Technical Reports Server (NTRS)

    Alexandrov, Mikhail D.; Cairns, Brian; Van Diedenhoven, Bastiaan; Ackerman, Andrew S.; Wasilewski, Andrzej P.; McGill, Matthew J.; Yorks, John E.; Hlavka, Dennis L.; Platnick, Steven E.; Arnold, G. Thomas

    2016-01-01

    Supercooled liquid water (SLW) clouds, where liquid droplets exist at temperatures below 0 C present a well known aviation hazard through aircraft icing, in which SLW accretes on the airframe. SLW clouds are common over the Southern Ocean, and climate-induced changes in their occurrence is thought to constitute a strong cloud feedback on global climate. The two recent NASA 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 SLW clouds from the high-altitude airborne platform of NASA's ER-2 aircraft. We present an analysis of measurements made by the Research Scanning Polarimeter (RSP) during these experiments accompanied by correlative retrievals from other sensors. The RSP measures both polarized and total reflectance in 9 spectral channels with wavelengths ranging from 410 to 2250 nm. It is a scanning sensor taking samples at 0.8deg intervals within 60deg from nadir in both forward and backward directions. This unique 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 135deg and 165deg. 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 retrieval of the droplet size distribution without assuming a size distribution shape. We present an overview of the RSP campaign datasets available from the NASA GISS website, as well as two detailed examples of the retrievals. In these case studies we focus on cloud fields with spatial features

  4. Liquid penetration inside glass nozzle during bubble departures in water

    NASA Astrophysics Data System (ADS)

    Dzienis, P.; Mosdorf, R.; Augustyniak, J.

    2016-09-01

    Liquid penetration into the glass nozzle with inner diameter of 1 mm during the bubble, departures in distilled (surface tension = 65 mN/m) and not distilled (surface tension = 72 mN/m), water was investigated. It has been shown that dynamics of liquid movement inside the nozzle depend on the water surface tension. Maximum value of liquid penetration inside the nozzle is different for distilled and not distilled water. In not distilled water the depth of liquid penetration into the nozzle depends on air volume flow rate. For desilted water this value is constant.

  5. Ab Initio Quantum Simulations of Liquid Water

    NASA Astrophysics Data System (ADS)

    Gergely, John; Ceperley, David; Gygi, Francois

    2007-03-01

    Some recent efforts at simulating liquid water have employed ``ab initio'' molecular dynamics (AIMD) methods with forces from a version of density functional theory (DFT) and, in some cases, imaginary-time path integrals (PI) to study quantum effects of the protons. Although AIMD methods have met with many successes, errors introduced by the approximations and choices of simulation parameters are not fully understood. We report on path integral Monte Carlo (PIMC) studies of liquid water using DFT energies that provide quantitative benchmarks for PI-AIMD work. Specifically, we present convergence studies of the path integrals and address whether the Trotter number can be reduced by improving the form of the (approximate) action. Also, we assess 1) whether typical AIMD simulations are sufficiently converged in simulation time, i.e., if there is reason to suspect that nonergodic behavior in PI-AIMD methods leads to poor convergence, and 2) the relative efficiency of the methods. E. Schwegler, J.C. Grossman, F. Gygi, G. Galli, J. Chem. Phys 121, 5400 (2004).

  6. The Liquid Treasure Water History Trunk: Learning from the Past.

    ERIC Educational Resources Information Center

    Kesselheim, Alan S.; And Others

    This document is a guide to building a Liquid Treasure Water History Trunk that allows educators and students of all ages to learn about water from a historical perspective. By assembling historical water related items into a meaningful and interesting learning format--The Liquid Treasure Trunk--teachers and students of all ages can gain a glimpse…

  7. 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

  8. Optical Fluorescence Detected from X-ray Irradiated Liquid Water.

    PubMed

    Hans, Andreas; Ozga, Christian; Seidel, Robert; Schmidt, Philipp; Ueltzhöffer, Timo; Holzapfel, Xaver; Wenzel, Philip; Reiß, Philipp; Pohl, Marvin N; Unger, Isaak; Aziz, Emad F; Ehresmann, Arno; Slavíček, Petr; Winter, Bernd; Knie, André

    2017-03-16

    Despite its importance, the structure and dynamics of liquid water are still poorly understood in many apsects. Here, we report on the observation of optical fluorescence upon soft X-ray irradiation of liquid water. Detection of spectrally resolved fluorescence was achieved by a combination of the liquid microjet technique and fluorescence spectroscopy. We observe a genuine liquid-phase fluorescence manifested by a broad emission band in the 170-340 nm (4-7 eV) photon wavelength range. In addition, another narrower emission near 300 nm can be assigned to the fluorescence of OH (A state) in the gas phase, the emitting species being formed by Auger electrons escaping from liquid water. We argue that the newly observed broad-band emission of liquid water is relevant in search of extraterrestrial life, and we also envision the observed electron-ejection mechanism to find application for exploring solutes at liquid-vapor interfaces.

  9. Glass polymorphism in glycerol-water mixtures: II. Experimental studies.

    PubMed

    Bachler, Johannes; Fuentes-Landete, Violeta; Jahn, David A; Wong, Jessina; Giovambattista, Nicolas; Loerting, Thomas

    2016-04-28

    We report a detailed experimental study of (i) pressure-induced transformations in glycerol-water mixtures at T = 77 K and P = 0-1.8 GPa, and (ii) heating-induced transformations of glycerol-water mixtures recovered at 1 atm and T = 77 K. Our samples are prepared by cooling the solutions at ambient pressure at various cooling rates (100 K s(-1)-10 K h(-1)) and for the whole range of glycerol mole fractions, χ(g). Depending on concentration and cooling rates, cooling leads to samples containing amorphous ice (χg ≥ 0.20), ice (χ(g) ≤ 0.32), and/or "distorted ice" (0 < χ(g) ≤ 0.38). Upon compression, we find that (a) fully vitrified samples at χ(g) ≥ 0.20 do not show glass polymorphism, in agreement with previous works; (b) samples containing ice show pressure-induced amorphization (PIA) leading to the formation of high-density amorphous ice (HDA). PIA of ice domains within the glycerol-water mixtures is shown to be possible only up to χ(g) ≈ 0.32 (T = 77 K). This is rather surprising since it has been known that at χ(g) < 0.38, cooling leads to phase-separated samples with ice and maximally freeze-concentrated solution of χ(g) ≈ 0.38. Accordingly, in the range 0.32 < χ(g) < 0.38, we suggest that the water domains freeze into an interfacial ice, i.e., a highly-distorted form of layered ice, which is unable to transform to HDA upon compression. Upon heating samples recovered at 1 atm, we observe a rich phase behavior. Differential scanning calorimetry indicates that only at χ(g) ≤ 0.15, the water domains within the sample exhibit polyamorphism, i.e., the HDA-to-LDA (low-density amorphous ice) transformation. At 0.15 < χ(g) ≤ 0.38, samples contain ice, interfacial ice, and/or HDA domains. All samples (χ(g) ≤ 0.38) show: the crystallization of amorphous ice domains, followed by the glass transition of the vitrified glycerol-water domains and, finally, the melting of ice at high temperatures. Our work exemplifies the complex "phase" behavior

  10. Glass polymorphism in glycerol–water mixtures: II. Experimental studies

    PubMed Central

    Bachler, Johannes; Fuentes-Landete, Violeta; Jahn, David A.; Wong, Jessina; Giovambattista, Nicolas

    2016-01-01

    We report a detailed experimental study of (i) pressure-induced transformations in glycerol–water mixtures at T = 77 K and P = 0–1.8 GPa, and (ii) heating-induced transformations of glycerol–water mixtures recovered at 1 atm and T = 77 K. Our samples are prepared by cooling the solutions at ambient pressure at various cooling rates (100 K s–1–10 K h–1) and for the whole range of glycerol mole fractions, χ g. Depending on concentration and cooling rates, cooling leads to samples containing amorphous ice (χ g ≥ 0.20), ice (χ g ≤ 0.32), and/or “distorted ice” (0 < χ g ≤ 0.38). Upon compression, we find that (a) fully vitrified samples at χ g ≥ 0.20 do not show glass polymorphism, in agreement with previous works; (b) samples containing ice show pressure-induced amorphization (PIA) leading to the formation of high-density amorphous ice (HDA). PIA of ice domains within the glycerol–water mixtures is shown to be possible only up to χ g ≈ 0.32 (T = 77 K). This is rather surprising since it has been known that at χ g < 0.38, cooling leads to phase-separated samples with ice and maximally freeze-concentrated solution of χ g ≈ 0.38. Accordingly, in the range 0.32 < χ g < 0.38, we suggest that the water domains freeze into an interfacial ice, i.e., a highly-distorted form of layered ice, which is unable to transform to HDA upon compression. Upon heating samples recovered at 1 atm, we observe a rich phase behavior. Differential scanning calorimetry indicates that only at χ g ≤ 0.15, the water domains within the sample exhibit polyamorphism, i.e., the HDA-to-LDA (low-density amorphous ice) transformation. At 0.15 < χ g ≤ 0.38, samples contain ice, interfacial ice, and/or HDA domains. All samples (χ g ≤ 0.38) show: the crystallization of amorphous ice domains, followed by the glass transition of the vitrified glycerol–water domains and, finally, the melting of ice at high temperatures. Our work exemplifies the complex

  11. Liquid-liquid transition without macroscopic phase separation in a water-glycerol mixture

    NASA Astrophysics Data System (ADS)

    Murata, Ken-Ichiro; Tanaka, Hajime

    2012-05-01

    The existence of more than two liquid states in a single-component substance and the ensuing liquid-liquid transitions (LLTs) has attracted considerable attention because of its counterintuitive nature and its importance in the fundamental understanding of the liquid state. Here we report direct experimental evidence for a genuine (isocompositional) LLT without macroscopic phase separation in an aqueous solution of glycerol. We show that liquid I transforms into liquid II by way of two types of kinetics: nucleation and growth, and spinodal decomposition. Although liquid II is metastable against crystallization, we could access both its static and dynamical properties experimentally. We find that liquids I and II differ in density, refractive index, structure, hydrogen bonding state, glass transition temperature and fragility, and that the transition between the two liquids is mainly driven by the local structuring of water rather than of glycerol, suggesting a link to a plausible LLT inpure water.

  12. Air and water stable ionic liquids in physical chemistry.

    PubMed

    Endres, Frank; Zein El Abedin, Sherif

    2006-05-14

    Ionic liquids are defined today as liquids which solely consist of cations and anions and which by definition must have a melting point of 100 degrees C or below. Originating from electrochemistry in AlCl(3) based liquids an enormous progress was made during the recent 10 years to synthesize ionic liquids that can be handled under ambient conditions, and today about 300 ionic liquids are already commercially available. Whereas the main interest is still focussed on organic and technical chemistry, various aspects of physical chemistry in ionic liquids are discussed now in literature. In this review article we give a short overview on physicochemical aspects of ionic liquids, such as physical properties of ionic liquids, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ionic liquids. The focus is set on air and water stable ionic liquids as they will presumably dominate various fields of chemistry in future.

  13. 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.

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

    PubMed

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

    2015-08-14

    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.

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

    SciTech Connect

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

    2015-08-14

    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.

  16. Hydrogen bonding in protic ionic liquids: reminiscent of water.

    PubMed

    Fumino, Koichi; Wulf, Alexander; Ludwig, Ralf

    2009-01-01

    Similarities and differences: Far-infrared spectra of protic ionic liquids could be assigned to intermolecular bending and stretching modes of hydrogen bonds. The characteristics of the low-frequency spectra resemble those of water. Both liquids form three-dimensional network structures, but only water is capable of building tetrahedral configurations. EAN: ethylammonium nitrate, PAN: propylammonium nitrate, DMAN: dimethylammonium nitrate.

  17. The glass-liquid transition of water on hydrophobic surfaces.

    PubMed

    Souda, Ryutaro

    2008-09-28

    Interactions of thin water films with surfaces of graphite and vitrified room-temperature ionic liquid [1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)])] were investigated using time-of-flight secondary ion mass spectrometry as a function of temperature and annealing time to elucidate the glass-liquid transition of water at the molecular level. Surface diffusion of water occurs at temperatures higher than 120 K, thereby forming three-dimensional clusters (a two-dimensional layer) on the [bmim][PF(6)] (graphite) surface. The hydrophobic effect of the surface decreases with increasing coverage of water; the bulklike properties evolve up to 40 ML, as evidenced by the occurrence of film dewetting at around the conventional glass transition temperature (140 K). Results also showed that aging is necessary for the water monolayer (a 40 ML water film) to dewet the graphite ([bmim][PF(6)]) surface. The occurrence of aging is explainable by the successive evolution of two distinct liquids during the glass-liquid transition: low density liquid is followed by supercooled liquid water. The water monolayer on graphite is characterized by the preferred orientation of unpaired OH groups toward the surface; this structure is arrested during the aging time despite the occurrence of surface diffusion. However, the water monolayer formed on the [bmim][PF(6)] surface agglomerates immediately after the commencement of surface diffusion. The structure of low density liquid tends to be arrested by the attractive interaction with the neighbors.

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

    NASA Astrophysics Data System (ADS)

    Kumar, V. Rakesh; Kiran, P. Prem

    2017-01-01

    Water dominantly present in liquid state on earth gets transformed to crystalline polymorphs under different dynamic loading conditions. Out of different crystalline phases discovered till date, ice VII is observed to be stable over wide pressure (2-63 GPa) and temperature (>273 K) ranges. The formation of ice VII crystalline structure has been vastly reported during high pressure static compression using diamond anvil cell and propagation of high energy (>50 mJ/pulse) nanosecond laser pulse induced dynamic high pressures through liquid water. 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 μm area of cross-section.

  19. Liquid-liquid equilibria of water + methanol + 1-octanol and water + ethanol + 1-octanol at various temperatures

    SciTech Connect

    Arce, A.; Blanco, A.; Souza, P.; Vidal, I. . Dept. of Chemical Engineering)

    1994-04-01

    This study is part of a wider program of research on the recovery of light alcohols from dilute aqueous solutions using high molecular weight solvents. The authors report liquid-liquid equilibrium data and binodal curves for the systems water + methanol + 1-octanol and water + ethanol + 1-octanol at 25, 35, and 45 C. The data were fitted to the NRTL and UNIQUAC equations.

  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

  1. Observed reflectivities and liquid water content for marine stratocumulus

    NASA Technical Reports Server (NTRS)

    Coakley, J. A., Jr.; Snider, J. B.

    1989-01-01

    Simultaneous observations of cloud liquid water content and cloud reflectivity are used to verify their parametric relationship in a manner consistent with simple parameterizations often used in general-circulation climate models. The column amount of cloud liquid water was measured with a microwave radiometer on San Nicolas Island as described by Hogg et al., (1983). Cloud reflectivity was obtained through spatial coherence analysis of AVHRR imagery data as per Coakley and Baldwin (1984) and Coakley and Beckner (1988). The dependence of the observed reflectivity on the observed liquid water is discussed, and this empirical relationship is compared with the parameterization proposed by Stephens (1978).

  2. 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.

  3. 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

  4. Isothermal vapor-liquid equilibria for methanol + ethanol + water, methanol + water, and ethanol + water

    SciTech Connect

    Kurihara, Kiyofumi; Takeda, Kouichi; Kojima, Kazuo; Minoura, Tsuyoshi

    1995-05-01

    Isothermal vapor-liquid equilibria were measured for the ternary system methanol + ethanol + water and its constituent binary systems of methanol + water and ethanol + water at 323.15, 328.15, and 333.15 K. The apparatus that was used made it possible to control the measured temperature and total pressure by computer. The experimental binary data were correlated by the NRTL equation. The ternary system was predicted using the binary NRTL parameters with good accuracy.

  5. Polymorphous crystals from chlorozincate-choline chloride ionic liquids in different molar ratios

    NASA Astrophysics Data System (ADS)

    Liu, Yaodong; Wu, Guozhong; Qi, Mingying

    2005-08-01

    Polymorphous crystals of chlorozincate-choline chloride ionic liquid (IL) in different molar ratios were incubated at 5 °C and characterized by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and optical microscope (OM). It is clearly shown that the properties of IL crystal change significantly with X(ZnCl 2) (mole fraction of ZnCl 2) over the range from 0.67 to 0.40. Crystal ( a) (m.p. 45 °C) is formed at X(ZnCl 2)=0.67, both crystal ( a) and crystal ( b) (m.p. 85 °C) are observed at X(ZnCl)=0.50. However, crystal ( c) (m.p. 27 °C) and non-coordinated choline chloride are observed at X(ZnCl 2)=0.40. Morphology of the IL crystal also changes greatly with the X(ZnCl 2). This investigation reveals that structures and properties of the IL anions vary with the X(ZnCl 2) and the molar ratio is a pivotal factor dominating the IL property.

  6. 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.

  7. Liquid-liquid transition in supercooled water suggested by microsecond simulations.

    PubMed

    Li, Yaping; Li, Jicun; Wang, Feng

    2013-07-23

    The putative liquid-liquid phase transition in supercooled water has been used to explain many anomalous behaviors of water. However, no direct experimental verification of such a phase transition has been accomplished, and theoretical studies from different simulations contradict each other. We investigated the putative liquid-liquid phase transition using the Water potential from Adaptive Force Matching for Ice and Liquid (WAIL). The simulation reveals a first-order phase transition in the supercooled regime with the critical point at ~207 K and 50 MPa. Normal water is high-density liquid (HDL). Low-density liquid (LDL) emerges at lower temperatures. The LDL phase has a density only slightly larger than that of the ice-Ih and shows more long-range order than HDL. However, the transformation from LDL to HDL is spontaneous across the first-order phase transition line, suggesting the LDL configuration is not poorly formed nanocrystalline ice. It has been demonstrated in the past that the WAIL potential provides reliable predictions of water properties such as melting temperature and temperature of maximum density. Compared with other simple water potentials, WAIL is not biased by fitting to experimental properties, and simulation with this potential reflects the prediction of a high-quality first-principle potential energy surface.

  8. Liquid water in the domain of cubic crystalline ice Ic

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Banham, S. F.; Blake, D. F.; McCoustra, M. R.

    1997-01-01

    Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

  9. Liquid water in the domain of cubic crystalline ice Ic.

    PubMed

    Jenniskens, P; Banham, S F; Blake, D F; McCoustra, M R

    1997-07-22

    Vapor-deposited amorphous water ice when warmed above the glass transition temperature (120-140 K), is a viscous liquid which exhibits a viscosity vs temperature relationship different from that of liquid water at room temperature. New studies of thin water ice films now demonstrate that viscous liquid water persists in the temperature range 140-210 K. where it coexists with cubic crystalline ice. The liquid character of amorphous water above the glass transition is demonstrated by (1) changes in the morphology of water ice films on a nonwetting surface observed in transmission electron microscopy (TEM) at around 175 K during slow warming, (2) changes in the binding energy of water molecules measured in temperature programmed desorption (TPD) studies, and (3) changes in the shape of the 3.07 micrometers absorption band observed in grazing angle reflection-absorption infrared spectroscopy (RAIRS) during annealing at high temperature. whereby the decreased roughness of the water surface is thought to cause changes in the selection rules for the excitation of O-H stretch vibrations. Because it is present over such a wide range of temperatures, we propose that this form of liquid water is a common material in nature. where it is expected to exist in the subsurface layers of comets and on the surfaces of some planets and satellites.

  10. 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

  11. 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)…

  12. Process for blending coal with water immiscible liquid

    DOEpatents

    Heavin, Leonard J.; King, Edward E.; Milliron, Dennis L.

    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.

  13. 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.

  14. Cluster Monte Carlo and numerical mean field analysis for the water liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Mazza, Marco G.; Stokely, Kevin; Strekalova, Elena G.; Stanley, H. Eugene; Franzese, Giancarlo

    2009-04-01

    Using Wolff's cluster Monte Carlo simulations and numerical minimization within a mean field approach, we study the low temperature phase diagram of water, adopting a cell model that reproduces the known properties of water in its fluid phases. Both methods allow us to study the thermodynamic behavior of water at temperatures, where other numerical approaches - both Monte Carlo and molecular dynamics - are seriously hampered by the large increase of the correlation times. The cluster algorithm also allows us to emphasize that the liquid-liquid phase transition corresponds to the percolation transition of tetrahedrally ordered water molecules.

  15. 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.

  16. Review: Drinking water for liquid-fed pigs.

    PubMed

    Meunier-Salaün, M-C; Chiron, J; Etore, F; Fabre, A; Laval, A; Pol, F; Prunier, A; Ramonet, Y; Nielsen, B L

    2016-11-07

    Liquid feeding has the potential to provide pigs with sufficient water to remain hydrated and prevent prolonged thirst. However, lack of permanent access to fresh water prevents animals from drinking when they are thirsty. Moreover, individual differences between pigs in a pen may result in uneven distribution of the water provided by the liquid feed, leading to some pigs being unable to meet their water requirements. In this review, we look at the need for and provision of water for liquid-fed pigs in terms of their production performance, behaviour, health and welfare. We highlight factors which may lead to water ingestion above or below requirements. Increases in the need for water may be caused by numerous factors such as morbidity, ambient temperature or competition within the social group, emphasising the necessity of permanent access to water as also prescribed in EU legislation. The drinkers can be the target of redirected behaviour in response to feed restriction or in the absence of rooting materials, thereby generating water losses. The method of water provision and drinker design is critical to ensure easy access to water regardless of the pig's physiological state, and to limit the amount of water used, which does not benefit the pig.

  17. Water percolation governs polymorphic transitions and conductivity of DNA.

    PubMed

    Brovchenko, Ivan; Krukau, Aliaksei; Oleinikova, Alla; Mazur, Alexey K

    2006-09-29

    We report on the first computer simulation studies of the percolation transition of water at the surface of the DNA double helix. With increased hydration, the ensemble of small clusters merges into a spanning water network via a quasi-two-dimensional percolation transition. This transition occurs strikingly close to the hydration level where the B form of DNA becomes stable in experiment. Formation of spanning water networks results in sigmoidlike acceleration of long-range ion transport in good agreement with experiment.

  18. 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 μm area of cross-section. The work is supported by Defence Research and Developement Organization, India through Grants-in-Aid Program.

  19. 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.

  20. Identification of Cryptosporidium spp. Oocysts in United Kingdom Noncarbonated Natural Mineral Waters and Drinking Waters by Using a Modified Nested PCR-Restriction Fragment Length Polymorphism Assay

    PubMed Central

    Nichols, R. A. B.; Campbell, B. M.; Smith, H. V.

    2003-01-01

    We describe a nested PCR-restriction fragment length polymorphism (RFLP) method for detecting low densities of Cryptosporidium spp. oocysts in natural mineral waters and drinking waters. Oocysts were recovered from seeded 1-liter volumes of mineral water by filtration through polycarbonate membranes and from drinking waters by filtration, immunomagnetizable separation, and filter entrapment, followed by direct extraction of DNA. The DNA was released from polycarbonate filter-entrapped oocysts by disruption in lysis buffer by using 15 cycles of freeze-thawing (1 min in liquid nitrogen and 1 min at 65°C), followed by proteinase K digestion. Amplicons were readily detected from two to five intact oocysts on ethidium bromide-stained gels. DNA extracted from Cryptosporidium parvum oocysts, C. muris (RN 66), C. baileyi (Belgium strain, LB 19), human-derived C. meleagridis, C. felis (DNA from oocysts isolated from a cat), and C. andersoni was used to demonstrate species identity by PCR-RFLP after simultaneous digestion with the restriction enzymes DraI and VspI. Discrimination between C. andersoni and C. muris isolates was confirmed by a separate, subsequent digestion with DdeI. Of 14 drinking water samples tested, 12 were found to be positive by microscopy, 8 were found to be positive by direct PCR, and 14 were found to be positive by using a nested PCR. The Cryptosporidium species detected in these finished water samples was C. parvum genotype 1. This method consistently and routinely detected >5 oocysts per sample. PMID:12839797

  1. Charge-on-spring polarizable water models revisited: From water clusters to liquid water to ice

    NASA Astrophysics Data System (ADS)

    Yu, Haibo; van Gunsteren, Wilfred F.

    2004-11-01

    The properties of two improved versions of charge-on-spring (COS) polarizable water models (COS/G2 and COS/G3) that explicitly include nonadditive polarization effects are reported. In COS models, the polarization is represented via a self-consistently induced dipole moment consisting of a pair of separated charges. A previous polarizable water model (COS/B2), upon which the improved versions are based, was developed by Yu, Hansson, and van Gunsteren [J. Chem. Phys. 118, 221 (2003)]. To improve the COS/B2 model, which overestimated the dielectric permittivity, one additional virtual atomic site was used to reproduce the water monomer quadrupole moments besides the water monomer dipole moment in the gas phase. The molecular polarizability, residing on the virtual atomic site, and Lennard-Jones parameters for oxygen-oxygen interactions were varied to reproduce the experimental values for the heat of vaporization and the density of liquid water at room temperature and pressure. The improved models were used to study the properties of liquid water at various thermodynamic states as well as gaseous water clusters and ice. Overall, good agreement is obtained between simulated properties and those derived from experiments and ab initio calculations. The COS/G2 and COS/G3 models may serve as simple, classical, rigid, polarizable water models for the study of organic solutes and biopolymers. Due to its simplicity, COS type of polarization can straightforwardly be used to introduce explicit polarization into (bio)molecular force fields.

  2. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water

    NASA Astrophysics Data System (ADS)

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-01

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  3. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water.

    PubMed

    Biddle, John W; Holten, Vincent; Anisimov, Mikhail A

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  4. Dependence of marine stratocumulus reflectivities on liquid water paths

    NASA Technical Reports Server (NTRS)

    Coakley, James A., Jr.; Snider, Jack B.

    1990-01-01

    Simple parameterizations that relate cloud liquid water content to cloud reflectivity are often used in general circulation climate models to calculate the effect of clouds in the earth's energy budget. Such parameterizations have been developed by Stephens (1978) and by Slingo and Schrecker (1982) and others. Here researchers seek to verify the parametric relationship through the use of simultaneous observations of cloud liquid water content and cloud reflectivity. The column amount of cloud liquid was measured using a microwave radiometer on San Nicolas Island following techniques described by Hogg et al., (1983). Cloud reflectivity was obtained through spatial coherence analysis of Advanced Very High Resolution Radiometer (AVHRR) imagery data (Coakley and Beckner, 1988). They present the dependence of the observed reflectivity on the observed liquid water path. They also compare this empirical relationship with that proposed by Stephens (1978). Researchers found that by taking clouds to be isotropic reflectors, the observed reflectivities and observed column amounts of cloud liquid water are related in a manner that is consistent with simple parameterizations often used in general circulation climate models to determine the effect of clouds on the earth's radiation budget. Attempts to use the results of radiative transfer calculations to correct for the anisotropy of the AVHRR derived reflectivities resulted in a greater scatter of the points about the relationship expected between liquid water path and reflectivity. The anisotropy of the observed reflectivities proved to be small, much smaller than indicated by theory. To critically assess parameterizations, more simultaneous observations of cloud liquid water and cloud reflectivities and better calibration of the AVHRR sensors are needed.

  5. Experimental Evidence for a Liquid-Liquid Crossover in Deeply Cooled Confined Water

    NASA Astrophysics Data System (ADS)

    Cupane, Antonio; Fomina, Margarita; Piazza, Irina; Peters, Judith; Schirò, Giorgio

    2014-11-01

    In this work we investigate, by means of elastic neutron scattering, the pressure dependence of mean square displacements (MSD) of hydrogen atoms of deeply cooled water confined in the pores of a three-dimensional disordered SiO2 xerogel; experiments have been performed at 250 and 210 K from atmospheric pressure to 1200 bar. The "pressure anomaly" of supercooled water (i.e., a mean square displacement increase with increasing pressure) is observed in our sample at both temperatures; however, contrary to previous simulation results and to the experimental trend observed in bulk water, the pressure effect is smaller at lower (210 K) than at higher (250 K) temperature. Elastic neutron scattering results are complemented by differential scanning calorimetry data that put in evidence, besides the glass transition at about 170 K, a first-order-like endothermic transition occurring at about 230 K that, in view of the neutron scattering results, can be attributed to a liquid-liquid crossover. Our results give experimental evidence for the presence, in deeply cooled confined water, of a crossover occurring at about 230 K (at ambient pressure) from a liquid phase predominant at 210 K to another liquid phase predominant at 250 K; therefore, they are fully consistent with the liquid-liquid transition hypothesis.

  6. 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.

  7. The puzzling unsolved mysteries of liquid water: Some recent progress

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Water is perhaps the most ubiquitous, and the most essential, of any molecule on earth. Indeed, it defies the imagination of even the most creative science fiction writer to picture what life would be like without water. Despite decades of research, however, water's puzzling properties are not understood and 63 anomalies that distinguish water from other liquids remain unsolved. We introduce some of these unsolved mysteries, and demonstrate recent progress in solving them. We present evidence from experiments and computer simulations supporting the hypothesis that water displays a special transition point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell). The general idea is that when the liquid is near this “tipping point,” it suddenly separates into two distinct liquid phases. This concept of a new critical point is finding application to other liquids as well as water, such as silicon and silica. We also discuss related puzzles, such as the mysterious behavior of water near a protein.

  8. A new water-based liquid scintillator and potential applications

    NASA Astrophysics Data System (ADS)

    Yeh, M.; Hans, S.; Beriguete, W.; Rosero, R.; Hu, L.; Hahn, R. L.; Diwan, M. V.; Jaffe, D. E.; Kettell, S. H.; Littenberg, L.

    2011-12-01

    In this paper we describe a new type of scintillating liquid based on water. We describe the concept, preparation, and properties of this liquid, and how it could be used for a very large, but economical detector. The applications of such a detector range from fundamental physics such as nucleon decay and neutrino physics to physics with broader application such as neutron detection. We briefly describe the scientific requirements of these applications, and how they can be satisfied by the new material.

  9. Solid−liquid critical behavior of water in nanopores

    PubMed Central

    Mochizuki, Kenji; Koga, Kenichiro

    2015-01-01

    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

  10. On the Stability of Liquid Water on Present Day Mars

    NASA Technical Reports Server (NTRS)

    Haberle, Robert M.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The mean annual surface pressure and temperature on present day Mars do not allow for the long term stability of liquid water on the surface. However, theoretical arguments have been advanced that suggest liquid water could form in transient events even though it would not be in equilibrium with the environment. Using a Mars General Circulation Model, we calculate where and for how long the surface pressure and surface temperature meet the minimum requirements for this metastability of liquid water. These requirements are that the pressure and temperature must be above the triple point of water, but below its boiling point. We find that there are five regions on Mars where these requirements are periodically satisfied: in the near equatorial regions of Amazonis, Arabia, and Elysium, and in the Hellas and Argyre impact basins. Whether liquid water ever forms in these regions depends on the availability of ice and heat, and on the evaporation rate. The latter is poorly understood for low pressure CO2 environments, but is likely to be so high that melting occurs rarely, if at all. However, in the relatively recent past, surface pressures may have been higher than they are today perhaps by as much as a factor of 2 or 3. Under these circumstances melting would have been easier to achieve. We plan to undertake laboratory experiments to better understand the potential for melting in low pressure environments.

  11. On the Fluctuations that Order and Frustrate Liquid Water

    NASA Astrophysics Data System (ADS)

    Limmer, David Tyler

    At ambient conditions, water sits close to phase coexistence with its crystal. More so than in many other materials, this fact is manifested in the fluctuations that maintain a large degree of local order in the liquid. These fluctuations and how they result in long-ranged order, or its absence, are emergent features of many interacting molecules. Their study therefore requires using the tools of statistical mechanics for their their systematic understanding. In this dissertation we develop such an understanding. In particular, we focus on collective behavior that emerges in liquid and solid water. At room temperatures, the thermophysical properties of water are quantified and rationalized with simple molecular models. A key feature of these models is the correct characterization of the competition between entropic forces of packing and the energetic preference for tetrahedral order. At cold temperatures, the properties of ice surfaces are studied with statistical field theory. The theory we develop for the long wavelength features of ice interfaces allows us to explain the existence of a premelting layer on the surface of ice and the stability of ice in confinement. In between these extremes, the dynamics of supercooled water are considered. A detailed theory for the early stages of coarsening is developed and used to explain the peculiar observation of a transient second liquid state of water. When coarsening dynamics are arrested, the result is the formation of a glassy states of water. We show that out-of-equilibrium the phase diagram for supercooled water exhibits a rich amount of structure, including a triple point between two glass phases of water and the liquid. At the end, we explore possible technological implications for the interplay between ordering and frustration in studies of water at metal interfaces.

  12. Development of a dispersive liquid-liquid microextraction method using a lighter-than-water ionic liquid for the analysis of polycyclic aromatic hydrocarbons in water.

    PubMed

    Medina, Giselle S; Reta, Mario

    2016-11-01

    A dispersive liquid-liquid microextraction method using a lighter-than-water phosphonium-based ionic liquid for the extraction of 16 polycyclic aromatic hydrocarbons from water samples has been developed. The extracted compounds were analyzed by liquid chromatography coupled to fluorescence/diode array detectors. The effects of several experimental parameters on the extraction efficiency, such as type and volume of ionic liquid and disperser solvent, type and concentration of salt in the aqueous phase and extraction time, were investigated and optimized. Three phosphonium-based ionic liquids were assayed, obtaining larger extraction efficiencies when trihexyl-(tetradecyl)phosphonium bromide was used. The optimized methodology requires a few microliters of a lighter-than-water phosphonium-based ionic liquid, which allows an easy separation of the extraction solvent phase. The obtained limits of detection were between 0.02 and 0.56 μg/L, enrichment factors between 109 and 228, recoveries between 60 and 108%, trueness between 0.4 and 9.9% and reproducibility values between 3 and 12% were obtained. These figures of merit combined with the simplicity, rapidity and low cost of the analytical methodology indicate that this is a viable and convenient alternative to the methods reported in the literature. The developed method was used to analyze polycyclic aromatic hydrocarbons in river water samples.

  13. Economics of liquid hydrogen from water electrolysis

    NASA Technical Reports Server (NTRS)

    Lin, F. N.; Moore, W. I.; Walker, S. W.

    1985-01-01

    An economical model for preliminary analysis of LH2 cost from water electrolysis is presented. The model is based on data from vendors and open literature, and is suitable for computer analysis of different scenarios for 'directional' purposes. Cost data associated with a production rate of 10,886 kg/day are presented. With minimum modification, the model can also be used to predict LH2 cost from any electrolyzer once the electrolyzer's cost data are available.

  14. 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.

  15. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    SciTech Connect

    Perahia, Dvora, Dr.; Pierce, Flint; Tsige, Mesfin; Grest, Gary Stephen, Dr.

    2008-08-01

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  16. Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.

    PubMed

    Pierce, Flint; Tsige, Mesfin; Perahia, Dvora; Grest, Gary S

    2008-12-18

    The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

  17. Limiting shear stress and monotonic properties of liquid water

    NASA Astrophysics Data System (ADS)

    Gorshkov, A. I.

    2016-12-01

    Publications in scientific journals in which the authors attempt to experimentally prove that water, the most widespread substance on the Earth, is not a completely classical liquid, have become more frequent recently. This means, first, that water behaves as a solid at very low shear stress, i.e., does not flow, and, second, that the temperature dependences of its different properties are non-monotonic, i.e., possess singularities. We are aware of several such publications [1-5].

  18. Molecular dynamics simulation of liquid water: Hybrid density functionals

    SciTech Connect

    Todorova, T; Seitsonen, A; Hutter, J; Kuo, W; Mundy, C

    2005-09-12

    The structure, dynamical and electronic properties of liquid water utilizing different hybrid density functionals were tested within the plane wave framework of first principles molecular dynamics simulations. The computational approach, which employs modified functionals with short-ranged Hartree-Fock exchange, was first tested in calculations of the structural and bonding properties of the water dimer and cyclic water trimer. Liquid water simulations were performed at the state point of 350 K at the experimental density. Simulations included three different hybrid functionals, a meta functional, four gradient corrected functionals, the local density and Hartree-Fock approximation. It is found that hybrid functionals are superior in reproducing the experimental structure and dynamical properties as measured by the radial distribution function and self diffusion constant when compared to the pure density functionals. The local density and Hartree-Fock approximations show strongly over- and under-structured liquids, respectively. Hydrogen bond analysis shows that the hybrid functionals give slightly smaller averaged numbers of hydrogen bonds and similar hydrogen bond populations as pure density functionals. The average molecular dipole moments in the liquid from the three hybrid functionals are lower than from the corresponding pure density functionals.

  19. 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.

  20. Computer simulation of liquid/liquid interfaces. I. Theory and application to octane/water

    NASA Astrophysics Data System (ADS)

    Zhang, Yuhong; Feller, Scott E.; Brooks, Bernard R.; Pastor, Richard W.

    1995-12-01

    Statistical ensembles for simulating liquid interfaces at constant pressure and/or surface tension are examined, and equations of motion for molecular dynamics are obtained by various extensions of the Andersen extended system approach. Valid ensembles include: constant normal pressure and surface area; constant tangential pressure and length normal to the interface; constant volume and surface tension; and constant normal pressure and surface tension. Simulations at 293 K and 1 atm normal pressure show consistent results with each other and with a simulation carried out at constant volume and energy. Calculated surface tensions for octane/water (61.5 dyn/cm), octane/vacuum (20.4 dyn/cm) and water/vacuum (70.2 dyn/cm) are in very good agreement with experiment (51.6, 21.7, and 72.8 dyn/cm, respectively). The practical consequences of simulating with two other approaches commonly used for isotropic systems are demonstrated on octane/water: applying equal normal and tangential pressures leads to an instability; and applying a constant isotropic pressure of 1 atm leads to a large positive normal pressure. Both results are expected for a system of nonzero surface tension. Mass density and water polarization profiles in the liquid/liquid and liquid/vapor interfaces are also compared.

  1. Boson peak, Ioffe-Regel Crossover, and Liquid-Liquid phase transition in Supercooled Water

    NASA Astrophysics Data System (ADS)

    Kumar, Pradeep

    We have investigated the onset of Boson peak in a model of liquid water which exhibits a clear first-order phase transition between a low-density liquid phase and a high-density liquid phase of water at low temperature and high pressure. We find that the at low pressures, the onset of Boson peak coincides with the Widom-line of the system. At high pressures, the onset occurs at the transition temperature between the two liquids. Furthermore, we show that at both low and high pressure, the frequency of the Boson peak coincides with the Ioffe-Regel crossover of the transverse phonons, suggesting that the breakdown of Debye behavior is a general feature of Ioffe-Regel limit crossover in supercooled water. The frequency of the Boson peak is weakly pressure dependent and decreases with increasing pressure. Our work bridges gap between the experimental results on the Boson peak nanoconfined water and the behavior that one would expect from a bulk system.

  2. Switchable water: microfluidic investigation of liquid-liquid phase separation mediated by carbon dioxide.

    PubMed

    Lestari, Gabriella; Abolhasani, Milad; Bennett, Darla; Chase, Preston; Günther, Axel; Kumacheva, Eugenia

    2014-08-27

    Increase in the ionic strength of water that is mediated by the reaction of carbon dioxide (CO2) with nitrogenous bases is a promising approach toward phase separation in mixtures of water with organic solvents and potentially water purification. Conventional macroscale studies of this complicated process are challenging, due to its occurrence via several consecutive and concurrent steps, mass transfer limitation, and lack of control over gas-liquid interfaces. We report a new microfluidic strategy for fundamental studies of liquid-liquid phase separation mediated by CO2 as well as screening of the efficiency of nitrogenous agents. A single set of microfluidic experiments provided qualitative and quantitative information on the kinetics and completeness of water-tetrahydrofuran phase separation, the minimum amount of CO2 required to complete phase separation, the total CO2 uptake, and the rate of CO2 consumption by the liquid mixture. The efficiency of tertiary diamines with different lengths of alkyl chain was examined in a time- and labor-efficient manner and characterized with the proposed efficiency parameter. A wealth of information obtained using the MF methodology can facilitate the development of new additives for switchable solvents in green chemistry applications.

  3. Ionic liquid-based dispersive liquid-liquid microextraction for sensitive determination of aromatic amines in environmental water.

    PubMed

    Han, Dandan; Yan, Hongyuan; Row, Kyung H

    2011-05-01

    Ionic liquid-based dispersive liquid-liquid microextraction was developed for the extraction and preconcentration of aromatic amine from environmental water. A suitable mixture of extraction solvent (100 μL, 1-butyl-3-methylimidazolium hexafluorophoshate) and dispersive solvent (750 μL, methanol) were injected into the aqueous samples (10.00 mL), forming a cloudy solution. After centrifuging, enriched analytes in the sediment phase were determined by HPLC-UV. The effect of various factors, such as the extraction and dispersive solvent, sample pH, extraction time and salt effect were investigated. Under optimum conditions, enrichment factors for 2-anilinoethanol, o-chloroaniline and 4-bromo-N,N-dimethylaniline were above 50 and the limits of detection (LODs) were 0.023, 0.015 and 0.026 ng/mL, respectively. Their linear ranges were 0.8-400 ng/mL for 2-anilinoethanol, 0.5-200 ng/mL for o-chloroaniline and 0.4-200 ng/mL for 4-bromo-N,N-dimethylaniline, respectively. Relative standard deviations (RSDs) were below 5.0%. The relative recoveries from samples of environmental water were in the range of 82.0-94.0%. Compared with other methods, dispersive liquid-liquid microextraction is simple, rapid, sensitive and economical.

  4. Complete wetting of Pt(111) by nanoscale liquid water films

    SciTech Connect

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Kay, Bruce D.; Kimmel, Gregory A.

    2016-02-04

    The melting and wetting of nanoscale crystalline ice films on Pt(111) that are transiently heated above the melting point using nanosecond laser pulses are studied with infrared refection absorption spectroscopy (IRAS) and Kr temperature programmed desorption (TPD). The as-grown crystalline ice films consist of isolated nanoscale ice crystallites embedded in a hydrophobic water monolayer. Upon heating above the melting point, these ice crystallites rapidly melt to form nanoscale droplets of liquid water. Rapid cooling of the system to cryogenic temperatures after each laser pulse quenches the water films and allows them to be interrogated with IRAS, Kr TPD and other ultrahigh vacuum surface science techniques. With each successive heat pulse, these liquid drops spread across the surface until it is entirely covered with multilayer water films after several pulses. These results, which show that nanoscale water films completely wet Pt(111), are in contrast to molecular dynamics simulations predicting partial wetting of nanoscale water drops on a hydrophobic water monolayer. The results provide valuable new insights into the wetting characteristics of nanoscale water films on a clean, well-characterized single crystal surface.

  5. Three-dimensional picture of dynamical structure in liquid water

    NASA Astrophysics Data System (ADS)

    Svishchev, Igor M.; Zassetsky, Alexander Yu.

    2000-01-01

    This paper presents a methodology with which to study the local density distributions in molecular liquids and their fluctuations in any spatial direction. The distinct part of the van Hove density-density correlation function for liquid water is calculated in molecular dynamics simulations. Because of the pronounced nonspherical intermolecular interactions this pair-density function is direction dependent in the local molecular frame. We explicitly resolve the distinct van Hove function in the local frame of water molecules. The dynamics of the tetrahedrally coordinated (hydrogen bonded) and the interstitial molecules in liquid water are examined. The spectrum of the pair-density fluctuations for the tetrahedrally coordinated molecules in supercooled and ambient water exhibits a well-known translational mode at 200 cm-1 and a collective relaxation mode at lower frequencies, at approximately 10 cm-1 at 263 K. The correlation time of this relaxation process decreases with temperature, from 2.2 ps at 238 K to 1.4 ps at 298 K. The spectrum for the interstitial coordination also features a 10 cm-1 mode. It represents a secondary relaxation process in water different from a much slower Debye process. As temperature increases this relaxation mode tends to disappear from the pair-density fluctuations.

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

    DOE PAGES

    Bignell, L. J.; Diwan, M. V.; Hans, S.; ...

    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

  7. 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.

  8. Numerical studies on the separation performance of liquid- liquid Hydrocyclone for higher water-cut wells

    NASA Astrophysics Data System (ADS)

    Osei, H.; Al-Kayiem, H. H.; Hashim, F. M.

    2015-12-01

    Liquid-liquid hydrocyclones have nowadays become very useful in the oil industry because of their numerous applications. They can be installed downhole in the case of a well that produces higher water-oil ratios. The design of a liquid-liquid hydrocyclone for such a task is critical and every geometric part of the hydrocyclone has a part to play as far as separation is concerned. This work, through validated numerical technique, investigated the liquid-liquid hydrocyclone performance for the cases of single-inlet and dual-inlets, with different upper cylindrical lengths, specifically, 30mm and 60mm.It was observed that the hydrocyclones with the 30mm upper cylindrical section perform better than the ones with 60 mm upper cylindrical section. It was again noted that, even though higher number of tangential inlets increases the swirl intensity, they have the tendency to break up the oil droplets within the hydrocyclone because of increasing shear and jet flow interaction.

  9. Study of the ST2 model of water close to the liquid-liquid critical point.

    PubMed

    Sciortino, Francesco; Saika-Voivod, Ivan; Poole, Peter H

    2011-11-28

    We perform successive umbrella sampling grand canonical Monte Carlo computer simulations of the original ST2 model of water in the vicinity of the proposed liquid-liquid critical point, at temperatures above and below the critical temperature. Our results support the previous work of Y. Liu, A. Z. Panagiotopoulos and P. G. Debenedetti [J. Chem. Phys., 2009, 131, 104508], who provided evidence for the existence and location of the critical point for ST2 using the Ewald method to evaluate the long-range forces. Our results therefore demonstrate the robustness of the evidence for critical behavior with respect to the treatment of the electrostatic interactions. In addition, we verify that the liquid is equilibrated at all densities on the Monte Carlo time scale of our simulations, and also that there is no indication of crystal formation during our runs. These findings demonstrate that the processes of liquid-state relaxation and crystal nucleation are well separated in time. Therefore, the bimodal shape of the density of states, and hence the critical point itself, is a purely liquid-state phenomenon that is distinct from the crystal-liquid transition.

  10. 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

  11. Electronic Excitation Dynamics in Liquid Water under Proton Irradiation

    PubMed Central

    Reeves, Kyle G.; Kanai, Yosuke

    2017-01-01

    Molecular behaviour of liquid water under proton irradiation is of great importance to a number of technological and medical applications. The highly energetic proton generates a time-varying field that is highly localized and heterogeneous at the molecular scale, and massive electronic excitations are produced as a result of the field-matter interaction. Using first-principles quantum dynamics simulations, we reveal details of how electrons are dynamically excited through non-equilibrium energy transfer from highly energetic protons in liquid water on the atto/femto-second time scale. Water molecules along the path of the energetic proton undergo ionization at individual molecular level, and the excitation primarily derives from lone pair electrons on the oxygen atom of water molecules. A reduced charge state on the energetic proton in the condensed phase of water results in the strongly suppressed electronic response when compared to water molecules in the gas phase. These molecular-level findings provide important insights into understanding the water radiolysis process under proton irradiation. PMID:28084420

  12. Electronic Excitation Dynamics in Liquid Water under Proton Irradiation

    NASA Astrophysics Data System (ADS)

    Reeves, Kyle G.; Kanai, Yosuke

    2017-01-01

    Molecular behaviour of liquid water under proton irradiation is of great importance to a number of technological and medical applications. The highly energetic proton generates a time-varying field that is highly localized and heterogeneous at the molecular scale, and massive electronic excitations are produced as a result of the field-matter interaction. Using first-principles quantum dynamics simulations, we reveal details of how electrons are dynamically excited through non-equilibrium energy transfer from highly energetic protons in liquid water on the atto/femto-second time scale. Water molecules along the path of the energetic proton undergo ionization at individual molecular level, and the excitation primarily derives from lone pair electrons on the oxygen atom of water molecules. A reduced charge state on the energetic proton in the condensed phase of water results in the strongly suppressed electronic response when compared to water molecules in the gas phase. These molecular-level findings provide important insights into understanding the water radiolysis process under proton irradiation.

  13. A single-site multipole model for liquid water

    NASA Astrophysics Data System (ADS)

    Tran, Kelly N.; Tan, Ming-Liang; Ichiye, Toshiko

    2016-07-01

    Accurate and efficient empirical potential energy models that describe the atomistic interactions between water molecules in the liquid phase are essential for computer simulations of many problems in physics, chemistry, and biology, especially when long length or time scales are important. However, while models with non-polarizable partial charges at four or five sites in a water molecule give remarkably good values for certain properties, deficiencies have been noted in other properties and increasing the number of sites decreases computational efficiency. An alternate approach is to utilize a multipole expansion of the electrostatic potential due to the molecular charge distribution, which is exact outside the charge distribution in the limits of infinite distances or infinite orders of multipoles while partial charges are a qualitative representation of electron density as point charges. Here, a single-site multipole model of water is presented, which is as fast computationally as three-site models but is also more accurate than four- and five-site models. The dipole, quadrupole, and octupole moments are from quantum mechanical-molecular mechanical calculations so that they account for the average polarization in the liquid phase, and represent both the in-plane and out-of-plane electrostatic potentials of a water molecule in the liquid phase. This model gives accurate thermodynamic, dynamic, and dielectric properties at 298 K and 1 atm, as well as good temperature and pressure dependence of these properties.

  14. 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.

  15. Liquid water confined in carbon nanochannels at high temperatures.

    PubMed

    Nagy, G; Gordillo, M C; Guàrdia, E; Martí, J

    2007-11-01

    Structure, hydrogen bonding, electrostatics, dielectric, and dynamical properties of liquid water confined in flat graphene nanochannels are investigated by molecular dynamics simulations. A wide range of temperatures (between 20 and 360 degrees C) have been considered. Molecular structure suffers substantial changes when the system is heated, with a significant loss of structure and hydrogen bonding. In such case, the interface between adsorbed and bulk-like water has a marked tendency to disappear, and the two preferential orientations of water nearby the graphite layers at room temperature are essentially merging above the boiling point. The general trend for the static dielectric constant is its reduction at high temperature states, as compared to ambient conditions. Similarly, residence times of water molecules in adsorbed and bulk-like regions are significantly influenced by temperature, as well. Finally, we observed relevant changes in water diffusion and spectroscopy along the range of temperatures analyzed.

  16. On the implications of aerosol liquid water and phase ...

    EPA Pesticide Factsheets

    Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to organic carbon (OM ∕ OC) ratios are high such that separation relative humidities (SRH) are below the ambient relative humidity (RH). As OM ∕ OC ratios in the SE US are often between 1.8 and 2.2, organic aerosol experiences both mixing with inorganic water and separation from it. Regional chemical transport model simulations including inorganic water (but excluding water uptake by organic compounds) in the partitioning medium for secondary organic aerosol (SOA) when RH  >  SRH led to increased SOA concentrations, particularly at night. Water uptake to the organic phase resulted in even greater SOA concentrations as a result of a positive feedback in which water uptake increased SOA, which further increased aerosol water and organic aerosol. Aerosol properties, such as the OM ∕ OC and hygroscopicity parameter (κorg), were captured well by the model compared with measurements during the Southern Oxidant and Aerosol Study (SOAS) 2013. Organic nitrates from monoterpene oxidation were predicted to be the least water-soluble semivolatile species in the model, but most biogenically derived semivolatile species in the Community Multiscale Air Quality (CMAQ) model were hig

  17. Hydrogen bonding definitions and dynamics in liquid water.

    PubMed

    Kumar, R; Schmidt, J R; Skinner, J L

    2007-05-28

    X-ray and neutron diffractions, vibrational spectroscopy, and x-ray Raman scattering and absorption experiments on water are often interpreted in terms of hydrogen bonding. To this end a number of geometric definitions of hydrogen bonding in water have been developed. While all definitions of hydrogen bonding are to some extent arbitrary, those involving one distance and one angle for a given water dimer are unnecessarily so. In this paper the authors develop a systematic procedure based on two-dimensional potentials of mean force for defining cutoffs for a given pair of distance and angular coordinates. They also develop an electronic structure-based definition of hydrogen bonding in liquid water, related to the electronic occupancy of the antibonding OH orbitals. This definition turns out to be reasonably compatible with one of the distance-angle geometric definitions. These two definitions lead to an estimate of the number of hydrogen bonds per molecule in liquid simple point charge/extended (SPC/E) water of between 3.2 and 3.4. They also used these and other hydrogen-bond definitions to examine the dynamics of local hydrogen-bond number fluctuations, finding an approximate long-time decay constant for SPC/E water of between 0.8 and 0.9 ps, which corresponds to the time scale for local structural relaxation.

  18. Liquid-liquid critical point in a simple analytical model of water

    NASA Astrophysics Data System (ADS)

    Urbic, Tomaz

    2016-10-01

    A statistical model for a simple three-dimensional Mercedes-Benz model of water was used to study phase diagrams. This model on a simple level describes the thermal and volumetric properties of waterlike molecules. A molecule is presented as a soft sphere with four directions in which hydrogen bonds can be formed. Two neighboring waters can interact through a van der Waals interaction or an orientation-dependent hydrogen-bonding interaction. For pure water, we explored properties such as molar volume, density, heat capacity, thermal expansion coefficient, and isothermal compressibility and found that the volumetric and thermal properties follow the same trends with temperature as in real water and are in good general agreement with Monte Carlo simulations. The model exhibits also two critical points for liquid-gas transition and transition between low-density and high-density fluid. Coexistence curves and a Widom line for the maximum and minimum in thermal expansion coefficient divides the phase space of the model into three parts: in one part we have gas region, in the second a high-density liquid, and the third region contains low-density liquid.

  19. 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.

  20. 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

  1. Liquid-Liquid Phase Equilibria and Interactions between Droplets in Water-in-Oil Microemulsions.

    PubMed

    Yin, Tianxiang; Wang, Mingjie; Tao, Xiaoyi; Shen, Weiguo

    2016-12-20

    The liquid-liquid phase equilibria of [water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane] with the molar ratio w0 of water to AOT being 37.9 and [water/AOT/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/n-decane] with w0 = 37.9 and the mole fraction α of Dynol-604 in the total surfactants being 0.158 were measured in this study. From the data collected in the critical region, the critical exponent β corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value. A thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was proposed to describe the coexistence curves and to deduce the interaction properties between droplets in the microemulsions. The interaction enthalpies were found to be positive for the studied systems, which evidenced that the entropy effect dominated the phase separations as the temperature increased. The addition of Dynol-604 into the (water/AOT/n-decane) microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy. Combining the liquid-liquid equilibrium data for (water/AOT/n-decane) microemulsions with various w0 values determined previously, it was shown that the interaction enthalpy decreased with w0 and tended to change its sign at low w0, which coincided with the results from the isothermal titration calorimetry investigation. All of these behaviors were interpreted by the effects of entropy and enthalpy and their competition, which resulted from the release of solvent molecules entrapped in the interface of microemulsion droplets and were dependent on the rigidity of the surfactant layers and the size of the droplet.

  2. X-Ray Spectroscopy of the Liquid Water Surface

    NASA Astrophysics Data System (ADS)

    Saykally, Richard

    2004-03-01

    We have developed a new experiment for probing molecular details of liquid-vapor interfaces of volatile substances and their solutions under equilibrium conditions. Electronic and geometric structures of interfacial molecules are probed by EXAFS and NEXAFS methods in the soft X-ray region, using the Advanced Light Source, Berkeley, CA. Liquids are introduced into a high vacuum environment through the use of liquid microjets, which have been characterized independently by Raman spectroscopy. Detection of ions and electrons produced by the Auger avalanche probe the bulk and surface regions of the microjet, respectively, as a result of their different escape depths. Our first efforts involved a comparative study of the interfaces of water and methanol, wherein we detailed the first observation of surface relaxation for a liquid. Analysis of EXAFS data yielded a 6distance at the water interface, whereas a 5was found for methanol. NEXAFS measurements, interpreted in terms of density functional theory simulations, indicate a large population of interfacial water molecules having two free OH bonds ("acceptor only molecules"). This complements the "single donor" species identified in sum frequency generation experiments. These results are supported by recent theoretical calculations. For methanol and other simple alcohols, the data indicate that free alkyl groups extend into the vapor part of the interface. Preliminary results for aqueous solutions, as well as for other pure liquids, have been obtained and are presently under analysis. REFERENCES 1. K.R. Wilson, R.D. Schaller, B.S. Rude, T. Catalano, D.T. Co, J.D. Bozek, and R.J. Saykally, "Surface relaxation in liquid water and methanol studied by X-ray absorption spectroscopy," J. Chem. Phys 117,7738(2002). 2. K.R. Wilson, M. Cavalleri, B.S. Rude, R.D. Schaller, A. Nilsson, L.G.M. Pettersson, N. Goldman, T. Catalano, J.D. Bozek, and R.J. Saykally, "Characterization of hydrogen bond acceptor molecules at the water surface

  3. 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

    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.

  4. Ionic-liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography for the determination of multiclass pesticide residues in water samples.

    PubMed

    Tadesse, Bezuayehu; Teju, Endale; Gure, Abera; Megersa, Negussie

    2015-03-01

    Ionic-liquid-based dispersive liquid-liquid microextraction in combination with high-performance liquid chromatography and diode array detection has been proposed for the simultaneous analysis of four multiclass pesticide residues including carbaryl, methidathion, chlorothalonil, and ametryn from water samples. The major experimental parameters including the type and volume of ionic liquid, sample pH, type, and volume of disperser solvent and cooling time were investigated and optimum conditions were established. Under the optimum experimental conditions, limits of detection and quantification of the method were in the range of 0.1-1.8 and 0.4-5.9 μg/L, respectively, with satisfactory enrichment factors ranging from 10-20. The matrix-matched calibration curves, which were constructed for lake water, as a representative matrix were linear over wide range with coefficients of determination of 0.996 or better. Intra- and interday precisions, expressed as relative standard deviations, were in the range of 1.1-9.7 and 3.1-7.8%, respectively. The relative recoveries of the spiked environmental water samples at one concentration level were in the range of 77-102%. The results of the present study revealed that the proposed method is simple, fast, and uses environmentally friendly extraction solvent for the analysis of the target pesticide residues in environmental water samples.

  5. Dispersive liquid-liquid microextraction of silver nanoparticles in water using ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate.

    PubMed

    Chen, Sha; Sun, Yuanjing; Chao, Jingbo; Cheng, Liping; Chen, Yun; Liu, Jingfu

    2016-03-01

    Using the ionic liquid (IL) 1-octyl-3-methylimidazolium hexafluorophosphate as the extractant and methanol as the dispersion solvent, a dispersive liquid-liquid microextraction method was developed to extract silver nanoparticles (AgNPs) from environmental water samples. Parameters that influenced the extraction efficiency such as IL concentration, pH and extraction time were optimized. Under the optimized conditions, the highest extraction efficiency for AgNPs was above 90% with an enrichment factor of >90. The extracted AgNPs in the IL phase were identified by transmission electron microscopy and ultraviolet-visible spectroscopy, and quantified by inductively coupled plasma mass spectrometry after microwave digestion, with a detection limit of 0.01μg/L. The spiked recovery of AgNPs was 84.4% with a relative standard deviation (RSD) of 3.8% (n=6) at a spiked level of 5μg/L, and 89.7% with a RSD of 2.2% (n=6) at a spiked level of 300μg/L, respectively. Commonly existed environmental ions had a very limited influence on the extraction efficiency. The developed method was successfully applied to the analysis of AgNPs in river water, lake water, and the influent and effluent of a wastewater treatment plant, with recoveries in the range of 71.0%-90.9% at spiking levels of 0.11-4.7μg/L.

  6. Optically Thin Liquid Water Clouds: Their Importance and Our Challenge

    NASA Technical Reports Server (NTRS)

    Turner, D. D.; Vogelmann, A. M.; Austin, R. T.; Barnard, J. C.; Cady-Pereira, K.; Chiu, J. C.; Clough, S. A.; Flynn, C.; Khaiyer, M. M.; Liljegren, J.; Johnson, K.; Lin, B.; Long, C.; Marshak, A.; Matrosov, S. Y.; McFarlane, S. A.; Miller, M.; Min, Q.; Minnis, P.; O'Hirok, W.; Wang, Z.; Wiscombe, W.

    2006-01-01

    Many of the clouds important to the Earth's energy balance, from the tropics to the Arctic, are optically thin and contain liquid water. Longwave and shortwave radiative fluxes are very sensitive to small perturbations of the cloud liquid water path (LWP) when the liquid water path is small (i.e., < g/sq m) and, thus, the radiative properties of these clouds must be well understood to capture them correctly in climate models. We review the importance of these thin clouds to the Earth's energy balance, and explain the difficulties in observing them. In particular, because these clouds are optically thin, potentially mixed-phase, and often (i.e., have large 3-D variability), it is challenging to retrieve their microphysical properties accurately. We describe a retrieval algorithm intercomparison that was conducted to evaluate the issues involved. The intercomparison included eighteen different algorithms to evaluate their retrieved LWP, optical depth, and effective radii. Surprisingly, evaluation of the simplest case, a single-layer overcast cloud, revealed that huge discrepancies exist among the various techniques, even among different algorithms that are in the same general classification. This suggests that, despite considerable advances that have occurred in the field, much more work must be done, and we discuss potential avenues for future work.

  7. 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.

  8. 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.

  9. Rapid screening of water soluble arsenic species in edible oils using dispersive liquid-liquid microextraction.

    PubMed

    López-García, Ignacio; Briceño, Marisol; Vicente-Martínez, Yesica; Hernández-Córdoba, Manuel

    2015-01-15

    A methodology for the non-chromatographic screening of the main arsenic species present in edible oils is discussed. Reverse dispersive liquid-liquid microextraction was used to extract water soluble arsenic compounds (inorganic arsenic, methylarsonate, dimethylarsinate and arsenobetaine) from the edible oils into a slightly acidic aqueous medium. The total arsenic content was measured in the extracts by electrothermal atomic absorption spectrometry using palladium as the chemical modifier. By repeating the measurement using cerium instead of palladium, the sum of inorganic arsenic and methylarsonate was obtained. The detection limit was 0.03 ng As per gram of oil. Data for the total and water-soluble arsenic levels of 29 samples of different origin are presented. Inorganic arsenic was not found in any of the samples marketed as edible oils.

  10. Liquid water can slip on a hydrophilic surface

    PubMed Central

    Ho, Tuan Anh; Papavassiliou, Dimitrios V.; Lee, Lloyd L.; Striolo, Alberto

    2011-01-01

    Understanding and predicting the behavior of water, especially in contact with various surfaces, is a scientific challenge. Molecular-level understanding of hydrophobic effects and their macroscopic consequences, in particular, is critical to many applications. Macroscopically, a surface is classified as hydrophilic or hydrophobic depending on the contact angle formed by a water droplet. Because hydrophobic surfaces tend to cause water slip whereas hydrophilic ones do not, the former surfaces can yield self-cleaning garments and ice-repellent materials whereas the latter cannot. The results presented herein suggest that this dichotomy might be purely coincidental. Our simulation results demonstrate that hydrophilic surfaces can show features typically associated with hydrophobicity, namely liquid water slip. Further analysis provides details on the molecular mechanism responsible for this surprising result. PMID:21911406

  11. Temperature dependence of the structure of protein hydration water and the liquid-liquid transition.

    PubMed

    Accordino, S R; Malaspina, D C; Rodriguez Fris, J A; Alarcón, L M; Appignanesi, G A

    2012-03-01

    We study the temperature dependence of the structure and orientation of the first hydration layers of the protein lysozyme and compare it with the situation for a model homogeneous hydrophobic surface, a graphene sheet. We show that in both cases these layers are significantly better structured than bulk water. The geometrical constraint of the interface makes the water molecules adjacent to the surface lose one water-water hydrogen bond and expel the fourth neighbors away from the surface, lowering local density. We show that a decrease in temperature improves the ordering of the hydration water molecules, preserving such a geometrical effect. For the case of graphene, this favors an ice Ih-like local structuring, similar to the water-air interface but in the opposite way along the c axis of the basal plane (while the vicinal water molecules of the air interface orient a hydrogen atom toward the surface, the oxygens of the water molecules close to the graphene plane orient a lone pair in such a direction). In turn, the case of the first hydration layers of the lysozyme molecule is shown to be more complicated, but still displaying signs of both kinds of behavior, together with a tendency of the proximal water molecules to hydrogen bond to the protein both as donors and as acceptors. Additionally, we make evident the existence of signatures of a liquid-liquid transition (Widom line crossing) in different structural parameters at the temperature corresponding to the dynamic transition incorrectly referred to as "the protein glass transition."

  12. Extraction of pesticides in water samples using vortex-assisted liquid-liquid microextraction.

    PubMed

    Jia, Chunhong; Zhu, Xiaodan; Wang, Jihua; Zhao, Ercheng; He, Min; Chen, Li; Yu, Pingzhong

    2010-09-10

    A simple solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-microECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30 microL toluene used as extraction solvent were directly injected into a 25 mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835-1115 and limits of detection below 0.010 microg L(-1) were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r(2)) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5 microg L(-1). Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72-106.3% were obtained.

  13. 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 π-π 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.

  14. Self-assembly and orientation of hydrogen-bonded oligothiophene polymorphs at liquid-membrane-liquid interfaces.

    PubMed

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

    2011-10-19

    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 π-π 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.

  15. 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.

  16. IR and Raman spectra of liquid water: theory and interpretation.

    PubMed

    Auer, B M; Skinner, J L

    2008-06-14

    IR and Raman (parallel- and perpendicular-polarized) spectra in the OH stretch region for liquid water were measured some years ago, but their interpretation is still controversial. In part, this is because theoretical calculation of such spectra for a neat liquid presents a formidable challenge due to the coupling between vibrational chromophores and the effects of motional narrowing. Recently we proposed an electronic structure/molecular dynamics method for calculating spectra of dilute HOD in liquid D(2)O, which relied on ab initio calculations on clusters to provide a map from nuclear coordinates of the molecules in the liquid to OH stretch frequencies, transition dipoles, and polarizabilities. Here we extend this approach to the calculation of couplings between chromophores. From the trajectories of the fluctuating local-mode frequencies, transition moments, and couplings, we use our recently developed time-averaging approximation to calculate the line shapes. Our results are in good agreement with experiment for the IR and Raman line shapes, and capture the significant differences among them. Our analysis shows that while the coupling between chromophores is relatively modest, it nevertheless produces delocalization of the vibrational eigenstates over up to 12 chromophores, which has a profound effect on the spectroscopy. In particular, our results demonstrate that the peak in the parallel-polarized Raman spectrum at about 3250 wavenumbers is collective in nature.

  17. 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.

  18. Liquid water simulations with the density fragment interaction approach.

    PubMed

    Hu, Xiangqian; Jin, Yingdi; Zeng, Xiancheng; Hu, Hao; Yang, Weitao

    2012-06-07

    We reformulate the density fragment interaction (DFI) approach [Fujimoto and Yang, J. Chem. Phys., 2008, 129, 054102.] to achieve linear-scaling quantum mechanical calculations for large molecular systems. Two key approximations are developed to improve the efficiency of the DFI approach and thus enable the calculations for large molecules: the electrostatic interactions between fragments are computed efficiently by means of polarizable electrostatic-potential-fitted atomic charges; and frozen fragment pseudopotentials, similar to the effective fragment potentials that can be fitted from interactions between small molecules, are employed to take into account the Pauli repulsion effect among fragments. Our reformulated and parallelized DFI method demonstrates excellent parallel performance based on the benchmarks for the system of 256 water molecules. Molecular dynamics simulations for the structural properties of liquid water also show a qualitatively good agreement with experimental measurements including the heat capacity, binding energy per water molecule, and the radial distribution functions of atomic pairs of O-O, O-H, and H-H. With this approach, large-scale quantum mechanical simulations for water and other liquids become feasible.

  19. One-dimensional model for water and aqueous solutions. I. Pure liquid water

    NASA Astrophysics Data System (ADS)

    Ben-Naim, Arieh

    2008-01-01

    Two simplified one-dimensional models for waterlike particles are studied. One is referred to as the primitive model which is a simplified version of a model introduced by Ben-Naim in 1992 [Statistical Thermodynamics for Chemists and Biochemists (Plenum, New York, 1992)]. The second, referred to as the primitive cluster model, is a simplified version of the model used by Lovett and Ben-Naim in 1969 [J. Chem. Phys. 51, 3108 (1969)]. The two models are shown to be nearly equivalent and both exhibit some of the most characteristic behavior of liquid water. It is argued that a key feature of the molecular interactions—the correlation between the strong binding energy and low local density—is essential for the manifestation of the anomalous behavior of liquid water. It is also essential for the understanding of the outstanding behavior of liquid water.

  20. Selective extraction of emerging contaminants from water samples by dispersive liquid-liquid microextraction using functionalized ionic liquids.

    PubMed

    Yao, Cong; Li, Tianhao; Twu, Pamela; Pitner, William R; Anderson, Jared L

    2011-03-25

    Functionalized ionic liquids containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion were used as extraction solvents in dispersive liquid-liquid microextraction (DLLME) for the extraction of 14 emerging contaminants from water samples. The extraction efficiencies and selectivities were compared to those of an in situ IL DLLME method which uses an in situ metathesis reaction to exchange 1-butyl-3-methylimidazolium chloride (BMIM-Cl) to 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMIM-NTf(2)). Compounds containing tertiary amine functionality were extracted with high selectivity and sensitivity by the 1-(6-amino-hexyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (HNH(2)MPL-FAP) IL compared to other FAP-based ILs and the BMIM-NTf(2) IL. On the other hand, polar or acidic compounds without amine groups exhibited higher enrichment factors using the BMIM-NTf(2) IL. The detection limits for the studied analytes varied from 0.1 to 55.1 μg/L using the traditional IL DLLME method with the HNH(2)MPL-FAP IL as extraction solvent, and from 0.1 to 55.8 μg/L using in situ IL DLLME method with BMIM-Cl+LiNTf(2) as extraction solvent. A 93-fold decrease in the detection limit of caffeine was observed when using the HNH(2)MPL-FAP IL compared to that obtained using in situ IL DLLME method. Real water samples including tap water and creek water were analyzed with both IL DLLME methods and yielded recoveries ranging from 91% to 110%.

  1. A "First Principles" Potential Energy Surface for Liquid Water from VRT Spectroscopy of Water Clusters

    SciTech Connect

    Goldman, N; Leforestier, C; Saykally, R J

    2004-05-25

    We present results of gas phase cluster and liquid water simulations from the recently determined VRT(ASP-W)III water dimer potential energy surface. VRT(ASP-W)III is shown to not only be a model of high ''spectroscopic'' accuracy for the water dimer, but also makes accurate predictions of vibrational ground-state properties for clusters up through the hexamer. Results of ambient liquid water simulations from VRT(ASP-W)III are compared to those from ab initio Molecular Dynamics, other potentials of ''spectroscopic'' accuracy, and to experiment. The results herein represent the first time that a ''spectroscopic'' potential surface is able to correctly model condensed phase properties of water.

  2. 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.)

  3. Shock wave initiated by an ion passing through liquid water

    NASA Astrophysics Data System (ADS)

    Surdutovich, Eugene; Solov'Yov, Andrey V.

    2010-11-01

    We investigate the shock wave produced by an energetic ion in liquid water. This wave is initiated by a rapid energy loss when the ion moves through the Bragg peak. The energy is transferred from the ion to secondary electrons, which then transfer it to the water molecules. The pressure in the overheated water increases by several orders of magnitude and drives a cylindrical shock wave on a nanometer scale. This wave eventually weakens as the front expands further; but before that, it may contribute to DNA damage due to large pressure gradients developed within a few nanometers from the ion’s trajectory. This mechanism of DNA damage may be a very important contribution to the direct chemical effects of low-energy electrons and holes.

  4. 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.

  5. Thermodynamic properties of liquid water from a polarizable intermolecular potential.

    PubMed

    Yigzawe, Tesfaye M; Sadus, Richard J

    2013-01-28

    Molecular dynamics simulation results are reported for the pressure, isothermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient and speed of sound of liquid water using a polarizable potential [Li et al., J. Chem. Phys. 127, 154509 (2007)]. These properties were obtained for a wide range of temperatures and pressures at a common liquid density using the treatment of Lustig [J. Chem. Phys. 100, 3048 (1994)] and Meier and Kabelac [J. Chem. Phys. 124, 064104 (2006)], whereby thermodynamic state variables are expressible in terms of phase-space functions determined directly from molecular dynamics simulations. Comparison with experimental data indicates that the polarizable potential can be used to predict most thermodynamic properties with a very good degree of accuracy.

  6. Size-Resolved Photoelectron Anisotropy of Gas Phase Water Clusters and Predictions for Liquid Water

    NASA Astrophysics Data System (ADS)

    Hartweg, Sebastian; Yoder, Bruce L.; Garcia, Gustavo A.; Nahon, Laurent; Signorell, Ruth

    2017-03-01

    We report the first measurements of size-resolved photoelectron angular distributions for the valence orbitals of neutral water clusters with up to 20 molecules. A systematic decrease of the photoelectron anisotropy is found for clusters with up to 5-6 molecules, and most remarkably, convergence of the anisotropy for larger clusters. We suggest the latter to be the result of a local short-range scattering potential that is fully described by a unit of 5-6 molecules. The cluster data and a detailed electron scattering model are used to predict the anisotropy of slow photoelectrons in liquid water. Reasonable agreement with experimental liquid jet data is found.

  7. Liquid water and resurfacing of Enceladus' south polar terrain

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    Enceladus are the only solid objects in the Solar System to be sufficiently geologically active for their internal heat to be detected by remote sensing. Interestingly, 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 ([1], [2]). The current polar location of the thermal anomaly can possibly be explained by diapirinduced reorientation of the satellite [3], but the triggering of the thermal anomaly and the heat power required to sustain it over geologic timescales remain problematic. Using a three-dimensional viscoelastic numerical model simulating the response of Enceladus to tidal forcing, we have demonstrated in a previous recent study [4] 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 (Fig. 1). Moreover, as tidally-induced heat must be generated over a relatively broad region in the southern hemisphere to explain the observed thermal emission, we proposed that this heat is then transferred toward the south polar terrain where it could be episodically released during relatively short resurfacing events. In the present study, we investigate the thermal stability of localized liquid water reservoir at the rock-ice interface by performing simulations of thermal convection in three-dimensional spherical geometry with the numerical tool OEDIPUS ([5],[6]) and by computing the corresponding dissipation pattern using the method developped in [4]. Where liquid water is present, a constant temperature equal to the melting temperature of water ice is prescribed at the base of the ice shell. Outside this region, a constant heat flux owing to the radiogenic power coming out of the silicate core is prescribed. Figure 2 illustrates the temperature field obtained for varying size of the liquid reservoir (ranging from 60o to 120o). These preliminary results

  8. Ionic liquid foam floatation coupled with ionic liquid dispersive liquid-liquid microextraction for the separation and determination of estrogens in water samples by high-performance liquid chromatography with fluorescence detection.

    PubMed

    Zhang, Rui; Wang, Chuanliu; Yue, Qiaohong; Zhou, Tiecheng; Li, Na; Zhang, Hanqi; Hao, Xiaoke

    2014-11-01

    An ionic liquid foam floatation coupled with ionic liquid dispersive liquid-liquid microextraction method was proposed for the extraction and concentration of 17-α-estradiol, 17-β-estradiol-benzoate, and quinestrol in environmental water samples by high-performance liquid chromatography with fluorescence detection. 1-Hexyl-3-methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion-pairing and salting-out agent NH4 PF6 was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1-hexyl-3-methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid-liquid microextraction was widened.

  9. 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.

  10. Determination of trace lead in biological and water samples with dispersive liquid-liquid microextraction preconcentration.

    PubMed

    Liang, Pei; Sang, Hongbo

    2008-09-01

    A new method for the determination of trace lead was developed by dispersive liquid-liquid microextraction preconcentration and graphite furnace atomic absorption spectrometry. In the proposed approach, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was used as a chelating agent, and carbon tetrachloride and ethanol were selected as extraction and dispersive solvents. Some factors influencing the extraction efficiency of lead and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent, and extraction time, were studied and optimized. Under the optimum conditions, the enrichment factor of this method for lead was reached at 78. The detection limit for lead was 39 ng L(-1) (3 sigma), and the relative standard deviation (RSD) was 3.2% (n=7, c=10 ng mL(-1)). The method was successfully applied to the determination of trace amounts of lead in human urine and water samples.

  11. Interfacial thermodynamics of water and six other liquid solvents.

    PubMed

    Pascal, Tod A; Goddard, William A

    2014-06-05

    We examine the thermodynamics of the liquid-vapor interface by direct calculation of the surface entropy, enthalpy, and free energy from extensive molecular dynamics simulations using the two-phase thermodynamics (2PT) method. Results for water, acetonitrile, cyclohexane, dimethyl sulfoxide, hexanol, N-methyl acetamide, and toluene are presented. We validate our approach by predicting the interfacial surface tensions (IFT--excess surface free energy per unit area) in excellent agreement with the mechanical calculations using Kirkwood-Buff theory. Additionally, we evaluate the temperature dependence of the IFT of water as described by the TIP4P/2005, SPC/Ew, TIP3P, and mW classical water models. We find that the TIP4P/2005 and SPC/Ew water models do a reasonable job of describing the interfacial thermodynamics; however, the TIP3P and mW are quite poor. We find that the underprediction of the experimental IFT at 298 K by these water models results from understructured surface molecules whose binding energies are too weak. Finally, we performed depth profiles of the interfacial thermodynamics which revealed long tails that extend far into what would be considered bulk from standard Gibbs theory. In fact, we find a nonmonotonic interfacial free energy profile for water, a unique feature that could have important consequences for the absorption of ions and other small molecules.

  12. 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.

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

    PubMed

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

    2015-06-17

    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.

  14. Storage tank with liquid insulator for storing cryogenic fluids using water displacement

    SciTech Connect

    McCabe, J.S.; Stafford, D.C.; Laverman, R.J.

    1980-06-24

    For storing cryogenic liquids such as LNG at or slightly above atmospheric pressure, this design uses a tank with insulated vertical walls and an insulated top located in and surrounded by a body of water in communication with a layer of water inside the tank; the level of the tank contents can thus be controlled using the water-displacement principle. A layer of insulating liquid having a specific gravity lower than water and higher than LNG (or the cryogenic liquid being stored) separates the water and LNG while remaining liquid at the cryogenic temperature; the insulating liquid - pentanes, particularly isopentane, are suitable - must be essentially immiscible with water, LNG, or both. For preventing turbulent mixing of the water and LNG while the tank is being filled or emptied, a float in the form of a closed or open shell made partially or entirely of insulating material extends over the water layer and contains the insulating liquid.

  15. 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

  16. 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.

  17. Water-based scintillators for large-scale liquid calorimetry

    SciTech Connect

    Winn, D.R.; Raftery, D.

    1985-02-01

    We have investigated primary and secondary solvent intermediates in search of a recipe to create a bulk liquid scintillator with water as the bulk solvent and common fluors as the solutes. As we are not concerned with energy resolution below 1 MeV in large-scale experiments, light-output at the 10% level of high-quality organic solvent based scintillators is acceptable. We have found encouraging performance from industrial surfactants as primary solvents for PPO and POPOP. This technique may allow economical and environmentally safe bulk scintillator for kiloton-sized high energy calorimetry.

  18. 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

  19. Radar and the Detection of Liquid Water on Mars

    NASA Technical Reports Server (NTRS)

    Roth, L. E.; Saunders, R. S.

    1985-01-01

    Detection of the seasonally variable radar reflectivity in the Goldstone Mars data (the Solis Lacus radar anomaly and the proposed interpretation in terms of the near-surface presence of liquid water created a controversy in the planetary science community. Over the past year, skepticism was voiced about the reality of the phenomenon of a seasonally variable radar reflectivity anywhere on Mars. The necessary background information and the pertinent data are reviewed in a format perhaps more convincing than that employed in the original presentation of the discovery. A summary of the results and recommendations for future work are included.

  20. Glass polymorphism in glycerol-water mixtures: I. A computer simulation study.

    PubMed

    Jahn, David A; Wong, Jessina; Bachler, Johannes; Loerting, Thomas; Giovambattista, Nicolas

    2016-04-28

    We perform out-of-equilibrium molecular dynamics (MD) simulations of water-glycerol mixtures in the glass state. Specifically, we study the transformations between low-density (LDA) and high-density amorphous (HDA) forms of these mixtures induced by compression/decompression at constant temperature. Our MD simulations reproduce qualitatively the density changes observed in experiments. Specifically, the LDA-HDA transformation becomes (i) smoother and (ii) the hysteresis in a compression/decompression cycle decreases as T and/or glycerol content increase. This is surprising given the fast compression/decompression rates (relative to experiments) accessible in MD simulations. We study mixtures with glycerol molar concentration χ(g) = 0-13% and find that, for the present mixture models and rates, the LDA-HDA transformation is detectable up to χ(g) ≈ 5%. As the concentration increases, the density of the starting glass (i.e., LDA at approximately χ(g) ≤ 5%) rapidly increases while, instead, the density of HDA remains practically constant. Accordingly, the LDA state and hence glass polymorphism become inaccessible for glassy mixtures with approximately χ(g) > 5%. We present an analysis of the molecular-level changes underlying the LDA-HDA transformation. As observed in pure glassy water, during the LDA-to-HDA transformation, water molecules within the mixture approach each other, moving from the second to the first hydration shell and filling the first interstitial shell of water molecules. Interestingly, similar changes also occur around glycerol OH groups. It follows that glycerol OH groups contribute to the density increase during the LDA-HDA transformation. An analysis of the hydrogen bond (HB)-network of the mixtures shows that the LDA-HDA transformation is accompanied by minor changes in the number of HBs of water and glycerol. Instead, large changes in glycerol and water coordination numbers occur. We also perform a detailed analysis of the effects that

  1. Modification of polymorphisms in polyvinylidene fluoride thin films via water and hydrated salt.

    PubMed

    Song, Rui; Xia, Guangmei; Xing, Xueqing; He, Linghao; Zhao, Qiaoling; Ma, Zhi

    2013-07-01

    In this study, the effects of solvent and magnesium chloride hexahydrate (MgCl2·6H2O) on the polymorphism of polyvinylidene fluoride (PVDF) thin films were systematically investigated. Wherein, N,N-dimethylformamide (DMF) and water with different volume ratio were used as mixed solvents to obtain the solution casting films, P series. In addition, MgCl2·6H2O was comparatively added to prepare PVDF/MgCl2·6H2O hybrid films, P-M series. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimeter (DSC) were utilized to study the influence of the water content in the mixed solvents and the hydrated salt on crystallization behavior of PVDF. Further, the morphologic images from scanning electronic microscopy (SEM) and polarized optical microscopy (POM), as well as the pizoelectirc d33 test also supplies the corresponding evidences. As indicated, the water in the mixed solvent shows different effect on main crystal forms of PVDF. At low water content, the solvents may favor the polar phase (β- and γ-phase) mainly by hydrogen bonds interactions between PVDF and water, together with dipolar interactions between PVDF and DMF. At high water content, the nonsolvent water will impose confinement effect on polymer chain diffusion and crystal growth which facilitate the formation of α-phase PVDF. Moreover, magnesium chloride hexahydrate mainly functioned as the nucleation sites for PVDF crystallization. The result of small-angle X-ray scattering (SAXS) implies the content of water or MgCl2·6H2O has little impact on the structure of the long period.

  2. 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)

  3. Determination of organic compounds in water using dispersive liquid-liquid microextraction.

    PubMed

    Rezaee, Mohammad; Assadi, Yaghoub; Milani Hosseini, Mohammad-Reza; Aghaee, Elham; Ahmadi, Fardin; Berijani, Sana

    2006-05-26

    A new microextraction technique termed dispersive liquid-liquid microextraction (DLLME) was developed. DLLME is a very simple and rapid method for extraction and preconcentration of organic compounds from water samples. In this method, the appropriate mixture of extraction solvent (8.0 microL C2Cl4) and disperser solvent (1.00 mL acetone) are injected into the aqueous sample (5.00 mL) by syringe, rapidly. Therefore, cloudy solution is formed. In fact, it is consisted of fine particles of extraction solvent which is dispersed entirely into aqueous phase. After centrifuging, the fine particles of extraction solvent are sedimented in the bottom of the conical test tube (5.0 +/- 0.2 microL). The performance of DLLME is illustrated with the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by using gas chromatography-flame ionization detection (GC-FID). Some important parameters, such as kind of extraction and disperser solvent and volume of them, and extraction time were investigated. Under the optimum conditions the enrichment factor ranged from 603 to 1113 and the recovery ranged from 60.3 to 111.3%. The linear range was 0.02-200 microg/L (four orders of magnitude) and limit of detection was 0.007-0.030 microg/L for most of analytes. The relative standard deviations (RSDs) for 2 microg/L of PAHs in water by using internal standard were in the range 1.4-10.2% (n = 5). The recoveries of PAHs from surface water at spiking level of 5.0 microg/L were 82.0-111.0%. The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds (benzene, toluene, ethyl benzene, and xylenes) from water samples were studied. The advantages of DLLME method are simplicity of operation, rapidity, low cost, high recovery, and enrichment factor.

  4. On the implications of aerosol liquid water and phase separation for organic aerosol mass

    EPA Science Inventory

    Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to org...

  5. 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

  6. 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.

  7. 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.

  8. Glass polymorphism in glycerol–water mixtures: I. A computer simulation study

    PubMed Central

    Jahn, David A.; Wong, Jessina; Bachler, Johannes; Loerting, Thomas

    2016-01-01

    We perform out-of-equilibrium molecular dynamics (MD) simulations of water–glycerol mixtures in the glass state. Specifically, we study the transformations between low-density (LDA) and high-density amorphous (HDA) forms of these mixtures induced by compression/decompression at constant temperature. Our MD simulations reproduce qualitatively the density changes observed in experiments. Specifically, the LDA–HDA transformation becomes (i) smoother and (ii) the hysteresis in a compression/decompression cycle decreases as T and/or glycerol content increase. This is surprising given the fast compression/decompression rates (relative to experiments) accessible in MD simulations. We study mixtures with glycerol molar concentration χ g = 0–13% and find that, for the present mixture models and rates, the LDA–HDA transformation is detectable up to χ g ≈ 5%. As the concentration increases, the density of the starting glass (i.e., LDA at approximately χ g ≤ 5%) rapidly increases while, instead, the density of HDA remains practically constant. Accordingly, the LDA state and hence glass polymorphism become inaccessible for glassy mixtures with approximately χ g > 5%. We present an analysis of the molecular-level changes underlying the LDA–HDA transformation. As observed in pure glassy water, during the LDA-to-HDA transformation, water molecules within the mixture approach each other, moving from the second to the first hydration shell and filling the first interstitial shell of water molecules. Interestingly, similar changes also occur around glycerol OH groups. It follows that glycerol OH groups contribute to the density increase during the LDA–HDA transformation. An analysis of the hydrogen bond (HB)-network of the mixtures shows that the LDA–HDA transformation is accompanied by minor changes in the number of HBs of water and glycerol. Instead, large changes in glycerol and water coordination numbers occur. We also perform a detailed analysis of the

  9. Hot electron dominated rapid transverse ionization growth in liquid water.

    PubMed

    Brown, Michael S; Erickson, Thomas; Frische, Kyle; Roquemore, William M

    2011-06-20

    Pump/probe optical-transmission measurements are used to monitor in space and time the ionization of a liquid column of water following impact of an 800-nm, 45-fs pump pulse. The pump pulse strikes the 53-μm-diameter column normal to its axis with intensities up to 2 × 10(15) W/cm2. After the initial photoinization and for probe delay times < 500 fs, the neutral water surrounding the beam is rapidly ionized in the transverse direction, presumably by hot electrons with initial velocities of 0.55 times the speed of light (relativistic kinetic energy of ~100 keV). Such velocities are unusual for condensed-matter excitation at the stated laser intensities.

  10. 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...

  11. Rapid determination of octanol-water partition coefficient using vortex-assisted liquid-liquid microextraction.

    PubMed

    Román, Iván P; Mastromichali, Anna; Tyrovola, Konstantina; Canals, Antonio; Psillakis, Elefteria

    2014-02-21

    Vortex-assisted liquid-liquid microextraction (VALLME) coupled with high-performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol-water partitioning coefficients (Kow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2min were enough to achieve equilibrium conditions between the octanolic and aqueous phases. Upon equilibration, separation was achieved using centrifugation and the octanolic microdrop was collected and analyzed in a HPLC system. Six model compounds with logKow values ranging between ∼0.5 and 3.5 were used during the present investigations. The proposed method produced logKow values that were consistent with previously published values and the recorded uncertainty was well within the acceptable log unit range. Overall, the key features of the proposed Kow determination procedure comprised speed, reliability, simplicity, low cost and minimal solvent consumption.

  12. Response functions near the liquid-liquid critical point of ST2 water

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    We simulate the ST2 water model for time periods up to 1000 ns, and for four different system sizes, N = 63, 73, 83, and 93. We locate the liquid-liquid phase transition line and its critical point in the supercooled region. Near the liquidliquid phase transition line, we observe that the system continuously flips between the low-density and high-density liquid phases. We analyze the transition line further by calculating two thermodynamic response functions, the isobaric specific heat capacity CP and the isothermal compressibility KT. We use two different methods: (i) from fluctuations and (ii) with the relevant thermodynamic derivative. We find that, within the accuracy of our simulations, the maxima of two different response functions occur at the same temperatures. The lines of CP and KT maxima below the critical pressure approximate the Widom line which is continuous with the line of first-order transitions in the two-phase region where we observe the phase flipping.

  13. Ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction followed high-performance liquid chromatography for the determination of ultraviolet filters in environmental water samples.

    PubMed

    Zhang, Yufeng; Lee, Hian Kee

    2012-10-31

    In the present study, a rapid, highly efficient and environmentally friendly sample preparation method named ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction (IL-USA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for the extraction and preconcentration of four benzophenone-type ultraviolet (UV) filters (viz. benzophenone (BP), 2-hydroxy-4-methoxybenzophenone (BP-3), ethylhexyl salicylate (EHS) and homosalate (HMS)) from three different water matrices. The procedure was based on a ternary solvent system containing tiny droplets of ionic liquid (IL) in the sample solution formed by dissolving an appropriate amount of the IL extraction solvent 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) in a small amount of water-miscible dispersive solvent (methanol). An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvents, ionic strength, pH and extraction time) were evaluated. Under optimal conditions, the proposed method provided good enrichment factors in the range of 354-464, and good repeatability of the extractions (RSDs below 6.3%, n=5). The limits of detection were in the range of 0.2-5.0 ng mL(-1), depending on the analytes. The linearities were between 1 and 500 ng mL(-1) for BP, 5 and 500 ng mL(-1) for BP-3 and HMS and 10 and 500 ng mL(-1) for EHS. Finally, the proposed method was successfully applied to the determination of UV filters in river, swimming pool and tap water samples and acceptable relative recoveries over the range of 71.0-118.0% were obtained.

  14. IR spectra of water droplets in no man's land and the location of the liquid-liquid critical point.

    PubMed

    Ni, Yicun; Skinner, J L

    2016-09-28

    No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, using our E3B3 model, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others.

  15. Quantitation of antioxidants in water samples using ionic liquid dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection.

    PubMed

    Sobhi, Hamid Reza; Kashtiaray, Amir; Farahani, Hadi; Farahani, Mohammad Reza

    2011-01-01

    A simple and efficient method, ionic liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), has been applied for the extraction and determination of some antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) in water samples. The microextraction efficiency factors were investigated and optimized: 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM][PF(6)] (0.06 g) as extracting solvent, methanol (0.5 mL) as disperser solvent without salt addition. Under the selected conditions, enrichment factors up to 48-fold, limits of detection (LODs) of 5.0-10.0 ng/mL and dynamic linear ranges of 25-1500 ng/mL were obtained. A reasonable repeatability (RSD≤11.8%, n=5) with satisfactory linearity (r(2)≥0.9954) of the results illustrated a good performance of the presented method. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 118%. Finally, the method was successfully applied for determination of the analytes in several real water samples.

  16. Improved Polymerase Chain Reaction-restriction Fragment Length Polymorphism Genotyping of Toxic Pufferfish by Liquid Chromatography/Mass Spectrometry

    PubMed Central

    Miyaguchi, Hajime

    2016-01-01

    An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively. The mobile phase, consisting of 400 mM 1,1,1,3,3,3-hexafluoro-2-propanol, 15 mM triethylamine (pH 7.9) and methanol, is delivered at a flow rate of 0.4 ml/min. The cycle time for LC/ESI-MS analysis is 8 min including equilibration of the column. Deconvolution software having an isotope distribution model of the oligonucleotide is used to calculate the corresponding monoisotopic mass from the mass spectrum. For analysis of oligonucleotides (range 26-79 nucleotides), mass accuracy was 0.62 ± 0.74 ppm (n = 280) and excellent accuracy and precision were sustained for 180 hr without use of a lock mass standard. PMID:27684516

  17. Ionic liquid-based dispersive liquid-liquid microextraction followed high-performance liquid chromatography for the determination of organophosphorus pesticides in water sample.

    PubMed

    He, Lijun; Luo, Xianli; Xie, Hongxue; Wang, Chunjian; Jiang, Xiuming; Lu, Kui

    2009-11-23

    Using 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)MIM][PF(6)]) ionic liquid as extraction solvent, organophosphorus pesticides (OPPs) (parathion, phoxim, phorate and chlorpyifos) in water were determined by dispersive liquid-liquid microextraction (DLLME) combined with high-performance liquid chromatography (HPLC). The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C(8)MIM][PF(6)] dispersed entirely into sample solution with the help of disperser solvent (methanol). Parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, centrifugal time, salt addition, extraction temperature and sample pH were investigated and optimized. Under the optimized conditions, up to 200-fold enrichment factor of analytes and acceptable extraction recovery (>70%) were obtained. The calibration curves were linear in the concentration range of 10.5-1045.0 microg L(-1) for parathion, 10.2-1020.0 microg L(-1) for phoxim, 54.5-1089.0 microg L(-1) for phorate and 27.2-1089.0 microg L(-1) for chlorpyifos, respectively. The limits of detection calculated at a signal-to-noise ratio of 3 were in the range of 0.1-5.0 microg L(-1). The relative standard deviations for seven replicate experiments at 200 microg L(-1) concentration level were less than 4.7%. The proposed method was applied to the analysis of four different sources water samples (tap, well, rain and Yellow River water) and the relative recoveries of spiked water samples are 99.9-115.4%, 101.8-113.7% and 87.3-117.6% at three different concentration levels of 75, 200 and 1000 microg L(-1), respectively.

  18. [Effects of water deficiency on mitochondrial functions and polymorphism of respiratory enzymes in plants].

    PubMed

    Rakhmankulova, Z F; Shuĭskaia, E V; Rogozhnikova, E S

    2013-01-01

    In plants, adaptive-compensatory responses to stress always entail additional energy expenditure. A suggestion was brought forward that in plants growing under conditions of water stress there is a relationship between genetic variability of respiratory enzymes and their functional significance. With Kochia prostrate (L.) Schrad. as a case study, intraspecies genetic polymorphism under the conditions of drought has been analyzed using typical protein markers which, considering their functional importance, can be viewed as respiratory enzymes. Out of eight protein markers examined, four enzymes were singled out for which dominating combination of genotypes Dia B (a), G6pd (a), Gdh (c), and Mdh A (a) was incidental. In all populations from arid and semiarid zone, these genotypes frequency of occurrence was in the range of 0.53-1.0, i.e., it comprised more than 50% of the whole variety of combinations. Thus, it seems plausible that this combination of genotypes can be an "adaptive collection" for K. prostrata populations growing in arid habitats. A characteristic feature of the picked out enzymes is their belonging to NAD(P)(+)-depending oxidoreductases that play a key role in functioning and redox-regulation of respiratory metabolism in course of adapting to water deficiency. It is suggested that the presence of such well-balanced co-adaptive genotype combinations, that provide enzymes important in terms of energetics, determine the formation of energetic and redox-balances during the process of adaptation to water stress.

  19. 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

  20. Relationship between optical extinction and liquid water content in fogs

    NASA Astrophysics Data System (ADS)

    Klein, C.; Dabas, A.

    2014-05-01

    Studies carried out in the late 1970s suggest that a simple linear relationship exists in practice between the optical extinction in the thermal IR and the liquid water content (LWC) in fogs. Such a relationship opens the possibility to monitor the vertical profile of the LWC in fogs with a rather simple backscatter lidar. Little is known on how the LWC varies as a function of height and during the fog life cycle, so the new measurement technique would help understand fog physics and provide valuable data for improving the quality of fog forecasts. In this paper, the validity of the linear relationship is revisited in the light of recent observations of fog droplet size distributions measured with a combination of sensors covering a large range of droplet radii. In particular, large droplets (radius above 15 μm) are now detected, which was not the case in the late 1970s. The results confirm that the linear relationship still holds, at least for the mostly radiative fogs observed during the campaign. The impact of the precise value of the real and imaginary parts of the refractive index on the coefficient of the linear relationship is also studied. The usual practice considers that droplets are made of pure water. This assumption is probably valid for big drops, but it may be questioned for small ones since droplets are formed from condensation nuclei of highly variable chemical composition. The study suggests that the precise nature of condensation nuclei will primarily affect rather light fogs with small droplets and light liquid water contents.

  1. Crystal structure of an anhydrous form of trehalose: structure of water channels of trehalose polymorphism.

    PubMed

    Nagase, H; Ogawa, N; Endo, T; Shiro, M; Ueda, H; Sakurai, M

    2008-07-31

    alpha, alpha-Trehalose (trehalose) is a nonreducing disaccharide of glucose and is accumulated at high concentrations in some anhydrobiotic organisms, which can survive without water for long periods and rapidly resume active metabolism upon hydration. Although it has been proposed that the intriguing mechanism of bioprotection in anhydrobiosis is conferred by a water channel, details of such a channel have yet to be revealed. We determined the crystal structure of a trehalose anhydrate to further understand the relationship between the structure of water channels and the trehalose polymorph. The space group was identical to that of the dihydrate and the lattice constants were also very similar. Among the five intermolecular hydrogen bonds between the trehalose molecules, four were preserved in the anhydrate. If dehydration of the dihydrate is slow and/or gentle enough to preserve the hydrogen bonds, transformation from the dihydrate to the anhydrate may occur. There are two different holes, hole-1 and hole-2, along one crystal axis. Hole-1 is constructed by trehalose molecules with a screw diad at its center, while hole-2 has a smaller diameter and is without a symmetry operator. Because of the screw axis at the center of hole-1, hollows are present at the side of the hole with diameters roughly equal to that of hole-1. Hole-1 and side pockets followed by hollows correspond to the positions of two water molecules of the dihydrate. The side hollows of the water channel are also observed in the water-filled hole of the dihydrate. Consequently, hole-1 is considered to be a one-dimensional water channel with side pockets. We also calculated molecular and crystal energies to examine the rapid water uptake of the anhydrate. It was demonstrated that the intermolecular interactions in the anhydrate were weaker than in the other anhydrous form, and probably also than those in amorphous trehalose. The anhydrate provides water capture for another solid form and gives

  2. Ionic liquids for improving the extraction of NSAIDs in water samples using dispersive liquid-liquid microextraction by high performance liquid chromatography-diode array-fluorescence detection.

    PubMed

    Toledo-Neira, Carla; Álvarez-Lueje, Alejandro

    2015-03-01

    A rapid, sensitive and efficient analytical method based on the use of ionic liquids for determination of non-steroidal anti-inflammatory drugs (NSAIDs) in water samples was developed. High-performance liquid chromatography equipped with a diode array and fluorescence detector was used for quantification of ketoprofen, ibuprofen and diclofenac in tap and river water samples. This new method relies on the use of two ionic liquids with multiple functionalities: one functions as an extraction solvent (1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the other changes the polarity in the aqueous medium (1-butyl-3-methylimidazolium tetrafluoroborate, ([BMIM][BF4]). Factors such as the type and volume of the ILs and dispersive solvent, sample volume, and centrifugation time were investigated and optimized. The optimized method exhibited good precision, with relative standard deviation values between 2% and 3%, for the three NSAIDs. Limits of detection achieved for all of the analytes were between 17 and 95 ng mL(-1), and the recoveries ranged from 89% to 103%. Furthermore, the enrichment factors ranged from 49 to 57. The proposed method was successfully applied to the analysis of NSAIDs in tap and river water samples.

  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. Use of spacecraft data to derive regions on Mars where liquid water would be stable

    PubMed Central

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

    2001-01-01

    Combining Viking pressure and temperature data with Mars Orbital Laser Altimeter 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°. 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 were present. Locations of stability appear to correlate with the distribution of valley networks. PMID:11226204

  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. 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.

  8. Application of empirical ionic models to SiO 2 liquid: Potential model approximations and integration of SiO 2 polymorph data

    NASA Astrophysics Data System (ADS)

    Erikson, Robert L.; Hostetler, Charles J.

    1987-05-01

    Structural and thermodynamic properties of crystalline SiO 2 and SiO 2 liquid have been examined with Monte Carlo (MC), molecular dynamics (MD), and energy minimization (EM) calculations using several ionic potential models obtained from the literature. The MC and MD methods calculate the same structural and thermodynamic properties for liquids when the same potential model is used. The Ewald (1921) method of calculating coulomb interactions reproduced most successfully the structure of liquid silica. Approximating the coulomb interaction by eliminating the inverse lattice sum results in predicted bond distances that are too short and an average angle of approximately 180°. Introduction of a cut-off in the potential energy function produces irregular tetrahedra and inconsistencies in predicted Si-O coordination in silica liquid. The system internal energies show that liquid structures derived from random starting configurations can be metastable relative to structures calculated from crystalline starting configurations. The static lattice properties of the polymorphs alpha-quartz, coesite, and stishovite were used to evaluate further the accuracy of different sets of repulsive parameters for the full Ewald ionic model. Most of the models studied reproduced poorly the measured structures and elastic constants of the polymorphs. The major weakness of the ionic model is the unreasonably large Si-O bond strength (120 × 10 -12 ergs/bond) when formal ionic charges are used. Fractional charge models with a small Si-O bond strength (30 × 10 -12 ergs/bond) improve the agreement with experimental data. However, further improvement of the ionic model should include reducing the Si-O bond strength to values in better agreement with published estimates (7 × 10 - 12 to 13 × 10 -12 ergs/bond). By using additional information to constrain the parameterization of the ionic model, such as estimated bond strengths and static properties of the silica polymorphs, a model

  9. 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.

  10. Onset of simple liquid behaviour in modified water models

    NASA Astrophysics Data System (ADS)

    Prasad, Saurav; Chakravarty, Charusita

    2014-04-01

    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.

  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. Characterization and Modeling of a Water-based Liquid Scintillator

    SciTech Connect

    L. J. Bignell; Beznosko, D.; Diwan, M. V.; Hans, S.; Jaffe, D. E.; S. Kettell; Rosero, R.; Themann, H. W.; Viren, B.; Worcester, E.; Yeh, M.; Zhang, C.

    2015-12-15

    We 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 210 MeV, 475 MeV, and 2 GeV and for two WbLS compositions. These 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 Cherenkov light on our measurements. These results are relevant to the suitability of WbLS materials for next generation intensity frontier experiments.

  13. Atomistic simulations of liquid water using Lekner electrostatics

    NASA Astrophysics Data System (ADS)

    English, Niall J.; MacElroy, J. M. D.

    Equilibrium molecular dynamics simulations have been performed for liquid water using three different potential models in the NVT and NPT ensembles. The flexible SPC model, the rigid TIP4P model and the rigid/polarizable TIP4P-FQ potential were studied. The Lekner method was used to handle long range electrostatic interactions, and an efficient trivariate cubic spline interpolation method was devised for this purpose. A partitioning of the electrostatic interactions into medium and long range parts was performed, and the concomitant use of multiple timestep techniques led to substantially enhanced computation speeds. The simulations were carried out using 256 molecules in the NVT ensemble at 25°C and 997kgm-3 and in the NPT ensemble at 25°C and 1 bar. Various dynamic, structural, dielectric, rotational and thermodynamic properties were calculated, and it was found that the simulation methodologies performed satisfactorily vis-à-vis previous simulation results and experimental observations.

  14. 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.

  15. 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.

  16. Cloud Liquid Water, Mean Droplet Radius and Number Density Measurements Using a Raman Lidar

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Melfi, S. Harvey

    1999-01-01

    A new technique for measuring cloud liquid water, mean droplet radius and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid micro-spheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested.

  17. 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

  18. Photoinduced charge recombination in dipolar D-A-A photonic liquid crystal polymorphs.

    PubMed

    Mazza, Mercedes M A; Yamazaki, Shiori; Mai, Dieu X; Padgaonkar, Suyog; Peurifoy, Samuel; Goncalves, Ariane; Wu, Yi-Lin; Hu, Qiaoyu; Scott, Amy M

    2017-02-08

    A hexylalkoxy dipolar D-A-A molecule [7-(4-N,N-(bis(4-hexyloxyphenyl)amino)phenyl)-2,1,3-(benzothia-diazol-4-yl)methylene]propane-dinitrile, (C6-TPA-BT-CN) has been synthesized and the photophysics studied via femtosecond transient absorption spectroscopy (FsTA) in toluene and in amorphous and liquid crystalline spherulite thin films. Two spherulite macromolecular crystalline phases (banded, and non-banded) were observed through concentration dependent, solution processing techniques and are birefringent with a negative sign of elongation. A dramatic change in the electronic absorption from blue in amorphous films to green in spherulites was observed, and the molecular orientation was determined through the combined analysis of polarized light microscopy, X-ray diffraction, and scanning electron microscopy. FsTA was performed on amorphous films and show complex charge recombination dynamics, and a Stark effect, characterized from the combined TPA+˙ and [BT-CN]-˙ spectroscopic signatures at 450 nm and 510 nm and identified through spectroelectrochemistry. Radical cation dynamics of TPA+˙ was observed selectively at 750 nm with >503.3 ps (18%) recombination kinetics resulting in a rather significant yield of free charge carriers in amorphous films and consistent with previous reports on energetically disordered blend films. However, photoexcitation on large, non-banded spherulites areas (>250 μm) reveal average monoexponential charge recombination lifetimes of 169.2 ps from delocalized states similar to those observed in amorphous films and are 5× longer-lived than previous reports [Chang et al., J. Am. Chem. Soc., 2013, 135, 8790] of a related methyl-DPAT-BT-CN whose amorphous thin films were prepared through vapor deposition. Thus, the correlation between the microstructure of the blend film and the photoinduced radical pair dynamics described here is critical for developing a fundamental understanding of how dipolar states contribute to the charge carrier

  19. Stabilization of lamellar oil-water liquid crystals by surfactant/ co-surfactant monolayers

    NASA Astrophysics Data System (ADS)

    Braganza, L. F.; Dubois, M.; Tabony, J.

    1989-03-01

    LIQUID crystals are divided into two main classes, thermotropic and lyotropic. Thermotropic liquid crystals are formed by melting, whereas lyotropic liquid crystals arise from the association of molecules, such as soap and water, that in general are not in themselves liquid crystalline. Thermotropic liquid crystals are used for liquid-crystal displays; lyotropic liquid crystals occur in living cells. Here we report a novel sequence of lyotropic liquid crystals comprising alternate layers of oil and water whose thickness varies linearly with the relative proportions of oil and water, and we have determined their structure using neutron diffraction methods. The oil and water layers are separated and stabilized by a monolayer film of surfactant and co-surfactant. The individual layers are typically a hundred ångströms or more in thickness, and total lamellar spacings of up to 1,000 Å were observed. This behaviour is difficult to describe in terms of the theories of colloid stability currently used to describe lyotropic liquid crystals. An understanding of the self-organization of such systems over such large distances would elucidate how long-range liquid-crystalline ordering arises in living cells. Moreover, thermotropic liquid crystals are expensive and chemically relatively unstable, and lamellar mesophases of the lyotopic type described here could lead to inexpensive, chemically stable liquid-crystalline materials suitable for industrial application.

  20. Relationship between optical extinction and liquid water content in fogs

    NASA Astrophysics Data System (ADS)

    Klein, C.; Dabas, A.

    2013-11-01

    Studies carried out in the late 1970s suggest a simple linear relationship exists in practice between the optical extinction in the thermal IR and the liquid water content (LWC) in fogs. Such a relationship opens the possibility to monitor the vertical profile of the LWC in fogs with a rather simple backscatter lidar. Little is known on how the LWC varies as a function of height and during the fog life cycle, so the new measurement technique would help understand fog physics and provide valuable data for improving the quality of fog forecasts. In the present article, the validity of the linear relationship is revisited at the light of recent observations of fog droplet size distributions measured with a combination of sensors covering a large range of droplet radii. In particular, large droplets (radius above 15 μm) are detected, which was not the case in the late 1970s. The results confirm the linear relationship still holds, at least for the mostly radiative fogs observed during the campaign. The impact of the precise value of the real and imaginary parts of the refractive index on the coefficient of the linear relationship is also studied. The usual practice considers droplets are made of pure water. This assumption is probably valid for big droplets, it may be questioned for small ones since droplets are formed from condensation nuclei of highly variable chemical composition. The study suggests the relationship is mostly sensitive to the real part of the refractive index and the sensitivity grows with the size of fog droplets. However, large fog droplets are more likely to have an index close to that of water since they are mainly composed of water.

  1. 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.

  2. Why does hydronium diffuse faster than hydroxide in liquid water?

    NASA Astrophysics Data System (ADS)

    Zheng, Lixin; Santra, Biswajit; Distasio, Robert; Klein, Michael; Car, Roberto; Wu, Xifan

    Experiments show that the hydronium ion (H3O+) diffuses much faster than the hydroxide ion (OH-) in liquid water. ab initio molecular dynamics (AIMD) simulations correctly associated the diffusion mechanism to proton transfer (PT) but have been unable so far to clearly identify the reason for the faster diffusion of hydronium compared to hydroxide, as the diffusion rate was found to depend sensitively on the adopted functional approximation. We carried out AIMD simulations of the solvated water ions using a van der Waals (vdW) inclusive PBE0 hybrid density functional. It is found that not only hydronium diffuses faster than hydroxide but also the absolute rates agree with experiment. The fast diffusion of H3O+ occurs via concerted PT that enables the ion to jump across several H-bonded molecules in successful transfer events; in contrast, such concerted motion is significantly hindered in OH- where the ion is easily trapped in a hyper-coordination configuration (a local solvation structure that forbids PT). As a result multiple PT events are rare and the diffusion of OH- is significantly slowed down. Such a clear difference between the two ions results from the combined effect of vdW interactions and self-interaction correction. Doe SciDac: DE-SC0008626 and DE-SC0008726.

  3. Direct Raman evidence for a weak continuous phase transition in liquid water.

    PubMed

    Alphonse, Natalie K; Dillon, Stephanie R; Dougherty, Ralph C; Galligan, Dawn K; Howard, Louis N

    2006-06-22

    This paper presents the Raman depolarization ratio of degassed ultrapure water as a function of temperature, in the range 303.4-314.4 K (30.2-41.2 degrees C). The pressure of the sample was the vapor pressure of water at the measurement temperature. The data provide a direct indication of the existence of a phase transition in the liquid at 307.7 K, 5.8 kPa (34.6 degrees C, 0.057 atm). The minimum in the heat capacity, C(p)(), of water occurs at 34.5 degrees C, 1.0 atm (J. Res. Natl. Bur. Stand. 1939, 23, 197(1)). The minimum in C(p)() is shallow, and the transition is a weak-continuous phase transition. The pressure coefficient of the viscosity of water changes sign as pressure increases for temperatures below 35 degrees C (Nature 1965, 207, 620(2)). The viscosity minimum tracks the liquid phase transition in the P, T plane where it connects with the minimum in the freezing point of pure water in the same plane (Proc. Am. Acad. Arts Sci. 1911-12, 47, 441(3)). Previously we argued (J. Chem. Phys. 1998, 109, 7379(4)) that the minimum in the pressure coefficient of viscosity signaled the elimination of three-dimensional connectivity in liquid water. These observations coupled with recent measurements of the coordination shell of water near 300 K (Science 2004, 304, 995(5)) suggest that the structural component that changes during the phase transition is tetrahedrally coordinated water. At temperatures above the transition, there is no tetrahedrally coordinated water in the liquid and locally planar water structures dominate the liquid structure. Water is a structured liquid with distinct local structures that vary with temperature. Furthermore, liquid water has a liquid-liquid phase transition near the middle of the normal liquid range.

  4. Lake morphometry and resource polymorphism determine niche segregation between cool- and cold-water-adapted fish.

    PubMed

    Hayden, Brian; Harrod, Chris; Kahilaineni, Kimmo K

    2014-02-01

    Climate change is increasing ambient temperatures in Arctic and subarctic regions, facilitating latitudinal range expansions of freshwater fishes adapted to warmer water temperatures. The relative roles of resource availability and interspecific interactions between resident and invading species in determining the outcomes of such expansions has not been adequately evaluated. Ecological interactions between a cool-water adapted fish, the perch (Perca fluviatilis), and the cold-water adapted European whitefish (Coregonus lavaretus), were studied in both shallow and deep lakes with fish communities dominated by (1) monomorphic whitefish, (2) monomorphic whitefish and perch, and (3) polymorphic whitefish and perch. A combination of stomach content, stable-isotope, and invertebrate prey availability data were used to identify resource use and niche overlap among perch, the trophic generalist large sparsely rakered (LSR) whitefish morph, and the pelagic specialist densely rakered (DR) whitefish morph in 10 subarctic lakes at the contemporary distribution limit of perch in northern Scandinavia. Perch utilized its putative preferred littoral niche in all lakes. LSR whitefish utilized both littoral and pelagic resources in monomorphic whitefish-dominated lakes. When found in sympatry with perch, LSR whitefish exclusively utilized pelagic prey in deep lakes, but displayed niche overlap with perch in shallow littoral lakes. DR whitefish was a specialist zooplanktivore, relegating LSR whitefish from pelagic habitats, leading to an increase in niche overlap between LSR whitefish and perch in deep lakes. Our results highlight how resource availability (lake depth and fish community) governs ecological interactions between native and invading species, leading to different outcomes even at the same latitudes. These findings suggest that lake morphometry and fish community structure data should be included in bioclimate envelope-based models of species distribution shifts

  5. Isobaric vapor-liquid equilibria for methanol + ethanol + water and the three constituent binary systems

    SciTech Connect

    Kurihara, Kiyofumi; Nakamichi, Mikiyoshi; Kojima, Kazuo . Dept. of Industrial Chemistry)

    1993-07-01

    Vapor-liquid equilibrium data for methanol + ethanol + water and its three constituent binary systems methanol + ethanol, ethanol + water, and methanol + water were measured at 101.3 kPa using a liquid-vapor ebullition-type equilibrium still. The experimental binary data were correlated by the NRTL equation. The ternary system methanol + ethanol + water was predicted by means of the binary NRTL parameters with good accuracy.

  6. Investigation of the Extinguishing Features for Liquid Fuels and Organic Flammable Liquids Atomized by a Water Flow

    NASA Astrophysics Data System (ADS)

    Voytkov, Ivan V.; Zabelin, Maksim V.; Vysokomornaya, Olga V.

    2016-02-01

    The processes of heat and mass transfer were investigated experimentally while moving and evaporating the atomized water flow in high-temperature combustion products of typical liquid fuels and organic flammable liquids: gasoline, kerosene, acetone, crude oil, industrial alcohol. We determined typical periods of liquid extinguishing by an atomized water flow of various dispersability. Data of the discharge of extinguishing medium corresponding to various parameters of atomization and duration of using the atomization devices was presented. It is shown that Um≈3.5 m/s is a minimal outflow velocity of droplets during moving while passing the distance of 1m in the high-temperature gas medium to stop the combustion of organic liquids.

  7. 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...

  8. 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.

  9. 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.

  10. Development of an ionic liquid based dispersive liquid-liquid microextraction method for the analysis of polycyclic aromatic hydrocarbons in water samples.

    PubMed

    Pena, M Teresa; Casais, M Carmen; Mejuto, M Carmen; Cela, Rafael

    2009-09-04

    A simple, rapid and efficient method, ionic liquid based dispersive liquid-liquid microextraction (IL-DLLME), has been developed for the first time for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in water samples. The chemical affinity between the ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate) and the analytes permits the extraction of the PAHs from the sample matrix also allowing their preconcentration. Thus, this technique combines extraction and concentration of the analytes into one step and avoids using toxic chlorinated solvents. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, type and volume of disperser solvent, extraction time, dispersion stage, centrifuging time and ionic strength, were optimised. Analysis of extracts was performed by high performance liquid chromatography (HPLC) coupled with fluorescence detection (Flu). The optimised method exhibited a good precision level with relative standard deviation values between 1.2% and 5.7%. Quantification limits obtained for all of these considered compounds (between 0.1 and 7 ng L(-1)) were well below the limits recommended in the EU. The extraction yields for the different compounds obtained by IL-DLLME, ranged from 90.3% to 103.8%. Furthermore, high enrichment factors (301-346) were also achieved. The extraction efficiency of the optimised method is compared with that achieved by liquid-liquid extraction. Finally, the proposed method was successfully applied to the analysis of PAHs in real water samples (tap, bottled, fountain, well, river, rainwater, treated and raw wastewater).

  11. Angle-resolved photoemission spectroscopy of liquid water at 29.5 eV

    PubMed Central

    Nishitani, Junichi; West, Christopher W.; Suzuki, Toshinori

    2017-01-01

    Angle-resolved photoemission spectroscopy of liquid water was performed using extreme ultraviolet radiation at 29.5 eV and a time-of-flight photoelectron spectrometer. SiC/Mg coated mirrors were employed to select the single-order 19th harmonic from laser high harmonics, which provided a constant photon flux for different laser polarizations. The instrument was tested by measuring photoemission anisotropy for rare gases and water molecules and applied to a microjet of an aqueous NaI solution. The solute concentration was adjusted to eliminate an electric field gradient around the microjet. The observed photoelectron spectra were analyzed considering contributions from liquid water, water vapor, and an isotropic background. The anisotropy parameters of the valence bands (1b1, 3a1, and 1b2) of liquid water are considerably smaller than those of gaseous water, which is primarily attributed to electron scattering in liquid water.

  12. Water quantitatively induces the mucoadhesion of liquid crystalline phases of glyceryl monooleate.

    PubMed

    Lee, J; Young, S A; Kellaway, I W

    2001-05-01

    The possible role of water in the mucoadhesion phenomenon exhibited by the liquid crystalline phases of glyceryl monooleate was investigated using an in-vitro tensile strength technique. The mucoadhesion of the liquid crystalline phases of glyceryl monooleate was found to occur following uptake of water. The mucoadhesive force of the cubic phase was consistent since it is not capable of taking up additional water. An increase in pre-load period greatly facilitated the mucoadhesion of glyceryl monooleate (0% w/w initial water content), suggesting that the mucoadhesion is dependent upon the extent of the dehydration of the substrate. A good linear relationship between initial water content of the liquid crystalline phases and mucoadhesive force led to the conclusion that the mucoadhesive force increased with decreasing initial water concentration. Rheological properties of the liquid crystalline phases were also studied to allow a correlation between physical changes and mucoadhesion of the liquid crystalline phases, revealing that higher water concentrations in the liquid crystalline phases led to a more ordered structure that showed less mucoadhesion. The results of this study indicated that the mucoadhesive force of the liquid crystalline phases of glyceryl monooleate is determined by the capability to take up water from a water-rich environment. It may, therefore, be advantageous to use the lamellar phase as a buccal drug carrier as opposed to the relatively less mucoadhesive cubic phase.

  13. Automated dynamic liquid-liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection for the determination of phenoxy acid herbicides in environmental waters.

    PubMed

    Wu, Jingming; Ee, Kim Huey; Lee, Hian Kee

    2005-08-05

    Automated dynamic liquid-liquid-liquid microextraction (D-LLLME) controlled by a programmable syringe pump and combined with HPLC-UV was investigated for the extraction and determination of 5 phenoxy acid herbicides in aqueous samples. In the extraction procedure, the acceptor phase was repeatedly withdrawn into and discharged from the hollow fiber by the syringe pump. The repetitive movement of acceptor phase into and out of the hollow fiber channel facilitated the transfer of analytes into donor phase, from the organic phase held in the pore of the fiber. Parameters such as the organic solvent, concentrations of the donor and acceptor phases, plunger movement pattern, speed of agitation and ionic strength of donor phase were evaluated. Good linearity of analytes was achieved in the range of 0.5-500 ng/ml with coefficients of determination, r2 > 0.9994. Good repeatabilities of extraction performance were obtained with relative standard deviations lower than 7.5%. The method provided up-to 490-fold enrichment within 13 min. In addition, the limits of detection (LODs) ranged from 0.1 to 0.4 ng/mL (S/N = 3). D-LLLME was successfully applied for the analysis of phenoxy acid herbicides from real environmental water samples.

  14. Studies of liquid water by computer simulations. V. Equation of state of fluid water with Carravetta-Clementi potential

    NASA Astrophysics Data System (ADS)

    Kataoka, Yosuke

    1987-07-01

    The pressure of liquid water at normal density is obtained by molecular dynamics simulations based on four intermolecular potential functions derived from quantum chemical calculations of the water dimer; Matsuoka-Clementi-Yoshimine, Carravetta-Clementi, Clementi-Habitz, Yoon-Morokuma-Davidson. Among them, the Carravetta-Clementi potential gives the most reasonable temperature-dependence of pressure, although the absolute value is large compared with the experimental one. The fluid state is surveyed over a wide range of temperature and density with the Carravetta-Clementi potential. The equation of state of fluid water is determined by a least-square fitting of the calculated energies and pressures at 347 state points. The anomalous properties of liquid water observed experimentally are nonempirically reproduced on a semiquantitative level. The calculated equation of state of liquid water is consistent with the Speedy-Angell conjecture on the limit of stability of the liquid phase.

  15. Probing the interactions between ionic liquids and water: experimental and quantum chemical approach.

    PubMed

    Khan, Imran; Kurnia, Kiki A; Mutelet, Fabrice; Pinho, Simão P; Coutinho, João A P

    2014-02-20

    For an adequate choice or design of ionic liquids, the knowledge of their interaction with other solutes and solvents is an essential feature for predicting the reactivity and selectivity of systems involving these compounds. In this work, the activity coefficient of water in several imidazolium-based ionic liquids with the common cation 1-butyl-3-methylimidazolium was measured at 298.2 K. To contribute to a deeper insight into the interaction between ionic liquids and water, COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies. The results showed good agreement between experimental and predicted activity coefficient of water in ionic liquids and that the interaction of water and ionic liquids was strongly influenced by the hydrogen bonding of the anion with water. Accordingly, the intensity of interaction of the anions with water can be ranked as the following: [CF3SO3](-) < [SCN](-) < [TFA](-) < Br(-) < [TOS](-) < Cl(-) < [CH3SO3](-) [DMP](-) < [Ac](-). In addition, fluorination and aromatization of anions are shown to reduce their interaction with water. The effect of temperature on the activity coefficient of water at infinite dilution was measured by inverse gas chromatography and predicted by COSMO-RS. Further analysis based on COSMO-RS provided information on the nature of hydrogen bonding between water and anion as well as the possibility of anion-water complex formation.

  16. Evaporation of Ethanol-Water Binary Mixture Sessile Liquid Marbles.

    PubMed

    Ooi, Chin Hong; Bormashenko, Edward; Nguyen, Anh V; Evans, Geoffrey M; Dao, Dzung V; Nguyen, Nam-Trung

    2016-06-21

    Liquid marble is a liquid droplet coated with particles. Recently, the evaporation process of a sessile liquid marble using geometric measurements has attracted great attention from the research community. However, the lack of gravimetric measurement limits further insights into the physical changes of a liquid marble during the evaporation process. Moreover, the evaporation process of a marble containing a liquid binary mixture has not been reported before. The present paper investigates the effective density and the effective surface tension of an evaporating liquid marble that contains aqueous ethanol at relatively low concentrations. The effective density of an evaporating liquid marble is determined from the concurrent measurement of instantaneous mass and volume. Density measurements combined with surface profile fitting provide the effective surface tension of the marble. We found that the density and surface tension of an evaporating marble are significantly affected by the particle coating.

  17. UBXN1 polymorphism and its expression in porcine M. longissimus dorsi are associated with water holding capacity.

    PubMed

    Loan, Huynh Thi Phuong; Muráni, Eduard; Maak, Steffen; Ponsuksili, Siriluck; Wimmers, Klaus

    2014-03-01

    The UBX domain containing protein 1-like gene (UBXN1) promotes the protein degradation that affects meat quality, in particular traits related to water holding capacity. The aim of our study was to identify UBXN1 polymorphisms and to analyse their association with meat quality traits. Moreover, the relationship of UBXN1 polymorphisms and its transcript abundance as well as the link between UBXN1 expression and water holding capacity were addressed. Pigs of the breed German landrace (GL) and the commercial crossbreed of Pietrain × [German large white × GL] (PiF1) were used for this study. In GL, the novel SNP c.355 C > T showed significant association with conductivity and drip loss (P ≤ 0.05). Another SNP at nt 674 of the coding sequence [SNP c.674C>T (p.Thr225Ile)] was associated with drip loss (P ≤ 0.05) and pH1 (P ≤ 0.1). In PiF1, the SNP UBXN1 c.674C>T was associated with conductivity (P ≤ 0.01). Moreover, the haplotype combinations showed effects on conductivity within both commercial populations at P ≤ 0.1. In both populations, high expression of UBXN1 tended to decrease water holding capacity in the early post mortem period. The analysis of triangular relationship of UBXN1 polymorphism, transcript abundance, and water holding capacity evidences the existence of a causal polymorphism in cis-regulatory regions of UBXN1 that influences its expression.

  18. Analysis of aromatic amines in water samples by liquid-liquid-liquid microextraction with hollow fibers and high-performance liquid chromatography.

    PubMed

    Zhao, Limian; Zhu, Lingyan; Lee, Hian Kee

    2002-07-19

    Liquid-liquid-liquid microextraction (LLLME) with hollow fibers in high-performance liquid chromatography (HPLC) has been applied as a rapid and sensitive quantitative method for the detection of four aromatic amines (3-nitroaniline, 4-chloroaniline, 4-bromoaniline and 3,4-dichloroaniline) in environmental water samples. The preconcentration procedure was induced by the pH difference inside and outside the hollow fiber. The target compounds were extracted from 4-ml aqueous sample (donor solution, pH approximately 13) through a microfilm of organic solvent (di-n-hexyl ether), immobilized in the pores of a hollow fiber (1.5 cm length x 0.6 mm I.D.), and finally into 4 microl of acid acceptor solution inside the fiber. After a prescribed period of time, the acceptor solution inside the fiber was withdrawn into the microsyringe and directly injected into the HPLC system for analysis. Factors relevant to the extraction procedure were studied. Up to 500-fold enrichment of analytes could be obtained under the optimized conditions (donor solution: 0.1 M sodium hydroxide solution with 20% sodium chloride and 2% acetone; organic phase: di-n-hexyl ether; acceptor solution: 0.5 M hydrochloric acid and 500 mM 18-crown-6 ether; extraction time of 30 min; stirring at 1,000 rev./min). The procedure also served as a sample clean-up step. The influence of humic acid on the extraction efficiency was also investigated, and more than 85% relative recoveries of the analytes at two different concentrations (20 and 100 microg/l) were achieved at various concentration of humic acid. This technique is a low cost, simple and fast approach to the analysis of polar compounds in aqueous samples.

  19. Liquid Water from First Principles: Validation of Different Sampling Approaches

    SciTech Connect

    Mundy, C J; Kuo, W; Siepmann, J; McGrath, M J; Vondevondele, J; Sprik, M; Hutter, J; Parrinello, M; Mohamed, F; Krack, M; Chen, B; Klein, M

    2004-05-20

    A series of first principles molecular dynamics and Monte Carlo simulations were carried out for liquid water to assess the validity and reproducibility of different sampling approaches. These simulations include Car-Parrinello molecular dynamics simulations using the program CPMD with different values of the fictitious electron mass in the microcanonical and canonical ensembles, Born-Oppenheimer molecular dynamics using the programs CPMD and CP2K in the microcanonical ensemble, and Metropolis Monte Carlo using CP2K in the canonical ensemble. With the exception of one simulation for 128 water molecules, all other simulations were carried out for systems consisting of 64 molecules. It is found that the structural and thermodynamic properties of these simulations are in excellent agreement with each other as long as adiabatic sampling is maintained in the Car-Parrinello molecular dynamics simulations either by choosing a sufficiently small fictitious mass in the microcanonical ensemble or by Nos{acute e}-Hoover thermostats in the canonical ensemble. Using the Becke-Lee-Yang-Parr exchange and correlation energy functionals and norm-conserving Troullier-Martins or Goedecker-Teter-Hutter pseudopotentials, simulations at a fixed density of 1.0 g/cm{sup 3} and a temperature close to 315 K yield a height of the first peak in the oxygen-oxygen radial distribution function of about 3.0, a classical constant-volume heat capacity of about 70 J K{sup -1} mol{sup -1}, and a self-diffusion constant of about 0.1 Angstroms{sup 2}/ps.

  20. 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.

  1. Electrochemical anomalies of protic ionic liquid - Water systems: A case study using ethylammonium nitrate - Water system

    NASA Astrophysics Data System (ADS)

    Abe, Hiroshi; Nakama, Kazuya; Hayashi, Ryotaro; Aono, Masami; Takekiyo, Takahiro; Yoshimura, Yukihiro; Saihara, Koji; Shimizu, Akio

    2016-08-01

    Electrochemical impedance spectroscopy was used to evaluate protic ionic liquid (pIL)-water mixtures in the temperature range of -35-25 °C. The pIL used in this study was ethylammonium nitrate (EAN). At room temperature, the resonant mode of conductivity was observed in the high frequency region. The anomalous conductivity disappeared once solidification occurred at low temperatures. The kinetic pH of the EAN-water system was investigated at a fixed temperature. Rhythmic pH oscillations in the EAN-H2O mixtures were induced at 70 < x < 90 mol% H2O. The electrochemical instabilities in a EAN-water mixture are caused in an intermediate state between pIL and bulk water. From the ab initio calculations, it was observed that the dipole moment of the EAN-water complex shows a discrete jump at around 85 mol% H2O. Water-mediated hydrogen bonding network drastically changes at the crossover concentration.

  2. 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 μg/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 μg/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%.

  3. Electrodeposition of Si from an Ionic Liquid Bath at Room Temperature in the Presence of Water.

    PubMed

    Shah, Nisarg K; Pati, Ranjan Kumar; Ray, Abhijit; Mukhopadhyay, Indrajit

    2017-02-21

    The electrochemical deposition of Si has been carried out in an ionic liquid medium in the presence of water in a limited dry nitrogen environment on highly oriented pyrolytic graphite (HOPG) at room temperature. It has been found that the presence of water in ionic liquids does not affect the available effective potential window to a large extent. Silicon has been successfully deposited electrochemically in the overpotential regime in two different ionic liquids, namely, BMImTf2N and BMImPF6, in the presence of water. Although a Si thin film has been obtained from BMImTf2N; only distinguished Si crystals protected in ionic liquid droplets have been observed from BMImPF6. The most important observation of the present investigation is that the Si precursor, SiCl4, instead of undergoing hydrolysis, even in the presence of water, coexisted with ionic liquids, and elemental Si has been successfully electrodeposited.

  4. Vortex-assisted liquid-liquid microextraction for the rapid screening of short-chain chlorinated paraffins in water.

    PubMed

    Chang, Chia-Yu; Chung, Wu-Hsun; Ding, Wang-Hsien

    2016-01-01

    The rapid screening of trace levels of short-chain chlorinated paraffins in various aqueous samples was performed by a simple and reliable procedure based on vortex-assisted liquid-liquid microextraction combined with gas chromatography and electron capture negative ionization mass spectrometry. The optimal vortex-assisted liquid-liquid microextraction conditions for 20 mL water sample were as follows: extractant 400 μL of dichloromethane; vortex extraction time of 1 min at 2500 × g; centrifugation of 3 min at 5000 × g; and no ionic strength adjustment. Under the optimum conditions, the limit of quantitation was 0.05 μg/L. Precision, as indicated by relative standard deviations, was less than 9% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was above 91%. The vortex-assisted liquid-liquid microextraction with gas chromatography and electron capture negative ionization mass spectrometry method was successfully applied to quantitatively extract short-chain chlorinated paraffins from samples of river water and the effluent of a wastewater treatment plant, and the concentrations ranged from 0.8 to 1.6 μg/L.

  5. 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.

  6. 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.

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

    PubMed

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

    2007-10-14

    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.

  8. Revisiting a many-body model for water based on a single polarizable site: from gas phase clusters to liquid and air/liquid water systems.

    PubMed

    Réal, Florent; Vallet, Valérie; Flament, Jean-Pierre; Masella, Michel

    2013-09-21

    We present a revised version of the water many-body model TCPE [M. Masella and J.-P. Flament, J. Chem. Phys. 107, 9105 (1997)], which is based on a static three charge sites and a single polarizable site to model the molecular electrostatic properties of water, and on an anisotropic short range many-body energy term specially designed to accurately model hydrogen bonding in water. The parameters of the revised model, denoted TCPE/2013, are here developed to reproduce the ab initio energetic and geometrical properties of small water clusters (up to hexamers) and the repulsive water interactions occurring in cation first hydration shells. The model parameters have also been refined to reproduce two liquid water properties at ambient conditions, the density and the vaporization enthalpy. Thanks to its computational efficiency, the new model range of applicability was validated by performing simulations of liquid water over a wide range of temperatures and pressures, as well as by investigating water liquid/vapor interfaces over a large range of temperatures. It is shown to reproduce several important water properties at an accurate enough level of precision, such as the existence liquid water density maxima up to a pressure of 1000 atm, the water boiling temperature, the properties of the water critical point (temperature, pressure, and density), and the existence of a "singularity" temperature at about 225 K in the supercooled regime. This model appears thus to be particularly well-suited for characterizing ion hydration properties under different temperature and pressure conditions, as well as in different phases and interfaces.

  9. Revisiting a many-body model for water based on a single polarizable site: From gas phase clusters to liquid and air/liquid water systems

    NASA Astrophysics Data System (ADS)

    Réal, Florent; Vallet, Valérie; Flament, Jean-Pierre; Masella, Michel

    2013-09-01

    We present a revised version of the water many-body model TCPE [M. Masella and J.-P. Flament, J. Chem. Phys. 107, 9105 (1997)], which is based on a static three charge sites and a single polarizable site to model the molecular electrostatic properties of water, and on an anisotropic short range many-body energy term specially designed to accurately model hydrogen bonding in water. The parameters of the revised model, denoted TCPE/2013, are here developed to reproduce the ab initio energetic and geometrical properties of small water clusters (up to hexamers) and the repulsive water interactions occurring in cation first hydration shells. The model parameters have also been refined to reproduce two liquid water properties at ambient conditions, the density and the vaporization enthalpy. Thanks to its computational efficiency, the new model range of applicability was validated by performing simulations of liquid water over a wide range of temperatures and pressures, as well as by investigating water liquid/vapor interfaces over a large range of temperatures. It is shown to reproduce several important water properties at an accurate enough level of precision, such as the existence liquid water density maxima up to a pressure of 1000 atm, the water boiling temperature, the properties of the water critical point (temperature, pressure, and density), and the existence of a "singularity" temperature at about 225 K in the supercooled regime. This model appears thus to be particularly well-suited for characterizing ion hydration properties under different temperature and pressure conditions, as well as in different phases and interfaces.

  10. 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

  11. 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.

  12. The structure of graphene oxide membranes in liquid water, ethanol and water-ethanol mixtures.

    PubMed

    Talyzin, Alexandr V; Hausmaninger, Tomas; You, Shujie; Szabó, Tamás

    2014-01-07

    The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of "negative thermal expansion" and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes.

  13. Another glimpse over the salting-out assisted liquid-liquid extraction in acetonitrile/water mixtures.

    PubMed

    Valente, Inês Maria; Gonçalves, Luís Moreira; Rodrigues, José António

    2013-09-20

    The use of the salting-out effect in analytical chemistry is very diverse and can be applied to increase the volatility of the analytes in headspace extractions, to cause the precipitation of proteins in biological samples or to improve the recoveries in liquid-liquid extractions. In the latter, the salting-out process can be used to create a phase separation between water-miscible organic solvents and water. Salting-out assisted liquid-liquid extraction (SALLE) is an advantageous sample preparation technique aiming HPLC-UV analysis when developing analytical methodologies. In fact, some new extraction methodologies like QuEChERS include the SALLE concept. This manuscript discusses another point of view over SALLE with particular emphasis over acetonitrile-water mixtures for HPLC-UV analysis; the influence of the salting-out agents, their concentration and the water-acetonitrile volume ratios were the studied parameters. α-dicarbonyl compounds and beer were used as test analytes and test samples, respectively. The influence of the studied parameters was characterized by the obtained phase separation volume ratio and the fraction of α-dicarbonyls extracted to the acetonitrile phase. Results allowed the distribution of salts within three groups according to the phase separation and their extractability: (1) chlorides and acetates, (2) carbonates and sulfates and (3) magnesium sulfate; of all tested salts, sodium chloride had the highest influence on the α-dicarbonyls fraction extracted.

  14. Temperature dependence of local solubility of hydrophobic molecules in the liquid-vapor interface of water.

    PubMed

    Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

    2014-11-14

    One important aspect of the hydrophobic effect is that solubility of small, nonpolar molecules in liquid water decreases with increasing temperature. We investigate here how the characteristic temperature dependence in liquid water persists or changes in the vicinity of the liquid-vapor interface. From the molecular dynamics simulation and the test-particle insertion method, the local solubility Σ of methane in the liquid-vapor interface of water as well as Σ of nonpolar solutes in the interface of simple liquids are calculated as a function of the distance z from the interface. We then examine the temperature dependence of Σ under two conditions: variation of Σ at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of Σ at fixed z depends on the position z and the system, whereas Σ at fixed local density decreases with increasing temperature for all the model solutions at any fixed density between vapor and liquid phases. The monotonic decrease of Σ under the fixed-density condition in the liquid-vapor interface is in accord with what we know for the solubility of nonpolar molecules in bulk liquid water under the fixed-volume condition but it is much robust since the solvent density to be fixed can be anything between the coexisting vapor and liquid phases. A unique feature found in the water interface is that there is a minimum in the local solubility profile Σ(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of Σ grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of Σ is due to the layering structure of the free interface of water.

  15. Determination of pyrazon residues in water by reversed phase high performance liquid chromatography.

    PubMed

    Ahmad, I

    1982-01-01

    A simple analytical method is described for the quantitative determination of pyrazon residues in water. It involves high performance liquid chromatography with ultraviolet detection at 270 nm. The procedure is used to determine 2 ppb to 1 ppm levels of pyrazon in water. The traditional liquid-liquid extraction method has been replaced by an adsorption-trapping method for the extraction of pyrazon. Average recovery of pyrazon from the laboratory spiked samples was 98.1%. The method can be used for water samples with concentrations as low as 2 ppb.

  16. Solvated water molecules and hydrogen-bridged networks in liquid water

    NASA Astrophysics Data System (ADS)

    Corongiu, Giorgina; Clementi, Enrico

    1993-02-01

    We have analyzed the molecular-dynamics (MD) trajectories for the oxygen and hydrogen atoms of liquid water, at six temperatures (from hot, T=361 K, to supercooled water, T=242 K); in the MD simulations the Nieser-Corongiu-Clementi ab initio potential has been used, since it yields reliable x-ray and neutron-diffraction data as well as infrared, Raman, and neutron-scattering spectra. Our analysis leads to two complementary models where we can consider each water as a solvated molecule (placed at the center of a solvation shell) or as a component of a cyclic polymer, a substructure of the hydrogen-bonded network. In the first solvation shell all water molecules are solvated with coordination values in the range 2-8. The most probable solvation number is four, at low temperature, and five at high temperature considering oxygen-oxygen pairs; however, the coordination number is four at all the temperatures if we consider oxygen-hydrogen pairs. The lifetime of the tetra coordinated complexes is the largest one and increases as temperature decreases. The computed population of cyclic polymers is highest for the pentameters in the studied temperature range, the second most probable cyclic structure is for hexamers. The average O-O distances in the liquid are temperature dependent and shorter than those in the gas phase, approaching ice values at low temperature (except for cyclic trimers, for which the O-O distance is nearly temperature independent). As a preliminary result, the lifetime of the polygons is estimated to be around 0.01 ps.

  17. Isotope effects in liquid water by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2002-03-01

    The light and heavy liquid water (H2O-D2O) mixtures in the 0-1 molar fraction were studied in the mid-infrared by Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Five principal factors were retrieved by factor analysis (FA). When D2O is mixed with H2O, the HDO formed because of the hopping nature of the proton (H or D) results in three types of molecules in equilibrium. Because of the nearest-neighbor interactions, the three molecules give rise to nine species. Some of the species evolve concomitantly with other species giving the five principal factors observed. We present the spectra of these factors with their abundances. The calculated probability of the species present at different molar fractions which when the concomitant species are combined gives the observed abundances. To appreciate clearly the difference between the principal spectra, a Gaussian simulation of the bands was made. Because of the numerous components that make up the stretch bands, they are not very sensitive to changes in composition of the solutions; nevertheless, they do indicate the presence of new entities other than the pure species. The deformation bands, more sensitive to such changes than the stretch bands, clearly indicate the presence of the three types of molecules as well as of intermediate species. These bands are sensitive to the two hydrogen bonds on the oxygen atom that a reference molecule makes with its nearest-neighbors, but not to the hydrogen bonds that the nearest-neighbors make with the next nearest neighbors.

  18. Using nanoscale amorphous solid water films to create and study deeply supercooled liquid water at interfaces

    NASA Astrophysics Data System (ADS)

    Kay, Bruce

    Molecular beam vapor deposition of water on cryogenic substrates is known to produce amorphous solid films. When heated above their glass transition these films transform into deeply supercooled liquid water. These nanoscale liquid films can be used to study kinetic processes such as diffusion, isotope exchange, crystallization, and solvent mediated reactions in unprecedented detail. This talk will highlight our recent advances in this area. My colleagues Yuntao Xu, Chunqing Yuan, Collin Dibble, R. Scott Smith, Nick Petrik, and Greg Kimmel made important contributions to this work.This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The research was performed using EMSL, a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by Battelle, operated for the U.S. DOE under Contract DE-AC05-76RL01830.

  19. Libration induced stretching mode excitation for pump-probe spectroscopy in pure liquid water.

    PubMed

    Amir, Wafa; Gallot, Guilhem; Hache, François

    2004-10-22

    We developed an experimental approach to study pure liquid water in the infrared and avoid thermal effects. This technique is based on libration induced stretching excitation of water molecules. A direct correspondence between frequencies within the libration and OH stretching bands is demonstrated. Energy diffusion is studied in pure liquid water by measuring wave packet dynamics of OH stretching vibrator with infrared femtosecond spectroscopy. Wave packet dynamics reveals ultrafast energy dynamics and reflects 130 fs intermolecular energy transfer between water vibrators. Energy diffusion is almost two orders of magnitude faster than self diffusion in water.

  20. Column atmospheric water vapor and vegetation liquid water retrievals from Airborne Imaging Spectrometer data

    NASA Astrophysics Data System (ADS)

    Gao, Bo-Cai; Goetz, Alexander F. H.

    1990-03-01

    simultaneously because the band centers of liquid water in vegetation and the atmospheric water vapor are offset by approximately 0.05 μm.

  1. Primitive Liquid Water of the Solar System in an Aqueous Altered Carbonaceous Chondrite

    NASA Technical Reports Server (NTRS)

    Tsuchiyama, A.; Miyake, A.; Kitayama, A.; Matsuno, J.; Takeuchi, A.; Uesugi, K.; Suzuki, Y.; Nakano, T.; Zolensky, M. E.

    2016-01-01

    Non-destructive 3D observations of the aqueous altered CM chondrite Sutter's Mill using scanning imaging x-ray microscopy (SIXM) showed that some of calcite and enstatite grains contain two-phase inclusion, which is most probably composed of liquid water and bubbles. This water should be primitive water responsible for aqueous alteration in an asteroid in the early solar system.

  2. Molecular-dynamics simulation of liquid water with an ab initio flexible water-water interaction potential

    NASA Astrophysics Data System (ADS)

    Lie, G. C.; Clementi, E.

    1986-04-01

    The Matsuoka-Clementi-Yoshimine (MCY) configuration interaction potential for rigid water-water interactions has been extended to include the intramolecular vibrations. The extended potential (MCYL), using no empirical parameters other than the atomic masses, electron charge, and Planck constant, is used in a molecular-dynamics simulation study of the static and dynamic properties of liquid water. Among the properties studied are internal energy, heat capacity, pressure, radial distribution functions, dielectric constant, static structure factor, velocity autocorrelation functions, self-diffusion coefficients, dipole autocorrelation function, and density and current fluctuations. Comparison with experiments is made whenever possible. Most of these properties are found to improve slightly relative to the MCY model. The simulated high-frequency sound mode seems to support the results and interpretation of a recent coherent inelastic neutron scattering experiment.

  3. Hydrocarbon contamination increases the liquid water content of frozen Antarctic soils.

    PubMed

    Siciliano, Steven D; Schafer, Alexis N; Forgeron, Michelle A M; Snape, Ian

    2008-11-15

    We do not yet understand why fuel spills can cause greater damage in polar soils than in temperate soils. The role of water in the freezing environment may partly be responsible for why polar soils are more sensitive to pollution. We hypothesized that hydrocarbons alter the liquid water in frozen soil, and we evaluated this hypothesis by conducting laboratory and field experiments at Casey Station, Antarctica. Liquid water content in frozen soils (theta(liquid)) was estimated by time domain reflectometry in laboratory, field collected soils, and in situ field measurements. Our results demonstrate an increase in liquid water associated with hydrocarbon contamination in frozen soils. The dependence of theta(liquid) on aged fuel and spiked fuel were almost identical,with a slope of 2.6 x 10(-6) mg TPH (total petroleum hydrocarbons) kg(-1) for aged fuel and 3.1 x 10(-6) mg TPH kg(-1) for spiked fuel. In situ measurements found theta(liquid) depends, r2 = 0.75, on fuel for silt loam soils (theta(liquid) = 0.094 + 7.8 x 10(-6) mg TPH kg(-1)) but not on fuel for silt clay loam soils. In our study, theta(liquid) doubled in field soils and quadrupled in laboratory soils contaminated with diesel which may have profound implications on frost heave models in contaminated soils.

  4. 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.

  5. Widom line and the liquid-liquid critical point for the TIP4P/2005 water model.

    PubMed

    Abascal, José L F; Vega, Carlos

    2010-12-21

    The Widom line and the liquid-liquid critical point of water in the deeply supercooled region are investigated via computer simulation of the TIP4P/2005 model. The Widom line has been calculated as the locus of compressibility maxima. It is quite close to the experimental homogeneous nucleation line and, in the region studied, it is almost parallel to the curve of temperatures of maximum density at fixed pressure. The critical temperature is determined by examining which isotherm has a region with flat slope. An interpolation in the Widom line gives the rest of the critical parameters. The computed critical parameters are T(c)=193 K, p(c)=1350 bar, and ρ(c)=1.012 g/cm(3). Given the performance of the model for the anomalous properties of water and for the properties of ice phases, the calculated critical parameters are probably close to those of real water.

  6. Tailored ionic liquid-based surfactants for the formation of microemulsions with water and a hydrophobic ionic liquid.

    PubMed

    Porada, Jan H; Zauser, Diana; Feucht, Birgit; Stubenrauch, Cosima

    2016-08-14

    Microemulsions (μe) with water and a hydrophobic ionic liquid (IL) usually require 45-60 wt% surfactant to solubilize equal amounts of water and IL. To increase the efficiency we designed a new class of surfactants by combining a hydrophilic but IL-ophobic carbohydrate-based part with a hydrophobic but IL-ophilic IL-based part. These surfactants allow formulating microemulsions with 20 wt% surfactant only which opens up a new arena for efficient water-IL μes.

  7. 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

    2015-10-27

    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, T(g) . Here we report a universal water-content, X(aqu) , dependence of T(g) for aqueous solutions. Solutions with X(aqu)>X(cr)(aqu)vitrify/devitrify at a constant temperature, ~T(g) , referring to freeze-concentrated phase with X(aqu)left behind ice crystallization. Those solutions with X(aqu)liquid II phase of water'. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.

  8. 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.

  9. IDENTIFICATION OF POLAR DRINKING WATER DISINFECTION BY-PRODUCTS USING LIQUID CHROMATOGRAPHY - MASS SPECTROMETRY

    EPA Science Inventory

    A qualitative method using 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by analysis with liquid chromatography (LC)/negative ion-electrospray mass spectrometry (MS) was developed for identifying polar aldehydes and ketones in ozonated drinking water. This method offe...

  10. Process for hydrogen isotope concentration between liquid water and hydrogen gas

    DOEpatents

    Stevens, William H.

    1976-09-21

    A process for hydrogen isotope exchange and concentration between liquid water and hydrogen gas, wherein liquid water and hydrogen gas are contacted, in an exchange section, with one another and with at least one catalyst body comprising at least one metal selected from Group VIII of the Periodic Table and preferably a support therefor, the catalyst body has a liquid-water-repellent, gas permeable polymer or organic resin coating, preferably a fluorinated olefin polymer or silicone coating, so that the isotope concentration takes place by two simultaneously occurring steps, namely, ##EQU1## WHILE THE HYDROGEN GAS FED TO THE EXCHANGE SECTION IS DERIVED IN A REACTOR VESSEL FROM LIQUID WATER THAT HAS PASSED THROUGH THE EXCHANGE SECTION.

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

    SciTech Connect

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

    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.

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

    PubMed

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

    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.

  13. 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.

  14. 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.

  15. Ice or liquid water in the Martian regolith. Morphologic indicators from rampart craters

    NASA Technical Reports Server (NTRS)

    Mouginismark, P. J.

    1987-01-01

    The morphology of ejecta blankets around certain Martian craters carries implications for volatiles in either the Martian crust or the atmosphere or both. The evidence that rampart crater ejecta can be used to infer the physical condition of volatiles in target rocks at the time of impact is reviewed. It was concluded that ice, and not liquid water, was the main volatile state, although rare examples also suggest the presence of liquid water at the time the craters were formed.

  16. Response to ``Comment on `Isotope effects in liquid water by infrared spectroscopy. IV. No free OH groups in liquid water''' [J. Chem. Phys. 135, 117101 (2011)

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2011-09-01

    The original infrared spectra in the OH stretch region that Riemenschneider and Ludwig (thereafter, RL) have obtained for pure water and aqueous salt solutions are very similar to what we have previously reported [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 6803 (2001)]. In our 2010 paper, we claimed that "free" OH is not present in pure liquid water. The difference spectra from the salt solutions and pure water spectrum give small negative components situated near 3655 cm-1. Because this position is in the range where free OH groups should absorb RL assigned the negative peaks to free OH removed from pure water. That is, RL consider that pure liquid water contains free OH groups which are removed in the salt solutions. Obviously, the removal of all free OH present in pure water will produce maximum negative intensities in the difference spectra. In this response, we present unpublished difference spectra between several salt solutions and pure water where negative peaks are higher than that claimed by RL for pure water. Since this is impossible it demonstrates that the assignment proposed by RL to free OH is incorrect. The negative peaks come from the difference between large components that differ a little between salt solutions and pure water [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 6803 (2001)]. Recall that the ionized salts do not absorb but perturb the surrounding water molecules.

  17. 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

    2015-10-14

    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.

  18. Combustion characteristics of nanoaluminum, liquid water, and hydrogen peroxide mixtures

    SciTech Connect

    Sabourin, J.L.; Yetter, R.A.; Risha, G.A.; Son, S.F.; Tappan, B.C.

    2008-08-15

    An experimental investigation of the combustion characteristics of nanoaluminum (nAl), liquid water (H{sub 2}O{sub (l)}), and hydrogen peroxide (H{sub 2}O{sub 2}) mixtures has been conducted. Linear and mass-burning rates as functions of pressure, equivalence ratio ({phi}), and concentration of H{sub 2}O{sub 2} in H{sub 2}O{sub (l)} oxidizing solution are reported. Steady-state burning rates were obtained at room temperature using a windowed pressure vessel over an initial pressure range of 0.24 to 12.4 MPa in argon, using average nAl particle diameters of 38 nm, {phi} from 0.5 to 1.3, and H{sub 2}O{sub 2} concentrations between 0 and 32% by mass. At a nominal pressure of 3.65 MPa, under stoichiometric conditions, mass-burning rates per unit area ranged between 6.93 g/cm{sup 2} s (0% H{sub 2}O{sub 2}) and 37.04 g/cm{sup 2} s (32% H{sub 2}O{sub 2}), which corresponded to linear burning rates of 9.58 and 58.2 cm/s, respectively. Burning rate pressure exponents of 0.44 and 0.38 were found for stoichiometric mixtures at room temperature containing 10 and 25% H{sub 2}O{sub 2}, respectively, up to 5 MPa. Burning rates are reduced above {proportional_to}5 MPa due to the pressurization of interstitial spaces of the packed reactant mixture with argon gas, diluting the fuel and oxidizer mixture. Mass burning rates were not measured above {proportional_to}32% H{sub 2}O{sub 2} due to an anomalous burning phenomena, which caused overpressurization within the quartz sample holder, leading to tube rupture. High-speed imaging displayed fingering or jetting ahead of the normal flame front. Localized pressure measurements were taken along the sample length, determining that the combustion process proceeded as a normal deflagration prior to tube rupture, without significant pressure buildup within the tube. In addition to burning rates, chemical efficiencies of the combustion reaction were determined to be within approximately 10% of the theoretical maximum under all conditions

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

    DOEpatents

    Shepodd, Timothy J.

    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.

  20. Polymorphisms in maternal folate pathway genes interact with arsenic in drinking water to influence risk of myelomeningocele

    PubMed Central

    Mazumdar, Maitreyi; Valeri, Linda; Rodrigues, Ema G.; Hasan, Md Omar Sharif Ibne; Hamid, Rezina; Paul, Ligi; Selhub, Jacob; Silva, Fareesa; Mostofa, MdGolam; Quamruzzaman, Quazi; Rahman, Mahmuder; Christiani, David C.

    2015-01-01

    Background Arsenic induces neural tube defects in many animal models. Additionally, studies have shown that mice with specific genetic defects in folate metabolism and transport are more susceptible to arsenic-induced neural tube defects. We sought to determine whether 14 single-nucleotide polymorphisms in genes involved in folate metabolism modified the effect of exposure to drinking water contaminated with inorganic arsenic and posterior neural tube defect (myelomeningocele) risk. Methods Fifty-four mothers of children with myelomeningocele and 55 controls were enrolled through clinical sites in rural Bangladesh in a case-control study of the association between environmental arsenic exposure and risk of myelomeningocele. We assessed participants for level of myelomeningocele, administered questionnaires, conducted biological and environmental sample collection, and performed genotyping. Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure inorganic arsenic concentration in drinking water. Candidate single-nucleotide polymorphisms were identified through review of the literature. Results Drinking water inorganic arsenic concentration was associated with increased risk of myelomeningocele for participants with 4 of the 14 studied single-nucleotide polymorphisms in genes involved in folate metabolism: the AA/AG genotype of rs2236225 (MTHFD1), the GG genotype of rs1051266 (SLC19A1), the TT genotype of rs7560488 (DNMT3A), and the GG genotype of rs3740393 (AS3MT) with adjusted OR of 1.13, 1.31, 1.20, and 1.25 for rs2236225, rs1051266, rs7560488, and rs3740393, respectively. Conclusions Our results support the hypothesis that environmental arsenic exposure increases the risk of myelomeningocele via interaction with folate metabolic pathways. PMID:26250961

  1. Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

    DOE PAGES

    Wang, Zhe; Kolesnikov, Alexander I.; Ito, Kanae; ...

    2015-12-03

    We studied the boson peak in deeply cooled water confined in nanopores in order to examine the liquid-liquid transition (LLT). Below ~180 K, the boson peaks at pressures P higher than ~3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. Moreover, these phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. Additionally,more » the P dependence of the librational band also agrees with the above conclusion.« less

  2. Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

    SciTech Connect

    Wang, Zhe; Kolesnikov, Alexander I.; Ito, Kanae; Podlesnyak, Andrey; Chen, Sow-Hsin

    2015-12-03

    We studied the boson peak in deeply cooled water confined in nanopores in order to examine the liquid-liquid transition (LLT). Below ~180 K, the boson peaks at pressures P higher than ~3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. Moreover, these phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. Additionally, the P dependence of the librational band also agrees with the above conclusion.

  3. Determination of organochlorine pesticides in snow water samples by low density solvent based dispersive liquid-liquid microextraction.

    PubMed

    Zhao, Wenting; Li, Jindong; Wu, Tong; Wang, Peng; Zhou, Zhiqiang

    2014-09-01

    A simple, rapid, efficient, and environmentally friendly pretreatment based on a low-density solvent based dispersive liquid-liquid microextraction was developed for determining trace levels of 17 organochlorine pesticides in snow. The parameters affecting the extraction efficiency, such as the type and volume of the extraction and dispersive solvents, extraction time, and salt content, were optimized. The optimized conditions yielded a good performance, with enrichment factors ranging from 271 to 474 and recoveries ranging from 71.4 to 114.5% and relative standard deviations between 1.6 and 14.8%. The detection limits, calculated as three times the signal-to-noise ratio, ranged from 0.02 to 0.11 μg/L. The validated method was used to successfully analyze 17 analytes in snow water samples, overcoming the drawbacks of some existing low-density solvent liquid microextraction methods, which require special devices, large volumes of organic solvents, or complicated operation procedures.

  4. Detection of the liquid-liquid transition in the deeply cooled water confined in MCM-41 with elastic neutron scattering technique

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Ito, Kanae; Chen, Sow-Hsin

    2016-05-01

    In this paper we present a review on our recent experimental investigations into the phase behavior of the deeply cooled water confined in a nanoporous silica material, MCM-41, with elastic neutron scattering technique. Under such strong confinement, the homogeneous nucleation process of water is avoided, which allows the confined water to keep its liquid state at temperatures and pressures that are inaccessible to the bulk water. By measuring the average density of the confined heavy water, we observe a likely first-order low-density liquid (LDL) to high-density liquid (HDL) transition in the deeply cooled region of the confined heavy water. The phase separation starts from 1.12±0.17{ kbar} and 215±1{ K} and extends to higher pressures and lower temperatures in the phase diagram. This starting point could be the liquid-liquid critical point of the confined water. The locus of the Widom line is also estimated. The observation of the liquid-liquid transition in the confined water has potential to explain the mysterious behaviors of water at low temperatures. In addition, it may also have impacts on other disciplines, because the confined water system represents many biological and geological systems in which water resides in nanoscopic pores or in the vicinity of hydrophilic or hydrophobic surfaces.

  5. Liquid water content and precipitation characteristics of stratiform clouds as inferred from satellite microwave measurements

    SciTech Connect

    Curry, J.A. ); Ardell, C.D. ); Tian, Lin )

    1990-09-20

    In this paper the authors present an analysis of the integrated liquid water content and precipitation characteristics of stratiform clouds using data from the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) for January 1979, over the North Atlantic Ocean (40{degree}-60{degree}N). Concurrent analysis of the SMMR data with the US Air Force 3-Dimensional Nephanalysis (3DNEPH) allows the interpretation of the SMMR-derived liquid water paths and precipitation characteristics in terms of cloud type, cloud fraction, and cloud height. Combining the initialized analyses from the European Center for Medium-Range Weather Forecasting with the 3DNEPH enables vertical temperature and humidity profiles to be incorporated into the retrievals. The interpretation and presentation of results are guided by their implications for the parameterization of liquid water content of layer clouds in large-scale atmospheric models. The average liquid water paths for middle and low clouds were determined to be 115 and 102 g m{sup {minus}2}, respectively, with a maximum value of 1,070 g m{sup {minus}2}. Analysis of the liquid water path as a function of temperature showed that clouds with average temperature below 246 K had little liquid water and were inferred to be predominantly crystalline. Liquid water paths of 350 g m{sup {minus}2} and 500 g m{sup {minus}2} for middle and low clouds, respectively, were determined to be average thresholds for the onset of precipitation. Maximum rain rates for these clouds were determined to be 7 mm h{sup {minus}1}. The autoconversion of cloud water to rain water was determined to occur at a rate of 0.001 s{sup {minus}1}.

  6. Experimentally probing the libration of interfacial water: the rotational potential of water is stiffer at the air/water interface than in bulk liquid.

    PubMed

    Tong, Yujin; Kampfrath, Tobias; Campen, R Kramer

    2016-07-21

    Most properties of liquid water are determined by its hydrogen-bond network. Because forming an aqueous interface requires termination of this network, one might expect the molecular level properties of interfacial water to markedly differ from water in bulk. Intriguingly, much prior experimental and theoretical work has found that, from the perspective of their time-averaged structure and picosecond structural dynamics, hydrogen-bonded OH groups at an air/water interface behave the same as hydrogen-bonded OH groups in bulk liquid water. Here we report the first experimental observation of interfacial water's libration (i.e. frustrated rotation) using the laser-based technique vibrational sum frequency spectroscopy. We find this mode has a frequency of 834 cm(-1), ≈165 cm(-1) higher than in bulk liquid water at the same temperature and similar to bulk ice. Because libration frequency is proportional to the stiffness of water's rotational potential, this increase suggests that one effect of terminating bulk water's hydrogen bonding network at the air/water interface is retarding rotation of water around intact hydrogen bonds. Because in bulk liquid water the libration plays a key role in stabilizing reaction intermediates and dissipating excess vibrational energy, we expect the ability to probe this mode in interfacial water to open new perspectives on the kinetics of heterogeneous reactions at aqueous interfaces.

  7. 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.

  8. 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.

  9. 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.

  10. Molecular dynamics simulation of the behaviour of water in nano-confined ionic liquid-water mixtures

    NASA Astrophysics Data System (ADS)

    Docampo-Álvarez, B.; Gómez-González, V.; Montes-Campos, H.; Otero-Mato, J. M.; Méndez-Morales, T.; Cabeza, O.; Gallego, L. J.; Lynden-Bell, R. M.; Ivaništšev, V. B.; Fedorov, M. V.; Varela, L. M.

    2016-11-01

    This work describes the behaviour of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid under nanoconfinement, between graphene sheets. By means of molecular dynamics simulations, the adsorption of water molecules at the graphene surface is studied. A depletion of water molecules in the vicinity of the neutral and negatively charged graphene surfaces, and their adsorption at the positively charged surface are observed in line with the preferential hydration of the ionic liquid anions. The findings are appropriately described using a two-level statistical model. The confinement effect on the structure and dynamics of the mixtures is thoroughly analyzed using the density and the potential of mean force profiles, as well as by the vibrational densities of the states of water molecules near the graphene surface. The orientation of water molecules and the water-induced structural transitions in the layer closest to the graphene surface are also discussed.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Two-Phase Model of Liquid-Liquid Interactions With Interface Capturing: Application to Water Assisted Injection Molding

    NASA Astrophysics Data System (ADS)

    Silva, Luisa; Lanrivain, Rodolphe; Zerguine, Walid; Rodriguez-Villa, Andrès; Coupez, Thierry

    2007-05-01

    In this paper, a two phase model to compute liquid-liquid flows is presented. We consider that one phase is a highly viscous thermodependent liquid (polymer phase), whereas the second one is a low viscosity low temperature fluid (water). The first part of this paper concerns capture of the interface between the water and the polymer (or determination of the phase field function). Classical VOF and Level set techniques have been implemented and were ameliorated using mesh adaptation techniques. To accurately determine the velocity field, a two-phase formulation is considered, based in the theory of mixtures, and we introduce a scalar parameter, the phase fraction quantifying the presence of each phase in each point of the computational domain. A friction type coupling between both phases is retained. Using the mixed finite element method within an eulerian framework, we calculate in a single system the whole kinematic variables for both liquids (velocity and pressure of each phase). Results are shown, for 2D and 3D parts.

  16. Can liquid water profiles be retrieved from passive microwave zenith observations?

    NASA Astrophysics Data System (ADS)

    Crewell, Susanne; Ebell, Kerstin; Löhnert, Ulrich; Turner, D. D.

    2009-03-01

    The ability to determine the cloud boundaries and vertical distribution of cloud liquid water for single-layer liquid clouds using zenith-pointing microwave radiometers is investigated. Simulations are used to demonstrate that there is little skill in determining either cloud base or cloud thickness, especially when the cloud thickness is less than 500 m. It is also shown that the different distributions of liquid water content within a cloud with known cloud boundaries results in a maximum change in the brightness temperature of less than 1 K at the surface from 20 to 150 GHz, which is on the order of the instrument noise level. Furthermore, it is demonstrated using the averaging kernel that the number of degrees of freedom for signal (i.e., independent pieces of information) is approximately 1, which implies there is no information on vertical distribution of liquid water in the microwave observations.

  17. 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.

  18. Determination of 5-Bromo-2’-Deoxyuridine (BrdU) in Well Water by High Performance Liquid Chromatography (HPLC)

    DTIC Science & Technology

    1992-09-01

    HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC...Securrty Classification) Determination of 5-Bromo-2’-Deoxyuridine (BrdU) in Well Water by High Performance Liquid Chromatography (hPLC) 12. PERSONAL...PLOT OF BrdU STABILITY VERSUS TIME ....................... 10 ii DETERMINATION OF 5-BROMO-2’-DEOXY-URIDINE (BrdU) IN WELL WATER BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

  19. 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.

  20. Synergistic conversion of glucose into 5-hydroxymethylfurfural in ionic liquid-water mixtures.

    PubMed

    Qi, Xinhua; Watanabe, Masaru; Aida, Taku M; Smith, Richard L

    2012-04-01

    A method for converting glucose into 5-hydroxymethylfurfural (5-HMF) without using chromium-containing catalysts was developed. The method uses ionic liquid-water mixtures with a ZrO(2) catalyst. Addition of a certain amount of water (10-50 wt.%) into the 1,3-dialkylimidazolium chloride ionic liquid promoted the formation of 5-HMF from glucose compared with that in either pure water or in the pure ionic liquid. A 5-HMF yield of 53% was obtained within 10 min at 200 °C in a 50:50 w/w% 1-hexyl-3-methyl imidazolium chloride-water mixture in the presence of ZrO(2). The 1,3-dialkylimidazolium ionic liquids having Cl(-) or HSO(4)(-) anions were effective for promoting 5-HMF formation. Addition of protic solvents such as methanol and ethanol to the ionic liquid had a similar synergistic effect as water and promoted fructose and 5-HMF formation. The results reported in this work can be extended to other fields, where the ratio of ionic liquid and protic solvent can be adjusted to promote the desired reactions.

  1. A Convolution Algorithm of Differential Coefficients of liquid water Based on Vibrational Raman Scattering

    NASA Astrophysics Data System (ADS)

    Han, Dong; Chen, Liangfu; Tao, Jinhua; Su, Lin; Li, Shenshen; Yu, Chao; Yan, Huanhuan

    Inelastic Vibrational Raman Scattering (VRS) by liquid water is one significant limitation to the accuracy of the retrieval of trace gas constituents in atmosphere over waters, particularly over clear ocean waters, while using satellite data with Differential Optical Absorption Spec-troscopy technique (DOAS).The effect which is similar to the Ring effect in atmosphere results in the filling in of Fraunhofer lines, which is known as solar absorption lines. The inelastic component of the liquid water scattering causes a net increase of radiance in the line because more radiation is shifted to the wavelength of an absorption line than shifted from this wave-length to other wavelengths. The spectrum at the top of the atmosphere over land measured by OMI (Ozone Monitoring Instrument)/AURA is convolved with Vibrational Raman Scat-tering coefficients of liquid water, divided by the original measured spectrum, with a cubic polynomial subtracted off, to create differential water Ring spectrum. The OMI spectrum over land is chosen to avoid the effect of VRS by liquid water. This method has been suggested in order to obtain an effective differential water Ring coeffients for the DOAS fitting process.The differential water Ring spectrum could be used to improve the accuracy of the retrieval of the trace gases concentration. The method is not relying on RTM, which would be time-consuming and depending on lot of parameters. Therefore, it is very fast and convenient.

  2. 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.

  3. Effect of water presence on choline chloride-2urea ionic liquid and coating platings from the hydrated ionic liquid

    PubMed Central

    Du, Cuiling; Zhao, Binyuan; Chen, Xiao-Bo; Birbilis, Nick; Yang, Haiyan

    2016-01-01

    In the present study, hygroscopicity of the choline chloride-urea (ChCl-2Urea) ionic liquid (IL) was confirmed through Karl-Fisher titration examination, indicating that the water content in the hydrated ChCl-2Urea IL was exposure-time dependent and could be tailored by simple heating treatment. The impact of the absorbed water on the properties of ChCl-2Urea IL, including viscosity, electrical conductivity, electrochemical window and chemical structure was investigated. The results show that water was able to dramatically reduce the viscosity and improve the conductivity, however, a broad electrochemical window could be persisted when the water content was below ~6 wt.%. These characteristics were beneficial for producing dense and compact coatings. Nickel (Ni) coatings plating from hydrated ChCl-2Urea IL, which was selected as an example to show the effect of water on the electroplating, displayed that a compact and corrosion-resistant Ni coating was plated from ChCl-2Urea IL containing 6 wt.% water doped with 400 mg/L NA at a moderate temperature. As verified by FTIR analysis, the intrinsic reason could be ascribed that water was likely linked with urea through strong hydrogen bond so that the water decomposition was suppressed during plating. Present study may provide a reference to prepare some similar water-stable ILs for plating. PMID:27381851

  4. Effect of water presence on choline chloride-2urea ionic liquid and coating platings from the hydrated ionic liquid.

    PubMed

    Du, Cuiling; Zhao, Binyuan; Chen, Xiao-Bo; Birbilis, Nick; Yang, Haiyan

    2016-07-06

    In the present study, hygroscopicity of the choline chloride-urea (ChCl-2Urea) ionic liquid (IL) was confirmed through Karl-Fisher titration examination, indicating that the water content in the hydrated ChCl-2Urea IL was exposure-time dependent and could be tailored by simple heating treatment. The impact of the absorbed water on the properties of ChCl-2Urea IL, including viscosity, electrical conductivity, electrochemical window and chemical structure was investigated. The results show that water was able to dramatically reduce the viscosity and improve the conductivity, however, a broad electrochemical window could be persisted when the water content was below ~6 wt.%. These characteristics were beneficial for producing dense and compact coatings. Nickel (Ni) coatings plating from hydrated ChCl-2Urea IL, which was selected as an example to show the effect of water on the electroplating, displayed that a compact and corrosion-resistant Ni coating was plated from ChCl-2Urea IL containing 6 wt.% water doped with 400 mg/L NA at a moderate temperature. As verified by FTIR analysis, the intrinsic reason could be ascribed that water was likely linked with urea through strong hydrogen bond so that the water decomposition was suppressed during plating. Present study may provide a reference to prepare some similar water-stable ILs for plating.

  5. Effect of water presence on choline chloride-2urea ionic liquid and coating platings from the hydrated ionic liquid

    NASA Astrophysics Data System (ADS)

    Du, Cuiling; Zhao, Binyuan; Chen, Xiao-Bo; Birbilis, Nick; Yang, Haiyan

    2016-07-01

    In the present study, hygroscopicity of the choline chloride-urea (ChCl-2Urea) ionic liquid (IL) was confirmed through Karl-Fisher titration examination, indicating that the water content in the hydrated ChCl-2Urea IL was exposure-time dependent and could be tailored by simple heating treatment. The impact of the absorbed water on the properties of ChCl-2Urea IL, including viscosity, electrical conductivity, electrochemical window and chemical structure was investigated. The results show that water was able to dramatically reduce the viscosity and improve the conductivity, however, a broad electrochemical window could be persisted when the water content was below ~6 wt.%. These characteristics were beneficial for producing dense and compact coatings. Nickel (Ni) coatings plating from hydrated ChCl-2Urea IL, which was selected as an example to show the effect of water on the electroplating, displayed that a compact and corrosion-resistant Ni coating was plated from ChCl-2Urea IL containing 6 wt.% water doped with 400 mg/L NA at a moderate temperature. As verified by FTIR analysis, the intrinsic reason could be ascribed that water was likely linked with urea through strong hydrogen bond so that the water decomposition was suppressed during plating. Present study may provide a reference to prepare some similar water-stable ILs for plating.

  6. Liquid-like sorption water in the upper Martian surface - physical, chemical and possible biological consequences

    NASA Astrophysics Data System (ADS)

    Möhlmann, Diedrich T. F.

    2004-03-01

    Sorption water is a constituent of the soil of the upper meters of the Martian surface at mid- and low latitudes (Möhlmann, 2004). This water content can regionally reach values of about 16wt% (Feldman et al., 2003, Mitrofanov et al., 2003). Adsorption water, the physisorbed part of sorption water, can exist in a liquid-like state at temperatures down to -40°C and less. The terrestrial counterpart is the "unfrozen water" in permafrost (Anderson and Tice, 1972). It has partially modified physical, chemical and biological properties if compared to dry frozen soil. Liquid-like water can act as a solvent, and it supports transport processes to become effective. Chemical processes, which are triggered by adsorption water, are shown to be effective under Martian conditions. These processes are energetically driven by photons. Possibilities for a related photon driven bio-chemical Martian iron-carbon cycle are discussed.

  7. Use of magnetic effervescent tablet-assisted ionic liquid dispersive liquid-liquid microextraction to extract fungicides from environmental waters with the aid of experimental design methodology.

    PubMed

    Yang, Miyi; Wu, Xiaoling; Jia, Yuhan; Xi, Xuefei; Yang, Xiaoling; Lu, Runhua; Zhang, Sanbing; Gao, Haixiang; Zhou, Wenfeng

    2016-02-04

    In this work, a novel effervescence-assisted microextraction technique was proposed for the detection of four fungicides. This method combines ionic liquid-based dispersive liquid-liquid microextraction with the magnetic retrieval of the extractant. A magnetic effervescent tablet composed of Fe3O4 magnetic nanoparticles, sodium carbonate, sodium dihydrogen phosphate and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonimide) was used for extractant dispersion and retrieval. The main factors affecting the extraction efficiency were screened by a Plackett-Burman design and optimized by a central composite design. Under the optimum conditions, good linearity was obtained for all analytes in pure water model and real water samples. Just for the pure water, the recoveries were between 84.6% and 112.8%, the limits of detection were between 0.02 and 0.10 μg L(-1) and the intra-day precision and inter-day precision both are lower than 4.9%. This optimized method was successfully applied in the analysis of four fungicides (azoxystrobin, triazolone, cyprodinil, trifloxystrobin) in environmental water samples and the recoveries ranged between 70.7% and 105%. The procedure promising to be a time-saving, environmentally friendly, and efficient field sampling technique.

  8. 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

  9. Ionic liquid-based dispersive liquid-liquid microextraction and enhanced spectrophotometric determination of molybdenum (VI) in water and plant leaves samples by FO-LADS.

    PubMed

    Gharehbaghi, Maysam; Shemirani, Farzaneh

    2011-02-01

    A new simple and rapid ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) has been applied to preconcentrate trace levels of molybdenum (VI) as a prior step to its enhanced determination by fiber optic-linear array detection spectrophotometry (FO-LADS). In this method, a small amount of [Hmim][Tf(2)N] (1-hexyl-3-methylimmidazolium bis (trifluormethylsulfonyl) imid) as an extraction solvent was applied to extract molybdenum - pyrogallol red complex, which was formed in an aqueous solution in the presence of N-cetyl-N-N-N-trimethyl ammonium chloride as a sensitizing agent. Under optimum conditions, enhancement factor, detection limit and relative standard deviation (n=5, for 30 μg L(-1) of molybdenum (VI)) in 10 mL water sample were 72.6, 1.43 μg L(-1) and 2.8%, respectively.

  10. Ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction combined with electrothermal atomic absorption spectrometry for a sensitive determination of cadmium in water samples

    NASA Astrophysics Data System (ADS)

    Li, Shengqing; Cai, Shun; Hu, Wei; Chen, Hao; Liu, Hanlan

    2009-07-01

    A new method was developed for the determination of cadmium in water samples using ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction (IL-based USA-DLLME) followed by electrothermal atomic absorption spectrometry (ETAAS). The IL-based USA-DLLME procedure is free of volatile organic solvents, and there is no need for a dispersive solvent, in contrast to conventional DLLME. The ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF 6), was quickly disrupted by an ultrasonic probe for 1 min and dispersed in water samples like a cloud. At this stage, a hydrophobic cadmium-DDTC complex was formed and extracted into the fine droplets of HMIMPF 6. After centrifugation, the concentration of the enriched cadmium in the sedimented phase was determined by ETAAS. Some effective parameters of the complex formation and microextraction, such as the concentration of the chelating agent, the pH, the volume of the extraction solvent, the extraction time, and the salt effect, have been optimized. Under optimal conditions, a high extraction efficiency and selectivity were reached for the extraction of 1.0 ng of cadmium in 10.0 mL of water solution employing 73 µL of HMIMPF 6 as the extraction solvent. The enrichment factor of the method is 67. The detection limit was 7.4 ng L - 1 , and the characteristic mass ( m0, 0.0044 absorbance) of the proposed method was 0.02 pg for cadmium (Cd). The relative standard deviation (RSD) for 11 replicates of 50 ng L - 1 Cd was 3.3%. The method was applied to the analysis of tap, well, river, and lake water samples and the Environmental Water Reference Material GSBZ 50009-88 (200921). The recoveries of spiked samples were in the range of 87.2-106%.

  11. Comparison of liquid-state anomalies in Stillinger-Weber models of water, silicon, and germanium

    NASA Astrophysics Data System (ADS)

    Dhabal, Debdas; Chakravarty, Charusita; Molinero, Valeria; Kashyap, Hemant K.

    2016-12-01

    We use molecular dynamics simulations to compare and contrast the liquid-state anomalies in the Stillinger-Weber models of monatomic water (mW), silicon (Si), and germanium (Ge) over a fairly wide range of temperatures and densities. The relationships between structure, entropy, and mobility, as well as the extent of the regions of anomalous behavior, are discussed as a function of the degree of tetrahedrality. We map out the cascade of density, structural, pair entropy, excess entropy, viscosity, and diffusivity anomalies for these three liquids. Among the three liquids studied here, only mW displays anomalies in the thermal conductivity, and this anomaly is evident only at very low temperatures. Diffusivity and viscosity, on the other hand, show pronounced anomalous regions for the three liquids. The temperature of maximum density of the three liquids shows re-entrant behavior consistent with either singularity-free or liquid-liquid critical point scenarios proposed to explain thermodynamic anomalies. The order-map, which shows the evolution of translational versus tetrahedral order in liquids, is different for Ge than for Si and mW. We find that although the monatomic water reproduces several thermodynamic and dynamic properties of rigid-body water models (e.g., SPC/E, TIP4P/2005), its sequence of anomalies follows, the same as Si and Ge, the silica-like hierarchy: the region of dynamic (diffusivity and viscosity) anomalies encloses the region of structural anomalies, which in turn encloses the region of density anomaly. The hierarchy of the anomalies based on excess entropy and Rosenfeld scaling, on the other hand, reverses the order of the structural and dynamic anomalies, i.e., predicts that the three Stillinger-Weber liquids follow a water-like hierarchy of anomalies. We investigate the scaling of diffusivity, viscosity, and thermal conductivity with the excess entropy of the liquid and find that for dynamical properties that present anomalies there is no

  12. Mixed reverse micelles facilitated downstream processing of lipase involving water-oil-water liquid emulsion membrane.

    PubMed

    Bhowal, Saibal; Priyanka, B S; Rastogi, Navin K

    2014-01-01

    Our earlier work for the first time demonstrated that liquid emulsion membrane (LEM) containing reverse micelles could be successfully used for the downstream processing of lipase from Aspergillus niger. In the present work, we have attempted to increase the extraction and purification fold of lipase by using mixed reverse micelles (MRM) consisting of cationic and nonionic surfactants in LEM. It was basically prepared by addition of the internal aqueous phase solution to the organic phase followed by the redispersion of the emulsion in the feed phase containing enzyme, which resulted in globules of water-oil-water (WOW) emulsion for the extraction of lipase. The optimum conditions for maximum lipase recovery (100%) and purification fold (17.0-fold) were CTAB concentration 0.075 M, Tween 80 concentration 0.012 M, at stirring speed of 500 rpm, contact time 15 min, internal aqueous phase pH 7, feed pH 9, KCl concentration 1 M, NaCl concentration 0.1 M, and ratio of membrane emulsion to feed volume 1:1. Incorporation of the nonionic surfactant (e.g., Tween 80) resulted in remarkable improvement in the purification fold (3.1-17.0) of the lipase. LEM containing a mixture of nonionic and cationic surfactants can be successfully used for the enhancement in the activity recovery and purification fold during downstream processing of enzymes/proteins.

  13. Structural, electronic and optical properties of Bi2O3 polymorphs by first-principles calculations for photocatalytic water splitting

    NASA Astrophysics Data System (ADS)

    Azhar, N. S.; Taib, M. F. M.; Hassan, O. H.; Yahya, M. Z. A.; Ali, A. M. M.

    2017-03-01

    Crystal structures of α-Bi2O3 and β-Bi2O3 were calculated using Cambridge serial total energy package (CASTEP) based on the first-principles plane-wave ultrasoft pseudopotential method within local density approximation (LDA) and generalized gradient approximation (GGA) together with Perdew–Burke–Ernzerhof (GGA-PBE) and Perdew–Burke–Ernzerhof revised for solid (GGA-PBEsol). The structural parameter of α-Bi2O3 and β-Bi2O3 are in good agreement with previous experimental and theoretical data. All of the polymorphs were calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms. Density of states exhibits hybridization of Bi 6s and O 2p orbitals and the calculated charge density profiles exhibit the ionic character in the chemical bonding of this compound. The narrowed band gap (E g) and red-shift of light absorption edge are responsible for the photocatalytic activity of Bi2O3 for water splitting application. The optical properties such as optical absorption and electron energy loss function were calculated to show the best structure among these polymorphs for the photocatalytic water splitting application.

  14. A new dispersive liquid-liquid microextraction using ionic liquid based microemulsion coupled with cloud point extraction for determination of copper in serum and water samples.

    PubMed

    Arain, Salma Aslam; Kazi, Tasneem Gul; Afridi, Hassan Imran; Arain, Mariam Shahzadi; Panhwar, Abdul Haleem; Khan, Naeemullah; Baig, Jameel Ahmed; Shah, Faheem

    2016-04-01

    A simple and rapid dispersive liquid-liquid microextraction procedure based on ionic liquid assisted microemulsion (IL-µE-DLLME) combined with cloud point extraction has been developed for preconcentration copper (Cu(2+)) in drinking water and serum samples of adolescent female hepatitits C (HCV) patients. In this method a ternary system was developed to form microemulsion (µE) by phase inversion method (PIM), using ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and nonionic surfactant, TX-100 (as a stabilizer in aqueous media). The Ionic liquid microemulsion (IL-µE) was evaluated through visual assessment, optical light microscope and spectrophotometrically. The Cu(2+) in real water and aqueous acid digested serum samples were complexed with 8-hydroxyquinoline (oxine) and extracted into IL-µE medium. The phase separation of stable IL-µE was carried out by the micellar cloud point extraction approach. The influence of of different parameters such as pH, oxine concentration, centrifugation time and rate were investigated. At optimized experimental conditions, the limit of detection and enhancement factor were found to be 0.132 µg/L and 70 respectively, with relative standard deviation <5%. In order to validate the developed method, certified reference materials (SLRS-4 Riverine water) and human serum (Sero-M10181) were analyzed. The resulting data indicated a non-significant difference in obtained and certified values of Cu(2+). The developed procedure was successfully applied for the preconcentration and determination of trace levels of Cu(2+) in environmental and biological samples.

  15. In-situ metathesis reaction combined with ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction method for the determination of phenylurea pesticides in water samples.

    PubMed

    Zhang, Jiaheng; Liang, Zhe; Li, Songqing; Li, Yubo; Peng, Bing; Zhou, Wenfeng; Gao, Haixiang

    2012-08-30

    A novel microextraction technique, named in-situ metathesis reaction, combined with ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction was developed for the determination of five phenylurea pesticides (i.e., diuron, diflubenzuron, teflubenzuron, flufenoxuron, and chlorfluazuron) in environmental water samples. In the developed method, 360 μL LiNTf(2) aqueous solution (0.162 g/mL) was added to the sample solution containing a small amount of [C(6)MIM]Cl (0.034 g) to form a water-immiscible ionic liquid, [C(6)MIM]NTf(2), as extraction solution. The mixed solutions were placed in an ultrasonic water bath at 150 W for 4min and centrifuged at 3500 rpm for 10 min to achieve phase separation. After centrifugation, fine droplets of the extractant phase settled to the bottom of the centrifuge tube and were directly injected into the high-performance liquid chromatography system for analysis. The quantity of [C(6)MIM]Cl, the molar ratio of [C(6)MIM]Cl and LiNTf(2), ionic strength, ultrasound time, and centrifugation time, were optimized using a Plackett-Burman design. Significant factors obtained were optimized by employing a central composite design. The optimized technique provides good repeatability (RSD 2.4 to 3.5%), linearity (0.5 μg/L to 500 μg/L), low LODs (0.06 μg/L to 0.08 μg/L) and great enrichment factor (244 to 268). The developed method can be applied in routine analysis for the determining of phenylurea pesticides in environmental samples.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Synergistic effect of dicarbollide anions in liquid-liquid extraction: a molecular dynamics study at the octanol-water interface.

    PubMed

    Chevrot, G; Schurhammer, R; Wipff, G

    2007-04-28

    We report a molecular dynamics study of chlorinated cobalt bis(dicarbollide) anions [(B(9)C(2)H(8)Cl(3))(2)Co](-)"CCD(-)" in octanol and at the octanol-water interface, with the main aim to understand why these hydrophobic species act as strong synergists in assisted liquid-liquid cation extraction. Neat octanol is quite heterogeneous and is found to display dual solvation properties, allowing to well solubilize CCD(-), Cs(+) salts in the form of diluted pairs or oligomers, without displaying aggregation. At the aqueous interface, octanol behaves as an amphiphile, forming either monolayers or bilayers, depending on the initial state and confinement conditions. In biphasic octanol-water systems, CCD(-) anions are found to mainly partition to the organic phase, thus attracting Cs(+) or even more hydrophilic counterions like Eu(3+) into that phase. The remaining CCD(-) anions adsorb at the interface, but are less surface active than at the chloroform interface. Finally, we compare the interfacial behavior of the Eu(BTP)(3)(3+) complex in the absence and in the presence of CCD(-) anions and extractant molecules. It is found that when the CCD(-)'s are concentrated enough, the complex is extracted to the octanol phase. Otherwise, it is trapped at the interface, attracted by water. These results are compared to those obtained with chloroform as organic phase and discussed in the context of synergistic effect of CCD(-) in liquid-liquid extraction, pointing to the importance of dual solvation properties of octanol and of the hydrophobic character of CCD(-) for synergistic extraction of cations.

  1. Stability of Liquid Water on a Land Planet: Wider Habitable Zone for a Less Water Planet than an Aqua Planet

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Abe-Ouchi, A.; Zahnle, K. J.

    2009-12-01

    Most of the previous studies on the habitable zone implicitly assume an ocean-covered 'aqua' planet that has a large amount of liquid water like the present Earth. However, there is a possibility of a habitable 'land' planet that is covered by vast dry desert but has locally abundant water. The land planet state is expected when the fraction of water covered areas is less than about half of surface. Ancient Mars might be in such a state. The conditions for the existence of liquid water can be different for a less water land planet from that of an aqua planet, because both the ice-albedo feedback, which causes the complete freezing, and the runaway greenhouse, which causes the complete evaporation, are enhanced by abundant water. Here, we investigated the condition for the solar flux that cause the complete freezing or evaporation of liquid water on a land planet using a general circulation model. We use a general circulation model, CCSR/NIES AGCM5.4g, which have been developed for the Earth’s climate modeling by the Centre for Climate System Research, University of Tokyo and the National Institute for Environmental Research. To compare a land planet with an aqua planet, we consider an Earth-sized planet without topography with 1 bar air atmosphere on a circular orbit. The distribution of water on a land planet is completely determined by the atmospheric circulation. On a land planet, complete freezing and complete evaporation of water occurred at the 77% and 170% of the present Earth's solar flux, respectively. On the other hand, complete freezing and evaporation of an aqua planet occurs at 90% and about 130%, respectively. Thus, a land planet shows stronger resistance to both the complete freezing and evaporation of liquid water than an aqua planet. The stability field of liquid water is quite wide on a land planet compared with that of an aqua planet. In addition, escape flux of water from a land planet is very small because of dry upper atmosphere. It suggests

  2. 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 μL of an acceptor phase at an optimal pH 2.02 of the donor phase (sample). The highest

  3. 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.

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

    DOE PAGES

    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

  5. Ionic liquid based dispersive liquid-liquid microextraction coupled with micro-solid phase extraction of antidepressant drugs from environmental water samples.

    PubMed

    Ge, Dandan; Lee, Hian Kee

    2013-11-22

    Ionic liquid-dispersive liquid-liquid microextraction combined with micro-solid phase extraction (IL-DLLME-μ-SPE), and high-performance liquid chromatography (HPLC) was developed for the determination of tricyclic antidepressants (TCAs) in water samples. Two hundred microliters of an organic solvent (as disperser solvent) and 20 μl of 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate were injected into a 5.0 ml sample for sonication-assisted DLLME. After this, a μ-SPE device, containing a novel material zeolite imidazolate framework 4 (ZIF-4), was added into the sample solution and 1 min of vortex-assisted extraction was performed. After 5 min of sonication-assisted desorption, 10 μl of desorption solvent was injected into a HPLC system for analysis. A characteristic property of DLLME-VA-μ-SPE is that any organic solvent and solid sorbent immiscible with water can be used. Special apparatus, or conical-bottom test tubes, and tedious procedures conventionally associated with DLLME such as centrifugation, or refrigeration of solvent are not necessary in the present approach. A novel material, ZIF-4 was employed as μ-SPE sorbent. Under the optimized conditions, the calibration curves were linear in the range of 1-1000 μg/L. The relative standard deviations and the limits of detection were in the range of 1.5% and 7.8% and 0.3 and 1 μg/L, respectively. The relative recoveries of canal water samples, spiked with drugs, were in the range of 94.3% and 114.7%. The results showed that IL-DLLME-μ-SPE was suitable for the determination of TCAs in water samples.

  6. [Determination of four phenolic endocrine disruptors in environmental water samples by high performance liquid chromatography-fluorescence detection using dispersive liquid-liquid microextraction coupled with derivatization].

    PubMed

    Wang, Xiaoyan; Qi, Weimei; Zhao, Xian'en; Lü, Tao; Wang, Xiya; Zheng, Longfang; Yan, Yehao; You, Jinmao

    2014-06-01

    To achieve accurate, fast and sensitive detection of phenolic endocrine disruptors in small volume of environmental water samples, a method of dispersive liquid-liquid microextraction (DLLME) coupled with fluorescent derivatization was developed for the determination of bisphenol A, nonylphenol, octylphenol and 4-tert-octylphenol in environmental water samples by high performance liquid chromatography-fluorescence detection (HPLC-FLD). The DLLME and derivatization conditions were investigated, and the optimized DLLME conditions for small volume of environmental water samples (pH 4.0) at room temperature were as follows: 70 microL chloroform as extraction solvent, 400 microL acetonitrile as dispersing solvent, vortex mixing for 3 min, and then high-speed centrifugation for 2 min. Using 2-[2-(7H-dibenzo [a, g] carbazol-7-yl)-ethoxy] ethyl chloroformate (DBCEC-Cl) as precolumn derivatization reagent, the stable derivatives of the four phenolic endocrine disruptors were obtained in pH 10.5 Na2CO3-NaHCO3 buffer/acetonitrile at 50 degrees C for 3 min, and then separated within 10 min by HPLC-FLD. The limits of detection (LODs) were in the range of 0.9-1.6 ng/L, and the limits of quantification (LOQs) were in the range of 3.8-7.1 ng/L. This method had perfect linearity, precision and recovery results, and showed obvious advantages and practicality comparing to the previously reported methods. It is a convenient and validated method for the routine analysis of phenolic endocrine disruptors in waste water of paper mill, lake water, domestic wastewater, tap water, etc.

  7. Kapitza Resistance between Few-Layer Graphene and Water: Liquid Layering Effects.

    PubMed

    Alexeev, Dmitry; Chen, Jie; Walther, Jens H; Giapis, Konstantinos P; Angelikopoulos, Panagiotis; Koumoutsakos, Petros

    2015-09-09

    The Kapitza resistance (RK) between few-layer graphene (FLG) and water was studied using molecular dynamics simulations. The RK was found to depend on the number of the layers in the FLG though, surprisingly, not on the water block thickness. This distinct size dependence is attributed to the large difference in the phonon mean free path between the FLG and water. Remarkably, RK is strongly dependent on the layering of water adjacent to the FLG, exhibiting an inverse proportionality relationship to the peak density of the first water layer, which is consistent with better acoustic phonon matching between FLG and water. These findings suggest novel ways to engineer the thermal transport properties of solid-liquid interfaces by controlling and regulating the liquid layering at the interface.

  8. Hydrogen Bonding and Related Properties in Liquid Water: A Car-Parrinello Molecular Dynamics Simulation Study.

    PubMed

    Guardia, Elvira; Skarmoutsos, Ioannis; Masia, Marco

    2015-07-23

    The local hydrogen-bonding structure and dynamics of liquid water have been investigated using the Car-Parrinello molecular dynamics simulation technique. The radial distribution functions and coordination numbers around water molecules have been found to be strongly dependent on the number of hydrogen bonds formed by each molecule, revealing also the existence of local structural heterogeneities in the structure of the liquid. The results obtained have also revealed the strong effect of the local hydrogen-bonding network on the local tetrahedral structure and entropy. The investigation of the dynamics of the local hydrogen-bonding network in liquid water has shown that this network is very labile, and the hydrogen bonds break and reform very rapidly. Nevertheless, it has been found that the hydrogen-bonding states associated with the formation of four hydrogen bonds by a water molecule exhibit the largest survival probability and corresponding lifetime. The reorientational motions of water molecules have also been found to be strongly dependent on their initial hydrogen-bonding state. Finally, the dependence of the librational and vibrational modes of water molecules on the local hydrogen-bonding network has been carefully examined, revealing a significant effect upon the libration and bond-stretching peak frequencies. The calculated low frequency peaks come in agreement with previously reported interpretations of the experimental low-frequency Raman spectrum of liquid water.

  9. 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.

  10. Models for a liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Buldyrev, S. V.; Franzese, G.; Giovambattista, N.; Malescio, G.; Sadr-Lahijany, M. R.; Scala, A.; Skibinsky, A.; Stanley, H. E.

    2002-02-01

    We use molecular dynamics simulations to study two- and three-dimensional models with the isotropic double-step potential which in addition to the hard core has a repulsive soft core of larger radius. Our results indicate that the presence of two characteristic repulsive distances (hard core and soft core) is sufficient to explain liquid anomalies and a liquid-liquid phase transition, but these two phenomena may occur independently. Thus liquid-liquid transitions may exist in systems like liquid metals, regardless of the presence of the density anomaly. For 2D, we propose a model with a specific set of hard core and soft core parameters, that qualitatively reproduces the phase diagram and anomalies of liquid water. We identify two solid phases: a square crystal (high density phase), and a triangular crystal (low density phase) and discuss the relation between the anomalies of liquid and the polymorphism of the solid. Similarly to real water, our 2D system may have the second critical point in the metastable liquid phase beyond the freezing line. In 3D, we find several sets of parameters for which two fluid-fluid phase transition lines exist: the first line between gas and liquid and the second line between high-density liquid (HDL) and low-density liquid (LDL). In all cases, the LDL phase shows no density anomaly in 3D. We relate the absence of the density anomaly with the positive slope of the LDL-HDL phase transition line.

  11. Automated dispersive liquid-liquid microextraction coupled to high performance liquid chromatography - cold vapour atomic fluorescence spectroscopy for the determination of mercury species in natural water samples.

    PubMed

    Liu, Yao-Min; Zhang, Feng-Ping; Jiao, Bao-Yu; Rao, Jin-Yu; Leng, Geng

    2017-04-14

    An automated, home-constructed, and low cost dispersive liquid-liquid microextraction (DLLME) device that directly coupled to a high performance liquid chromatography (HPLC) - cold vapour atomic fluorescence spectroscopy (CVAFS) system was designed and developed for the determination of trace concentrations of methylmercury (MeHg(+)), ethylmercury (EtHg(+)) and inorganic mercury (Hg(2+)) in natural waters. With a simple, miniaturized and efficient automated DLLME system, nanogram amounts of these mercury species were extracted from natural water samples and injected into a hyphenated HPLC-CVAFS for quantification. The complete analytical procedure, including chelation, extraction, phase separation, collection and injection of the extracts, as well as HPLC-CVAFS quantification, was automated. Key parameters, such as the type and volume of the chelation, extraction and dispersive solvent, aspiration speed, sample pH, salt effect and matrix effect, were thoroughly investigated. Under the optimum conditions, linear range was 10-1200ngL(-1) for EtHg(+) and 5-450ngL(-1) for MeHg(+) and Hg(2+). Limits of detection were 3.0ngL(-1) for EtHg(+) and 1.5ngL(-1) for MeHg(+) and Hg(2+). Reproducibility and recoveries were assessed by spiking three natural water samples with different Hg concentrations, giving recoveries from 88.4-96.1%, and relative standard deviations <5.1%.

  12. Molecular dynamics simulation of nanostructural organization in ionic liquid/water mixtures.

    PubMed

    Jiang, Wei; Wang, Yanting; Voth, Gregory A

    2007-05-10

    Molecular dynamics simulations have been carried out to investigate nanostructural organization in mixtures of 1-octyl-3-methylimidazolium nitrate ionic liquid and water at multiple water concentrations. Evolution of the polar network, water network, and micelle structures is visualized and analyzed via partial radial distribution functions. The calculated static partial structure factors show that within the range of water contents examined, polar networks, water networks, and micelles possess an approximately invariant characteristic length at around 20 A. Furthermore, the above calculations point out that, as the amount of water increases, the polar network is continuously broken up (screened) by the intruding water, while the structural organization of the water network and the micelle exhibits a turnover. At the turnover point, the most ordered micelle (cation-cation) structure and water (water-anion-water) network are formed. Thereafter, the structural organization abates drastically, and only loose micelle structure exists due to the dominant water-water interactions. The simulated turnover of structural organization agrees with the sharpest peak in the experimentally obtained structure factor in aqueous solutions of similar ionic liquids; the simulated water structure reveals that water can form liquidlike associated aggregates due to the planar symmetry and strong basicity of NO(3)-, in agreement with experiment. The turnover of structural organization of micelles results from the persistent competition between the hydrophobic interactions of the nonpolar groups and the breakup of the charged polar network with increasing water content, whereas the turnover of the water network results from the competition between the water-water and water-anion interactions.

  13. Electro-Optical Transmission and Liquid Water Content of Fogs and Clouds

    DTIC Science & Technology

    1985-05-01

    ter Clouds. 1.3. Experimental Apparatus and Techniques 1.4. Liquid Water Content of laboratory Cloud 1.5. Data Acquisition 1.6 Experimental ...Backscatter in Water Cloud at Visible Wavelengths 2.6. Experimental Verification of the Extinction-Backscatter Relation at Visible Wavelengths 13...16 SECTION 3: EXTINCTION AND BACKSCATTER OF WATER CLOUDS AT CO. 1 LASER WAVELENGTHS 3.1. Introduction 3.2 Experimental Measurement of

  14. Ultrasound-assisted dispersive liquid-liquid microextraction for the determination of six pyrethroids in river water.

    PubMed

    Yan, Hongyuan; Liu, Baomi; Du, Jingjing; Yang, Gengliang; Row, Kyung Ho

    2010-08-06

    A simple ultrasound-assisted dispersive liquid-liquid microextraction method combined with liquid chromatography was developed for the preconcentration and determination of six pyrethroids in river water samples. The procedure was based on a ternary solvent system to formatting tiny droplets of extractant in sample solution by dissolving appropriate amounts of water-immiscible extractant (tetrachloromethane) in watermiscible dispersive solvent (acetone). Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvent, extraction time, ultrasonic time, and centrifuging time) were evaluated. Under the optimum condition, good linearity was obtained in a range of 0.00059-1.52 mg L(-1) for all analytes with the correlation coefficient (r(2))>0.999. Intra-assay and inter-assay precision evaluated as the relative standard deviation (RSD) were less than 3.4 and 8.9%. The recoveries of six pyrethroids at three spiked levels were in the range of 86.2-109.3% with RSD of less than 8.7%. The enrichment factors for the six pyrethroids were ranged from 767 to 1033 folds.

  15. Sequential dispersive liquid-liquid microextraction for the determination of aryloxyphenoxy-propionate herbicides in water.

    PubMed

    Li, Songqing; Gao, Peng; Zhang, Jiaheng; Li, Yubo; Peng, Bing; Gao, Haixiang; Zhou, Wenfeng

    2012-12-01

    A novel dispersive liquid-liquid microextraction (DLLME) method followed by HPLC analysis, termed sequential DLLME, was developed for the preconcentration and determination of aryloxyphenoxy-propionate herbicides (i.e. haloxyfop-R-methyl, cyhalofop-butyl, fenoxaprop-P-ethyl, and fluazifop-P-butyl) in aqueous samples. The method is based on the combination of ultrasound-assisted DLLME with in situ ionic liquid (IL) DLLME into one extraction procedure and achieved better performance than widely used DLLME procedures. Chlorobenzene was used as the extraction solvent during the first extraction. Hydrophilic IL 1-octyl-3-methylimidazolium chloride was used as a dispersive solvent during the first extraction and as an extraction solvent during the second extraction after an in situ chloride exchange by bis[(trifluoromethane)sulfonyl]imide. Several experimental parameters affecting the extraction efficiency were studied and optimized with the design of experiments using MINITAB® 16 software. Under the optimized conditions, the extractions resulted in analyte recoveries of 78-91%. The correlation coefficients of the calibration curves ranged from 0.9994 to 0.9997 at concentrations of 10-300, 15-300, and 20-300 μg L(-1). The relative SDs (n = 5) ranged from 2.9 to 5.4%. The LODs for the four herbicides were between 1.50 and 6.12 μg L(-1).

  16. Mass-controlled capillary viscometer for a Newtonian liquid: viscosity of water at different temperatures.

    PubMed

    Digilov, Rafael M; Reiner, M

    2007-03-01

    The operation principle of the mass-controlled capillary viscometer is presented for a Newtonian liquid. The derived equation for the temporal changes of the mass in a liquid column draining under gravity through a discharge capillary tube accounts self-consistently for the inertial convective term associated with the acceleration effect. The viscosity of water measured at different temperatures using the new approach is in good agreement with literature data.

  17. Liquid Water on Mars: The Story from Meteorites

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2000-05-01

    Two studies shed light on the nature and timing of alteration by water of rocks from Mars. One is an experimental study of the alteration of a rock similar to Martian meteorites, conducted by Leslie Baker, Deborah Agenbroad, and Scott Wood (University of Idaho). They exposed crushed pieces of terrestrial lava flows to water at 23 C and 75 C and normal atmospheric pressure, and to hot water at 200 C to 400 C and a pressure 1000 times normal atmospheric to see what minerals would form. On the basis of a detailed comparison between the experimental products and the Martian meteorites Baker and colleagues conclude that the rocks from which Martian meteorites derived were intermittently exposed to water or water vapor; they were not exposed for a long time to large volumes of water. In an independent study, a team led by Tim Swindle (University of Arizona) tried to determine the time of formation of a reddish-brown alteration product in the Martian meteorite Lafayette. This meteorite appears to have formed from magma 1.3 billion years ago, but the rusty-looking weathering product, a mixture of clay minerals, iron oxide, and iron hydride, formed long after the original rock had crystallized. Although the precise time is not pinned down, their measurements indicate formation during the past 650 million years. Taken together, these studies suggest that water flowed intermittently on the surface of Mars during the past 650 million years.

  18. 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.

  19. Interactions in Water-Ionic Liquid Mixtures: Comparing Protic and Aprotic Systems.

    PubMed

    Reid, Joshua E S J; Gammons, Richard J; Slattery, John M; Walker, Adam J; Shimizu, Seishi

    2017-01-26

    The sensitivity of ionic liquids (ILs) to water affects their physical and chemical properties, even at relatively low concentrations, yet the structural thermodynamics of protic IL- (PIL-) water systems at low water concentrations still remains unclear. Using the rigorous Kirkwood-Buff theory of solutions, which can quantify the interactions between species in IL-water systems solely from thermodynamic data, we have shown the following: (1) Between analogous protic and aprotic ILs (AILs), the AIL cholinium bis(trifluoromethanesulfonyl)imide ([Ch][NTf2]) shows stronger interactions with water at low water concentrations, with the analogous PIL N,N-dimethylethanolammonium bis(trifluoromethanesulfonyl)imide ([DMEtA][NTf2]) having stronger water-ion interactions at higher water contents, despite water-ion interactions weakening with increasing water content in both systems. (2) Water has little effect on the average ion-ion interactions in both protic and aprotic ILs, aside from the AIL [Ch][NTf2], which shows a strengthening of ion-ion interactions with increasing water content. (3) Self-association of water in both PIL-water systems leading to the presence of large aggregates of water in IL-rich compositions has been inferred. Water-water interactions in [DMEtA][NTf2] were found to be similar to those of dialkylimidazolium AILs, whereas these interactions were much larger in the PIL N,N-dimethylethanolammonium propionate ([DMEtA][Pr]), attributed to the change in anion-water interactions.

  20. Application of response surface methodology for optimization of ionic liquid-based dispersive liquid-liquid microextraction of cadmium from water samples.

    PubMed

    Rajabi, M; Kamalabadi, M; Jamali, M R; Zolgharnein, J; Asanjarani, N

    2013-06-01

    A new, rapid, and simple method for the determination of cadmium in water samples was developed using ionic liquid-based dispersive liquid-liquid microextraction (IL-DLLME) coupled to flame atomic absorption spectrometry (FAAS). In the proposed approach, 2-(5-boromo-2-pyridylazo)-5-(diethyamino) phenol was used as a chelating agent and 1-hexyl-3-methylimidazolium bis(trifluoro methylsulfonyl)imide and acetone were selected as extraction and dispersive solvents, respectively. Sample pH, concentration of chelating agent, amount of ionic liquid (extraction solvent), disperser solvent volume, extraction time, salt effect, and centrifugation speed were selected as interested variables in IL-DLLME process. The significant variables affecting the extraction efficiency were determined using a Placket-Burman design. Thereafter, the significant variables were optimized using a Box-Behnken design and the quadratic model between the dependent and the independent variables was built. The optimum experimental conditions obtained from this statistical evaluation included: pH: 6.7; concentration of chelating agent: 1.1 10(-) (3) mol L(-1); and ionic liquid: 50.0 mg. Under the optimum conditions, the preconcentration factor obtained was 100. Calibration graph was linear in the range of 0.2-60 µg L(-1) with correlation coefficient of 0.9992. The limit of detection was 0.06 µg L(-) (1), which is lower than other reported approaches applied to the determination of cadmium using FAAS. The relative SD (n = 8) was 2.4%. The proposed method was successfully applied to the determination of trace amounts of cadmium in the real water samples with satisfactory results.

  1. Ab initio calculation of the deuterium quadrupole coupling in liquid water

    NASA Astrophysics Data System (ADS)

    Eggenberger, Rolf; Gerber, Stefan; Huber, Hanspeter; Searles, Debra; Welker, Marc

    1992-10-01

    The quadrupole coupling constant and asymmetry parameter for the deuteron in liquid heavy water was determined using purely theoretical methods. Molecular-dynamics simulations with the ab initio potential-energy surface of Lie and Clementi were used to generate snapshots of the liquid. The electric-field gradient at the deuteron was then calculated for these configurations and averaged to obtain the liquid quadrupole coupling constant. At 300 K a quadrupole coupling constant of 256±5 kHz and an asymmetry parameter of 0.164±0.003 were obtained. The temperature dependence of the quadrupole coupling constant was investigated.

  2. 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.

  3. Stability of Liquid Water on a Land Planet: Wider Habitable Zone for a Less Water Planet than an Aqua Planet

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Abe-Ouchi, A.

    2005-12-01

    Most of the previous studies on the habitable zone implicitly assume an ocean-covered 'aqua' planet that has a large amount of liquid water like the present Earth. However, there is a possibility of a habitable 'land' planet that is covered by vast dry desert but has locally abundant water. Ancient Mars might be in such a state. The conditions for the stability of liquid water can be different for a less water land planet from that of an aqua planet, because both the ice-albedo feedback, which causes the complete freezing, and the runaway greenhouse, which causes the complete evaporation, are enhanced by abundant water. Here, we investigated the condition for the solar flux that cause the complete freezing or evaporation of liquid water on a land planet using a general circulation model. We use a general circulation model, CCSR/NIES AGCM5.4g, which have been developed for the Earth's climate modeling by the Centre for Climate System Research, University of Tokyo and the National Institute for Environmental Research. To compare a land planet with an aqua planet, we consider an Earth-sized planet without topography with 1 bar air atmosphere on a circular orbit. The distribution of water on a land planet is completely determined by the atmospheric circulation. On a land planet, complete freezing and complete evaporation of water occurred at the 77% and 170% of the present Earth's solar flux, respectively. On the other hand, complete freezing and evaporation of an aqua planet occurs at 90% and about 130%, respectively. The absolute values of the criteria depends on the abundance of the greenhouse gases. However, the relative values between the land and aqua planets would not be changed. Thus, a land planet shows stronger resistance to both the complete freezing and evaporation of liquid water than an aqua planet. The stability field of liquid water is quite wide on a land planet compared with that of an aqua planet. It suggests that a water rich aqua planet may not be

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

    PubMed

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

    2006-06-14

    We calculate the hydration free energy of liquid TIP3P water at 298 K and 1 bar using a quasi-chemical 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.

  5. 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.

  6. 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.

  7. Fast screening of perfluorooctane sulfonate in water using vortex-assisted liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry.

    PubMed

    Papadopoulou, Aikaterini; Román, Iván P; Canals, Antonio; Tyrovola, Konstantina; Psillakis, Elefteria

    2011-04-08

    Fast screening of trace amounts of the perfluorooctane sulfonate anion (PFOS) in water samples was performed following a simple, fast and efficient sample preparation procedure based on vortex-assisted liquid-liquid microextraction (VALLME) prior to liquid chromatography-mass spectrometry. VALLME initially uses vortex agitation, a mild emulsification procedure to disperse microvolumes of octanol, a low density extractant solvent, in the aqueous sample. Microextraction under equilibrium conditions is thus achieved within few minutes. Subsequently, centrifugation separates the two phases and restores the initial microdrop shape of the octanol acceptor phase, which can be collected and used for liquid chromatography-single quadrupole mass spectrometry analysis. Several experimental parameters were controlled and the optimum conditions found were: 50 μL of octanol as the extractant phase; 20 mL aqueous donor samples (pH=2); a 2 min vortex extraction time with the vortex agitator set at a 2500 rpm rotational speed; no ionic strength adjustment. Centrifugation for 2 min at 3500 rpm yielded separation of the two phases throughout this study. Enhanced extraction efficiencies were observed at low pH which was likely due to enhanced electrostatic interaction between the negatively PFOS molecules and the positively charged octanol/water interface. The effect of pH was reduced in the presence of sodium chloride, likely due to electrical double layer compression. The linear response range for PFOS was from 5 to 500 ng L(-1) (coefficient of determination, r(2), 0.997) and the relative standard deviation for aqueous solutions containing 10 and 500 ng L(-1) PFOS were 7.4% and 6.5%, respectively. The limit of detection was 1.6 ng L(-1) with an enrichment factor of approximately 250. Analysis of spiked tap, river and well water samples revealed that matrix did not affect extraction.

  8. Rheological changes and kinetics of water uptake by poly(ionic liquid)-based thin films.

    PubMed

    Benedetti, Tânia M; Torresi, Roberto M

    2013-12-17

    Water uptake by thin films composed of the poly(ionic liquid) poly[diallyldimethylammonium bis(trifluoromethanesulfonyl)imide] (PDDATf2N) and the ionic liquid N,N-butylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr1.4Tf2N) was studied with a quartz crystal microbalance with dissipation. The data obtained for films with different compositions during the passage of dry and wet N2 flow through the films were simulated with the Kevin-Voigt viscoelastic model for assessment of the mass of uptake water as well as the viscoelastic parameters. Our results show that the ionic liquid acts as a plasticizer, reducing the rigidity of the film and decreasing the capacity of water uptake. Introduction to a Li salt (LiTf2N) increases the water uptake capacity and also affects both elastic and viscous parameters due to aggregation among the ions from the ionic liquid and Li(+). However, due to the preferable interaction of Li(+) ions with water molecules, these aggregates are broken when the film is hydrated. In short, the presence of water in such films affects their mechanical properties, which can reflect in their performances as solid state electrolytes and ion-conducting membranes for electrochemical applications.

  9. The dielectric behaviour of snow: A study versus liquid water content

    NASA Technical Reports Server (NTRS)

    Ambach, W.; Denoth, A.

    1980-01-01

    Snow is treated as a heterogeneous dielectric material consisting of ice, air, and water. The greater difference in the high frequency relative permittivity of dry snow and water allows to determine the liquid water content by measurements of the relative permittivity of snow. A plate condenser with a volume of about 1000 cv cm was used to measure the average liquid water content in a snow volume. Calibration was carried out using a freezing calorimeter. In order to measure the liquid water content in thin snow layers, a comb-shaped condenser was developed, which is the two dimensional analogon of the plate condenser. With this moisture meter the liquid water content was measured in layers of a few millimeters in thickness, whereby the effective depth of measurement is given by the penetration depth of electric field lines which is controlled by the spacing of the strip lines. Results of field measurements with both moisture meters, the plate condenser and the comb-shaped condenser, are given.

  10. Multimycotoxin analysis in water and fish plasma by liquid chromatography-tandem mass spectrometry.

    PubMed

    Tolosa, J; Font, G; Mañes, J; Ferrer, E

    2016-02-01

    High performance liquid chromatography-mass spectrometry was used for the determination of 15 mycotoxins in water and fish plasma samples, including aflatoxins, fumonisins, ochratoxin A, sterigmatocistin, fusarenon-X and emerging Fusarium mycotoxins. In this work, dispersive liquid-liquid microextraction (DLLME) was assessed as a sample treatment for the simultaneous extraction of mycotoxins. Results showed differences in recovery assays when different extraction solvents were employed. Ethyl acetate showed better recoveries for the major part of mycotoxins analyzed, except for aflatoxins B2, G1 and G2, which showed better recoveries when employing chloroform as extractant solvent. Fumonisins and beauvericin exhibited low recoveries in both water and plasma. This method was validated according to guidelines established by European Commission and has shown to be suitable to be applied in dietary and/or toxicokinetic studies in fish where is necessary to check mycotoxin contents in rearing water and fish plasma.

  11. Mid-tropospheric supercooled liquid water observation consistent with nucleation induced by a mountain lee wave

    NASA Astrophysics Data System (ADS)

    Madonna, Fabio; Russo, Felicita; Ware, Randolph; Pappalardo, Gelsomina

    2009-09-01

    A case study relative to the observation of unexpected liquid water in an apparently cloudless atmosphere is presented. Microwave radiometer profiler observations on 14 April 2008 at Boulder, Colorado, USA, showed an increase in the liquid water path with values higher than 0.05 mm and corresponding relative humidity saturation from 4.75 to 6.75 km above the ground level in profiles retrieved using a neural network algorithm. The formation of small supercooled droplets identified in the microwave retrieval of the temperature and relative humidity vertical profiles may result from nucleation stimulated by a mountain lee wave. The presented analysis reveals the existence of supercooled liquid water in the mid troposphere related to a wave activity that occurred in a sky condition classifiable as “clear” and describes an atmospheric scenario consistent with the observation of the so-called twilight zone.

  12. Effect of water uptake on morphology of polymerized ionic liquid block copolymers and random copolymers

    NASA Astrophysics Data System (ADS)

    Wang, Tsen-Shan; Ye, Yuesheng; Elabd, Yossef; Winey, Karen

    2012-02-01

    Dynamic studies of polymer morphology probe how the physical properties of polymerized ionic liquids are affected by the environment, such as temperature or moisture. For a series of poly(methyl methacrylate-b-1-[2-(methacryloyloxy)ethyl]-3-Butylimidazolium X^-) block and random copolymers with hydrophilic counterions (X^- = Br^-, HCO3^-, OH^-), the introduction of water vapor to the system can swell the ionic liquid block, causing enlarged hydrophilic domains and swollen channels for ion conduction. This expected expansion of ionic liquid domains in humid environments can be used to intelligently design these copolymers for use in technological applications. The effect of water vapor exposure in these imidazolium-based acrylate polymers is studied by small-angle X-ray scattering. These morphology results will be discussed alongside complementary studies of water uptake and ion conductivity.

  13. Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

    2012-11-01

    In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

  14. Freely accessible water does not decrease consumption of ethanol liquid diets.

    PubMed

    de Fiebre, NancyEllen C; de Fiebre, Christopher M

    2003-02-01

    In experimental studies, liquid ethanol diets are usually given as the sole source of nutrition and fluid. Two series of experiments were conducted to examine the effect of freely accessible water on the consumption of ethanol liquid diets in male Long-Evans rats. The consumption of diets and subsequent learning ability of rats were first examined in animals given twice-daily saline injections. One group received diet with no access to water for 12 weeks and was subsequently given free access to water with diets for an additional 12 weeks. A second group was given diet and water ad libitum for 24 weeks. Control animals received an isocaloric sucrose-containing diet (with or without ad libitum access to water). Subsequently, rats were tested for active avoidance learning. In the first 12 weeks, animals with ad libitum access to water drank more diet than did water-restricted animals, and previously water-restricted animals increased their diet consumption when access to water was freely available. All water-restricted animals, in both ethanol- and sucrose-treated groups, showed deficits in active avoidance learning, whereas only ethanol-treated animals in groups with ad libitum access to water showed learning deficits. In the second series of experiments, the effect of saline injections on diet consumption, both in the presence and absence of water, was examined. Although saline injections were associated with decreased diet consumption, there was no effect of free access to water. No differences in blood ethanol concentration were seen among groups. Findings obtained from both series of studies demonstrate that consumption of a Sustacal-based liquid ethanol diet does not decrease if access to water is freely available.

  15. Gas-liquid-liquid equilibria in mixtures of water, light gases, and hydrocarbons

    SciTech Connect

    Chao, K.C.

    1990-01-01

    Phase equilibrium in mixtures of water + light gases and water + heavy hydrocarbons has been investigated with the development of new local composition theory, new equations of state, and new experimental data. The preferential segregation and orientation of molecules due to different energies of molecular interaction has been simulated with square well molecules. Extensive simulation has been made for pure square well fluids and mixtures to find the local composition at wide ranges of states. A theory of local composition has been developed and an equation of state has been obtained for square well fluids. The new local composition theory has been embedded in several equations of state. The pressure of water is decoupled into a polar pressure and non-polar pressure according to the molecular model of water of Jorgensen et al. The polar pressure of water is combined with the BACK equation for the general description of polar fluids and their mixtures. Being derived from the steam table, the Augmented BACK equation is particularly suited for mixtures of water + non-polar substances such as the hydrocarbons. The hydrophobic character of the hydrocarbons had made their mixtures with water a special challenge. A new group contribution equation of state is developed to describe phase equilibrium and volumetric behavior of fluids while requiring only to know the molecular structure of the components. 15 refs., 1 fig.

  16. Removal of Multiple Contaminants from Water by Polyoxometalate Supported Ionic Liquid Phases (POM-SILPs).

    PubMed

    Herrmann, Sven; De Matteis, Laura; de la Fuente, Jesús M; Mitchell, Scott G; Streb, Carsten

    2017-02-01

    The simultaneous removal of organic, inorganic, and microbial contaminants from water by one material offers significant advantages when fast, facile, and robust water purification is required. Herein, we present a supported ionic liquid phase (SILP) composite where each component targets a specific type of water contaminant: a polyoxometalate-ionic liquid (POM-IL) is immobilized on porous silica, giving the heterogeneous SILP. The water-insoluble POM-IL is composed of antimicrobial alkylammonium cations and lacunary polyoxometalate anions with heavy-metal binding sites. The lipophilicity of the POM-IL enables adsorption of organic contaminants. The silica support can bind radionuclides. Using the POM-SILP in filtration columns enables one-step multi-contaminant water purification. The results show how multi-functional POM-SILPs can be designed for advanced purification applications.

  17. 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.

  18. 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.

  19. 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.

  20. Dispersive liquid-liquid microextraction for four phenolic environmental estrogens in water samples followed by determination using capillary electrophoresis.

    PubMed

    Liu, Junying; Lu, Wenhui; Liu, Huitao; Wu, Xiaqing; Li, Jinhua; Chen, Lingxin

    2016-10-01

    Dispersive liquid-liquid microextraction (DLLME) coupled with CE was successfully developed for simultaneous determination of four types of phenolic environmental estrogens (PEEs), namely hexestrol (HS), bisphenol A (BPA), diethylstilbestrol (DES) and dienestrol (DS). Several parameters affecting DLLME and CE conditions were systematically investigated including the type and volume of extraction solvent and dispersive solvent, extraction time, salt, pH value, surfactant, buffer solution and so on. Under the optimal conditions, DLLME-CE exhibited strong enrichment ability, presenting high enrichment factors of 467, 241, 367 and 362 for HS, BPA, DES and DS, respectively, as well as low detection limits of 0.3, 0.6, 0.6 and 0.3 μg/L, respectively. Excellent linearity was achieved in the range of 2.0-150 μg/L for HS and DS, and 4.0-300 μg/L for BPA and DES, with correlation coefficients R>0.9983. Recoveries ranging from 70.4 to 108.1% were obtained with tap water, lake water and seawater samples spiked at three concentration levels and the relative standard deviations (RSDs, for n = 5) were 2.1-9.7%. This DLLME-CE method with high selectivity and sensitivity, high stability, simplicity, cost-effectiveness, eco-friendliness was proved potentially applicable for the rapid and simultaneous determination of PEEs in complicated water samples.

  1. Molecular dynamics simulation for vapor-liquid coexistence of water in nanocylinder

    NASA Astrophysics Data System (ADS)

    Mima, Toshiki; Kinefuchi, Ikuya; Yoshimoto, Yuta; Miyoshi, Nobuya; Fukushima, Akinori; Tokumasu, Takashi; Takagi, Shu; Matsumoto, Yoichiro

    2013-03-01

    Molecular dynamics simulation was conducted in order to investigate the vapor-liquid coexistence of the water molecules in nanopore. In this research, the Lennard-Jones energy parameter between a water molecule and an atom of nanopore was optimized so as to model the contact angle between a water droplet and the carbon material in the fuel cell. The TIP4P/2005 as the model of a water molecule was used; this model produces well the vapor-liquid coexistence line. All of the systems were equilibrated by Nosé-Hoover thermostat. The electrostatic interaction between water molecules was calculated through smooth particle mesh Ewald method. First, we equilibrated a water plug in the single-wall atomistic nanocylinder as a model of nanopore in the fuel cell with radius 1.3nm. Water molecules burst from an interface of the water plug in equilibration. Then, the equilibrium densities both in dense and dilute region ware sampled over 1 ns. The vapor-liquid coexistence line, density profile, free energy profile will be presented in the session.

  2. Associations between polymorphisms of the gene and milk production traits in water buffaloes.

    PubMed

    Deng, T X; Pang, C Y; Lu, X R; Zhu, P; Duan, A Q; Liang, X W

    2016-03-01

    Signal transducer and activator of transcription 1 () is an important regulator of mammary gland differentiation and cell survival that has been regarded as a candidate gene affecting milk production traits in mammals. Therefore, this study was conducted to evaluate significant associations between SNP of the gene and milk production traits in buffaloes. Here, 18 SNP were identified in the buffalo gene, including 15 intronic mutations and 3 exon mutations. All the identified SNP were then genotyped using matrix-assisted laser desorption/ionization time of flight mass spectrometry methods from 192 buffaloes. All the SNP were in Hardy-Weinberg equilibrium, and 2 haplotype blocks were successfully constructed based on these SNP data, which formed 5 and 3 major haplotypes in the population (>5%), respectively. The results of association analysis showed that only SNP13 located in exon 10 was significantly associated with the milk production traits in the population ( < 0.05). Single nucleotide polymorphism 2, SNP5, SNP8, and SNP9 were associated with protein percentage, and SNP4 and SNP10 were associated with 305-d milk yield ( < 0.05). Our results provide evidence that polymorphisms of the buffalo gene are associated with milk production traits and can be used as a candidate gene for marker-assisted selection in buffalo breeding.

  3. A polarized liquid-liquid interface meets visible light-driven catalytic water oxidation.

    PubMed

    Rastgar, Shokoufeh; Pilarski, Martin; Wittstock, Gunther

    2016-09-15

    Hyperbranched nanostructured bismuth vanadate at a chemically polarized water/organic interface is applied for efficient visible light-driven catalytic oxidation of water in the presence of [Co(bpy)3](PF6)3 as an organic soluble electron acceptor. The photocurrent response originating from the transfer of photo-excited electrons in BiVO4 to [Co(bpy)3](3+) is measured by scanning electrochemical microscopy.

  4. Volumetric properties of human islet amyloid polypeptide in liquid water.

    PubMed

    Brovchenko, I; Andrews, M N; Oleinikova, A

    2010-04-28

    The volumetric properties of human islet amyloid polypeptide (hIAPP) in water were studied in a wide temperature range by computer simulations. The intrinsic density rho(p) and the intrinsic thermal expansion coefficient alpha(p) of hIAPP were evaluated by taking into account the difference between the volumetric properties of hydration and bulk water. The density of hydration water rho(h) was found to decrease almost linearly with temperature upon heating and its thermal expansion coefficient was found to be notably higher than that of bulk water. The peptide surface exposed to water is more hydrophobic and its rho(h) is smaller in conformation with a larger number of intrapeptide hydrogen bonds. The two hIAPP peptides studied (with and without disulfide bridge) show negative alpha(p), which is close to zero at 250 K and decreases to approximately -1.5 x 10(-3) K(-1) upon heating to 450 K. The analysis of various structural properties of peptides shows a correlation between the intrinsic peptide volumes and the number of intrapeptide hydrogen bonds. The obtained negative values of alpha(p) can be attributed to the shrinkage of the inner voids of the peptides upon heating.

  5. Coexistence of ice clusters and liquid-like water clusters on the Ru(0001) surface.

    PubMed

    Liu, Feng; Sturm, J M; Lee, Chris J; Bijkerk, Fred

    2017-03-10

    The RAIRS spectra of water adsorbed on Ru(0001) at 85 K are recorded from 600 cm(-1) to 4000 cm(-1). Measured at water coverages from 0.13 ML to 2.0 ML, the RAIRS spectra suggest that chemisorption of water on Ru(0001) depends on coverage. Water adsorbs on a clean Ru surface as chemisorbed ice-like clusters (likely through an O-Ru bond) up to 0.33 ML. Above this coverage, the chemisorbed layer saturates. Upon more exposure, water adsorbs as a liquid-like H-bonded layer without bonding to the Ru substrate. The chemisorbed water absorbs 7 times less IR per molecule than the liquid-like structure, which indicates that the orientation of the chemisorbed water is more parallel to the surface. Additionally, the influence of water-Ru bonding on H-bonding is reflected in the OH symmetric stretching mode. Under perturbation from water-Ru bonding, a large red shift (40 cm(-1)) in the free OH stretching frequency is observed in the chemisorbed clusters. By deconvoluting the main H-bonded OH stretching peak into five Gaussian sub-bands at 2945 ± 5 cm(-1), 3210 ± 5 cm(-1), 3300 ± 15 cm(-1), 3430 ± 5 cm(-1) and 3570 ± 10 cm(-1), changes in the H-bonding network are rationalized in terms of H-bonding motifs. The donor-acceptor-acceptor motif is significant only in the chemisorbed clusters. On the other hand, the donor-acceptor motif dominates in the liquid-like structure, which increases the disorder present in the adlayer. Although chemisorption is suppressed above 0.33 ML, no structural changes in the ice-like clusters are observed up to multilayer coverage. Therefore, ice-like and liquid-like water coexist in a meta-stable state at 85 K.

  6. 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

  7. A new device for magnetic stirring-assisted dispersive liquid-liquid microextraction of UV filters in environmental water samples.

    PubMed

    Zhang, Ping-Ping; Shi, Zhi-Guo; Yu, Qiong-Wei; Feng, Yu-Qi

    2011-02-15

    A new method based on dispersive liquid-liquid microextraction (DLLME) in combination with high-performance liquid chromatography (HPLC) has been developed for the analysis of UV filters. A specially designed flask, which has two narrow open necks with one of them having a capillary tip, was employed to facilitate the DLLME process. By adopting such a device, the extraction and subsequent phase separation were conveniently achieved. A binary solvent system of water sample and low-density extraction solvent (1-octanol) was used for the DLLME and no disperser solvent was involved. The extraction was accelerated by magnetic agitation of the two phases. After extraction, phase separation of the extraction solvent from the aqueous sample was easily achieved by leaving the extraction system statically for a while. No centrifugation step involving in classical DLLME was necessary. The analyte-enriched phase, floating above the sample solution, was elevated and concentrated into the narrow open tip of the flask by adding pure water into it via the other port, which was withdrawn with a microsyringe for the subsequent HPLC analysis. Under the optimized conditions, the limits of detection for the analytes were in range of 0.2-0.8ngmL(-1) .The linearity ranges were 8-20,000 ng mL(-1) for HB, 7-20,000 ng mL(-1) for DB, 8-10,000 ng mL(-1) for BP and 5-20,000 ng mL(-1) for HMB, respectively. Enrichment factors ranging from 59 to 107 folders were obtained for the analytes. The relative standard deviations (n=3) at a spiked level of 80 ng mL(-1) were between 1.4 and 4.8%. The proposed magnetic stirring-assisted DLLME method was successfully applied to the analysis of lake water samples.

  8. Determinations of cloud liquid water in the tropics from the SSM/I

    NASA Technical Reports Server (NTRS)

    Alishouse, John C.; Swift, Calvin; Ruf, Christopher; Snyder, Sheila; Vongsathorn, Jennifer

    1989-01-01

    Upward-looking microwave radiometric observations were used to validate the SSM/I determinations, and also as a basis for the determination of new coefficients. Due to insufficiency of the initial four channel algorithm for cloud liquid water, the improved algorithm was derived from the CORRAD (the University of Massachusetts autocorrelation radiometer) measurements of cloud liquid water and the matching SSM/I brightness temperatures using the standard linear regression. The correlation coefficients for the possible four channel combinations, and subsequently the best and the worst combinations were determined.

  9. Generation of liquid water on Mars through the melting of a dusty snowpack

    NASA Technical Reports Server (NTRS)

    Clow, Gary D.

    1987-01-01

    An optical/thermal model for dusty snowpacks at temperate Martian latitudes is used to investigate the possibility of valley network formation by liquid water that was provided by snowmelts, assuming insolation absorption under clear-sky conditions. The mean-annual surface temperatures for snow and the atmospheric exchange terms of the surface energy balance are constrained by global climate model results. Under favorable conditions, liquid water is generated at atmospheric pressures as low as 30-100 mbar, provided that the substrate is composed of regolith; this condition is in keeping with the cratered terrain expected in an ancient Martian surface.

  10. Measurement of liquid water content in a melting snowpack using cold calorimeter techniques

    NASA Technical Reports Server (NTRS)

    Rango, A.; Jones, E. B.; Howell, S.

    1980-01-01

    Liquid water in a snowpack is a quantifiable parameter of hydrological significance. It is also important in the interpretation of snowpack remote sensing data using microwave techniques. One acceptable approach to measuring liquid water content of a snowpack (by weight) is the cold calorimeter. This technique is presented from theory through application. Silicon oil was used successfully as the freezing agent. Consistent results can be obtained even when using operators with a minimum of training. Data can be obtained approximately every 15 minutes by using two calorimeters and three operators. Accuracy within one to two percent can be achieved under reasonable field conditions.

  11. Intraspecific diversity of Vibrio vulnificus in Galveston Bay water and oysters as determined by randomly amplified polymorphic DNA PCR.

    PubMed

    Lin, Meilan; Payne, Deborah A; Schwarz, John R

    2003-06-01

    Randomly amplified polymorphic DNA (RAPD) PCR was used to analyze the temporal and spatial intraspecific diversity of 208 Vibrio vulnificus strains isolated from Galveston Bay water and oysters at five different sites between June 2000 and June 2001. V. vulnificus was not detected during the winter months (December through February). The densities of V. vulnificus in water and oysters were positively correlated with water temperature. Cluster analysis of RAPD PCR profiles of the 208 V. vulnificus isolates revealed a high level of intraspecific diversity among the strains. No correlation was found between the intraspecific diversity among the isolates and sampling site or source of isolation. After not being detected during the winter months, the genetic diversity of V. vulnificus strains first isolated in March was 0.9167. Beginning in April, a higher level of intraspecific diversity (0.9933) and a major shift in population structure were observed among V. vulnificus isolates. These results suggest that a great genetic diversity of V. vulnificus strains exists in Galveston Bay water and oysters and that the population structure of this species is linked to changes in environmental conditions, especially temperature.

  12. Speciation of mercury in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Jia, Xiaoyu; Han, Yi; Liu, Xinli; Duan, Taicheng; Chen, Hangting

    2011-01-01

    The dispersive liquid-liquid microextraction (DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of mercury in water samples was described. Firstly methylmercury (MeHg +) and mercury (Hg 2+) were complexed with sodium diethyldithiocarbamate, and then the complexes were extracted into carbon tetrachloride by using DLLME. Under the optimized conditions, the enrichment factors of 138 and 350 for MeHg + and Hg 2+ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 0.0076 ng mL -1 for MeHg + and 0.0014 ng mL -1 for Hg 2+, respectively. The relative standard deviations for ten replicate measurements of 0.5 ng mL -1 MeHg + and Hg 2+ were 6.9% and 4.4%, respectively. Standard reference material of seawater (GBW(E)080042) was analyzed to verify the accuracy of the method and the results were in good agreement with the certified values. Finally, the developed method was successfully applied for the speciation of mercury in three environmental water samples.

  13. Combination of ultrasound-assisted ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the sensitive determination of benzoylureas pesticides in environmental water samples.

    PubMed

    Zhou, Qingxiang; Zhang, Xiaoguo

    2010-12-01

    This paper describes a new method for rapid and sensitive determination of diflubenzuron, flufenoxuron, triflumuron and chlorfluazuron in water samples by ultrasound-assisted ionic liquid dispersive liquid-phase microextraction in combination with HPLC. Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]) was used as the extraction solvent for the enrichment of four benzoylurea (BU) pesticides. Factors such as volume of [C(6)MIM][PF(6)], sonication time, sample pH, extraction time, centrifuging time and salting-out effect were systematically investigated. Under the optimum conditions, an excellent linear relationship was achieved in the range of 1.0-100 μg/L. The detection limits varied from 0.21 to 0.45 μg/L and the precision of the method was below 6.9% (RSD, n=6). The proposed method was successfully applied for the determination of these BU pesticides in water samples and excellent spiked recoveries were achieved. All these results demonstrated that this procedure provided a new simple, rapid, easy to operate, efficient and sensitive method for the analysis of BU pesticides in aqueous samples.

  14. 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.

  15. Colloidal crystals and water: Perspectives on liquid-solid nanoscale phenomena in wet particulate media.

    PubMed

    Gallego-Gómez, Francisco; Morales-Flórez, Víctor; Morales, Miguel; Blanco, Alvaro; López, Cefe

    2016-08-01

    Solid colloidal ensembles inherently contain water adsorbed from the ambient moisture. This water, confined in the porous network formed by the building submicron spheres, greatly affects the ensemble properties. Inversely, one can benefit from such influence on collective features to explore the water behavior in such nanoconfinements. Recently, novel approaches have been developed to investigate in-depth where and how water is placed in the nanometric pores of self-assembled colloidal crystals. Here, we summarize these advances, along with new ones, that are linked to general interfacial water phenomena like adsorption, capillary forces, and flow. Water-dependent structural properties of the colloidal crystal give clues to the interplay between nanoconfined water and solid fine particles that determines the behavior of ensembles. We elaborate on how the knowledge gained on water in colloidal crystals provides new opportunities for multidisciplinary study of interfacial and nanoconfined liquids and their essential role in the physics of utmost important systems such as particulate media.

  16. Radiometric Observations of Supercooled Liquid Water within a Split Front over the Sierra Nevada.

    NASA Astrophysics Data System (ADS)

    Heggli, Mark F.; Reynolds, David W.

    1985-11-01

    A storm bearing close structural resemblance to a katafront was observed from the ground with microwave radiometry and a vertically pointing Ka-band radar over the Sierra Nevada of California. The onset and duration of supercooled liquid water was determined and matched to a split front model used to describe the synoptic features of a katafront. Results indicate that prior to the passage of the upper front no supercooled liquid water was observed. This portion of the storm provided the deepest cloud and coldest cloud tops. Supercooled liquid water was most prevalent after the upper front passage, and persisted until the suspected surface front passage. The duration of measured supercooled water was 16 hours.This information broadens the knowledge regarding the presence of supercooled liquid water, and thus possible seeding potential, within winter storms so that treatment can be confined to the period of storms amenable to cloud seeding. Future studies may well confirm the ease with which these periods can be predicted on an operational basis in the Sierra Nevada.

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

    PubMed

    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.

  18. 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.

  19. 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.

  20. 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.

  1. The Inner Boundary of the Habitable Zone: Loss Processes of Liquid Water from Terrestrial Planet Surfaces

    NASA Astrophysics Data System (ADS)

    Stracke, B.; Godolt, M.; Grenfell, J. L.; von Paris, P.; Patzer, B.; Rauer, H.

    2012-04-01

    The question of habitability is very important in the context of terrestrial extrasolar planets. Generally, the Habitable Zone (HZ) is defined as the orbital region around a star, in which life-supporting (habitable) planets can exist. Taking into account that liquid water is a commonly accepted, fundamental requirement for the development of life - as we know it - the habitable region around a star is mainly determined by the stellar insolation of radiation, which is sufficient to maintain liquid water at the planetary surface. This study focuses on different processes that can lead to the complete loss of a liquid water reservoir from the surface of a terrestrial planet to determine the inner boundary of the HZ. The investigated criteria are, for example, reaching the temperature of the critical point of water at the planetary surface, the runaway greenhouse effect and the diffusion-limited escape of water from the atmosphere, which could lead to the loss of the complete water reservoir within the lifetime of a planet. We investigate these criteria, which determine the inner boundary of the HZ, with a one-dimensional radiative-convective model of a planetary atmosphere, which extends from the surface to the mid-mesosphere. Our modelling approach involves the step-by-step increase of the incoming stellar flux and the subsequent iterative calculation of resulting changes in the temperature profiles, the atmospheric water vapour content and the radiative properties. Therefore, this climate model had to be adapted to account for high temperatures and water mixing ratios. For example, the infrared radiative transfer scheme was improved to be suitable for such high temperature and pressure conditions. Modelling results are presented determining the inner boundary of the HZ affected by these processes, which can result in no liquid water on the planetary surface. In this context, especially the role of the runaway greenhouse effect is discussed in detail.

  2. Biphase photoelectrochemistry: A novel cell with a liquid-liquid phase boundary for water photoelectrolysis

    SciTech Connect

    Cheng, I.F. ); Jordan, J. )

    1991-05-02

    A new approach is described that overcomes the problems of photocorrosion and slow heterogeneous electron-transfer kinetics associated with light-assisted water oxidation at semiconductor electrodes. The photoanode, n-MoS{sub 2}, was immersed in an immiscible organic phase, nitromethane, or 1,2-dichloroethane, which insulated it from the aqueous catholyte. Tetrabutylammonium chloride provided ion environment that stabilized n-MoS{sub 2} in the unavoidably water-saturated nitromethane (or dichloroethane) phase. Chemical water oxidation by photoelectrogenerated Cl{sub 2} proceeded through a hypochlorite intermediate that was broken down with the help of RuO{sub 2} colloid catalysts, releasing O{sub 2}, H{sup +}, and Cl{sup {minus}}. Significant reduction of oxygen overvoltage was attained, corresponding to a photoanodic efficiency of 3%. Combined with efficient photocathodes developed in recent years, this could provide prospective foundations for hydrogen fuel generation by photoelectrochemical solar energy conversion.

  3. Monte Carlo simulation of the liquid-vapor interface of water using an ab initio potential

    NASA Astrophysics Data System (ADS)

    Lie, George C.; Grigoras, Stelian; Dang, Liem X.; Yang, Dah-Yen; McLean, A. Douglas

    1993-09-01

    Monte Carlo calculations have been carried out to study the interfacial properties of liquid water, using the Matsuoka-Clementi-Yoshimine (MCY) potential for the water-water interaction. The surface tension calculated at 298 K is 23.7±3.4 dyn/cm, to be compared with the experimental value of 72 dyn/cm. The interfacial 10-90 thickness is 4.70 Å, with the dipoles of the water molecules near the liquid phase pointing slightly towards the liquid phase and those near the gas phase pointing towards the gas phase. The interfacial water molecules are found to be more restricted in their rotation, as evidenced by the smaller root-mean-squared fluctuations of the dipole directions. The Volta potential difference across the interface arising from the permanent dipoles is estimated to be 0.024 V. A new and efficient method is proposed to calculated the surface excess energy. The excess energy calculated for the MCY water is 119 erg/cm2, to be compared with the experimental value of 120 erg/cm2. From the calculated surface excess energy, the temperature variation of the surface tension, or the surface entropy, for the MCY water is estimated to be -0.32 dyn/(cm2 K). This temperature variation is confirmed by another Monte Carlo study at 310 K to within the calculated uncertainty.

  4. Self-aggregation of cationic dimeric surfactants in water-ionic liquid binary mixtures.

    PubMed

    Martín, Victoria Isabel; Rodríguez, Amalia; Laschewsky, André; Moyá, María Luisa

    2014-09-15

    The micellization of four dimeric cationic surfactants ("gemini surfactants") derived from N-dodecyl-N,N,N-trimethylammonium chloride was studied in pure water and in water-ionic liquid (IL) solutions by a wide range of techniques. The dimeric surfactants are distinguished by their rigid spacer groups separating the two surfactant motifs, which range from C3 to C5 in length. In order to minimize organic ion pairing effects as well as the role of the ionic liquids as potential co-surfactants, ILs with inorganic hydrophilic anions and organic cations of limited hydrophobicity were chosen, namely ethyl, butyl, and hexyl-3-imidazolium chlorides. (1)H NMR two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy measurements, ROESY, supported this premise. The spacer nature hardly affects the micellization process, neither in water nor in water-IL solutions. However, it does influence the tendency of the dimeric surfactants to form elongated micelles when surfactant concentration increases. In order to have a better understanding of the ternary water-IL surfactant systems, the micellization of the surfactants was also studied in aqueous NaCl solutions, in water-ethylene glycol and in water-formamide binary mixtures. The combined results show that the ionic liquids play a double role in the mixed systems, operating simultaneously as background electrolytes and as polar organic solvents. The IL role as organic co-solvent becomes more dominant when its concentration increases, and when the IL alkyl chain length augments.

  5. Swelling behavior of chitosan hydrogels in ionic liquid-water binary systems.

    PubMed

    Spinks, Geoffrey M; Lee, Chang Kee; Wallace, Gordon G; Kim, Sun I; Kim, Seon Jeong

    2006-10-24

    The swelling behavior of chitosan hydrogels in ionic liquid-water binary systems was studied using hydrophilic room-temperature ionic liquids (RTILs) to elucidate the swelling mechanism of chitosan hydrogels. No penetration of RTIL into a dry chitosan material was observed. Swelling was achieved by soaking in water-RTIL binary mixtures, with larger swelling observed at higher water contents. In one instance, the binary mixture was acidic and produced larger than expected swelling due to the dissociation of the amine groups in the chitosan. The equilibrium binary system content behavior of the chitosan hydrogels depended upon the amount of free water, which is a measure of the number of water molecules that do not interact with the ionic liquid. After evaporation of water, remnant RTIL remained in the chitosan network and hardness testing indicated a plasticization effect, suggesting that the RTIL molecularly mixed with the chitosan. Chitosan hydrogels containing only RTIL were prepared by dropping pure RTIL onto a fully preswollen hydrogel followed by water evaporation. This method may be a useful means for preparing air-stable swollen chitosan gels.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Intermolecular correlations in liquid water at ambient conditions have generally been characterized through short range density fluctuations described through the atomic pair distribution functions. Recent numerical and experimental results have suggested that such a description of order or structure in liquid water is incomplete and there exist considerably longer ranged orientational correlations in water that can be studied through dipolar correlations. In this study, using large scale classical, atomistic molecular dynamics 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 (MgCl2) have a long range effect on the dipolar correlations, which cannot be explained by the notion of structure making and breaking by dissolved ions. 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 (CH4) 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.

  8. 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.

  9. Simulations of the Effects of Water Vapor, Cloud Liquid Water, and Ice on AMSU Moisture Channel Brightness Temperatures.

    NASA Astrophysics Data System (ADS)

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

    1994-10-01

    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 TB'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 TB's for window frequencies at 23.8, 89.0, and 157.0 GHz, and water vapor frequencies at 176.31, 180.3 1, and 182.31 GHz by documenting specific examples. This is accomplished through detailed analyses of TB'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 TB of changing surface emissivity also are addressed. The brightness temperature contribution functions are presented as an aid to physically interpreting AMSU TB's.Both liquid and ice clouds impact the TB's in a variety of ways. The TB'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 water impact on 157- and 183-GHz TB's than do lower clouds. Clouds depress TB's of the higher-frequency channels by suppressing, but not necessarily obscuring, radiance contributions from below. Thus, TB'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 µm near 157 and 183

  10. Use of amplified-fragment length polymorphism to study the ecology of Campylobacter jejuni in environmental water and to predict multilocus sequence typing clonal complexes.

    PubMed

    Lévesque, Simon; St-Pierre, Karen; Frost, Eric; Arbeit, Robert D; Michaud, Sophie

    2012-04-01

    We determined the genetic variability among water isolates of Campylobacter jejuni by using amplified-fragment length polymorphism (AFLP) and multilocus sequence typing (MLST). Across a highly diverse collection of isolates, AFLP clusters did not correlate with MLST clonal complexes, suggesting that AFLP is not reliable for deciphering population genetic relationships and may be problematic for larger epidemiologic analyses.

  11. Liquid-state theory of hydrocarbon-water systems: Application to methane, ethane, and propane

    SciTech Connect

    Lue, L.; Blankschtein, D.

    1992-10-15

    The authors studied the structural and bulk thermodynamic properties of hydrocarbon (methane, ethane, and propane)-water systems as well as pure water using the site-site Ornstein-Zernike (SSOZ) equation under a variety of different closure relations in order to compare the quantitative predictive capabilities of the various closures. For the hydrocarbon-water systems, the simple point-charge(SPC) potential was used to model water, and the optimized potentials for liquid, simulation (OPLS) were used to model the hydrocarbons. 69 refs., 11 figs., 8 tabs.

  12. Microscopic properties of liquid water from combined ab initio molecular dynamics and energy decomposition studies.

    PubMed

    Khaliullin, Rustam Z; Kühne, Thomas D

    2013-10-14

    The application of newly developed first-principle modeling techniques to liquid water deepens our understanding of the microscopic origins of its unusual macroscopic properties and behaviour. Here, we review two novel ab initio computational methods: second-generation Car-Parrinello molecular dynamics and decomposition analysis based on absolutely localized molecular orbitals. We show that these two methods in combination not only enable ab initio molecular dynamics simulations on previously inaccessible time and length scales, but also provide unprecedented insights into the nature of hydrogen bonding between water molecules. We discuss recent applications of these methods to water clusters and bulk water.

  13. Fundamental Study on Enhancement of Liquid-Liquid Direct Contact Heat Transfer of Descending Water Insoluble High Density Liquid Droplets in a Heat Source Water Layer by Using Wire Mesh as Dispersion Material

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Horibe, Akihiko; Yokoyama, Naoki; Haruki, Naoto

    This paper has dealt with liquid-liquid direct contact heat transfer characteristics by means of water insoluble heat transfer medium. In the present study, Perfluorocarbon(PFC, density of 1830kg/m3)was injected from above into a hot water layer, which was mounted by stainless steel wire net in order to make PFC droplets finer. The measuring result of the drop let diameter revealed that the droplet size distribution exerted an influence on the temperature effectiveness between PFC droplets and the hot water layer. It was observed that PFC droplets were dispersed by collision with stainless steel wire nets during falling in the hot water layer. Finally correlations equations of the temperature effectiveness and average diameter of PFC droplets had been derived as a function of some parameters.

  14. Uncertainty in vertically integrated liquid water content due to radar reflectivity observation error

    NASA Technical Reports Server (NTRS)

    French, Mark N.; Andrieu, Herve; Krajewski, Witold F.

    1995-01-01

    Radar reflectivity is used to estimate meteorological quantities such as rainfall rate, liquid water content, and the related quantity, vertically integrated liquid (VIL) water content. The estimation of any of these quantities depends on several assumptions related to the characteristics of the physical processes controlling the occurrence and character of water in the atmosphere. Additionally, there are many sources of error associated with radar observations, such as those due to brighthand, hail, and drop size distribution approximations. This work addresses one error of interest, the radar reflectivity observation error; other error sources are assumed to be corrected or negligible. The result is a relationship between the uncertainty in VIL water content and radar reflectivity measurement error. An example application illustrates the estimation of VIL uncertainty from typical radar reflectivity observations and indicates that the coefficient of variation in VIL is much larger than the coefficient of variation in radar reflectivity.

  15. Topological and spatial structure in the liquid-water-acetonitrile mixture

    NASA Astrophysics Data System (ADS)

    Bergman, Dan L.; Laaksonen, Aatto

    1998-10-01

    We have studied the structure of the liquid-water-acetonitrile mixture using molecular configurations obtained by molecular dynamics simulation. Spatial distribution functions have been used to analyze the local structures surrounding the molecules. The effective hydrogen-bond definition has been used to study basic hydrogen-bond properties and topological properties of the hydrogen-bond network. The topology of the network depends on the acetonitrile concentration. Up to a critical concentration, there is an infinite network of hydrogen-bonded water molecules. At higher concentrations, the network cannot be supported, and finite water clusters form. In order to characterize the networks and clusters, we have calculated some properties of loops and chains of water molecules. The patterns of hydrogen bonds surrounding the molecules and the size distribution of the clusters have also been calculated. We suggest that this approach can be useful when studying the structure of other liquid mixtures where hydrogen bonds are an important mode of interaction.

  16. Water-free rare-earth-metal ionic liquids/ionic liquid crystals based on hexanitratolanthanate(III) anion.

    PubMed

    Ji, Shun-Ping; Tang, Meng; He, Ling; Tao, Guo-Hong

    2013-04-02

    The hexanitratolanthanate anion (La(NO(3))(6)(3-)) is an interesting symmetric anion suitable to construct the component of water-free rare-earth-metal ionic liquids. The syntheses and structural characterization of eleven lanthanum nitrate complexes, [C(n)mim](3)[La(NO(3))(6)] (n=1, 2, 4, 6, 8, 12, 14, 16, 18), including 1,3-dimethylimidazolium hexanitratolanthanate ([C(1)mim](3)[La(NO(3))(6)], 1), 1-ethyl-3-methylimidazolium hexanitratolanthanate ([C(2)mim](3)[La(NO(3))(6)], 2), 1-butyl-3-methylimidazolium hexanitratolanthanate ([C(4)mim](3)[La(NO(3))(6)], 3), 1-isobutyl-3-methylimidazolium hexanetratolanthanate ([isoC(4)mim](3)[La(NO(3))(6)], 4), 1-methyl-3-(3'-methylbutyl)imidazolium hexanitratolanthanate ([MC(4)mim](3)[La(NO(3))(6)], 5), 1-hexyl-3-methylimidazolium hexanitratolanthanate ([C(6)mim](3)[La(NO(3))(6)], 6), 1-methyl-3-octylimidazolium hexanitratolanthanate ([C(8)mim](3)[La(NO(3))(6)], 7), 1-dodecyl-3-methylimidazolium hexanitratolanthanate ([C(12)mim](3)[La(NO(3))(6)], 8), 1-methyl-3-tetradecylimidazolium hexanitratolanthanate ([C(14)mim](3)[La-(NO(3))(6)], 9), 1-hexadecyl-3-methylimid-azolium hexanitratolanthanum ([C(16)dmim](3)[La(NO(3))(6)], 10), and 1-methyl-3-octadecylimidazolium hexanitratolanthanate ([C(18)mim](3)[La(NO(3))(6)], 11) are reported. All new compounds were characterized by (1)H and (13)C NMR, and IR spectroscopy as well as elemental analysis. The crystal structure of compound 1 was determined by using single-crystal X-ray diffraction, giving the following crystallographic information: monoclinic; P2(1)/c; a=15.3170 (3), b=14.2340 (2), c=13.8954(2) Å; β=94.3453(15)°, V=3020.80(9) Å(3), Z=4, ρ=1.764 g cm(-3). The coordination polyhedron around the lanthanum ion is rationalized by six nitrate anions with twelve oxygen atoms. No hydrogen-bonding network or water molecule was found in 1. The thermodynamic stability of the new complexes was investigated by using thermogravimetric analysis (TGA). The water

  17. The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like.

    PubMed

    Willard, Adam P; Chandler, David

    2014-11-14

    With molecular simulation for water and a tunable hydrophobic substrate, we apply the instantaneous interface construction [A. P. Willard and D. Chandler, "Instantaneous liquid interfaces," J. Phys. Chem. B 114, 1954-1958 (2010)] to examine the similarity between a water-vapor interface and a water-hydrophobic surface interface. We show that attractive interactions between a hydrophobic surface and water affect capillary wave fluctuations of the instantaneous liquid interface, but these attractive interactions have essentially no effect on the intrinsic interface. The intrinsic interface refers to molecular structure in terms of distances from the instantaneous interface. Further, the intrinsic interface of liquid water and a hydrophobic substrate differs little from that of water and its vapor. The same is not true, we show, for an interface between water and a hydrophilic substrate. In that case, strong directional substrate-water interactions disrupt the liquid-vapor-like interfacial hydrogen bonding network.

  18. Effects of porosity distribution variation on the liquid water flux through gas diffusion layers of PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Zhan, Zhigang; Xiao, Jinsheng; Li, Dayong; Pan, Mu; Yuan, Runzhang

    Flooding of the membrane electrode assembly (MEA) and dehydrating of the polymer electrolyte membrane have been the key problems to be solved for polymer electrolyte membrane fuel cells (PEMFCs). So far, almost no papers published have focused on studies of the liquid water flux through differently structured gas diffusion layers (GDLs). For gas diffusion layers including structures of uniform porosity, changes in porosity (GDL with microporous layer (MPL)) and gradient change porosity, using a one-dimensional model, the liquid saturation distribution is analyzed based on the assumption of a fixed liquid water flux through the GDL. And then the liquid water flux through the GDL is calculated based on the assumption of a fixed liquid saturation difference between the interfaces of the catalyst layer/GDL and the GDL/gas channel. Our results show that under steady-state conditions, the liquid water flux through the GDL increases as contact angle and porosity increase and as the GDL thickness decreases. When a MPL is placed between the catalyst layer and the GDL, the liquid saturation is redistributed across the MPL and GDL. This improves the liquid water draining performance. The liquid water flux through the GDL increases as the MPL porosity increases and the MPL thickness decreases. When the total thickness of the GDL and MPL is kept constant and when the MPL is thinned to 3 μm, the liquid water flux increases considerably, i.e. flooding of MEA is difficult. A GDL with a gradient of porosity is more favorable for liquid water discharge from catalyst layer into the gas channel; for the GDLs with the same equivalent porosity, the larger the gradient is, the more easily the liquid water is discharged. Of the computed cases, a GDL with a linear porosity 0.4 x + 0.4 is the best.

  19. Dispersive liquid-liquid microextraction combined with online preconcentration MEKC for the determination of some phenoxyacetic acids in drinking water.

    PubMed

    Zhang, Yaohai; Jiao, Bining

    2013-09-01

    A fast and simple technique composed of dispersive liquid-liquid microextraction (DLLME) and online preconcentration MEKC with diode array detection was developed for the determination of four phenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,6-dichlorophenoxyacetic acid, and 4-chlorophenoxyacetic acid, in drinking water. The four phenoxyacetic acids were separated in reversed-migration MEKC to the baseline. About 145-fold increases in detection sensitivity were observed with online concentration strategy, compared with standard hydrodynamic injection (5 s at 25 mbar pressure). LODs ranged from 0.002 to 0.005 mg/L using only the online preconcentration procedures without any offline concentration of the extract. A DLLME procedure was used in combination with the proposed online preconcentration strategies, which achieved the determination of analytes at limits of quantification ranging from 0.2 to 0.5 μg/kg, which is far lower than the maximum residue limits established by China. The satisfactory recoveries obtained by DLMME spiked at two levels ranged from 67.2 to 99.4% with RSD <15%, making this proposed method suitable for the determination of phenoxyacetic acids in water samples.

  20. Homogeneous liquid-liquid microextraction via flotation assistance for rapid and efficient determination of polycyclic aromatic hydrocarbons in water samples.

    PubMed

    Hosseini, Majid Haji; Rezaee, Mohammad; Akbarian, Saeid; Mizani, Farhang; Pourjavid, Mohammad Reza; Arabieh, Masoud

    2013-01-31

    In this work, a rapid, simple and efficient homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) method was developed based on applying low density organic solvents without no centrifugation. For the first time, a special extraction cell was designed to facilitate collection of the low-density solvent extraction in the determination of four polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). The effect of different variables on the extraction efficiency was studied simultaneously using experimental design. The variables of interest in the HLLME-FA were selected as extraction and homogeneous solvent volumes, ionic strength and extraction time. Response surface methodology (RSM) was applied to investigate the optimum conditions of all the variables. Using optimized variables in the extraction process, for all target PAHs, the detection limits, the precisions and the linearity of the method were found in the range of 14-41 μg L(-1), 3.7-10.3% (RSD, n=3) and 50-1000 μg L(-1), respectively. The proposed method has been successfully applied to the analysis of four target PAHs in the water samples, and satisfactory results were obtained.

  1. 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

  2. A new chiral residue analysis method for triazole fungicides in water using dispersive liquid-liquid microextraction (DLLME).

    PubMed

    Luo, Mai; Liu, Donghui; Zhou, Zhiqiang; Wang, Peng

    2013-09-01

    A rapid, simple, reliable, and environment-friendly method for the residue analysis of the enantiomers of four chiral fungicides including hexaconazole, triadimefon, tebuconazole, and penconazole in water samples was developed by dispersive liquid-liquid microextraction (DLLME) pretreatment followed by chiral high-performance liquid chromatography (HPLC)-DAD detection. The enantiomers were separated on a Chiralpak IC column by HPLC applying n-hexane or petroleum ether as mobile phase and ethanol or isopropanol as modifier. The influences of mobile phase composition and temperature on the resolution were investigated and most of the enantiomers could be completely separated in 20 min under optimized conditions. The thermodynamic parameters indicated that the separation was enthalpy-driven. The elution orders were detected by both circular dichroism detector (CD) and optical rotatory dispersion detector (ORD). Parameters affecting the DLLME performance for pretreatment of the chiral fungicides residue in water samples, such as the extraction and dispersive solvents and their volume, were studied and optimized. Under the optimum microextraction condition the enrichment factors were over 121 and the linearities were 30-1500 µg L(-1) with the correlation coefficients (R(2)) over 0.9988 and the recoveries were between 88.7% and 103.7% at the spiking levels of 0.5, 0.25, and 0.05 mg L(-1) (for each enantiomer) with relative standard deviations varying from 1.38% to 6.70% (n = 6) The limits of detection (LODs) ranged from 8.5 to 29.0 µg L(-1) (S/N = 3).

  3. Sub- and super-Maxwellian evaporation of simple gases from liquid water

    NASA Astrophysics Data System (ADS)

    Kann, Z. R.; Skinner, J. L.

    2016-04-01

    Non-Maxwellian evaporation of light atoms and molecules (particles) such as He and H2 from liquids has been observed experimentally. In this work, we use simulations to study systematically the evaporation of Lennard-Jones particles from liquid water. We find instances of sub- and super-Maxwellian evaporation, depending on the mass of the particle and the particle-water interaction strength. The observed trends are in qualitative agreement with experiment. We interpret these trends in terms of the potential of mean force and the effectiveness and frequency of collisions during the evaporation process. The angular distribution of evaporating particles is also analyzed, and it is shown that trends in the energy from velocity components tangential and normal to the liquid surface must be understood separately in order to interpret properly the angular distributions.

  4. Equation of state of ammonia-water liquid - Derivation and planetological applications

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    The present least-squares fit calculation of the equation of state for ammonia-water liquid has yielded results for the zero-100 wt pct NH3, 170-300 K temperature, and zero-10 kb pressure parameter ranges. In conjunction with solid density and thermodynamic measurements, the present calculated and measured liquid densities are used to yield estimates of density and thermal expansion at 1 bar for the solid phases of ammonia's monohydrate, dihydrate, and hemihydrate between absolute zero and their respective melting points. Attention is given to the implications for icy satellite morphologic and tectonic forms of peritectic ammonia-water liquid that is neutrally buoyant relative to the corresponding solid phases.

  5. Sub- and super-Maxwellian evaporation of simple gases from liquid water.

    PubMed

    Kann, Z R; Skinner, J L

    2016-04-21

    Non-Maxwellian evaporation of light atoms and molecules (particles) such as He and H2 from liquids has been observed experimentally. In this work, we use simulations to study systematically the evaporation of Lennard-Jones particles from liquid water. We find instances of sub- and super-Maxwellian evaporation, depending on the mass of the particle and the particle-water interaction strength. The observed trends are in qualitative agreement with experiment. We interpret these trends in terms of the potential of mean force and the effectiveness and frequency of collisions during the evaporation process. The angular distribution of evaporating particles is also analyzed, and it is shown that trends in the energy from velocity components tangential and normal to the liquid surface must be understood separately in order to interpret properly the angular distributions.

  6. 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.

  7. Interaction of a sodium ion with the water liquid-vapor interface

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Molecular dynamics results are presented for the density profile of a sodium ion near the water liquid-vapor interface at 320 K. These results are compared with the predictions of a simple dielectric model for the interaction of a monovalent ion with this interface. The interfacial region described by the model profile is too narrow and the profile decreases too abruptly near the solution interface. Thus, the simple model does not provide a satisfactory description of the molecular dynamics results for ion positions within two molecular diameters from the solution interface where appreciable ion concentrations are observed. These results suggest that surfaces associated with dielectric models of ionic processes at aqueous solution interfaces should be located at least two molecular diameters inside the liquid phase. A free energy expense of about 2 kcal/mol is required to move the ion within two molecular layers of the free water liquid-vapor interface.

  8. Experimental, Numerical, and Analytical Slosh Dynamics of Water and Liquid Nitrogen in a Spherical Tank

    NASA Technical Reports Server (NTRS)

    Storey, Jedediah Morse

    2016-01-01

    Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving performance of space missions when a significant percentage of the spacecraft's mass is a liquid. Computational fluid dynamics simulations can be used to predict the dynamics of slosh, but these programs require extensive validation. Many experimental and numerical studies of water slosh have been conducted. However, slosh data for cryogenic liquids is lacking. Water and cryogenic liquid nitrogen are used in various ground-based tests with a spherical tank to characterize damping, slosh mode frequencies, and slosh forces. A single ring baffle is installed in the tank for some of the tests. Analytical models for slosh modes, slosh forces, and baffle damping are constructed based on prior work. Select experiments are simulated using a commercial CFD software, and the numerical results are compared to the analytical and experimental results for the purposes of validation and methodology-improvement.

  9. 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.

  10. Application of dispersive liquid-liquid microextraction combined with high-performance liquid chromatography for the determination of methomyl in natural waters.

    PubMed

    Wei, Guohui; Li, Yanyan; Wang, Xuedong

    2007-12-01

    A new method was developed for determination of methomyl in water samples by combining a dispersive liquid-liquid microextraction (DLLME) technique with HPLC-variable wavelength detection (VWD). In this extraction method, 0.50 mL of methanol (as dispersive solvent) containing 20.0 microL of tetrachloroethane (as extraction solvent) was rapidly injected by syringe into a 5.00-mL water sample containing the analyte, thereby forming a cloudy solution. After phase separation by centrifugation for 2 min at 4000 rpm, the enriched analyte in the settled phase (8 +/- 0.2 microL) was at the bottom of the conical test tube. A 5.0-microL volume of the settled phase was analyzed by HPLC-VWD. Parameters such as the nature and volume of the extraction solvent and the dispersive solvent, extraction time, and the salt concentration were optimized. Under the optimum conditions, the enrichment factor could reach 70.7 for a 5.00-mL water sample and the linear range, detection limit (S/N = 3), and precision (RSD, n = 6) were 3-5000 ng/mL, 1.0 ng/mL, and 2.6%, respectively. River and lake water samples were successfully analyzed by the proposed method. Comparison of this method with solid-phase extraction, solid-phase microextraction, and single-drop microextraction, indicates that DLLME combined with HPLC-VWD is a simple, fast, and low-cost method for the determination of methomyl, and thus has tremendous potential in trace analysis of methomyl in natural waters.

  11. 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

  12. 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.

  13. Observed and simulated temperature dependence of the liquid water path of low clouds

    SciTech Connect

    Del Genio, A.D.; Wolf, A.B.

    1996-04-01

    Data being acquired at the Atmospheric Radiation Measurement (ARM) Southern great Plains (SGP) Cloud and Radiation Testbed (CART) site can be used to examine the factors determining the temperature dependence of cloud optical thickness. We focus on cloud liquid water and physical thickness variations which can be derived from existing ARM measurements.

  14. Lipid-induced structural turnover of water droplets to liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Sidiq, Sumyra; Pal, Santanu Kumar

    2014-04-01

    For the first time direct observation of structural turnover of water droplets to liquid crystal (LC) droplets with radial LC ordering was observed in presence of surfactants and lipids. Study of interactions between enzymes with the topological defects in the LC mediate the response of these droplets suggesting new principles for the design of chemical and biological sensors.

  15. 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.

  16. GENERIC, COMPONENT FAILURE DATA BASE FOR LIGHT WATER AND LIQUID SODIUM REACTOR PRAs

    SciTech Connect

    S. A. Eide; S. V. Chmielewski; T. D. Swantz

    1990-02-01

    A comprehensive generic component failure data base has been developed for light water and liquid sodium reactor probabilistic risk assessments (PRAs) . The Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR) and the Centralized Reliability Data Organization (CREDO) data bases were used to generate component failure rates . Using this approach, most of the failure rates are based on actual plant data rather than existing estimates .

  17. 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...

  18. A complete dielectric response model for liquid water: a solution of the Bethe ridge problem.

    PubMed

    Emfietzoglou, Dimitris; Cucinotta, Francis A; Nikjoo, Hooshang

    2005-08-01

    We present a complete yet computationally simple model for the dielectric response function of liquid water over the energy-momentum plane, which, in contrast to earlier models, is consistent with the recent inelastic X-ray scattering spectroscopy data at both zero and finite momentum transfer values. The model follows Ritchie's extended-Drude algorithm and is particularly effective at the region of the Bethe ridge, substantially improving previous models. The present development allows for a more accurate simulation of the inelastic scattering and energy deposition process of low-energy electrons in liquid water and other biomaterials. As an example, we calculate the stopping power of liquid water for electrons over the 0.1-10 keV range where direct experimental measurements are still impractical and the Bethe stopping formula is inaccurate. The new stopping power values are up to 30-40% lower than previous calculations. Within the range of validity of the first Born approximation, the new values are accurate to within the experimental uncertainties (a few percent). At the low end, the introduction of Born corrections raises the uncertainty to perhaps approximately 10%. Thus the present model helps extend the ICRU electron stopping power database for liquid water down to about two orders of magnitude with a comparable level of uncertainty.

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

    PubMed

    Attri, Pankaj; Venkatesu, P; Kumar, Anil

    2012-10-07

    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, α-chymotrypsin and succinylated Con A. We show that the enzymatic activity is regained and in certain circumstances enhanced.

  20. A Laboratory Comparison of Field Techniques for Measurement of the Liquid Water Fraction of Snow

    DTIC Science & Technology

    1990-02-01

    Tiuri and A. Sihvola (1984) A comparative study of instruments for measuring the liquid water content of snow. Journal of Applied Phyisics , 56:2154...meaningful comparison. Applying the same statistical tests as for the laboratory data consistently showed a bias in the compar- isons. We attribute the

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

    DOE Data Explorer

    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. Biodegradability of immidazolium, pyridinium, piperidinium and pyrrolidinium based ionic liquid in different water source

    NASA Astrophysics Data System (ADS)

    Krishnan, S.; Quraishi, K. S.; Aminuddin, N. F.; Mazlan, F. A.; Leveque, J.-M.

    2016-11-01

    Ionic Liquid (IL), combination of an organic cation with an organic or inorganic cation, possess some remarkable physical chemical properties such as no virtual vapor pressure (allowing recyclability and reusability), wide liquid range, high thermal and chemical stability, ease to choose hydrophobic/hydrophilic character and wide electrochemical window. Owing to that, they have become increasingly popular as green solvents/additives/catalysts for organic synthetic chemistry, extraction, electrochemistry, catalysis, biomass conversion, biotechnologies and pharmaceutical applications. This is acknowledged by the exponential number of yearly published articles related to them. However, even if these are very widely studied in the international scientific community, they are not or very little used on an industrial scale, particularly because of the lack of data on their toxicity and biodegradability. Notably hydrophobic ILs seems to display higher toxicity towards microorganisms and lower biodegradability compared to their hydrophilic analogues since they are not readily disassociated in water. This present work aims to explore the biodegradability of 8 different insoluble ILs in different sources of water bearing varied amount of microorganisms to study the impact of the used water on the biodegradability assessment. The water sources used are Type III Water, Pond water and filtered Sewage Water. Based on the results obtained, it can be concluded that the type of water has a very minor influence on the biodegradability effect of insoluble ILs. However, there is still some degree of influence on the type of water with the biodegradability.

  3. 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.

  4. Infrared spectroscopy of acetone-water liquid mixtures. I. Factor analysis

    NASA Astrophysics Data System (ADS)

    Max, Jean-Joseph; Chapados, Camille

    2003-09-01

    Acetone and water mixtures covering the whole solubility range were measured by Fourier transform infrared attenuated total reflectance spectroscopy. In this system, only water can supply the hydrogen atoms necessary for hydrogen bonding. Using spectral windowing with factor analysis (FA), 10 principal factors were retrieved, five water and five acetone. Hydrogen bonding is observed on the carbonyl stretch band as water is introduced in the solution, redshifting the band further from its gas position than that observed in pure liquid acetone. This indicates that the hydrogen bonding is stronger than the acetone dipole-dipole interactions because it overrides them. A water molecule isolated in acetone is twice H bonded through its two H atoms; although both OH groups are H-bond donors, the OH stretch band is less redshifted (˜138 cm-1) than that of pure liquid water (˜401 cm-1). This is attributable to the two lone electron pairs remaining on the oxygen atom that sustain a large part of the OH valence bond strength. Hydrogen bonds on the water oxygen weaken both its OH valence bonds and modify the OH stretch band when water is added to the solution. The oxygen atoms of both water and acetone can accept 0, 1, and 2 H bonds given by water to yield three water and three acetone situations. Since these six situations are far less than the 10 principal factors retrieved by FA, other perturbations must be present to account for the difference. Although acetone and water are intermingled through H bonds, hydrates in the sense of an acetone molecule sequestering a number of water molecules or altering the H-bonding water network are not present because the principal factors evolve independently.

  5. The vibrational proton potential in bulk liquid water and ice.

    PubMed

    Burnham, C J; Anick, D J; Mankoo, P K; Reiter, G F

    2008-04-21

    We present an empirical flexible and polarizable water model which gives an improved description of the position, momentum, and dynamical (spectroscopic) distributions of H nuclei in water. We use path integral molecular dynamics techniques in order to obtain momentum and position distributions and an approximate solution to the Schrodinger equation to obtain the infrared (IR) spectrum. We show that when the calculated distributions are compared to experiment the existing empirical models tend to overestimate the stiffness of the H nuclei involved in H bonds. Also, these models vastly underestimate the enormous increase in the integrated IR intensity observed in the bulk over the gas-phase value. We demonstrate that the over-rigidity of the OH stretch and the underestimation of intensity are connected to the failure of existing models to reproduce the correct monomer polarizability surface. A new model, TTM4-F, is parametrized against electronic structure results in order to better reproduce the polarizability surface. It is found that TTM4-F gives a superior description of the observed spectroscopy, showing both the correct redshift and a much improved intensity. TTM4-F also has a somewhat improved dielectric constant and OH distribution function. It also gives an improved match to the experimental momentum distribution, although some discrepancies remain.

  6. Vortex-assisted low density solvent based demulsified dispersive liquid-liquid microextraction and high-performance liquid chromatography for the determination of organophosphorus pesticides in water samples.

    PubMed

    Seebunrueng, Ketsarin; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

    2014-05-01

    A simple, rapid, effective and eco-friendly preconcentration method, vortex-assisted low density solvent based solvent demulsified dispersive liquid-liquid microextraction (VLDS-SD-DLLME), followed by high performance liquid chromatography-diode array detector (HPLC-DAD) analysis, has been developed for the first time for the determination of four organophosphorus pesticides (OPPs) (e.g., azinphos-methyl, parathion-methyl, fenitrothion and diazinon) in environmental water samples. In this preconcentration procedure, an emulsion was obtained after the mixture of extraction solvent (1-dodecanol) and dispersive solvent (acetonitrile, ACN) was injected rapidly into 10 mL of the sample solution. The vortex agitator aided the dispersion of the extraction solvent into the sample solution. After the formation of an emulsion, the demulsifier (ACN) was added, resulting in the rapid separation of the mixture into two phases without centrifugation. Under optimal conditions, the proposed method provided high extraction efficiency (90-99%), good linearity range (0.5-500 ng mL(-1)), low limits of detection (0.25-1 ng mL(-1)) and good repeatability and recoveries were obtained.

  7. 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 μs. 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 μs. 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.

  8. 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.

  9. 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.

  10. Simultaneous liquid-liquid microextraction/methylation for the determination of haloacetic acids in drinking waters by headspace gas chromatography.

    PubMed

    Cardador, M J; Serrano, A; Gallego, M

    2008-10-31

    A novel analytical method that combines simultaneous liquid-liquid microextraction/methylation and headspace gas chromatography-mass spectrometry for the determination of nine haloacetic acids (HAAs) in water was reported. A mechanistic model on the basis of mass transfer with chemical reaction in which methylation of HAAs was accomplished in n-pentane-water (150 microl-10 ml) two-phase system with a tetrabutylammonium salt as phase transfer catalyst was proposed. Derivatisation with dimethylsulphate was completed in 3 min by shaking at room temperature. The methyl ester derivatives and the organic phase were completely volatilised by static headspace technique, being the gaseous phase analysed. Parameters related to the extraction/methylation and headspace generation of HAAs were studied and the results were compared with methyl haloacetate standards to establish the yield of each step. The thermal instability of HAAs, by degradation to their respective halogenated hydrocarbon by decarboxylation, and the possible hydrolysation of the methyl esters were rigorously controlled in the whole process to obtain a reliable and robust method. The proposed method yielded detection limits very low which ranges from 0.02 to 0.4 microg l(-1) and a relative standard deviation of ca. 7.5%. Finally, the method was validated with the US Environmental Protection Agency (EPA) method 552.2 for the analysis of HAAs in drinking and swimming pool water samples containing concentrations of HAAs that must be higher than 10 microg l(-1) due to the fact that this method is less sensitive than the proposed one.

  11. Determination of organochlorine pesticides in water samples by dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry.

    PubMed

    Cortada, Carol; Vidal, Lorena; Pastor, Raul; Santiago, Noemi; Canals, Antonio

    2009-09-07

    A rapid and simple dispersive liquid-liquid microextraction (DLLME) has been developed to preconcentrate eighteen organochlorine pesticides (OCPs) from water samples prior to analysis by gas chromatography-mass spectrometry (GC-MS). The studied variables were extraction solvent type and volume, disperser solvent type and volume, aqueous sample volume and temperature. The optimum experimental conditions of the proposed DLLME method were: a mixture of 10 microL tetrachloroethylene (extraction solvent) and 1 mL acetone (disperser solvent) exposed for 30 s to 10 mL of the aqueous sample at room temperature (20 degrees C). Centrifugation of cloudy solution was carried out at 2300 rpm for 3 min to allow phases separation. Finally, 2 microL of extractant was recovered and injected into the GC-MS instrument. Under the optimum conditions, the enrichment factors ranged between 46 and 316. The calculated calibration curves gave a high-level linearity for all target analytes with correlation coefficients ranging between 0.9967 and 0.9999. The repeatability of the proposed method, expressed as relative standard deviation, varied between 5% and 15% (n=8), and the detection limits were in the range of 1-25 ng L(-1). The LOD values obtained are able to detect these OCPs in aqueous matrices as required by EPA methods 525.2 and 625. Analysis of spiked real water samples revealed that the matrix had no effect on extraction for river, surface and tap waters; however, urban wastewater sample shown a little effect for five out of eighteen analytes.

  12. Organic synthesis reactions on-water at the organic-liquid water interface.

    PubMed

    Butler, Richard N; Coyne, Anthony G

    2016-10-25

    Organic reactions that occur at the water interface for water-insoluble compounds, and reactions in water solution for water soluble compounds, has added a powerful dimension to prospects for organic synthesis under more beneficial economic and environmental conditions. Many organic molecules are partially soluble in water and reactions that appear as heterogeneous mixtures and suspensions may involve on-water and in-water reaction modes occurring simultaneously. The behavior of water molecules and organic molecules at this interface is discussed in the light of reported theoretical and experimental studies. The on-water catalytic effect, relative to neat reactions or organic solvents, ranges from factors of several hundred times to 1-2 times and it depends on the properties of reactant compounds. In some cases when on-water reactions produce quantitative yields of water-insoluble products they can reach ideal synthetic aspirations.

  13. 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.

  14. 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

    2016-01-01

    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 50μL 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.

  15. 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

  16. 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.

  17. 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.

  18. Water distribution at solid/liquid interfaces visualized by frequency modulation atomic force microscopy

    PubMed Central

    Fukuma, Takeshi

    2010-01-01

    Interfacial phenomena at solid/water interfaces play an important role in a wide range of industrial technologies and biological processes. However, it has been a great challenge to directly probe the molecular-scale behavior of water at solid/water interfaces. Recently, there have been tremendous advancements in frequency modulation atomic force microscopy (FM-AFM), enabling its operation in liquids with atomic resolution. The high spatial and force resolutions of FM-AFM have enabled the visualization of one-dimensional (1D) profiles of the hydration force, two-dimensional (2D) images of hydration layers and three-dimensional (3D) images of the water distribution at solid/water interfaces. Here I present an overview of the recent advances in FM-AFM instrumentation and its applications to the study of solid/water interfaces. PMID:27877337

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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.

  20. 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.

  1. 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 20 µL 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 8.1 ng L(-1) were obtained, depending on the compound. Concentrations of between 9 and 47 ng L(-1) for some analytes were obtained in the analysis of ten samples.

  2. Extraction of hydroxyaromatic compounds in river water by liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase.

    PubMed

    Melwanki, Mahaveer B; Huang, Shang-Da

    2006-08-01

    Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase technique is described for the extraction of six hydroxyaromatic compounds in river water using a disposable and ready to use hollow fiber. Separation and quantitative analyses were performed using LC with UV detection at 254 nm. Analytes were extracted from the acidified sample solution (donor phase) into the organic solvent impregnated in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10 microL LC syringe. The acceptor phase was sandwitched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber using a syringe pump. This movement provides a fresh acceptor phase to come in contact with the organic phase and thus enhancing extraction kinetics thereby leading to the improvement in enrichment of the analytes. The microcap separates the acceptor phase and the donor phase in addition to being partially responsible for mass transfer of the analytes from the donor solution to the acceptor solution. Under stirring, a fresh donor phase will enter through the open end of the fiber that will also contribute to the mass transfer. Various parameters affecting the extraction efficiency viz type of organic solvent, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. RSD (3.9-5.6%), correlation coefficient (0.995-0.997), detection limit (2.0-51.2 ng/mL), enrichment factor (339-630), relative recovery (93.2-97.9%), and absolute recovery (33.9-63.0%) have also been investigated. The developed method was applied for the analysis of river water.

  3. Experimental evidence for the formation of liquid saline water on Mars.

    PubMed

    Fischer, Erik; Martínez, Germán M; Elliott, Harvey M; Rennó, Nilton O

    2014-07-16

    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.

  4. Slow dielectric response of Debye-type in water and other hydrogen bonded liquids

    NASA Astrophysics Data System (ADS)

    Jansson, Helén; Bergman, Rikard; Swenson, Jan

    2010-05-01

    The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related α-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular.

  5. Hybrid quantum/classical simulation of the vibrational relaxation of the bend fundamental in liquid water.

    PubMed

    Bastida, Adolfo; Zúñiga, José; Requena, Alberto; Miguel, Beatriz

    2009-11-28

    The Ehrenfest method with quantum corrections is used to describe the vibrational relaxation of the bend fundamental in liquid water. All the vibrational degrees of freedom of the water molecules are described using quantum mechanics, while the remaining translational and rotational degrees of freedom are described classically. The relaxation time obtained compares well with experiment and with relaxation times calculated using other theoretical approximations. The presence of resonant intermolecular vibrational energy (VV) transfer is established with a maximum percentage of excited molecules, different from the initial one, of 9.2%. It is found through an effective kinetic fit that two VV transfers occur before relaxation of water to the vibrational ground state.

  6. Structural and dipolar fluctuations in liquid water: A Car-Parrinello molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Skarmoutsos, Ioannis; Masia, Marco; Guardia, Elvira

    2016-03-01

    A Car-Parrinello molecular dynamics simulation was performed to investigate the local tetrahedral order, molecular dipole fluctuations and their interrelation with hydrogen bonding in liquid water. Water molecules were classified in three types, exhibiting low, intermediate and high tetrahedral order. Transitions from low to high tetrahedrally ordered structures take place only through transitions to the intermediate state. The molecular dipole moments depend strongly on the tetrahedral order and hydrogen bonding. The average dipole moment of water molecules with a strong tetrahedral order around them comes in excellent agreement with previous estimations of the dipole moment of ice Ih molecules.

  7. Interaction of monovalent ions with the water liquid-vapor interface - A molecular dynamics study

    NASA Technical Reports Server (NTRS)

    Wilson, Michael A.; Pohorille, Andrew

    1991-01-01

    Results of molecular dynamics calculations are presented for a series of ions at infinite dilution near the water liquid-vapor interface. The free energies of ion transfer from the bulk to the interface are discussed, as are the accompanying changes of water structure at the surface and ion mobilities as a function of their proximity to the interface. It is shown that simple dielectric models do not provide an accurate description of ions at the water surface. The results of the study should be useful in the development of better models incorporating the shape and molecular structure of the interface.

  8. Behavior of supercooled aqueous solutions stemming from hidden liquid–liquid transition in water

    SciTech Connect

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid–liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid–liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H{sub 2}O-NaCl and H{sub 2}O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid–liquid transition. We elucidate the non-conserved nature of the order parameter (extent of “reaction” between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  9. 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.

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

    PubMed

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

    2011-09-01

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

  11. Purification of inkjet ink from water using liquid phase, electric discharge polymerization and cellulosic membrane filtration.

    PubMed

    Jordan, Alexander T; Hsieh, Jeffery S; Lee, Daniel T

    2013-01-01

    A method to separate inkjet ink from water was developed using a liquid phase, electric discharge process. The liquid phase, electric discharge process with filtration or sedimentation was shown to remove 97% of inkjet ink from solutions containing between 0.1-0.8 g/L and was consistent over a range of treatment conditions. Additionally, particle size analysis of treated allyl alcohol and treated propanol confirmed the electric discharge treatment has a polymerization mechanism, and small molecule analysis of treated methanol using gas chromatography and mass spectroscopy confirmed the mechanism was free radical initiated polymerization.

  12. 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.

  13. A New Water-based Liquid Scintillator for Large Neutrino Physics

    NASA Astrophysics Data System (ADS)

    Yeh, Minfang

    2012-03-01

    A new type of scintillating liquid based on water has been developed at Brookhaven National Laboratory (Chemistry & Physics). The concept, preparation, and properties of this liquid, and how it could be used for a very large, but economical detector will be discussed in the talk. The applications of such a detector range from fundamental physics such as nucleon decay and neutrino physics to physics with broader application such as neutron detection. We will briefly describe the scientific requirements of these applications, and how they can be satisfied by this new material.

  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. 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

  16. Heat-transfer resistance at solid-liquid interfaces: a tool for the detection of single-nucleotide polymorphisms in DNA.

    PubMed

    van Grinsven, Bart; Vanden Bon, Natalie; Strauven, Hannelore; Grieten, Lars; Murib, Mohammed; Monroy, Kathia L Jiménez; Janssens, Stoffel D; Haenen, Ken; Schöning, Michael J; Vermeeren, Veronique; Ameloot, Marcel; Michiels, Luc; Thoelen, Ronald; De Ceuninck, Ward; Wagner, Patrick

    2012-03-27

    In this article, we report on the heat-transfer resistance at interfaces as a novel, denaturation-based method to detect single-nucleotide polymorphisms in DNA. We observed that a molecular brush of double-stranded DNA grafted onto synthetic diamond surfaces does not notably affect the heat-transfer resistance at the solid-to-liquid interface. In contrast to this, molecular brushes of single-stranded DNA cause, surprisingly, a substantially higher heat-transfer resistance and behave like a thermally insulating layer. This effect can be utilized to identify ds-DNA melting temperatures via the switching from low- to high heat-transfer resistance. The melting temperatures identified with this method for different DNA duplexes (29 base pairs without and with built-in mutations) correlate nicely with data calculated by modeling. The method is fast, label-free (without the need for fluorescent or radioactive markers), allows for repetitive measurements, and can also be extended toward array formats. Reference measurements by confocal fluorescence microscopy and impedance spectroscopy confirm that the switching of heat-transfer resistance upon denaturation is indeed related to the thermal on-chip denaturation of DNA.

  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

    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.

  18. Site-site direct correlation functions for three popular molecular models of liquid water.

    PubMed

    Zhao, Shuangliang; Liu, Yu; Liu, Honglai; Wu, Jianzhong

    2013-08-14

    Direct correlation functions (DCFs) play a pivotal role in the applications of classical density functional theory (DFT) to addressing the thermodynamic properties of inhomogeneous systems beyond the local-density or mean-field approximations. Whereas numerous studies have been dedicated to the radial distribution functions of liquid water--the most important solvent on earth, relatively little attention has been given to the site-site DCFs. The water DCFs are long-ranged and difficult to calculate directly by simulation, and the predictions from conventional liquid-state theories have been rarely calibrated. Here we report a computational procedure for accurate evaluation of the site-site DCFs of liquid water based on three popular molecular models (viz., SPC, SPC∕E, and TIP3P). The numerical results provide a benchmark for calibration of conventional liquid-state theories and fresh insights into development of new DFT methods. We show that: (1) the long-range behavior of the site-site DCFs depends on both the molecular model and the thermodynamic condition; (2) the asymptotic limit of DCFs at large distance does not follow the mean-spherical approximation (MSA); (3) individual site-site DCFs are long ranged (~40 nm) but a summation of all DCF pairs exhibits only short-range behavior (~1 nm or a few water diameters); (4) the site-site bridge correlation functions behave as the DCFs, i.e., they are also long-ranged while the summation of all bridge correlation functions is short ranged. Our analytical and numerical analyses of the DCFs provide some simple strategies for possible improvement of the numerical performance of conventional liquid-state theories.

  19. 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.

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

    SciTech Connect

    Taleyarkhan, R.P.; Gulec, K.; West, C.D.; Haines, J.

    1998-09-01

    It is well-known that fluids (like solids) will break apart or form voids when put under sufficient tension. The present study has been motivated by the need to evaluate the impact of fluid cavitation in spallation neutron source target systems, more specifically for the proposed 1-MW Spallation Neutron Source (SNS) project, which is being designed in collaboration between Oak Ridge National Laboratory (ORNL), Los Alamos National Laboratory, Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and Argonne National Laboratory. Indeed, results of SNS-specific simulations have indicated that the onset of cavitation could play a very significant role in reducing imposed stresses in structural components of the SNS. In general, the cavitation of fluids is target systems is important to consider for a variety of reasons. Its occurrence can have significant impact on heat transfer, pressure pulse generation, fluid jetting on to structures, surface erosion, stresses induced in enclosures, etc. Therefore, it is important to evaluate the threshold pressure under which the fluid in tension will undergo cavitation. Another major aspect concerns the possible onset of cavitation in an oscillating pressure field; i.e., one would need to know if fluids such as mercury and water will cavitate if the imposed tensile pressure in the fluid is of short duration. If indeed it takes sufficiently long for cavitation bubbles to nucleate, then it would be possible to disregard the complexities involved with addressing cavitation-related issues. This paper provides an overview of preliminary work done to date to derive information on cavitation onset in a relatively static and in a high-frequency environment.

  1. Self-assembly of azobenzene bilayer membranes in binary ionic liquid-water nanostructured media.

    PubMed

    Kang, Tejwant Singh; Ishiba, Keita; Morikawa, Masa-aki; Kimizuka, Nobuo

    2014-03-11

    Anionic azobenzene-containing amphiphile 1 (sodium 4-[4-(N-methyl-N-dodecylamino)phenylazo]benzenesulfonate) forms ordered bilayer membranes in binary ionic liquid (1-ethyl-3-methylimidazolium ethyl sulfate, [C2mim][C2OSO3])-water mixtures. The binary [C2mim][C2OSO3]-water mixture is macroscopically homogeneous at any mixing ratio; however, it possesses fluctuating nanodomains of [C2mim][C2OSO3] molecules as observed by dynamic light scattering (DLS). These nanodomains show reversible heat-induced mixing behavior with water. Although the amphiphile 1 is substantially insoluble in pure water, it is dispersible in the [C2mim][C2OSO3]-water mixtures. The concentration of [C2mim][C2OSO3] and temperature exert significant influences on the self-assembling characteristics of 1 in the binary media, as shown by DLS, transmission electron microscopy (TEM), UV-vis spectroscopy, and zeta-potential measurements. Bilayer membranes with rod- or dotlike nanostructures were formed at a lower content of [C2mim][C2OSO3] (2-30 v/v %), in which azobenzene chromophores adopt parallel molecular orientation regardless of temperature. In contrast, when the content of [C2mim][C2OSO3] is increased above 60 v/v %, azobenzene bilayers showed thermally reversible gel-to-liquid crystalline phase transition. The self-assembly of azobenzene amphiphiles is tunable depending on the volume fraction of [C2mim][C2OSO3] and temperature, which are associated with the solvation by nanoclusters in the binary [C2mim][C2OSO3]-water media. These observations clearly indicate that mixtures of water-soluble ionic liquids and water provide unique and valiant environments for ordered molecular self-assembly.

  2. Hydrogen bond network topology in liquid water and methanol: a graph theory approach.

    PubMed

    Bakó, Imre; Bencsura, Akos; Hermannson, Kersti; Bálint, Szabolcs; Grósz, Tamás; Chihaia, Viorel; Oláh, Julianna

    2013-09-28

    Networks are increasingly recognized as important building blocks of various systems in nature and society. Water is known to possess an extended hydrogen bond network, in which the individual bonds are broken in the sub-picosecond range and still the network structure remains intact. We investigated and compared the topological properties of liquid water and methanol at various temperatures using concepts derived within the framework of graph and network theory (neighbour number and cycle size distribution, the distribution of local cyclic and local bonding coefficients, Laplacian spectra of the network, inverse participation ratio distribution of the eigenvalues and average localization distribution of a node) and compared them to small world and Erdős-Rényi random networks. Various characteristic properties (e.g. the local cyclic and bonding coefficients) of the network in liquid water could be reproduced by small world and/or Erdős-Rényi networks, but the ring size distribution of water is unique and none of the studied graph models could describe it. Using the inverse participation ratio of the Laplacian eigenvectors we characterized the network inhomogeneities found in water and showed that similar phenomena can be observed in Erdős-Rényi and small world graphs. We demonstrated that the topological properties of the hydrogen bond network found in liquid water systematically change with the temperature and that increasing temperature leads to a broader ring size distribution. We applied the studied topological indices to the network of water molecules with four hydrogen bonds, and showed that at low temperature (250 K) these molecules form a percolated or nearly-percolated network, while at ambient or high temperatures only small clusters of four-hydrogen bonded water molecules exist.

  3. ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water.

    PubMed

    Banerjee, D; Bhat, S N; Bhat, S V; Leporini, D

    2009-07-14

    Using electron spin resonance spectroscopy (ESR), we measure the rotational mobility of probe molecules highly diluted in deeply supercooled bulk water and negligibly constrained by the possible ice fraction. The mobility increases above the putative glass transition temperature of water, T(g) = 136 K, and smoothly connects to the thermodynamically stable region by traversing the so called "no man's land" (the range 150-235 K), where it is believed that the homogeneous nucleation of ice suppresses the liquid water. Two coexisting fractions of the probe molecules are evidenced. The 2 fractions exhibit different mobility and fragility; the slower one is thermally activated (low fragility) and is larger at low temperatures below a fragile-to-strong dynamic cross-over at approximately 225 K. The reorientation of the probe molecules decouples from the viscosity below approximately 225 K. The translational diffusion of water exhibits a corresponding decoupling at the same temperature [Chen S-H, et al. (2006) The violation of the Stokes-Einstein relation in supercooled water. Proc Natl Acad Sci USA 103:12974-12978]. The present findings are consistent with key issues concerning both the statics and the dynamics of supercooled water, namely the large structural fluctuations [Poole PH, Sciortino F, Essmann U, Stanley HE (1992) Phase behavior of metastable water. Nature 360:324-328] and the fragile-to-strong dynamic cross-over at approximately 228 K [Ito K, Moynihan CT, Angell CA (1999) Thermodynamic determination of fragility in liquids and a fragile-to-strong liquid transition in water. Nature 398:492-494].

  4. 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 μg/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.

  5. Structural properties of geminal dicationic ionic liquid/water mixtures: a theoretical and experimental insight.

    PubMed

    Serva, Alessandra; Migliorati, Valentina; Lapi, Andrea; Aquilanti, Giuliana; Arcovito, Alessandro; D'Angelo, Paola

    2016-06-28

    The structural behavior of geminal dicationic ionic liquid 1,n-bis[3-methylimidazolium-1-yl] alkane bromide ([Cn(mim)2]Br2)/water mixtures has been studied using extended X-ray absorption fine structure (EXAFS) spectroscopy in combination with molecular dynamics (MD) simulations. The properties of the mixtures are investigated as a function of both water concentration and alkyl-bridge chain length. The very good agreement between the EXAFS experimental data and the theoretical curves calculated from the MD structural results has proven the validity of the theoretical framework used for all of the investigated systems. In all the solutions the water molecules are preferentially coordinated with the Br(-) ion, even if a complex network of interactions among dications, anions and water molecules takes place. The local molecular arrangement around the bromide ion is found to change with increasing water content, as more and more water molecules are accomodated in the Br(-) first coordination shell. Moreover, with the decrease of the alkyl-bridge chain length, the interactions between dications and anions increase, with Br(-) forming a bridge between the two imidazolium rings of the same dication. On the other hand, in [Cn(mim)2]Br2/water mixtures with long alkyl-bridge chains peculiar internal arrangements of the dications are found, leading to different structural features of geminal dicationic ionic liquids as compared to their monocationic counterparts.

  6. 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.

  7. 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

    2016-01-01

    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, 250μL 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 16.9-169μg 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 6.01μgL(-)(1) of iodide, respectively. The suggested procedure was applied for determination of iodide in real mineral water samples.

  8. Application of chemometric assisted dispersive liquid-liquid microextraction to the determination of personal care products in natural waters.

    PubMed

    Panagiotou, Aikaterini N; Sakkas, Vasilios A; Albanis, Triantafyllos A

    2009-09-07

    A rapid and simple method for the determination of two phthalates and five polycyclic musks in water samples using dispersive liquid-liquid microextraction (DLLME) mated to chemometrics and coupled to GC-MS was developed. Volume of extraction (CCl4) and disperser solvent (MeOH), pH, ionic strength, extraction time, centrifugation time as well as centrifugation speed were optimized in a 2(7-4) Plackett-Burman design. The obtained significant factors were optimized by using a central composite design (CCD) and the quadratic model between the dependent and the independent variables was built. The optimum experimental conditions of the proposed method were: 250 microL carbon tetrachloride, 0.62 mL methanol, 7.5 min centrifugation time, natural pH containing 0% (w/v) NaCl, while keeping centrifugation speed fixed at 4000 rpm. The calculated calibration curves gave high-level linearity for all target analytes with correlation coefficients ranging between 0.9970 and 0.9992. The repeatability and reproducibility of the proposed method, expressed as relative standard deviation, varied between 2.6% to 9.7% and 5.7% to 12.2%, respectively. The obtained LOD values were in the range of 8-63 ng L(-1).

  9. 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.

  10. Structure of water at zwitterionic copolymer film-liquid water interfaces as examined by the sum frequency generation method.

    PubMed

    Kondo, Takuya; Nomura, Kouji; Gemmei-Ide, Makoto; Kitano, Hiromi; Noguchi, Hidenori; Uosaki, Kohei; Saruwatari, Yoshiyuki

    2014-01-01

    A copolymer film composed of zwitterionic carboxymethylbetaine (CMB) and n-butyl methacrylate (BMA), Poly(CMB-r-BMA), was cast on a flat plane of an octadecyltrichlorosilane (ODS)-modified fused quartz prism with a semi-cylindrical shape. CH stretching of the polymer film and O-H stretching of water at the surface of the film were examined using the sum frequency generation (SFG) technique. The C-H stretching band of the cast film, indicating a gauche defect of the film, was affected by the contact medium including dry nitrogen, water vapor-saturated nitrogen and liquid water. In contrast, the C-H stretching of an octadecyl group introduced onto the quartz prism for stable attachment of the cast film was not significantly changed by the contact medium. The O-H stretching band indicated that water molecules at the surface of the Poly(CMB-r-BMA) film in contact with liquid water were not greatly oriented in comparison with those at the surfaces of a bare prism, an ODS SAM-modified prism, and a prism covered with a PolyBMA film or a copolymer film of BMA and methacrylic acid or 2-(dimethylamino)ethyl methacrylate. A similar small perturbation of the structure of water was previously observed in the vicinity of water-soluble zwitterionic polymers and zwitterionic copolymer films using Raman and attenuated total reflection infrared spectroscopies, respectively. A distinct effect of charge neutralization to diminish the perturbation of the structure of interfacial water around polymer materials was suggested.

  11. A new 1,3-dibutylimidazolium hexafluorophosphate ionic liquid-based dispersive liquid-liquid microextraction to determine organophosphorus pesticides in water and fruit samples by high-performance liquid chromatography.

    PubMed

    He, Lijun; Luo, Xianli; Jiang, Xiuming; Qu, Lingbo

    2010-07-30

    The paper described a new ionic liquid, 1,3-dibutylimidazolium hexafluorophosphate, as extraction solvent for extraction and preconcentration of organophosphorus pesticides (fenitrothion, parathion, fenthion and phoxim) from water and fruit samples by dispersive liquid-liquid microextraction combined with high-performance liquid chromatography. The effects of experimental parameters, such as extraction solvent volume, disperser solvent and its volume, extraction and centrifugal time, sample pH, extraction temperature and salt addition, on the extraction efficiency were investigated. An extraction recovery of over 75% and enrichment factor of over 300-fold were obtained under the optimum conditions. The linearity relationship was also observed in the range of 5-1000 microgL(-1) with the correlation coefficients (r(2)) ranging from 0.9988 to 0.9999. Limits of detection were 0.01-0.05 microgL(-1) for four analytes. The relative standard deviations at spiking three different concentration levels of 20, 100 and 500 microgL(-1) varied from 1.3-2.7, 1.4-1.9 and 1.1-1.7% (n=7), respectively. Three real samples including tap water, Yellow River water and pear spiked at three concentration levels were analyzed and yielded recoveries ranging from 92.7-109.1, 95.0-108.2 and 91.2-108.1%, respectively.

  12. 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

  13. Estrogenic compounds determination in water samples by dispersive liquid-liquid microextraction and micellar electrokinetic chromatography coupled to mass spectrometry.

    PubMed

    D'Orazio, Giovanni; Asensio-Ramos, María; Hernández-Borges, Javier; Fanali, Salvatore; Rodríguez-Delgado, Miguel Ángel

    2014-05-30

    In this work, a group of 12 estrogenic compounds, i.e., four natural sexual hormones (estrone, 17β-estradiol, 17α-estradiol and estriol), an exoestrogen (17α-ethynylestradiol), a synthetic stilbene (dienestrol), a mycotoxin (zearalenone) and some of their major metabolites (2-methoxyestradiol, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol) have been separated and determined by micellar electrokinetic chromatography (MEKC) coupled to electrospray ion trap mass spectrometry. For this purpose, a background electrolyte containing an aqueous solution of 45 mM of perfluorooctanoic acid (PFOA) adjusted to pH 9.0 with an ammonia solution, as MS friendly surfactant, and methanol (10% (v/v)), as organic modifier, was used. To further increase the sensitivity, normal stacking mode was applied by injecting the sample dissolved in an aqueous solution of 11.5mM of ammonium PFO (APFO) at pH 9.0 containing 10% (v/v) of methanol for 25s. Dispersive liquid-liquid microextraction, using 110 μL of chloroform and 500 μL of acetonitrile as extraction and dispersion solvents, respectively, was employed to extract and preconcentrate the target analytes from different types of environmental water samples (mineral, run-off and wastewater) containing 30% (w/v) NaCl and adjusted to pH 3.0 with 1M HCl. The limits of detection achieved were in the range 0.04-1.10 μg/L. The whole method was validated in terms of linearity, precision, recovery and matrix effect for each type of water, showing determination coefficients higher than 0.992 for matrix-matched calibration and absolute recoveries in the range 43-91%.

  14. Impact of water vapour and carbon dioxide on surface composition of C{sub 3}A polymorphs studied by X-ray photoelectron spectroscopy

    SciTech Connect

    Dubina, E.; Plank, J.; Black, L.

    2015-07-15

    The surface specific analytical method, X-ray photoelectron spectroscopy (XPS), has been used to study the effects of water vapour and CO{sub 2} on the cubic and orthorhombic polymorphs of C{sub 3}A. Significant differences between the two polymorphs were observed in the XPS spectra. Upon exposure to water vapour, both polymorphs produced C{sub 4}AH{sub 13} on their surfaces. Additionally, the sodium-doped o-C{sub 3}A developed NaOH and traces of C{sub 3}AH{sub 6} on its surface. Subsequent carbonation yielded mono carboaluminate on both polymorphs. Large amounts of Na{sub 2}CO{sub 3} also formed on the surface of o-C{sub 3}A as a result of carbonation of NaOH. Furthermore, the extent of carbonation was much more pronounced for o-C{sub 3}A{sub o} than for c-C{sub 3}A.

  15. 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.

  16. Imbibition in mesoporous silica: rheological concepts and experiments on water and a liquid crystal.

    PubMed

    Gruener, Simon; Huber, Patrick

    2011-05-11

    We present, along with some fundamental concepts regarding imbibition of liquids in porous hosts, an experimental, gravimetric study on the capillarity-driven invasion dynamics of water and of the rod-like liquid crystal octyloxycyanobiphenyl (8OCB) in networks of pores a few nanometers across in monolithic silica glass (Vycor). We observe, in agreement with theoretical predictions, square root of time invasion dynamics and a sticky velocity boundary condition for both liquids investigated. Temperature-dependent spontaneous imbibition experiments on 8OCB reveal the existence of a paranematic phase due to the molecular alignment induced by the pore walls even at temperatures well beyond the clearing point. The ever present velocity gradient in the pores is likely to further enhance this ordering phenomenon and prevent any layering in molecular stacks, eventually resulting in a suppression of the smectic phase in favor of the nematic phase.

  17. Cloud liquid water path and radiative feedbacks over the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bodas-Salcedo, A.; Andrews, T.; Karmalkar, A. V.; Ringer, M. A.

    2016-10-01

    Climate models show a robust shortwave negative feedback in the midlatitude oceans in climate change simulations. This feedback is commonly attributed to an increase in cloud optical depth due to ice to liquid phase change as the climate warms. Here we use a cyclone compositing technique to show that the models' cloud liquid water path (LWP) response is strongly dependent on cloud regime. The radiative and LWP responses are not as tightly coupled as a zonal-mean analysis would suggest, implying that the physical mechanisms that control the overall LWP response are not necessarily responsible for the radiative response. The area of the cyclone dominated by low-level stratiform and shallow convective clouds plays a dominant role in the radiative response. Since these are mostly supercooled liquid clouds, the strength of a negative cloud phase feedback in the real world should be smaller than the one predicted by current models.

  18. Liquid interfacial water and brines in the upper surface of Mars

    NASA Astrophysics Data System (ADS)

    Moehlmann, Diedrich

    2013-04-01

    Liquid interfacial water and brines in the upper surface of Mars Diedrich T.F. Möhlmann DLR Institut für Planetenforschung, Rutherfordstr. 2, D - 12489 Berlin, Germany dirk.moehlmann@dlr.de Interfacial water films and numerous brines are known to remain liquid at temperatures far below 0° C. The physical processes behind are described in some detail. Deliquescence, i.e. the liquefaction of hygroscopic salts at the threshold of a specific "Deliquescence Relative Humidity", is shown to be that process, which on present Mars supports the formation of stable interfacial water and bulk liquids in form of temporary brines on and in a salty upper surface of present Mars in a diurnally temporary and repetitive process. Temperature and relative humidity are the governing conditions for deliquescence (and the counterpart "efflorescence") to evolve. The current thermo-dynamical conditions on Mars support these processes to evolve on present Mars. The deliquescence-driven presence of liquid brines in the soil of the upper surface of Mars can expected to be followed by physical and chemical processes like "surface cementation", down-slope flows, and physical and chemical weathering processes. A remarkable and possibly also biologically relevant evolution towards internally interfacial water bearing structures of dendritic capillaries is related to their freezing - thawing driven formation. The internal walls of these network-pores or -tubes can be covered by films of interfacial water, providing that way possibly habitable crack-systems in soil and rock. These evolutionary processes of networks, driven by their tip-growth, can expected to be ongoing also at present.

  19. Evidence of the existence of the low-density liquid phase in supercooled, confined water.

    PubMed

    Mallamace, Francesco; Broccio, Matteo; Corsaro, Carmelo; Faraone, Antonio; Majolino, Domenico; Venuti, Valentina; Liu, Li; Mou, Chung-Yuan; Chen, Sow-Hsin

    2007-01-09

    By confining water in a nanoporous structure so narrow that the liquid could not freeze, it is possible to study properties of this previously undescribed system well below its homogeneous nucleation temperature TH = 231 K. Using this trick, we were able to study, by means of a Fourier transform infrared spectroscopy, vibrational spectra (HOH bending and OH-stretching modes) of deeply supercooled water in the temperature range 183 < T < 273 K. We observed, upon decreasing temperature, the building up of a new population of hydrogen-bonded oscillators centered around 3,120 cm(-1), the contribution of which progressively dominates the spectra as one enters into the deeply supercooled regime. We determined that the fractional weight of this spectral component reaches 50% just at the temperature, TL approximately 225 K, where the confined water shows a fragile-to-strong dynamic cross-over phenomenon [Ito, K., Moynihan, C. T., Angell, C. A. (1999) Nature 398:492-494]. Furthermore, the fact that the corresponding OH stretching spectral peak position of the low-density-amorphous solid water occurs exactly at 3,120 cm(-1) [Sivakumar, T. C., Rice, S. A., Sceats, M. G. (1978) J. Chem. Phys. 69:3468-3476.] strongly suggests that these oscillators originate from existence of the low-density-liquid phase derived from the occurrence of the first-order liquid-liquid (LL) phase transition and the associated LL critical point in supercooled water proposed earlier by a computer molecular dynamics simulation [Poole, P. H., Sciortino, F., Essmann, U., Stanley, H. E. (1992) Nature 360:324-328].

  20. 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.

  1. 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.

  2. 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

  3. 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 μm 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 μm 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 μm ash, which adhered by electrostatic forces and sparse liquid bridges. From this, we

  4. 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.

  5. Liquid-crystal thermometer use in pediatric office counseling about tap water burn prevention.

    PubMed

    Katcher, M L; Landry, G L; Shapiro, M M

    1989-05-01

    Tap water scald burns are an important topic of injury prevention in pediatricians' offices. Consecutive pediatric clinic clients, randomized to two groups, received an informational pamphlet, a one-minute discussion about tap water safety, and a baseline questionnaire. The first group also received a liquid-crystal thermometer for testing maximum hot tap water temperature. One month later in a follow-up telephone interview (n = 503), the impact of the added thermometer on knowledge regarding scalding, temperature testing, and thermostat lowering was assessed. Approximately 80% of each group read the pamphlet. Reading the pamphlet was associated with greater temperature testing in the thermometer (T) group but not in the pamphlet only (P) group. Temperatures were checked by 46.4% of the T group but by only 23.0% of the P group (P less than .001). In the households in which the reported water temperature exceeded 54.4 degrees C (130 degrees F) and the water heater was accessible, 77.3% reported lowering the setting, independent of receiving the thermometer. The reliability of self-reported water temperature was assessed after 1 year by home visits. The use of relevant facilitating devices, such as a liquid-crystal thermometer, in-office anticipatory guidance efforts may increase behavioral compliance.

  6. Photochemical synthesis of silver particles in Tween 20/water/ionic liquid microemulsions.

    PubMed

    Harada, Masafumi; Kimura, Yoshifumi; Saijo, Kenji; Ogawa, Tetsuya; Isoda, Seiji

    2009-11-15

    Metal particles of silver (Ag) were synthesized by the photoreduction of silver perchlorate (AgClO(4)) in water-in-ionic liquid (ILs) microemulsions consisting of Tween 20, water and ionic liquids. The ILs were tetrafluoroborate anions associated with the cations 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF(4)]) and 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIm][BF(4)]). The time evolution of Ag particle formation by photoreduction using UV-irradiation was investigated by UV-Vis, cryo-TEM, extended X-ray absorption fine structure (EXAFS) and small angle X-ray scattering (SAXS) measurements. The average diameter of the metallic Ag particles prepared in the water-in-[BMIm][BF(4)] and water-in-[OMIm][BF(4)] microemulsions was estimated from TEM to be 8.9 and 4.9nm, respectively, which was consistent with that obtained from the SAXS analysis. Using Guinier plots in a low q-range (<0.16nm(-1)), we demonstrate that the average diameter of the water droplets that consisted of aggregates of ionic precursors of AgClO(4) before reduction and Ag particles after reduction, in the microemulsions, was estimated to be about 20-40nm. The diameter of the water droplets increased as a function of photoreduction time because of the formation of Ag particles and their aggregates. EXAFS analysis indicated that Ag(+) ions were completely reduced to Ag(0) atoms during the photoreduction, followed by the formation of larger Ag particles.

  7. Why many semiempirical molecular orbital theories fail for liquid water and how to fix them.

    PubMed

    Welborn, Matthew; Chen, Jiahao; Wang, Lee-Ping; Van Voorhis, Troy

    2015-05-05

    Water is an extremely important liquid for chemistry and the search for more accurate force fields for liquid water continues unabated. Neglect of diatomic differential overlap (NDDO) molecular orbital methods provide and intriguing generalization of classical force fields in this regard because they can account both for bond breaking and electronic polarization of molecules. However, we show that most standard NDDO methods fail for water because they give an incorrect description of hydrogen bonding, water's key structural feature. Using force matching, we design a reparameterized NDDO model and find that it qualitatively reproduces the experimental radial distribution function of water, as well as various monomer, dimer, and bulk properties that PM6 does not. This suggests that the apparent limitations of NDDO models are primarily due to poor parameterization and not to the NDDO approximations themselves. Finally, we identify the physical parameters that most influence the condensed phase properties. These results help to elucidate the chemistry that a semiempirical molecular orbital picture of water must capture. We conclude that properly parameterized NDDO models could be useful for simulations that require electronically detailed explicit solvent, including the calculation of redox potentials and simulation of charge transfer and photochemistry.

  8. 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.

  9. 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.

  10. Use of textile waste water along with liquid NPK fertilizer for production of wheat on saline sodic soils.

    PubMed

    Yaseen, Muhammad; Aziz, Muhammad Zahir; Jafar, Abdul Aleem; Naveed, Muhammad; Saleem, Muhammad

    2016-01-01

    A field experiment in collaboration with a private textile industry (Noor Fatima Fabrics Private (Ltd.), Faisalabad) was conducted to evaluate the effect of disposed water from bleaching unit, printing unit and end drain for improving growth and yield of wheat under saline sodic soil. Textile waste water along with canal water (control) was applied with and without liquid NPK fertilizer. The application of liquid NPK fertilizer with end drain waste water increased plant height, spike length, flag leaf length, root length, number of tillers (m(-2)), number of fertile tillers (m(-2)), 1000 grain weight, grain yield, straw yield and biological yield up to 21, 20, 20, 44, 17, 20, 14, 44, 40 and 41%, respectively compared to canal water (control). Similarly, the NPK uptake in grain was increased up to 15, 30 and 28%, respectively by liquid fertilizer treated end drain water as compare to canal water with liquid fertilizer. Moreover, concentration of different heavy metals particularly Cu, Cr, Pb and Cd was decreased in grains by application of waste water along with liquid NPK. The result may imply that waste water application along with liquid-NPK could be a novel approach for improving growth and yield of wheat in saline sodic soils.

  11. Improved solvent collection system for a dispersive liquid-liquid microextraction of organochlorine pesticides from water using low-density organic solvent.

    PubMed

    Chang, Chu-Chi; Wei, Shuo-Yang; Huang, Shang-Da

    2011-04-01

    In this study, the organochlorine pesticides (OCPs) levels in lake and tap water samples were determined by a dispersive liquid-liquid microextraction method using a low-density organic solvent and an improved solvent collection system (DLLME-ISCS). This method used a very small volume of a solvent of low toxicity (11  μL of 1-nonanol and 400  μL of methanol) to extract OCPs from 10  mL water samples prior to the analysis by GC. After centrifugation in the dispersive liquid-liquid microextraction, there was a liquid organic drop floating between the water surface and the glass wall of the centrifuge tube. The liquid organic drop (with some water phase) was transferred into a microtube (3  mm×15  mm) with a syringe. The organic and aqueous phases were separated in the microtube immediately. Then, 1  μL of the organic solvent (which was in the upper portion of liquid in the microtube) was easily collected by a syringe and injected into the GC-ECD system for the analysis. Under optimum conditions, the linear range of this method was 5-5000  ng/L for most of the analytes. The correlation coefficient was higher than 0.997. Enrichment factors ranged from 1309 to 3629. The relative recoveries ranged from 73 to 119% for lake water samples. The LODs of the method ranged from 0.7 to 9.4  ng/L. The precision of the method ranged from 1.0 to 10.8% for lake water.

  12. Differences and Similarity in the Dynamic and Acoustic Properties of Gas Microbubbles in Liquid Mercury and Water

    NASA Astrophysics Data System (ADS)

    Ida, Masato; Haga, Katsuhiro; Kogawa, Hiroyuki; Naoe, Takashi; Futakawa, Masatoshi

    2010-04-01

    Differences and similarities in the dynamics of microbubbles in liquid mercury and water are clarified and summarized in order to evaluate the validity and usefulness of experiments with water as an alternative to experiments with mercury. Pressure-wave induced cavitation in liquid mercury is of particular concern in the high-power pulsed neutron sources working in Japan and the U.S. Toward suppressing the pressure waves and cavitation, injection of gas microbubbles into liquid mercury has been attempted. However, many difficulties arise in mercury experiments mainly because liquid mercury is an opaque liquid. Hence we and collaborators have performed water experiments as an alternative, in conjunction with mercury experiments. In this paper, we discussed how we should use the result with water and how we can make the water experiments meaningful. The non-dimensional numbers of bubbly liquids and bubbles’ rise velocity, coalescence frequency, and response to heat input were investigated theoretically for both mercury and water. A suggestion was made to “see through” bubble distribution in flowing mercury from the result of water study, and a notable similarity was found in the effect of bubbles to absorb thermal expansion of the liquids.