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1

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

NASA Astrophysics Data System (ADS)

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

Mirgorod, Yu. A.

2015-01-01

2

Polyamorphism and polymorphism of a confined water monolayer: liquid-liquid critical point, liquid-crystal and crystal-crystal phase transitions  

NASA Astrophysics Data System (ADS)

Water is an anomalous liquid because its properties are different from those of the majority of liquids. Here, we first review what is anomalous about water. Then we study a many-body model for a water monolayer confined between hydrophobic plates in order to answer fundamental questions related to the origin of its anomalies and to predict new testable futures. In particular, we study by Monte Carlo simulations the low temperature phase diagram of the model. By finite size scaling, we find a liquid-liquid first order phase transition ending in a critical point (LLCP) in the region in which bulk water would be supercooled. We show that the LLCP belongs to the universality class of the two-dimensional (2D) Ising model in the limit of infinite walls. Next, we study the limit of stability of the liquid phase with respect to the crystal phases. To this goal we modify the model in order to characterize the crystal formation and find that the model has a crystal-crystal phase transition and that the LLCP is stable with respect to the liquid-crystal phase transition depending on the relative strength of the three-body interaction with respect to the rest of many-body interactions.

Bianco, Valentino; Vilanova, Oriol; Franzese, Giancarlo

2014-03-01

3

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

E-print Network

Water is an anomalous substance in many respects. Most liquids contract upon cooling. This is not the case of water, a liquid where the specific volume at ambient pressure starts to increase when cooledLiquid polymorphism and density anomaly in a three-dimensional associating lattice gas Mauricio

Barbosa, Marcia C. B.

4

Cloud Liquid Water Measurements  

E-print Network

#12;Wet Power Term Energy is transferred to heat droplets to to the boiling point and vaporize of Vaporization · cw - Specific Heat of Water · Tv - Boiling Temperature of Water · Ta ­ Ambient Temperature #12 of Vaporization · cw - Specific Heat of Water · Tv ­ Water Boiling Temperature Solve for Liquid Water Content · P

Delene, David J.

5

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

6

Liquid-liquid phase transition in water  

NASA Astrophysics Data System (ADS)

Water shows anomalies different from most of other materials. Different sceniaros have been proposed to explain water anomalies, among which the liquid-liquid phase transition (LLPT) is the most discussed one. It attributes water anomalies to the existence of a hypothesized liquid-liquid critical point (LLCP) buried deep in the supercooled region. We briefly review the recent experimental and theoretical progresses on the study of the LLPT in water. These studies include the discussion on the existence of the first order LLPT in supercooled water and the detection of liquid-liquid critical point. Simulational results of different water models for LLPT and the experimental evidence in confined water are also discussed.

Sun, ZhaoRu; Sun, Gang; Chen, YiXuan; Xu, LiMei

2014-05-01

7

Water: The Strangest Liquid  

SciTech Connect

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.

Nilsson, Anders

2009-02-24

8

Polymorphs in GeO2 Liquid  

NASA Astrophysics Data System (ADS)

Local structure in liquid GeO2 with density ranging from 3.56 to 5.89 g/cm3 has been investigated in MD model containing 1998 atoms. The simulation revealed that the germania liquid is composed of three species: GeO4, GeO5 and GeO6 with fraction varying with density. The density as well as volume fraction of voids can be expressed as a linear function of the fraction of those species. Low-density liquid is mainly consisted of GeO4 and has a large number of O- and Ge-voids (OV,GV) and very large void tube (LVT). This LVT contained most OVs and was spread over whole system. The low-density liquid differs from high-density liquid also in the oxygen linkage characteristics.

Hung, P. K.; Nhan, N. T.; Vinh, L. T.; Phuong, T. T. B.

9

Life's Little Essential: Liquid Water  

NSDL National Science Digital Library

Without liquid water, terrestrial life could not exist. All living organisms on Earth depend on water and its unique chemical and physical properties. In the search for life beyond Earth, scientists have focused their efforts on looking for signs of liquid water. This essay discusses the properties of liquid water that are conducive to life, pointing out that the biochemical reactions that sustain life need a fluid in order to operate, and that water is probably the best solvent in the universe.

10

Polymorphs in GeO 2 Liquid  

Microsoft Academic Search

Local structure in liquid GeO2 with density ranging from 3.56 to 5.89 g\\/cm3 has been investigated in MD model containing 1998 atoms. The simulation revealed that the germania liquid is composed of\\u000a three species: GeO4, GeO5 and GeO6 with fraction varying with density. The density as well as volume fraction of voids can be expressed as a linear function\\u000a of

P. K. Hung; N. T. Nhan; L. T. Vinh; T. T. B. Phuong

11

Liquid Assets: Sustainable Water Use  

NSDL National Science Digital Library

This video from a WPSU documentary Liquid Assets shows the transformation of Las Vegas water infrastructure. A desert community, Las Vegas is reducing water consumption and re-using wastewater, making optimal use of limited water resources.

WPSU

2008-11-20

12

Dissolving Different Liquids in Water  

NSDL National Science Digital Library

In this activity, students add different liquids to water and apply their working definition of dissolving to their observations. After observing isopropyl rubbing alcohol, vegetable oil, and corn syrup in water, students can conclude that while some liquids may dissolve in water, different liquids dissolve in water to different extents. There is a downloadable activity sheet that will be very helpful to educators, and will help students stay on track. An assessment sheet is also available on the activity page to keep track of students progress. There is also a step by step guide as to how to perform the experiment, and how to introduce it t the students.

James Kessler

2010-01-01

13

Liquid Assets: A Water System  

NSDL National Science Digital Library

This segment from a WPSU documentary Liquid Assets succinctly explains how water in New York journeys from its source to our faucets. Although water flows under our feet everyday, we are blissfully unaware of this service and take it for granted.

WPSU

2008-11-20

14

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

PubMed

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

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

2009-06-01

15

Static heterogeneities in liquid water  

NASA Astrophysics Data System (ADS)

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.

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

2004-10-01

16

Spontaneous liquid-liquid phase separation of water  

NASA Astrophysics Data System (ADS)

We report a molecular dynamics simulation demonstrating a fast spontaneous liquid-liquid phase separation of water and a subsequent slow crystallization to ice. It is found that supercooled water separates rapidly into low- and high-density domains so as to reduce the surface energy in the rectangular simulation cell at certain thermodynamic states. The liquid-liquid phase separation, which is about two orders of magnitude faster than the crystallization, suggests a possibility to observe this phenomenon experimentally.

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2014-02-01

17

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

PubMed Central

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). PMID:25716054

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

2015-01-01

18

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

NASA Astrophysics Data System (ADS)

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).

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

2015-02-01

19

Inhomogeneities of stratocumulus liquid water  

NASA Technical Reports Server (NTRS)

There is a growing body of observational evidence on inhomogeneous cloud structure, most recently from the extensive measurements of the FIRE field program. Knowledge of cloud structure is important because it strongly influences the cloud radiative properties, one of the major factors in determining the global energy balance. Current atmospheric circulation models use plane-parallel radiation, so that the liquid water in each gridbox is assumed to be uniform, which gives an unrealistically large albedo. In reality cloud liquid water occupies only a subset of each gridbox, greatly reducing the mean albedo. If future climate models are to treat the hydrological cycle in a manner consistent with energy balance, a better treatment of cloud liquid is needed. FIRE concentrated upon two cloud types of special interest: cirrus and marine stratocumulus. Cirrus tend to be high and optically thin, thus reducing the effective radiative temperature without increasing the albedo significantly, leading to an enhanced greenhouse heating. In contrast, marine stratocumulus are low and optically thick, thus producing a large increase in reflected radiation with a small change in emitted radiation, giving a net cooling which could potentially mitigate the expected greenhouse warming. The FIRE measurements in California stratocumulus during June and July of 1987 show variations in cloud liquid water on all scales. Such variations are associated with inhomogeneous entrainment, in which entrained dry air, rather than mixing uniformly with cloudy air, remains intact in blobs of all sizes, which decay only slowly by invasion of cloudy air. Two important stratocumulus observations are described, followed by a simple fractal model which reproduces these properties, and finally, the model radiative properties are discussed.

Cahalan, Robert F.; Snider, Jack B.

1990-01-01

20

Entropy-driven liquid-liquid transitions in supercooled water  

NASA Astrophysics Data System (ADS)

Twenty years ago it was suggested that the anomalous properties of supercooled water may be caused by a critical point that terminates a line of metastable liquid-liquid separation of lower-density and higher-density water. I describe a phenomenological model in which liquid water at low temperatures is viewed as an athermal solution of two hydrogen-bond network structures with different entropies and densities. Alternatively to the lattice-gas/regular solution model, in which fluid phase separation is driven by energy, the phase transition in the athermal two-state water is driven by entropy upon increasing the pressure, while the critical temperature is defined by the reaction equilibrium constant. The order parameter is associated with the entropy, while the ordering field is a combination of temperature and pressure. The model predicts the location of density maxima at the locus of a near-constant fraction of the lower-density structure. Another example of entropy-driven liquid polyamorphism is the transition between the structurally ordered ``Blue Phase III'' and disordered liquid in some chiral materials; this transition is experimentally accessible. I also discuss the application of the two-state model to binary solutions of supercooled water in which liquid-liquid transition may also become accessible to direct observation. Some atomistic ``water-like'' models such as mW, do not show liquid-liquid separation in the metastable liquid domain. However, even without actual liquid-liquid separation, the anomalies observed in MD simulations of mW can be accurately described by the entropy-driven nonideality of two molecular configurations, the same physics that presumably drives the liquid-liquid transition in real water.

Anisimov, Mikhail

2013-03-01

21

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

NASA Astrophysics Data System (ADS)

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], series edited by S. A. Rice (Wiley, New York, 2010).

Stanley, H. Eugene

2010-03-01

22

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

E-print Network

II. Properties of Water 1. Ice and Liquid water structure 2. Cohesion / Surface Tension 3. High and Properties Water's molecular structure and capacity to donate and accept hydrogen bonds give it unusual.6: Five Critical Properties of Water 1. Ice and liquid water structure Temperature 0C Temperature > 0C

Frey, Terry

23

Interconversion kinetic studies of betamethasone acetate polymorphs in water.  

PubMed

This study assessed the effect of polymers on the transformation of polymorphs of betamethasone acetate (BA) when suspended in water. The results showed that the polymers, in particular HPMC E5, retarded the transition of the forms Ialpha and Ibeta. However, the form Ialpha, as the metastable form, with the aid of HPMC E5, was preferred for BA suspension preparation through kinetic studies, while the form Ibeta was not suitable due to its instability in water. PMID:17012114

Ke, Xue; Ping, QiNeng; Liao, ZhengGen

2006-10-01

24

Proton Electrodynamics in Liquid Water  

E-print Network

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

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

2013-02-20

25

Electrokinetic Power Generation from Liquid Water Microjets  

SciTech Connect

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

Duffin, Andrew M.; Saykally, Richard J.

2008-02-15

26

Comment on "Spontaneous liquid-liquid phase separation of water"  

NASA Astrophysics Data System (ADS)

Yagasaki et al. [Phys. Rev. E 89, 020301 (2014), 10.1103/PhysRevE.89.020301] present results from a molecular dynamics trajectory illustrating coarsening of ice, which they interpret as evidence of transient coexistence between two distinct supercooled phases of liquid water. We point out that neither two distinct liquids nor criticality are demonstrated in this simulation study. Instead, the illustrated trajectory is consistent with coarsening behaviors analyzed and predicted in earlier work by others.

Limmer, David T.; Chandler, David

2015-01-01

27

Polymorphic transitions in n-hydrocarbon-water and n-alcohol-water binary systems  

NASA Astrophysics Data System (ADS)

The mixing of hydrocarbons and alcohols in an excess of water is explained by polymorphic transitions similar to crystallization in an ensemble of water clusters. Enthalpies of transitions of 4.90 0.07 and 2.2 0.3 kJ/mol are obtained for solutions of hydrocarbons and alcohols in an excess of water, respectively. It is concluded that the mixing of water in an excess of hydrocarbons and alcohols is similar to evaporation (the breaking of H-bonds) with an enthalpy of 34 1.4 kJ/mol. It is established that a polymorphic transition occurs between two binodals, and is accompanied by the emergence of microphases (concentration fluctuations) of alcohols in water. Binodals and spinodals in an excess of water and alcohol coincide for butyl and other higher alcohols.

Mirgorod, Yu. A.

2014-08-01

28

Evidence for Liquid Water on Comets  

NASA Technical Reports Server (NTRS)

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

Sheldon, Robert; Hoover, Richard

2005-01-01

29

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

Microsoft Academic Search

Polymorphous crystals of chlorozincate-choline chloride ionic liquid (IL) in different molar ratios were incubated at 5C 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(ZnCl2) (mole fraction of ZnCl2) over the range from 0.67 to 0.40. Crystal (a) (m.p. 45C) is

Yaodong Liu; Guozhong Wu; Mingying Qi

2005-01-01

30

Liquid Water Oceans in Ice Giants  

E-print Network

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

Sloane J. Wiktorowicz; Andrew P. Ingersoll

2006-09-26

31

Liquid chromatographic determination of water  

DOEpatents

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.

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

1990-11-13

32

Liquid chromatographic determination of water  

DOEpatents

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.

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

1990-11-13

33

Liquid Water Oceans in Ice Giants  

NASA Technical Reports Server (NTRS)

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

Wiktorowicz, Sloane J.; Ingersoll, Andrew P.

2007-01-01

34

Advancing into water's "no man's land": two liquid states?  

PubMed

A tale of two liquids? Liquid water exhibits many anomalous properties which are strongly amplified in the supercooled state. A possible explanation for the unusual behavior is a phase transition between two distinct metastable forms of liquid water at deeply supercooled conditions. A recent theoretical study has confirmed the existence of this liquid-liquid phase transition. PMID:25252122

Paschek, Dietmar; Ludwig, Ralf

2014-10-27

35

Polymorphs  

E-print Network

) ? Thermomechanical analysis (TMA) ? Microthermal analysis ? Isothermal Calorimetry 28 Differential Scanning Calorimetry Measures the heat flux as a function of temperature ? Premafloxacin Forms I and III ? Exothermic transitions suggest monotropic pairs I, II... by change in extinction. After rotation of the stage, extinction of polarized light is restored. From Nichols, Light microscopy, in Hilfiker, Polymorphism, Wiley-VCH (2005) Ch. 7 22 43 Thermomechanical Analysis Two major types ? Compression ? Allows...

Prankerd, Richard

2006-10-26

36

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

SciTech Connect

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.

Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria, E-mail: Valeria.Molinero@utah.edu [Department of Chemistry, The University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850 (United States)

2014-11-14

37

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

NASA Astrophysics Data System (ADS)

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, TBmax 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 TBmax 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.

Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria

2014-11-01

38

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

PubMed

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

Lupi, Laura; Kastelowitz, Noah; Molinero, Valeria

2014-11-14

39

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

NASA Astrophysics Data System (ADS)

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

Lascaris, Erik

40

Role of water in protein aggregation and amyloid polymorphism.  

PubMed

A variety of neurodegenerative diseases are associated with amyloid plaques, which begin as soluble protein oligomers but develop into amyloid fibrils. Our incomplete understanding of this process underscores the need to decipher the principles governing protein aggregation. Mechanisms of in vivo amyloid formation involve a number of coconspirators and complex interactions with membranes. Nevertheless, understanding the biophysical basis of simpler in vitro amyloid formation is considered important for discovering ligands that preferentially bind regions harboring amyloidogenic tendencies. The determination of the fibril structure of many peptides has set the stage for probing the dynamics of oligomer formation and amyloid growth through computer simulations. Most experimental and simulation studies, however, have been interpreted largely from the perspective of proteins: the role of solvent has been relatively overlooked in oligomer formation and assembly to protofilaments and amyloid fibrils. In this Account, we provide a perspective on how interactions with water affect folding landscapes of amyloid beta (A?) monomers, oligomer formation in the A?16-22 fragment, and protofilament formation in a peptide from yeast prion Sup35. Explicit molecular dynamics simulations illustrate how water controls the self-assembly of higher order structures, providing a structural basis for understanding the kinetics of oligomer and fibril growth. Simulations show that monomers of A? peptides sample a number of compact conformations. The formation of aggregation-prone structures (N*) with a salt bridge, strikingly similar to the structure in the fibril, requires overcoming a high desolvation barrier. In general, sequences for which N* structures are not significantly populated are unlikely to aggregate. Oligomers and fibrils generally form in two steps. First, water is expelled from the region between peptides rich in hydrophobic residues (for example, A?16-22), resulting in disordered oligomers. Then the peptides align along a preferred axis to form ordered structures with anti-parallel ?-strand arrangement. The rate-limiting step in the ordered assembly is the rearrangement of the peptides within a confining volume. The mechanism of protofilament formation in a polar peptide fragment from the yeast prion, in which the two sheets are packed against each other and create a dry interface, illustrates that water dramatically slows self-assembly. As the sheets approach each other, two perfectly ordered one-dimensional water wires form. They are stabilized by hydrogen bonds to the amide groups of the polar side chains, resulting in the formation of long-lived metastable structures. Release of trapped water from the pore creates a helically twisted protofilament with a dry interface. Similarly, the driving force for addition of a solvated monomer to a preformed fibril is water release; the entropy gain and favorable interpeptide hydrogen bond formation compensate for entropy loss in the peptides. We conclude by offering evidence that a two-step model, similar to that postulated for protein crystallization, must also hold for higher order amyloid structure formation starting from N*. Distinct water-laden polymorphic structures result from multiple N* structures. Water plays multifarious roles in all of these protein aggregations. In predominantly hydrophobic sequences, water accelerates fibril formation. In contrast, water-stabilized metastable intermediates dramatically slow fibril growth rates in hydrophilic sequences. PMID:21761818

Thirumalai, D; Reddy, Govardhan; Straub, John E

2012-01-17

41

Recent Images Suggesting Liquid Water on Mars  

NSDL National Science Digital Library

Recently, the press reported that the Mars Orbiter Camera (MOC) had captured compelling images of gullies and slope failures that might be associated with the presence of liquid water on Mars. Now you can see these famous images at Malin Space Science Systems' MOC Website. These sharp, beautiful, color images (.jpeg, .gif) are featured on pages containing descriptions of how such physical features are formed on earth. The images are available in two sizes (small = 360K, large = 690K). Highlights include the "gully landform" compared to channel and apron features on Mount Saint Helens on Earth, a 3-D image (3-D glasses required) of a "weeping" alcove in an impact crater, and clues suggesting that the suspected liquid water on Mars is relatively young.

42

Liquid Hot Water Pretreatment of Cellulosic Biomass  

NASA Astrophysics Data System (ADS)

Lignocellulosic biomass is an abundant and renewable resource for fuel ethanol production. However, the lignocellulose is recalcitrant to enzymatic hydrolysis because of its structural complexity. Controlled-pH liquid hot water (LHW) pretreatment of cellulosic feedstock improves its enzymatic digestibility by removing hemicellulose and making the cellulose more accessible to cellulase enzymes. The removed hemicellulose is solubilized in the liquid phase of the pretreated feedstock as oligosaccharides. Formation of monomeric sugars during the LHW pretreatment is minimal. The LHW pretreatment is carried out by cooking the feedstock in process water at temperatures between 160 and 190C and at a pH of 4-7. No additional chemicals are needed. This chapter presents the detailed procedure of the LHW pretreatment of lignocellulosic biomass.

Kim, Youngmi; Hendrickson, Rick; Mosier, Nathan S.; Ladisch, Michael R.

43

Phase effects for electrons in liquid water and water vapor  

SciTech Connect

The objective of these studies is to compare transport, energy loss, and other phenomena for electrons in water in the liquid and vapor phases. Understanding the differences and similarities is an interesting physics problem in its own right. It is also important for applying the relatively large body of experimental data available for the vapor to the liquid, which is of greater relevance in radiobiology. This paper presents a summary of results from a series of collaborative studies carried out by the authors at Oak Ridge National Laboratory (ORNL) and the Gesellschaft fuer Strahlen- und Umweltforschung (GSF). 14 figs.

Turner, J.E.; Paretzke, H.G.; Wright, H.A.; Hamm, R.N.; Ritchie, R.H.

1988-01-01

44

Thermodynamics of ice nucleation in liquid water.  

PubMed

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

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

2015-01-29

45

Liquid and glass polymorphism in a monatomic system with isotropic, smooth pair interactions.  

PubMed

Systems of particles with interactions given by the Jagla core-softened pair potential are known to exhibit water-like thermodynamic anomalies and a liquid-liquid phase transition. The drawback of the Jagla potential is that it is characterized by discontinuous forces acting between particles and thus is not suitable for standard molecular dynamics (MD) simulations. Here we introduce a smooth version of the Jagla potential based on two Fermi distributions and study the properties of a system of particles interacting via this new "Fermi-Jagla" pair potential by using standard MD simulations. We find that the liquid based on the Fermi-Jagla potential retains most of the properties of the liquid based on the original Jagla potential. Namely, it exhibits the following water-like anomalies: (i) decrease of density, (ii) increase of compressibility, ?(T)(T,P), and (iii) increase of isobaric specific heat, C(P)(T,P), upon isobaric cooling, and (iv) increase of diffusivity upon isothermal compression. The Fermi-Jagla potential also exhibits (i') density minima, (ii') compressibility minima, (iii') isobaric specific heat minima upon isobaric cooling, and (iv') diffusivity minima upon isothermal compression. As in the Jagla model case, we find a liquid-liquid phase transition (LLPT) and a liquid-liquid critical point in the equilibrium liquid. Contrary to the case of the original Jagla model liquid, the LLPT line for the Fermi-Jagla potential has a negative slope in the P-T plane that extends well above the crystallization temperature. This feature makes the Fermi-Jagla potential a better candidate to reproduce the behavior of tetrahedral liquids including water, for which the LLPT line observed in simulations has also negative slope. In the glass state, the Fermi-Jagla pair potential results in reversible polyamorphism between low- and high-density amorphous solids (LDA and HDA, respectively). We also find that HDA results from pressure-induced amorphization of the model's low pressure crystal, as observed in water and other materials. The Fermi-Jagla pair potential, being a smooth function of the interparticle separation, can be easily implemented in standard MD simulation codes. Moreover, since spontaneous crystallization for the Fermi-Jagla potential can be avoided by fast cooling, it can be used to study the phenomenology of glasses. PMID:21992558

Abraham, Joel Y; Buldyrev, Sergey V; Giovambattista, Nicolas

2011-12-01

46

Metastable liquid-liquid transition in a molecular model of water  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

47

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

PubMed

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

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

2014-06-19

48

Liquid Water Removal from a Polymer Electrolyte Fuel Cell  

Microsoft Academic Search

Liquid water transport and removal from the gas diffusion layer GDL and gas channel of a polymer electrolyte fuel cell PEFC are studied experimentally and theoretically. In situ observations of the liquid water distribution on the GDL surface and inside the gas channel were made in an operating transparent PEFC. Liquid droplet formation and emergence from the GDL surface are

F. Y. Zhang; X. G. Yang; C. Y. Wang

2006-01-01

49

Point Mutations in A? Induce Polymorphic Aggregates at Liquid/Solid Interfaces  

PubMed Central

A pathological hallmark of Alzheimers disease (AD), a late onset neurodegenerative disease, is the development of neuritic amyloid plaques, composed predominantly of aggregates of the ?-amyloid (A?) peptide. It has been demonstrated that A? can aggregate into a variety of polymorphic aggregate structures under different chemical environments, and a potentially important environmental factor in dictating aggregate structure is the presence of surfaces. There are also several mutations clustered around the central hydrophobic core of A? (E22G Arctic mutation, E22K Italian mutation, D23N Iowa mutation, and A21G Flemish mutation). These mutations are associated with hereditary diseases ranging from almost pure cerebral amyloid angiopathy (CAA) to typical Alzheimers disease pathology. The goal of this study was to determine how these mutations influence the morphology of A? aggregates under free solution conditions and at an anionic surface/liquid interface. While the rate of formation of specific aggregates was altered by mutations in A? under free solution conditions, the respective aggregate morphologies were similar. However, aggregation occurring directly on a negatively charged mica surface resulted in distinct aggregate morphologies formed by different mutant forms of A?. These studies provide insight into the potential role anionic surfaces play in dictating the formation of A? polymorphic aggregate structures. PMID:22778873

2011-01-01

50

Triplet correlation functions in liquid water  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

51

Triplet correlation functions in liquid water.  

PubMed

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. PMID:25381528

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

2014-11-01

52

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

E-print Network

systems based on water electrolysis to H2 and O2 is limited by availability of low- cost, earthPhotochemical Water Oxidation by Crystalline Polymorphs of Manganese Oxides: Structural different crystal structures, providing a rigorous test system to explore the significance of atomic

Garfunkel, Eric

53

PERMEABILITY OF SOILS TO FOUR ORGANIC LIQUIDS AND WATER  

EPA Science Inventory

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

54

Liquid water sill emplacement on Europa?  

NASA Astrophysics Data System (ADS)

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 propagation, however, only reaches a width of ~ 100s meters, whereas a sill of ~ 4 km width is necessary for formation of the flanking fractures at their observed locations on the ridges. Future work will explore the effect of crack spacing on fracture propagation and will study mechanical layering and lateral stress gradients in greater detail in an effort to enable wider sill emplacement. Assessment of the sill lifetime finds that a 10 - 100 m thick sill will convect and transfer its heat away over ~ hours to a few days, respectively. According to recent work, a liquid sill would need to exist for 1000s of years to enable the lithosphere flexure. One possible mechanism to extend the sill lifetime could involve liquid water replenishment from the ocean driven by brine migration, although the lifetime may still prove challenging to achieve. Overall, our analyses suggest sill emplacement may be possible by liquid ocean water flow up an open vertical fracture to the subsurface and fracture propagation turned horizontal by stress field change factors such as shallow and deep cracks. However, sill width and lifetime must both be extended to enable flexure and flanking fracture formation.

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

2013-12-01

55

Liquid-liquid transition in ST2 water  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

56

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

ERIC Educational Resources Information Center

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

Kesselheim, Alan S.; And Others

57

DERIVING PROGNOSTIC EQUATIONS FOR CLOUD FRACTION AND LIQUID WATER CONTENT  

E-print Network

DERIVING PROGNOSTIC EQUATIONS FOR CLOUD FRACTION AND LIQUID WATER CONTENT Vincent E. Larson1 1-negative everywhere and is normalized. Gregory et al. (2002), Wilson and Gregory (2003), and Bushell et al. (2003 that accounts for how liquid water varies with both total water content and temperature. The variable s has

58

Liquid-liquid and liquid-solid equilibria of systems containing water and selected chlorophenols  

SciTech Connect

Chlorinated phenols are present in effluents of oil refinery, coal mining, plastic, leather, paint, and pharmaceutical industrial plants. The solubilities of phenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol in water were determined in the temperature range between 270 K and 423 K. Dynamic thermal analysis and a visual static method were used to establish the phase diagrams. Results obtained over a wide temperature and concentration range were used to model the liquid-liquid coexistence curve of the systems studied.

Jaoui, M.; Luszczyk, M.; Rogalski, M.

1999-12-01

59

Evidence for Recent Liquid Water on Mars  

NASA Technical Reports Server (NTRS)

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

2000-01-01

60

Reply to "Comment on `Spontaneous liquid-liquid phase separation of water' "  

NASA Astrophysics Data System (ADS)

Two different scenarios have been proposed on the phase separation occurring in the deeply supercooled liquid water. We discuss what we can derive from our simulation results for the two scenarios and propose a way for future investigation. We also demonstrate that the phase separation in the supercooled liquid water looks like the separation of liquid water and vapor just below the conventional critical point.

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2015-01-01

61

Reply to "Comment on 'Spontaneous liquid-liquid phase separation of water'?".  

PubMed

Two different scenarios have been proposed on the phase separation occurring in the deeply supercooled liquid water. We discuss what we can derive from our simulation results for the two scenarios and propose a way for future investigation. We also demonstrate that the phase separation in the supercooled liquid water looks like the separation of liquid water and vapor just below the conventional critical point. PMID:25679745

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2015-01-01

62

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

PubMed

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 in pure water. PMID:22426459

Murata, Ken-ichiro; Tanaka, Hajime

2012-05-01

63

Photoelectron angular distributions from liquid water: effects of electron scattering.  

PubMed

Photoelectron angular distributions (PADs) from the liquid-water surface and from bulk liquid water are reported for water oxygen-1s ionization. Although less so than for the gas phase, the measured PADs from the liquid are remarkably anisotropic, even at electron kinetic energies lower than 100eV, when elastic scattering cross sections for the outgoing electrons with other water molecules are large. The PADs reveal that theoretical estimates of the inelastic mean free path are likely too long at low kinetic energies, and hence the electron probing depth in water, near threshold ionization, appears to be considerably smaller than so far assumed. PMID:24206487

Thrmer, Stephan; Seidel, Robert; Faubel, Manfred; Eberhardt, Wolfgang; Hemminger, John C; Bradforth, Stephen E; Winter, Bernd

2013-10-25

64

Routine Use of PCR-Restriction Fragment Length Polymorphism Analysis for Identification of Mycobacteria Growing in Liquid Media  

Microsoft Academic Search

A PCR-restriction fragment length polymorphism (PCR-RFLP) procedure capable of rapidly identifying 28 species of clinically encountered mycobacteria was evaluated for use in the routine identification of acid-fast isolates growing in BACTEC 12B and 13A liquid media. PCR-RFLP identified 100 of 103 acid-fast isolates recovered from 610 patient specimens submitted for culture during the study. The three isolates unidentifiable by PCR-RFLP

THERESA B. TAYLOR; CANDY PATTERSON; YVONNE HALE; ANDWILLIAM W. SAFRANEK

1997-01-01

65

The puzzling unsolved mysteries of liquid water: Some recent progress  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

66

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

NASA Astrophysics Data System (ADS)

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.

Liu, Yaodong; Wu, Guozhong; Qi, Mingying

2005-08-01

67

SIMPLIFIED LIQUID-LIQUID EXTRACTION METHOD ANALYSIS OF TRIHALOMETHANES IN DRINKING WATER  

EPA Science Inventory

A rapid, simple method for determination of trihalomethanes in water is described. The procedure involves liquid-liquid extraction by vigorous agitation of a pentane:water mixture, followed by gas chromatographic analysis of the pentane extract. Other solvents were also examined ...

68

OPTIMIZATION OF LIQUID-LIQUID EXTRACTION METHODS FOR ANALYSIS OF ORGANICS IN WATER  

EPA Science Inventory

This report describes a laboratory study of liquid-liquid extraction (LLE) method for the analysis of volatile organic compounds in water. The objectives of the study were to examine various method variables, including choice of solvent; solvent to water ratio; matrix pH and ioni...

69

The puzzling unsolved mysteries of liquid water: Some recent progress  

Microsoft Academic Search

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

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

2007-01-01

70

On the polymorphism of a sapogenin monohydrate induced by different rotations of water molecules.  

PubMed

The structure of 1beta,3beta,11alpha-trihydroxyspirosta-5,25(27)-diene (C(27)H(40)O(5); a steroidal sapogenin) isolated from Helleborus serbicus Adam 1906 (Ranunculaceae) and crystallized from absolute ethanol as a monohydrate (melting point 519-522 K) had been characterized by two symmetry-independent binary (steroid-water) layers, cross-linked by hydrogen bonds [Klmn et al. (1985). Acta Cryst. C41, 1645-1647]. Recently, a novel monohydrate was crystallized again from absolute ethanol (source: Helleborus multifidus subspecies serbicus) with a somewhat higher melting point of 525-526 K. X-ray analysis of these crystals [Argay et al. (1998). Acta Chim. Hung. 135, 449-456] revealed a novel polymorph (hereinafter denoted polymorph B), which is also built up by two binary layers of C(27)H(40)O(5) and H(2)O, but in which the relative position of these layers differs from that found in the first modification (polymorph A). Comparing the two polymorphs, layers of one type are found to be similar, displaying identical hydrogen bonding, whereas layers of the second type differ with respect to the orientations adopted by the water molecules; these orientations also differ from those in the layers of the first type. Consequently, by these water rotations, hydrogen bonds, at least partly, are reversed. This leads to two different close packings: in form A four consecutive layers are cross-linked by two homomolecular (hydroxyl.hydroxyl and water.water) hydrogen-bond pairs, while in B there are only heteromolecular hydroxyl.water bonds. These hydrogen-bond dissimilarities together with the differences in the weak CH.X etc. interactions explain the greater stability of the higher melting-point form B. PMID:10927418

Fbin; Argay; Klmn

1999-10-01

71

Polymorphism and morphology of calcium carbonate precipitated in mixed solvents of ethylene glycol and water  

NASA Astrophysics Data System (ADS)

The influence of (mono) ethylene glycol (MEG) on polymorphism and the resulting morphology of calcium carbonate have been studied for activity-based supersaturation ratios in the range of 3-10 and temperatures from 25-80 C in mixed solvents of ethylene glycol and water at ratios of 0-90 wt%. The presence of a co-solvent in the solution affects the supersaturation, because of changes in the activity coefficients and the solubility of the salt, a fact that is usually not accounted for in similar studies in the literature. In the present study, the effect of the solvent was isolated from the accompanying change in the supersaturation. MEG was found to affect both the polymorphic abundance in the precipitates, the morphology of the particles and the transformation rates. High concentrations of MEG favoured the precipitation of vaterite and higher temperatures promoted the formation of aragonite. The particle size was reduced in experiments with high MEG concentrations at supersaturations ratios comparable to water solutions, illustrating that the nucleation rate is affected by the co-solvent. The morphology of the calcium carbonate particles was changed at various conditions of MEG concentrations and temperatures from cubes of calcite to spherical, flower-like and dumbbell particles of vaterite and aragonite needles. MEG prolongs the transformation time of metastable polymorphs and the effect was shown to be caused by the solvent itself, probably as a result of kinetic stabilization by delaying the growth rate of the more stable polymorphs.

Flaten, Ellen Marie; Seiersten, Marion; Andreassen, Jens-Petter

2009-06-01

72

Searching for springtime zonal liquid interfacial water on Mars  

NASA Astrophysics Data System (ADS)

We analyzed the spatial and temporal characteristics of the surface temperature at the northern water ice annulus on Mars that is left behind the receding seasonal carbon dioxide cap in springtime. Using OMEGA hyperspectral images we show that water ice without carbon dioxide ice coverage lasts for 10-30 days between 55 and 70N. The longest water ice coverage without CO2 ice is observed between 40-55N and 300-330E and lasts 80-110 days in ideal case. Using TES temperature data, we show that thin interfacial liquid water may be present at the water ice annulus. Higher spatial resolution THEMIS temperature data shows that the above mentioned finding is relevant to a spatial scale of 100 m. Although the exact near surface water vapor concentration is not known, beside the average 10 pr-?m we used two elevated values and corresponding threshold temperatures for interfacial liquid water formation: 190 and 199 K beside the average 180 K. While the area of interfacial liquid water is substantially smaller in the case of higher threshold temperature values, even for 199 K terrains exist at THEMIS and OMEGA scale of resolution where such thin interfacial liquid water could be present on the surface. Summarizing: good chance exists for the presence of liquid interfacial water in the warmest part of the day on at the northern hemisphere of Mars at extended areas - although firm evidence requires better targeted future observations.

Kereszturi, Akos; Appr, Thomas

2014-08-01

73

Glassliquid transition of water at high pressure  

PubMed Central

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 1GPa and temperatures below approximately 140K, 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 1GPa and 140K. On heating of HDA, the Cp increases abruptly by (3.40.2)Jmol-1K-1 before crystallization starts at (1531)K. This is larger than the Cp rise at the glass to liquid transition of annealed ASW at 1atm, which suggests the existence of liquid water under these extreme conditions. PMID:21690361

Andersson, Ove

2011-01-01

74

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

E-print Network

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

75

Space Station Water Processor Mostly Liquid Separator (MLS)  

NASA Technical Reports Server (NTRS)

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.

Lanzarone, Anthony

1995-01-01

76

Liquid water in the domain of cubic crystalline ice Ic  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

77

Experimentally proven liquid-liquid critical point of dilute glycerol-water solution at 150 K  

NASA Astrophysics Data System (ADS)

The experimental and theoretical studies of supercooled liquid water strongly suggest that the two liquid waters and their liquid-liquid critical point (LLCP) exist at low temperature. However, the decisive experimental evidence of the LLCP has not been obtained because of the rapid crystallization of liquid water in the "no-man's land." Here, we observed experimentally the pressure-induced polyamorphic transition in the dilute glycerol-water solution which relates to the water polyamorphism. We examined the effect of the glycerol concentration on the liquid-liquid transition, and found its LLCP around 0.12-0.15 mole fraction, 0.03-0.05 GPa, and 150 K. A 150 K was above, or around, the recently recognized glass transition temperatures of amorphous ices, and the crystallization did not occur, indicating that the direct observation of LLCP is feasible. The low-temperature LLCP has implication to the argument of the relation between the interaction potential of water molecule and the polyamorphic phase diagram.

Suzuki, Yoshiharu; Mishima, Osamu

2014-09-01

78

Spectroscopic investigations of hydrogen bond dynamics in liquid water  

E-print Network

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

Fecko, Christopher J., 1975-

2004-01-01

79

Partial molar volume of water in phonolitic glasses and liquids  

Microsoft Academic Search

The volumes and expansivities of four hydrous phonolite glasses and liquids have been measured by dilatometry from 300 K up to the glass transition and over a 50 K interval just above the glass transition. The partial molar volume of water is independent of the water content for the glass and liquid phases, with values of about 11.0ǂ.5 and 17.1ǂ.9

Ali M. Bouhifd; Alan Whittington; Pascal Richet

2001-01-01

80

Waterhelium condensate (watergel) in liquid helium  

Microsoft Academic Search

The waterhelium condensate (watergel) is formed in He-II cooled below 1.5K as a result of condensation of the gas flow of 4He with the water impurity at the surface of superfluid liquid. The experimental results indicate that the shape of the gel samples formed below the liquid surface depends strongly on geometry of experimental cell: from an oval iceberg in

Leonid P. Mezhov-Deglin; Andrey M. Kokotin

2003-01-01

81

Room Temperature Ionic Liquids for Separating Organics from Produced Water  

Microsoft Academic Search

The distribution of polar organic compounds typical of water contaminants (organic acids, alcohols, and aromatic compounds) associated with oil and gas production was measured between water and nine hydrophobic, room?temperature ionic liquids. The ionic liquids used in this study were 1?butyl?3?methylimidazolium bistrifluoromethanesulfonylimide, 1?hexyl?3?methylimidazolium bistrifluoromethanesulfonylimide, 1?octyl?3?methylimidazolium bistrifluoromethanesulfonylimide, 1?butyl?3?methylimidazolium hexafluorophosphate, trihexyltetradecylphosphonium bistrifluoromethanesulfonylimide, 1?butyl?1?methyl?pyrrolidinium bistrifluoromethanesulfonylimide, trihexyltetradecylphosphonium dodecylbenzenesulfonate, tributyltetradecylphosphonium dodecylbenzenesulfonate, and trihexyltetradecylphosphonium methanesulfonate. Sensitivity

J. McFarlane; W. B. Ridenour; H. Luo; R. D. Hunt; D. W. DePaoli; R. X. Ren

2005-01-01

82

Interfacial Depth Profiling of the Orientation and Bonding of Water Molecules across Liquid-Liquid Interfaces  

E-print Network

-Liquid Interfaces Dave S. Walker and Geraldine L. Richmond* Department of Chemistry and Materials Science Institute Molecular interactions that create the interfacial properties present at a junction between water and several hydrophobic liquids are the focus of this paper. This study employs molecular dynamics simulations

Richmond, Geraldine L.

83

Ice-Crystal Fallstreaks from Supercooled Liquid Water Parent Clouds  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

84

Process for blending coal with water immiscible liquid  

DOEpatents

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.

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

1982-10-26

85

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

E-print Network

By the 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 allows us to study the water thermodynamic behavior 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.

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

2009-01-20

86

Liquid Water in the Extremely Shallow Martian Subsurface  

NASA Technical Reports Server (NTRS)

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.

Pavlov, A.; Shivak, J. N.

2012-01-01

87

New Isotopic Water Analyzer for Hydrological Measurements of Both Liquid Water and Water Vapor  

NASA Astrophysics Data System (ADS)

Measurements of the stable isotope ratios of liquid water allow determination of water flowpaths, residence times in catchments, and groundwater migration. Previously, discrete water samples have been collected and transported to an IRMS lab for isotope characterization. Due to the expense and labor associated with such sampling, isotope studies have thus been generally limited in scope and in temporal resolution. We report on the recent development of the first Isotopic Water Analyzer that simultaneously quantifies ?2H, ?17O and ?18O in liquid water or in water vapor from different natural water sources (e.g., rain, snow, streams and groundwater). In High-Throughput mode, the IWA can report measurements at the unprecedented rate of over 800 injections per day, which yields more than 140 total unknown and reference samples per day (still with 6 injections per measurement). This fast time response provides isotope hydrologists with the capability to study dynamic changes in ? values quickly (minutes) and over long time scales (weeks, months), thus enabling studies of mixing dynamics in snowmelt, canopy throughfall, stream mixing, and allows for individual precipitation events to be independently studied. In addition, the same IWA can also record fast measurements of isotopic water vapor (?2H, ?17O, ?18O) in real time (2 Hz data rate or faster) over a range of mole fractions greater than 60000 ppm H2O in air. Changing between operational modes requires a software command, to enable the user to switch from measuring liquid water to measuring water vapor, or vice versa. The new IWA, which uses LGR's patented Off-axis ICOS technology, incorporates proprietary internal thermal control for stable measurements with essentially zero drift despite changes in ambient temperature (over the entire range from 0-45 degrees C). Measurements from recent field studies using the IWA will be presented.

Owano, T.; Gupta, M.; Berman, E.; Baer, D.

2012-04-01

88

Genomic organization and polymorphisms detected by denaturing high-performance liquid chromatography of porcine SLC11A1 gene.  

PubMed

SLC11A1 (also known as Natural Resistance Associated Macrophage Protein1, NRAMP1) plays a crucial role in resistance of inbred mice to infection with several intracellular pathogens such as Mycobacterium, Leishmania and Salmonella. In this study, PCR amplification and sequencing were performed to obtain the genomic organization and sequence of porcine SLC11A1 gene by comparative genomic analysis. Results showed that porcine SLC11A1 gene consists of 15 exons and 14 introns, which is consistent with that of mice and human. All introns were sequenced and their nucleotide sequences were submitted to GenBank. The exon/intron boundaries were determined by comparing cDNA sequence with amplified genomic DNA sequences. Mutational analysis was performed on exonic and neighboring intronic region by denaturing high-performance liquid chromatography (DHPLC) and sequencing confirmation. Forty polymorphisms were identified; six are located in exons and thirty-four in introns. Two exonic polymorphisms are nonsynonymous changes (D6H and V175I), three are synonymous changes (S23, G33 and I155), and one is in 3' UTR. The availability of the fine genomic organization and identification of the polymorphisms will facilitate the evaluation of porcine SLC11A1 functional role in diseases resistance or susceptibility. PMID:17654007

Wu, Zhen-Fang; Luo, Wen-Hua; Yang, Guan-Fu; Zhang, Xi-Quan

2007-10-01

89

Order parameter defining liquid-liquid transition in water  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

90

Behavior of Supercooled Aqueous Solutions Stemming from Hidden Liquid-Liquid Transition in Water  

E-print Network

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, to be consistent with the presence of the metastable liquid-liquid transition. We suggest an interpretation of the liquid-liquid transition in aqueous solutions of glycerol, recently observed by Murata and Tanaka, elucidating the non-conserved nature of the order parameter, its coupling with density and concentration, and the peculiarity of "spinodal decomposition without phase separation". We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

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

2014-08-21

91

Interaction of C1O radical with liquid water  

SciTech Connect

In the present work, the interaction between ClO radical and liquid water is studied using molecular dynamics simulations. We perform simulations of collisions of a ClO radical with the surface of liquid water to understand the accommodation of ClO by liquid water. Simulations results show that the ClO radical has a higher propensity to be adsorbed on the air-water interface than be dissolved in the bulk. The free energy profile is also calculated and the solvation free energy and Henrys law constant is determined for ClO as, ?Gs, of -2.9 kcal/mol and 5.5 M/atm, respectively. The mechanism of the ClO recombination reaction is also discussed and the results are consistent with laboratory findings.

Du, Shiyu; Francisco, Joseph S.; Schenter, Gregory K.; Garrett, Bruce C.

2009-10-21

92

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

NASA Astrophysics Data System (ADS)

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), 10.1063/1.3643333 and preprint 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.

Limmer, David T.; Chandler, David

2013-06-01

93

Quantum effects in liquid water and ice: model dependence.  

PubMed

This paper explores the influence of choice of potential model on the quantum effects observed in liquid water and ice. This study utilizes standard rigid models and a more formal context for the rigid-body centroid molecular dynamics methodology used to perform the quantum simulations is provided. Quantum and classical molecular dynamics simulations are carried out for liquid water and ice Ih at 298 and 220 K, respectively, with the simple point charge/extended and TIP4P-Ew water models. The results obtained for equilibrium and dynamical properties are compared with those recently reported on TIP4P [L. Hernandez de la Pena and P. G. Kusalik, J. Chem. Phys. 121, 5992 (2004); L. Hernandez de la Pena et al., J. Chem. Phys 123, 144506 (2005)]. For the liquid, an energy shift of about 8% and an average molecular uncertainty of about 11 degrees were found independently of the water model. The self-diffusion coefficient consistently increases by more than 50% when going from the classical to the quantum system and quantum dynamics are found to reproduce the experimental isotopic shifts with the models examined. The ice results compare remarkably well with those previously reported for the TIP4P water model; they confirm that quantum effects are considerable and that the quantum mechanical uncertainty and the energy shifts due to quantization are smaller in ice than in liquid water. The relevance of these findings in the context of the construction of water models is briefly discussed. PMID:16942231

Hernndez de la Pea, Lisandro; Kusalik, Peter G

2006-08-01

94

A Mechanism for Recent Production of Liquid Water on Mars  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

95

Perspectives on the Interaction of Plasmas With Liquid Water for Water Purification  

Microsoft Academic Search

Plasma production or plasma injection in liquid water affords one the opportunity to nonthermally inject advanced oxidation processes into water for the purpose of purification or chemical processing. Such technology could potentially revolutionize the treatment of drinking water, as well as current methods of chemical processing through the elimination of physical catalysts. Presented here is an overview of current water

John Foster; Bradley S. Sommers; Sarah Nowak Gucker; Isaiah M. Blankson; Grigory Adamovsky

2012-01-01

96

Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water.  

PubMed

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related. PMID:24089711

Schir, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-28

97

Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water  

NASA Astrophysics Data System (ADS)

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related.

Schir, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-01

98

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

99

1Octanol\\/Water Partition Coefficient of Ionic Liquids  

Microsoft Academic Search

Room temperature ionic liquids are nonvolatile, they can only disperse into the aquatic environment. 1-octanol-water partition coefficient is a measure of the bioconcentration tendency of a chemical in a hydrologic cycle. In this work, 1-octanol-water partition coefficient of 1-ethyl-3-methylimidazolium hexafluoro- phosphate ((emim)(PF6)) and 1-butyl-3-methylimidazolium hexafluorophosphate ((bmim)(PF6)) at 303 K were measured using ultraviolet spectrometer and Karl-Fischer analysis. The 1-octanol\\/water partition

Cheng-Huang Choua; Fu-Shan Perng; David Shan; Hill Wong; Wen Cheng Su

100

Water and other tetrahedral liquids: order, anomalies and solvation  

NASA Astrophysics Data System (ADS)

In order to understand the common features of tetrahedral liquids with water-like anomalies, the relationship between local order and anomalies has been studied using molecular dynamics simulations for three categories of such liquids: (a) atomistic rigid-body models for water (TIP4P, TIP4P/2005, mTIP3P, SPC/E), (b) ionic melts, BeF2 (TRIM model) and SiO2 (BKS potential) and (c) Stillinger-Weber liquids parametrized to model water (mW) and silicon. Rigid-body, atomistic models for water and the Stillinger-Weber liquids show a strong correlation between tetrahedral and pair correlation order and the temperature for the onset of the density anomaly is close to the melting temperature. In contrast, the ionic melts show weaker and more variable degrees of correlation between tetrahedral and pair correlation metrics, and the onset temperature for the density anomaly is more than twice the melting temperature. In the case of water, the relationship between water-like anomalies and solvation is studied by examining the hydration of spherical solutes (Na+, Cl-, Ar) in water models with different temperature regimes of anomalies (SPC/E, TIP4P and mTIP3P). For both ionic and nonpolar solutes, the local structure and energy of water molecules is essentially the same as in bulk water beyond the second-neighbour shell. The local order and binding energy of water molecules are not perturbed by the presence of a hydrophobic solute. In the case of ionic solutes, the perturbation is largely localized within the first hydration shell. The binding energies for the ions are strongly dependent on the water models and clearly indicate that the geometry of the partial charge distributions, and the associated multipole moments, play an important role. However the anomalous behaviour of the water network has been found to be unimportant for polar solvation.

Shadrack Jabes, B.; Nayar, Divya; Dhabal, Debdas; Molinero, Valeria; Chakravarty, Charusita

2012-07-01

101

Water and other tetrahedral liquids: order, anomalies and solvation.  

PubMed

In order to understand the common features of tetrahedral liquids with water-like anomalies, the relationship between local order and anomalies has been studied using molecular dynamics simulations for three categories of such liquids: (a)atomistic rigid-body models for water (TIP4P, TIP4P/2005, mTIP3P, SPC/E), (b)ionic melts, BeF(2) (TRIM model) and SiO(2) (BKS potential) and (c)Stillinger-Weber liquids parametrized to model water (mW) and silicon. Rigid-body, atomistic models for water and the Stillinger-Weber liquids show a strong correlation between tetrahedral and pair correlation order and the temperature for the onset of the density anomaly is close to the melting temperature. In contrast, the ionic melts show weaker and more variable degrees of correlation between tetrahedral and pair correlation metrics, and the onset temperature for the density anomaly is more than twice the melting temperature. In the case of water, the relationship between water-like anomalies and solvation is studied by examining the hydration of spherical solutes (Na(+), Cl(-), Ar) in water models with different temperature regimes of anomalies (SPC/E, TIP4P and mTIP3P). For both ionic and nonpolar solutes, the local structure and energy of water molecules is essentially the same as in bulk water beyond the second-neighbour shell. The local order and binding energy of water molecules are not perturbed by the presence of a hydrophobic solute. In the case of ionic solutes, the perturbation is largely localized within the first hydration shell. The binding energies for the ions are strongly dependent on the water models and clearly indicate that the geometry of the partial charge distributions, and the associated multipole moments, play an important role. However the anomalous behaviour of the water network has been found to be unimportant for polar solvation. PMID:22739063

Jabes, B Shadrack; Nayar, Divya; Dhabal, Debdas; Molinero, Valeria; Chakravarty, Charusita

2012-07-18

102

Experimental evidence for a liquid-liquid crossover in deeply cooled confined water.  

PubMed

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. PMID:25479506

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

2014-11-21

103

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

104

Metastable statics and dynamics of liquid water  

Microsoft Academic Search

Water is perhaps the most ubiquitous, and the most essential, of any molecule on earth. Indeed, H2O challenges the imagination of even the most creative science fiction writers (such as K. Vonnegut) to picture what life would be like without water, and one often hears the adage \\

H. Eugene Stanley

105

Surface potential of the water liquid-vapor interface  

NASA Technical Reports Server (NTRS)

An analysis of an extended molecular dynamics calculation of the surface potential (SP) of the water liquid-vapor interface is presented. The SP predicted by the TIP4P model is -(130 + or - 50) mV. This value is of reasonable magnitude but of opposite sign to the expectations based on laboratory experiments. The electrostatic potential shows a nonmonotonic variation with depth into the liquid.

Wilson, Michael A.; Pohorille, Andrew; Pratt, Lawrence R.

1988-01-01

106

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

E-print Network

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

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

2015-02-27

107

Observed cloud reflectivities and liquid water paths: An update  

NASA Technical Reports Server (NTRS)

The FIRE microwave radiometer observations of liquid water path from San Nicolas Island and simultaneous NOAA AVHRR observations of cloud reflectivity were used to test a relationship between cloud liquid water path and cloud reflectivity that is often used in general circulation climate models (Stephens, 1978). The results of attempts to improve the data analysis which was described at the previous FIRE Science Team Workshop and elsewhere (Coakley and Snider, 1989) are reported. The improvements included the analysis of additional satellite passes over San Nicolas and sensitivity studies to estimate the effects on the observed reflectivities due to: (1) nonzero surface reflectivities beneath the clouds; (2) the anisotropy of the reflected radiances observed by the AVHRR; (3) small scale spatial structure in the liquid water path; and (4) adjustments to the calibration of AVHRR.

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

1990-01-01

108

Evaluation of ground-based remotely sensed liquid water cloud properties using shortwave radiation measurements  

E-print Network

Evaluation of ground-based remotely sensed liquid water cloud properties using shortwave radiation 2009 Accepted 31 January 2010 Water cloud optical and microphysical properties are required 1. Introduction The microphysical and optical properties of liquid water clouds are important

Haak, Hein

109

A high pressure calorimetric experiment to validate the liquid-liquid critical point hypothesis in water  

E-print Network

An experimental proposal to test the existence of a liquid-liquid critical point in water, based on high pressure calorimetric measurements, is presented on this paper. Considering the existence of an intramolecular correlation in the water molecule we show how the response of the specific heat at high pressure is different depending on the existence, or not, of the second critical point. If the liquid-liquid critical point hypothesis is true there must be a maximum in the specific heat at some temperature $T>T_{H}$ for any pressure $P>P_{c}$ (being $T_{H}$ the homogeneous nucleation temperature and $P_{c}$ the pressure of the second critical point). This maximum does not appear for the singularity free scenario.

Manuel I. Marques

2007-01-23

110

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

PubMed

There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed. PMID:23104614

Tanaka, Hajime

2012-10-01

111

Solid-liquid phase diagrams for the determination of the solid state nature of both polymorphs of (RS)-2-(2-oxo-pyrrolidin-1-yl)-butyramide.  

PubMed

This work focuses on the determination of the solid state nature of (RS)-2-(2-oxo-pyrrolidin-1-yl)-butyramide (Etiracetam), the racemic intermediate of (S)-2-(2-oxo-pyrrolidin-1-yl)-butyramide, an Active Pharmaceutical Ingredient, marketed under the name Levetiracetam(). It is show how this information can easily be extracted from solid-liquid phase diagrams of the racemic system. As two polymorphs of Etiracetam are known (Forms I and II), the analyses have been performed considering both polymorphs. The solid-liquid phase diagrams are determined experimentally, using Differential Scanning Calorimetry, and theoretically, using the Prigogine-Defay and Schroeder-Van Laar equations. Only the phase diagram involving the polymorph stable at higher temperatures (Form II) can be constructed experimentally. The theoretical phase diagram involving this polymorph compares well with the experimental one, thus allowing the use of theoretical equations for the prediction of the solid-liquid phase diagram involving Form I, which is meta-stable above 30.5 C. Our findings confirm that both polymorphs are racemic compounds, which is also confirmed by XRPD analysis. PMID:22846407

Herman, Christelle; Haut, Benot; Aerts, Luc; Leyssens, Tom

2012-11-01

112

The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in Atomistic Models of Water  

NASA Astrophysics Data System (ADS)

Our detailed and controlled studies of free energy surfaces for models of water find no evidence for reversible polyamorphism, and a general theoretical analysis of the phase behavior of cold water in nano pores shows that measured behaviors of these systems reflect surface modulation and dynamics of ice, not a liquid-liquid critical point. A few workers reach different conclusions, reporting evidence of a liquid-liquid critical point in computer simulations of supercooled water. In some cases, it appears that these contrary results are based upon simulation algorithms that are inconsistent with principles of statistical mechanics, such as using barostats that do not reproduce the correct distribution of volume fluctuations. In other cases, the results appear to be associated with difficulty equilibrating the supercooled material and mistaking metastability for coarsening of the ordered ice phase. In this case, sufficient information is available for us to reproduce the contrary results and to establish that they are artifacts of finite time sampling. This finding leads us to the conclusion that two distinct, reversible liquid phases do not exist in models of supercooled water.

Chandler, David; Limmer, David

2013-03-01

113

How much liquid water was there on Martian dunes?  

NASA Astrophysics Data System (ADS)

Presently, liquid water unlikely to be found on the surface of Mars because of atmospheric pressure/temperature conditions below water's triple-point. However, gullies discovered by Malin and Edgett (2000) suggest that significant amounts of liquid water has flowed on Mars in the recent past. These gullies are among the youngest features on Mars based on the scarcity of cratered gullies (Heldmann et al., 2007) and their superposition on relatively young formations such as dunes. Several hypotheses have been suggested for the formation of gullies: (i) runoff and debris flows with liquid water from groundwater aquifers (Heldmann and Mellon, 2004; Malin et al., 2000), (ii) snow-melt (Christensen, 2003; Dickson et al, 2007), (iii) liquid CO2 breakout (Musselwhite et al., 2001), (iv) melting of near-surface ground ice (< 1 m meter) at high obliquity (Costard et al., 2002), (v) geothermal-heated aquifers (Gaidos, 2001; Hartmann, 2001), (vi) the presence of brines (Knauth et al., 2000; Knauth and Burt, 2003). This study focuses on gully morphologies on the Russell megadune (54.5S; 12.7E) and in Kaiser crater (46.2S; 19.1E) using High Resolution Imaging Science Experiment (HiRISE) images and Digital Terrain Models (DTM). Gullies on terrestrial sand dunes are rare, and their presence on Mars, as well as their mechanical properties, and the quantity of fluid required for their formation currently remain misunderstood. Based on the scenario of ground ice melting in a periglacial environment, we propose to test the hypothesis that Martian gullies on dunes were triggered by the presence of liquid water. The calculated results for Martian gullies are consistent with terrestrial studies on debris flows. Based on a morphological description and on the estimated physical parameters, we propose a model for gully formation on Martian dunes. The melt water from near-surface ground ice is incorporated in the debris flow and water concentration increases during its propagation. The increase of water concentration in the debris flow can be explained by a progressive increase of water/ice content in the permafrost downslope. Consequently, the lack of a final deposit at the front of some gullies tends to demonstrate that the flow became relatively highly concentrated in liquid downstream and all the water could have been lost in the final stage of the flow. Here we quantify the quantity of liquid necessary to form such a morphology.

Gargani, J.; Jouannic, G.; Costard, F.; Ori, G. G.; Marmo, C.; Schmidt, F.; Lucas, A.; Busson, J.

2012-04-01

114

[Polymorphism of the fur pigmentation genes and the hormonal adaptation system in the water vole (Arvicola terrestris)].  

PubMed

Postnatal ontogenesis of hormonal system of hypophysis - adrenal glands and hormonal reaction under stress conditions were examined in adult water mouse, which had polymorphic fur color genes. Black females (genotype aa), opposite to brown ones, (genotype AA, Aa) had changed postnatal ontogenesis of adrenal glands function and they had not hormonal reaction to the two days water deprivation. PMID:1955614

Bazhan, N M

1991-01-01

115

Resurfacing of Ganymede by Liquid-Water Volcanism  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

116

Solute effects on the thermodynamic and kinetic behavior of water and liquid-liquid transition  

NASA Astrophysics Data System (ADS)

Water is known to be an exceptionally poor glass former, which is one of the characteristic features of water, but its link to the thermodynamic and kinetic anomalies of water remains elusive. Recently we showed that the glass-forming ability and the fragility of a water/salt mixture are closely related to its equilibrium phase diagram.footnotetextM. Kobayashi and H. Tanaka, Phys. Rev. Lett. 106, 125703 (2011);J. Phys. Chem. B 115, 14077 (2011) We proposed that frustration between local and global orderings controls both the glass-forming ability and fragility on the basis of experimental evidence. Relying on the same role of salt and pressure, which commonly breaks tetrahedral order, we apply this idea to pure water under pressure. This scenario not only explains unusual behavior of water-type liquids such as water, Si and Ge, but also provides a general explanation on the link between the equilibrium phase diagram, the glass-forming ability, and the fragility of various materials including oxides, chalcogenides, and metallic glasses.footnotetextH. Tanaka, Eur. Phys. J. E 35, 113 (2012) We also discuss liquid-liquid transition found in mixtures of water with glycerolfootnotetextK. Murata and H. Tanaka, Nature Mater. 11, 436 (2012) and other molecules and its implications.

Tanaka, Hajime

2013-03-01

117

Remote sensing of atmospheric water vapor and liquid water with the Nimbus 5 microwave spectrometer  

NASA Technical Reports Server (NTRS)

The Nimbus 5 satellite is provided with a passive microwave spectrometer (NEMS) incorporating channels at 22.235 and 31.4 GHz to measure atmospheric water vapor and liquid water over ocean. The discussion covers principles of atmospheric water determination, accuracy of measurements, observations of specific storms and fronts, and observations of water vapor and liquid water on a global scale. The NEMS experiment has demonstrated the ability of a two-channel microwave spectrometer to determine integrated abundances of water vapor and liquid water with estimated rms accuracies of 0.2 and 0.01 g per sq cm, respectively. The data can be used to plot global maps or accumulate global statistics.

Staelin, D. H.; Kunzi, K. F.; Pettyjohn, R. L.; Poon, R. K. L.; Wilcox, R. W.; Waters, J. W.

1976-01-01

118

New Isotopic Water Analyzer for Hydrological Measurements of both Liquid Water and Water Vapor  

NASA Astrophysics Data System (ADS)

Measurements of the stable isotope ratios of liquid water (?2H and ?18O) allow determination of water flowpaths, residence times in catchments, and groundwater migration. In the past, discrete water samples have been collected and transported to an IRMS lab for isotope characterization. Due to the expense and labor associated with such sampling, isotope studies have thus been generally limited in scope and in temporal resolution. We report on the recent development of a new field-portable Isotopic Water Analyzer (IWA-35EP) that accurately quantifies ?2H and ?18O of different natural water sources (e.g., rain, snow, streams and groundwater) at the unprecedented rate of 1080 injections per day, which yields 180 total unknown and reference samples per day (150 unknown samples per day), or 1 measurement of an unknown sample in less than 10 minutes (with 6 injections per measurement). This fast time response provides isotope hydrologists with the capability to study dynamic changes in ? values quickly (minutes) and over long time scales (weeks, months), thus enabling studies of mixing dynamics in snowmelt, canopy throughfall, stream mixing, and allows for individual precipitation events to be independently studied. In addition, the same IWA can also record fast measurements of isotopic water vapor (?18O and ?2H) in real time (2 Hz data rate or faster) over a range of mole fractions greater than 60000 ppm H2O in air. Changing between operational modes requires a software command, to enable the user to switch from measuring liquid water to measuring water vapor, or vice versa. The new IWA, which uses LGR's patented Off-axis ICOS technology, incorporates proprietary internal thermal control for stable measurements with essentially zero drift. Measurements from recent field studies using the IWA will be presented.

Owano, T. G.; Gupta, M.; Dong, F.; Baer, D. S.

2011-12-01

119

Satellite Remote Sensing of the Liquid Water Sensitivity in Water Clouds  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

120

Diffusion-controlled and ``diffusionless'' crystal growth near the glass transition temperature: Relation between liquid dynamics and growth kinetics of seven ROY polymorphs  

NASA Astrophysics Data System (ADS)

The liquid dynamics of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, named ROY for its red, orange, and yellow crystal polymorphs, was characterized by dielectric spectroscopy and differential scanning calorimetry. Four of these polymorphs show fast "diffusionless" crystal growth at low temperatures while three others do not. ROY was found to be a typical fragile organic liquid. Its ? relaxation process has time-temperature superposition symmetry across the viscous range (??=100 s-100 ns) with the width of the relaxation peak characterized by a constant ?KWW of 0.73. No secondary relaxation peak was observed, even with glasses made by fast quenching. For the polymorphs not showing fast crystal growth in the glassy state, the growth rate has a power-law relation with ??, u ???-?, where ? ?0.7. For the polymorphs showing fast crystal growth in the glassy state, the growth is so fast near and below the glass transition temperature Tg that thousands of molecular layers can be added to the crystalline phase during one structural relaxation time of the liquid. In the glassy state, this mode of growth slows slightly over time. This slowdown is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the glass vapor pressure, or the rate of structural relaxation. This study demonstrates that from the same liquid or glass, the growth of some polymorphs is accurately described as being limited by the rate of structural relaxation or bulk diffusion, whereas the growth of other polymorphs is too fast to be under such control.

Sun, Ye; Xi, Hanmi; Ediger, M. D.; Richert, Ranko; Yu, Lian

2009-08-01

121

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

SciTech Connect

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.

Yu, Tang-Qing, E-mail: tangqing.yu@nyu.edu; Vanden-Eijnden, Eric, E-mail: eve2@cims.nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Chen, Pei-Yang; Chen, Ming [Department of Chemistry, New York University, New York, New York 10003 (United States); Samanta, Amit [Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA and Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Tuckerman, Mark, E-mail: mark.tuckerman@nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Department of Chemistry, New York University, New York, New York 10003 (United States); NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062 (China)

2014-06-07

122

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

123

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

E-print Network

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

Santra, Biswajit; Martelli, Fausto; Car, Roberto

2015-01-01

124

DIURNAL VARIATION IN WATER VAPOR AND LIQUID WATER PROFILES FROM A NEW MICROWAVE RADIOMETER PROFILER  

E-print Network

only twice a day (00 and 12 UTC). A new microwave radiometer profiler (MWRP) has been developed5.5 DIURNAL VARIATION IN WATER VAPOR AND LIQUID WATER PROFILES FROM A NEW MICROWAVE RADIOMETER water up to 10 km are retrieved from the MWRP radiance data in about 10-min temporal resolu- tion

Wang, Junhong

125

Polymorphic behavior of some fully hydrogenated oils and their mixtures with liquid oil  

Microsoft Academic Search

Fully hydrogenated soybean oil, beef fat, rapeseed oil, a rapeseed, palm and soybean oil blend, cottonseed oil and palm oil\\u000a were characterized by fatty acid composition, glyceride carbon number and partial glyceride content, as well as melting and\\u000a crystallization properties. The latter were established by differential scanning calorimetry. Polymorphic behavior was analyzed\\u000a by X-ray diffraction of the products in the

L. deMan; J. M. deMan; B. Blackman

1989-01-01

126

A quantitative account of quantum effects in liquid water  

Microsoft Academic Search

We report converged quantum statistical mechanical simulations of liquid water with the Thole-type Model (version 2.1), Flexible, polarizable (TTM2.1-F) interaction potential for water. Simulations of total length of 600 ps with a 0.05 fs time step for a periodic unit cell of 256 molecules with up to 32 replicas per atom suggest that the quantum effects contribute 1.01+\\/-0.02 kcal\\/mol to

Georgios S. Fanourgakis; Gregory K. Schenter; Sotiris S. Xantheas

2006-01-01

127

A quantitative account of quantum effects in liquid water  

Microsoft Academic Search

We report converged quantum statistical mechanical simulations of liquid water with the Thole-type Model (version 2.1), Flexible, polarizable (TTM2.1-F) interaction potential for water. Simulations of total length of 600 ps with a 0.05 fs time step for a periodic unit cell of 256 molecules with up to 32 replicas per atom suggest that the quantum effects contribute 1.010.02 kcal?mol to

G. S. Fanourgakis; G. K. Schenter; S. S. Xantheas

2006-01-01

128

Molecular dynamics of the water liquid-vapor interface  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

129

Economics of liquid hydrogen from water electrolysis  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

130

Liquid state theories for the structure of water  

Microsoft Academic Search

Liquid state theories are investigated for the local structure of the simple point charge (SPC) and a modified SPC (MSPC) model of water. The latter model includes a van der Waals repulsion between the oxygen (O) and hydrogen (H) atoms, which is necessary for the implementation of some integral equation theories. Two integral equation theories, the reference interaction site model

Govardhan Reddy; C. P. Lawrence; J. L. Skinner; Arun Yethiraj

2003-01-01

131

Water immiscible ionic liquids as solvents for whole cell biocatalysis  

Microsoft Academic Search

Whole cell biocatalysis can effectively be used for the production of enantiomerically pure compounds, but efficiency is often low. Toxicity and poor solubility of substrates and products are the main obstacles. In this study, water immiscible ionic liquids are shown to have no damaging effects on the cell membranes of Escherichia coli and Saccharomyces cerevisiae. Thus, they can be used

Holger Pfruender; Ross Jones; Dirk Weuster-Botz

2006-01-01

132

Updated model for dielectric response function of liquid water  

PubMed Central

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

Dingfelder, Michael

2013-01-01

133

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

SciTech Connect

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.

Perahia, Dvora, Dr. (Clemson University, Clemson, SC); Pierce, Flint (Clemson University, Clemson, SC); Tsige, Mesfin (Southern Illinois University, Carbondale, IL); Grest, Gary Stephen, Dr.

2008-08-01

134

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

E-print Network

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

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

2006-08-28

135

The effect of traces of hexyloxyethoxyethanol on the 2-butoxyethanol + water liquid-liquid coexistence curve  

NASA Astrophysics Data System (ADS)

A cloudy region found in the liquid system 2-butoxyethanol + water with traces of 2-(2-hexyloxyethoxy) ethanol, at the water-rich part of the phase diagram, is studied with light scattering. Our results indicate that the cloudy region corresponds to a phase separation. We present the cloud points for two series of mixtures at constant 2-(2-hexyloxyethoxy) ethanol concentration (I and 1.5 wt% ). Some comments are made to explain the apparent stability of that cloudy region.

Castillo, R.; Rivera, M.

1995-05-01

136

Ionic liquid/water mixtures: from hostility to conciliation.  

PubMed

Water was originally inimical to ionic liquids (ILs) especially in the analysis of their detailed properties. Various data on the properties of ILs indicate that there are two ways to design functions of ionic liquids. The first is to change the structure of component ions, to provide "task-specific ILs". The second is to mix ILs with other components, such as other ILs, organic solvents or water. Mixing makes it easy to control the properties of the solution. In this strategy, water is now a very important partner. Below, we summarise our recent results on the properties of IL/water mixtures. Stable phase separation is an effective method in some separation processes. Conversely, a dynamic phase change between a homogeneous mixture and separation of phases is important in many fields. Analysis of the relation between phase behaviour and the hydration state of the component ions indicates that the pattern of phase separation is governed by the hydrophilicity of the ions. Sufficiently hydrophilic ions yielded ILs that are miscible with water, and hydrophobic ions gave stable phase separation with water. ILs composed of hydrophobic but hydrated ions undergo a dynamic phase change between a homogeneous mixture and separate phases according to temperature. ILs having more than seven water molecules per ion pair undergo this phase transition. These dynamic phase changes are considered, with some examples, and application is made to the separation of water-soluble proteins. PMID:22683915

Kohno, Yuki; Ohno, Hiroyuki

2012-07-21

137

Interaction and permeability of water with liquid crystalline thermoset  

NASA Astrophysics Data System (ADS)

The complex transport behavior of water in both liquid crystalline thermoset and non-liquid crystalline thermoset systems were investigated. The liquid crystalline thermoset was 4,4'-diglycidyloxy-alpha-methylstilbene with sulfanilamine (SAA) as the crosslinking agent, the non-liquid crystalline thermoset the diglycidyl ether of bisphenol A. The liquid crystalline thermosets have higher barrier properties than isotropic non-LC epoxy resins. The efficient chain packing of the smectic mesophase of the liquid crystalline thermosets is attributed as the main factor for this difference. Permeation testing results show that the diffusion coefficient, permeability, and solubility coefficient depend on the amine/epoxide functional ratio. FTIR results confirmed that hydrophilic groups in the crosslinked network are one of the major factors that control the sorption and diffusion of water in epoxy resins. Two possible water-epoxy hydrogen bond configurations are identified, namely hydrogen bond formation of water to amine groups and hydrogen bond formation of water molecules to hydroxyl groups. Thus, diffusion of water molecules into epoxy resins depends on two major factors, namely, the availability of appropriate microvoids in the cured network and the interaction between the water molecules and the epoxy resin matrix. Depression of glass transition temperature was revealed by dynamic mechanical thermal analysis. The intrinsic moisture sensitivity of the epoxy resins is traceable directly to the molecular structure of the network. The presence of polar groups provides the chemical basis for moisture sensitivity. The entropy model can satisfactorily describe the nature of the depression of glass transition temperature. The hypothesis of a heterogeneous network was confirmed by phase images of atomic force microscopy for all of the epoxy samples. High crosslinked domains are surrounded by low crosslinked regions. Quantitative analysis of phase images shows that the relative amount of hard-phase changes with amine/epoxide functional ratio. Based on the analysis of morphology and interaction of water-epoxy resin, a theoretical model for the diffusion coefficient was set up for the first time by considering two factors: morphology and hydrogen bonding. This model relates the fraction of the hard-phase and the hydrogen bonding capacity to the experimental diffusion coefficients.

Feng, Jianxun

138

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

E-print Network

of the shoulder well is chosen so that the resulting potential reproduces the oxygen-oxygen radial distribution, the rise in density on isobaric heating (density anomaly) and the increase in molecular mobility and mobility underlying this diverse set of liquids with water-like anomalies, can be un- derstood in terms

Barbosa, Marcia C. B.

139

Anisotropic behavior of water in ferroelectric liquid crystals  

NASA Astrophysics Data System (ADS)

The outcome of water addition in ferroelectric liquid crystal (FLC) has been investigated in uniform and defect-free homogeneous and homeotropically aligned monodomain sample cells from electro-optical and dielectric spectroscopic measurements. The lagging in optical response between nonconducting (spatially variable switching) and conducting (conventional switching) portions of water added FLC sample cell has been observed by frequency-dependent electro-optical studies. The bias-dependent water related new relaxation peak near the conventional Goldstone mode relaxation process has been observed only in the homogeneous alignment and not in the homeotropic one. Further, the significant increment in dielectric anisotropy as well as faster diffusion of water along long molecular axis than short molecular axis has also been monitored. These studies strongly suggest that the distribution of water is anisotropic in FLC medium and could be the reason for new relaxation peak in the water added FLC sample.

Singh, G.; Choudhary, A.; Vijaya Prakash, G.; Biradar, A. M.

2010-05-01

140

Nanomechanics and dynamics of confined water and other liquids  

NASA Astrophysics Data System (ADS)

From oil recovery to molecular biology, nanoconfined water plays an important role in many areas of research. However, the mechanics and dynamics of nanoconfined water are not well understood. Over the last ten years, a number of groups have measured the mechanics of confined water using atomic force microscopy (AFM) or surface force apparatus (SFA) - often with contradictory results. At Wayne State University, we have developed high resolution AFMs for ultra-small amplitude, linear measurements of the mechanics and dynamics of confined liquids. We have shown that water shows a distinct slow-down in dynamics under confinement (PRB 2004), co-discovered a dynamic ``solidification'' in a model liquid (Langmuir 2006), and showed that normal and shear stiffness are closely related in confined liquids (Rev. Sci. Instr. 2008). Recently, we found dynamic solidification also in water layers (PRL 2010), a finding that explains the contradictory findings in earlier measurements and points to surprisingly complex behavior in this seemingly simple system. Here we will review these findings, as well as present new findings that show the profound effects of ion concentration on these dynamical effects, as well as measurements of colloidal systems, which illustrate that some findings at the molecular scale can be understood from purely geometric considerations and are not dependent on molecular-scale interactions.

Hoffmann, Peter; Khan, Shah

2012-02-01

141

Nanomechanics and dynamics of confined water and other liquids  

NASA Astrophysics Data System (ADS)

From oil recovery to molecular biology, nanoconfined water plays an important role in many areas of research. However, the mechanics and dynamics of nanoconfined water are not well understood. Over the last ten years, a number of groups have measured the mechanics of confined water using atomic force microscopy (AFM) or surface force apparatus (SFA) - often with contradictory results. At Wayne State University, we have developed high resolution AFMs for ultra-small amplitude, linear measurements of the mechanics and dynamics of confined liquids. We have shown that water shows a distinct slow-down in dynamics under confinement (PRB 2004), co-discovered a dynamic ``solidification'' in a model liquid (Langmuir 2006), and showed that normal and shear stiffness are closely related in confined liquids (Rev. Sci. Instr. 2008). Recently, we found dynamic solidification also in water layers (PRL 2010), a finding that explains the contradictory findings in earlier measurements and points to surprisingly complex behavior in this seemingly simple system. Here we will review these findings, as well as present new findings that show the profound effects of ion concentration on these dynamical effects, as well as measurements of colloidal systems, which illustrate that some findings at the molecular scale can be understood from purely geometric considerations and are not dependent on molecular-scale interactions.

Hoffmann, Peter

2012-10-01

142

Probing Hydrophilic Interface of Solid/Liquid-Water by Nanoultrasonics  

PubMed Central

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 ngstrm 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

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

143

Probing hydrophilic interface of solid/liquid-water by nanoultrasonics.  

PubMed

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 ngstrm 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

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

2014-01-01

144

Probing Hydrophilic Interface of Solid/Liquid-Water by Nanoultrasonics  

NASA Astrophysics Data System (ADS)

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 ngstrm 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.

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

2014-09-01

145

A continuous mixture of two different dimers in liquid water.  

PubMed

It is hitherto thought that liquid water is composed of tetrahedrally coordinated molecules with an asymmetric interaction of the central molecule with neighboring molecules. Khne et al., Nat. Commun., 2013, 4, 1450 suggested that this asymmetry, energetic rather than geometric, is the cornerstone to reconcile the homogeneous and inhomogeneous viewpoints of liquid water. In order to investigate the geometric origin of that asymmetry, we have scrutinized Molecular Dynamics (MD) simulations of water through a careful analysis of the five-dimensional probability distribution function of Euler angles in which the relative positions and orientations of water molecules are obtained. We demonstrate that, beyond the ubiquitous tetrahedral structure with well-defined molecular dimers, there is a series of possible molecular orientations that define the structure. These orientations are generated by rotating the neighboring molecule around the O-H axis that is involved in the hydrogen bond scheme. Two of the possible orientations have a higher probability, giving rise to two kinds of dimers: one close to the lowest energy of a water dimer in vacuum with an almost perpendicular alignment of the dipole moment, and another one with a parallel orientation of the dipole moment which is less tightly bound. These two different dimers have an effect on the orientation of further water dipole moments up to a distance of ?6 . Liquid water can therefore be described as a continuous mixture of two kinds of dimers where the hydrogen bonds have the same geometry but the interaction energies are different due to a different mutual orientation of the dipoles of the participating water molecules. PMID:25308564

Pardo, L C; Henao, A; Busch, S; Gurdia, E; Tamarit, J Ll

2014-11-28

146

Water Tank with Capillary Air/Liquid Separation  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

147

30 CFR 250.217 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2010 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must...

2010-07-01

148

30 CFR 550.217 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2012 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must...

2012-07-01

149

30 CFR 550.217 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2014 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must...

2014-07-01

150

30 CFR 250.217 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2011 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must...

2011-07-01

151

30 CFR 550.217 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2013 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must...

2013-07-01

152

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

PubMed

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 ?-? 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. PMID:21879723

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

2011-10-19

153

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

SciTech Connect

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

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

2012-03-15

154

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

PubMed

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 Pietrainנ[German large whiteנGL] (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. PMID:24407602

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

2014-03-01

155

Liquid water transport in fuel cell gas diffusion layers Aimy Ming Jii Bazylak  

E-print Network

Liquid water transport in fuel cell gas diffusion layers by Aimy Ming Jii Bazylak Bachelor means, without the permission of the author. #12;ii Liquid water transport in fuel cell gas diffusion State University) Abstract Liquid water management has a major impact on the performance and durability

Victoria, University of

156

Microwave radiometer measurements at Liquid water path algorithm development and accuracy  

E-print Network

1 Microwave radiometer measurements at Chilbolton Liquid water path algorithm development the atmosphere 1.3Liquid water path retrieval 2. MICROWAVE RADIOMETERS. 2.1Radiometer description. 2.2 Radiometer calibration. 3. LIQUID WATER PATH RETRIEVAL ALGORITHM. 3.1 Relationship between radiometer output

Reading, University of

157

Photochemical Degradation of Organic Pollutants in Liquid Water and Ice  

NASA Astrophysics Data System (ADS)

Arctic snow and ice play an important role as reactive media in the environment. A variety of species are photochemically generated from snow/ice, including carbonyl compounds, alkyl halides, molecular halogens, and nitrogen oxides. However, the fate of anthropogenic organic pollutants in snow and ice is largely unknown. Volatile pollutants evaporate from lower, warmer latitudes and condense out in the higher, colder latitudes by a process known as global distillation, leading to enhanced concentrations of a variety of pollutants in polar regions. Here we present recent results of photochemical degradation studies of several important organic pollutants including aldrin, dieldrin, hexachlorobenzene, and 3,3',4,5'-tetrachlorobiphenyl. Direct and indirect (with H2O2) pathways were studied in both liquid water and ice forms. Aldrin and 3,3',4,5'-tetrachlorobiphenyl have shown the most reactivity, both degrading significantly via the direct and indirect pathway in liquid water and ice. Dieldrin has shown reactivity under both direct and indirect liquid conditions, while HCB is only reactive under indirect liquid conditions. These results indicate that ice can serve as an important reactive surface for anthropogenic organic pollutants. Snow/ice photochemistry should be included in models of pollutant fate, but further studies are necessary to determine which pollutants are most affected by ice photochemistry under typical environmental conditions.

Sprenkle, A. M.; Grannas, A. M.

2006-12-01

158

X-Ray Spectroscopy of the Liquid Water Surface  

NASA Astrophysics Data System (ADS)

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 using near-edge x-ray absorption fine-structure spectroscopy and density functional theory," J. Phys.: Condens. Matter 14, L221-L226 (2002).

Saykally, Richard

2004-03-01

159

A quantitative account of quantum effects in liquid water  

NASA Astrophysics Data System (ADS)

We report converged quantum statistical mechanical simulations of liquid water with the Thole-type Model (version 2.1), Flexible, polarizable (TTM2.1-F) interaction potential for water. Simulations of total length of 600ps with a 0.05fs time step for a periodic unit cell of 256 molecules with up to 32 replicas per atom suggest that the quantum effects contribute 1.010.02kcal/mol to the liquid enthalpy of formation at 298.15K. They furthermore demonstrate for the first time a quantitative agreement with experiment for the heights and broadening of the intramolecular OH and HH peaks in the radial distribution functions.

Fanourgakis, G. S.; Schenter, G. K.; Xantheas, S. S.

2006-10-01

160

Thrust Characteristics of Water/Liquid Nitrogen Rocket Engine  

NASA Astrophysics Data System (ADS)

When liquid nitrogen and heated water are mixed in a chamber, pressure increase due to evaporation expansion inside the chamber becomes high enough to generate thrust force for rocket propulsion. This thrust system is safer and environment-friendly compared to conventional rocket engines utilizing combustion process. This new type of rocket engine system is called "Water-Liquid Nitrogen rocket engine system" and it can be used for small payload mission with expected altitude of several kilometers. In this paper, experimentally obtained thrust characteristics are shown and analyzed. As a result, relations between the thrust force and the mixing chamber pressure are clarified. Also, it is found that the present injector can attain only half of the theoretically expected specific impulse due to insufficient mixing efficiency.

Watanabe, Rikio; Hayashi, Kohei; Iwao, Masaki; Ikawa, Keita; Tomita, Nobuyuki

161

Liquid-liquid equilibria for 2,3-butanediol + water + organic solvents at 303. 15 K  

SciTech Connect

2, 3-Butanediol, an important industrial chemical, is of interest because of its application as a solvent and liquid fuel additive. Liquid-liquid equilibria at 303.15 [+-] 0.5 K were measured for water + 2, 3-butanediol + butan-1-ol, + 3-methyl-1-butanol, + 4-methyl-2-pentanone, + tributyl phosphate, and + butyl acetate. Complete phase diagrams were obtained by evaluating the solubility and tie-line results for each ternary mixture. The consistency of the tie-line results was ascertained using an Othmer-Tobias plot. The distribution coefficient and separation factors were evaluated over the immiscibility region. Among the solvents studied, butan-1-ol is the most effective one though tributyl phosphate and 3-methyl-1-butanol may be preferred because of their low solubility and high selectivity.

Sharma, S.; Pandya, G.; Chakrabarti, T.; Khanna, P. (National Environmental Engineering Research Inst., Nagpur (India))

1994-10-01

162

Liquid-glass transition of water/salt mixtures  

NASA Astrophysics Data System (ADS)

Water is known to exhibit a number of anomalous behaviors and to be an exceptionally poor glass-former. However, both features are strongly affected by applying pressure or adding salt. This means that these two parameters have strong influence on physical factors controlling the unusual features of water. By using a water/salt mixture as a model system, we experimentally demonstrate that the glass-forming ability and the fragility of a water/salt mixture are closely related to its equilibrium phase diagram. The key to this link may be frustration between local ordering and global ordering toward the crystal. Relying on the same role of salt as pressure in water anomalies as a breaker of local tetrahedral order, we infer the behavior of water under pressure from that of a water/salt mixture. This scenario not only explains unusual behavior of water-type liquids such as water, Si and Ge under pressure, but also may provide a general explanation on the link between the equilibrium phase diagram, the glass-forming ability, and the fragility of various materials for a wide class of materials.

Kobayashi, Mika; Tanaka, Hajime

2013-02-01

163

Detection of Numerous Y Chromosome Biallelic Polymorphisms by Denaturing High-Performance Liquid Chromatography  

Microsoft Academic Search

Y chromosome haplotypes are particularly useful in deciphering human evolutionary history because they accentuate the effects of drift, migration, and range expansion. Significant acceleration of Y biallelic marker discovery and subsequent typing involving heteroduplex detection has been achieved by implementing an innovative and cost-efficient method called denaturing high-performance liquid chromatography (DHPLC). The power of the method resides in its sensitivity

Peter A. Underhill; Li Jin; Alice A. Lin; S. Qasim Mehdi; Trefor Jenkins; Douglas Vollrath; Ronald W. Davis; L. Luca Cavalli-Sforza; Peter J. Oefner

164

Liquid Crystalline Properties of Amyloid Protein Fibers in Water  

Microsoft Academic Search

We have studied the liquid crystalline features of two colloidal systems consisting of food protein amyloid fibrils in water, obtained by heat-denaturation and aggregation of beta-lactoglobulin, a globular dairy protein. The resulting fibrils, have a monodisperse cross section of about 4 nm and two groups of polydisperse contour lengths: (i) fibrils 1-10 mum long, showing semiflexible polyeletrolyte-like behaviour and (ii)

Raffaele Mezzenga; Jin-Mi Jung

2010-01-01

165

Investigating evidence of geologically recent liquid water on Mars  

NASA Astrophysics Data System (ADS)

Geologically young gullies have been proposed to be evidence of recent liquid water on Mars. This dissertation details work I have done to address issues surrounding the Martian gullies and recent water on Mars. In order to determine the elevations at which gullies occur, I created a set of Interactive Data Language programs and Unix C-shell scripts to coregister Mars Orbiter Laser Altimeter topography with high resolution Mars images. My scripts represent the first public method that does this. Recently, the Mars Orbiter Camera detected changes in the form of new bright deposits in two gullies. The High Resolution Imaging Science Experiment (HiRISE) camera detected more gullies with bright deposits. I used my scripts to identify some of the best candidates for liquid water formation based on their shallow average slopes. A Digital Elevation Model (DEM) was produced using HiRISE stereo images of my selected candidates in Hale Crater. I model two gullies with bright slope deposits in Hale Crater and find that both water- rich and sediment-rich flows could reproduce the bright deposits' locations and morphologies. Since liquid water is rarely stable on Mars today, I suggest that dry flows formed the bright deposits. The channel gradient where flows deposit, the apex slope, can tell us whether a flow was likely dry and non-fluidized (slopes ~21) or fluidized (shallower slopes). I measured the apex slope of 75 gullies located in five HiRISE DEMs. I find that 72% of the gullies studied were likely emplaced by a fluidized flow. I also find that modified gullies are more likely to have a fluidized emplacement than relatively fresh gullies. My results suggest that there is no evidence requiring water-rich flows in gullies today. Understanding the concept of water on Mars is crucial to understanding NASA's Mars Exploration Strategy, "Follow the Water." I undertook a study investigating alternative conceptions about water on Mars held by middle school science teachers to understand what they hear when scientists say "water on Mars." All study participants had alternative conceptions about water on Mars. I suggest focus topics for space science education programs.

Kolb, Kelly Jean

2009-06-01

166

Electrons and Hydrogen-Bond Connectivity in Liquid Water  

SciTech Connect

The network connectivity in liquid water is revised in terms of electronic signatures of hydrogen bonds (HBs) instead of geometric criteria, in view of recent x-ray absorption studies. The analysis is based on ab initio molecular-dynamics simulations at ambient conditions. Even if instantaneous threadlike structures are observed in the electronic network, they continuously reshape in oscillations reminiscent of the r and t modes in ice ({tau}{approx}170 fs). However, two water molecules initially joined by a HB remain effectively bound over many periods regardless of its electronic signature.

Fernandez-Serra, M.V. [Laboratoire de Physique de la Matiere Condensee et Nanostructures (LPMCN) and UMR CNRS 5586, Universite Claude Bernard Lyon 1, 69622 Villeurbanne (France); Artacho, Emilio [Donostia International Physics Center, Universidad del Pais Vasco, 20080 San Sebastian (Spain); Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)

2006-01-13

167

Measuring Low Concentrations of Liquid Water in Soil  

NASA Technical Reports Server (NTRS)

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.

Buehler, Martin

2009-01-01

168

Optically Thin Liquid Water Clouds: Their Importance and Our Challenge  

NASA Technical Reports Server (NTRS)

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.

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

169

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

PubMed

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 ?g/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. PMID:25641819

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

2015-03-01

170

Liquid-liquid transition in the ST2 model of water  

NASA Astrophysics Data System (ADS)

We present clear evidence of the existence of a metastable liquid-liquid phase transition in the ST2 model of water. Using four different techniques (the weighted histogram analysis method with single-particle moves, well-tempered metadynamics with single-particle moves, weighted histograms with parallel tempering and collective particle moves, and conventional molecular dynamics), we calculate the free energy surface over a range of thermodynamic conditions, we perform a finite size scaling analysis for the free energy barrier between the coexisting liquid phases, we demonstrate the attainment of diffusive behavior, and we perform stringent thermodynamic consistency checks. The results provide conclusive evidence of a first-order liquid-liquid transition. We also show that structural equilibration in the sluggish low-density phase is attained over the time scale of our simulations, and that crystallization times are significantly longer than structural equilibration, even under deeply supercooled conditions. We place our results in the context of the theory of metastability.

Debenedetti, Pablo

2013-03-01

171

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

PubMed

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. PMID:25149003

Lpez-Garca, Ignacio; Briceo, Marisol; Vicente-Martnez, Yesica; Hernndez-Crdoba, Manuel

2015-01-15

172

Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water  

NASA Astrophysics Data System (ADS)

Most liquids can form a single glass or amorphous state when cooled sufficiently fast (in order to prevent crystallization). However, there are a few substances that are relevant to scientific and technological applications which can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation evolves into a first-order liquid-liquid phase transition (LLPT) at temperatures above the glass transition temperature Tg. However, obtaining direct experimental evidence of the LLPT has been challenging since the LLPT occurs at conditions where water rapidly crystallizes. In this talk, I will (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models -- one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLPT may exist for the case of water.

Giovambattista, Nicolas

2013-03-01

173

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

SciTech Connect

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.

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

2004-05-25

174

A 'first principles' potential energy surface for liquid water from VRT spectroscopy of water clusters.  

PubMed

We present results of gas phase cluster and liquid water simulations from the recently determined VRT(ASP-W)III water dimer potential energy surface (the third fitting of the Anisotropic Site Potential with Woermer dispersion to vibration-rotation-tunnelling data). 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 with those from ab initio molecular dynamics, other potentials of 'spectroscopic' accuracy and with experiment. The results herein represent the first time to the authors' knowledge that a 'spectroscopic' potential surface is able to correctly model condensed phase properties of water. PMID:15664895

Goldman, Nir; Leforestier, Claude; Saykally, R J

2005-02-15

175

Relationship between structural order and the anomalies of liquid water  

NASA Astrophysics Data System (ADS)

In contrast to crystalline solids-for which a precise framework exists for describing structure-quantifying structural order in liquids and glasses has proved more difficult because even though such systems possess short-range order, they lack long-range crystalline order. Some progress has been made using model systems of hard spheres, but it remains difficult to describe accurately liquids such as water, where directional attractions (hydrogen bonds) combine with short-range repulsions to determine the relative orientation of neighbouring molecules as well as their instantaneous separation. This difficulty is particularly relevant when discussing the anomalous kinetic and thermodynamic properties of water, which have long been interpreted qualitatively in terms of underlying structural causes. Here we attempt to gain a quantitative understanding of these structure-property relationships through the study of translational and orientational order in a model of water. Using molecular dynamics simulations, we identify a structurally anomalous region-bounded by loci of maximum orientational order (at low densities) and minimum translational order (at high densities)-in which order decreases on compression, and where orientational and translational order are strongly coupled. This region encloses the entire range of temperatures and densities for which the anomalous diffusivity and thermal expansion coefficient of water are observed, and enables us to quantify the degree of structural order needed for these anomalies to occur. We also find that these structural, kinetic and thermodynamic anomalies constitute a cascade: they occur consecutively as the degree of order is increased.

Errington, Jeffrey R.; Debenedetti, Pablo G.

2001-01-01

176

Gas-Liquid Coexistence in the Primitive Model for Water  

E-print Network

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

F. Romano; P. Tartaglia; F. Sciortino

2007-05-08

177

Meteoritic strikes and liquid water pools on Titan  

NASA Astrophysics Data System (ADS)

Impact cratering must be an important process on Titan, since the airless icy satellites of the saturnian system exhibit high crater densities. However, Titan's thick atmosphere efficiently decelerates all comets smaller than 2-3 km in diameter. The resulting airblasts may heat an atmosphere locally and distribute cometary materials around Titan. We performed 3D numerical simulations of cometary impacts on Titan varying the comet size from 3 to 30 km and the crust thickness -from 10 km (ancient Titan) to 50 km (the last 1 Gyr). The surface temperature is 94 K, the water mantle is at 273 K with a calculated crustal thermal gradient in between. Cratering processes on Titan are mainly defined by the thickness of its crust. Even the smallest comets easily breached an ancient Titan's crust, delivering huge amount of water (both, molten crust and underlying ocean). The shape of these craters differs substantially from standard complex craters: a central uplift does not emerge; the rim is substantially eroded by liquid flows. Moreover, any crater relaxes quickly in the high-temperature (hence, low-viscosity) ice. Indeed, recent Cassini observations revealed a substantial dearth of impact craters on the surface with an approximate surface age of < 1 Gyr. Under modern conditions only < 10-km-diameter comets produce a crater in ice, while larger comets breach the crust creating an open water pool. The freezing time of an impact pool with a thickness H [km] is 26H2 [kyr]. If ammonia is present at non-negligible levels then the time for complete freezing could be significantly longer. Comparison of the impact rates and the cooling time of water shows that a persistent surface water layer on Titan does not exist for the present thermal conditions and for the present impact rate in saturnian system. Nonetheless, a non-negligible fraction of Titan's hydrocarbon (including ethane) deposits might have been exposed to liquid water on the surface over Titan's history. The interaction of liquid water may result in the clathration of ethane in and around the impact site. As ethane-rich clathrates have a density larger than water ice or methane clathrates, crustal overturn may occur.

Artemieva, Natalia; Lunine, Jonathan

178

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

E-print Network

We investigate the phase diagram of a three-dimensional associating gas $(ALG)$ model. This model combines orientational ice-like interactions and ``van der Waals'' that might be repulsive, representing, in this case, a penalty for distortion of hydrogen bonds. These interactions can be interpreted as two competing distances making the connection between this model and continuous isotropic soft-core potentials. We present Monte Carlo studies of the $ALG$ model showing the presence of two liquid phase, two critical points and A density anomaly.

Mauricio Girardi; Aline L. Balladares; Vera B. Henriques; Marcia C. Barbosa

2006-12-09

179

Combustion of Liquid Fuels Spilled on Water. Prediction of Time to Start of Boilover  

Microsoft Academic Search

The combustion of a liquid fuel floating on water is a problem of interest because of its potential environmental and safety consequences. When a liquid fuel is burning under these conditions, the presence of the water may cause some particular effects due to heat transfer to the water. If the fuel layer is thin, heat losses to the water may

J. P. GARO; P. GILLARD; J. P. VANTELON; A. C. FERNANDEZ-PELLO

1999-01-01

180

Spectrophotometric determination of mercury in water samples after preconcentration using dispersive liquid-liquid microextraction.  

PubMed

A simple method for the determination of mercury in water samples after preconcentration using dispersive liquid-liquid microextraction is described. The procedure is based on the extraction of mercury in the form of a complex and its subsequent determination by spectrophotometry. The complex is formed between Hg(II) and 2-(2-benzothiazolylazo)-p-cresol. The detection at 650 nm is performed directly in the metal-rich phase, which is spread on a triacetylcellulose membrane. The method eliminates the need to use a cuvet or large quantities of samples and reagents. The parameters that influence the preconcentration were studied, and the analytical characteristics were determined. The enrichment factor and the consumptive index for this method were 64 and 0.16 mL, respectively. The LOD (3.3 microg/L) and LOQ (11.1 microg/L) were also determined. The accuracy of the method was tested by the determination of mercury in certified reference materials BCR 397 (Human Hair) and SRM 2781 (Domestic Sludge). The method was applied to the determination of mercury in samples of drinking water, sea water, and river water. PMID:22468364

Lemos, Valfredo Azevedo; dos Santos, Liz Oliveira; Silva, Eldevan dos Santos; Vieira, Emanuel Vitor dos Santos

2012-01-01

181

Thermodynamic properties of liquid water from a polarizable intermolecular potential  

NASA Astrophysics Data System (ADS)

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.

Yigzawe, Tesfaye M.; Sadus, Richard J.

2013-01-01

182

Vapor liquid equilibrium simulations of the SCPDP model of water  

NASA Astrophysics Data System (ADS)

Molecular simulations were carried out using the self-consistent point dipole polarizability model (SCPDP) of water in the region of vapor-liquid equilibrium. The methods of isothermal-isochoric molecular dynamics (NVT-MD) and Gibbs ensemble Monte Carlo (GEMC) were employed to calculate orthobaric densities and vapor pressures; NVT-MD also yields surface tensions and interface thickness. Agreement was found between the two methods, particularly at lower temperatures, but compared with experimental results, this model over-predicts vapor pressures and densities, and under-predicts the liquid density, surface tension, and interface thickness. The interface thickness predicted by the SCPDP model showed better agreement with experimental results than a simpler extended point charge model (SPC/E).

Rivera, J. L.; Predota, M.; Chialvo, A. A.; Cummings, P. T.

2002-05-01

183

Development of a liquid-fed water resistojet  

NASA Technical Reports Server (NTRS)

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.

Morren, W. Earl; Stone, James R.

1988-01-01

184

Influence of Water on Diffusion in Imidazolium-Based Ionic Liquids by NMR  

E-print Network

Influence of Water on Diffusion in Imidazolium-Based Ionic Liquids by NMR Sergey Vasenkov AMRIS-ethyl-3- methylimidazolium-based ionic liquids. This technique combines advantages of high field (17.6 T recording of an NMR signal from small amounts of water added to the ionic liquids. Using high gradients

185

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

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid-liquid microextraction method was proposed for the extraction and concentration of 17-?-estradiol, 17-?-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. PMID:25146581

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

2014-11-01

186

Interfacial thermodynamics of water and six other liquid solvents.  

PubMed

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. PMID:24820859

Pascal, Tod A; Goddard, William A

2014-06-01

187

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

PubMed

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 following predicted climate change. PMID:24669746

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

2014-02-01

188

Liquid-liquid equilibria of the ternary system water + acetic acid + 1-hexanol  

SciTech Connect

The recovery of organic acids from dilute solutions resulting from fermentation processes is important and many solvents have been tried to improve such recovery. Liquid-liquid equilibria for the ternary system water + acetic acid + 1-hexanol were measured over a temperature range of (288 to 323) K. The results were used to estimate the interaction parameters between each of the three compounds for the NRTL and UNIQUAC models and between each of the main groups of H{sub 2}O, CH{sub 2} (paraffinic CH{sub 2}), OH, and COOH for the UNIFAC model as a function of temperature. The estimated interaction parameters were successfully used to predict the equilibrium compositions by the three models. The NRTL equation was the most accurate model in correlating the overall equilibrium compositions of the studied system. The UNIQUAC and UNIFAC models satisfactorily predicted the equilibrium compositions.

Fahim, M.A. [Kuwait Univ., Safat (Kuwait). Dept. of Chemical Engineering] [Kuwait Univ., Safat (Kuwait). Dept. of Chemical Engineering; Al-Muhtaseb, S.A.; Al-Nashef, I.M. [U.A.E. Univ., Al-Ain (United Arab Emirates). Dept. of Chemical and Petroleum Engineering] [U.A.E. Univ., Al-Ain (United Arab Emirates). Dept. of Chemical and Petroleum Engineering

1997-01-01

189

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

E-print Network

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

V. K. Konyukhov

2009-09-23

190

Radar and the Detection of Liquid Water on Mars  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

191

Investigation of a liquid-fed water resistojet plume  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

192

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

SciTech Connect

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.

Chempath, Shaji [Los Alamos National Laboratory; Pratt, Lawrence R [TULANE UNIV

2008-01-01

193

An SCC-DFTB Repulsive Potential for Various ZnO Polymorphs and the ZnOWater System  

PubMed Central

We have developed an efficient scheme for the generation of accurate repulsive potentials for self-consistent charge density-functional-based tight-binding calculations, which involves energy-volume scans of bulk polymorphs with different coordination numbers. The scheme was used to generate an optimized parameter set for various ZnO polymorphs. The new potential was subsequently tested for ZnO bulk, surface, and nanowire systems as well as for water adsorption on the low-index wurtzite (101?0) and (112?0) surfaces. By comparison to results obtained at the density functional level of theory, we show that the newly generated repulsive potential is highly transferable and capable of capturing most of the relevant chemistry of ZnO and the ZnO/water interface. PMID:23991228

2013-01-01

194

Application of liquid-liquid-liquid microextraction and high-performance liquid-chromatography for the determination of sulfonamides in water.  

PubMed

This work presents a novel liquid-liquid-liquid microextraction (LLLME) technique for the extraction of sulfonamides from aqueous systems; it combines with high-performance liquid-chromatography-ultraviolet absorbance detection (HPLC/UV). In this experiment the sulfonamides were successively extracted from a donor phase (i.e., a water sample) into several microliters of an organic phase and then from the organic phase into an acceptor phase (i.e., an aqueous extract) by LLLME. The following separation and quantitative analyses were performed using HPLC/UV with 265 nm detection. Extraction condition such as solvent identity, agitation, extraction time, acceptor phase NaOH concentration, donor phase pH, and salt addition were optimized. Relative standard deviation (RSD, 2.6-5.3%), coefficient of estimation (R2, 0.9972-0.9999), and method detection limit (MDL, 0.11-0.77 ng mL(-1)) were achieved under the selected conditions. The proposed method was successfully applied to the analyses of three practical water samples and the relative recoveries of sulfonamides from the spiked water samples were in the range of 86.2-108.7%. The proposed method also confirms microextraction to be robust to monitoring trace levels of sulfacetamide, sulfadiazine, sulfathiazole, sulfamerazine, sulfadimidine, sulfamonomethoxine, sulfamethoxazole, and sulfaquinoxaline in aqueous samples. PMID:18331856

Lin, Che-Yi; Huang, Shang-Da

2008-03-31

195

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...

196

Hot electron dominated rapid transverse ionization growth in liquid water.  

PubMed

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-?m-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. PMID:21716461

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

2011-06-20

197

Thermodynamic mechanism of density anomaly of liquid water  

NASA Astrophysics Data System (ADS)

Although density anomaly of liquid water has long been studied by many different authors up to now, it is not still cleared what thermodynamic mechanism induces the anomaly. The thermodynamic properties of substances are determined by interparticle interactions. We analyze what characteristics of pair potential cause the density anomaly on the basis of statistical mechanics and thermodynamics using a thermodynamically self-consistent Ornstein-Zernike approximation (SCOZA). We consider a fluid of spherical particles with a pair potential given by a hard-core repulsion plus a soft-repulsion and an attraction. We show that the density anomaly occurs when the value of the soft-repulsive potential at hard-core contact is in some proper range, and the range depends on the attraction. Further, we show that the behavior of the excess internal energy plays an essential role in the density anomaly and the behavior is mainly determined by the values of the soft-repulsive potential, especially near the hard core contact. Our results show that most of ideas put forward up to now are not the direct causes of the density anomaly of liquid water.

Yasutomi, Makoto

2015-03-01

198

The BALTEX Cloud Liquid Water Network: CLIWA-NET  

NASA Astrophysics Data System (ADS)

The focus of the BALTEX Cloud Liquid Water Network (CLIWA-NET) is the observation of cloud liquid water and vertical cloud structures, and the evaluation and improvement of model cloud parameterizations. The prototype of a European Cloud observation Network consisting of a network of advanced ground-based remote sensing stations and satellite observations was successfully established within three measurement campaigns. While the first two campaigns (CNN I and II) were performed on a continental scale the third, the BALTEX BRIDGE CAMPAIGN (BBC) performed in conjunction with the 4D-Clouds project (see contribution by Venema et al.), concentrated on a regional network in the Netherlands. Macro- and microphysical cloud parameters were derived from AVHRR and AMSU satellite data. The BALTRAD radar network provided precipitation fields. All measurements were used to evaluate predictions of cloud parameters of four leading atmospheric models. Special focus was put on boundary layer clouds, the aspect of model resolution (vertical and horizontal), cloud overlap assumptions, and the daily cycle of cloudiness.

Crewell, S.; Cliwa-Net Team

2003-04-01

199

Solvation response of polar liquid mixtures: Water-dimethylsulfoxide  

NASA Astrophysics Data System (ADS)

The solvation dynamics following the instantaneous creation of a positive or negative electronic charge in a previously neutral solute immersed in different water-dimethyl sulfoxide (DMSO) mixtures, spanning the entire composition range, is analyzed by molecular dynamics simulations. The solvation responses are strongly dependent on the sign of the solute charge, being considerably faster in the presence of cations for all mixtures considered. In terms of the composition dependence, the mixtures' solvation response to the creation of the anion departs substantially from the pure solvents', whereas for the cation, the mixtures' responses are close to those exhibited by pure DMSO. In the case of anions, the mixture overall solvation time, defined as the time integral of the nonequilibrium response, can be as large as ten times the solvation time in pure DMSO, the slowest of the two cosolvents. The DMSO contribution to the mixtures' solvation response may present an intriguing negative branch in the rotational-diffusion regime which persists for times much longer than the time scales typically found in other polar liquids and mixtures. This negative portion is nearly cancelled by an equally long-lasting positive contribution from water, resulting in a fast-decaying, total response curve which is typical of many polar liquid environments. This behavior is rationalized in terms of the time evolution of the first solvation shell around each type of solute.

Laria, Daniel; Skaf, Munir S.

1999-07-01

200

Stability of amorphous silica-alumina in hot liquid water.  

PubMed

Herein, the hydrothermal stability of amorphous silica-alumina (ASA) is investigated under conditions relevant for the catalytic conversion of biomass, namely in liquid water at 200?C. The hydrothermal stability of ASA is much higher than that of pure silica or alumina. Interestingly, the synthetic procedure used plays a major role in its resultant stability: ASA prepared by cogelation (CG) lost its microporous structure, owing to hydrolysis of the siloxane bonds, but the resulting mesoporous material still had a considerable surface area. ASA prepared by deposition precipitation (DP) contained a silicon-rich core and an aluminum-rich shell. In hot liquid water, the latter structure was transformed into a layer of amorphous boehmite, which protected the particle from further hydrolysis. The surface area showed relatively minor changes during the transformation. Independent of the synthetic method used, the ASAs retained a considerable concentration of acid sites. The concentration of acid sites qualitatively followed the changes in surface area, but the changes were less pronounced. The performance of different ASAs for the hydrolysis of cellobiose into glucose is compared. PMID:24124062

Hahn, Maximilian W; Copeland, John R; van Pelt, Adam H; Sievers, Carsten

2013-12-01

201

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

EPA Science Inventory

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

202

Journal of Power Sources 170 (2007) 334344 Experimental investigation of liquid water formation and transport  

E-print Network

Journal of Power Sources 170 (2007) 334344 Experimental investigation of liquid water formation 3 April 2007 Available online 18 April 2007 Abstract Liquid water formation and transport were. We examined the effectiveness of various gas diffusion layer (GDL) materials in removing water away

Prasad, Ajay K.

2007-01-01

203

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

204

Routine use of PCR-restriction fragment length polymorphism analysis for identification of mycobacteria growing in liquid media.  

PubMed Central

A PCR-restriction fragment length polymorphism (PCR-RFLP) procedure capable of rapidly identifying 28 species of clinically encountered mycobacteria was evaluated for use in the routine identification of acid-fast isolates growing in BACTEC 12B and 13A liquid media. PCR-RFLP identified 100 of 103 acid-fast isolates recovered from 610 patient specimens submitted for culture during the study. The three isolates unidentifiable by PCR-RFLP produced restriction patterns not included in the PCR-RFLP algorithm and could therefore not be assigned to a species. These isolates were characterized by their morphologic and biochemical characteristics. Two of the isolates were identified as M. terrae complex and M. gordonae. The third isolate could not be definitively identified and could only be characterized as a Mycobacterium sp. most closely resembling M. chelonae. PCR-RFLP identifications agreed with the conventional identifications for 96 of the 100 isolates identified by PCR-RFLP. Subsequent identification of the four discordant isolates by gas chromatography analysis supported the PCR-RFLP identification of each isolate. Amplification products were also obtained from isolates of Streptococcus albus and Rhodococcus equi recovered from patient specimens; however, the restriction patterns of these nonmycobacterial species did not resemble the patterns of any mycobacterial species included in the PCR-RFLP algorithm. PCR-RFLP seems to be a reliable procedure for the routine identification of mycobacteria and has the potential for providing identifications of mycobacterial isolates which are more accurate than conventional identification techniques based on morphologic and biochemical characteristics. PMID:8968884

Taylor, T B; Patterson, C; Hale, Y; Safranek, W W

1997-01-01

205

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

206

Behavior of clathrate hydrate formation at the boundary of liquid water and a fluorocarbon in liquid or vapor state  

Microsoft Academic Search

Observational studies have been carried out to reveal the mechanistic aspects of the formation of clathrate hydrate, crystalline solid, at the boundary of water in the liquid state and a fluorocarbon (HFC-134a; CF3CH2F) in the liquid or vapor state. The surface morphology of the hydrate layer formed at the interface depends strongly on the degree of saturation of the water

Makoto Sugaya; Yasuhiko H. Mori

1996-01-01

207

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitudes  

NASA Astrophysics Data System (ADS)

Data from the Special Sensor Microwave Imager (years 1987-2006), Advanced Microwave Scanning Radiometer, and a surface-based radiometer at Barrow, Alaska are examined for insights into the behavior of water vapor, cloud liquid water and rainrates over the northern high latitudes. Screening for sea ice is accomplished by combining an independent dataset of monthly-mean sea ice fractions with the water vapor path (WVP), cloud liquid water path (LWP), and rainrate (RR) retrievals. The Wentz water vapor path retrieval shows no sensitivity to a proxy for sub-pixel sea ice presence, while the Wentz liquid water path retrievals are sensitive to sea ice presence during summertime when atmospheric variability is high but otherwise their sea-ice screening appears effective. The rainrate retrieval is highly sensitive to sea ice. The seasonal cycle and 1987-2006 time trends are examined. The WVP annual cycle has an amplitude of 1 cm with a July maximum phasing that is consistent with a continental influence. The springtime LWP increase usually occurs in tandem with the WVP increase and slightly lags the falltime WVP decrease. The maximum lag occurs over the northern Pacific, where the maximum LWP occurs in August, one month later than over the northern Atlantic, and is correlated to an August precipitation maximum. The strongest SSMI-derived trend is an increase in wintertime moisture south and southwest of Greenland, consistent with continental air outflow over warmer waters. An interesting feature is an autumnal increase in WVP and LWP north of the Bering Strait from 1989 to 2001 with a subsequent decrease in recent years. This cannot be explained by surface evaporation off of increased areas of open water and instead appears linked to recent decreases in cyclone activity. Winter and spring increases in LWP are noted in the surface-based dataset from Barrow, Alaska.

Zuidema, P.; Joyce, R.

2007-12-01

208

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

209

Modulated Terahertz Transmission through Sub-Wavelength Cu Grating by Liquid Water  

Microsoft Academic Search

Submerging the sub-wavelength Cu wire grating in liquid water, we prove that the transmission ration can be changed pronouncedly from 0.1 THz to 1.7 THz. The modulation of terahertz responses by liquid water is explained by the increasing effective electron mass in the plasmon picture. Due to this response, we extract the index of liquid water, and our results provide

Hua Chen; Xiu-Mei Wu; Yangwen-Xing

2010-01-01

210

Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son  

E-print Network

1 Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son , R.A. Yetter, V. Yang, and B: Supplemental materials submitted #12;2 Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son, R of nano-aluminum (nAl) and liquid water has been conducted. In particular, linear and mass-burning rates

Yang, Vigor

211

Seasonal and diurnal cycles of liquid water in snow  

NASA Astrophysics Data System (ADS)

The combination of upward-looking ground-penetrating radar (upGPR), automatic weather station (AWS) and lysimeter allows for continuous monitoring of bulk volumetric liquid water content (?w) within the snowpack and direct comparison with measurements of the corresponding outflow. The AWS data can be utilized to calculate energy fluxes between atmosphere and snowpack at the location of the station. While combining all data sets, we were able to quantify diurnal and seasonal changes in residual water content and relate modeled energy fluxes to water outflow. Since upGPR is a non-destructive monitoring technique, it is possible to continuously observe the snowpack and results are not biased through spatial variability of pit locations. Data analysis conducted for three consecutive years at the flat test site Weissfluhjoch, Davos, Switzerland showed that diurnal ?w variations never exceeded 2%. Without regard to days with new snow accumulation or refreezing, the diurnal patterns in ?w were very similar, with always daily peaks in the late afternoon (at about 17:00h) at the site. Although ?w values varied during a day up to 2%, the gradients during the season were very small. In 2012, for the whole melting period (>100 days), increases in ?w from day to day were 0.4% liquid water content on average. After the snowpack has become isothermal, positive energy fluxes result in outflow and increase the residual water content (?r). Our data showed that as long as potential melt - calculated for the determined energy fluxes - was exceeding measured outflow, ?r values were increasing but only until reaching a certain threshold. For all three years, the thresholds were similar at about ?r=4-5%. Only shortly before full ablation, these thresholds were surpassed. In two sloped test sites (about 22 degree slope angle) in Boise, Idaho, USA and above Davos, we installed upGPR systems as well. AWS data and energy-flux calculations for both slopes were extrapolated for the respective aspect and slope angle. Our data showed that snow stratigraphy highly influences ?r in slopes. As long as e.g. crusts ponded the vertical water flow, residual ?w of the whole snowpack was fairly low (

Heilig, Achim; Mitterer, Christoph; Schmid, Lino; Marshall, Hans-Peter; Schweizer, Jrg; Okorn, Robert; Eisen, Olaf

2014-05-01

212

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

PubMed

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. PMID:21171179

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

2011-01-01

213

Liquid water content variation with altitude in clouds over Europe  

NASA Astrophysics Data System (ADS)

Cloud water content is one of the most fundamental measurements in cloud physics. Knowledge of the vertical variability of cloud microphysical characteristics is important for a variety of reasons. The profile of liquid water content (LWC) partially governs the radiative transfer for cloudy atmospheres, LWC profiles improves our understanding of processes acting to form and maintain cloud systems and may lead to improvements in the representation of clouds in numerical models. Presently, in situ airborne measurements provide the most accurate information about cloud microphysical characteristics. This information can be used for verification of both numerical models and cloud remote sensing techniques. The aim of this paper was to analyze the liquid water content (LWC) measurements in clouds, in time of the aircraft flights. The aircraft and its platform ATMOSLAB - Airborne Laboratory for Environmental Atmospheric Research is property of the National Institute for Aerospace Research "Elie Carafoli" (INCAS), Bucharest, Romania. The airborne laboratory equipped for special research missions is based on a Hawker Beechcraft - King Air C90 GTx aircraft and is equipped with a sensors system CAPS - Cloud, Aerosol and Precipitation Spectrometer (30 bins, 0.51-50 m). The processed and analyzed measurements are acquired during 4 flights from Romania (Bucharest, 4425'57?N 2606'14?E) to Germany (Berlin 5230'2?N 1323'56?E) above the same region of Europe. The flight path was starting from Bucharest to the western part of Romania above Hungary, Austria at a cruse altitude between 6000-8500 m, and after 5 hours reaching Berlin. In total we acquired data during approximately 20 flight hours and we presented the vertical and horizontal LWC variations for different cloud types. The LWC values are similar for each type of cloud to values from literature. The vertical LWC profiles in the atmosphere measured during takeoff and landing of the aircraft have shown their dependence of the meteorological parameters.

Andreea, Boscornea; Sabina, Stefan

2013-04-01

214

Block Copolymer Micelle Shuttles between Water and Ionic Liquids  

NASA Astrophysics Data System (ADS)

The micelle shuttle is an interesting phenomenon recently discovered by our group: a reversible and intact migration of poly(butadiene- b-ethylene oxide) (PB-PEO) block copolymer micelles between water and a hydrophobic ionic liquid upon a simple temperature stimulus. The micelles allow for encapsulation of cargo molecules and the transfer enables control of their partitioning in the biphasic system. This simple round-trip delivery system can be used in delivery, reaction, and separations in synthesis and biphasic catalysis using ionic liquids. This thesis is aimed to systematically study the components, features, mechanism and possible applications of the micelle shuttle. For study on the components, several block copolymers and ionic liquids were employed to demonstrate the micelle shuttle, indicating the generality of the phenomenon. To control the loading and release of the micelle nanocarriers in the biphasic system, a thermoreversible micellization-transfer-demicellization shuttle was developed using a multiply thermosensitive block copolymer. The micelle shuttle was also demonstrated using micelles with different nanostructures, including spheres, cylinders, and vesicles. In particular, a new class of vesicles with ionic liquid interiors dispersed in water was developed using a vesicle shuttle. Permeability studies reflect the reasonably permeable membrane of the vesicles, which is desirable for potential applications of these responsive and stable vesicles as recyclable nanoreactors. As for research into the features, reversible and quantitative transfer appeared to be a common characteristic of the micelle shuttle. A strong temperature dependence of the micelle distribution in the biphasic system was observed, which is favorable for controlled delivery using the micelle shuttle. The transfer temperature determining the micelle partitioning in the biphasic system could be effectively tuned by simply using additives in the aqueous phase. To understand the transfer mechanism, the driving force, thermodynamics and kinetics of the micelle shuttle were investigated in detail utilizing shuttles of PEO homopolymers and dye-loaded PB-PEO micelles. A detailed multiple-step transfer mechanism was then proposed. To demonstrate possible applications, micelles formed by the commercial and inexpensive Pluronic block copolymer were employed as nanocarriers for delivery and extraction in the biphasic system. The vesicle shuttle was also utilized to transport various dyes in the biphasic system.

Bai, Zhifeng

215

30 CFR 550.248 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2012 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...wastes and discharges information and cooling water intake information must...

2012-07-01

216

30 CFR 250.248 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2011 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...wastes and discharges information and cooling water intake information must...

2011-07-01

217

30 CFR 550.248 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2013 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...wastes and discharges information and cooling water intake information must...

2013-07-01

218

30 CFR 550.248 - What solid and liquid wastes and discharges information and cooling water intake information must...  

Code of Federal Regulations, 2014 CFR

...liquid wastes and discharges information and cooling water intake information must accompany...liquid wastes and discharges information and cooling water intake information must accompany...wastes and discharges information and cooling water intake information must...

2014-07-01

219

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

220

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

PubMed Central

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

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

2001-01-01

221

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

PubMed

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 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 were present. Locations of stability appear to correlate with the distribution of valley networks. PMID:11226204

Lobitz, B; Wood, B L; Averner, M M; McKay, C P

2001-02-27

222

Water-mediated ion-ion interactions are enhanced at the water vapor-liquid interface.  

PubMed

There is overwhelming evidence that ions are present near the vapor-liquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ion-ion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vapor-liquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. "Sticky" electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from ?-helical to a hairpin-turn-like one in response to charging of its ends. PMID:24889634

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-06-17

223

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

USGS Publications Warehouse

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.

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

1969-01-01

224

Water-mediated ionion interactions are enhanced at the water vaporliquid interface  

PubMed Central

There is overwhelming evidence that ions are present near the vaporliquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ionion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vaporliquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. Sticky electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from ?-helical to a hairpin-turnlike one in response to charging of its ends. PMID:24889634

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-01-01

225

Detachment of Liquid-Water Droplets from Gas-Diffusion Layers  

SciTech Connect

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.

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

2011-07-01

226

Determination of phthalate esters in bottled water using dispersive liquidliquid microextraction coupled with GC-MS.  

PubMed

Dispersive liquid-liquid microextraction method was developed for the determination of the amount of phthalate esters in bottled drinking water samples and dispersive liquid-liquid microextraction samples were analyzed by GC-MS. Various experimental conditions influencing the extraction were optimized. Under the optimized conditions, very good linearity was observed for all analytes in a range between 0.05 and 150 ?g/L with coefficient of determination (R) between 0.995 and 0.999. The LODs based on S/N = 3 were 0.005-0.22 ?g/L. The reproducibility of dispersive liquid-liquid microextraction was evaluated. The RSDs were 1.3-5.2% (n = 3). The concentrations of phthalates were determined in bottled samples available in half shell. To understand the leaching profile of these phthalates from bottled water, bottles were exposed to direct sunlight during summer (temperature from 34-57C) and sampled at different intervals. Result showed that the proposed dispersive liquid-liquid microextraction is suitable for rapid determination of phthalates in bottled water and di-n-butyl, butyl benzyl, and bis-2-ethylhexyl phthalate compounds leaching from bottles up to 36 h. Thereafter, degradation of phthalates was observed. PMID:23936915

Mousa, Amayreh; Basheer, Chanbasha; Al-Arfaj, Abdul Rahman

2013-06-01

227

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

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 95ngmL(-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. PMID:25618715

Toledo-Neira, Carla; lvarez-Lueje, Alejandro

2015-03-01

228

Onset of simple liquid behaviour in modified water models  

SciTech Connect

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.

Prasad, Saurav; Chakravarty, Charusita, E-mail: charus@chemistry.iitd.ac.in [Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi 110016 (India)] [Department of Chemistry, Indian Institute of Technology-Delhi, New Delhi 110016 (India)

2014-04-28

229

Onset of simple liquid behaviour in modified water models.  

PubMed

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. PMID:24784281

Prasad, Saurav; Chakravarty, Charusita

2014-04-28

230

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

E-print Network

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

Emilio Del Giudice; Giuseppe Vitiello

2010-09-29

231

Conversion of lignocellulosics pretreated with liquid hot water to ethanol  

SciTech Connect

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.

Walsum, G.P. van; Laser, M.S.; Lynd, L.R. [Dartmouth College, Hanover, NH (United States)] [and others

1996-12-31

232

Electrokinetic Hydrogen Generation from Liquid WaterMicrojets  

SciTech Connect

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.

Duffin, Andrew M.; Saykally, Richard J.

2007-05-31

233

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

E-print Network

Dynamics of Isolated Water Molecules in a Sea of Ions in a Room Temperature Ionic Liquid Daryl B2O molecules in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium ionic liquids (RTIL), such as 1-butyl-3- methylimidazolium hexafluorophosphate (BmImPF6), are salts

Fayer, Michael D.

234

Green methodology based on dispersive liquid-liquid microextraction and micellar electrokinetic chromatography for 5-nitroimidazole analysis in water samples.  

PubMed

Dispersive liquid-liquid microextraction has been proposed as an extraction technique combined with micellar electrokinetic chromatography (MEKC) for the analysis of eight 5-nitroimidazole compounds, including some metabolites, in water samples. Determination has been carried out using a diode array detector, employing 20 mM sodium phosphate and 150 mM SDS as separation buffer. Separation has taken place under a voltage of 25 kV and a temperature of 20C. Samples were prepared in a buffer without micelles and they were hydrodynamically injected at 50 mbar for 25 s, producing a sweeping effect on the analytes for increasing sensitivity. Different factors involved in the dispersive liquid-liquid microextraction procedure were optimized, such as sample pH, nature, and volume of extraction and dispersive solvents in the mixture, percentage of NaCl added to sample and shaking time after the injection of the extraction and dispersive solvents. The method was characterized for water samples, achieving detection limits lower than 2.4 ?g/L. Trueness was checked in river, tap, and bottled water. Dispersive liquid-liquid microextraction combined with MEKC constitutes an easy, cheap, and green alternative for 5-nitroimidazole analysis in environmental water samples. PMID:23857677

Hernndez-Mesa, Maykel; Cruces-Blanco, Carmen; Garca-Campaa, Ana M

2013-09-01

235

Liquid Crystalline Properties of Amyloid Protein Fibers in Water  

NASA Astrophysics Data System (ADS)

We have studied the liquid crystalline features of two colloidal systems consisting of food protein amyloid fibrils in water, obtained by heat-denaturation and aggregation of ?-lactoglobulin, a globular dairy protein. The resulting fibrils, have a monodisperse cross section of about 4 nm and two groups of polydisperse contour lengths: (i) fibrils 1-10 ?m long, showing semiflexible polyeletrolyte-like behaviour and (ii) rigid rods 100-200 nm long. In both systems, the fibers are highly charged (+5 e/nm) and stable in water at low ionic strength (0.01 M) and low pH (pH 2). The physical properties of these systems are studied using a polymer physics approach and phase diagrams of these two systems are obtained by changing concentration and pH. Both systems exhibit rich phase behaviours. Interestingly, the experimentally measured isotropic-nematic phase transition was found to occur at concentrations more than one order of magnitude lower than what expected based on Onsager theory. Experimental results are revisited in terms of the Flory theory developed for rigid polymers in solvent of varying conditions.

Mezzenga, Raffaele; Jung, Jin-Mi

2010-03-01

236

Capillary waves at the water liquid-vapor interface  

NASA Astrophysics Data System (ADS)

Evidence for capillary waves at the liquid-vapor interface of water is presented from molecular dynamics simulations. The total interfacial width includes a correction term which depends logarithmically on the length L of the simulation cell parallel to the interface, and which is inversely proportional to the surface tension ?cw. Comparison of ?cw for system sizes up to 10^5 molecules to ?p, obtained from the difference between the pressure parallel and the pressure perpendicular to the interface, yields adequate agreement only if one fits the interfacial profile to an error function and not to a hyperbolic tangent, as often assumed. Results for ? for a number of atomistic three-site (SPC/E, TIP3P, TIP3P-CHARMM, and TIP3P-Ew) and four-site (TIP4P and TIP4P-Ew) non-polarizable water models are compared to experiment for temperatures from 300 K to 500 K, and for a variety of interaction cutoffs and reciprocal-space mesh refinements. Our results show that the SPC/E model is more accurate than the other available three-site models, while the original TIP3P model is closer to experimental data than its more recent parameterizations.

Ismail, Ahmed E.; Grest, Gary S.; Stevens, Mark J.

2006-03-01

237

Network analysis of proton transfer in liquid water  

SciTech Connect

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.

Shevchuk, Roman; Rao, Francesco, E-mail: francesco.rao@frias.uni-freiburg.de [Freiburg Institute for Advanced Studies, School of Soft Matter Research, Freiburg im Breisgau (Germany); Agmon, Noam [Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem (Israel)

2014-06-28

238

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

E-print Network

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

239

Near-Global Survey of Effective Droplet Radii in Liquid Water Clouds Using ISCCP Data  

Microsoft Academic Search

A global survey of cloud particle size variations can provide crucial constraints on how cloud processes determine cloud liquid water contents and their variation with temperature, and further, may indicate the magnitude of aerosol effects on clouds. A method, based on a complete radiative transfer model for AVHRR-measured radiances, is described for retrieving cloud particle radii in liquid water clouds

Qingyuan Han; William B. Rossow; Andrew A. Lacis

1994-01-01

240

Mixture-Model Approach to the Theory of Classical Fluids. II. Application to Liquid Water  

Microsoft Academic Search

The possibility of viewing liquid water as a mixture of various species is examined within the framework of classical statistical mechanics. In the first part of the paper the application of the so-called ``Two Structure Model'' to liquid water is examined. Two novel features of the present treatment are: (1) An exact classification procedure is employed to transform a one-component

A. Ben-Naim

1972-01-01

241

CFD Modeling of Gas-Liquid Flows in Water Electrolysis Units  

Microsoft Academic Search

This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to opti mize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid

Vladimir AGRANAT; Andrei TCHOUVELEV

242

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...

243

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

E-print Network

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

244

Equilibrium structural model of liquid water: Evidence from heat capacity, spectra, density, and other properties  

Microsoft Academic Search

Hydrogen bond strength depends on both temperature and pressure. The gradient for hydrogen bond strength with temperature, or pressure, depends upon the hydrogen bonded structure. These features create an intimate connection between quantum mechanics and thermodynamics in the structure of liquid water. The equilibrium structural model of liquid water developed from analysis of the heat capacity at constant pressure is

Ralph C. Dougherty; Louis N. Howard

1998-01-01

245

Lyotropic chromonic liquid crystal semiconductors for water-solution processable organic electronics  

E-print Network

Lyotropic chromonic liquid crystal semiconductors for water-solution processable organic August 2010; accepted 12 December 2010; published online 30 December 2010 We propose lyotropic chromonic liquid crystals LCLCs as a distinct class of materials for organic electronics. In water, the chromonic

Lavrentovich, Oleg D.

246

Living in a physical world IX. Making and maintaining liquid water  

Microsoft Academic Search

Metabolically active organisms contain water in its liquid phase I believe no exceptions are known. Lifes domain consists of the intersection of the circumstances under which liquid water will persist and those at the earths surface except as we artifi cially maintain some bit of that domain elsewhere. No single phase of a single compound so characterizes the

Steven Vogel

2006-01-01

247

Simulating liquid water for determining its structural and transport properties.  

PubMed

Molecular dynamics simulations are carried out for calculating structural and transport properties of pure liquid water, such as radial distribution functions and self-diffusion and viscosity coefficients, respectively. We employed reparameterized versions of the ab initio water potential by Niesar, Clementi and Corongiu (NCC). In order to investigate the role of the electrostatic contribution, the partial charges of the NCC model are adjusted so that to reproduce the dipole moment values of the SPC/E, SPC/Fw and TIP4P/2005 water models. The single and collective transport coefficients are obtained by employing the Green-Kubo relations at various temperatures. Additionally, in order to overcome convergence difficulties arising from the long correlation times of the stress-tensor autocorrelation functions, a previously reported fitting scheme was employed. The present results indicate that there is a significant relationship between the dipole moment value of the model, and the calculated transport coefficients. We found that by adjusting the molecular dipole moment of the NCC to the value of the TIP4P/2005, the obtained values for the self-diffusion and viscosity coefficients are in better agreement with experiment, compared to the values obtained with the original NCC model. Even though the predictions of the present model exhibits an overall correct behavior, we conclude that further improvements are still required. In order to achieve that, a careful reparameterization of the repulsion-dispersion terms of the potential model is proposed. Also, the effect of the inclusion of many-body effects such as polarizability, should also be investigated. PMID:23415103

Arismendi-Arrieta, Daniel; Medina, Juan S; Fanourgakis, George S; Prosmiti, Rita; Delgado-Barrio, Gerardo

2014-01-01

248

Model for the structure of the liquid water network  

SciTech Connect

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.

Grunwald, E.

1986-09-17

249

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

PubMed

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. PMID:24467614

Khan, Imran; Kurnia, Kiki A; Mutelet, Fabrice; Pinho, Simo P; Coutinho, Joo A P

2014-02-20

250

Determination of zinc in water samples by flame atomic absorption spectrometry after homogeneous liquid-liquid extraction  

Microsoft Academic Search

In this study, a new and simple homogeneous liquid-liquid extraction (HLLE) method based on a pH-independent phase-separation process was developed using a ternary solvent system [water-tetrabutylammonium\\u000a ion (TBA\\u000a +)-chloroform] for the preconcentration of Zn2+ ions. A Schiffs base ligand was used as the chelating agent prior to Zn2+ ions extraction. Flame atomic absorption spectrophotometry using acetylene-air flame was used for

Sh. Dehghan Abkenar; Z. Dahaghin; H. Bagheri Sadeghi; M. Hosseini; M. Salavati-Niasari

2011-01-01

251

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

SciTech Connect

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

Wang, Yun (University of California, Irvine, CA); Chen, Ken Shuang

2010-10-01

252

Stable positive nonsimple liquid for water-flooding subterranean formations  

Microsoft Academic Search

This is a method of treatment of a flooding liquid for recovering oil from a subterranean formation. The flooding medium is what is known as a positive nonsimple liquid. A positive nonsimple liquid is active in the sense that it adjusts its properties to flow at a rate whch is relatively insensitive to the permeability of the medium in which

M. K. Abdo; P. E. Blatz

1966-01-01

253

REVIEW ARTICLE: The high-frequency dynamics of liquid water  

NASA Astrophysics Data System (ADS)

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

Ruocco, Giancarlo; Sette, Francesco

1999-06-01

254

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

E-print Network

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

Peter O. Fedichev; Leonid I. Menshikov

2012-01-30

255

Boson peak in deeply cooled confined water: a possible way to explore the existence of the liquid-to-liquid transition in water.  

PubMed

The boson peak in deeply cooled water confined in nanopores is studied with inelastic neutron scattering. We show that in the (P, T) plane, the locus of the emergence of the boson peak is nearly parallel to the Widom line below ? 1600 bar. Above 1600 bar, the situation is different and from this difference the end pressure of the Widom line is estimated. The frequency and width of the boson peak correlate with the density of water, which suggests a method to distinguish the hypothetical "low-density liquid" and "high-density liquid" phases in deeply cooled water. PMID:24972226

Wang, Zhe; Liu, Kao-Hsiang; Le, Peisi; Li, Mingda; Chiang, Wei-Shan; Leo, Juscelino B; Copley, John R D; Tyagi, Madhusudan; Podlesnyak, Andrey; Kolesnikov, Alexander I; Mou, Chung-Yuan; Chen, Sow-Hsin

2014-06-13

256

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

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. PMID:16035352

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

2005-08-01

257

A realization of ``V structure'' in liquid water  

NASA Astrophysics Data System (ADS)

Results obtained from a molecular dynamics computer simulation of ST2 model water are used to generate a representation of liquid water which corresponds closely to the so-called ''V structure'' described by Eisenberg and Kauzmann. The representation is obtained by calculating a sequence of mean molecular positions, each mean being obtained by averaging the true dynamical center of mass and angular coordinates over a time comparable to the periods of hindered translational and rotational motion. For the averaging time used (?A = 0.2 psec), the results show significant narrowing in the distribution of nearest neighbor distances and of hydrogen bond angles. The distribution of molecular interaction energies manifests an associated shift to more negative values, and is somewhat narrower. Correspondingly, for a reasonable energetic criteria for an intact bond, the occurrence frequency of hydrogen bonds is dramatically increased in the V structure. The degree of connectivity of the hydrogen bond network shows parallel behavior. However, it is further shown that the energetic description of the V structure parallels that of the original, unmodified, structure, if corresponding intact hydrogen bond energy criteria are chosen reasonably. To obtain corresponding energetic structures, the criterion in the V structure must be shifted to more negative values to allow for the apparent loss there of a thermal excitation energyof about kBT. It is suggested that a time sequence of V structures can be a valuable source of information for the analysis of longer time scale dynamics, since the rapid and large amplitude librational motions are effectively averaged out. By the same token, a study of the temperature variation of the V structure should be able to separate the variation in structure arising from changes in the underlying hydrogen bond network from that due to changes in the thermal vibrational excitation of that network.

Hirata, Fumio; Rossky, Peter J.

1981-06-01

258

Derivation and evaluation of a flexible SPC model for liquid water  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of a new flexible water model are presented. The potential function is based on the simple point charge (SPC) model combined with an accurate experimental quartic intramolecular potential (CCL). This potential not only reproduces the key structural, dynamical and thermodynamical properties of liquid water, but also generates the correct values for both the absolute O-H vibrational frequency and the gas-to-liquid frequency shift. Thus, the model yields a value of ca. 3420 cm -1 for the peak maximum of the anharmonic OH stretching band for liquid water (experiment 3400 cm -1) and a corresponding gas-to-liquid downshift of -300 cm -1 (experiment -310 cm -1). The paper also emphasizes the importance of parameterizing correctly both the harmonic and anharmonic force constants in the gas-phase when developing flexible water models to be used in the liquid state.

Amira, Sami; Spngberg, Daniel; Hermansson, Kersti

2004-08-01

259

Dissociative ionization of liquid water induced by vibrational overtone excitation  

SciTech Connect

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.

Natzle, W.C.

1983-03-01

260

Water vapor, cloud liquid water paths, and rain rates over northern high latitude open seas  

NASA Astrophysics Data System (ADS)

Data from the Special Sensor Microwave Imager (SSMI; years 1987-2006), Advanced Microwave Scanning Radiometer, and a surface-based radiometer at Barrow, Alaska are examined for insights into the behavior of water vapor, cloud liquid water and rainrates over the northern high latitude seas. We evaluated two separate sets of retrievals, and achieved the best results through combining one that contained explicit monthly mean sea ice fractions with the Wentz V6 water vapor path (WVP), cloud liquid water path (LWP), and rainrate (RR) retrievals. The water vapor path retrieval shows no sensitivity to a proxy for sub-pixel sea ice presence, while the liquid water path retrievals are sensitive to sea ice presence during summertime but otherwise the Wentz internal sea-ice screening appears effective. The rainrate retrieval is highly sensitive to any sea ice during all seasons. The seasonal cycle and 1987-2006 time trends are examined. The WVP annual cycle has an amplitude of 1 cm at all locations, approximately double a broad winter minimum, with a July maximum phasing that is consistent with a continental influence. Little change occurs between January and April in WVP and LWP. The springtime LWP increase usually occurs in tandem with the WVP increase and slightly lags the falltime WVP decrease. The maximum lag occurs over the northern Pacific, where the maximum LWP occurs in August, one month later than over the northern Atlantic, and is correlated to an August precipitation maximum. The strongest SSMI-derived trend is an increase in wintertime moisture south of Greenland, with wintertime LWP increases in the Labrador Sea. North of the Bering Strait, where much of the recent summer and autumn sea ice loss has occurred, the autumn WVP and LWP increased from 1989 to 2001 with a subsequent LWP decrease in recent years. The recent decline appears linked to a decrease in cyclone activity. Winter and spring LWP increases from 2002 to the present are noted in the surface-based data set from Barrow, Alaska. Over the Barents Sea, where much of the recent winter sea ice loss has occurred, winter WVP and LWP have increased over the past decade. A comparison to National Center for Atmospheric Research Community Atmospheric Model Version 3.5 values finds modeled WVPs are slightly underestimated but the amplitude of the annual cycle is similar to that observed. Modeled winter LWPs slightly exceed those measured while the modeled summer LWPs exceed by a factor of two those observed (which are more likely to be positively biased also). The modeled rainrates are similar to retrieved values in the north Pacific, and exceed retrieved values by approximately a factor of 2 in the northeast Atlantic.

Zuidema, Paquita; Joyce, Robert

2008-03-01

261

Ionic liquid integrated multiwalled carbon nanotube in a poly(vinylidene fluoride) matrix: formation of a piezoelectric ?-polymorph with significant reinforcement and conductivity improvement.  

PubMed

Multiwalled carbon nanotubes (MWNTs) are functionalized covalently with ionic liquid (IL, 3-aminoethyl imidazolium bromide) which helps good dispersion of IL-functionalized MWNTs (MWNT-IL) in the poly(vinylidene fluoride) (PVDF) matrix. Analysis of transmission electron microscopy (TEM) micrographs suggests ?10 nm coating thickness of MWNTs by ILs, and the covalent linkage of ILs with MWNTs is confirmed from FT-IR and Raman spectra. PVDF nanocomposites with full ?-polymorphic (piezoelectric) form are prepared using MWNT-IL by both the solvent cast and melt-blending methods. The FE-SEM and TEM micrographs indicate that IL-bound MWNTs are homogeneously dispersed within the PVDF matrix. Increasing MWNT-IL concentration in the composites results in increased ? polymorph formation with a concomitant decrease of the ? polymorph, and a 100% ? polymorph formation occurs for 1 wt % MWNT-IL in both the fabrication conditions. A differential scanning calorimetry (DSC) study shows that the MWNT-ILs are an efficient nucleating agent for PVDF crystallization preferentially nucleating the ? form due to its dipolar interactions with PVDF. The glass transition temperature (T(g)) gradually increases with an increase in MWNT-IL concentration, and the storage modulus (G') of the composites increases significantly, showing a maximum increase of 101.3% for 0.5 wt % MWNT-IL. The Young's modulus increases with MWNT-IL concentration, and analysis of the data using the Halpin-Tsai equation suggests that at low concentration they adopt an orientation parallel to the film surface; however, at higher MWNT-IL concentration it is randomly oriented. The tensile strength also increases with an increase in MWNT-IL concentration, and both the Young's modulus and the tensile strength of solvent cast films are lower than melt-blended samples. The elongation at break in the solvent cast samples shows a maximum, but in melt-blended samples it decreases continuously with increasing MWNT-IL concentration. The composites exhibit a very low conductivity percolation threshold at 0.05 wt %, and the three-dimensional conducting network is produced. Higher conductivity (?1 S/cm for 1% MWNT-IL) than other MWNT/PVDF composites has been attributed to the anchored ionic liquid. PMID:23281687

Mandal, Amit; Nandi, Arun K

2013-02-01

262

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

NASA Technical Reports Server (NTRS)

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.

Prabhakara, C.; Short, D. A.

1984-01-01

263

Free energy surface of ST2 water near the liquid-liquid phase transition Peter H. Poole, Richard K. Bowles, Ivan Saika-Voivod, and Francesco Sciortino  

E-print Network

Free energy surface of ST2 water near the liquid-liquid phase transition Peter H. Poole, Richard K://jcp.aip.org/about/rights_and_permissions #12;THE JOURNAL OF CHEMICAL PHYSICS 138, 034505 (2013) Free energy surface of ST2 water near umbrella sampling Monte Carlo simulations to evaluate the free energy surface of the ST2 model of water

Sciortino, Francesco

264

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

NASA Technical Reports Server (NTRS)

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.

Yamauchi, S. T. (inventor)

1983-01-01

265

Water-saving liquid-gas conditioning system  

DOEpatents

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.

Martin, Christopher; Zhuang, Ye

2014-01-14

266

Experimental evidence of the ferroelectric phase transition near the $\\lambda-$point in liquid water  

E-print Network

We studied dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by the porous sizes \\sim 3-10nm. We report the direct measurements of the dielectric constant by the dielectric spectroscopy method at frequencies 25Hz-1MHz and demonstrate clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the \\lambda- point in the bulk supercooled water. The presented results support the previously developed polar liquid phenomenology and hence establish its applicability to model actual phenomena in liquid water.

Fedichev, P O; Bordonskiy, G S; Orlov, A O

2011-01-01

267

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

NASA Astrophysics Data System (ADS)

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 ? of methane in the liquid-vapor interface of water as well as ? 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 ? under two conditions: variation of ? at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of ? at fixed z depends on the position z and the system, whereas ? 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 ? 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 ?(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of ? grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of ? is due to the layering structure of the free interface of water.

Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

2014-11-01

268

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

PubMed

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 ? of methane in the liquid-vapor interface of water as well as ? 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 ? under two conditions: variation of ? at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of ? at fixed z depends on the position z and the system, whereas ? 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 ? 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 ?(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of ? grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of ? is due to the layering structure of the free interface of water. PMID:25399181

Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

2014-11-14

269

Determination of true octanol-water partition coefficients by means of solvent generated liquid-liquid chromatography  

Microsoft Academic Search

Compared to other methods for the determination of octanol-water partition coefficients chromatography offers a number of advantages: sample purification is unnecessary, the partition coefficients of the components of a mixture can be measured simultaneously and a minimum amount of sample is needed. In the past these determinations were almost exclusively carried out by liquid-solid chromatography (LSC) on alkyl bonded silica

M. Cichna; P. Markl; J. F. K. Huber

1995-01-01

270

Optimization of a dispersive liquid-liquid microextraction method for the analysis of benzotriazoles and benzothiazoles in water samples.  

PubMed

A simple and rapid dispersive liquid-liquid microextraction method has been developed for the determination of 11 benzotriazoles and benzothiazoles in water samples. Tri-n-butylphosphate (TBP) was used as extractant, thus avoiding the use of toxic water-immiscible chlorinated solvents. The influence of several variables (e.g., type and volume of dispersant and extraction solvents, sample pH, ionic strength, etc.) on the performance of the sample preparation step was systematically evaluated. Analytical determinations were carried out by high-performance liquid chromatography with fluorescence and UV detection and liquid chromatography-electrospray ionization-tandem mass spectrometry. The optimized method exhibited a good precision level with relative standard deviation values between 3.7% and 8.4%. Extraction yields ranging from 67% to 97% were obtained for all of these considered compounds. Finally, the proposed method was successfully applied to the analysis of benzotriazoles and benzothiazoles in real water samples (tap, river, industrial waters, and treated and raw wastewaters). PMID:22134495

Pena, Ma Teresa; Vecino-Bello, X; Casais, Ma Carmen; Mejuto, Ma Carmen; Cela, Rafael

2012-02-01

271

NATURAL RADIONUCLIDES MEASUREMENTS IN DRINKING WATER BY LIQUID SCINTILLATION COUNTING. METHODS AND RESULTS  

E-print Network

been used in this work. Some brands of bottled water were examined too, both for testing methodsNATURAL RADIONUCLIDES MEASUREMENTS IN DRINKING WATER BY LIQUID SCINTILLATION COUNTING. METHODS content in water intended for human consumption has been brought to public attention by the recent Council

272

Reference Correlations for Thermophysical Properties of Liquid Water Jaroslav Ptek, Jan Hrub,a...  

E-print Network

Reference Correlations for Thermophysical Properties of Liquid Water at 0.1 MPa Jaroslav Ptek, Jan Association for the Properties of Water and Steam IAPWS . The equations presented here are simple enough capacity; speed of sound; thermal conductivity; ther- modynamic properties; viscosity; water. CONTENTS 1

Magee, Joseph W.

273

Vacuum skimming apparatus for removing liquid contaminants floating in confined bodies of water  

Microsoft Academic Search

A boat-mounted vacuum system is described for removing floating liquid contaminants, such as oil spills, particularly from confined bodies of waters such as harbors, bays, and the like. The system employs one or more water jet eductors for creating a vacuum in a vacuum tank located between the suction heads and the pump supplying high pressure water to the eductors

D. M. Horne; W. H. Heyser; H. M. Neeley

1973-01-01

274

Macroemulsions of liquid and supercritical CO{sub 2}-in-water and water-in-liquid CO{sub 2} stabilized by fine particles  

SciTech Connect

Liquid and supercritical carbon dioxide-in-water (C/W) and water-in-carbon dioxide (W/C) macroemulsions (Pickering emulsions) stabilized by fine particles were created in a high-pressure batch reactor. C/W macroemulsions form when hydrophilic particles, such as pulverized limestone, sand, flyash, shale, and lizardite, a rock rich in magnesium silicate, are used as stabilizers; W/C macroemulsions form when hydrophobic particles, such as Teflon powder, activated carbon, carbon black, and pulverized coal, are used as stabilizers. C/W macroemulsions form with both liquid and supercritical CO{sub 2}, C/W macroemulsions consist of dispersed droplets of liquid or supercritical CO{sub 2} sheathed with particles in water; W/C macroemulsions consist of droplets of water sheathed with particles dispersed in liquid CO{sub 2}. The sheathed droplets are called globules. The globule diameter is largely dependent on the shear force imparted by mixing the two fluids, CO{sub 2} and H{sub 2O. The particle size needs to be adjusted to the dispersed droplet diameter; a practical ratio was found to be 1:20. In a batch reactor with a magnetic stir bar rotating at 1300 rpm, liquid CO{sub 2} produced typical globule diameters in the 200-300 mu m range, whereas supercritical CO{sub 2} produced smaller globules, in the 100-150 mu m range.

Golomb, D.; Barry, E.; Ryan, D.; Swett, P.; Duan, H. [University of Massachusetts Lowell, Lowell, MA (United States)

2006-04-12

275

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

SciTech Connect

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

Lundin, A. G., E-mail: arlund@mail.ru; Koryavko, N. A.; Chichikov, S. A. [Siberian State Technological University (Russian Federation)

2013-05-15

276

CFD MODELING OF GAS LIQUID FLOW AND HEAT TRANSFER IN A HIGH PRESSURE WATER ELECTROLYSIS SYSTEM  

Microsoft Academic Search

A high -pressure water electrolysis system has been investigated numerically and experimentally . The advanced CFD model of tw o-phase flow, which calculated the 3D distributions of pressure, gas and liquid velocities and gas and liquid volume fractions, has been developed to account for all the major components in the system, and appropriate constitutive equations for two -phase f low

V. Agranat; S. Zhubrin; A. Maria; J. Hinatsu; M. Stemp; M. Kawaji

277

Enthalpies of dissolution of ionic liquids in water-acetonitrile solutions at 298.15 K  

NASA Astrophysics Data System (ADS)

Enthalpies of dissolution of ionic liquids [C4mim]OTf, [C4mim]NTf2, and [C4mpy]NTf2 are measured in studying the thermodynamic characteristics of solvation and ion association for ionic liquids in nonaqueous and mixed solvents in acetonitrile-water of three compositions at 298.15 K. Standard enthalpies of solution are determined.

Belov, A. V.; Solov'ev, S. N.

2015-02-01

278

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

E-print Network

Park City/ANS 1 ANALYSIS OF LIQUID CRYOGEN-WATER EXPERIMENTS WITH THE MELCOR CODE R.C. Duckworth, J explosions have been of interest in industrial processes with molten metals, and postulated accident with industrial accidents involving molten metals, and with melt accidents in fission reactors. When hot liquid

California at Los Angeles, University of

279

Ultralow liquid/solid friction in carbon nanotubes: comprehensive theory for alcohols, alkanes, OMCTS, and water.  

PubMed

In this work, we perform a theoretical study of liquid flow in graphitic nanopores of different sizes and geometries. Molecular dynamics flow simulations of different liquids (water, decane, ethanol, and OMCTS) in carbon nanotubes (CNT) are shown to exhibit flow velocities 1-3 orders of magnitude higher than those predicted from the continuum hydrodynamics framework and the no-slip boundary condition. These results support previous experimental findings obtained by several groups that reported exceptionally high liquid flow rates in CNT membranes. The liquid/graphite friction coefficient is identified as the crucial parameter for this fast mass transport in CNT. The friction coefficient is found to be very sensitive to wall curvature: friction is independent of confinement for liquids between flat graphene walls with zero curvature, whereas it decreases with increasing positive curvature (liquid inside CNT), and it increases with increasing negative curvature (liquid outside CNT). Furthermore, we present a theoretical approximate expression for the friction coefficient, which predicts qualitatively and semiquantitatively its curvature dependent behavior. The proposed theoretical description, which works well for different kinds of liquids (alcohols, alkanes, and water), sheds light on the physical mechanisms at the origin of the ultra low liquid/solid friction in CNT. In fact, it is due to their perfectly ordered molecular structure and their atomically smooth surface that carbon nanotubes are quasiperfect liquid conductors compared to other membrane pores like nanochannels in amorphous silica. PMID:22974715

Falk, Kerstin; Sedlmeier, Felix; Joly, Laurent; Netz, Roland R; Bocquet, Lydric

2012-10-01

280

Chasing charge localization and chemical reactivity following photoionization in liquid water  

E-print Network

The ultrafast dynamics of the cationic hole formed in bulk liquid water following ionization is investigated by ab initio molecular dynamics simulations and an experimentally accessible signature is suggested that might ...

Marsalek, Ondrej; Elles, Christopher G.; Pieniazek, Piotr A.; Pluha?ová , Eva; VandeVondele, Joost; Bradforth, Stephen E.; Jungwirth, Pavel

2011-11-08

281

CYP1A1 and GSTM1 genetic polymorphisms in lung cancer populations exposed to arsenic in drinking water.  

PubMed

Region II of Chile is the most important copper mining area in the world and it shows the highest lung cancer mortality rate in the country (35/100,000). The population in Antofagasta, the main city of Region II, was exposed from 1958 to 1970 to 860 microg m(-3) arsenic (As) in drinking water and has currently been declining to 40 microg m(-3). Glutathione serves as a reducing agent and glutathione S-transferase (GST) may have an important role in As methylation capacity and body retention. In the current study, the null genotype of GSTM1 and the MspI polymorphism of CYP450 1A1 were investigated in lung cancer patients and in healthy volunteers of Region II. In males, the 2A genotype of MspI represented a highly significant estimated relative lung cancer risk (OR=2.60). Relative lung cancer risk for the combined 2A/null GSTM1 genotypes was 2.51, which increased with the smoking habit (OR=2.98). In Region II, the cancer mortality rate for As-associated cancers at least partly might be related to differences in As biotransformation. Genetic biomarkers such as 2A and GSTM1 polymorphisms in addition to DR70 as screening biomarkers might provide relevant information to identify individuals with a high risk for lung cancer as prevention and protection actions to protect public health. PMID:16012082

Adonis, M; Martnez, V; Marn, P; Gil, L

2005-05-01

282

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

PubMed

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

Lasarte-Aragons, Guillermo; Lucena, Rafael; Crdenas, Soledad; Valcrcel, Miguel

2015-03-01

283

Ab initio calculation of the electronic absorption spectrum of liquid water  

SciTech Connect

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 OH 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.

Martiniano, Hugo F. M. C.; Galamba, Nuno [Grupo de Fsica Matemtica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa (Portugal)] [Grupo de Fsica Matemtica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa (Portugal); Cabral, Benedito J. Costa, E-mail: ben@cii.fc.ul.pt [Grupo de Fsica Matemtica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa (Portugal) [Grupo de Fsica Matemtica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa (Portugal); Departamento de Qumica e Bioqumica, Faculdade de Cincias, Universidade de Lisboa, 1749-016 Lisboa (Portugal); Instituto de Fsica da Universidade de So Paulo, CP 66318, 05314-970 So Paulo, SP (Brazil)

2014-04-28

284

Pressure Evolution of the High-Frequency Sound Velocity in Liquid Water  

Microsoft Academic Search

The high-frequency sound velocity v? of liquid water has been determined to densities of 1.37 g\\/cm3 by inelastic x-ray scattering. In comparison to the hydrodynamic sound velocity v0, the increase of v? with density is substantially less pronounced, indicating that, at high density, the hydrogen-bond network is decreasingly relevant to the physical properties of liquid water. Furthermore, we observe an

M. Krisch; P. Loubeyre; G. Ruocco; F. Sette; A. Cunsolo; M. D'Astuto; R. Letoullec; M. Lorenzen; A. Mermet; G. Monaco; R. Verbeni

2002-01-01

285

Hydrogen peroxide and ozone formation in hybrid gas-liquid electrical discharge reactors [water treatment applications  

Microsoft Academic Search

Ozone and hydrogen peroxide were simultaneously formed in the gas and liquid phases of hybrid electrical discharge reactors, known as the hybrid-series and hybrid-parallel reactors, which utilize both gas phase nonthermal plasma formed above the water surface and direct liquid phase corona-like discharge in the water. In the series configuration the high voltage needle-point electrode is submerged and the ground

P. Lukes; A. T. Appleton; B. R. Locke

2002-01-01

286

Single- and dual-wavelength radar determination of liquid-water content in a Texas thunderstorm  

E-print Network

SINGLE- AND DUAL-WAVELENGTH RADAR DETERMINATION OF LIQUID-WATER CONTENT IN A TEXAS THUNDERSTORM A Thesis by CHARLES THEODORE LINN l Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE May 1976 Major Subject: Meteorology SINGLE-AND DUAL-WAVELENGTH RADAR DETERMINATION OF LIQUID-WATER CONTENT IN A TEXAS THUNDERSTORM A Thesis by CHARLES THEODORE LINN Approved as to style and content by: (Ch rman...

Linn, Charles Theodore

1976-01-01

287

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

DOEpatents

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.

Shepodd, Timothy J. (Livermore, CA)

2006-02-21

288

Aquarius - A Compact and Lightweight Ice and Liquid Water Isotope Analyzer  

NASA Astrophysics Data System (ADS)

We are developing Aquarius, a multipurpose ice and liquid water isotope analyzer. Aquarius combines a liquid-to-gas converter with a laser spectrometer to measure water isotopologue abundances with per mil accuracy. Its compact size will be ideal for field hydrology, while an optional interface with a thermal ice drill will enable in situ measurement of polar climate records. Upon completion, Aquarius will be used for extraterrestrial studies including identifying Mars" past climate cycles, tracing Martian water history, and measuring deuterium abundance in the primordial solar system as recorded in comet ice. Anticipated terrestrial applications include sampling aquifers to assess drinking water quality in developing countries.

Christensen, L. E.; Smith, M.; Chen, P.

2008-12-01

289

Nuclear tanker producing liquid fuels from air and water  

E-print Network

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

Galle-Bishop, John Michael

2011-01-01

290

Hydrothermal decomposition of liquid crystal in subcritical water.  

PubMed

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 275C and reaction time 5 min, 97.6% of 4-octoxy-4'-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment. PMID:24632487

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

2014-04-30

291

Intraspecific Diversity of Vibrio vulnificus in Galveston Bay Water and Oysters as Determined by Randomly Amplified Polymorphic DNA PCR  

PubMed Central

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. PMID:12788713

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

2003-01-01

292

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

PubMed

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. PMID:12788713

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

2003-06-01

293

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)

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.

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

1991-01-01

294

Excess entropy, Diffusivity and Structural Order in liquids with water-like anomalies  

E-print Network

The excess entropy, Se, defined as the difference between the entropies of the liquid and the ideal gas under identical density and temperature conditions, is shown to be the critical quantity connecting the structural, diffusional and density anomalies in water-like liquids. Based on simulations of silica and the two-scale ramp liquids, water-like density and diffusional anomalies can be seen as consequences of a characteristic non-monotonic density dependence of Se. The relationship between excess entropy, the order metrics and the structural anomaly can be understood using a pair correlation approximation to Se.

Ruchi Sharma; Somendra Nath Chakraborty; Charusita Chakravarty

2006-07-17

295

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

NASA Technical Reports Server (NTRS)

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.

Powell, Eugene A.

1988-01-01

296

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

USGS Publications Warehouse

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

Delaney, David F.; Maevsky, Anthony

1980-01-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

298

Interfacial effects on the band edges of functionalized si surfaces in liquid water.  

PubMed

By combining ab initio molecular dynamics simulations and many-body perturbation theory calculations of electronic energy levels, we determined the band edge positions of functionalized Si(111) surfaces in the presence of liquid water, with respect to vacuum and to water redox potentials. We considered surface terminations commonly used for Si photoelectrodes in water splitting experiments. We found that, when exposed to water, the semiconductor band edges were shifted by approximately 0.5 eV in the case of hydrophobic surfaces, irrespective of the termination. The effect of the liquid on band edge positions of hydrophilic surfaces was much more significant and determined by a complex combination of structural and electronic effects. These include structural rearrangements of the semiconductor surfaces in the presence of water, changes in the orientation of interfacial water molecules with respect to the bulk liquid, and charge transfer at the interfaces, between the solid and the liquid. Our results showed that the use of many-body perturbation theory is key to obtain results in agreement with experiments; they also showed that the use of simple computational schemes that neglect the detailed microscopic structure of the solid-liquid interface may lead to substantial errors in predicting the alignment between the solid band edges and water redox potentials. PMID:25402590

Pham, Tuan Anh; Lee, Donghwa; Schwegler, Eric; Galli, Giulia

2014-12-10

299

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04631a

Talyzin, Alexandr V.; Hausmaninger, Tomas; You, Shujie; Szab, Tams

2013-12-01

300

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

NASA Technical Reports Server (NTRS)

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.

Stoker, C.

2004-01-01

301

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

SciTech Connect

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.

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

2007-06-25

302

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

303

Identification of a low-frequency elastic behaviour in liquid water  

NASA Astrophysics Data System (ADS)

This article deals with the identification of solid-like properties measured at room temperature at a sub-millimetre length scale in liquid water. At a macroscopic scale, normal liquids (i.e. above melting temperature), and in particular water, are typically and empirically defined by the absence of shear elasticity, in contrast to solids or plastic fluids that require a stress threshold for flowing. A novel method optimizing the transmission of the shear stress to the sample enables a more complete probe of the mechanical response of liquids. It reveals that glass formers and viscous alkanes actually exhibit finite macroscopic shear elasticity away from any phase transition. This protocol is here applied for the first time to liquid water at room temperature, revealing, at the sub-millimetre scale, a low-frequency solid-like property.

Noirez, Laurence; Baroni, Patrick

2012-09-01

304

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

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 L 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 g L(-1) was obtained with a correlation coefficient of 0.997 for six calibration points. The limit of detection obtained was 0.2 g L(-1), which is lower than the threshold value established by the Environmental Protection Agency and European Union (i.e., 2 g L(-1) and 1 g L(-1), respectively). The repeatability of the proposed method was evaluated at two different spiking levels (3 and 10 g L(-1)) and a coefficient of variation of 13% was obtained in both cases. The performance of the proposed methodology was evaluated in real-world water samples including tap water, bottled water, river water and industrial wastewater. Relative recoveries between 95% and 108% were obtained. PMID:25640123

Fernndez, Elena; Vidal, Lorena; Martn-Yerga, Daniel; Blanco, Mara del Carmen; Canals, Antonio; Costa-Garca, Agustn

2015-04-01

305

Pulsed Barrier Discharge in Gas-Liquid Two-Phase Flow for Water Treatment  

Microsoft Academic Search

Summary form only given. Pulsed barrier discharge is generated in a gas-liquid two-phase flow for decomposing persistent substances in water. This new method is proposed to extend the interfacial area between the nonthermal plasma and the treat water for efficient decomposition of persistent materials. Acetic acid solution as a persistent substance is filled in a plasma reactor that consists of

K. Yasuoka; H. Katayama; S. Ishii

2007-01-01

306

Special Pair Dance and Partner Selection: Elementary Steps in Proton Transport in Liquid Water  

E-print Network

translation of the oxygen atoms. This explained its fast mobility. Yet the molecular mechanism behind functions reveal the details of the water structure surrounding the hydronium during the proton mobility, and the construction of hydrogen fuel cells.16 Its mobility in liquid water is at least 4.5 times larger than

Agmon, Noam

307

Theory for an order-driven disruption of the liquid state in water  

Microsoft Academic Search

Water is known to exhibit a number of peculiar physical properties because of the strong orientational dependence of the intermolecular hydrogen bonding interactions that dominate its liquid state. Recent full-atom simulations of water in a nanolayer between graphite plates submersed in an aqueous medium have raised the possibility of a new addition to this list of peculiarities: they show that

Jeremy L. England; Sanghyun Park; Vijay S. Pande

2008-01-01

308

Simulations of ice and liquid water over a range of temperatures using the fluctuating charge model  

Microsoft Academic Search

The temperature dependence of the thermodynamic and dynamical properties of liquid water using the polarizable fluctuating charge (FQ) model is presented. The properties of ice Ih, both for a perfect lattice with no thermal disorder and at a temperature of 273 K, are also presented. In contrast to nonpolarizable models, the FQ model has a density maximum of water near

Steven W. Rick

2001-01-01

309

Effect of compression on liquid water transport and microstructure of PEMFC gas diffusion layers  

Microsoft Academic Search

This work explores how the degradation of the gas diffusion layer (GDL) under compression contributes to the formation of preferential pathways for water transport. Fluorescence microscopy is used to provide ex situ visualization of liquid water transport through the GDL placed beneath an optically transparent clamping plate. Transient image data obtained with a CCD camera indicates that areas of compression

A. Bazylak; D. Sinton; Z.-S. Liu; N. Djilali

2007-01-01

310

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

E-print Network

Measurement of Liquid Water Accumulation in a PEMFC with Dead-Ended Anode Jason B. Siegel,a, *,z electrolyte membrane fuel cell PEMFC with a dead-ended anode is observed using neutron imaging, polymer electrolyte membrane fuel cells PEMFCs operate below the boil- ing point of water, causing excess

Stefanopoulou, Anna

311

A two-dimensional computational model of a PEMFC with liquid water transport  

Microsoft Academic Search

A comprehensive, steady-state, computational model of a proton exchange membrane fuel cell (PEMFC) derived from first principles is presented. The model is two-dimensional and includes the transport of liquid water within the porous electrodes as well as the transport of gaseous species, protons, energy, and water dissolved in the ion conducting polymer. Electrochemical kinetics are modeled with standard rate equations

N. P. Siegel; M. W. Ellis; D. J. Nelson; M. R. von Spakovsky

2004-01-01

312

Liquid Water Transport in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells  

Microsoft Academic Search

High-current-density performance of polymer electrolyte fuel cells ~PEFCs! is known to be limited by transport of reactants and products. In addition, at high current densities, excessive amount of water is generated and condenses, filling the pores of electrodes with liquid water, and hence limiting the reactant transport to active catalyst. This phenomenon known as ''flooding'' is an important limiting factor

Ugur Pasaogullari; C. Y. Wang

2004-01-01

313

Liquid Water Dynamics in a Model Polymer Electrolyte Fuel Cell Flow Channel  

E-print Network

Liquid Water Dynamics in a Model Polymer Electrolyte Fuel Cell Flow Channel by Chris Miller in a Model Polymer Electrolyte Fuel Cell Flow Channel by Chris Miller Bachelors of Engineering, University in a polymer electrolyte fuel cell is a critical issue in ensuring high cell performance. The water production

Victoria, University of

314

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

NASA Technical Reports Server (NTRS)

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.

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

315

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

PubMed

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 ?g L(-1) of molybdenum (VI)) in 10 mL water sample were 72.6, 1.43 ?g L(-1) and 2.8%, respectively. PMID:21092750

Gharehbaghi, Maysam; Shemirani, Farzaneh

2011-02-01

316

Dynamics of nanoparticle self-assembly into superhydrophobic liquid marbles during water condensation.  

PubMed

Nanoparticles adsorbed onto the surface of a drop can fully encapsulate the liquid, creating a robust and durable soft solid with superhydrophobic characteristics referred to as a liquid marble. Artificially created liquid marbles have been studied for about a decade but are already utilized in some hair and skin care products and have numerous other potential applications. These soft solids are usually formed in small quantity by depositing and rolling a drop of liquid on a layer of hydrophobic particles but can also be made in larger quantities in an industrial mixer. In this work, we demonstrate that microscale liquid marbles can also form through self-assembly during water condensation on a superhydrophobic surface covered with a loose layer of hydrophobic nanoparticles. Using in situ environmental scanning electron microscopy and optical microscopy, we study the dynamics of liquid marble formation and evaporation as well as their interaction with condensing water droplets. We demonstrate that the self-assembly of nanoparticle films into three-dimensional liquid marbles is driven by multiple coalescence events between partially covered droplets and is aided by surface flows causing rapid nanoparticle film redistribution. We also show that droplet and liquid marble coalescence can occur due to liquid-to-liquid contact or squeezing of the two objects into each other as a result of compressive forces from surrounding droplets and marbles. Irrelevant of the mechanism, coalescence of marbles and drops can cause their rapid movement across and rolling off the edge of the surface. We also demonstrate that the liquid marbles randomly moving across the surface can be captured and immobilized by hydrophilic surface patterns. PMID:22035295

Rykaczewski, Konrad; Chinn, Jeff; Walker, Marlon L; Scott, John Henry J; Chinn, Amy; Jones, Wanda

2011-12-27

317

Liquid water absorption and scattering effects in DOAS retrievals over oceans  

NASA Astrophysics Data System (ADS)

Spectral effects of liquid water are present in absorption (differential optical absorption spectroscopy - DOAS) measurements above the ocean and, if insufficiently removed, may interfere with trace gas absorptions, leading to wrong results. Currently available literature cross sections of liquid water absorption are provided in coarser resolution than DOAS applications require, and vibrational Raman scattering (VRS) is mostly not considered, or is compensated for using simulated pseudo cross sections from radiative transfer modeling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS (Multi-AXis differential optical absorption spectroscopy) measurements of light penetrating very clear natural waters were performed, achieving average underwater light paths of up to 50 m. From these measurements, the retrieval of a correction spectrum (H2Ocorr) is presented, compensating simultaneously for insufficiencies in the liquid water absorption cross section and broad-banded VRS structures. Small-banded structures caused by VRS were found to be very efficiently compensated for by the intensity offset correction included in the DOAS fit. No interference between the H2Ocorr spectrum and phytoplankton absorption was found. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality, and performed better than using a liquid water cross section in combination with a simulated VRS spectrum. The decrease in the residual root mean square (rms) of the DOAS fit depends on the measurement's contamination with liquid water structures, and ranges from ? 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ocorr spectrum was found to prevent misfits of NO2 slant columns, especially for very low NO2 scenarios, and thus increases the reliability of the fit. In test fits on OMI satellite data, the H2Ocorr spectrum was found selectively above ocean surfaces, where it decreases the rms by up to ? 11 %.

Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.

2014-12-01

318

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

E-print Network

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

Gugan, Rgis; Lefort, Ronan; Bziel, Wilfried; Guendouz, Mohammed; Noirez, Laurence; Henschel, Anke; Huber, Patrick; 10.1140/epje/i2007-10323-0

2011-01-01

319

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

NASA Astrophysics Data System (ADS)

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

Banerjee, Rupak

320

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

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 ?L 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 ?g/L to 500 ?g/L), low LODs (0.06 ?g/L to 0.08 ?g/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. PMID:22939140

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

2012-08-30

321

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

PubMed

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

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

2014-07-14

322

A pressure-induced phase-transition from liquid to solid in Water  

Microsoft Academic Search

In connection with recent isentropic experiments on water where a functionally graded impactor in a light-gas gun is used to systematically probe the high-pressure meltline for water, hydrodynamic simulations of water undergoing a pressure-induced phase transition into its ice phase are presented. From a well defined set of initial conditions, the liquid system is isentropically compressed into its solid phase,

Daniel Orlikowski

2005-01-01

323

Three types of liquid water in icy surfaces of celestial bodies  

Microsoft Academic Search

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:(i)undercooled interfacial water (due to freezing point depression by van der Waals forces and premelting),(ii)water in brines (due to freezing point depression in solutions), and(iii)sub-surface melt

D. Mhlmann

2011-01-01

324

Establishment of a method for Rn determination in water by low-level liquid scintillation counter.  

PubMed

A procedure for the determination of (222)Rn in environmental water samples using liquid scintillation counting (LSC) was performed. The (226)Ra content in the water was determined by gamma-ray spectroscopy. An application of this procedure to drinking water collected from a public drinking fountain in Vojvodina (Serbia) is presented, including calculations of the annual effective dose for ingestion and inhalation for adults. PMID:25071245

Todorovi?, Nataa; Jakoni?, Ivana; Nikolov, Jovana; Hansman, Jan; Veskovi?, Miroslav

2014-11-01

325

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

NASA Astrophysics Data System (ADS)

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

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

326

Long time fluctuation of liquid water: l/f spectrum of energy fluctuation in hydrogen bond network rearrangement dynamics  

E-print Network

Long time fluctuation of liquid water: l/f spectrum of energy fluctuation in hydrogen bond network of the potential energy fluctuation of liquid water is examined and found to yield so-called l/f frequency bond network. `,* This rearrangement dynamics involves collective motion of water molecules and energy

Ramaswamy, Ram

327

Water transport in water-in-oil-in-water liquid emulsion membrane system for the separation of lactic acid  

SciTech Connect

Liquid emulsion membranes (LEMs) were applied to the separation of lactic acid from an aqueous feed phase, and water transport (swelling) was investigated during the separation. Considering that as lactic acid was extracted into the internal stripping phase, osmotic pressure difference across the membrane was varied, the water transfer coefficient was evaluated. The water transfer coefficient was larger at higher carrier concentration and initial lactic acid concentration, which means that emulsion swelling can also be mediated by solute/carrier complexes although it is, in general, osmotically induced. The appropriate LEM formulation was given for separation and concentration of lactic acid. If both separation and concentration are desired, evidently emulsion swelling should be considered in conjunction with the transport rate of lactic acid. It was observed that the separated solute concentration in the internal phase was lowered due to swelling during the operation. Nevertheless, lactic acid could be concentrated in the internal phase more than 6 times in specific conditions, indicating that as the volume ratio of external phase to internal phase is increased, a still higher concentration in the internal phase can be obtained. 22 refs., 10 figs., 4 tabs.

Mok, Y.S.; Lee, W.K. (Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of))

1994-03-01

328

[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

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. PMID:25269261

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

2014-06-01

329

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

PubMed

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

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

2013-11-01

330

Distributed Reforming of Renewable Liquids via Water Splitting using  

E-print Network

-print area #12;BILIWG Meeting, Nov. 6, 2007 3 Reforming of Fuels via Water Splitting using OTM No electrical Splitting using OTM Oxygen is removed by membrane. Non-galvanic (no electrodes/ electrical circuitry) High p Spring Al2O3 Rod seal Al2O3 Tubes Agilent 6890 GC Column: molecular sieve 5A Detector: TCD Water Trap

331

QUATERNARY LIQUID EQULIBRIUM : WATERPHOSPHORIC ACID1 PENTANONE AT 25 C  

Microsoft Academic Search

Liquid-liquid equilibrium, solubility and tie-line data, for the quaternary system Water-Phosphoric Acid-l-Pentanol-3-Pentanone, were obtained at 25C and atmospheric pressure, using an analytical method. 1-Pentanol appears to be more effective than 3-Pentanone as extractant solvent of phosphoric acid. Advantages are not observed with the use of mixed solvents in the purification of wet process phosphoric acid by means of solvent extraction.

JOSE M. MARCO; MARIA L GALAN; JOSE COSTA

1988-01-01

332

Calculation of the X-ray absorption spectrum of liquid water and ice  

Microsoft Academic Search

We calculate the near-edge X-ray absorption fine structure (NEXAFS) spectrum of water in the gas liquid and solid (cubic) phases. We use density functional theory in the gas and solid phases and ab initio molecular dynamics to generate liquid phase configurations at a temperature of 300K. Subsequently, we calculate oscillator strengths between the 1s state of each oxygen atom and

Balazs Hetenyi; Paolo Giannozzi; Roberto Car

2001-01-01

333

Dialkylimidazolium ionic liquids as electrolytes for hydrogen production from water electrolysis  

Microsoft Academic Search

Imidazolium ionic liquids (ILs) such as BMIBF4 and BMIPF6 were studied by cyclic voltammetry (CV). BMIBF4 was used as an electrolyte for hydrogen production through water electrolysis. The system using this ionic liquid in a conventional electrochemical cell with platinum electrodes at room temperature and atmospheric pressure gives current densities (j) higher than 20mAcm?2 and efficiencies of more than 94.5%.

Roberto F. de Souza; Janine C. Padilha; Reinaldo S. Gonalves; Jolle Rault-Berthelot

2006-01-01

334

Ionic liquid-containing semipermeable membrane devices for monitoring the polycyclic aromatic hydrocarbons in water  

Microsoft Academic Search

Ionic liquid-containing semipermeable membrane devices (IL-SPMDs) were developed to monitor the polycyclic aromatic hydrocarbons in water. Uptake kinetics of naphthalene, 1-methylnaphthalene, phenanthrene, pyrene, chrysene by layflat low-density polyethylene tubing (15cm2cm) filled with 0.5ml 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid were studied in a laboratory continuous-flow system for the duration of 16 days. The device concentration factors were in the range of 8307800

Wenyan Zhao; Meng Han; Shugui Dai; Jian Xu; Ping Wang

2006-01-01

335

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

Microsoft Academic Search

Automated dynamic liquidliquidliquid 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

Jingming Wu; Kim Huey Ee; Hian Kee Lee

2005-01-01

336

The effect of polymorphism and magnesium substitution on oxygen isotope fractionation between calcium carbonate and water  

Microsoft Academic Search

Calcite, aragonite and magnesian calcite were slowly precipitated from aqueous bicarbonate solutions, and oxygen isotope fractionation factors between the precipitate and water were measured. For calcite-water at 25C and 0C, 1000 ln = 28.1 and 33.7, respectively, both values in excellent agreement with the Urey-Epstein paleotemperature scale. Aragonitewater at 25C gave 28.7, implying a small but significant fractionation between aragonite

Toshikazu Tarutani; Robert N. Clayton; Toshiko K. Mayeda

1969-01-01

337

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

SciTech Connect

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.

Brusseau, M.L.; Narter, M.; Schnaar, G.; Marble, J.; (Ariz)

2009-06-01

338

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

339

Comparison of the structure of harmonic aqueous glasses and liquid water  

NASA Technical Reports Server (NTRS)

Glassy structures of water were generated by rapidly quenching configurations of 64 and 343 molecules of liquid water; and the potential energy was then expanded through quadratic order around local minima generated in this way, and the properties of the resulting harmonic system were calculated. The results obtained were used to test the degree to which the structure of liquid water is similar to that of a harmonic aqueous glass. The radial distribution functions for the glass were found to be remarkably similar to those of the liquid. Translational modes were found to be almost entirely responsible for the broadening of the oxygen-oxygen radial distribution function of the quenched configuration, and also primarily responsible for the broadening of other radial distribution functions.

Pohorille, Andrew; Wilson, Michael A.; Pratt, Lawrence R.; Laviolette, Randall A.; Macelroy, Robert D.

1987-01-01

340

A liquid water management strategy for PEM fuel cell stacks  

E-print Network

for fuel cell stacks consisting of a few cells, can also be used to prevent non-uniform gas distribution [5]. In the serial configuration the gas from the outlet of the first cell is fed to the inlet of the second cell and so on until the last cell... rates, this method was insufficient. Since no other means was readily or economically available, a water displacement method was used. The stack exhaust was connected to a water bottle with an exit submerged in the water to allow the inflow of gas...

Van Nguyen, Trung; Knobbe, M. W.

2003-02-25

341

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

342

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

PubMed

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

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

2014-06-20

343

Dual Spectrum Neutron Radiography: Identification of Phase Transitions between Frozen and Liquid Water  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

344

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

PubMed

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: 1.110(-) (3)molL(-1); and ionic liquid: 50.0mg. Under the optimum conditions, the preconcentration factor obtained was 100. Calibration graph was linear in the range of 0.2-60gL(-1) with correlation coefficient of 0.9992. The limit of detection was 0.06gL(-) (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. PMID:22893353

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

2013-06-01

345

Experimental study on the interaction of fine water spray with liquid pool fires  

NASA Astrophysics Data System (ADS)

An experimental study of the interaction of a fine water spray with liquid pool fires was performed. Spatially resolved droplet size, velocity distributions, and volume flux of the fine water spray have been obtained in two types of pressure-atomized fine spray, using LDA/APV technology. A method to correct for the presence of droplets is presented and used to determine the heat release rate using a cone calorimeter system, the effects of water spray application on the heat release rate for liquid pool fires were studied. It was found that the volume flux of the water spray is an important factor to determine the liquid pool fire behavior. For the current experimental conditions, the flame was enlarged when lower volume flux of water is used, and suppressed significantly when larger volumes of water are used. Two opposing mechanisms compete when water sprays are applied, which is more complex than the halon agents, such as 1301. The combustion enhancement becomes insignificant when water sprays with the proper characteristics such as adequate volume flux are applied to the diffusion flame in a confined space.

Liao, Guangxuan; Liu, Jianghong; Qin, Jun; Yao, Bin

2001-10-01

346

Two-Phase Model of Liquid-Liquid Interactions With Interface Capturing: Application to Water Assisted  

E-print Network

Assisted Injection Molding Luisa Silva, Rodolphe Lanrivain, Walid Zerguine, Andres Rodriguez and pressure of each phase). Results are shown, for 2D and 3D parts. Keywords: Water Assisted Injection Molding, Finite element method, Two phase flow. PACS: INTRODUCTION Water Assisted Injection Molding (WAIM

Paris-Sud XI, Université de

347

Diffusivity in 2-butoxyethanol/water mixtures of noncritical composition approaching the liquid/liquid coexistence curve  

NASA Astrophysics Data System (ADS)

Results of dynamic light scattering experiments are reported which demonstrate that the mutual diffusion coefficient of 2-butoxyethanol/water mixtures of noncritical composition exhibits a characteristic temperature and composition dependence: The diffusion coefficients of the two phases of noncritical composition coexisting along the liquid/liquid coexistence curve decrease by an order of magnitude in the temperature range (Tp-Tc)<10 K approaching the lower critical point (Tp, temperature of phase separation; Tc, critical temperature). In the homogeneous 1-fluid phase region of the phase diagram, the D vs (T-Tp) curves of mixtures of noncritical composition are shifted to smaller values of D with decreasing values of ?y-yc? (y, mass fraction of 2-butoxyethanol; yc, critical mass fraction). These findings are discussed on the basis of the model of regular mixtures.

Schmitz, J.; Belkoura, L.; Woermann, D.

1994-07-01

348

Homogeneous Liquid-Liquid Extraction Coupled to Ion Mobility Spectrometry for the Determination of p-Toluidine in Water Samples.  

PubMed

In this research, homogeneous liquid-liquid extraction followed by ion mobility spectrometry (HLLE-IMS) with corona discharge ionization source has been developed for the determination of p-toluidine. The analyte was extracted by single-phase extraction in a ternary solvent system and then the extracted p-toluidine was injected into IMS for analysis. Optimization of different parameters which could influence HLLE-IMS was performed. Under optimum conditions, the dynamic linear range was obtained over 2.0-40.0ng/mL with R (2)=0.9966 while relative standard deviation was below 10%. The limits of detection and quantification were 0.6 and 2.0ng/mL of p-toluidine, respectively. The proposed method was applied to determine p-toluidine in environmental water samples which resulted in acceptable recoveries of the analyte, ranging from 85.3%-90%. PMID:25427773

Ashori, Amin; Sheibani, Ali

2015-04-01

349

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

NASA Technical Reports Server (NTRS)

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.

Clow, Gary D.

1987-01-01

350

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

SciTech Connect

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

Chiu, Janet; Giovambattista, Nicolas [Department of Physics, Brooklyn College of the City University of New York, Brooklyn, New York 11210 (United States)] [Department of Physics, Brooklyn College of the City University of New York, Brooklyn, New York 11210 (United States); Starr, Francis W. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States)] [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States)

2014-03-21

351

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

PubMed

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

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

2014-03-21

352

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

353

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

SciTech Connect

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.

Chao, K.C.

1990-01-01

354

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

NASA Astrophysics Data System (ADS)

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 Eyjafjallajkull eruptions. Laser diffraction particle size analysis of parent ash and aggregates is also used to calculate the first experimentally derived aggregation coefficients that account for changing liquid water contents and subzero temperatures. These indicate that dry conditions (<5-10 wt% liquid) promote strongly size selective collection of sub-63 ?m particles into aggregates (given by aggregation coefficients >1). In contrast, liquid-saturated conditions (>15-20 wt% liquid) promote less size selective processes. Crystalline ice was also capable of preferentially selecting volcanic ash <31 ?m under liquid-free conditions in a two-stage process of electrostatic attraction followed by ice sintering. However, this did not accumulate more than a monolayer of ash at the ice surface. These quantitative relationships may be used to predict the timescales and characteristics of aggregation, such as aggregate size spectra, densities, and constituent particle size characteristics, when the initial size distribution and water content of a volcanic cloud are known. The presence of an irregularly shaped, millimeter-scale vacuole at the center of natural aggregates was also replicated during interaction of ash and melting ice pellets, followed by sublimation. Fine-grained rims were formed by adding moist aggregates to a dry mixture of sub-31 ?m ash, which adhered by electrostatic forces and sparse liquid bridges. From this, we infer that the fine-grained outer layers of natural aggregates reflect recycled exposure of moist aggregates to regions of volcanic clouds that are relatively dry and dominated by <31 ?m ash.

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

2012-11-01

355

On the Existence and Stability of Liquid Water on the Surface of Mars Today  

NASA Astrophysics Data System (ADS)

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.

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

2002-06-01

356

Thrust Performance Improvement for a Water/Liquid Nitrogen Rocket Engine  

NASA Astrophysics Data System (ADS)

We propose a water/liquid nitrogen rocket engine as a new non-combustion type rocket engine. Liquid nitrogen is mixed with heated water and specific volume of nitrogen is increased by evaporation. Thrust force is obtained by exhaust of nitrogen gas through a nozzle with water particles. Results of previous experiments indicated a specific impulse is 60 % of the theoretically estimated value. By evaluating the characteristic exhaust velocity and other thrust characteristics, we found that the lower-than-expected specific impulse is due to insufficient propellant mixing and heat transfer between heated water and liquid nitrogen in the mixing chamber. We also performed high-speed imaging experiments to visualize impinging and mixing of propellants. Results indicate that in the original injection setup, heat conveyed by heated water is not adequately transferred to the liquid nitrogen. An alternative injection pattern was tested, which resulted in a 10% increase in the characteristic exhaust velocity. In addition, we tested a new type of injector designed for more efficient mixing and heat transfer that exhibited 30 % increase in characteristic exhaust velocity. Furthermore, we modified the theoretical expression for the characteristic exhaust velocity based on multi-phased flow theory so that it agrees well with the experimental results.

Watanabe, Rikio; Mikami, Ryo

357

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

358

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

PubMed

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. PMID:22356595

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

2012-03-27

359

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

360

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

PubMed

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. PMID:24974245

Martn, Victoria Isabel; Rodrguez, Amalia; Laschewsky, Andr; Moy, Mara Luisa

2014-09-15

361

The molecular charge distribution, the hydration shell, and the unique properties of liquid water  

NASA Astrophysics Data System (ADS)

The most essential features of a water molecule that give rise to its unique properties are examined using computer simulations of different water models. The charge distribution of a water molecule characterized by molecular multipoles is quantitatively linked to the liquid properties of water via order parameters for the degree (S2) and symmetry (?S2) of the tetrahedral arrangement of the nearest neighbors, or "hydration shell." ?S2 also appears to determine the long-range tetrahedral network and interfacial structure. From the correlations, some models are shown to be unable to reproduce certain properties due to the limitations of the model itself rather than the parameterization, which indicates that they are lacking essential molecular features. Moreover, since these properties depend not only on S2 but also on ?S2, the long-range structure in these models may be incorrect. Based on the molecular features found in the models that are best able to reproduce liquid properties, the most essential features of a water molecule in liquid water appear to be a charge distribution with a large dipole, a large quadrupole, and negative charge out of the molecular plane, as well as a symmetrically ordered tetrahedral hydration shell that results from this charge distribution. The implications for modeling water are also discussed.

Tan, Ming-Liang; Cendagorta, Joseph R.; Ichiye, Toshiko

2014-12-01

362

Determination of estrogenic mycotoxins in environmental water samples by low-toxicity dispersive liquid-liquid microextraction and liquid chromatography-tandem mass spectrometry.  

PubMed

A novel, simple, rapid and eco-friendly method based on dispersive liquid-liquid microextraction using a bromosolvent was developed to determine six estrogenic mycotoxins (zearalenone, zearalanone, ?-zearalanol, ?-zearalanol, ?-zearalenol and ?-zearalenol) in water samples by liquid chromatography-electrospray ionization tandem mass spectrometry in the negative mode (LC-ESI-MS/MS). The optimal conditions for this method include the use of 100?L bromocyclohexane as an extraction solvent (using a non-dispersion solvent), 10mL of aqueous sample (adjusted to pH 4), a vortex extraction time of 2min, centrifugation for 10min at 3500rpm and no ionic strength adjustment. The calibration function was linear and was verified by applying the Mandel fitting test with a 95% confidence level. No matrix effect was observed. According to the relative standard deviations (RSDs), the precision was better than 13% for the repeatability and intermediate precision. The average recoveries of the spiked compounds ranged from 81 to 118%. The method limits of detection (LOD) and quantification (LOQ) considering a 125-fold pre-concentration step were 4-20 and 8-40ngL(-1), respectively. Next, the method was applied to the analysis of the environmental aqueous samples, demonstrating the presence of ?-zearalanol and zearalanone in the river water samples. PMID:25770896

Emdio, Elissandro Soares; da Silva, Claudia Pereira; de Marchi, Mary Rosa Rodrigues

2015-04-24

363

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

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??g/L. The detection limits varied from 0.21 to 0.45??g/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. PMID:21077128

Zhou, Qingxiang; Zhang, Xiaoguo

2010-12-01

364

Comment on ``Structure and dynamics of liquid water on rutile TiO2(110)''  

NASA Astrophysics Data System (ADS)

Liu and co-workers [Phys. Rev. B1098-012110.1103/PhysRevB.82.161415 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 published work, 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.

Wesolowski, David J.; Sofo, Jorge O.; Bandura, Andrei V.; Zhang, Zhan; Mamontov, Eugene; P?edota, Milan; Kumar, Nitin; Kubicki, James D.; Kent, Paul R. C.; Vlcek, Lukas; Machesky, Michael L.; Fenter, Paul A.; Cummings, Peter T.; Anovitz, Lawrence M.; Skelton, Adam A.; Rosenqvist, Jrgen

2012-04-01

365

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

SciTech Connect

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.

Wesolowski, David J [ORNL; Sofo, Jorge O. [Pennsylvania State University; Bandura, Andrei V. [St. Petersburg State University, St. Petersburg, Russia; Zhang, Zhan [Argonne National Laboratory (ANL); Mamontov, Eugene [ORNL; Predota, M. [University of South Bohemia, Czech Republic; Kumar, Nitin [ORNL; Kubicki, James D. [Pennsylvania State University; Kent, Paul R [ORNL; Vlcek, Lukas [ORNL; Machesky, Michael L. [Illinois State Water Survey, Champaign, IL; Fenter, Paul [Argonne National Laboratory (ANL); Cummings, Peter T [ORNL; Anovitz, Lawrence {Larry} M [ORNL; Skelton, A A [Vanderbilt University; Rosenqvist, Jorgen K [ORNL

2012-01-01

366

Experimental determination of cavitation thresholds in liquid water and mercury  

SciTech Connect

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.

Taleyarkhan, R.P.; West, C.D. [Oak Ridge National Lab., TN (United States); Moraga, F. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1998-11-01

367

Reversed-phase high-performance liquid chromatography of sulfur mustard in water  

SciTech Connect

A reversed-phase high-performance liquid chromatography method for the detection and quantitation of sulfur mustard (HD) in water is described with detection at 200 nm. The detection based on the solubility of HD in water revealed that extremely low quantities of HD (4 to 5 mg/L) only are soluble. Experience shows that water is still the medium of choice for the analysis of HD in water and aqueous effluents in spite of the minor handicap of its half-life of ca. 4 minutes, which only calls for speedy analysis.

Raghuveeran, C.D.; Malhotra, R.C.; Dangi, R.S. (Defence Research and Development Establishment, Gwalior (India))

1993-01-01

368

Kinematical relations among radar-observed water concentrations, vertical motions, and liquid-water drop-size spectra in convective clouds  

E-print Network

KINEMATICAL RELATIONS AMONG RADAR-OBSERVED WATER CONCENTRATIONSp VERTICAL MOTIONS, AND LIQUID- WATER DROP-SIZE SPECTRA IN CONVECTIVE CLOUDS A Thesis By ROBERT CLAYTON RUNNELS Submitted to the Graduate School of the Agricultural and Mechanical... College of Texas in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1962 Major Subject: METEOROLOGY KINEMATICAL RELATIONS AMONG RADAR-OBSERVED WATER CONCENTRATIONS' VERTICAL MOTIONS p AND LIQUID WATER DROP" SIZE...

Runnels, Robert Clayton

1962-01-01

369

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

USGS Publications Warehouse

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.

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

1990-01-01

370

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

NASA Astrophysics Data System (ADS)

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.

Willard, Adam P.; Chandler, David

2014-11-01

371

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

PubMed

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. PMID:25399184

Willard, Adam P; Chandler, David

2014-11-14

372

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

373

Application of liquid-phase microextraction for the determination of phoxim in water samples by high performance liquid chromatography with diode array detector  

Microsoft Academic Search

A new method, which involves liquid-phase microextraction (LPME) followed by high performance liquid chromatography (HPLC) with diode array detector (DAD), was developed to determine phoxim in water sample. Experimental parameters affecting the extraction efficiency, such as extraction solvent, solvent volume, agitation speed of the sample and extraction time were investigated. Under the optimal extraction conditions, phoxim was found to yield

Pei Liang; Li Guo; Yan Liu; Shi Liu; Tao-zhi Zhang

2005-01-01

374

EVALUATION OF A TEFLON HELIX LIQUID-LIQUID EXTRACTOR FOR CONCENTRATION OF TRACE ORGANICS FROM WATER INTO METHYLENE CHLORIDE (JOURNAL VERSION)  

EPA Science Inventory

A continuous liquid-liquid extraction system (CLLE) for concentrating trace organics from water into methylene chloride for analysis was designed, built and evaluated. The CLLE uses Teflon coils for phase contact and gravity phase separation. The system includes a self-contained ...

375

Nuclear quantum effects in liquid water from path-integral simulations using anab initioforce-matching approach  

NASA Astrophysics Data System (ADS)

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

Spura, Thomas; John, Christopher; Habershon, Scott; Khne, Thomas D.

2015-04-01

376

Two exchange-correlation functionals compared for first-principles liquid water  

E-print Network

The first-principles description of liquid water using ab initio molecular dynamics (AIMD) based on Density Functional theory (DFT) has recently been found to require long equilibration times, giving too low diffusivities and a clear over-structuring of the liquid. In the light of these findings we compare here the room-temperature description offered by two different exchange correlation functionals: BLYP, the most popular for liquid water so far, and RPBE, a revision of the widely used PBE. We find for RPBE a less structured liquid with radial distribution functions closer to the experimental ones than the ones of BLYP. The diffusivity obtained with RPBE for heavy water is still 20% lower than the corresponding experimental value, but it represents a substantial improvement on the BLYP value, one order of magnitude lower than experiment. These characteristics and the hydrogen-bond (HB) network imperfection point to an effective temperature ~3% lower than the actual simulation temperature for the RPBE liquid, as compared with BLYP's ~17% deviation. The too long O--O average nearest-neighbor distance observed points to an excessively weak HB, possibly compensating more fundamental errors in the DFT description.

M. V. Fernandez-Serra; G. Ferlat; Emilio Artacho

2005-07-13

377

The supramolecular structure of liquid water and quantum coherent processes in biology  

NASA Astrophysics Data System (ADS)

Vibrational spectroscopy provides a powerful tool to understand the molecular structures. When applied to the liquid water, this technique reveals so many details which can also shed a light on the supramolecular arrangement of the most ubiquitous of the substances. In particular, the two fluid model of water, proposed several decades ago, founds experimental evidence. Moreover, some fundamental parameters calculated in the realm of the theory of Quantum ElectroDynamics applied to liquid water can be actually measured showing an excellent agreement with the theory. This allows to add a dynamical origin to the mixed cluster model of water well known by the biologists for fifty years and opens the way to the dawn of a real quantum biology.

De Ninno, A.; Congiu Castellano, A.; Del Giudice, E.

2013-06-01

378

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)

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.

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

379

Interaction of a Long Alkyl Chain Protic Ionic Liquid and Water  

E-print Network

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

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

2014-01-01

380

Molybdenum electrodes for hydrogen production by water electrolysis using ionic liquid electrolytes  

Microsoft Academic Search

The hydrogen production by water electrolysis was tested with different electrocatalysts (molybdenum, nickel, iron alloys containing chromium, manganese and nickel) using aqueous solutions of ionic liquid (IL) like 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4). The hydrogen evolution reaction (HER) was performed at room temperature in a potential of ?1.7V (PtQRE). A Hoffman cell apparatus was used to water electrolysis with current density values,

Roberto F. de Souza; Gabriel Loget; Janine C. Padilha; Emilse M. A. Martini; Michele O. de Souza

2008-01-01

381

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

USGS Publications Warehouse

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.

Goerlitz, D.F.

1981-01-01

382

A normal coordinate analysis based on the local structure of liquid water  

Microsoft Academic Search

Recent far-infrared, Raman, hyper-Raman, and inelastic neutron scattering measurements in the frequency range of about 100 to 1000 cm-1 have provided data related to the intermolecular motions of liquid water. A normal coordinate analysis of a simple mathematical model is used to study the motions of a rigid water molecule hydrogen bonded to its four nearest neighbors. The potential energy

Jon B. Bryan; Basil Curnutte

1972-01-01

383

Inactivation of algae in ballast water with multi-needle gas-liquid hybrid discharge reactor  

Microsoft Academic Search

Pulsed high-voltage discharge is a new advanced oxidation water treatment technology. Plasma technology has recently become significant because it offers the advantages of lower costs, higher treatment and energy efficiencies, and the smaller space volume it occupies. The present work investigates the use of a multi-needle plate reactor with gas-liquid hybrid discharge system to sterilize ballast water. The optimal sterilization

Nyein Nyein Aye; Sun Bing; Xiaomei Zhu; Zhiying Gao; Masayuki Sato

2010-01-01

384

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

385

Effect of the cation on the interactions between alkyl methyl imidazolium chloride ionic liquids and water.  

PubMed

A systematic study of the interactions between water and alkyl methyl imidazolium chloride ionic liquids at 298.2 K, based on activity coefficients estimated from water activity measurements in the entire solubility range, is presented. The results show that the activity coefficients of water in the studied ILs are controlled by the hydrophilicity of the cation and the cation-anion interaction. To achieve a deeper understanding on the interactions between water and the ILs, COSMO-RS and FTIR spectroscopy were also applied. COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies, suggesting the formation of complexes between three molecules of water and one IL molecule. On the basis of quantum-chemical calculations, it is found that cation-anion interaction plays an important role upon the ability of the IL anion to interact with water. The changes in the peak positions/band areas of OH vibrational modes of water as a function of IL concentration were investigated, and the impact of the cation on the hydrogen-bonding network of water is identified and discussed. PMID:25120073

Khan, Imran; Taha, Mohamed; Ribeiro-Claro, Paulo; Pinho, Simo P; Coutinho, Joo A P

2014-09-01

386

Parallel gastric emptying of nonhydrolyzable fat and water after a solid-liquid meal in humans.  

PubMed

Our aim was to examine the control of gastric emptying of the oil phase of a mixed solid and liquid meal. Previous studies had shown that liquid dietary fats normally leave the stomach at a slower rate than does water. We wished to determine whether the slower emptying of fats was due to the physical characteristics of food (lower density and greater viscosity than water), to retardation by duodenal feedback mechanisms, or whether both factors contributed. Thus, we quantified the emptying rates of water and sucrose polyester (a nonabsorbable analog of dietary fat) ingested by healthy volunteers as a mixed solid and liquid meal. Gastric emptying was quantified by an intubation-perfusion method incorporating an occlusive jejunal balloon to facilitate recovery. Four phase-specific, nonabsorbable markers were used. [14C[Sucrose octaoleate and polyethylene glycol were incorporated in the meal and traced the lipid and water phases, respectively; [3H]glycerol triether and phenolsulfonphthalein were used as duodenal recovery markers. Sucrose polyester (substituting for dietary fat) was emptied very rapidly, and at about the same rate as was water, in contrast to natural fat, which empties very slowly. Emptying of water was rapid and comparable to that observed after mixed meals containing natural fat. These results imply that gastric emptying of the oil phase is controlled by receptors sensitive to the hydrolytic products of fat digestion and that the slow emptying of dietary fat is not simply due to its lower density. PMID:7060909

Cortot, A; Phillips, S F; Malagelada, J R

1982-05-01

387

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

E-print Network

The time-resolved optical Kerr effect spectroscopy (OKE) is a powerful experimental tool enabling accurate investigations of the dynamic phenomena in molecular liquids. We introduced innovative experimental and fitting procedures, that permit a safe deconvolution of sample response function from the instrumental function. This is a critical issue in order to measure the dynamics of sample presenting weak signal, e.g. liquid water. We report OKE data on water measuring intermolecular vibrations and the structural relaxation processes in an extended temperature range, inclusive of the supercooled states. The unpreceded data quality makes possible a solid comparison with few theoretical models; the multi-mode Brownian oscillator model, the Kubo's discrete random jump model and the schematic mode-coupling model. All these models produce reasonable good fits of the OKE data of stable liquid water, i.e. over the freezing point. The features of water dynamics in the OKE data becomes unambiguous only at lower temperatures, i.e. for water in the metastable supercooled phase. Hence this data enable a valid comparison between the model fits. We found that the schematic mode-coupling model provides the more rigorous and complete model for water dynamics, even if is intrinsic hydrodynamic approach hide the molecular information.

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

2014-06-20

388

A GC-TCD method for measuring the liquid water mass of collected aerosols  

Microsoft Academic Search

This work presents a gas chromatographic method that uses a thermal conductivity detector (GC-TCD) to measure the liquid water mass (LWM) of collected aerosols. The method is a modification of the previously developed EA-TCD method (Journal of Aerosol Science 29, 827). A microcomputer was incorporated into the system to control the analytical procedures, improve the measurement precision, and make possible

Chung-Te Lee; Shih-Yu Chang

2002-01-01

389

Water-Solvent Liquid Junction Potential for some Low-Dielectric Solvents  

Microsoft Academic Search

The redox potentials for the cobalticenium \\/ cobaltocene couple in some low-dielectric solvents perspective as media for electroorganic syntheses and other applications, namely in monoglyme, dichlormetane and diglyme, have been determined. On this basis, the water - solvent liquid junction potentials are evaluated. This opens the possibility to compare the potentials of any electrochemical reaction in these solvents. The data

L. V. Bunakova; L. A. Khanova; V. V. Topolev; L. I. Krishtalik

390

Influence of chloride, water, and organic solvents on the physical properties of ionic liquids  

Microsoft Academic Search

We report here the first systematic study of the effect of impurities and additives (e.g., water, chloride, and cosolvents) on the physical properties of room-temperature ionic liquids. Remarkably, it was discovered that the viscosity of mixtures was dependent mainly on the mole fraction of added molecular solvents and only to a lesser extent upon their iden- tity, allowing viscosity changes

Kenneth R. Seddon; Annegret Stark; Mara-Jos Torres

2000-01-01

391

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

392

Exploring water and other liquids at negative pressure Frdric Caupin1,2  

E-print Network

Exploring water and other liquids at negative pressure Frédéric Caupin1,2 , Arnaud Arvengas1 been hitherto less studied: the region where the pressure is negative. Here we review the work with a description of the ongoing work in our groups. 1. Introduction to metastability and negative pressures 1

Paris-Sud XI, Université de

393

Liquid water in small solar system bodies, and the possibilities for evolution of life  

Microsoft Academic Search

Much attention has been focused on the few large satellites of Jupiter and Saturn that have evidence of interior layers of liquid water, and the possibility that they may be suitable habitats for life. For life to evolve in these regions, they would have to, at a minimum, produce the necessary chemical constituents to provide energy for building organic matter,

D. W. Sparks; M. M. Tice; L. Farrell; R. S. McGary

2008-01-01

394

Australian Winter Storms Experiment (AWSE) I: Supercooled Liquid Water and Precipitation-Enhancement Opportunities  

Microsoft Academic Search

Some results of the first (1988) Australian Winter Storms Experiment are described. The results shed light on precipitation-enhancement opportunities in winter cyclonic storms interacting with the Great Dividing Range of southeast Australia. The results come from analysis of supercooled liquid water amounts provided by a dual-wavelength microwave radiometer, atmospheric structure from Omegasondes, and precipitation amounts from a large number of

Alexis B. Long; Arlen W. Huggins

1992-01-01

395

Pore-Level Liquid Water Transport Through Composite Diffusion Media of PEMFC  

E-print Network

Pore-Level Liquid Water Transport Through Composite Diffusion Media of PEMFC Yan Ji, Gang Luo exchange membrane fuel cell PEMFC , has been simulated for the first time by a topologically equivalent. Published September 30, 2010. Proton exchange membrane fuel cells PEMFCs hold promise as a next generation

396

Numerical modeling of liquid water motion in a polymer electrolyte fuel cell  

E-print Network

Numerical modeling of liquid water motion in a polymer electrolyte fuel cell Fangming Jiang a October 2013 Accepted 20 October 2013 Available online 22 November 2013 Keywords: Polymer electrolyte fuel by Elsevier Ltd. All rights reserved. 1. Introduction Two-phase flow is ubiquitous in polymer electrolyte fuel

397

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

SciTech Connect

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

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

2000-11-01

398

Aromatic-aromatic interactions: Free energy profiles for the benzene dimer in water, chloroform, and liquid benzene  

Microsoft Academic Search

An all-atom model for benzene is reported and tested largely in Monte Carlo simulations of pure liquid benzene, benzene in dilute aqueous solution, and the benzene dimer in water and chloroform. Free energy profiles were obtained for the association of the benzene dimer in liquid benzene, water, and chloroform that characterize the energetics for this prototypical interaction between arenes in

William L. Jorgensen; Daniel L. Severance

1990-01-01

399

Pulse radiolysis of liquid water using picosecond electron pulses produced by a table-top terawatt laser system  

E-print Network

Pulse radiolysis of liquid water using picosecond electron pulses produced by a table-top terawatt into a supersonic helium gas jet are used to ionize liquid water. The decay of the hydrated electrons produced interaction of en- ergetic radiation with condensed matter are radical cations and ejected electrons

Umstadter, Donald

400

A new retrieval for cloud liquid water path using a ground-based microwave radiometer and measurements of cloud temperature  

Microsoft Academic Search

A new method to retrieve cloud liquid water path using 23.8 and 31.4 GHz microwave radiometer brightness temperature measurements is developed. This method does not depend on climatological estimates of either the mean radiating temperature of the atmosphere Tmr or the mean cloud liquid water temperature Tcloud. Rather, Tmr is estimated from surface temperature and relative humidity measurements, while Tcloud

James C. Liljegren; Eugene E. Clothiaux; Gerald G. Mace; Seiji Kato; Xiquan Dong

2001-01-01

401

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

PubMed

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 ?g L(-1), 3.7-10.3% (RSD, n=3) and 50-1000 ?g 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. PMID:23327945

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

2013-01-31

402

Development of a dispersive liquid-liquid microextraction method for iron speciation and determination in different water samples.  

PubMed

A novel, simple and efficient method for the iron (Fe) speciation and determination in different water samples was developed using dispersive liquid-liquid microextraction (DLLME) technique followed by spectrophotometric analysis. The procedure is based on complexation of Fe(II) with O-phenanthroline (O-Phen), the subsequent ion-association formation with picrate anion, then extraction of the complex using DLLME technique. Some important parameters such as the type and volume of extraction and dispersive solvents as well as the extraction time were investigated and optimized in detail. Under the optimum conditions, the calibration graphs were linear over the range of 0.025-1.0 ?g mL(-1) with limit of detection of 7.5 ?g L(-1). Relative standard deviation for five replicate determinations of Fe at 0.2 ?g mL(-1) concentration level was calculated to be 1.2%. Average recoveries for spiked samples were determined to be between 90% and 108%. The method was applied to water samples and parenteral solutions and the amounts of Fe found in these samples using the proposed method were similar with those obtained by a standard method. PMID:20797818

Tabrizi, Ahad Bavili

2010-11-15

403

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

PubMed

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

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

2014-05-28

404

Mars Gully: No Mineral Trace of Liquid Water  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2007-01-01

405

Scattering of water from the glycerol liquid-vacuum interface  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

406

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)

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

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

2013-06-01

407

Simultaneous diode-laser-based in situ measurement of liquid water content and oxygen mole fraction in dense water mist environments.  

PubMed

We performed what we believe are the first simultaneous in situ measurements of liquid water and oxygen concentrations in a dense water mist environment. Direct absorption tunable diode laser absorption spectroscopy was used to make oxygen concentrations and simultaneously quantify the liquid water via optical density measurements. This spectrometer with an absorption path length of only 36.8 cm was successfully tested during full-scale fire suppression tests with scattering losses up to 99.9%. The simultaneous oxygen and liquid water concentration measurements agree with fire suppression model calculations. PMID:16599205

Awtry, Andrew R; Fleming, James W; Ebert, Volker

2006-04-01

408

Simultaneous diode-laser-based in situ measurement of liquid water content and oxygen mole fraction in dense water mist environments  

NASA Astrophysics Data System (ADS)

We performed what we believe are the first simultaneous in situ measurements of liquid water and oxygen concentrations in a dense water mist environment. Direct absorption tunable diode laser absorption spectroscopy was used to make oxygen concentrations and simultaneously quantify the liquid water via optical density measurements. This spectrometer with an absorption path length of only 36.8 cm was successfully tested during full-scale fire suppression tests with scattering losses up to 99.9%. The simultaneous oxygen and liquid water concentration measurements agree with fire suppression model calculations.

Awtry, Andrew R.; Fleming, James W.; Ebert, Volker

2006-04-01

409

Artificial photosynthesis at liquid | liquid interfaces: photoreduction of benzoquinone by water soluble porphyrin species  

Microsoft Academic Search

The heterogeneous photoreduction of benzoquinone by hydrophilic porphyrin species was studied at a polarised water|1,2-dichloroethane interface. The dynamics of photoinduced electron injection and back charge transfer processes were analysed by periodic onoff light intensity perturbation and intensity modulated photocurrent spectroscopy (IMPS). The flux of electron injection increased and the phenomenological rate constant of back charge transfer decreased upon addition of

Riikka Lahtinen; David J. Ferm??n; Kysti Kontturi; Hubert H. Girault

2000-01-01

410

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

SciTech Connect

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.

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

2010-05-01

411

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)

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

Chen, Sow-Hsin; Baglioni, Piero

2012-02-01

412

Quantum effects in light and heavy liquid water: A rigid-body centroid molecular dynamics study.  

PubMed

The centroid molecular dynamics (CMD) method is applied to the study of liquid water in the context of the rigid-body approximation. This rigid-body CMD technique, which is significantly more efficient than the standard CMD method, is implemented on the TIP4P model for water and used to examine isotopic effects in the equilibrium and dynamical properties of liquid H(2)O and D(2)O. The results obtained with this approach compare remarkably well with those determined previously with path integrals simulations as well as those obtained from the standard CMD method employing flexible models. In addition, an examination of the impact of quantization on the rotational and librational motion of the water molecule is also reported. PMID:15367027

Hernndez de la Pea, L; Kusalik, P G

2004-09-22

413

Molecular Density Functional Theory for water with liquid-gas coexistence and correct pressure  

E-print Network

The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. With this correction, molecular density functional theory gives, at a modest computational cost, quantita...

Jeanmairet, Guillaume; Sergiievskyi, Volodymyr; Borgis, Daniel

2015-01-01

414

Determination of liquid water content and dielectric constant in porous media by the capacitive method  

NASA Astrophysics Data System (ADS)

A capacitive sensor-based apparatus has been settled to determine the liquid water amount and dielectric constant in consolidated porous media. This technique relies on the dielectric properties of water, air, and mineral substrate. The experimental procedure is described for successively oven-dried samples at 323 K. It allows us to determine the sample dielectric constant as a function of the sample water amount. For limestones from Caen region, an affine relationship is found at 293 K. This is then compared with other empirical soils data and with existing homogeneisation techniques applied to undeformable heterogeneous dielectrics. To cite this article: T. Fen-Chong et al., C. R. Mecanique 332 (2004).

Fen-Chong, Teddy; Fabbri, Antonin; Guilbaud, Jean-Pierre; Coussy, Olivier

2004-08-01

415

Hydrogen bonding and molecular orientation at the liquid-vapour interface of water.  

PubMed

We determine the molecular structure and orientation at the liquid-vapour interface of water using an electronically coarse grained model constructed to include all long-range electronic responses within Gaussian statistics. The model, fit to the properties of the isolated monomer and dimer, is sufficiently responsive to generate the temperature dependence of the surface tension from ambient conditions to the critical point. Acceptor hydrogen bonds are shown to be preferentially truncated at the free surface under ambient conditions and a related asymmetry in hydrogen bonding preference is identified in bulk water. We speculate that this bonding asymmetry in bulk water is the microscopic origin of the observed surface structure. PMID:25715668

Cipcigan, Flaviu S; Sokhan, Vlad P; Jones, Andrew P; Crain, Jason; Martyna, Glenn J

2015-04-14

416

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

NASA Technical Reports Server (NTRS)

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.

Wilson, Michael A.; Pohorille, Andrew

1991-01-01

417

Its Just a Phase: Water as a Solid, Liquid, and Gas  

NSDL National Science Digital Library

In this lesson, students will construct models of the way water molecules arrange themselves in the three physical states. They will come to understand that matter can be found in three forms or phases (solid, liquid, and gas). Using physical models, students will be able to explain the molecular behavior of ice, water, and water vapor. The instructor guide contains detailed background material, learning goals, alignment to national standards, grade level/time, details on materials and preparation, procedure, assessment ideas, and modifications for alternative learners.

418

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

SciTech Connect

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

KL Gaustad; DD Turner

2007-09-30

419

Track effects of heavy ions in liquid water.  

PubMed

The various types of ionizing radiation can have widely differing radiation effects due to their variation in track structure. The effects of track structure on the radiation chemistry of water are particularly important because of the fundamental aspects and the wide range of practical applications. This review gives an overview of how the physics of energy-loss processes are responsible for the geometry of the particle track and thereby the final product yields. The radiation chemical effects are discussed in qualitative terms to show how the fundamental relationship between the physics and chemistry of particle tracks leads to the observed products. Special phenomena at very high rates of energy deposition are also covered. Finally, a discussion on the future research trends is given. PMID:10790268

LaVerne, J A

2000-05-01

420

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

E-print Network

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...

Rhoden, Alyssa R; Roth, Lorenz; Retherford, Kurt

2015-01-01

421

An Environmental Chamber to Investigate Liquid Saline Water in the Martian Polar Region  

NASA Astrophysics Data System (ADS)

We present the design of an environmental chamber to simulate the diurnal and seasonal cycles of the Martian polar region. This chamber is being built to aid in the investigation of liquid saline water in Mars' Richardson Crater (72 S, 179 E) and the Mars Phoenix Lander site (68 N, 126 W). Our objective is to: (i) determine the environmental conditions at with brines, formed from perchlorate salts found by the Mars Phoenix Lander, are stable on the surface of Mars and (ii) determine the optical properties of liquid saline wat