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1

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

2

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

PubMed

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. PMID:19894955

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

2009-10-28

3

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.

2011-04-15

4

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.

5

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

6

Polymorphism and metastable phenomena in liquid tin under pressure  

NASA Astrophysics Data System (ADS)

Polymorphism of substances under high pressures is observed and used to obtain materials with new physical properties. Here the authors present experimental results revealing phase transitions and structure of liquid tin at high pressure under metastable conditions using x-ray absorption spectroscopy and x-ray diffraction. They show that there is an abrupt change in the undercooling limit of liquid Sn above 2 GPa, where nucleation takes place into the Sn-III metastable solid phase. The liquid local structure is found to be composed of tetrahedral and close-packed configurations. The latter are found to dominate at high pressure favoring crystallization to the Sn-III metastable solid phase.

di Cicco, Andrea; Trapananti, Angela; Principi, Emiliano; de Panfilis, Simone; Filipponi, Adriano

2006-11-01

7

Liquid to quasicrystal transition in bilayer water.  

PubMed

The phase behavior of confined water is a topic of intense and current interest due to its relevance in biology, geology, and materials science. Nevertheless, little is known about the phases that water forms even when confined in the simplest geometries, such as water confined between parallel surfaces. Here we use molecular dynamics simulations to compute the phase diagram of two layers of water confined between parallel non hydrogen bonding walls. This study shows that the water bilayer forms a dodecagonal quasicrystal, as well as two previously unreported bilayer crystals, one tiled exclusively by pentagonal rings. Quasicrystals, structures with long-range order but without periodicity, have never before been reported for water. The dodecagonal quasicrystal is obtained from the bilayer liquid through a reversible first-order phase transition and has diffusivity intermediate between that of the bilayer liquid and ice phases. The water quasicrystal and the ice polymorphs based on pentagons are stabilized by compression of the bilayer and are not templated by the confining surfaces, which are smooth. This demonstrates that these novel phases are intrinsically favored in bilayer water and suggests that these structures could be relevant not only for confined water but also for the wetting and properties of water at interfaces. PMID:20969412

Johnston, Jessica C; Kastelowitz, Noah; Molinero, Valeria

2010-10-21

8

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

9

The physics of liquid water  

NASA Astrophysics Data System (ADS)

Water is a liquid with extraordinary properties: it has a very high cohesion, and an exceptionally strong dielectric cohesion, yet it is a fluid at ambient temperature and pressure. It also has an open structure that is full of voids, especially so at low temperatures. Some of these properties are found in other fluids, but the combination of all these anomalies makes liquid water unique among all other fluids. It is thanks to these unusual properties that life evolved in water and nowhere else. To cite this article: B. Cabane, R. Vuilleumier, C. R. Geoscience 337 (2005).

Cabane, Bernard; Vuilleumier, Rodolphe

2005-02-01

10

(Liquid + liquid) equilibrium for (dimethyl phthalate + water), (diethyl phthalate + water), and (dibutyl phthalate + water)  

Microsoft Academic Search

Data on (liquid + liquid) equilibrium in (dimethyl phthalate + water), (diethyl phthalate + water), and (dibutyl phthalate + water) have been measured by direct analytical methods over the temperature range (283 to 323) K. Gas chromatography and spectrophotometric methods have been employed to determine the composition of the organic substances in the liquid phases. The water content in the

Karel ?ehák; Jaroslav Matouš; Josef P. Novák; Magdalena Bendová

2000-01-01

11

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

PubMed Central

The polymorphic and metastable phase behavior of monoelaidin dry and in excess water was studied by using high-sensitivity differential scanning calorimetry and time-resolved x-ray diffraction in the temperature range of 4 degrees C to 60 degrees C. To overcome problems associated with a pronounced thermal history-dependent phase behavior, simultaneous calorimetry and time-resolved x-ray diffraction measurements were performed on individual samples. Monoelaidin/water samples were prepared at room temperature and stored at 4 degrees C for up to 1 week before measurement. The initial heating scan from 4 degrees C to 60 degrees C showed complex phase behavior with the sample in the lamellar crystalline (Lc0) and cubic (Im3m, Q229) phases at low and high temperatures, respectively. The Lc0 phase transforms to the lamellar liquid crystalline (L alpha) phase at 38 degrees C. At 45 degrees C, multiple unresolved lines appeared that coexisted with those from the L alpha phase in the low-angle region of the diffraction pattern that have been assigned previously to the so-called X phase (Caffrey, 1987, 1989). With further heating the X phase converts to the Im3m cubic phase. Regardless of previous thermal history, cooling calorimetric scans revealed a single exotherm at 22 degrees C, which was assigned to an L alpha+cubic (Im3m, Q229)-to-lamellar gel (L beta) phase transition. The response of the sample to a cooling followed by a reheating or isothermal protocol depended on the length of time the sample was incubated at 4 degrees C. A model is proposed that reconciles the complex polymorphic, mesomorphic, and metastability interrelationships observed with this lipid/water system. Dry monoelaidin exists in the lamellar crystalline (beta) phase in the 4 degrees C to 45 degrees C range. The beta phase transforms to a second lamellar crystalline polymorph identified as beta* at 45 degrees C that subsequently melts at 57 degrees C. The beta phase observed with dry monoelaidin is identical to the LcO phase formed by monoelaidin that was dispersed in excess water and that had not been previously heated. Images FIGURE 3

Chung, H; Caffrey, M

1995-01-01

12

Water ice polymorphs and their significance on planetary surfaces  

NASA Technical Reports Server (NTRS)

Impacts into an icy surface could produce significant amounts of high pressure forms of water ice. Due to the relatively low ambient surface temperatures on satellites in the outer solar system and the modest temperature rises accompanying the impact pressures required for water ice metamorphism, high-pressure polymorphs will be created by and may remain after large cratering events. If so, those high-pressure ices should be ubiquitous. Low-pressure cubic ice may be abundant as well. Impacts into an icy regolith may both produce high-pressure polymorphs from ice I and destroy high-pressure polymorphs already present. The result will be an (unknown) equilibrium concentration of high pressure polymorphs in the regolith. Polymorphs may be detectable and mappable by reflection spectroscopy at vacuum ultraviolet and mid-infrared wavelengths.

Gaffney, E. S.; Matson, E. L.

1980-01-01

13

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

14

Recent Liquid Water on Mars  

NASA Astrophysics Data System (ADS)

The presence of liquid water during a given epoch is of tremendous importance to both climatology and exobiology. Under present climatic conditions, water at the surface of Mars is almost exclusively in a solid or adsorbed state. Yet orbiter images reveal channels, valley networks, and other geomorphic indicators of the past existence of liquid water. Recent dynamical calculations suggest that the obliquity of Mars, which is presently at an Earth-like 25.2 degrees, has ranged chaotically from 0 to as much as 60 degrees over the last 100 Myr, and is unpredictable over longer timescales. At high obliquities, not only will the polar regions continuously experience intense solar radiation during local spring and summer, but the water currently trapped as ice in the polar caps may get released as water vapor, potentially leading to a water vapor greenhouse heating effect. Thus the polar regions should be the first places on the planet that might experience temperatures that exceed 273K throughout an entire Martian day. Our modeling of the Martian surface heat balance at high latitudes and obliquities in the recent past (i.e., during the last 100 Myr) indicates that liquid water has indeed been stable in the polar regions of Mars during local spring and summer. Previously, both Toon et al. (1980) and Jakosky et al. (1995) modeled the high-obliquity climate of Mars, and both concluded that liquid water would not be stable at high obliquity. However, our model differs from these previous models in three crucial respects: a sophisticated Voigt quasi-random atmospheric radiative transfer model (Crisp, 1994) is employed to assess the water vapor greenhouse; the effects of atmospheric dust are incorporated; and perhaps most importantly, idealized sublimation into a completely dry atmosphere is not assumed. Using the best estimates of Martian polar surface properties such as thermal inertia and albedo, we present a detailed map of the "critical obliquity" required to sustain stable liquid water as a function of latitude and surface composition.

Pathare, A.; Paige, D. A.

1996-09-01

15

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

16

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

17

Liquid-Liquid Critical Point in Heavy Water  

Microsoft Academic Search

According to the liquid-liquid critical-point hypothesis about water, two liquid waters exist at low temperatures and are supposed to be merged at a critical point. The low-temperature metastable melting curves of D2O ices have been measured. It is found that the melting curve of D2O ice III is smoothly curved around 25 MPa and 238 K, whereas the melting curve

Osamu Mishima

2000-01-01

18

Geomorphologic evidence for liquid water  

USGS Publications Warehouse

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

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

2001-01-01

19

Liquid Water on Early Mars  

NASA Technical Reports Server (NTRS)

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

Davis, Wanda L.; McKay, Christopher P.

1994-01-01

20

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

21

Water as a solid, liquid, and gas  

NSDL National Science Digital Library

The representation is a set of 3 diagrams, with accompanying text explanations, showing the arrangement of water molecules in each of its three states of matter and an activity that uses BB's and petri dishes to create models of ice, liquid water, and water vapor.

22

The Bethe surface of liquid water.  

SciTech Connect

The Bethe surface of liquid water, earlier calculated using a semi-empirical model, is compared with recent available data from IXS-experiments (inelastic X-ray scattering; Compton scattering of high energy photons) in liquid water. No alarming discrepancy is found on a global view of the Bethe surface. The extrapolation to the optical limit (viz., at zero momentum transfer) is shown and the reliability of these data is discussed in detail.

Dingfelder, M.

1998-10-14

23

Global cloud liquid water path simulations  

SciTech Connect

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

Lemus, L. [Southern Hemisphere Meteorology, Clayton, Victoria (Australia)] [Southern Hemisphere Meteorology, Clayton, Victoria (Australia); Rikus, L. [Bureau of Meteorology Research Centre, Melbourne, Victoria (Australia)] [Bureau of Meteorology Research Centre, Melbourne, Victoria (Australia); Martin, C.; Platt, R. [CSIRO, Aspendale, Victoria (Australia)] [CSIRO, Aspendale, Victoria (Australia)

1997-01-01

24

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

25

Liquid water production from atmospheric sources  

NASA Astrophysics Data System (ADS)

The purpose of this effort was to assess the feasibility of developing a desiccant system to produce potable water from atmospheric sources that is compatible with military constraints. Goals were: (1) to examine desiccant technology, investigate methods of using available desiccants to collect atmospheric moisture, (2) develop a conceptual model of a desiccant water production system, and (3) develop a mathematical model to simulate the operation of the conceptual model. Results show that a desiccant system can produce large quantities of potable water using relatively small amounts of fuel for heat and fan power. The focus of this project was using a liquid desiccant (such as triethylene glycol) in an absorption-distillation cycle. This report documents the theoretical analysis of a hypothetical liquid desiccant based system for producing liquid water through collection of atmospheric moisture. Estimates are made of cost, weight and water production rate for the hypothetical system.

Matthews, John D.; Clarke, Norman P.

1991-02-01

26

Micro liquid–liquid extraction of synthetic pyrethroids from surface waters for liquid-chromatographic determination  

Microsoft Academic Search

A micro liquid–liquid extraction (MLLE) flask designed for the extraction of bioavailable synthetic pyrethroids from agricultural and ground water samples is used. The method is simple, rapid, and reproducible. Extracts are analyzed off-line by reversed-phase high-performance liquid chromatography (RP-HPLC). A volume of 100?µL n-hexane is sufficient for recovery of the three pyrethroids from 100?mL water. Further clean-up is not required

Saeed S. Albaseer; R. Nageswara Rao; Y. V. Swamy; K. Mukkanti; Boje Gowda Bandi

2011-01-01

27

Micro liquid-liquid extraction of synthetic pyrethroids from surface waters for liquid-chromatographic determination  

Microsoft Academic Search

A micro liquid-liquid extraction (MLLE) flask designed for extraction of bioavailable synthetic pyrethroids from agricultural and ground waters is used. The method is simple, rapid and reproducible. Extracts are analysed off-line by reversed-phase high performance liquid chromatography (RP-HPLC). A volume of 100??L n-hexane is sufficient for recovery of the three pyrethroids from 100?mL water. Further clean-up is not required before

Saeed S. Albaseer; R. Nageswara Rao; Y. V. Swamy; K. Mukkanti; Boje Gowda Bandi

2011-01-01

28

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

29

THz reflection spectroscopy of liquid water  

Microsoft Academic Search

We report an investigation of the temperature-dependent far-infrared spectrum of liquid water. We have employed a new experimental technique based on ultrashort electromagnetic pulses (THz pulses). This technique allows for fast and reliable data of both index of refraction and absorption coefficient for highly absorbing liquids. The temperature dependence reveals an enthalpy of activation corresponding to 2.5 kcal\\/mol, in agreement

L. Thrane; R. H. Jacobsen; P. Uhd Jepsen; S. R. Keiding

1995-01-01

30

Polymorphous Structures and Their Phase Relationships in a Main-Chain\\/Side-Chain Liquid Crystalline Polyester  

Microsoft Academic Search

A series of specially designed polyesters consisting aromatic main-chain\\/side-chain liquid crystalline (LC) polymers have been synthesized (PEFBP (n), where n is the number of methylene units in the side chains). For a PEFBP (n = 7) polyester, complicated polymorphism has been found, which includes three triclinic crystalline (Kt1, Kt2 and Kt3) phases, one highly ordered LC smectic phase (SKO) having

Jrjeng Ruan; Jason J. Ge; Anqiu Zhang; Jin Shi; Shy-Yeu Wang; Frank W. Harris; Stephen Z. D. Cheng

2002-01-01

31

Re-sequencing of multiple single nucleotide polymorphisms by liquid chromatography-electrospray ionization mass spectrometry  

Microsoft Academic Search

Allelic discrimination of single nucleotide poly- morphisms (SNPs) and, particularly, determination of the phase of multiple variations are of utmost importance in genetics. The physicochemical separ- ation of alleles by completely denaturing ion-pair reversed-phase high-performance liquid chromato- graphy and their on-line sequence determination by electrospray ionization mass spectrometry is dem- onstrated. Simultaneous genotyping of two and three simple sequence polymorphisms

H. Oberacher; P. J. Oefner; G. Holzl; A. Premstaller; K. Davis; C. G. Huber

2002-01-01

32

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

SciTech Connect

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

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

2009-05-27

33

PH-induced nanosegregation of ritonavir to lyotropic liquid crystal of higher solubility than crystalline polymorphs.  

PubMed

Birefringent spherical vesicles of ritonavir (RTV) are formed by increasing the pH of aqueous solutions from 1 to 3 or to 7 and by addition of water to ethanol solutions at room temperature. Increasing the pH creates supersaturation levels of 30-400. Upon this change in pH, the solutions become translucent, implying that some kind of RTV assembly was formed. Small spherical vesicles of narrow size distribution are detectable only after a few hours by optical microscopy. The vesicles show similar X-ray diffraction patterns and differential scanning calorimetry (DSC) behavior to amorphous RTV prepared by melt-quenching crystalline RTV. Examination by polarized optical microscopy suggests that these are lyotropic liquid crystalline (LLC) assemblies. Small-angle X-ray scattering and synchrotron X-ray diffraction further support the presence of orientational order that is associated with a nematic structure. RTV self-organizes into various phases as a result of the supersaturation created in aqueous solutions. The LLC vesicles do not fuse but slowly transform to the polymorphs of RTV (in days), Form I and finally Form II. Amorphous RTV in aqueous suspension also undergoes a transformation to a mesophase of similar morphology. Transformation pathways are consistent with measured dissolution rates and solubilities: amorphous > LLC > Form I > Form II. The dissolution and solubility of LLC is slightly lower than that of the amorphous phase and about 20 times higher than that of Form II. RTV also self-assembles at the air/water interface as indicated by the decrease in surface tension of aqueous solutions. This behavior is similar to that of amphiphilic molecules that induce LLC formation. PMID:19434919

Rodríguez-Spong, Barbara; Acciacca, Alison; Fleisher, David; Rodríguez-Hornedo, Naír

2008-01-01

34

A study of pressure-induced polymorphism in liquid GeO2  

NASA Astrophysics Data System (ADS)

Pressure-induced polymorphism in liquid GeO2 has been investigated by a molecular dynamic model with 1998 atoms and Oeffner-Elliot potential. The simulation reveals that liquid GeO2 is made up of the species GeOx with fraction depending on density. Here x = 4, 5 and 6. This viewpoint is supported by the fact that the density, the oxygen-connectivity and the volume of void could be expressed as a linear function of the GeOx fractions. The structural change that occurs upon compression is analysed through both atom- and void-species and discussed here.

Hung, P. K.; Hong, N. V.; Nhan, N. T.; Vinh, L. T.

2007-12-01

35

Water is a molecular liquid  

NASA Astrophysics Data System (ADS)

Science and society are failing to grapple with the public health burden of cancer. In this short perspective piece, I contrast reductionism and complexity in cancer research, using water as a simple example, arguing for more ‘ecological’ approaches to cancer. This is a call to arms to physical scientists, ecologists and others to get involved, to link up with cancer clinicians and cancer biologists, and an appeal to funding agencies to link up across disciplines to make a difference. This perspective is dedicated to the memory of Dr Kenneth Mossman (1946–2014).

Newman, Timothy

2014-06-01

36

Theory of water and charged liquid bridges  

NASA Astrophysics Data System (ADS)

The phenomenon of liquid bridge formation due to an applied electric field is investigated. A solution of a charged catenary is presented, which allows one to determine the static and dynamical stability conditions where charged liquid bridges are possible. The creeping height, the bridge radius and length, as well as the shape of the bridge are calculated showing an asymmetric profile, in agreement with observations. The flow profile is calculated from the Navier-Stokes equation leading to a mean velocity, which combines charge transport with neutral mass flow and which describes recent experiments on water bridges.

Morawetz, K.

2012-08-01

37

Random Amplified Polymorphic DNA Analysis of Water Spinach ( Ipomoea aquatica ) in Florida  

Microsoft Academic Search

The genetic relationship between three biotypes of water spinach ( Ipomoea aquatica Forsk.), including one 'upland' agricultural cultivar and two floating wild biotypes collected from Hillsborough County, Florida, were evaluated using Random Amplified Polymorphic DNA (RAPD) markers. Forty-eight decamer primers were screened; eighteen of these were informative and yielded 188 resolvable bands, of which 58 (31%) were polymorphic. Five primers

THAI K. VAN; P. T. MADEIRA

38

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.

39

Multifractal characterization of liquid water in clouds  

SciTech Connect

The variations of atmospheric quantities are often represented by highly fluctuating time series. Therefore, specially designed analysis tools are needed to study signals which vary on many scales. Recently, Davis {ital et al.} [J. Geophys. Res. {bold 99}, 8055 (1994)] proposed a new technique for analysis of complex nonlinear geophysical processes observed over large time or space scales. The approach is aimed at investigating nonstationarity and intermittency as two complementary features of the geophysical fields. We apply the multifractal analysis to a liquid water path time series obtained via ground-based remote sensing measurements. On the (H{sub 1},C{sub 1}) plane we compare the results from this study with the results of direct measurements of liquid water content during the same field program and those reported by other authors. {copyright} {ital 1999} {ital The American Physical Society}

Ivanova, K. [Laboratoire de Telecommunications et Teledetection, Universite Catholique de Louvain, Place du Levant 2, B-1348 Louvain-la-Neuve (Belgium)] [Laboratoire de Telecommunications et Teledetection, Universite Catholique de Louvain, Place du Levant 2, B-1348 Louvain-la-Neuve (Belgium); Ackerman, T. [Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, Pennsylvania 16802 (United States)] [Department of Meteorology, Pennsylvania State University, 503 Walker Building, University Park, Pennsylvania 16802 (United States)

1999-03-01

40

Liquid water habitats on early Mars  

NASA Technical Reports Server (NTRS)

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

Mckay, Christopher P.; Davis, Wanda L.

1992-01-01

41

Liquid-liquid equilibria of fuel oxygenate + water + hydrocarbon mixtures. 2  

Microsoft Academic Search

The liquid-liquid equilibria of water + n-decane, water + n-hexadecane, and water + methylcyclohexane have been measured separately with the two oxygenates 2-methoxy-2-methylbutane (tertiary amyl methyl ether or TAME) and 2-methyl-2-butanol (tertiary amyl alcohol or TAOH) at 25 C. All of these systems exhibit type 2 liquid-liquid phase diagrams, through the shapes of the diagrams for the TAME and TAOH

S. Hellinger; S. I. Sandler

2009-01-01

42

Liquid-liquid equilibria of fuel oxygenate + water + hydrocarbon mixtures. 1  

Microsoft Academic Search

The authors have measured the liquid-liquid equilibria of water + 2, 2, 4-trimethylpentane and water + toluene separately with the four oxygenates ethanol, 2-methoxy-2-methylpropane (methyl tert-butyl ether or MTBE), 2-methoxy-2-methylbutane (tert-amyl methyl ether or TAME), and 2-methyl-2-butanol (tert-amyl alcohol or TAOH) at 25 C. Ethanol with the water + hydrocarbon systems forms a type 1 liquid-liquid phase diagram, while the

N. Peschke; S. I. Sandler

2009-01-01

43

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

44

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

45

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

46

Streamers in water and other dielectric liquids  

NASA Astrophysics Data System (ADS)

Experimental results on the inception and propagation of streamers in water generated under the application of high electric fields are reviewed. Characteristic parameters, such as breakdown voltage, polarity of the applied voltage, propagation velocities and other phenomenological features, are compared with similar phenomena in other dielectric liquids and in gases. Consequently, parameters that are expected to influence the development of streamers in water are discussed with respect to the analogous well-established models and theories for the related mechanisms in gases. Most of the data support the notion that an initial low-density nucleation site or gas-filled bubble assists the initiation of a streamer. Details of this theory are laid out explaining the observed differences in the breakdown originating from the anode versus the cathode locations. The mechanisms can also be applied to streamer propagation, although some observations cannot be satisfactorily explained.

Kolb, J. F.; Joshi, R. P.; Xiao, S.; Schoenbach, K. H.

2008-12-01

47

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

48

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

49

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

Microsoft Academic Search

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

Kiyofumi Kurihara; Kouichi Takeda; Kazuo Kojima; Tsuyoshi Minoura

1995-01-01

50

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 100 eV, 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

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

2013-10-25

51

Vapor-liquid and liquid-liquid equilibria of water, 2-methoxyethanol and cyclohexanone: Experiment and correlation  

Microsoft Academic Search

Vapor-liquid equilibria and liquid-liquid equilibria of a ternary mixture consisting of water, 2-methoxyethanol and cyclohexanone and in addition of all binary subsystems were studied experimentally at several temperatures. A ternary corrective term in the expression for the Gibbs free energy based on the NRTL model improves simultaneous representation of binary and ternary phase equilibria.

T. Hauschild; H. Knapp

1994-01-01

52

Liquid–liquid equilibrium data of water with neohexane, methylcyclohexane, tert-butyl methyl ether, n-heptane and vapor–liquid–liquid equilibrium with methane  

Microsoft Academic Search

Liquid–liquid equilibrium (LLE) data for non-aqueous liquid (neohexane [NH], tert-butyl methyl ether [TBME], methylcyclohexane [MCH], or n-heptane [nC7]) and water have been measured under atmospheric pressure at 275.5, 283.15, and 298.15K. It was found that TBME is the most water soluble followed by NH, MCH, and nC7. As the temperature increased, the solubility of the non-aqueous liquids (NALs) in water

R. Susilo; J. D. Lee; P. Englezos

2005-01-01

53

Physical and Thermodynamical Evidence for Liquid Water on Mars  

NASA Astrophysics Data System (ADS)

We show independent physical and thermodynamical evidence that liquid saline-water exists in areas disturbed by the Phoenix lander and that the thermodynamics of freeze-thaw cycles leads to the formation brine layers. Thus, liquid saline-water might be common on Mars.

Renno, N. O.; Bos, B. J.; Catling, D.; Clark, B. C.; Drube, L.; Fisher, D.; Goetz, W.; Hviid, S. F.; Keller, H. U.; Kok, J. F.; Kounaves, S. P.; Leer, K.; Lemmon, M.; Madsen, M. B.; Markiewicz, W. J.; Marshall, J.; McKay, C.; Mehta, M.; Smith, M.; Smith, P. H.; Stoker, C.; Young, S. M. M.; Zent, A.

2009-03-01

54

Liquid water transport mechanism in the gas diffusion layer  

Microsoft Academic Search

We developed an equivalent capillary model of a microscale fiber-fence structure to study the microscale evolution and transport of liquid in a porous media and to reveal the basic principles of water transport in gas diffusion layer (GDL). Analytical solutions using the model show that a positive hydraulic pressure is needed to drive the liquid water to penetrate through the

P. Zhou; C. W. Wu

2010-01-01

55

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

SciTech Connect

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

Wagner, G. [Universitaet Karlsruhe (Germany). Institut fuer Thermische Verfahrenstechnik; Sandler, S.I. [Univ. of Delaware, Newark, DE (United States). Center for Molecular and Engineering Thermodynamics

1995-09-01

56

Isobaric vapor–liquid and vapor–liquid–liquid equilibrium data for the system water + ethanol + cyclohexane  

Microsoft Academic Search

Isobaric vapor–liquid (VLE) and vapor–liquid–liquid equilibria (VLLE) were measured for the ternary system water+ethanol+cyclohexane at 101.3kPa. The experimental determination was carried out in a dynamic equilibrium still with circulation of both the vapor and liquid phases, equipped with an ultrasonic homogenizer. The experimental data demonstrated the existence of a ternary heterogeneous azeotrope at 335.6K with a composition of 0.188, 0.292,

V. Gomis; R. Pedraza; M. D. Saquete

2005-01-01

57

Liquid–liquid equilibria and vapor–liquid equilibria for the binary system of epichlorohydrin and water  

Microsoft Academic Search

The liquid–liquid equilibria (LLE) data and vapor–liquid equilibria (VLE) data for the binary system of epichlorohydrin (EPCH)+water were studied at 101.3kPa. An azeotropic behavior has been found in the EPCH+water. Both the experimental LLE and VLE data were compared with the correlated values obtained by means of the NRTL and UNIQUAC equations. Both models satisfactorily correlated the experimental data. Thermodynamic

Qun Yue; Jia-wen Zhu; Yan-yang Wu; Xiang-qian Yuan; Liang Ma

2009-01-01

58

Rapid determination of 226 Ra in drinking water samples using dispersive liquid-liquid microextraction coupled with liquid scintillation counting  

Microsoft Academic Search

A new radioanalytical method was developed for rapid determination of 226Ra in drinking water samples. The method is based on extraction and preconcentration of 226Ra from a water sample to an organic solvent using a dispersive liquid-liquid microextraction (DLLME) technique followed by\\u000a radiometric measurement using liquid scintillation counting. In DLLME for 226Ra, a mixture of an organic extractant (toluene doped

Baki B. Sadi; Chunsheng Li; Gary H. Kramer; Cassandra L. Johnson; Queenie Ko; Edward P. C. Lai

59

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...

60

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 ...

61

Evidence for Recent Liquid Water on Mars  

NASA Technical Reports Server (NTRS)

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

2000-01-01

62

Limit of Metastability for Liquid and Vapor Phases of Water  

NASA Astrophysics Data System (ADS)

We report the limits of superheating of water and supercooling of vapor from Monte Carlo simulations using microscopic models with configurational enthalpy as the order parameter. The superheating limit is well reproduced. The vapor is predicted to undergo spinodal decomposition at a temperature of Tspvap=46±10 °C (0 °C ?Tspvap?100 °C) under 1 atm. The water-water network begins to form at the supercooling limit of the vapor. Three-dimensional water-water and cavity-cavity unbroken networks are interwoven at critically superheated liquid water; if either network breaks, the metastable state changes to liquid or vapor.

Cho, Woo Jong; Kim, Jaegil; Lee, Joonho; Keyes, Thomas; Straub, John E.; Kim, Kwang S.

2014-04-01

63

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

64

Water Percolation Governs Polymorphic Transitions and Conductivity of DNA  

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

65

Isobaric vapor–liquid and vapor–liquid–liquid equilibrium data for the water–ethanol–hexane system  

Microsoft Academic Search

Isobaric vapor–liquid and vapor–liquid–liquid equilibria were measured for the water–ethanol–hexane system at normal atmospheric pressure. The apparatus used for the determination of vapor–liquid–liquid equilibrium data was an all-glass dynamic recirculating still with an ultrasonic homogenizer coupled to the boiling flask.The experimental data demonstrated the existence of a ternary heterogeneous azeotrope at 329.2K with a composition of 0.105, 0.236 and 0.658mol

V. Gomis; R. Pedraza; M. D. Saquete

2007-01-01

66

Anatomy of competing quantum effects in liquid water.  

NASA Astrophysics Data System (ADS)

ct- Molecules like water have vibrational modes with zero point energy well above room temperature. As a consequence, classical molecular dynamics simulations of liquid water largely underestimate the kinetic energy of the ions, which translates into an underestimation of covalent interatomic distances. In this work, we show that it is possible to apply generalized Langevin equation with suppressed noise in combination with Nose-Hoover thermostats to achieve an efficient zero-point temperature of independent modes of liquid water. Using this method we deconstruct the competing quantum effects in liquid water. We demonstrate how the structure and dynamical modes of liquid water respond to non-equilibrium distribution of zero point temperatures on the normal modes.

Ramirez, Rafa; Ganeshan, Sriram; Fernandez-Serra, M. V.

2013-03-01

67

Cloud top liquid water from lidar observations of marine stratocumulus  

NASA Technical Reports Server (NTRS)

Marine stratus clouds were simultaneously observed by nadir Nd:YAG lidar measurements and in situ cloud physics measurements. A procedure was applied to derive the two-dimensional vertical cross section of the liquid water from within the cloud top lidar observations. A comparison to direct in-cloud liquid water observations gave good results. The liquid water retrieval was limited to an effective optical depth of 1.5. The true cloud optical thickness was also obtained from the retrieval procedure to a corresponding limit of 3.8. The optical thickness of the observed marine stratus clouds was predominantly below 3.0.

Spinhirne, J. D.; Boers, R.; Hart, W. D.

1989-01-01

68

FBG application in monitoring the liquid-solid and gas-liquid phase transitions of water  

NASA Astrophysics Data System (ADS)

We propose to monitor the liquid-solid and gas-liquid phase transition of water based on FBG sensors. The naked FBGs and the packaged FBG temperature sensors are used to monitoring the liquid-solid phase transition of water at the same time in order to find its characteristics, including the supercooling state and the strain and pressure change introduced by the phase transition. Fourteen FBGs are packaged and arranged in a steam boiler in order to monitor the gas-liquid phase transition, including the temperature and pressure change inside the steam boiler and the strain of the boiler wall. The preliminary experimental results are demonstrated here.

Quan, Chai; Later, Khalil; Yang, Lijie; Peng, Shijun; Zhang, Anna; Hao, Qianqian; Zhang, Jianzhong; Sun, Weimin; Yuan, Libo; Peng, G. D.

2012-01-01

69

Recent Liquid Water in the Polar Regions of Mars  

NASA Astrophysics Data System (ADS)

The potential presence of liquid water on a planetary body during a given epoch is important to both climatology and exobiology. Our modeling of the martian surface heat balance at high latitudes and obliquities in the recent past (i.e., during the last 100 m.y.) indicates that liquid water has been stable during local spring and summer in the polar regions of Mars. Previous martian climate models concluded that liquid water would not be stable at high obliquity. However, our model differs from these previous models in three crucial respects: A more detailed atmospheric radiative transfer model is employed to assess the surface heating due to a water vapor greenhouse; the effects of atmospheric dust are incorporated; and, perhaps most importantly, idealized sublimation into a dry atmosphere is not assumed. Our results indicate that liquid water would indeed be stable at the martian poles at obliquities of 45 degrees and higher during much of local spring and summer. Furthermore, using the best estimates of martian near-polar surface properties such as thermal inertia and albedo, we also find that such liquid water "oases" would also be stable just off of the northern polar cap at obliquities as low as 35 degrees. The importance of such stable liquid water to climatology is twofold, as water not only influences climate but also readily erodes the surface, thereby recording past climate change. We will attempt to discuss the geologic evidence for such change in the context of new observations from Mars Global Surveyor.

Pathare, A. V.; Paige, D. A.

1998-01-01

70

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 70°N. The longest water ice coverage without CO2 ice is observed between 40-55°N and 300-330°E 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; Appéré, Thomas

2014-08-01

71

High frequency, realtime measurements of stable isotopes in liquid water  

NASA Astrophysics Data System (ADS)

We developed a method to measure in-situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a off-the-shelf microporous hydrophobic membrane contactor for under 200€ was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with nitrogen as carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the isotope laser spectrometer. To prove the membrane's applicability we determined the specific isotope fractionation factor for the phase change through the contactor's membrane for a common temperature range and with different waters of known isotopic compositions. This fractionation factor is then used to derive the liquid water isotope ratio from the measured water vapor isotope ratios and the measured temperature at the phase change. The system was compared for breakthrough curves of isotopically enriched water and the isotope values corresponded very well with those of liquid water samples taken simultaneously and analyzed with a conventional method (CRDS). The introduced method supersedes taking liquid samples and employs only relative cheap and readily available components. This makes it a relatively inexpensive, fast, user-friendly and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real-time isotope data of liquid water are required at high temporal resolution with the same accuracy as collecting individual water samples.

Weiler, M.; Herbstritt, B.; Gralher, B.

2012-04-01

72

Vapor-liquid and liquid-liquid equilibria and critical states of water + n-decane mixtures  

SciTech Connect

Mixtures of water and hydrocarbons exhibit a rich variety of fluid phase behavior that is of technological interest because of the common occurrence of these mixtures in chemical processes, in oil reservoirs, in the environment, and other instances. The weak interaction between water and hydrocarbon molecules contrasts sharply with the strong interaction between water and water molecules in the same mixture. The extreme dissimilarity of the molecular interactions manifested as highly non-ideal solution behavior invites unusual attention. Vapor-liquid equilibrium and liquid-liquid equilibrium are observed in disjointed regions at 573.2, 593.2, and 613.2 K for mixtures of water +n-decane at pressures up to 230 bar. Vapor-liquid critical states are determined at the temperatures studied.

Wang, Qi; Chao, Kwangchu (Purdue Univ., West Lafayette, IN (United States))

1990-01-01

73

Glass-liquid transition of water at high pressure.  

PubMed

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

Andersson, Ove

2011-07-01

74

Glass-liquid 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 1 GPa and temperatures below approximately 140 K, but a corresponding liquid phase has not been detected. Here we report results of heat capacity Cp and thermal conductivity, in situ, measurements, which are consistent with a reversible transition from annealed HDA to ultraviscous high-density liquid water at 1 GPa and 140 K. On heating of HDA, the Cp increases abruptly by (3.4 ± 0.2) J mol-1 K-1 before crystallization starts at (153 ± 1) K. This is larger than the Cp rise at the glass to liquid transition of annealed ASW at 1 atm, which suggests the existence of liquid water under these extreme conditions.

Andersson, Ove

2011-01-01

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

Complete vitrification in pure liquid water and dilute aqueous solutions  

Microsoft Academic Search

Pure water can only be vitrified by the very slow condensation of vapour on a metal surface maintained at very low temperatures1,2. Attempts to form vitreous ice by rapid cooling of liquid water invariably lead to formation of ice Ih (ref. 3). (Pryde and Jones4 did report a heat capacity change of rapidly cooled water at 126 K which they

Peter Brüggeller; Erwin Mayer

1980-01-01

77

The relationship between liquid, supercooled and glassy water  

Microsoft Academic Search

That water can exist in two distinct `glassy' forms - low- and high-density amorphous ice - may provide the key to understanding some of the puzzling characteristics of cold and supercooled water, of which the glassy solids are more-viscous counterparts. Recent experimental and theoretical studies of both liquid and glassy water are now starting to offer the prospect of a

Osamu Mishima; H. Eugene Stanley

1998-01-01

78

Liquid water in the extremely shallow Martian subsurface  

NASA Astrophysics Data System (ADS)

The discovery of a near-surface ice layer on Mars by the Phoenix lander has led to speculation about the stability of water in the subsurface, as the availability of liquid water is a major constraint for a potential Martian biosphere. Liquid water is unstable on the surface of Mars due to low atmospheric pressures, but it has been suggested that liquid water might be present as films or adsorbed layers in the regolith. This study was carried out to assess the stability of permafrost and liquid water in the Martian subsurface, and to support the interpretation of conductivity data from the Phoenix mission. Using a new Goddard Martian simulation chamber, we explored the possibility of liquid water formation in the extremely shallow (1-3 cm) subsurface soil layer under low atmospheric pressures (0.1-10 mbar) and analogous Martian surface temperatures (~ -50 C to 0 C). This was achieved through the use of impedance spectroscopy with conductivity probes similar to those used by Phoenix. Our results demonstrate that in a shallow layer of clean permafrost the amount of mobile liquid water present as films can reach several percent, even with temperatures as low as -25 C. The presence of perchlorates, found in the Martian regolith, causes the formation and mobility of liquid water to increase dramatically due to the effects of perchlorates on the melting temperature of ice. This study suggests that despite cold temperatures and low atmospheric pressures, the Martian regolith may contain appreciable amounts of liquid water in the near subsurface. Permafrost on Mars can be expected to extend to some depth, particularly in polar latitudes. These findings have implications for aqueous processing on Mars and the habitability of the Martian subsurface throughout its history.

Shivak, J. N.; Pavlov, A.

2012-12-01

79

Liquid water in the domain of cubic crystalline ice Ic.  

PubMed

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. PMID:11542399

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

1997-07-22

80

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

81

High pressure vapor-liquid and vapor-liquid-liquid equilibria for systems containing supercritical carbon dioxide, water and furfural  

Microsoft Academic Search

We measured vapor-liquid equilibrium for a binary system CO2?furfural at temperatures of 303 and 323 K and vapor-liquid-liquid equilibrium for a ternary system CO2?water?furfural at temperatures of 303, 323 and 343 K and pressure of 5 MPa to obtain fundamental data for concentration of furfural by using three phase separation technique. Furthermore the experimental data were compared with results calculated

Takeshi Sako; Tsutomu Sugeta; Noriaki Nakazawa; Katsuto Otake; Masahito Sato; Katsuo Ishihara; Masahiro Kato

1995-01-01

82

Speciation analysis of mercury in water samples using dispersive liquid–liquid microextraction combined with high-performance liquid chromatography  

Microsoft Academic Search

A novel approach for preconcentration and speciation analysis of trace amount of mercury from water samples was proposed by dispersive liquid–liquid microextraction (DLLME) coupled to high performance liquid chromatography with diode array detection (HPLC-DAD). Mercury species (Hg2+, methylmercury (MeHg+) and phenylmercury (PhHg+)) were complexed with dithizone (DZ) to form hydrophobic chelates and then extracted into the fine drops of extraction

Zhongben Gao; Xiaoguo Ma

2011-01-01

83

Isobaric vapor-liquid equilibrium for ethanol + water + potassium nitrate  

Microsoft Academic Search

An increasing research interest in the determination of the salt effect in the vapor-liquid equilibrium of binary systems has developed over the last few decades due to the importance of distillation with salts in the separation of close boiling and azeotropic mixtures. Isobaric vapor-liquid equilibrium for ethanol (1) + water (2) + potassium nitrate (3) at various concentrations of salt

Ernesto Vercher; M. Pilar Peña; Antoni Martinez-Andreu

1996-01-01

84

Isobaric vapor-liquid equilibrium for ethanol + water + strontium nitrate  

Microsoft Academic Search

The effect of salts on the vapor-liquid equilibrium of solvent mixtures is of considerable interest in the separation of close boiling and azeotropic mixtures. The salt effect has been studied by many researchers. Most investigations have been limited to measurements on the saturated salt solutions. Isobaric vapor-liquid equilibrium for ethanol (1) + water (2) + strontium nitrate (3) at various

Ernesto Vercher; M. Pilar Peña; Antoni Martinez-Andreu

1996-01-01

85

Isobaric vapor-liquid equilibria of water + ethanol + hexyl acetate  

SciTech Connect

The authors determined the isobaric vapor-liquid equilibrium data for the ternary system water + ethanol + hexyl acetate at 101.325 kPa using a distillation apparatus recycling both liquid and vapor phases. The results were compared with those predicted using group contribution methods. The UNIFAC method gave the best predictions.

Arce, A.; Soto, A. [Univ. of Santiago de Compostela (Spain). Chemical Engineering Dept.; Orge, B.; Tojo, J. [Univ. of Vigo (Spain). Chemical Engineering Dept.

1995-09-01

86

Liquid-liquid transition in supercooled water suggested by microsecond simulations  

PubMed Central

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

Li, Yaping; Li, Jicun; Wang, Feng

2013-01-01

87

Continuous in situ measurements of stable isotopes in liquid water  

NASA Astrophysics Data System (ADS)

We developed a method to measure in situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a microporous hydrophobic membrane contactor (Membrana) was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with N2 as a carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the Picarro analyzer. To prove the membrane's applicability, we determined the specific isotope fractionation factor for the phase change through the contactor's membrane across an extended temperature range (8°C-21°C) and with different waters of known isotopic compositions. This fractionation factor is needed to subsequently derive the liquid water isotope ratio from the measured water vapor isotope ratios. The system was tested with a soil column experiment, where the isotope values derived with the new method corresponded well (R2 = 0.998 for ?18O and R2 = 0.997 for ?2H) with those of liquid water samples taken simultaneously and analyzed with a conventional method (cavity ring-down spectroscopy). The new method supersedes taking liquid samples and employs only relatively cheap and readily available components. This makes it a relatively inexpensive, fast, user-friendly, and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real-time isotope data of liquid water are required at high temporal resolution.

Herbstritt, Barbara; Gralher, Benjamin; Weiler, Markus

2012-03-01

88

Redox reactions at liquid hydrocarbon\\/water interfaces: biophysical aspects  

Microsoft Academic Search

The liquid hydrocarbon\\/water interface with immobilized amphiphilic catalysts can serve as the simplest model of biological membrane convenient for the investigation of redox reaction accompanied by spatial separation of charges. In this review, we have described the vectorial redox reactions at oil\\/water interfaces. The structure of liquid interfaces, donor–acceptor interactions in the electrical double layer, specific bounding between molecules plays

Alexander G. Volkov

1998-01-01

89

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

Microsoft Academic Search

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

Sadhana Sharma; Girish Pandya; Tapan Chakrabarti; Purushottam Khanna

1994-01-01

90

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

91

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

92

Rapid micro liquid-liquid extraction method for trace analysis of organic contaminants in drinking water  

Microsoft Academic Search

The applicability and performance of a micro liquid-liquid extraction method for trace analysis of organic compounds in drinking water is reported. Tap water samples of 400 ml are saturated with sodium chloride and extracted once with 500 ?1 of toluene. Extracts are analyzed directly without further treatment by gas chromatograph using simultaneous electron-capture and nitrogen-phosphorus detection. Recoveries of 82 organic

Andreas Zapf; Regine Heyer; Hans-Jürgen Stan

1995-01-01

93

Electron localization in laser ionization of liquid water  

Microsoft Academic Search

Based on the hypothesis that a mobile (quasi-free) precursor of the localized “infrared” electron exists in water, a new mechanism of photoionization of liquid water is proposed to describe the data on picosecond and femtosecond laser photolysis. According to this mechanism, the fast recombination of the mobile electron with its parent ion governs both the quantum yield and absorption kinetics

L. V. Lukin

1995-01-01

94

Ionic Liquid Lubrication Effects on Ceramics in a Water Environment  

Microsoft Academic Search

Ionic liquids were studied to determine their effectiveness as boundary lubricant additives for water. The chemical and tribochemical reactions that govern their behavior were probed to understand lubrication mechanisms. Under water lubricated conditions, silicon nitride ceramics are characterized by a running-in period of high friction, during which time the surface is modified causing a dramatic decrease in friction and wear.

B. S. Phillips; J. S. Zabinski

2004-01-01

95

Nonaqueous phase liquid drop formation within a water saturated fracture  

Microsoft Academic Search

This work focuses on the mechanisms of non-aqueous phase liquid (NAPL) drop formation within a single fracture fed from a NAPL reservoir by way of a circular orifice, such as a pore. The fracture is assumed to be fully saturated, the relative wettability of the system is assumed water-wet, and the water velocity profile within the fracture is described by

Kent M. Pumphrey; Constantinos V. Chrysikopoulos

2004-01-01

96

Satellite remote sensing of the liquid water sensitivity in water clouds  

Microsoft Academic Search

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

Qingyuan Han; William B. Rossow; Jane Zeng; Ronald Welch

2001-01-01

97

Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water  

Microsoft Academic Search

Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of

Hiroharu Yui; Tsuguo Sawada

2003-01-01

98

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 Henry’s 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

99

Searching for liquid water in Europa by using surface observatories.  

PubMed

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

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

2002-01-01

100

Liquid and Glassy Water: Two Materials of Interdisciplinary Interest  

NASA Astrophysics Data System (ADS)

We can superheat water above its boiling temperature and supercool it below its freezing temperature, down to approximately — 40°C, below which water inevitably crystallizes. In this deeply supercooled region, strange things happen: response functions and transport functions appear as if they might diverge to infinity at a temperature of about-45 °C. These experiments were pioneered by Angell and co-workers over the past 30 years [1-4]. Down in the glassy region of water, additional strange things happen, e.g., there is not just one glassy phase [1]. Rather, just as there is more than one polymorph of crystalline water, so also there appears to be more than one polyamorph of glassy water. The first clear indication of this was a discovery of Mishima in 1985: at low pressure there is one form, called low-density amorphous (LDA) ice [5], while at high pressure Mishima discovered a new form, called highdensity amorphous (HDA) ice [6]. The volume discontinuity separating these two phases is comparable to the volume discontinuity separating low-density and high-density polymorphs of crystalline ice, 25-35 percent [7, 8].

Eugene Stanley, H.

101

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

PubMed

This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys. 135, 134503 (2011) and preprint 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. PMID:23758385

Limmer, David T; Chandler, David

2013-06-01

102

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

103

Physical and Thermodynamical Evidence of Liquid Water on Mars  

NASA Astrophysics Data System (ADS)

The objective of the Phoenix Mars mission is to determine if Mars' polar region can support life. Since liquid water is a basic ingredient for life, as we know, an important goal of the mission is to determine if liquid water exists at the landing site. It is believed that a layer of martian soil preserves ice by forming a barrier against sublimation, but that exposed ice sublimates without the formation of the liquid phase. Here we show physical and thermodynamical evidence that besides ice, liquid saline-water exists in areas disturbed by the Phoenix lander. Moreover, we show that the thermodynamics of freezing/thaw cycles ranging from diurnal to climatic time-scales leads to the formation of saline solutions with freezing temperatures much higher than current summer ground temperatures where surface ice is believed to exist near the surface. Thus, we hypothesize that liquid saline-water is common on Mars. This discovery has important implications for the stability of water, weathering, glaciology, mineralogy, geochemistry and the habitability of Mars.

Renno, N. O.; Bos, B. J.; Clark, B. C.; Drube, L.; Goetz, W.; Keller, H. U.; Kounaves, S.; Leer, K.; Lemmon, M.; Madsen, M. B.; Markiewicz, W.; Marshall, J.; Mackay, C.; Mehta, M.; Mellon, M.; Smith, M.; Tamppari, L. K.; Smith, P.; Stoker, C.; Tamppari, L.; Wood, S. U.; Young, S. M.; Zent, A.; Fisher, D.

2008-12-01

104

The unexpectedly high solubility of water in cryogenic liquids  

NASA Astrophysics Data System (ADS)

A high solubility for H2O in liquid nitrogen (LIN), LOX, and liquid methane (LIM) is demonstrated using Fourier transform IR spectroscopy. The trials were conducted with a vacuum insulated absorption cell made of brass. Ice particles were stirred into the LIN before transferrence to the cell, where the saturation was determined to depend on the mixing rate. The results were confirmed with the addition of D2O instead of H2O. It was also found that samples of LIN, LOX, and LIM exposed to the atmosphere displayed a significant uptake of water vapor. The LOX nu-1 and nu-2 lines were doublets with time and temperature varying intensities, which indicates that the doublets originate from dimer and monomer water. The results of the tests are useful for handling and storage of cryogenic liquids and biological specimens immersed in cryogenic liquids.

Rebiai, R.; Rest, A. J.; Scurlock, R. G.

1983-09-01

105

Ion Transport through a Water-Organic Solvent Liquid-Liquid Interface: A Simulation Study.  

PubMed

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

Holmberg, Nico; Sammalkorpi, Maria; Laasonen, Kari

2014-06-01

106

Ship-based liquid water path estimates in marine stratocumulus  

Microsoft Academic Search

We examine liquid water paths (LWPs) derived from ship-based microwave radiometer brightness temperature (Tb) measurements collected within southeastern Pacific stratocumulus at 20°S, 85°W in October 2001. The boundary layer was typically well mixed and overcast. Three gaseous absorption models and two liquid dielectric models are evaluated. Total differences in retrieved LWP attributable to microwave absorption model differences are 10–25 g

Paquita Zuidema; Edgeworth R. Westwater; Chris Fairall; Duane Hazen

2005-01-01

107

Ship-based liquid water path estimates in marine stratocumulus  

Microsoft Academic Search

We examine liquid water paths (LWPs) derived from ship-based microwave radiometer brightness temperature (Tb) measurements collected within southeastern Pacific stratocumulus at 20°S, 85°W in October 2001. The boundary layer was typically well mixed and overcast. Three gaseous absorption models and two liquid dielectric models are evaluated. Total differences in retrieved LWP attributable to microwave absorption model differences are 10-25 g

Paquita Zuidema; Edgeworth R. Westwater; Chris Fairall; Duane Hazen

2005-01-01

108

Solid + liquid phase equilibria in the hydroxylammonium nitrate + water system  

Microsoft Academic Search

The binary solid + liquid phase diagram has been measured for the water + hydroxylammonium nitrate (HAN) system. The phase diagram is a simple eutectic type with the eutectic at 231.5 K (41.7°C) and a mole fraction HAN of 0.281 (wt fraction HAN - 0.676).The enthalpy of fusion of the HAN was determined from the solid + liquid results to

Johanne I. Artman; J. Bevan Ott

1989-01-01

109

Metastability of Liquid Water on Mars  

NASA Technical Reports Server (NTRS)

This talk reviews reasonable spatial and temporal scales for melting and flowing of water on Mars, and relates them to plausible martian conditions. Additional information is contained in the original extended abstract.

Hecht, M. H.

2001-01-01

110

Liquid Water Production from Atmospheric Sources.  

National Technical Information Service (NTIS)

The purpose of this effort was to assess the feasibility of developing a desiccant system to produce potable water from atmospheric sources that is compatible with military constraints. Goals were: (1) to examine desiccant technology, investigate methods ...

J. D. Matthews N. P. Clarke

1991-01-01

111

Molecular Dynamics Study of Liquid Water  

Microsoft Academic Search

A sample of water, consisting of 216 rigid molecules at mass density 1 gm\\/cm3, has been simulated by computer using the molecular dynamics technique. The system evolves in time by the laws of classical dynamics, subject to an effective pair potential that incorporates the principal structural effects of many-body interactions in real water. Both static structural properties and the kinetic

Aneesur Rahman; Frank H. Stillinger

1971-01-01

112

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 (54.5°S; 12.7°E) and in Kaiser crater (46.2°S; 19.1°E) 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

113

Homogeneous liquid-liquid solvent extraction. [Propylene carbonate-water system  

Microsoft Academic Search

This investigation was undertaken to extend the technique of homogeneous liquid-liquid solvent extraction into propylene carbonate. The mutual solubilities of propylene carbonate in water and vice-versa are shown in the phase diagram. The extraction of a variety of monodentate and bidentate ligand complexes with Fe(III) as a function of ligand concentration and pH were investigated. The monodentate ligands studied include,

C. S. Ting; E. T. Williams; H. L. Finston

1980-01-01

114

Determination of organic compounds in water using dispersive liquid–liquid microextraction  

Microsoft Academic Search

A new microextraction technique termed dispersive liquid–liquid microextraction (DLLME) was developed. DLLME is a very simple and rapid method for extraction and preconcentration of organic compounds from water samples. In this method, the appropriate mixture of extraction solvent (8.0?L C2Cl4) and disperser solvent (1.00mL acetone) are injected into the aqueous sample (5.00mL) by syringe, rapidly. Therefore, cloudy solution is formed.

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

2006-01-01

115

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

116

Electron energy loss in liquid water  

NASA Astrophysics Data System (ADS)

The indirect effects of ionizing radiation is a major side effect in radiotherapy. The knowledge of the amount of energy deposited by electrons in the tissues is important to assure the right dose to be delivered to a patient. The lack of experimental data on the energy loss of electrons in water, with energies in the same range of the secondary electrons emitted in the interaction of radiation with tissues, renders difficult the evaluation of the real total dose released to the patient. In this work we present a method to obtain the electron energy loss from the measured fragmentation cross section of water by electron impact.

Tavares, André C.; Montenegro, E. C.

2012-11-01

117

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

Microsoft Academic Search

In this paper, a two phase model to compute liquid-liquid flows is presented. We consider that one phase is a highly viscous thermodependent liquid (polymer phase), whereas the second one is a low viscosity low temperature fluid (water). The first part of this paper concerns capture of the interface between the water and the polymer (or determination of the phase

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

2007-01-01

118

On the Stability of Liquid Water on Present Day Mars  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

119

On the Fluctuations that Order and Frustrate Liquid Water  

NASA Astrophysics Data System (ADS)

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

Limmer, David Tyler

120

Prediction of liquid-liquid equilibria. [4 alcohol/water/n-alkane systems; 3 ketone/water/n-alkane systems; 4 alcohol/ketone/water systems  

SciTech Connect

The use of a group-contribution molecular model for the prediction of liquid-liquid equilibria in alcohol/fuel blends in contact with water has been investigated. The group contribution technique is UNIFAC. The UNIFAC method is compared to 3 other molecular thermodynamic solution theories for 11 ternary liquid-liquid systems. These 11 systems were chosen to simulate alcohol/water/fuel blends. The group contribution technique predicted the experimental solubilities with an average error of slightly more than 2%. 15 references, 1 figure, 5 tables.

Arnold, D.W.; Yu, C.Y.

1982-01-01

121

Photochemical water oxidation by crystalline polymorphs of manganese oxides: structural requirements for catalysis.  

PubMed

Manganese oxides occur naturally as minerals in at least 30 different crystal structures, providing a rigorous test system to explore the significance of atomic positions on the catalytic efficiency of water oxidation. In this study, we chose to systematically compare eight synthetic oxide structures containing Mn(III) and Mn(IV) only, with particular emphasis on the five known structural polymorphs of MnO2. We have adapted literature synthesis methods to obtain pure polymorphs and validated their homogeneity and crystallinity by powder X-ray diffraction and both transmission and scanning electron microscopies. Measurement of water oxidation rate by oxygen evolution in aqueous solution was conducted with dispersed nanoparticulate manganese oxides and a standard ruthenium dye photo-oxidant system. No Ru was absorbed on the catalyst surface as observed by XPS and EDX. The post reaction atomic structure was completely preserved with no amorphization, as observed by HRTEM. Catalytic activities, normalized to surface area (BET), decrease in the series Mn2O3 > Mn3O4 ? ?-MnO2, where the latter is derived from spinel LiMn2O4 following partial Li(+) removal. No catalytic activity is observed from LiMn2O4 and four of the MnO2 polymorphs, in contrast to some literature reports with polydispersed manganese oxides and electro-deposited films. Catalytic activity within the eight examined Mn oxides was found exclusively for (distorted) cubic phases, Mn2O3 (bixbyite), Mn3O4 (hausmannite), and ?-MnO2 (spinel), all containing Mn(III) possessing longer Mn-O bonds between edge-sharing MnO6 octahedra. Electronically degenerate Mn(III) has antibonding electronic configuration e(g)(1) which imparts lattice distortions due to the Jahn-Teller effect that are hypothesized to contribute to structural flexibility important for catalytic turnover in water oxidation at the surface. PMID:23391134

Robinson, David M; Go, Yong Bok; Mui, Michelle; Gardner, Graeme; Zhang, Zhijuan; Mastrogiovanni, Daniel; Garfunkel, Eric; Li, Jing; Greenblatt, Martha; Dismukes, G Charles

2013-03-01

122

New polymorphic microsatellite loci of threadsail filefish, Stephanolepis cirrhifer (Teleostei, Monacanthidae), from Korean waters.  

PubMed

The threadsail filefish, Stephanolepis cirrhifer (Monacanthidae), is found mainly in the western Pacific. It is intensively caught in Korea and is a highly appreciated seafood delicacy. Consequently, the natural population of this species has drastically decreased, despite introductions from hatcheries. To provide information necessary for its conservation and management, we developed 24 polymorphic microsatellite markers using a combination of a total enriched genomic library and a small-scale 454 pyrosequencing. A total of 90,847 raw reads were obtained, and 75,128 unique sequences were generated, with an average length of 477 bp; 5350 (7.12%) sequences contained a minimum of 5 di- to tetranucleotide repeat motifs. Seventy-four sequences were used for microsatellite primer design. They all amplified successfully; 24 were polymorphic, with 8 containing trinucleotide repeats and 3 containing tetranucleotide repeats. The genetic variations based on 15 primer sets were investigated using 45 wild individuals from the coastal waters of Geomun Island. The number of alleles per locus varied from 4 to 15, with an average of 7.47. The observed and expected heterozygosities ranged from 0.333 to 0.956 and from 0.316 to 0.870, with averages of 0.692 and 0.701, respectively. No linkage disequilibrium was found between any pair of loci, indicating their independence. One locus significantly deviated from Hardy-Weinberg equilibrium after Bonferroni's correction; this may be due to the existence of a null allele. Cross-amplification was also tested for all 24 polymorphic loci in another monacanthid species, Thamnaconus modestus; 7 loci were effectively amplified. The high degree of polymorphism that was exhibited by the 15 newly developed microsatellites will be useful for assessing genetic variation and for conservation genetic studies of these 2 monacanthid species. PMID:23765974

An, C-M; An, H S; Lee, J W; Hong, S W

2013-01-01

123

Fluctuating selection by water level on gynoecium colour polymorphism in an aquatic plant  

PubMed Central

Background and Aims It has been proposed that variation in pollinator preferences or a fluctuating environment can act to maintain flower colour polymorphism. These two hypotheses were tested in an aquatic monocot Butomus umbellatus (Butomaceae) with a pink or white gynoecium in the field population. Methods Pollinator visitation was compared in experimental arrays of equivalent flowering cymes from both colour morphs. Seed set was compared between inter- and intramorph pollination under different water levels to test the effect of fluctuating environment on seed fertility. Key Results Overall, the major pollinator groups did not discriminate between colour morphs. Compared with the white morph, seed production in the pink morph under intermorph, intramorph and open pollination treatments was significantly higher when the water level was low but not when it was high. Precipitation in July was correlated with yearly seed production in the pink morph but not in the white morph. Conclusions The results indicated that the two colour morphs differed in their tolerance to water level. Our study on this aquatic plant provides additional evidence to support the hypothesis that flower colour polymorphism can be preserved by environmental heterogeneity.

Tang, Xiao-Xin; Huang, Shuang-Quan

2010-01-01

124

Effect of Molecular Structure on Mesomorphism.4. Factors Governing Polymorphism of Smectic Liquid Crystals  

Microsoft Academic Search

A three-dimensional energy surface is proposed as a model to account for smectic polymorphism. This model allows interplay between the two factors relating to phase transformations: (1) thermodynamic stabilities of the phases and (2) accessibility of a phase from the preceding phase. Experimental observations are rationalized using this model and predictions are made based on it.

Anselm C. Griffin

1976-01-01

125

Statistical physics and liquid water at negative pressures  

Microsoft Academic Search

Angell and his collaborators have underscored the importance of studying water under all extremes of pressure—squeezing to high pressures and stretching to negative pressures. Here we review recent results of molecular dynamics simulations of two models of liquid water, the extended simple point charge (SPC\\/E) and the Mahoney-Jorgensen transferable intermolecular potential with five points (TIP5P), which is closer to real

H. Eugene Stanley; M. C Barbosa; S. Mossa; P. A Netz; F. Sciortino; F. W Starr; M. Yamada

2002-01-01

126

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

127

Physical and Thermodynamical Evidence of Liquid Water on Mars  

NASA Astrophysics Data System (ADS)

We show evidence that liquid saline-water currently exists on Mars. Moreover, we show that the thermodynamics of freezing/thaw cycles leads to the formation of saline solutions with freezing temperatures much higher than currently found on most of Mars.

Renno, N. O.; Clark, B. C.; Drube, L.; Fisher, D.; Goetz, W.; Hecht, M.; Keller, H. U.; Kounaves, S.; Lemmon, M.; Madsen, M. B.; Marshall, J.; Mehta, M.; Mellon, M.; Smith, M.; Smith, P. H.; Stoker, C.; Tamppari, L.; Wood, S.; Young, S. M.; Zent, Z.

2008-11-01

128

Stratocumulus Liquid Water Content from Dual-Wavelength Radar  

Microsoft Academic Search

A technique is described to retrieve stratocumulus liquid water content (LWC) using the differential attenuation measured by vertically pointing radars at 35 GHz and 94 GHz. Millimeter-wave attenuation is proportional to LWC and increases with frequency, so LWC can be derived without the need to make any assumptions on the nature of the droplet size distribution. There is also no

ROBIN J. HOGAN; NICOLAS GAUSSIAT; ANTHONY J. ILLINGWORTH

2004-01-01

129

Molecular dynamics simulation of liquid water: Hybrid density functionals  

SciTech Connect

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

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

2005-09-12

130

Geminate recombination of quasi-free electrons in liquid water  

Microsoft Academic Search

The mechanism of geminate recombination of quasi-free electrons in liquid water was considered. The recombination occurs at electrostatic disequilibrium and the recombination time is comparable with the time of electrostatic polarization of the medium. The major contribution to the recombination is made by ion pairs that are formed via direct ionization rather than autoionization. The mechanism of formation of hydrogen

Sukhonosov

1995-01-01

131

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

132

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

133

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

134

Isobaric vapor–liquid equilibria of water–pyridine and water–pyridine–calcium chloride mixtures  

Microsoft Academic Search

Isobaric vapor–liquid equilibrium data at 705±1mmHg for the systems water–pyridine and water–pyridine–CaCl2 were obtained using the modified Othmer circulation still. The experimental data for the water–pyridine system exhibited an azeotropic point at a water composition of 75.0mol% and a temperature of 92.60°C. The isobaric salt-free binary data were compared with predicted vapor–liquid equilibrium (VLE) data using the UNIFAC model. Good

Fahmi A Abu Al-Rub; Ravindra Datta

2001-01-01

135

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

136

Isothermal--isobaric molecular dynamics simulation of liquid water  

SciTech Connect

Results of the first isothermal--isobaric molecular dynamics simulation of water are reported. Water molecules are assumed to be flexible and to interact via a sum of pairwise interatomic potentials. Extensive runs for 256 molecules at 298 and 373 K and 1 bar give satisfactory agreement with observed properties of liquid water as diverse as density, internal energy, heat capacity, compressibility, pair correlation functions, diffusion coefficient, vibrational spectrum, relative permittivity, and dielectric relaxation spectra. The nonlinear dependence of the relative permittivity on the electric field is also computed by means of fluctuation--dissipation relations.

Ruff, I.; Diestler, D.J. (Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (USA))

1990-08-01

137

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

138

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

PubMed

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

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

2014-06-01

139

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

140

Diffusion-controlled and "diffusionless" crystal growth near the glass transition temperature: relation between liquid dynamics and growth kinetics of seven ROY polymorphs.  

PubMed

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 alpha relaxation process has time-temperature superposition symmetry across the viscous range (tau(alpha)=100 s-100 ns) with the width of the relaxation peak characterized by a constant beta(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 tau(alpha), u proportional to tau(alpha)(-xi), where xi approximately = 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 T(g) 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. PMID:19708750

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

2009-08-21

141

Human salivary acidic proline-rich protein polymorphisms and biosynthesis studied by high-performance liquid chromatography.  

PubMed

Human salivary acidic proline-rich proteins (PRPs) constitute a significant fraction of the total salivary protein and possess important biological activities. Different genetic and post-translationally processed forms of the PRPs exhibit significant quantitative variations in several of these activities, especially the modulation of salivary calcium phosphate chemistry and oral bacterial adhesion. To quantify and understand these differences, we have developed a high-performance liquid chromatography (HPLC) method to identify and measure individual PRPs in saliva. The data obtained permit the identification of PRP polymorphisms and phenotypes, the determination of the relative amounts of PRPs derived from the two loci, PRH1 and PRH2, and the measurement of the extent of post-translational cleavage of the primary polypeptide products. Substantial inter-gland and inter-individual variations were found in relative amounts of PRPs derived from the two loci (at least two-fold), and in post-translational cleavage (greater than two-fold), both of which are likely to be biologically significant. Also in this study, the presence of what appear to be minor amounts of numerous variant PRPs in glandular secretions was observed, and two uncommon PRP polymorphisms were identified in the 127 subjects studied. PMID:7983258

Hay, D I; Ahern, J M; Schluckebier, S K; Schlesinger, D H

1994-11-01

142

Measurements and modeling of quaternary (liquid + liquid) equilibria for mixtures of (methanol or ethanol + water + toluene + n-dodecane)  

Microsoft Academic Search

The extraction of aromatic compound toluene from alkane, dodecane, by mixed solvents (water+methanol), (water+ethanol) and (methanol+ethanol) have been studied by (liquid+liquid) equilibrium (LLE) measurements at three temperatures (298.15, 303.15, and 313.15) K and ambient pressure. The compositions of liquid phases at equilibrium were determined by gas liquid chromatography.The experimental tie-line data for three quaternary mixtures of {(water+methanol)+toluene+dodecane}, {(water+ethanol)+toluene+dodecane}, and {(methanol+ethanol)+toluene+dodecane}

F. S. Mohammad Doulabi; M. Mohsen-Nia; H. Modarress

2006-01-01

143

Recommended Liquid-Liquid Equilibrium Data. Part 5. Ether-Water Systems  

NASA Astrophysics Data System (ADS)

Recommended liquid-liquid equilibrium (LLE) data for 12 binary ether-water systems have been obtained after the critical evaluation of all data (168 data sets) reported for 17 systems in the open literature up to the end of 2006. An equation for the prediction of the ether solubilities in water was developed. The predicted ether solubilities were used for the calculation of water solubility in the ether-rich phase. The LLE calculations were done with the equation of state appended with a chemical term (EoSC) proposed by Góral [Fluid Phase Equilib. 118, 27 (1996)]. The recommended data are presented in the form of individual tables with references. Using these recommended data, predictive ability has been tested for several UNIFAC and ASOG group-contribution methods.

Góral, Marian; MaCzy?ski, Andrzej; Oracz, Pawe?

2007-12-01

144

Isobaric vapor–liquid–liquid equilibrium and vapor–liquid equilibrium for the system water–ethanol-1,4-dimethylbenzene at 101.3 kPa  

Microsoft Academic Search

An all-glass, dynamic recirculating still equipped with an ultrasonic homogenizer has been used to determine vapor–liquid (VLE) and vapor–liquid–liquid (VLLE) equilibria. Consistent data have been obtained for the ternary water+ethanol+p-xylene system at 101.3kPa for temperatures in the range of 351.16–365.40K. Experimental results have been used to check the accuracy of the UNIFAC, UNIQUAC and NRTL models in the liquid–liquid region

Vicente Gomis; Ana Pequenín; Juan Carlos Asensi

2009-01-01

145

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

146

Liquid water transport in polylactide homo and graft copolymers.  

PubMed

The successful design of new biodegradable, renewable resource plastics as replacements to commodity barrier plastics would benefit from an accurate measurement of sorption and diffusion of liquids. In this study, the diffusion of liquid water in amorphous polylactide [PLA] and a PLA graft copolymer, poly(1,5-cyclooctadiene-co-5-norbornene-2-methanol-graft-dl-lactide) [PCNL], was examined with time-resolved Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior was observed for all experiments, indicated by a slow approach to steady state due to diffusion and polymer relaxation occurring on similar time scales. This non-Fickian behavior highlights the variability of the sorption isotherms reported in the literature, where others have collected nonequilibrium sorption behavior (instead of true steady-state equilibrium sorption) at different time points and film thicknesses. The dynamic infrared data provided direct evidence for both water diffusion and water-induced polymer relaxation, where both were quantified and regressed to a diffusion-relaxation model to determine the diffusion coefficient and the polymer relaxation time constant. In addition to the successful measurement and modeling of the diffusion-relaxation phenomena for diffusion of a liquid in a nonequilibrium state glassy polymer, this study also determined that the diffusivity of water in the PLA graft copolymer (with only 5 wt % rubber) was 3-fold lower than in the PLA homopolymer. PMID:21888318

Davis, Eric M; Theryo, Grayce; Hillmyer, Marc A; Cairncross, Richard A; Elabd, Yossef A

2011-10-01

147

Stability of tetracycline in water and liquid manure.  

PubMed

The objective of this study was to establish a suitable model for the prediction of the environmental stability of antibiotics in water and liquid manure. The model consists of incubation systems for solutions with installations for stirring ventilation. It was used to examine the stability of tetracycline in ventilated and unventilated Ringer's solution and liquid pig manure for a period of 8 days. Tetracycline concentrations decreased significantly during the experiment. The fastest degradation was observed in ventilated liquid manure. The test might be used as a screening test for the determination of the degradation half-life of antibiotics in the first phase of an environmental safety study according to directive 92/18/EEC. PMID:11008446

Kühne, M; Ihnen, D; Möller, G; Agthe, O

2000-08-01

148

(Liquid + liquid) equilibria of (water + propionic acid + diethyl phthalate) at several temperatures  

Microsoft Academic Search

(Liquid+liquid) equilibrium (LLE) data for (water+propionic acid+diethyl phthalate) were measured under atmospheric pressure and at T=(298.2, 303.2, 308.2, and 313.2)K. Phase diagrams were obtained by determining solubility and tie-line data. The UNIFAC model was used to correlate the experimental tie-line data. The average root-mean-square deviation between the observed and calculated mass fraction was 0.03. Distribution coefficients and separation factors were

Süheyla Çehreli; Dilek Özmen; Be?ir Tatl?

2005-01-01

149

A physically-based retrieval of cloud liquid water from SSM/I measurements  

NASA Technical Reports Server (NTRS)

A simple physical scheme is proposed for retrieving cloud liquid water over the ice-free global oceans from Special Sensor Microwave/Imager (SSM/I) observations. Details of the microwave retrieval scheme are discussed, and the microwave-derived liquid water amounts are compared with the ground radiometer and AVHRR-derived liquid water for stratocumulus clouds off the coast of California. Global distributions of the liquid water path derived by the method proposed here are presented.

Greenwald, Thomas J.; Stephens, Graeme L.; Vonder Haar, Thomas H.

1992-01-01

150

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

151

Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water  

NASA Astrophysics Data System (ADS)

Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of the SRS, it is suggested that the excess electrons, which are generated in a few picoseconds before the phase transition, play an important role in the transient SRS enhancement through the change of the nonlinear polarizability induced around the electrons in liquid water. Several applications of the enhanced vibrational spectra in the OH stretching vibrational region to the spectroscopic analyses of local water structures in various environments are also described.

Yui, Hiroharu; Sawada, Tsuguo

2003-01-01

152

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

153

Temporal and spatial relationships between topography, atmospheric water vapor, liquid water and vegetation endmember fractions determined using AVIRIS  

Microsoft Academic Search

Temporal and spatial changes in water vapor, liquid water and endmember fractions were investigated using AVIRIS data collected in the vicinity of Jasper Ridge, CA, on three dates in 1992. Water vapor and liquid water were mapped using a Modtran-II based atmospheric model that accounts for spatially varying atmospheric properties. Spectral mixture analysis (SMA) was used to model vegetation as

D. A. Roberts; R. O. Green; J. B. Adams; J. S. Cothern; D. E. Sabol; M. O. Smith

1994-01-01

154

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

155

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

156

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

157

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

158

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

159

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

PubMed Central

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

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

2013-01-01

160

Liquid water: from symmetry distortions to diffusive motion.  

PubMed

Water deviates from tetrahedral symmetry on different scales, creating "defects" that are important for its dynamics. In this Account, I trace the manifestations of these distortions from the isolated molecule through gas-phase clusters to the liquid phase. Unlike the common depiction, an isolated water molecule has a nonsymmetric charge distribution: although its positive charge is localized at the hydrogens, the negative charge is smeared between the lone-pair sites. This creates a "negativity track" along which a positive charge may slide. Consequently, the most facile motion within the water dimer is a reorientation of the hydrogen-bond (HB) accepting molecule (known as an "acceptor switch"), such that the donor hydrogen switches from one lone pair to the other. Liquid water exhibits asymmetry between donor and acceptor HBs. Molecular dynamics simulations show that the water oxygens accepting HBs from the central molecule are spatially localized, whereas water hydrogens donating HBs to it are distributed along the negativity track. This asymmetry is manifested in a wider acceptor- versus donor-HB distribution. There is a higher probability for a water molecule to accept one (trigonal symmetry) or three HBs than to donate one or three HBs. A simple model can explain semiquantitatively how these distributions evolve by distorting perfectly tetrahedral water. Just two reactions are required: the dissociation of a HB between a double-donor donating to a double-acceptor, D(2)···A(2), followed by a switching reaction in which a HB donor rotates its hydrogen between two double-acceptor molecules. The preponderance of D(2)···A(2) dissociation events is in line with HB "anticooperativity", whereas positive cooperativity is exhibited by conditional HB distributions: a molecule with more acceptor bonds tends to have more donor bonds and vice versa. Quantum mechanically, such an effect arises from intermolecular charge transfer, but it is observed even for fixed-charge water models. Possibly, in the liquid state this is partly a collective effect, for example, a more ordered hydration shell that enhances the probability for both acceptor and donor HBs. The activation energy for liquid water self-diffusion is considerably larger than its HB strength, pointing to the involvement of collective dynamics. The remarkable agreement between the temperature dependence of the water self-diffusion coefficient and its Debye relaxation time suggests that both share the same mechanism, likely consisting of coupled rotation and translation with collective rearrangement of the environment. The auto-correlation function of a hydrogen-bonded water molecule pair is depicted quantitatively by the solution of the diffusion equation for reversible geminate recombination, up to long times where the ubiquitous t(-3/2) power law prevails. From the model, one obtains the HB dissociation and formation rate coefficients and their temperature dependence. Both have a similar activation enthalpy, suggesting rapid formation of HBs with alternate partners, perhaps by the HB switching reaction involving the trigonal site. A detailed picture of how small fluctuations evolve into large-scale molecular motions in water remains elusive. Nonetheless, our results demonstrate how the plasticity of water can be traced to its asymmetric charge distribution, with duality between tetrahedral and trigonal ligation states. PMID:21978022

Agmon, Noam

2012-01-17

161

Liquid Water Simulations with Density Fragment Interaction Approach  

PubMed Central

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

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

2013-01-01

162

Thermodynamic study of solutions of liquid hydrocarbon mixtures in water  

SciTech Connect

The hydrocarbon solution process in water was studied because it is important in environmental and geological situations. The aqueous solubility of binary hydrocarbon mixtures was determined (n-octane + 1-methylnaphthalene at 20 and 70/sup 0/C; n-octane + ethylbenzene at 20/sup 0/C and tetralin + methylcyclohexane at 20/sup 0/C). Vapor-liquid equilibrium hydrocarbon phase activity coefficients for the above mixtures were also determined. Hydrocarbon activity coefficients in the aqueous phase were found not to be measurably reduced in the presence of hydrocarbon co-solutes, in contradiction to the conclusions of Leinonen and MacKay (1973) and Leinonen (1976). This indicates that the effects of aqueous phase solute-solute interactions can not be determined within the precision of water solubility measurements. The presence of a substantial amount of water in the liquid hydrocarbon phase at 70/sup 0/C did not significantly affect the hydrocarbon activity coefficients in the hydrocarbon phase. Activity coefficients estimated by the UNIFAC group-contribution method indicate that water in the hydrocarbon phase may not significantly affect hydrocarbon phase activity coefficients up to 150/sup 0/C.

Burris, D.R.; MacIntyre, W.G.

1986-07-01

163

Ab initio liquid water from PBE0 hybrid functional simulations  

NASA Astrophysics Data System (ADS)

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

Li, Zhaofeng; Wu, Xifan; Car, Roberto

2010-03-01

164

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

PubMed

In plants, adaptive-compensatory responses to stress always entail additional energy expenditure. A suggestion was brought forward that in plants growing under conditions of water stress there is a relationship between genetic variability of respiratory enzymes and their functional significance. With Kochia prostrate (L.) Schrad. as a case study, intraspecies genetic polymorphism under the conditions of drought has been analyzed using typical protein markers which, considering their functional importance, can be viewed as respiratory enzymes. Out of eight protein markers examined, four enzymes were singled out for which dominating combination of genotypes Dia B (a), G6pd (a), Gdh (c), and Mdh A (a) was incidental. In all populations from arid and semiarid zone, these genotypes frequency of occurrence was in the range of 0.53-1.0, i.e., it comprised more than 50% of the whole variety of combinations. Thus, it seems plausible that this combination of genotypes can be an "adaptive collection" for K. prostrata populations growing in arid habitats. A characteristic feature of the picked out enzymes is their belonging to NAD(P)(+)-depending oxidoreductases that play a key role in functioning and redox-regulation of respiratory metabolism in course of adapting to water deficiency. It is suggested that the presence of such well-balanced co-adaptive genotype combinations, that provide enzymes important in terms of energetics, determine the formation of energetic and redox-balances during the process of adaptation to water stress. PMID:24163981

Rakhmankulova, Z F; Shu?skaia, E V; Rogozhnikova, E S

2013-01-01

165

Fractionation of sugar cane with hot, compressed, liquid water  

SciTech Connect

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

Allen, S.G.; Kam, L.C.; Zemann, A.J.; Antal, M.J. Jr. [Univ. of Hawaii, Honolulu, HI (United States)] [Univ. of Hawaii, Honolulu, HI (United States)

1996-08-01

166

Occurrence, liquid water content, and fraction of supercooled water clouds from combined CALIOP/IIR/MODIS measurements  

NASA Astrophysics Data System (ADS)

The CALIOP depolarization measurements, combined with backscatter intensity measurements, are effective in discriminating between water clouds and ice clouds. The same depolarization measurements can also be used for estimating liquid water content information. Using cloud temperature information from the collocated infrared imaging radiometer measurements and cloud water paths from collocated MODIS measurements, this study compiles global statistics of the occurrence frequency, liquid water content, liquid water path, and their temperature dependence. For clouds with temperatures between -40°C and 0°C, the liquid phase fractions and liquid water paths are significantly higher than the ones from previous studies using passive remote sensing measurements. At midlatitudes, the occurrence of liquid phase clouds at temperatures between -40°C and 0°C depends jointly on both cloud height and cloud temperature. At high latitudes, more than 95% of low-level clouds with temperatures between -40°C and 0°C are water clouds. Supercooled water clouds are mostly observed over ocean near the storm-track regions and high-latitude regions. Supercooled water clouds over land are observed in the Northern Hemisphere over Europe, East Asia, and North America, and these are the supercooled water clouds with highest liquid water contents. The liquid water content of all supercooled water clouds is characterized by a Gamma (?) distribution. The mode values of liquid water content are around 0.06 g/m3 and are independent of cloud temperature. For temperatures warmer than -15°C, mean value of the liquid water content is around 0.14 g/m3. As the temperature decreases, the mean cloud liquid water content also decreases. These results will benefit cloud models and cloud parameterizations used in climate models in improving their ice-phase microphysics parameterizations and the aviation hazard forecast.

Hu, Yongxiang; Rodier, Sharon; Xu, Kuan-Man; Sun, Wenbo; Huang, Jianping; Lin, Bing; Zhai, Pengwang; Josset, Damien

2010-01-01

167

Shock wave initiated by an ion passing through liquid water  

SciTech Connect

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

Surdutovich, Eugene [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany); Department of Physics, Oakland University, Rochester, Michigan 48309 (United States); Solov'yov, Andrey V. [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany)

2010-11-15

168

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

169

Thermodynamic properties of liquid water from a polarizable intermolecular potential.  

PubMed

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. PMID:23387601

Yigzawe, Tesfaye M; Sadus, Richard J

2013-01-28

170

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

Microsoft Academic Search

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

Kiyofumi Kurihara; Mikiyoshi Nakamichi; Kazuo Kojima

1993-01-01

171

Negative pressure of stretched liquid water. Geochemistry of soil capillaries  

NASA Astrophysics Data System (ADS)

Solution-mineral equilibria in the unsaturated zone above aquifers requires us to take into account the negative internal pressure of liquid water, distributed in fine pores of a partially filled medium. The proposed method affords calculation of the thermodynamic properties of capillary water by extrapolating their dependencies measured at positive pressures, into a negative pressure domain, finding supports from measurements already obtained on the stretched water. Besides Gibbs free energy, enthalpy, entropy, heat capacity, isobaric expansibility and isothermal compressibility of soil water, calculations of the dielectric constant, the water-air interfacial tension and the pH at neutrality have been established. This thermodynamic characterization of the water state in soils enables us to consider quantitatively the melting and boiling temperatures in soils or in fluid inclusions, the corresponding latent heat, or the lowering of the saturated vapour pressure in the unsaturated zone of weathering profiles. This pressure approach implies some reviewed consequences about solute species, gases and mineral solubilities, or still hydration-dehydration phenomena, in capillaries.

Mercury, Lionel; Tardy, Yves

2001-10-01

172

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

173

Liquid/liquid metal extraction: Phase diagram topology resulting from molecular interactions between extractant, ion, oil and water  

NASA Astrophysics Data System (ADS)

We consider the class of surfactants called "extractants" since they specifically interact with some cations and are used in liquid-liquid separation processes. We review here features of water-poor reverse micelles in water/oil/ extractant systems as determined by combined structural studies including small angle scattering techniques on absolute scale. Origins of instabilities, liquid-liquid separation as well as emulsification failure are detected. Phase diagrams contain the same multi-phase domains as classical microemulsions, but special unusual features appear due to the high spontaneous curvature directed towards the polar cores of aggregates as well as rigidity of the film made by extracting molecules.

Bauer, C.; Bauduin, P.; Dufrêche, J. F.; Zemb, T.; Diat, O.

2012-11-01

174

Quantum diffusion in liquid water from ring polymer molecular dynamics.  

PubMed

We have used the ring polymer molecular-dynamics method to study the translational and orientational motions in an extended simple point charge model of liquid water under ambient conditions. We find, in agreement with previous studies, that quantum-mechanical effects increase the self-diffusion coefficient D and decrease the relaxation times around the principal axes of the water molecule by a factor of around 1.5. These results are consistent with a simple Stokes-Einstein picture of the molecular motion and suggest that the main effect of the quantum fluctuations is to decrease the viscosity of the liquid by about a third. We then go on to consider the system-size scaling of the calculated self-diffusion coefficient and show that an appropriate extrapolation to the limit of infinite system size increases D by a further factor of around 1.3 over the value obtained from a simulation of a system containing 216 water molecules. These findings are discussed in light of the widespread use of classical molecular-dynamics simulations of this sort of size to model the dynamics of aqueous systems. PMID:16252959

Miller, Thomas F; Manolopoulos, David E

2005-10-15

175

Learning science through guided discovery: liquid water and molecular networks  

NASA Astrophysics Data System (ADS)

In every drop of water, down at the scale of atoms and molecules, there is a world that can fascinate anyone. The objective of “Learning science through guided discovery: liquid water and molecular networks” is to use advanced technology to provide a window into the submicroscopic, and thereby allow students to discover by themselves an entire new world. We are developing a coordinated two-fold approach to high school science teaching in which a cycle of hands-on activities, games, and experimentation is followed by a cycle of computer simulations employing the full power of computer animation to “ZOOM” into the depths of this newly discovered world. Pairing of laboratory experiments with corresponding simulations challenges students to understand multiple representations of concepts. We thereby provide students with the opportunity to work in a fashion analogous to that in which practicing scientists work - e.g., by “building up” to general principles from specific experiences. Moreover, the ability to visualize “real-time” dynamic motions allows for student-controlled graphic simulations on the molecular scale, and interactive guided lessons superior to those afforded by even the most artful of texts. While our general approach could be applied to a variety of topics, we have chosen to focus first on the most familiar of molecular networks, that of liquid water. Later we will test the generality of the approach by exploring macromolecules such as proteins and DNA.

Ostrovsky, Boris; Poole, Peter H.; Sciortino, Francesco; Eugene Stanley, H.; Trunfio, Paul

1991-09-01

176

Cloud and rain liquid water statistics in the CHUVA campaign  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

177

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

PubMed

A new method for the determination of trace lead was developed by dispersive liquid-liquid microextraction preconcentration and graphite furnace atomic absorption spectrometry. In the proposed approach, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was used as a chelating agent, and carbon tetrachloride and ethanol were selected as extraction and dispersive solvents. Some factors influencing the extraction efficiency of lead and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent, and extraction time, were studied and optimized. Under the optimum conditions, the enrichment factor of this method for lead was reached at 78. The detection limit for lead was 39 ng L(-1) (3 sigma), and the relative standard deviation (RSD) was 3.2% (n=7, c=10 ng mL(-1)). The method was successfully applied to the determination of trace amounts of lead in human urine and water samples. PMID:18539126

Liang, Pei; Sang, Hongbo

2008-09-01

178

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

179

Liquid-liquid equilibria of the ternary system water + acetic acid + 2-methyl-2-butanol  

SciTech Connect

Liquid-liquid equilibria for the ternary system water + acetic acid + 2-methyl-2-butanol 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 UJNIFAC 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 UNIFAC model satisfactorily predicted the equilibrium compositions.

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

1996-11-01

180

Effects of the dispersion interaction in liquid water  

NASA Astrophysics Data System (ADS)

The properties of liquid water obtained from molecular simulations using a density functional theory (B3LYP) based force field [O. Akin-Ojo, F. Wang, J. Comput. Chem. 32 (2011) 453.] with and without an intermolecular dispersion interaction term are compared. Although it is small, the dispersion interaction is found to significantly affect some properties such as the density and the heat of vaporization but not others, for example, the atom-atom radial distribution functions and the infrared spectra. The inclusion of the dispersion interaction in the force field produces an increase in the computed self diffusivity comparable to that resulting from a ˜5 K rise in temperature.

Akin-Ojo, Omololu; Wang, Feng

2011-09-01

181

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

PubMed Central

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

Bai, Jaeil; Zeng, Xiao Cheng

2012-01-01

182

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

PubMed

A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I-ice XIV) and at least 3 glassy forms of water, namely, low-density amorphous, high-density amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7-9 Å apart, numerous bilayer (BL) ices (or polymorphs) can arise [e.g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on graphene/Pt(111) substrate has been achieved experimentally. Herein, we report computer simulation evidence of pressure-induced amorphization from BL-ice I to BL-amorphous and then to BL-VHDA(2) at 250 K and 3 GPa. In particular, BL-VHDA(2) can transform into BL-VHDA(1) via decompression from 3 to 1.5 GPa at 250 K. This phenomenon of 2D polyamorphic transition is akin to the pressure-induced amorphization in 3D ice (e.g., from hexagonal ice to HDA and then to VHDA via isobaric annealing). Moreover, when the BL-ice I is compressed instantly to 6 GPa, a new very-high-density BL ice is formed. This new phase of BL ice can be viewed as an array of square ice nanotubes. Insights obtained from pressure-induced amorphization and crystallization of confined water offer a guide with which to seek a thermodynamic path to grow a new form of methane clathrate whose BL ice framework exhibits the Archimedean 4?8(2) (square-octagon) pattern. PMID:23236178

Bai, Jaeil; Zeng, Xiao Cheng

2012-12-26

183

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

184

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

PubMed

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

Zhang, Ming; Geng, Ying; Xiang, Bingren

2011-01-01

185

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

PubMed Central

Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT.

Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

2012-01-01

186

Solute Isotope Fractionation by Diffusion in Liquid Water  

NASA Astrophysics Data System (ADS)

In natural systems where molecular diffusion plays an important role, isotope distributions can be highly sensitive to the mass dependence of solute diffusion coefficients (D) in liquid water. Isotope geochemistry studies routinely assume that this mass-dependence (heretofore essentially unknown) either is negligible (as predicted by hydrodynamic theories) or follows a kinetic-theory-like inverse square root relation. However, experiments and molecular dynamics (MD) simulations show that the mass-dependence of D is intermediate between these hydrodynamic and kinetic theory predictions for alkali metals, alkaline earth metals, halides, and noble gases (Richter et al., 2006; Bourg and Sposito, 2007, 2008; Bourg et al., 2009). In this talk, we present a general description of the influence of solute valence and radius on the mass-dependence of D for mono-atomic solutes in liquid water. We explain the molecular-scale origin of this mass-dependence and highlight its applications in geochemistry and groundwater hydrology. Bourg I.C., and Sposito G. (2007) Geochim. Cosmochim. Acta 71, 5583-5589. Bourg I.C., and Sposito G. (2008) Geochim. Cosmochim. Acta 72, 2237-2247. Bourg I.C., Richter F.M., et al. (2009) Geochim. Cosmochim. Acta, in preparation. Richter F.M., Mendybaev R.A., et al. (2006) Geochim. Cosmochim. Acta 70, 277-289.

Bourg, I. C.; Sposito, G.

2009-12-01

187

Capability ofBhaskara SAMIR to distinguish atmospheric water vapour and liquid water contents  

NASA Astrophysics Data System (ADS)

An environmental model to compute microwave brightness temperatures for downward looking radiometers on board satellite is described. The effects of water vapour, oxygen and clouds on the brightness temperature have been studied for frequencies from 5 to 50 GHz for a standard tropical atmosphere. The effect of look angle on brightness temperture has also been investigated. Based on the model it has been shown that while the radiometers on board Bhaskara at 19.35 and 22.235 GHz are capable of giving the atmospheric water vapour and liquid water contents, the ability to distinguish these quantities is more for the combination of the frequencies 22.235 and 31 GHz.

Pandey, P. C.; Sharma, A. K.; Gohil, B. S.

1980-07-01

188

Effective liquid–liquid extraction method for analysis of pyrethroid and phenylpyrazole pesticides in emulsion-prone surface water samples  

Microsoft Academic Search

The distribution of pyrethroid and phenylpyrazole pesticides in the water environment has raised public concerns because of their potential risks to ecosystem and human health. However, co-extraction of emulsifier type compounds (by liquid–liquid extraction, LLE) present in environmental samples can present a challenge for quantifying typically low concentrations of pesticides. Several methods were evaluated for breaking emulsions in problematic environmental

Jun Wu; Jian Lu; Chris Wilson; Youjian Lin; Hai Lu

2010-01-01

189

Liquid state theories for the structure of water  

NASA Astrophysics Data System (ADS)

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 (RISM) and the diagrammatically proper Chandler-Silbey-Ladanyi (CSL) theory, are tested by comparison with simulations of the MSPC model (neither theory converges for the SPC model when the hypernetted chain closure is used). The RISM theory is in reasonable agreement with simulations, and is more accurate than the CSL theory. A density functional theory (DFT) is investigated, which treats the ideal gas functional exactly and uses a truncated expansion for the excess free energy functional. The DFT is in excellent agreement with simulations for the structure of the MSPC water model at all temperatures studied, and for the structure of the SPC water model at high temperatures. At room temperature, the DFT is in good agreement with simulations (of SPC water) for gHH(r) and gOH(r), but misses the location of the second peak in gOO(r). We attribute this deficiency to the importance of three-body correlations that are not properly incorporated in the theory.

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

2003-12-01

190

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

191

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

192

NOTE: Cryovolcanism and the Recent Flow of Liquid Water on Mars  

Microsoft Academic Search

The surface of Mars is too cold and dry to permit stable liquid water, yet fresh, apparently water-carved gullies and seepage features have been identified in high-resolution imaging of canyon and crater walls by the Mars Global Surveyor spacecraft. Here, a model of nonequilibrium hydrological activity and liquid water cryovolcanism explains the paradoxical appearance and observed properties of these landforms:

Eric J. Gaidos

2001-01-01

193

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...

194

Atom Pair Distribution Functions of Liquid Water at 25{degrees}C from Neutron Diffraction.  

PubMed

The structure of liquid water is described by three atom pair distribution functions gOO(r), gOH(r), and gHH(r). These functions have now been derived from neutron diffraction data on four mixtures of light and heavy water. They will provide a crucial and sensitive test for proposed models of liquid water. PMID:17839340

Narten, A H; Thiessen, W E; Blum, L

1982-09-10

195

Atom Pair Distribution Functions of Liquid Water at 25circC from Neutron Diffraction  

NASA Astrophysics Data System (ADS)

The structure of liquid water is described by three atom pair distribution functions gOO(r), gOH(r), and gHH(r). These functions have now been derived from neutron diffraction data on four mixtures of light and heavy water. They will provide a crucial and sensitive test for proposed models of liquid water.

Narten, A. H.; Thiessen, W. E.; Blum, L.

1982-09-01

196

Atom Pair Distribution Functions of Liquid Water at 25circC from Neutron Diffraction  

Microsoft Academic Search

The structure of liquid water is described by three atom pair distribution functions gOO(r), gOH(r), and gHH(r). These functions have now been derived from neutron diffraction data on four mixtures of light and heavy water. They will provide a crucial and sensitive test for proposed models of liquid water.

A. H. Narten; W. E. Thiessen; L. Blum

1982-01-01

197

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, Jürg; Okorn, Robert; Eisen, Olaf

2014-05-01

198

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

Microsoft Academic Search

Birefringent spherical vesicles of ritonavir (RTV) are formed by increasing the pH of aqueous solutions from 1 to 3 or to 7 and by addition of water to ethanol solutions at room temperature. Increasing the pH creates supersaturation levels of 30--400. Upon this change in pH, the solutions become translucent, implying that some kind of RTV assembly was formed. Small

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

2009-01-01

199

Relationship between optical extinction and liquid water content in fogs  

NASA Astrophysics Data System (ADS)

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

Klein, C.; Dabas, A.

2014-05-01

200

Liquid-metal/water interactions in a shock tube  

SciTech Connect

To investigate liquid-metal (fuel)/water (coolant) interactions, a vertical shock tube has been designed and constructed. A series of tests was conducted with gallium, indium, lead, and tin as the fuel materials at either low (T{sub f} {approximately} 300 C) or high fuel temperature (T{sub f} {approximately} 600 C), with water at room temperature (low {Tc}) and in the range of T{sub c} = 56 to 67 C (high {Tc}), and with driving pressures from 0.25 to 1.22 MPa. These materials were tested to determine their compatibility for potential use in liquid-metal divertor systems for fusion power plants. The increase in fuel and water temperature, as well as the increase of driving pressure, caused more energetic interactions to occur. High T{sub f} tin and lead interactions, and high T{sub f} and {Tc} gallium and indium interactions were the most energetic. Stronger interactions produced finer debris fragments. In high T{sub f} gallium and indium interactions, small superficial oxidation was observed. For the first two pulses, larger ratios of compression-(compression of expansion vessel gas)to-expansion work correspond to the experiments with higher fuel and coolant temperatures. For the first pulse, only work ratio values of the most energetic experiments are larger than those of isothermal experiments. Consequently, for such experiments, the impulse values of second pulses are the largest. Higher values of the conversion ratio for the first pulse correspond to more energetic interactions. Even for the most energetic experiments, the conversion ratio is no higher than 1.2%, and no more than 15% (or a few millimeters-thick surface layer) of the initially loaded fuel participated in the interaction, assuming equal initial volumes of fuel and coolant.

Vukovic, G.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States). Nuclear Engineering and Engineering Physics Dept.

1996-07-01

201

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

202

Lipid polymorphism in lyotropic liquid crystals for triggered release of bioactives.  

PubMed

In this review we present recent progress on lyotropic liquid crystals (LLC) as delivery vehicles for cosmetoceuticals, nutraceuticals, and drugs. LLC have been known for decades and their potential as delivery vehicles is well recognized. Yet, the two major mesophases, reverse hexagonal (H(II)) and bicontinuous cubic (primitive, gyroid, and diamond), are relatively hard gels with very slow release kinetics of the bioactives. In recent years a discontinuous cubic micellar mesophase (Q(L)) was characterized and studied, showing significant potential as a delivery vehicle. In addition, the H(II) mesophase formed could be much more fluid and produced at room temperature. Recent studies concentrated on establishing methods to evaluate solubilization capacity and relationship between the diameter and length of the cylinders and the nature of the solubilizates. Special attention was given to finding methods to target the vehicles to the lumen and to trigger the release of the bioactives. This review summarizes the efforts of our group along with work by numerous other scientists in this area. All these efforts suggest that the lyotropic mesophases and the corresponding dispersed soft particles (cubosomes, hexosomes, micellosomes) are now more than ever ready to become drug delivery vehicles for transport across the skin and the gut. PMID:22592749

Garti, Nissim; Libster, Dima; Aserin, Abraham

2012-07-01

203

Determination of the insecticide imidacloprid in water and soil using high-performance liquid chromatography  

Microsoft Academic Search

We describe an analytical technique for measuring residues of imidacloprid, a relatively new and highly active insecticide, in water and soil using high-performance liquid chromatography (HPLC). All analyses were performed on reversed-phase HPLC with UV detection at 270 nm using a mobile phase of acetonitrile-water (20:80, v\\/v). Fortified water samples were extracted with either solid-phase extraction (SPE) or liquid-liquid extraction

Sundaram Baskaran; Rai S. Kookana; Ravendra Naidu

1997-01-01

204

Liquid water fade margin requirements for infrared and millimeter wave runway imaging sensors in fog  

Microsoft Academic Search

Liquid water content and particle size distribution at each ten meters in the vertical for a deep advection fog and a shallow\\u000a radiation fog are analyzed to determine the liquid water loss at millimeter and infrared wavelengths. The liquid water fade\\u000a margin is calculated along a three degree glideslope in each fog from the current height above the runway to

Robert E. Marshall; David A. de Wolf; Christos Kontogeorgakis

1997-01-01

205

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

206

Determination of phenolic compounds in water samples by HPLC following ionic liquid dispersive liquid-liquid microextraction and cold-induced aggregation  

Microsoft Academic Search

We report on the determination of bisphenol A and 2-naphthol in water samples using ionic liquid cold-induced aggregation\\u000a dispersive liquid-liquid microextraction combined with HPLC. Parameters governing the extraction efficiency (disperser solvent,\\u000a volume of extraction and disperser solvent, pH, temperature, extraction time) were optimized and resulted in enrichment factors\\u000a of 112 for bisphenol A and of 186 for 2-naphthol. The calibration

Xinyu Jiang; Hui Zhang; Xiaoqing Chen

207

Hydrogen bonds in liquid water are broken only fleetingly  

NASA Astrophysics Data System (ADS)

Although it is widely accepted that the local structure of liquid water has tetrahedral arrangements of molecules ordered by hydrogen bonds, the mechanism by which water molecules switch hydrogen-bonded partners remains unclear. In this mechanism, the role of nonhydrogen-bonded configurations (NHBs) between adjacent molecules is of particular importance. A molecule may switch hydrogen-bonding partners either (i) through thermally activated breaking of a hydrogen bond that creates a dangling hydrogen bond before finding a new partner or (ii) by infrequent but rapid switching events in which the NHB is a transition state. Here, we report a combination of femtosecond 2D IR spectroscopy and molecular dynamics simulations to investigate the stability of NHB species in an isotopically dilute mixture of HOD in D2O. Measured 2D IR spectra reveal that hydrogen-bonded configurations and NHBs undergo qualitatively different relaxation dynamics, with NHBs returning to hydrogen-bonded frequencies on the time scale of water's fastest intermolecular motions. Simulations of an atomistic model for the OH vibrational spectroscopy of water yield qualitatively similar 2D IR spectra to those measured experimentally. Analysis of NHBs in simulations by quenching demonstrates that the vast majority of NHBs are in fact part of a hydrogen-bonded well of attraction and that virtually all molecules return to a hydrogen-bonding partner within 200 fs. The results from experiment and simulation demonstrate that NHBs are intrinsically unstable and that dangling hydrogen bonds are an insignificant species in liquid water. Author contributions: J.D.E., J.J.L., C.J.F., A.T., and P.L.G. designed research; J.D.E., J.J.L., C.J.F., and S.T.R. performed research; J.D.E., J.J.L., C.J.F., S.T.R., A.T., and P.L.G. analyzed data; and J.D.E., J.J.L., C.J.F., S.T.R., A.T., and P.L.G. wrote the paper.Abbreviations: HB, hydrogen-bonded configuration; NHB, nonhydrogen-bonded configuration; MD, molecular dynamics.†J.D.E. and J.J.L. contributed equally to this work.‡Present address: Department of Chemistry, Columbia University, New York, NY 10027.§Present address: Department of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853.

Eaves, J. D.; Loparo, J. J.; Fecko, C. J.; Roberts, S. T.; Tokmakoff, A.; Geissler, P. L.

2005-09-01

208

Experimental evidence of the ferroelectric nature of the ?-point transition in liquid water  

NASA Astrophysics Data System (ADS)

We studied the dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by pore sizes 3-10 nm. Freezing temperature suppression in nanopores helps keep the water samples in liquid form at temperatures well below 0°C and thus effectively study the properties of supercooled liquid water. We report the first direct measurements of the dielectric constant by the dielectric spectroscopy method and demonstrate very clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the ?-point in the supercooled bulk water in full agreement with the recently developed model of the polar liquid.

Fedichev, P. O.; Menshikov, L. I.; Bordonskiy, G. S.; Orlov, A. O.

2011-11-01

209

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

210

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.

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

2001-01-01

211

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

212

Temperature-Mediated Heteroduplex Analysis Performed by Using Denaturing High-Performance Liquid Chromatography To Identify Sequence Polymorphisms in Mycobacterium tuberculosis Complex Organisms  

PubMed Central

PCR products containing sequence polymorphisms were prepared from six mycobacterial genes, denatured, mixed with reference PCR products, and reannealed; the mixtures were then examined with a denaturing high-performance liquid chromatography system (WAVE) equipped with a temperature-controlled alkalated polystyrene divinyl benzene column. Mismatching of bases in heteroduplexes of the PCR products causes elution patterns of the DNA from the column to be altered. The six mycobacterial genes studied were oxyR, in which a specific polymorphism (G1031A) is found only in certain species of the Mycobacterium tuberculosis complex, and five genes in which mutations associated with antituberculosis drug resistance have been found. The resistance genes (with affected drug and PCR product sizes given parenthetically) were rpoB (rifampin; 258 bp), katG (isoniazid; 205 bp), pncA (pyrazinamide; 579 bp); rpsL (streptomycin; 196 bp), and embB (ethambutol; 185 bp). Elution patterns of heteroduplexes of all 20 polymorphisms studied shifted detectably at column temperatures ranging from 65.3 to 68°C and elution times of 3.5 to 6 min. These results show that temperature-mediated heteroduplex analysis is a potentially useful genotypic screen for mutations associated with antituberculosis drug resistance and for the G1031A polymorphism in oxyR. The method may allow users to detect novel as well as heterogeneous mutations without using expensive kits or detection labels.

Cooksey, Robert C.; Morlock, Glenn P.; Holloway, Brian P.; Limor, Josef; Hepburn, Michael

2002-01-01

213

Onset of simple liquid behaviour in modified water models  

NASA Astrophysics Data System (ADS)

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

2014-04-01

214

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

215

Energy loss measurement of protons in liquid water.  

PubMed

The proton stopping power of liquid water was, for the first time, measured in the energy range 4.7-15.2 MeV. The proton energies were determined by the time-of-flight transmission technique with the microchannel plate detectors, which were especially developed for timing applications. The results are compared to the literature values (from ICRU Report 49 (1993) and Janni's tabulation (1982 At. Data Nucl. Data Tables 27 147-339)) which are based on Bethe's formula and an agreement is found within the experimental uncertainty of 4.6%. Thus, earlier reported discrepancy between the experimental and literature stopping power values at lower energies was not observed at the energies considered in this experiment. PMID:21427483

Siiskonen, T; Kettunen, H; Peräjärvi, K; Javanainen, A; Rossi, M; Trzaska, W H; Turunen, J; Virtanen, A

2011-04-21

216

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

217

Relationship between optical extinction and liquid water content in fogs  

NASA Astrophysics Data System (ADS)

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

Klein, C.; Dabas, A.

2013-11-01

218

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

NASA Astrophysics Data System (ADS)

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

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

1989-03-01

219

DETERMINATION OF THE INSECT GROWTH REGULATOR METHOPRENE IN NATURAL WATERS BY CAPILLARY GAS-LIQUID CHROMATOGRAPHY  

EPA Science Inventory

Residues of methoprene were measured in natural waters by capillary as liquid chromatography (GLG). Methoprene was extracted in the field by liquid-liquid partitioning with dichloromethane, transPorted to the laboratory, and extracted a second time with hexane. The extracts were ...

220

The discovery of liquid water on Mars and its implications for astrobiology  

NASA Astrophysics Data System (ADS)

Since liquid water is a key ingredient for life as we know it, NASA has adopted the theme "follow the water" as an strategy for exploring Mars. Recently, Renno et al.1,2 showed evidence that liquid saline-water exists in areas disturbed by the Phoenix Mars Lander. Moreover, they argued that the thermodynamics of freeze-thaw cycles leads to the formation of concentrated saline solutions (brines) with freezing temperatures much higher than current summer ground temperatures where ground ice exists near the surface and therefore liquid saline-water should be common on Mars. Here we summarize these ideas, present some new results, and discuss their implications for astrobiology. We propose a strategy for searching for liquid saline water on Mars and argue that NASA's theme for the exploration of Mars should be updated to "follow the liquid water."

Rennó, N. O.; Mehta, M.; Block, B. P.; Braswell, S.

2009-08-01

221

Liquid-Liquid Interface Study of Hydrocarbons, Alcohols, and Cationic Surfactants with Water  

NASA Astrophysics Data System (ADS)

Molecular interaction dynamics at liquid-liquid interface (LLI), involved nondispersive solution as compared with the interaction in bulk phase. Thereby, interfacial tension (IFT, mN/m) of LLI for four saturated hydrocarbons, six alcohols, and three cationic surfactants are reported at 298.15 K. The pentane, hexane, heptane, octane hydrocarbons and pentanol, hexanol, heptanol, 1-octanol, 2-octanol, and 1-decanol alcohols were used and IFT data were compared with 4 mm kg-1 dodecyltrimethylammoniumbromide (DTAB), trimethylsulfoxoniumiodide (TMSOI), methyltrioctylammoniumchloride (MTOAC) surfactants studied in benzene-water LLI. The IFT data are noted as hydrocarbons > DTAB > TMSOI > alcohols > MTOAC. The hydrocarbons and alcohols decreased IFT within 16 to 49% and 87 to 92%, respectively, whereas the surfactants within 78.3 to 95.9%. The alcohols developed interaction similar to surfactants and are denoted as nonionic surfactants for making mixtures of low IFT with hydrophilic and hydrophobic interactions to the level of the surfactants. The pentanol and MTOAC caused similar decrease in IFT so the pentanol developed the hydrophilic and hydrophobic interactions of the strength of MTOAC. Comparatively, the hydrocarbons showed lower decrease but the octane showed 49% decrease in IFT. Thus, the hydrocarbon with longer alkyl chain and the alcohol with shorter behave as good surfactants. The hydrocarbons with inductive effect on sigma bond between carbon atoms in alkyl chain also weakened the IFT and influenced the hydrophobic interactions. The MTOAC with four octyl units reduced 96% IFT so inductive effects monitor LLI dynamics.

Singh, Man; Matsuoka, Hideki

222

A Rapid Analysis of Surface Waters by High Pressure Liquid Chromatography.  

National Technical Information Service (NTIS)

A simple rapid method for obtaining fingerprint traces of nonpolar organic contaminants in water samples by trace enrichment and high pressure liquid chromatography (HPLC) has been evolved. Samples of 30-1000 ml of river water were filtered through precol...

K. Huibregtse

1979-01-01

223

(Vapour + liquid + liquid) equilibria and excess molar enthalpies of binary and ternary mixtures of isopropanol, water, and propylene  

Microsoft Academic Search

A static VLE apparatus has been used for the measurement of the (vapour+liquid+liquid) equilibrium of the (propylene+isopropanol+water) system at T=313.15K and pressures between (1.381 and 1.690)MPa. Using an isothermal flow calorimeter, HE values have been obtained for the binary system (isopropanol+water) over the temperature range from (313.15 to 353.15)K and pressures from (3.8 to 4.19)MPa. For the pseudo-binary mixture (propylene+(isopropanol+water)),

Maurizio Grigiante; Paolo Stringari; Giancarlo Scalabrin; E. Christian Ihmels; Kai Fischer; Jürgen Gmehling

2008-01-01

224

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

Microsoft Academic Search

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

X. Wu; G. R. Diak; C. M. Hayden; J. A. Young

1995-01-01

225

Influence of water on the surface of hydrophilic and hydrophobic room-temperature ionic liquids.  

PubMed

Vibrational spectroscopy, sum frequency generation, has been used to study the gas-liquid interface of imidazolium-based, room-temperature ionic liquids. The ionic liquids are divided into two categories on the basis of their miscibility with water, as hydrophobic (immiscible) and hydrophilic (miscible). The spectroscopy results indicate that water will reorient the cations of the hydrophobic ionic liquid, while in the hydrophilic ones they remain unaffected. Thus, under low water conditions the plane of the imidazolium ring remains parallel to the surface for both types of ionic liquid. However, at high water content the ring will reorient to along the surface normal for the hydrophobic ionic liquid but remain parallel to the surface for the hydrophilic one. This is a reversible process. PMID:15382902

Rivera-Rubero, Selimar; Baldelli, Steven

2004-09-29

226

Use of salt hydrate pairs to control water activity for enzyme catalysis in ionic liquids.  

PubMed

Salt hydrate pairs were used to control water activity in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate. It was shown that salt hydrate pairs behave essentially the same in ionic liquids as they do in organic solvents as long as they do not dissolve. Initial rate-water activity profiles were prepared for the immobilized Candida antarctica lipase catalyzed synthesis of 2-ethylhexyl methacrylate. The ability to use salt hydrate pairs for the control of water activity in ionic liquids should allow for improved comparison of enzyme activity and specificity in ionic liquids and conventional solvents. PMID:12790674

Berberich, Jason A; Kaar, Joel L; Russell, Alan J

2003-01-01

227

A model of vapor-liquid equilibria for acid gas-alkanolamine-water systems  

Microsoft Academic Search

A physico-chemical model was developed for representing liquid phase chemical equilibria and vapor-liquid (phase) equilibria of HâSCOâ-alkanolamine-water systems. The equilibrium composition of the liquid phase is determined by minimization of the Gibbs free energy. Activity coefficients are represented with the Electrolyte-NRTL equation treating both long-range electrostatic interactions and short-range binary interactions between liquid phase species. Vapor phase fugacity coefficients are

Austgen; D. M. Jr

1989-01-01

228

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

229

The Liquid Water Content of Small Cumuli from Turbulent Entrainment at Cloud Top  

Microsoft Academic Search

Measurements in small cumulus clouds have often shown that the amount of liquid water present is less than the amount expected if a parcel of saturated air rose from cloud base by a reversible adiabatic ascent. Most attempts in the past to explain this liquid water deficiency have employed entrainment of clear air into the sides of the clouds to

Robert George Lamontagne

1981-01-01

230

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

231

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...

232

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

NASA Astrophysics Data System (ADS)

Aims: Looking for the primary rainbow in starlight that is reflected by exoplanets appears to be a promising method to search for liquid water clouds in exoplanetary atmospheres. Ice water clouds, that consist of water crystals instead of water droplets, could potentially mask the rainbow feature in the planetary signal by covering liquid water clouds. Here, we investigate the strength of the rainbow feature for exoplanets that have liquid and icy water clouds in their atmosphere, and calculate the rainbow feature for a realistic cloud coverage of Earth. Methods: We calculate flux and polarization signals of starlight that is reflected by horizontally and vertically inhomogeneous Earth-like exoplanets, covered by patchy clouds consisting of liquid water droplets or water ice crystals. The planetary surfaces are black. Results: On a planet with a significant coverage of liquid water clouds only, the total flux signal shows a weak rainbow feature. Any coverage of the liquid water clouds by ice clouds, however, dampens the rainbow feature in the total flux, and thus the discovery of liquid water in the atmosphere. On the other hand, detecting the primary rainbow in the polarization signal of exoplanets appears to be a powerful tool for detecting liquid water in exoplanetary atmospheres, even when these clouds are partially covered by ice clouds. In particular, liquid water clouds covering as little as 10-20% of the planetary surface, with more than half of these covered by ice clouds, still create a polarized rainbow feature in the planetary signal. Indeed, calculations of flux and polarization signals of an exoplanet with a realistic Earth-like cloud coverage, show a strong polarized rainbow feature.

Karalidi, T.; Stam, D. M.; Hovenier, J. W.

2012-12-01

233

Statistical physics and liquid water at negative pressures  

NASA Astrophysics Data System (ADS)

Angell and his collaborators have underscored the importance of studying water under all extremes of pressure-squeezing to high pressures and stretching to negative pressures. Here we review recent results of molecular dynamics simulations of two models of liquid water, the extended simple point charge (SPC/E) and the Mahoney-Jorgensen transferable intermolecular potential with five points (TIP5P), which is closer to real water than previously proposed classical pairwise additive potentials. In particular, we describe simulations of the TIP5P model for a wide range of deeply supercooled states, including both positive and negative pressures, which reveal (i) the existence of a non-monotonic “nose-shaped” temperature of maximum density (TMD) line and a non-reentrant spinodal, (ii) the presence of a low-temperature phase transition. The TMD that changes slope from negative to positive as P decreases and, notably, the point of crossover between the two behaviors is located at ambient pressure (temperature ? 4° C, and density ? 1 g/cm3). We also describe simulations of the dynamics of the SPC/E model, which reveal (iii) the dynamics at negative pressure shows a minimum in the diffusion constant D when the density is decreased at constant temperature, complementary to the known maximum of D at higher pressures, and (iv) the loci of minima of D relative to the spinodal shows that they are inside the thermodynamically metastable regions of the phase diagram. These dynamical results reflect the initial enhancement and subsequent breakdown of the tetrahedral structure and of the hydrogen bond network as the density decreases.

Stanley, H. Eugene; Barbosa, M. C.; Mossa, S.; Netz, P. A.; Sciortino, F.; Starr, F. W.; Yamada, M.

2002-11-01

234

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 Schiff’s 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

235

Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS  

Microsoft Academic Search

A simple, rapid and reproducible method for the determination of some pesticide residues in water was developed using micro\\u000a liquid-liquid extraction and gas chromatography - mass spectrometry with selected ion monitoring (GC\\/MS-SIM). The chlorinated\\u000a insecticides ?- and ?-endosulfan and endosulfan-sulfate as well as the synthetic pyrethroids bifenthrin, permethrin, cypermethrin,\\u000a fenvalerate and deltamethrin can be separated from a 500 mL sample

A. Fernández-Gutiérrez; J. L. Martínez-Vidal; F. J. Arrebola-Liébanas; A. Gonzalez-Casado; J. L. Vílchez

1998-01-01

236

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

237

Occurrence, liquid water content, and fraction of supercooled water clouds from combined CALIOP\\/IIR\\/MODIS measurements  

Microsoft Academic Search

The CALIOP depolarization measurements, combined with backscatter intensity measurements, are effective in discriminating between water clouds and ice clouds. The same depolarization measurements can also be used for estimating liquid water content information. Using cloud temperature information from the collocated infrared imaging radiometer measurements and cloud water paths from collocated MODIS measurements, this study compiles global statistics of the occurrence

Yongxiang Hu; Sharon Rodier; Kuan-man Xu; Wenbo Sun; Jianping Huang; Bing Lin; Pengwang Zhai; Damien Josset

2010-01-01

238

Hydrophobic zeolites for biofuel upgrading reactions at the liquid-liquid interface in water/oil emulsions.  

PubMed

HY zeolites hydrophobized by functionalization with organosilanes are much more stable in hot liquid water than the corresponding untreated zeolites. Silylation of the zeolite increases hydrophobicity without significantly reducing the density of acid sites. This hydrophobization with organosilanes makes the zeolites able to stabilize water/oil emulsions and catalyze reactions of importance in biofuel upgrading, i.e., alcohol dehydration and alkylation of m-cresol and 2-propanol in the liquid phase, at high temperatures. While at 200 °C the crystalline structure of an untreated HY zeolite collapses in a few hours in contact with a liquid medium, the functionalized hydrophobic zeolites keep their structure practically unaltered. Detailed XRD, SEM, HRTEM, and BET analyses indicate that even after reaction under severe conditions, the hydrophobic zeolites retain their crystallinity, surface area, microporosity, and acid density. It is proposed that by preferentially anchoring hydrophobic functionalities on the external surface, the direct contact of bulk liquid water and the zeolite is hindered, thus preventing the collapse of the framework during the reaction in liquid hot water. PMID:22548687

Zapata, Paula A; Faria, Jimmy; Ruiz, M Pilar; Jentoft, Rolf E; Resasco, Daniel E

2012-05-23

239

Boson Peak in Deeply Cooled Confined Water: A Possible Way to Explore the Existence of the Liquid-to-Liquid Transition in Water  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

240

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; Leão, Juscelino B; Copley, John R D; Tyagi, Madhusudan; Podlesnyak, Andrey; Kolesnikov, Alexander I; Mou, Chung-Yuan; Chen, Sow-Hsin

2014-06-13

241

Simultaneous detection of variable number tandem repeats, single nucleotide polymorphisms, and allelic imbalance in the thymidylate synthase gene enhancer region using denaturing high-performance liquid chromatography.  

PubMed

Polymorphisms in the thymidylate synthase enhancer region (TSER) have been reported to be associated with alterations in thymidylate synthase (TS) mRNA protein levels. The TSER is characterized by the presence of variable double (2R) and triple (3R) number tandem repeats (VNTRs). In addition to VNTRs, single nucleotide polymorphisms (SNPs) and allelic imbalance (AI), including loss of heterozygosity (LOH), have recently been associated with response to 5-fluorouracil (5-FU)-based chemotherapy. The aim of the current study was to develop a specific denaturing high-performance liquid chromatography (DHPLC) method for the rapid detection of these variations in the TSER in clinical samples. DHPLC analysis was validated in parallel with agarose gel electrophoresis (AGE), enzyme digestion, and quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR). The optimized DHPLC method resolved 100% of the known TSER variations, differentiated between homozygous and heterozygous genotypes, and allowed the qualitative and quantitative detection of AI, including LOH, in tumor samples. This DHPLC method was developed to permit the rapid, sensitive, and accurate identification of the TSER genotype (VNTRs, SNPs, and AI) in clinical protocols where response to flouropyrimidines may be correlated with TSER polymorphisms. PMID:15494134

Ezzeldin, Hany; Hoffmayer, Cornelia; Soong, Richie; Johnson, Martin R; Lee, Adam; Heslin, Marty; Diasio, Robert

2004-11-15

242

Development of an ionic liquid-based dispersive liquid-liquid micro-extraction method for the determination of phthalate esters in water samples.  

PubMed

Ionic liquid-based dispersive liquid-liquid micro-extraction (IL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) for the determination of four phthalate esters, including butyl benzyl phthalate, di-n-butyl phthalate, dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate in water samples. The mixture of ionic liquid (IL) and dispersive solvent was rapidly injected into 10 mL aqueous sample. Then, IL phase was separated by centrifugation and was determined by high-performance liquid chromatography-ultraviolet. The factors influencing the extraction efficiency, such as type and volume of IL, disperse solvent, extraction time, centrifuging time and ionic strength, were investigated and optimized. Under the optimized conditions, the extraction recoveries by the proposed ionic liquid-based dispersive liquid-liquid micro-extraction for the four phthalates ranged from 83.0 to 91.7%. The relative standard deviations were between 7.8 and 15%. The limits of quantification for four phthalates were between 10.6 and 28.5 ?g/L. The proposed method was successfully applied for the analysis of PAEs in tap, lake and treated wastewater samples. PMID:21604368

Sha, Chen; Yi-Sheng, Zhong; Shui-Yuan, Cheng; Tian, Qian; Hao, Sun

2011-07-01

243

Liquid–liquid equilibria for quaternary mixtures of water, ethanol, and 2,2,4-trimethylpentane with fuel additives  

Microsoft Academic Search

The experimental tie-line data measured for two quaternary mixtures of the water–ethanol–2,2,4-trimethylpentane–methyl tert-butyl ether (MTBE) and water–ethanol–2,2,4-trimethylpentane–tert-amyl methyl ether (TAME) systems at the temperature 298.15 K and ambient pressure are presented. The experimental quaternary liquid–liquid equilibrium data have been satisfactorily correlated by using a modified form of the UNIQUAC model with binary, ternary and quaternary parameters. The calculated results are

Kazuhiro Tamura; Yao Chen; Kaoru Tada; Toshiro Yamada

2000-01-01

244

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

PubMed

Liquid-liquid-liquid microextraction (LLLME) with hollow fibers in high-performance liquid chromatography (HPLC) has been applied as a rapid and sensitive quantitative method for the detection of four aromatic amines (3-nitroaniline, 4-chloroaniline, 4-bromoaniline and 3,4-dichloroaniline) in environmental water samples. The preconcentration procedure was induced by the pH difference inside and outside the hollow fiber. The target compounds were extracted from 4-ml aqueous sample (donor solution, pH approximately 13) through a microfilm of organic solvent (di-n-hexyl ether), immobilized in the pores of a hollow fiber (1.5 cm length x 0.6 mm I.D.), and finally into 4 microl of acid acceptor solution inside the fiber. After a prescribed period of time, the acceptor solution inside the fiber was withdrawn into the microsyringe and directly injected into the HPLC system for analysis. Factors relevant to the extraction procedure were studied. Up to 500-fold enrichment of analytes could be obtained under the optimized conditions (donor solution: 0.1 M sodium hydroxide solution with 20% sodium chloride and 2% acetone; organic phase: di-n-hexyl ether; acceptor solution: 0.5 M hydrochloric acid and 500 mM 18-crown-6 ether; extraction time of 30 min; stirring at 1,000 rev./min). The procedure also served as a sample clean-up step. The influence of humic acid on the extraction efficiency was also investigated, and more than 85% relative recoveries of the analytes at two different concentrations (20 and 100 microg/l) were achieved at various concentration of humic acid. This technique is a low cost, simple and fast approach to the analysis of polar compounds in aqueous samples. PMID:12187976

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

2002-07-19

245

Application of dispersive liquid–liquid microextraction and reversed phase-high performance liquid chromatography for the determination of two fungicides in environmental water samples  

Microsoft Academic Search

Dispersive liquid–liquid microextraction (DLLME) has been developed for the extraction and preconcentration of diethofencarb (DF) and pyrimethanil (PM) in environmental water. In the method, a suitable mixture of extraction solvent (50 µL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) are injected into the aqueous samples (5.00 mL) and the cloudy solution is observed. After centrifugation, the enriched analytes in

Jing Cheng; Yiwen Zhou; Mei Zuo; Liping Dai; Xiaojie Guo

2010-01-01

246

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

247

Isobaric vapor-liquid equilibrium for ethanol + water + sodium nitrate  

Microsoft Academic Search

The salt effect on the vapor-liquid equilibrium of mixed solvents provides a potential technique of extractive distillation, in which a dissolved salt, rather than a liquid additive, is used as the separating agent. This salt distillation process has been used in the purification of close-boiling, azeotropic, and other systems which are difficult to separate. The isobaric vapor-liquid equilibrium for ethanol

M. Pilar Peña; Ernesto Vercher; Antoni Martinez-Andreu

1996-01-01

248

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

PubMed

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. PMID:24189605

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

2014-01-01

249

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

PubMed Central

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

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

2009-01-01

250

Estimated accuracy of ground-based liquid water measurements during FIRE  

NASA Technical Reports Server (NTRS)

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

Snider, Jack B.

1990-01-01

251

Mesoscale modeling of the water liquid-vapor interface: A surface tension calculation  

NASA Astrophysics Data System (ADS)

We report a mesoscale modeling of the liquid-vapor interface of water. A mesoscopic model of water has been established in dissipative particle dynamics (DPD) to reproduce the interfacial properties of water. The surface tension and coexisting densities are compared between atomistic and mesoscopic simulations. Simple scaling relations have been established to link the atomistic and mesoscopic length and time scales. Our study demonstrates the capability of the DPD method to explore the interfacial properties of a planar water liquid-vapor interface and a water nanodroplet. This constitutes an important step toward the calculation of the surface tension of larger and more complex interfacial systems.

Ghoufi, A.; Malfreyt, P.

2011-05-01

252

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

253

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

254

Prediction of Liquid and Vapor Enthalpies of Ammonia-water Mixture  

Microsoft Academic Search

The ammonia-water mixture may be commonly employed as a working fluid in the absorption chiller, especially because both ammonia and water are natural substances and are harmless. In addition, these substances have excellent thermodynamic properties. In this study, an alternative method using the artificial neural network (ANN) to determine liquid and vapor enthalpies of ammonia-water mixture is presented. The training

A. ?encan; S. Gök; E. Dikmen

2011-01-01

255

Confinement influence in liquid water studied by Raman and neutron scattering  

Microsoft Academic Search

We present a detailed Raman scattering study performed in liquid water confined in a porous sol-gel glass having 25 diameter pores. The measurements were carried out in the OH vibrational stretching region, ranging from 2700 cm-1 to 3700 cm-1 . By comparing the bulk water with the confined one, strong modification of the vibrational dynamics of adsorbed water on the

V. Crupi; S. Magazù; D. Majolino; P. Migliardo; V. Venuti; M.-C. Bellissent-Funel

2000-01-01

256

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

PubMed

Dielectric spectroscopy is a measure of the collective Coulomb interaction in liquid systems. Adding ionic liquids to an aqueous solution results in a decrease of the static value of the generalized dielectric constant which cannot be attributed to kinetic depolarization models characterized by the static conductivity and rotational relaxation constant. However, a dipolar Poisson-Boltzmann model computing the water depolarization in the proximity of ions is not only successful for simple electrolytes but also in case of molecular ionic liquids. Moreover, our simple geometric hydration model is also capable to explain the dielectric depolarization. Both models compute the dielectric constant of water and obtain the overall dielectric constant by averaging the values of its components, water and the ionic liquid, weighted by their volume occupancies. In this sense, aqueous ionic liquid mixtures seem to behave like polar mixtures. PMID:24880299

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

2014-05-28

257

Quaternary liquid/liquid equilibria of sodium sulfate, sodium sulfite and water with two solvents: Acetone and 2-propanol  

SciTech Connect

Aqueous solutions of sodium sulfate and sodium sulfite are produced from sodium carbonate in flue-gas scrubbers; recovery of these salts often requires multi-effect evaporators; however, a new energy-efficient unit operation called extractive crystallization has been shown to have reduced energy costs. In this process, an organic solvent is added to the aqueous salt solution to precipitate salt. Acetone is a suitable solvent for this process, better than 2-propanol. Liquid/liquid/solid equilibria for ternary systems containing a salt, water, and an organic solvent were measured. Systems investigated were sodium sulfite/water/acetone and sodium sulfite/water/2-propanol. Experiments were conducted at salt saturation covering a temperature range between the lower consolute temperature and 48.6{degrees}C. In the attempt to improve the extractive crystallization process for recovery of sodium sulfate from flue-gas scrubbers, attention was given to a feed containing a mixture of sodium sulfite and sodium sulfate. Liquid-liquid equilibria for quaternary systems containing two salts, water, and an organic solvent were experimentally determined at 35{degrees}C. The systems investigated were sodium sulfate/sodium sulfite/water/acetone and sodium sulfate/sodium sulfite/water/2propanol. The systems were studied at three salt ratios. For each salt ratio, experiments were conducted starting at saturation, water was then added until the one-phase region was reached. Mixtures of the two salts proved to have a small disadvantage relative to the 100 % sulfate feed process. Therefore, a sulfate-based extractive crystallization process is recommended.

Schiozer, A.L.

1994-03-01

258

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

259

Vapor–Liquid Equilibrium of Ethanol–Water System in the Presence of Molecular Sieves  

Microsoft Academic Search

Adsorptive distillation is a new process to separate liquid mixtures in a packed distillation column. It depends on using active packing material instead of inert packing material in a packed distillation column. The active packing material can affect the intermolecular forces among the system components and thus alter its vapor–liquid equilibrium (VLE). The VLE of the ethanol–water system at 1

FAHMI A. ABU AL-RUB; FAWZI A. BANAT; RAMI JUMAH

1999-01-01

260

Correlation of vapor - liquid equilibrium data for acetic acid - isopropanol - water - isopropyl acetate mixtures  

Microsoft Academic Search

A correlation procedure for the prediction of vapor - liquid equilibrium of acetic acid - isopropanol - water - isopropyl acetate mixtures has been developed. It is based on the NRTL model for predicting liquid activity coefficients, and on the Hayden-O'Connell second virial coefficients for predicting the vapor phase of systems containing association components. When compared with experimental data the

E. A. Campanella

2006-01-01

261

Freely accessible water does not decrease consumption of ethanol liquid diets  

Microsoft Academic Search

In experimental studies, liquid ethanol diets are usually given as the sole source of nutrition and fluid. Two series of experiments were conducted to examine the effect of freely accessible water on the consumption of ethanol liquid diets in male Long–Evans rats. The consumption of diets and subsequent learning ability of rats were first examined in animals given twice-daily saline

NancyEllen C de Fiebre; Christopher M de Fiebre

2003-01-01

262

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

263

Coating permits use of strain gage in water and liquid hydrogen  

NASA Technical Reports Server (NTRS)

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

Berven, B. B.

1966-01-01

264

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

265

Determination of222Rn concentrations in Lithuanian spa waters by liquid scintillation counting  

NASA Astrophysics Data System (ADS)

Characterisation of222Rn concentrations in Lithuanian spa waters and comparison of the measured radon concentrations in spa waters with those in ground waters with a small content of mineral salts and in waters from private wells were the objectives of this study. The measurements were performed in 34 spa water sources in four different places of Lithuania using the liquid scintillation method with a Packard Liquid Scintillation Analyser Tri-Carb 2770 TR/SL and the Packard BioScience cocktail. Techniques of222Rn extraction from water samples with a high mineralization to toluene in order to exclude precipitation in a mixture with organic scintillation cocktail are discussed. Results of comparison of the two methods—liquid scintillation counting and that using E-PERMS® system electrets—are also presented.

Ladygiene, R.; Mastauskas, A.; Morkunas, G.; Gasiunas, K.

1999-01-01

266

Test of Prototype Liquid-Water-Content Meter for Aircraft Use.  

National Technical Information Service (NTIS)

This report describes the effort undertaken to meet the objectives of National Science Foundation Grant ATM-9207345 titled 'Test of Prototype Liquid-Water-Content Meter for Aircraft Use.' Three activities were proposed for testing the new aircraft instrum...

H. E. Gerber

1993-01-01

267

Targeting In-Situ Liquid Water Analysis with New Probes on Mars  

NASA Astrophysics Data System (ADS)

We summarize parameters and reasons that present rationality of shifting the view of selecting landing sites toward higher latitudes in order to find promisful candidates for liquid water or brine detection and biosignature containing localities.

Bérczi, Sz.; Horváth, A.; Pócs, T.; Sik, A.; Szathmáry, E.; Kereszturi, Á.

2012-06-01

268

Emissions Prediction and Measurement for Liquid-Fueled TVC Combustor with and without Water Injection.  

National Technical Information Service (NTIS)

An investigation is performed to evaluate the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid-fueled combustor that uses water injection for control of pollutant emissions. The experiment consis...

A. Brankovic R. C. Ryder R. C. Hendricks N. S. Liu D. T. Shouse W. M. Roquemore

2005-01-01

269

Ab initio calculation of the electronic absorption spectrum of liquid water  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

270

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

PubMed

The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase. PMID:24784291

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

2014-04-28

271

Molecular dynamics simulations of charged nanoparticle self-assembly at ionic liquid-water and ionic liquid-oil interfaces  

NASA Astrophysics Data System (ADS)

Nanoparticle self-assembly at liquid-liquid interfaces can be significantly affected by the individual nanoparticle charges. This is particularly true at ionic liquid (IL) based interfaces, where Coulombic forces play a major role. Employing 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) as a model IL, we have studied the self-assembly of hydrophobic nanoparticles with different surface charges at the IL/water and IL/oil (hexane) interfaces using molecular dynamics simulations. In the IL/water system, the nanoparticles were initially dispersed in the water phase but quickly equilibrated at the interface, somewhat in favor of the IL phase. This preference was lessened with increased nanoparticle charge. In the IL/hexane system, all charged nanoparticles interacted with the IL to some extent, whereas the uncharged nanoparticles remained primarily in the hexane phase. Potential of mean force calculations supported the observations from the equilibrium studies and provided new insights into the interactions of the nanoparticles and ionic liquid based interfaces.

Frost, Denzil S.; Dai, Lenore L.

2012-02-01

272

Vapor liquid equilibria for the quaternary system of formaldehyde(1)-methanol(2)-methylal(3)-water(4)  

Microsoft Academic Search

The vapor-liquid equilibria in the quaternary system of formaldehyde(1)-methanol(2)-methylal(3)-water(4) were measured experimentally at a pressure of 101.33 ± 0.02 kPa, and at temperatures from about 318 to 367 K. The concentration ranges of the liquid phase were, formaldehyde < 15% (in mass), methanol < 42%, and methylal and water from 0 to 100%. Brandani's physico-chemical model was extended to correlate

Zhengjun Shan; Yanru Wang; Shouchang Qiu; Chongyu Zheng; Jun Shi

1995-01-01

273

Deliquescence, liquid water, and the search for sources and sinks of methane on Mars  

Microsoft Academic Search

The recent discoveries of evidence for liquid saline water1,2,3,4 and methane5 on Mars have excited the science community by reviving the possibility of extant microbial life in this nearby planet. Here we report recently discovered photometric and spectral evidence that liquid saline water exists on Mars4. We show that this finding indicates that deliquescence occurs seasonally on some areas of

N. O. Rennó; M. Mehta

2010-01-01

274

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

NASA Technical Reports Server (NTRS)

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

Mouginismark, P. J.

1987-01-01

275

The Structure Of Liquid Water; Novel Insights From Materials Research; Potential Relevance To Homeopathy  

Microsoft Academic Search

This paper provides an interdisciplinary base of information on the structure of liquid water. It begins with a synthesis built on the information base on the structure5 of noncrystalline, inorganic, covalently-bonded condensed liquid phases, such as SiO2, S, Se, P, and H2O, which exists in the materials science literature. The data for water are analyzed through the prism of well-established

Rustum Roy; W. A. Tiller; Iris Bell; M. R. Hoover

2005-01-01

276

Measurements of mechanical properties of the liquid CO 2-water-CO 2-hydrate system  

Microsoft Academic Search

Microscopic observations of the liquid CO2-water-CO2-hydrate system were conducted to measure both the interfacial tensions in these phases and the strength of the CO2-hydrate film. Measurements on hanging drops revealed that the interfacial tension between liquid CO2 and water decreased slightly as the temperature was raised from 266.3 to 284.9 K, and that the average of the interfacial tension was

Tsutomu Uchida; Jun'ichi Kawabata

1997-01-01

277

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

278

Liquid-Vapor Equilibrium Isotopic Fractionation of Water. How well can classical water models predict it?  

SciTech Connect

The liquid-vapor equilibrium isotopic fractionation of water is determined by molecular-based simulation, via Gibbs Ensemble Monte Carlo and isothermal-isochoric molecular dynamics involving two radically different but realistic models, the extended simple point charge (SPC/E) and the Gaussian charge polarizable (GCP) models. The predicted temperature dependence of the liquid-vapor equilibrium isotopic fractionation factors for H 2 18O / H 2 16O, H 2 17O / H 2 16O, and 2H 1H 16O / 1H 2 16O are compared against the most accurate experimental datasets to assess the ability of these intermolecular potential models to describe quantum effects according to the Kirkwood-Wigner free energy perturbation ! 2 !expansion. Predictions of the vapor pressure isotopic effect for the H 2 18O / H 2 16O and H 2 17O / H 2 16O pairs are also presented in comparison with experimental data and two recently proposed thermodynamic modeling approaches. Finally, the simulation results are used to discuss some approximations behind the microscopic interpretation of isotopic fractionation based on the underlying roto-translational coupling.

Chialvo, Ariel A [ORNL; Horita, Juske [ORNL

2009-01-01

279

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

PubMed

The liquid-vapor equilibrium isotopic fractionation of water is determined by molecular-based simulation, via Gibbs ensemble Monte Carlo and isothermal-isochoric molecular dynamics involving two radically different but realistic models, the extended simple point charge, and the Gaussian charge polarizable models. The predicted temperature dependence of the liquid-vapor equilibrium isotopic fractionation factors for H(2) (18)O/H(2) (16)O, H(2) (17)O/H(2) (16)O, and (2)H(1)H(16)O/(1)H(2) (16)O are compared against the most accurate experimental datasets to assess the ability of these intermolecular potential models to describe quantum effects according to the Kirkwood-Wigner free energy perturbation variant Planck's over h(2)-expansion. Predictions of the vapor pressure isotopic effect for the H(2) (18)O/H(2) (16)O and H(2) (17)O/H(2) (16)O pairs are also presented in comparison with experimental data and two recently proposed thermodynamic modeling approaches. Finally, the simulation results are used to discuss some approximations behind the microscopic interpretation of isotopic fractionation based on the underlying rototranslational coupling. PMID:19275411

Chialvo, Ariel A; Horita, Juske

2009-03-01

280

Liquid water absorption and scattering effects in DOAS retrievals over oceans  

NASA Astrophysics Data System (ADS)

It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided in coarser resolution than hyperspectral DOAS applications require and Vibrational Raman Scattering (VRS) is mostly unconsidered or compensated for using simulated pseudo cross-sections from radiative transfer modelling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS measurements were performed into very clear natural waters achieving underwater light paths of up to 50 m. From these measurements, the retrieval of a residual (H2Ores) spectrum is presented compensating simultaneously for insufficiencies of the liquid water absorption cross-section and broad-banded VRS structures. Small-banded (Ring) structures caused by VRS were found to be very efficiently compensated for by the intensity offset (straylight) correction included in the DOAS fit. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality. This was not achieved using a liquid water cross-section in combination with a simulated VRS spectrum. Typical values of improvement depend on the measurement's contamination with liquid water structures and range from ? 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ores spectrum was found to prevent misfits of NO2 slant columns especially for very low NO2 scenarios and thus increase the reliability of the fit. In test fits on OMI satellite data, the H2Ores spectrum was found selectively above ocean surfaces where it leads to fit quality improvements of up to 6-18%.

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

2014-05-01

281

The vibrational spectrum of water in liquid alkanes.  

PubMed Central

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

Conrad, M P; Strauss, H L

1985-01-01

282

[Simultaneous detection of polymorphisms in the 3'- and 5'-UTR of thymidylate synthase gene using denaturing high-performance liquid chromatography].  

PubMed

Polymorphism which is either in the thymidylate synthase (TS)enhancer region (TSER) of the 5-primer untranslation region (5' UTR) or in the 3-primer untranslation region (3' UTR) has been reported to be associated with the alterations in TS mRNA and protein levels. The TSER is characteristic of the presence of variable double (2R) and triple (3R) number tandem repeats (VNTRs). In addition to VNTRs, single nucleotide polymorphism (SNPs) in 3R, as well as the polymorphism of the fragment length(FLP) in the TS 3'-UTR which is characteristic of the presence or absence of a 6 bp- nucleotide fragment, has recently been reported to be associated with the response to 5-fuorouracil (5-FU)-based chemo-therapy. The aim of the present study was to develop a specifc denaturing high-performance liquid chromatography (DHPLC) method for the rapid and simultaneous detection of these variations in clinical samples. Multi-PCR primers were designed to amplify the two regions simultaneously, The 8.6 min DHPLC gradient was optimized to include the analysis of multiplexed TSER/3' UTR chromatogram peaks, allowing for the simultaneous detection of 28 bp VNTRs and 6 bp FLP under nondenaturing conditions (50). The optimal melting temperature was determined experimentally for the detection of SNP in the TSER VNTRs. Finally, the DHPLC analysis was verified in parallel with PCR-RFLP and sequencing. The optimized DHPLC method resolved 100% of the known TS variations, discriminated between homozygous and heterozy-gous genotypes. This developed DHPLC method could permit the rapid, sensitive, and accurate identification of the TS genotypes (VNTRs, SNPs, and FLP). PMID:17369151

Zhang, Xiao-Mei; Chen, Sen-Qing; Cao, Hai-Xia; Wu, Jian-Zhong; Ma, Guo-Jian; Li, Jin-Tian

2007-03-01

283

Cold crystallisation behaviour of water molecules in ionic liquids as a screening method to evaluate biocompatibility of the hydrated ionic liquids.  

PubMed

Hydrated ionic liquids, exhibiting cold crystallisation behaviour of water molecules in a certain range of water contents, successfully dissolved cytochrome c maintaining the original spin state of heme. PMID:23486783

Fujita, Kyoko; Nikawa, Yohsuke; Ohno, Hiroyuki

2013-04-21

284

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

285

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

286

Nature of the asymmetry in the hydrogen-bond networks of hexagonal ice and liquid water.  

PubMed

The interpretation of the X-ray spectra of water as evidence for its asymmetric structure has challenged the traditional nearly tetrahedral model and initiated an intense debate about the order and symmetry of the hydrogen-bond network in water. Here, we present new insights into the nature of local interactions in ice and liquid water obtained using a first-principle energy decomposition method. A comparative analysis shows that the majority of molecules in liquid water in our simulation exhibit hydrogen-bonding energy patterns similar to those in ice and retain the four-fold coordination with only moderately distorted tetrahedral configurations. Although this result indicates that the traditional description of liquid water is fundamentally correct, our study also demonstrates that for a significant fraction of molecules the hydrogen-bonding environments are highly asymmetric with extremely weak and distorted bonds. PMID:24521433

Kühne, Thomas D; Khaliullin, Rustam Z

2014-03-01

287

A procedure for determination of cobalt in water samples after dispersive liquid–liquid microextraction  

Microsoft Academic Search

In this work, a procedure for preconcentration of cobalt using dispersive liquid–liquid microextraction (DLLME) with the reagent Br-TAO as complexing reagent was developed. The procedure is based on a ternary system of solvents, where appropriate amounts of the extraction solvent, disperser solvent and the chelating agent Br-TAO are directly injected into an aqueous solution containing Co(II). A cloudy mixture is

Patrícia Xavier Baliza; Leonardo Sena Gomes Teixeira; Valfredo Azevedo Lemos

2009-01-01

288

Polymorphism of triphenyl phosphite  

NASA Astrophysics Data System (ADS)

The glass-forming liquid triphenyl phosphite (TPP) has recently attracted much attention due to the possible existence of a polyamorphism, i.e., the existence of two or more amorphous phases. In the present work we provide experimental evidence of the existence of a polymorphism in TPP. In addition to the already known conventional crystalline phase, which melts at 299.1 K, it has been found that TPP can crystallize in another polymorphic phase. The new polymorph can be obtained from the liquid phase due to direct cooling from the room temperature up to 245 K where it is held for 15 min and then heated up to 270 K. At 270 K crystallization of the new polymorph occurs, which melts at 291.6 K.

Baran, J.; Davydova, N. A.; Drozd, M.

2014-03-01

289

Polymorphism of triphenyl phosphite.  

PubMed

The glass-forming liquid triphenyl phosphite (TPP) has recently attracted much attention due to the possible existence of a polyamorphism, i.e., the existence of two or more amorphous phases. In the present work we provide experimental evidence of the existence of a polymorphism in TPP. In addition to the already known conventional crystalline phase, which melts at 299.1 K, it has been found that TPP can crystallize in another polymorphic phase. The new polymorph can be obtained from the liquid phase due to direct cooling from the room temperature up to 245 K where it is held for 15 min and then heated up to 270 K. At 270 K crystallization of the new polymorph occurs, which melts at 291.6 K. PMID:24628187

Baran, J; Davydova, N A; Drozd, M

2014-03-14

290

Surface relaxation in liquid water and methanol studied by x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

X-ray absorption spectroscopy is a powerful probe of local electronic structure in disordered media. By employing extended x-ray absorption fine structure spectroscopy of liquid microjets, the intermolecular O-O distance has been observed to undergo a 5.9% expansion at the liquid water interface, in contrast to liquid methanol for which there is a 4.6% surface contraction. Despite the similar properties of liquid water and methanol (e.g., abnormal heats of vaporization, boiling points, dipole moments, etc.), this result implies dramatic differences in the surface hydrogen bond structure, which is evidenced by the difference in surface tension of these liquids. This result is consistent with surface vibrational spectroscopy, which indicates both stronger hydrogen bonding and polar ordering at the methanol surface as a consequence of "hydrophobic packing" of the methyl group.

Wilson, Kevin R.; Schaller, R. D.; Co, D. T.; Saykally, R. J.; Rude, Bruce S.; Catalano, T.; Bozek, J. D.

2002-10-01

291

Low toxic dispersive liquid-liquid microextraction using halosolvents for extraction of polycyclic aromatic hydrocarbons in water samples.  

PubMed

A low toxic dispersive liquid-liquid microextraction (LT-DLLME) combined with gas chromatography-mass spectrometry (GC-MS) had been developed for the extraction and determination of 16 polycyclic aromatic hydrocarbons (PAHs) in water samples. In normal DLLME assay, chlorosolvent had been widely used as extraction solvents; however, these solvents are environmental-unfriendly. In order to solve this problem, we proposed to use low toxic bromosolvent (1-bromo-3-methylbutane, LD(50) 6150mg/kg) as the extraction solvent. In this study we compared the extraction efficiency of five chlorosolvents and thirteen bromo/iodo solvents. The results indicated that some of the bromo/iodo solvents showed better extraction and had much lower toxicity than chlorosolvents. We also found that propionic acid is used as the disperser solvent, as little as 50microL is effective. Under optimum conditions, the range of enrichment factors and extraction recoveries of tap water samples are ranging 372-1308 and 87-105%, respectively. The linear range is wide (0.01-10.00microgL(-1)), and the limits of detection are between 0.0003 and 0.0078microgL(-1) for most of the analytes. The relative standard deviations (RSD) for 0.01microgL(-1) of PAHs in tap water were in the range of 5.1-10.0%. The performance of the method was gauged by analyzing samples of tap water, sea water and lake water samples. PMID:20663510

Leong, Mei-I; Chang, Chu-Chi; Fuh, Ming-Ren; Huang, Shang-Da

2010-08-20

292

The liquid hydrogen iodide decomposition process step for water-splitting applications  

NASA Astrophysics Data System (ADS)

The reported studies are concerned with the optimization of the sulfur-iodine cycle used to obtain hydrogen from water. According to this cycle, sulfur dioxide reacts with iodine and water to form sulfuric acid and hydrogen iodide. Hydrogen and iodine are obtained as a result of the decomposition of HI. The homogeneous decomposition of HI could be used directly in a thermochemical process to split water. However, the temperature required would be relatively high. Catalyst utilization allows substantial temperature reduction for the same conversion rate. The decomposition of liquid HI is studied as another approach for enhancing HI conversion. A process step for liquid HI decomposition employing HI-I2 distillation is considered along with a process step for liquid HI decomposition employing I2 precipitation. The theoretical investigations were supplemented by precursory experimental studies to establish more fully the engineering viability of liquid HI decomposition.

Okeefe, D. R.; Norman, J. H.

293

Simple, rapid, and sensitive determination of beta-blockers in environmental water using dispersive liquid-liquid microextraction followed by liquid chromatography with fluorescence detection.  

PubMed

A novel method, dispersive liquid-liquid microextraction combined with liquid chromatography-fluorescence detection is proposed for the determination of three beta-blockers (metoprolol, bisoprolol, and betaxolol) in ground water, river water, and bottled mineral water. Some important parameters, such as the kind and volume of extraction and dispersive solvents, extraction time, pH, and salt effect were investigated and optimized. In the method, a suitable mixture of extraction solvent (60 ?L carbon tetrachloride) and dispersive solvent (1 mL acetonitrile) were injected into the aqueous samples (5.00 mL) and the cloudy solution was observed. After centrifugation, the enriched analytes in the bottom CCl(4) phase were determined by liquid chromatography with fluorescence detection. Under the optimum conditions, the enrichment factors (EFs) for metoprolol, bisoprolol, and betaxolol were 180, 190, and 182, and the limits of detection (LODs) were 1.8, 1.4, and 1.0 ng L(-1) , respectively. A good linear relationship between the peak area and the concentration of analytes was obtained in the range of 3-150 ng L(-1) . The relative standard deviations (RSDs) for the extraction of 10 ng L(-1) of beta-blockers were in the range of 4.6-5.7% (n = 5). Compared with other methods, dispersive liquid-liquid microextraction is a very simple, rapid, sensitive (low limit of detection), and economical (only 1.06 mL volume of organic solvent) method, which is in compliance with the requirements of green analytical methodologies. PMID:22887596

Parrilla Vázquez, María del Mar; Parrilla Vázquez, Piedad; Martínez Galera, Maria; Molina Sánchez, Luis

2012-09-01

294

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

295

Retrieving Liquid Water Path and Precipitable Water Vapor from the Atmospheric Radiation Measurement (ARM) Microwave Radiometers  

SciTech Connect

Ground-based two-channel microwave radiometers have been used for over 15 years by the Atmospheric Radiation Measurement (ARM) program to provide observations of downwelling emitted radiance from which precipitable water vapor (PWV) and liquid water path (LWP) – twp geophysical parameters critical for many areas of atmospheric research – are retrieved. An algorithm that utilizes two advanced retrieval techniques, a computationally expensive physical-iterative approach and an efficient statistical method, has been developed to retrieve these parameters. An important component of this Microwave Retrieval (MWRRET) algorithm is the determination of small (< 1K) offsets that are subtracted from the observed brightness temperatures before the retrievals are performed. Accounting for these offsets removes systematic biases from the observations and/or the model spectroscopy necessary for the retrieval, significantly reducing the systematic biases in the retrieved LWP. The MWRRET algorithm provides significantly more accurate retrievals than the original ARM statistical retrieval which uses monthly retrieval coefficients. By combining the two retrieval methods with the application of brightness temperature offsets to reduce the spurious LWP bias in clear skies, the MWRRET algorithm provides significantly better retrievals of PWV and LWP from the ARM 2-channel microwave radiometers compared to the original ARM product.

Turner, David D.; Clough, Shepard A.; Liljegren, James C.; Clothiaux, Eugene E.; Cady-Pereira, Karen E.; Gaustad, Krista L.

2007-11-01

296

Liquid ordering at the Brushite- { 010 } water interface  

NASA Astrophysics Data System (ADS)

Using surface x-ray diffraction, we have determined the atomic structure of the { 010 } interface of brushite, CaHPO4 ·2 ( H2 O ) , with water. Since this biomineral contains water layers as part of its crystal structure, special ordering properties at the interface are expected. We found that this interface consists of two water bilayers with different ordering properties. The first water bilayer is highly ordered and can be considered as part of the brushite crystal structure. Surprisingly, the second water bilayer exhibits no in-plane order, but shows only layering in the perpendicular direction. We propose that the low level of water ordering at the interface is correlated with the low solubility of brushite in water.

Arsic, J.; Kaminski, D.; Poodt, P.; Vlieg, E.

2004-06-01

297

Liquid-liquid equilibria of the ternary systems water + acetic acid + ethyl acetate and water + acetic acid + isophorene (3,5,5-trimethyl-2-cyclohexen-1-one)  

SciTech Connect

Liquid-liquid equilibria for the ternary systems water + acetic acid + ethyl acetate and water + acetic acid + isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) were measured over the temperature range (283 to 313) K. The results were used to estimate the interaction parameters between each of the three compounds of the systems studied for the NRTL and UNIQUAC models. The estimated interaction parameters were successfully used to predict the equilibrium compositions by the two models; experimental data were successfully reproduced. The UNIQUAC model was the most accurate in correlating the overall equilibrium composition of the studied systems. Also the NRTL model satisfactorily predicted the equilibrium composition. Isophorone experimentally resulted in a better extraction capacity for acetic acid and in a lower miscibility with water.

Colombo, A.; Battilana, P.; Ragaini, V.; Bianchi, C.L. [Milan Univ. (Italy). Dept. of Physical Chemistry and Electrochemistry] [Milan Univ. (Italy). Dept. of Physical Chemistry and Electrochemistry; Carvoli, G. [Chemial S.p.A., Cavaglia (Italy)] [Chemial S.p.A., Cavaglia (Italy)

1999-01-01

298

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

299

ANALYSIS OF LIQUID CRYOGEN-WATER EXPERIMENTS WITH THE MELCOR CODE  

Microsoft Academic Search

Vapor explosions are processes involving significant energy exchange between a hot and colder, more volatile liquid. This phenomenon can cause significant pressurization and may cause damage to structures. Historically, vapor explosions have been of interest in industrial processes with molten metals, and postulated accident scenarios involving molten fuel and water in current light water reactors. With the potential use of

R. C. Duckworth; J. G. Murphy; T. T. Utschig; M. L. Corradini; B. J. Merrill; R. L. Moore

300

Hydrogen Isotope Separation by Catalyzed Exchange Between Hydrogen and Liquid Water  

Microsoft Academic Search

The discovery, at Chalk River Nuclear Laboratories, of a simple method of wetproofing platinum catalysts so that they retain their activity in liquid water stimulated a concentrated research program for the development of catalysts for the hydrogen-water isotopic exchange reaction. This paper reviews 10 years of study which have resulted in the development of highly active platinum catalysts which remain

J. P. Butler

1980-01-01

301

Methanol and water crossover in a passive liquid-feed direct methanol fuel cell  

Microsoft Academic Search

Methanol crossover, water crossover, and fuel efficiency for a passive liquid-feed direct methanol fuel cell (DMFC) were all experimentally determined based on the mass balance of the cell discharged under different current loads. The effects of different operating conditions such as current density and methanol concentration, as well as the addition of a hydrophobic water management layer, on the methanol

Chao Xu; Amir Faghri; Xianglin Li; Travis Ward

2010-01-01

302

Ultrafast Conversions Between Hydrogen Bonded Structures in Liquid Water Observed by Femtosecond X-Ray Spectroscopy.  

National Technical Information Service (NTIS)

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 ...

A. M. Lindenberg H. Wen N. Huse R. W. Schoenlein

2010-01-01

303

Distribution of the liquid aerosol produced from bursting bubbles in sea and distilled water  

Microsoft Academic Search

Laser holographic techniques are used to observe and measure the liquid droplets (film drops) produced by air bubbles bursting in both seawater and distilled water. Film drop aerosol production is found not only to be a function of parent bubble size but also of the type of water (sea or distilled) in which the bubbles burst. For bubbles in the

G. M. Afeti; F. J. Resch

1990-01-01

304

Development of liquid and gas chromatographic methods for the determination of water.  

National Technical Information Service (NTIS)

Two liquid chromatographic (LC) methods and one gas chromatographic (GC) method for the determination of water are developed. In the LC methods, water in various analytical samples is separated from the sample matrices on either a single cation-exchange c...

J. Chen

1991-01-01

305

Low cost methodology for estrogens monitoring in water samples using dispersive liquid-liquid microextraction and HPLC with fluorescence detection.  

PubMed

A new low cost methodology for estrogens' analysis in water samples was developed in this work. Based on dispersive liquid-liquid microextraction followed by high-performance liquid chromatography with fluorescence detection, the developed method is fast, cheap, easy-to-use, uses low volumes of organic solvents and has the possibility of a large number of samples to be extracted in parallel. Under optimum conditions (sample volume: 8 mL; extraction solvent: 200 ?L of chlorobenzene; dispersive solvent: 2000 ?L of acetone), the enrichment factor and extraction recoveries were 145 and 72% for 17?-estradiol (E2) and 178 and 89% for 17?-ethinylestradiol (EE2), respectively. Limits of detection of 2.0 ng L(-1) for E2 and 6.5 ng L(-1) for EE2 were achieved, allowing the detection and quantification of these compounds in surface and waste water samples with concentrations from 12 to 32 ng L(-1) for E2 and from 11 to 18 ng L(-1) for EE2. Also, recovery tests were performed to evaluate possible matrix effects. Recoveries between 98% and 106% were obtained using humic acids (HA) to simulate the effect of organic matter, and between 86% and 120% in real water samples. PMID:24054691

Lima, Diana L D; Silva, Carla Patrícia; Otero, Marta; Esteves, Valdemar I

2013-10-15

306

Deliquescence, liquid water, and the search for sources and sinks of methane on Mars  

NASA Astrophysics Data System (ADS)

The recent discoveries of evidence for liquid saline water1,2,3,4 and methane5 on Mars have excited the science community by reviving the possibility of extant microbial life in this nearby planet. Here we report recently discovered photometric and spectral evidence that liquid saline water exists on Mars4. We show that this finding indicates that deliquescence occurs seasonally on some areas of Mars' polar region4. These discoveries support the hypothesis that liquid saline water is ubiquitous in the shallow Martian subsurface. This has important implications for the search for extraterrestrial life because a diverse array of terrestrial microorganisms thrives in highly saline water or brines6,7. We conclude this article by describing in situ and remote sensing instruments for detecting brines in the Martian subsurface and studying their relationship with sources and sinks of trace gases.

Rennó, N. O.; Mehta, M.

2010-08-01

307

Mesoscopic modeling of liquid water transport in polymer electrolyte fuel cells  

SciTech Connect

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

Mukherjee, Partha P [Los Alamos National Laboratory; Wang, Chao Yang [PENNSTATE UNIV.

2008-01-01

308

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

SciTech Connect

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

Tailor, Ramesh; Ibbott, Geoffrey; Lampe, Stephanie; Bivens Warren, Whitney; Tolani, Naresh [Radiation Physics, UT MD Anderson Cancer Center, 1515 Holcombe Boulevard, Box 94, Houston, Texas 77030 (United States); Radiological Physics Center, UT M.D. Anderson Cancer Center, 7515 Main Street, Suite 300, Houston, Texas 77030-4519 (United States); Radiation Physics, M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 94, Houston, Texas 77030 (United States); Harrington Cancer Center, 1500 Wallace Boulevard, Amarillo, Texas 76106 (United States); Radiation Physics, U.T. M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 94, Houston, Texas 77030 (United States)

2008-12-15

309

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

310

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

311

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

SciTech Connect

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.

Wu, X.; Diak, G.R.; Hayden, C.M.; Young, J.A. [Univ. of Wisconsin, Madison, WI (United States)] [Univ. of Wisconsin, Madison, WI (United States)

1995-02-01

312

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

313

Enhancement of atmospheric liquid water estimation using space-borne remote sensing data  

NASA Astrophysics Data System (ADS)

Clouds strongly affect the energy balance and water cycle, two dominant processes in the climate system. Low-level liquid clouds have the most significant influence on cloud radiative forcing due to their areal extent and frequency. Estimation of atmospheric liquid water contained in low-level clouds and the precipitation underneath them is very important in meteorology, hydrology, and climatology. Space-borne remote sensing data are widely used for global estimation of atmospheric liquid water, given that they have a wider spatial coverage than other data sources and are spanning many years. However, previous space-borne remote sensing techniques have some limitations for estimation of atmospheric liquid water in low-level liquid clouds, namely, the vertical variation of droplet effective radius (DER) is neglected in the calculation of cloud liquid water path (LWP) and the rain underneath low-level liquid clouds can be overlooked. Comprising many state-of-art passive and active instruments, the recently launched NASA A-Train series of satellites provides comprehensive simultaneous information about cloud and precipitation processes. Utilizing A-Train satellite data and ship-borne data from the East Pacific Investigation of Climate (EPIC) campaign, in this study investigated is the estimation of liquid water in low-level liquid clouds, and assessed is the potential of cloud microphysical parameters in the estimation of rain from low-level liquid clouds. This study demonstrates that assuming a constant cloud DER can cause biases in the calculation of LWP. It is also shown that accounting for the vertical variation of DER can reduce the mean biases. This study shows that DER generally increases with height in non-drizzling clouds, consistent with aircraft observations. It is found that in drizzling clouds, the vertical gradient of DER is significantly smaller than that in non-drizzling clouds, and it can become negative when the drizzle is heavier than approximately 0.1 mm hr-1. It is shown that the warm rain underneath low-level liquid clouds accounts for 45.0% of occurrences of rain and 27.5% of the rainfall amount over the global ocean areas. Passive microwave techniques underestimate the warm rain over oceans by nearly 48%. Among the cloud microphysical parameters, LWP calculated with DER profile shows the best potential for estimating warm rain, which is neglected by traditional techniques of precipitation estimation.

Chen, Ruiyue

314

Investigation on isobaric vapor–liquid equilibrium for acetic acid + water + methyl ethyl ketone + isopropyl acetate  

Microsoft Academic Search

Isobaric vapor–liquid equilibrium (VLE) data for acetic acid+water, acetic acid+methyl ethyl ketone (MEK), MEK+isopropyl acetate, acetic acid+MEK+water and acetic acid+MEK+isopropyl acetate+water are measured at 101.33kPa using a modified Rose cell. The nonideal behavior in vapor phase of binary systems measured in this work is analyzed through calculating fugacity coefficients since mixture containing acetic acid deviates from ideal behavior seriously in

Qiang Xie; Hui Wan; MingJuan Han; GuoFeng Guan

2009-01-01

315

Vapor-liquid equilibrium and density measurements of tetraalklylammonium bromide + propanol + water systems  

Microsoft Academic Search

Isobaric vapor-liquid equilibrium (VLE) measurements at atmospheric pressure were made for 1.0--3.0 m tetrapropylammonium bromide (TPAB) and 3.0 m tetrabutylammonium bromide (TBAB) in mixtures of 2-propanol and water, and 3.0 m TPAB and 3.0 m TBAB in mixtures of 1-propanol and water. In addition, VLE measurements were made on 3.0 m TBAB in 2-propanol + water mixtures at 0.080 bar.

Joseph T. Slusher; Peter T. Cummings; Yeqiong Hu; Carmen A. Vega; John P. O'Connell

1995-01-01

316

Energy Equilibrium and Conversion on Supercritical Water Oxidation of Organic Liquid-Waste  

Microsoft Academic Search

Supercritical water oxidation (SCWO) was first proposed almost 20 years ago as a potential organic waste treatment technology. In this paper, the energy-conversion system of supercritical water oxidation is built up in terms of a transpiring-wall reactor, in which the glucose-water solution is used to mimic the organic liquid-waste. Additionally, considering mass and energy conservations, the calculation on its energy

Shouyan Chen; Chunyuan Ma; Zhiqiang Wang; Gui-fang Chen; Fengming Zhang; Xiaofang Shen

2010-01-01

317

Optical and topographic changes in water-responsive patterned cholesteric liquid crystalline polymer coatings  

NASA Astrophysics Data System (ADS)

In this work, we present patterned water-responsive coatings, which alter both their topological and optical properties. The polymer coatings are based on a hydrogen-bonded cholesteric liquid crystalline polymer network. A two-step photopolymerization procedure leads to a patterned coating with repeating liquid crystalline and isotropic areas. The cholesteric liquid crystalline areas reflect green light, whilst the isotropic areas are transparent for visible light. Treatment with alkaline solution results in a hygroscopic polymer salt coating. When placed in demineralized water, the polymer films swells, leading to an enhancement of the surface topography structure in which the liquid crystalline areas swell more. Moreover, the pitch of the helical organization in the cholesteric areas increases due to this swelling leading to a color change from green to red.

Stumpel, Jelle E.; Broer, Dirk J.; Bastiaansen, Cees W. M.; Schenning, Albert P. H. J.

2014-05-01

318

Water-aromatic liquid-liquid-vapour equilibrium calculation using a cubic equation of state  

NASA Astrophysics Data System (ADS)

This paper presents an extension of the procedure developed in the case of water-alkane binaries to mixtures of water and benzene or toluene or xylene or ethylbenzene or diethylbenzene. The method used to calculate the equilibria is based on the Peng-Robinson cubic equation of state modified as regards the coefficient ?( Tr) and on the use of a binary interaction coefficient k iw specific to binaries containing water.

Gao, Guanghua; Daridon, J. L.; Lagourette, B.; Xans, P.

1994-09-01

319

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

320

Validation of total water vapor and liquid water algorithm for the ADEOS-II\\/AMSR: using SSM\\/I observations  

Microsoft Academic Search

The simulated brightness temperatures, TB, at two channels of the Advanced Microwave Scanning Radiometer (AMSR) system on the ADEOS-II satellite (frequencies of 23.8 and 36.5 GHz at vertical polarization) were used to develop a physical technique to simultaneously retrieve total atmospheric water vapor content and total cloud liquid water content for nonprecipitating conditions over the ocean. Coefficients and approximation functions

Maia Mitnik; Leonid Mitnik

1998-01-01

321

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

PubMed

Ionic liquid-dispersive liquid-liquid microextraction combined with micro-solid phase extraction (IL-DLLME-?-SPE), and high-performance liquid chromatography (HPLC) was developed for the determination of tricyclic antidepressants (TCAs) in water samples. Two hundred microliters of an organic solvent (as disperser solvent) and 20 ?l of 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate were injected into a 5.0 ml sample for sonication-assisted DLLME. After this, a ?-SPE device, containing a novel material zeolite imidazolate framework 4 (ZIF-4), was added into the sample solution and 1 min of vortex-assisted extraction was performed. After 5 min of sonication-assisted desorption, 10 ?l of desorption solvent was injected into a HPLC system for analysis. A characteristic property of DLLME-VA-?-SPE is that any organic solvent and solid sorbent immiscible with water can be used. Special apparatus, or conical-bottom test tubes, and tedious procedures conventionally associated with DLLME such as centrifugation, or refrigeration of solvent are not necessary in the present approach. A novel material, ZIF-4 was employed as ?-SPE sorbent. Under the optimized conditions, the calibration curves were linear in the range of 1-1000 ?g/L. The relative standard deviations and the limits of detection were in the range of 1.5% and 7.8% and 0.3 and 1 ?g/L, respectively. The relative recoveries of canal water samples, spiked with drugs, were in the range of 94.3% and 114.7%. The results showed that IL-DLLME-?-SPE was suitable for the determination of TCAs in water samples. PMID:23639124

Ge, Dandan; Lee, Hian Kee

2013-11-22

322

Improved energy efficiency in absorption heat pump through process modification. Part II: Thermodynamic potential of liquid-liquid extraction of ammonia-water mixtures  

Microsoft Academic Search

Extraction-system-attached (ESA) ammonia-water absorption heat pumps were derived from the conventional system as a strategy to improve the energy efficiency of the conventional ammonia-water absorption heat pump. The ESA absorption heat pumps were obtained by attaching a liquid-liquid extraction unit in the conventional system. Theoretical thermodynamic simulation of the ESA and conventional ammonia-water absorption heat pumps showed that a higher

A. S. Olawale; S. S. Adefila

1998-01-01

323

Frustration and anomalous behavior in the Bell-Lavis model of liquid water.  

PubMed

We have reconsidered the Bell-Lavis model of liquid water and investigated its relation to its isotropic version, the antiferromagnetic Blume-Emery-Griffiths model on the triangular lattice. Our study was carried out by means of an exact solution on the sequential Husimi cactus. We show that the ground states of both models share the same topology and that fluid phases (gas and low- and high-density liquids) can be mapped onto magnetic phases (paramagnetic, antiferromagnetic, and dense paramagnetic, respectively). Both models present liquid-liquid coexistence and several thermodynamic anomalies. This result suggests that anisotropy introduced through orientational variables play no specific role in producing the density anomaly, in agreement with a similar conclusion discussed previously following results for continuous soft core models. We propose that the presence of liquid anomalies may be related to energetic frustration, a feature common to both models. PMID:18643057

Barbosa, Marco Aurélio Alves; Henriques, Vera Bohomoletz

2008-05-01

324

Frustration and anomalous behavior in the Bell-Lavis model of liquid water  

NASA Astrophysics Data System (ADS)

We have reconsidered the Bell-Lavis model of liquid water and investigated its relation to its isotropic version, the antiferromagnetic Blume-Emery-Griffiths model on the triangular lattice. Our study was carried out by means of an exact solution on the sequential Husimi cactus. We show that the ground states of both models share the same topology and that fluid phases (gas and low- and high-density liquids) can be mapped onto magnetic phases (paramagnetic, antiferromagnetic, and dense paramagnetic, respectively). Both models present liquid-liquid coexistence and several thermodynamic anomalies. This result suggests that anisotropy introduced through orientational variables play no specific role in producing the density anomaly, in agreement with a similar conclusion discussed previously following results for continuous soft core models. We propose that the presence of liquid anomalies may be related to energetic frustration, a feature common to both models.

Barbosa, Marco Aurélio Alves; Henriques, Vera Bohomoletz

2008-05-01

325

Effect of calcium chloride on the isobaric vapor-liquid equilibrium of 1-propanol + water  

SciTech Connect

The effect of calcium chloride at salt mole fractions from 0.02 to saturation on the vapor-liquid equilibrium (VLE) of 1-propanol + water has been studied at 101.32 kPa using a modified Othmer equilibrium still. The salt exhibited a salting-out effect of the alcohol over the whole range of liquid composition, the azeotrope being eliminated at salt mole fractions greater than 0.080. A liquid phase splitting into two immiscible liquid phases on the whole range of salt concentration and over a liquid range of about 0.01--0.54 1-propanol mole fraction (salt-free basis) was observed. The results were compared with the values predicted from the extended UNIQUAC models of Sander et al. and Macedo et al. and the modified UNIFAC group-contribution model of Kikic et al.

Iliuta, M.C.; Thyrion, F.C. [Louvain Univ., Louvain-la-Neuve (Belgium). Chemical Engineering Inst.] [Louvain Univ., Louvain-la-Neuve (Belgium). Chemical Engineering Inst.; Landauer, O.M. [Univ. Politehnica Bucharest (Romania)] [Univ. Politehnica Bucharest (Romania)

1996-05-01

326

Mineral Specific IR Molar Absorption Coefficients for Routine Water Determination in Olivine, SiO2 polymorphs and Garnet  

NASA Astrophysics Data System (ADS)

Conventionally applied Infrared (IR) calibrations [1, 2] for quantitative water analyses in solids are established on hydrous minerals and glasses with several wt% water. These calibrations are based on a negative correlation between the IR molar absorption coefficient (?) for water and the mean wavenumber of the corresponding OH pattern. The correlation reflects the dependence of the OH band position on the appropriate O- H...O distances and thereby the magnitude of the dipole momentum which is proportional to the band intensity. However, it has been observed that these calibrations can not be adopted to nominally anhydrous minerals (NAMs) [3].To study the potential dependence of ? on structure and chemistry in NAMs we synthesized olivine and SiO2 polymorphs with specific isolated hydroxyl point defects, e.g. quartz, coesite and stishovite with B3++H+=Si4+ and/or Al3++H+=Si4+ substitutions. Experiments were performed with water in excess in piston cylinder and multi-anvil presses. Single crystal IR spectra demonstrate that we successfully managed to seperate generally complex OH patterns as e.g. observed in natural quartz and synthetic coesite. We quantified sample water contents of both natural samples and our run products by applying proton-proton-scattering [4], confocal microRaman spectroscopy [5] and Secondary Ion mass spectrometry. Resulting water concentrations were used to calculate new mineral specific ?s. For olivine with the mean wavenumber of 3517 cm-1 we determined an ? value of 41,000±5,000 lmol-1H2Ocm-2. Quantification of olivine with the mean wavenumber of 3550 cm-1 in contrast resulted in an ? value of 47,000±1,000 lmol-1H2Ocm-2. Taking into account previous studies [6, 7] there is evidence to suggest a linear wavenumber dependent correlation for olivine, where ? increases with decreasing wavenumber. In case of the SiO2 system it turns out that the magnitude of ? within one structure type is independent of the liable OH point defect and therewith the wavenumber of the observed band position. Consequently, one single mean ? of 68,000±5,000 lmol-1H2Ocm-2 could be determined for a suite of quartz samples with varying OH point defects. In contrast, ? varies with the structure itself. For polymorphic coesite we calculated a different ? of 214,000±8,000 lmol-1H2O}cm-2, that is in good agreement with earlier established data [8]. Quantification data of stishovite resulted in an even higher value of ?=867,000±29,000 lmol-1H2Ocm-2, similar to that determined by [9]. First data on natural garnet give an ? value of 40,000±2,000 lmol-1H2Ocm-2, that confirms prior suggested values [10]. Our results demonstrate that not using mineral specific calibrations for quantitative water analyses in NAMs leads to overestimation of sample water concentrations, that are required for modelling the earth's deep water cycle. [1]Paterson, M. S. (1982), Bull. Min., 105, 20-29. [2]Libowitzky, E., Rossman, G. R. (1997), Am. Min., 82, 1111- 1115. [3]Rossman, G. R. (2006), Rev. Mineral., 62, 1-28. [4]Reichart et al. (2004), Science, 306, 1537-1540. [5]Thomas et al. (2006), Am. Min., 91, 467-470. [6]Bell et al. (2003), JGR, 108, (B2), 2105-2113. [7]Koch-Mueller et al. (2006), PCM, 33, 276-287. [8]Koch-Mueller et al. (2001), PCM, 28, 693-705. [9]Pawley et al. (1993), Science, 261, 1024-1026. [10]Maldener et al. (2003), PCM, 30, 337-344.

Thomas, S.; Koch-Mueller, M.; Reichart, P.; Rhede, D.; Thomas, R.

2007-12-01

327

Vapor-liquid equilibria for the binary monoethanolamine+ water and monoethanolamine+ethanol systems  

Microsoft Academic Search

Isobaric vapor-liquid equilibrium data for monocthanolamine (MEA)+water and monoethanolamine (MEA)+ ethanol were measured\\u000a in an equilibrium cell circulating both the vapor and liquid phases. The measurements of the boiling temperatures and corresponding\\u000a equilibrium compositions for two binary mixtures were carried out at the atmospheric pressure. The results were checked for\\u000a thermodynamic consistency by the point test method. The activity coefficients

Sung-Bum Park; Huen Lee

1997-01-01

328

Equation of state of ammonia-water liquid - derivation and planetological applications  

Microsoft Academic Search

The present least-squares fit calculation of the equation of state for ammonia-water liquid has yielded results for the zero-100 wt pct NH3, 170-300 K temperature, and zero-10 kb pressure parameter ranges. In conjunction with solid density and thermodynamic measurements, the present calculated and measured liquid densities are used to yield estimates of density and thermal expansion at 1 bar for

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

1988-01-01

329

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

Microsoft Academic Search

The present least-squares fit calculation of the equation of state for ammonia-water liquid has yielded results for the zero-100 wt pct NH3, 170-300 K temperature, and zero-10 kb pressure parameter ranges. In conjunction with solid density and thermodynamic measurements, the present calculated and measured liquid densities are used to yield estimates of density and thermal expansion at 1 bar for

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

1988-01-01

330

Effect of calcium chloride on the isobaric vapor-liquid equilibrium of 1-propanol + water  

Microsoft Academic Search

The effect of calcium chloride at salt mole fractions from 0.02 to saturation on the vapor-liquid equilibrium (VLE) of 1-propanol + water has been studied at 101.32 kPa using a modified Othmer equilibrium still. The salt exhibited a salting-out effect of the alcohol over the whole range of liquid composition, the azeotrope being eliminated at salt mole fractions greater than

Maria C. Iliuta; Fernand C. Thyrion; Ortansa M. Landauer

1996-01-01

331

Liquid and gas velocity measurements using LDV in air–water duct flow  

Microsoft Academic Search

Simultaneous measurements of liquid and gas velocity have been made in an air–water two-phase flow in a rectangular vertical duct. A forward\\/backward scattering Laser Doppler Velocimeter (LDV) with amplitude discrimination was used to measure each of the two phasic velocities. High speed photography and hot-film anemometry were used to confirm the gas and liquid velocities respectively. Transverse velocity profiles were

Peter F Vassallo; Ranganathan Kumar

1999-01-01

332

Dialkylimidazolium ionic liquids as electrolytes for hydrogen production from water electrolysis  

Microsoft Academic Search

Imidazolium ionic liquids (ILs) such as BMI·BF4 and BMI·PF6 were studied by cyclic voltammetry (CV). BMI·BF4 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. Gonçalves; Joëlle Rault-Berthelot

2006-01-01

333

A dispersive liquid-liquid microextraction procedure for determination of boron in water after ultrasound-assisted conversion to tetrafluoroborate.  

PubMed

A novel, simple and green procedure is presented for the determination of boron. The method is based on ultrasound-assisted conversion of boron to tetrafluoroborate anion and the formation of an ion pair between BF(4)(-) and Astra Phloxine reagent (R), followed by dispersive liquid-liquid microextraction of the ion pair formed and subsequent UV-vis spectrophotometric detection. The conversion of boron to tetrafluoroborate anion is performed in an acidic medium of 0.9 mol L(-1) H(2)SO(4) in the presence of 0.1 mol L(-1)F(-) by means of 10 min of ultrasonication. The extraction of the ion pair formed between BF(4)(-) and R (1×10(-4)mol L(-1)R) is carried out by dispersive liquid-liquid microextraction using 0.5 mL of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as dispersive solvent) in a ratio of 1:1:2. The absorbance of the coloured extracts obeys Beer's law in the range 0.22-18.7 mg L(-1) of B(III) at 553 nm wavelength. The limit of detection calculated from a blank test (n=10) based on 3s is 0.015 mg L(-1) of B(III). The method was applied to the determination of boron in mineral waters. PMID:21645738

Rusnáková, Lenka; Andruch, Vasil; Balogh, Ioseph S; Skrlíková, Jana

2011-07-15

334

Application of dispersion-solidification liquid-liquid microextraction for the determination of triazole fungicides in environmental water samples by high-performance liquid chromatography.  

PubMed

A simple, rapid and environmentally friendly method has been developed for the determination of four triazole fungicides (myclobutanil, tebuconazole, triadimenol, hexaconazole) in water samples by dispersion-solidification liquid-liquid microextraction coupled with high performance liquid chromatography-diode array detection. Several variables that affect the extraction efficiencies, including the type and volume of the extraction solvent and dispersive solvent, extraction time, effect of pH and salt addition, were investigated and optimized. Under the optimum conditions, the proposed method is sensitive and shows a good linearity within a range of 0.5-200 ng mL(-1), with the correlation coefficients (r) varying from 0.9992 to 0.9998. High enrichment factors were achieved ranging from 190 to 450. The recoveries of the target analytes from water samples at spiking levels of 1.0, 5.0 and 50.0 ng mL(-1) were between 84.8% and 110.2%. The limits of detection (LODs) for the analytes were ranged in 0.06-0.1 ng mL(-1), and the relative standard deviations (RSD) varied from 3.9% to 5.7%. The proposed method has been successfully applied for the determination of the triazole fungicides in real water samples. PMID:20875927

Wang, Chun; Wu, Qiuhua; Wu, Chunxia; Wang, Zhi

2011-01-15

335

Salt-assisted liquid-liquid microextraction with water-miscible organic solvents for the determination of carbonyl compounds by high-performance liquid chromatography.  

PubMed

A simple and rapid method has been reported for the determination of carbonyl compounds involving reaction with 2,4-dinitrophenylhydrazine and extraction of hydrazones with water-miscible organic solvent acetonitrile when the phase separation occurs by addition of ammonium sulphate, a process called salt-assisted liquid-liquid microextraction. The extract was analyzed by high-performance liquid chromatography with UV detection at 360 nm. The procedure has been optimized with respect to solvent suitable for extraction, salt for phase separation between water and organic solvent, reaction temperature and reaction time. The method has been validated when a linear dynamic range was obtained between the amount of analyte and peak area of hydrazones in the range 7 microg-15 mg L(-1), the correlation coefficient over 0.9964-0.9991, and the limit of detection in the range 0.58-3.2 microg L(-1). Spiked water samples have been analyzed with adequate accuracy, and application of the method has been demonstrated in the analysis of benzaldehyde formed as oxidation product in pharmaceutical preparation where benzyl alcohol is used as preservative, and for a keto drug dexketoprofen. PMID:19836515

Gupta, Manju; Jain, Archana; Verma, Krishna K

2009-12-15

336

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

PubMed

A simple ultrasound-assisted dispersive liquid-liquid microextraction method combined with liquid chromatography was developed for the preconcentration and determination of six pyrethroids in river water samples. The procedure was based on a ternary solvent system to formatting tiny droplets of extractant in sample solution by dissolving appropriate amounts of water-immiscible extractant (tetrachloromethane) in watermiscible dispersive solvent (acetone). Various parameters that affected the extraction efficiency (such as type and volume of extraction and dispersive solvent, extraction time, ultrasonic time, and centrifuging time) were evaluated. Under the optimum condition, good linearity was obtained in a range of 0.00059-1.52 mg L(-1) for all analytes with the correlation coefficient (r(2))>0.999. Intra-assay and inter-assay precision evaluated as the relative standard deviation (RSD) were less than 3.4 and 8.9%. The recoveries of six pyrethroids at three spiked levels were in the range of 86.2-109.3% with RSD of less than 8.7%. The enrichment factors for the six pyrethroids were ranged from 767 to 1033 folds. PMID:20580006

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

2010-08-01

337

Thermodynamic Study of Solutions of Liquid Hydrocarbon Mixtures in Water.  

National Technical Information Service (NTIS)

The hydrocarbon solution process in water was studied because it is important in environmental and geological situations. The aqueous solubility of binary hydrocarbon mixtures was determined (n-octane + 1-methylnaphthalene at 20 and 70 C; n-octane + ethyl...

D. R. Burris W. G. MacIntyre

1986-01-01

338

Liquid-liquid equilibria for water + ethanol + 2-methylpropyl ethanoate and water + ethanol + 1,2-dibromoethane at 298. 15 K  

SciTech Connect

Liquid-liquid equilibrium, distribution coefficients, and selectivities of the systems water + ethanol + 2-methylpropyl ethanoate or + 1,2-dibromoethane have been determined at 298.15 K in order to evaluate their suitability in preferentially extracting ethanol from aqueous solution. Tie-line data were satisfactorily correlated by the Othmer and Tobias method, and the plait point coordinates for the two systems were estimated. The experimental data was compared with the values calculated by the NRTL and UNIQUAC models. The water + ethanol + 2-methylpropyl ethanoate system was also compared with the values predicted by the UNIFAC model. Poor qualitative agreement was obtained with these models. From the experimental results, they can conclude that both solvents are inappropriate for ethanol extraction processes from aqueous solutions.

Solimo, H.N.; Barnes de Arreguez, N.G. (Univ. Nacional de Tucuman, San Miguel de Tucuman (Argentina). Inst. de Fisica)

1994-01-01

339

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

340

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

Microsoft Academic Search

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

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

1991-01-01

341

Sodium-water reaction acoustic noise for liquid phase injections. [LMFBR  

SciTech Connect

Data on liquid and steam injections into sodium were recorded during a series of wastage experiments. These data are analyzed for acoustic power and spectral characteristics, expanding the data base up to 10 gm/sec injection rates from the earlier 0.5 gms/sec. No significant difference in acoustic power was measured between low temperature steam and liquid injections for the same mass flowrates. The bandwidth for steam injections is broader than for liquid injections. Reaction product deposition during water injections appears to cause a decrease in signal strength with test duration.

Callis, K.R.; Greene, D.A.; Malovrh, J.W.

1981-02-01

342

Stripping of acetone from water with microfabricated and membrane gas-liquid contactors.  

PubMed

Stripping of acetone from water utilizing nitrogen as a sweeping gas in co-current flow was conducted in a microfabricated glass/silicon gas-liquid contactor. The chip consisted of a microchannel divided into a gas and a liquid chamber by 10 ?m diameter micropillars located next to one of the channel walls. The channel length was 35 mm, the channel width was 220 ?m and the microchannel depth 100 ?m. The micropillars were wetted by the water/acetone solution and formed a 15 ?m liquid film between them and the nearest channel wall, leaving a 195 ?m gap for gas flow. In addition, acetone stripping was performed in a microchannel membrane contactor, utilizing a hydrophobic PTFE membrane placed between two microstructured acrylic plates. Microchannels for gas and liquid flows were machined in the plates and had a depth of 850 ?m and 200 ?m respectively. In both contactors the gas/liquid interface was stabilized: in the glass/silicon contactor by the hydrophilic micropillars, while in the PTFE/acrylic one by the hydrophobic membrane. For both contactors separation efficiency was found to increase by increasing the gas/liquid flow rate ratio, but was not affected when increasing the inlet acetone concentration. Separation was more efficient in the microfabricated contactor due to the very thin liquid layer employed. PMID:24223420

Constantinou, Achilleas; Ghiotto, Francesco; Lam, Koon Fung; Gavriilidis, Asterios

2014-01-01

343

Revisiting the total ion yield x-ray absorption spectra of liquid water microjets  

SciTech Connect

Measurements of the total ion yield (TIY) x-ray absorption spectrum (XAS) of liquid water by Wilson et al. (2002 J. Phys.: Condens. Matter 14 L221 and 2001 J. Phys. Chem. B 105 3346) have been revisited in light of new experimental and theoretical efforts by our group. Previously, the TIY spectrum was interpreted as a distinct measure of the electronic structure of the liquid water surface. However, our new results indicate that the previously obtained spectrum may have suffered from as yet unidentified experimental artifacts. Although computational results indicate that the liquid water surface should exhibit a TIY-XAS that is fundamentally distinguishable from the bulk liquid XAS, the new experimental results suggest that the observable TIY-XAS is actually nearly identical in appearance to the total electron yield (TEY-)XAS, which is a bulk probe. This surprising similarity between the observed TIY-XAS and TEY-XAS likely results from large contributions from x-ray induced electron stimulated desorption of ions, and does not necessarily indicate that the electronic structure of the bulk liquid and liquid surface are identical.

Saykally, Richard J; Cappa, Chris D.; Smith, Jared D.; Wilson, Kevin R.; Saykally, Richard J.

2008-02-16

344

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

PubMed Central

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 (Af) and maximum specific interfacial area (Am) 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.

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

2011-01-01

345

Liquid Water: Obtaining the right answer for the right reasons  

SciTech Connect

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

Apra, Edoardo [ORNL; Harrison, Robert J [ORNL; de Jong, Wibe A [Pacific Northwest National Laboratory (PNNL); Rendell, Alistair P [Australian National University, Canberra, Australia; Tipparaju, Vinod [ORNL; Xantheas, Sotiris [Pacific Northwest National Laboratory (PNNL)

2009-01-01

346

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

PubMed

A novel dispersive liquid-liquid microextraction (DLLME) method followed by HPLC analysis, termed sequential DLLME, was developed for the preconcentration and determination of aryloxyphenoxy-propionate herbicides (i.e. haloxyfop-R-methyl, cyhalofop-butyl, fenoxaprop-P-ethyl, and fluazifop-P-butyl) in aqueous samples. The method is based on the combination of ultrasound-assisted DLLME with in situ ionic liquid (IL) DLLME into one extraction procedure and achieved better performance than widely used DLLME procedures. Chlorobenzene was used as the extraction solvent during the first extraction. Hydrophilic IL 1-octyl-3-methylimidazolium chloride was used as a dispersive solvent during the first extraction and as an extraction solvent during the second extraction after an in situ chloride exchange by bis[(trifluoromethane)sulfonyl]imide. Several experimental parameters affecting the extraction efficiency were studied and optimized with the design of experiments using MINITAB® 16 software. Under the optimized conditions, the extractions resulted in analyte recoveries of 78-91%. The correlation coefficients of the calibration curves ranged from 0.9994 to 0.9997 at concentrations of 10-300, 15-300, and 20-300 ?g L(-1). The relative SDs (n = 5) ranged from 2.9 to 5.4%. The LODs for the four herbicides were between 1.50 and 6.12 ?g L(-1). PMID:23109344

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

2012-12-01

347

Influence of water on the surface of the water-miscible ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate: a sum frequency generation analysis.  

PubMed

Sum frequency generation spectroscopy (SFG) was used to study the influence of water on the surface of the water-miscible ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The orientation of the cation at the gas-liquid interface was analyzed as a function of ionic liquid concentration in water for concentrations from 0 to 1 mole fraction of the ionic liquid. The cation was found to be oriented with the imidazolium ring nearly parallel to the surface plane with a tilt angle > or = 70 degrees when the ionic liquid was dry. Furthermore, no noticeable change in the orientation was observed when high concentrations of water were mixed with the ionic liquid. The cation butyl chain is projecting into the gas phase with a CH(3) tilt angle of 54 +/- 2 degrees when the ionic liquid is dry and 46 +/- 4 degrees when mixed with water. Water is oriented at the surface only for concentration < or = 0.02 mole fraction of the ionic liquid. At higher ionic liquid concentrations (mole fractions > or = 0.05) the gas-liquid interface resembles that of the pure ionic liquid. PMID:16884273

Rivera-Rubero, Selimar; Baldelli, Steven

2006-08-10

348

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

349

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

350

The Association of Liquid Water Springs With Permafrost Regions on Earth and Mars  

NASA Astrophysics Data System (ADS)

Recent space missions have confirmed the presence of ice-rich ground in the middle and high latitudes of Mars. Geologically recent gully features on Mars show a geographic distribution that is correlated with theoretical models of ground ice stability which is suggestive of a genetic relationship between ground ice and gully activity. Possible mechanisms of gully formation are thus examined. A liquid water aquifer on Mars activated by freezing cycles is the favored model of gully formation based on an analysis of Mars Global Surveyor spacecraft data. Additionally, liquid water spring activity occurs in regions of continuous permafrost on Earth. Spring systems in the Canadian High Arctic (Axel Heiberg Island) as well as the Norwegian Arctic (Spitsbergen) demonstrate different morphologies and mechanisms of formation for spring systems in polar desert environments. On both Earth and Mars, liquid water springs in permafrost regions provide a unique setting for the possible preservation of biological signatures.

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

2003-12-01

351

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

352

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

353

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

354

Determination of trace levels of dinitrophenolic compounds by microporous membrane liquid-liquid extraction in environmental water samples.  

PubMed

A fast and simple hollow fibre-based microporous membrane liquid-liquid extraction (MMLLE) method is proposed for the determination of trace levels of dinitrophenolic compounds in water samples. The optimization step was performed using a three-variables Doehlert matrix design, involving the fibre length, the quantity of trioctylphosphine oxide (TOPO) in the acceptor phase and the extraction time. Using the established experimental conditions, some other parameters such as stirring speed, salt content, humic acids and different organic solvents as the acceptor phase were studied. Validation of the method included calibration experiments, linearity studies and determination of method LOD (MLD). The RSD was around 11% in all the experiments on different days at different concentrations. Separation and detection of four dinitrophenols were performed in 10 min with an RP-LC and a C(8 )column ACN-citric buffer gradient elution and diode array detection. PMID:17657827

Bartolomé, Luis; Lezamiz, Jon; Etxebarria, Néstor; Zuloaga, Olatz; Jönsson, Jan Ake

2007-08-01

355

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

356

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: 1.1 10(-) (3) mol L(-1); and ionic liquid: 50.0 mg. Under the optimum conditions, the preconcentration factor obtained was 100. Calibration graph was linear in the range of 0.2-60 µg L(-1) with correlation coefficient of 0.9992. The limit of detection was 0.06 µg L(-) (1), which is lower than other reported approaches applied to the determination of cadmium using FAAS. The relative SD (n = 8) was 2.4%. The proposed method was successfully applied to the determination of trace amounts of cadmium in the real water samples with satisfactory results. PMID:22893353

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

2013-06-01

357

Transcriptome sequencing of Eucalyptus camaldulensis seedlings subjected to water stress reveals functional single nucleotide polymorphisms and genes under selection  

PubMed Central

Background Water stress limits plant survival and production in many parts of the world. Identification of genes and alleles responding to water stress conditions is important in breeding plants better adapted to drought. Currently there are no studies examining the transcriptome wide gene and allelic expression patterns under water stress conditions. We used RNA sequencing (RNA-seq) to identify the candidate genes and alleles and to explore the evolutionary signatures of selection. Results We studied the effect of water stress on gene expression in Eucalyptus camaldulensis seedlings derived from three natural populations. We used reference-guided transcriptome mapping to study gene expression. Several genes showed differential expression between control and stress conditions. Gene ontology (GO) enrichment tests revealed up-regulation of 140 stress-related gene categories and down-regulation of 35 metabolic and cell wall organisation gene categories. More than 190,000 single nucleotide polymorphisms (SNPs) were detected and 2737 of these showed differential allelic expression. Allelic expression of 52% of these variants was correlated with differential gene expression. Signatures of selection patterns were studied by estimating the proportion of nonsynonymous to synonymous substitution rates (Ka/Ks). The average Ka/Ks ratio among the 13,719 genes was 0.39 indicating that most of the genes are under purifying selection. Among the positively selected genes (Ka/Ks > 1.5) apoptosis and cell death categories were enriched. Of the 287 positively selected genes, ninety genes showed differential expression and 27 SNPs from 17 positively selected genes showed differential allelic expression between treatments. Conclusions Correlation of allelic expression of several SNPs with total gene expression indicates that these variants may be the cis-acting variants or in linkage disequilibrium with such variants. Enrichment of apoptosis and cell death gene categories among the positively selected genes reveals the past selection pressures experienced by the populations used in this study.

2012-01-01

358

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

359

Accurate Optical Detection of Amphiphiles at Liquid-Crystal-Water Interfaces  

NASA Astrophysics Data System (ADS)

Liquid-crystal-based biosensors utilize the high sensitivity of liquid-crystal alignment to the presence of amphiphiles adsorbed to one of the liquid-crystal surfaces from water. They offer inexpensive, easy optical detection of biologically relevant molecules such as lipids, proteins, and cells. Present techniques use linear polarizers to analyze the alignment of the liquid crystal. The resulting images contain information not only about the liquid-crystal tilt with respect to the surface normal, the quantity which is controlled by surface adsorption, but also on the uncontrolled in-plane liquid-crystal alignment, thus making the detection largely qualitative. Here we show that detecting the liquid-crystal alignment between circular polarizers, which are only sensitive to the liquid-crystal tilt with respect to the interface normal, makes possible quantitative detection by measuring the transmitted light intensity with a spectrophotometer. Following a new procedure, not only the concentration dependence of the optical path difference but also the film thickness and the effective birefringence can be determined accurately. We also introduce a new "dynamic" mode of sensing, where (instead of the conventional "steady" mode, which detects the concentration dependence of the steady-state texture) we increase the concentration at a constant rate.

Popov, Piotr; Mann, Elizabeth K.; Jákli, Antal

2014-04-01

360

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

361

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 25°C and 0°C, 1000 ln = 28.1 and 33.7, respectively, both values in excellent agreement with the Urey-Epstein paleotemperature scale. Aragonitewater at 25°C gave 28.7, implying a small but significant fractionation between aragonite

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

1969-01-01

362

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

363

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

364

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

NASA Astrophysics Data System (ADS)

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

365

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

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

2012-11-01

366

The hydration number of Li{sup +} in liquid water  

SciTech Connect

The hydration of ions in water is not only fundamental to physical chemistry, but is also relevant to the current issue of selectivity of biological ion channels. In the context of potassium channels for example, the free energies for replacement of inner shell water ligands with peptide carbonyls donated by proteins of the channel, specifically for the preference of K{sup +} over Na{sup +}. Studies to elucidate the thermodynamic features of such inner shell exchange reactions require prior knowledge of the ion hydration structures and energetics. Simulations have produced a range of results including both four and six inner shell water neighbors with considerable statistical dispersion. Simulations are typically not designed to provide sole determinations of such properties, although they do shed light on the issues determining the hydration number of ions in water. The theoretical scheme used here to address these problems for the Li{sup +}(aq) ion is based upon the quasi-chemical organization of solution theory, which is naturally suited to these problems.

Rempe, S.B.; Pratt, L.R.; Hummer, G.; Kress, J.D.; Martin, R.L.; Redondo, A.

2000-02-09

367

[Liquid accumulation medium for isolation of Salmonella from water bodies].  

PubMed

The paper presents the data of experimental and field studies into the efficiency of Salmonella isolation from differently bacterial-contaminated water, by employing 3 storage media. It shows the benefits of using the test medium versus the storage (magnesium and selenite) media commonly applied by practical laboratories. The content of Salmonella in the biotopes of varying biological contamination is shown. PMID:18365464

Golovina, S V; Panasovets, O P; Aleshnia, V V; Zhuravlev, P V; Sibileva, A A; Kovalevskaia, O L

2008-01-01

368

Combined Microwave Radiometer and Micro Rain Radar Analysis of Cloud Liquid Water  

NASA Astrophysics Data System (ADS)

The cloud liquid water is a parameter of vital interest in both modeling and forecasting weather. In meso- scale models, the magnitude of latent heat effects corresponds to the amount of cloud liquid water, which is important in the development of a certain weather system. The purpose of this study is to obtain the combined cloud liquid water from a 21.8 and 31.4 GHz ground based microwave radiometer (MWR) and the micro rain radar (MRR), because each instrument has the limitation of observation; it is widely known that the measurements of MWR and MRR are not meaningful with and without rainfall, respectively. The cloud liquid water of the two instruments has been measured at the Cloud Physics Observation System (CPOS) site, located at 37.41¢¥ N, 128.45¢¥ E and 842 m from mean sea level. To examine the performance of instruments, the precipitable water vapor (PWV) measured by the MWR was compared with the calculated PWV of nearest radiosonde from December 2003 to July 2008, and MRR was compared with the several accumulated precipitation observed by AWS. The PWV of MWR gives good agreement with that of radiosonde: R-square = 0.82 for spring, 0.78 for summer, 0.83 for fall, but 0.25 for winter. This bad performance in the winter season seems from the heavy snow on the radome, and then the winter data of MWR has been not considered in the combining algorithm. The comparison of MRR and AWS a correlation coefficient: 30min accumulated precipitation was R-square = 0.84. To combine the MRR and MWR cloud liquid water, firstly we estimate the cloud physical thickness from the difference between the MTSAT-1R cloud top height and cloud base height of visual observation of Daegwallyeong weather station, and the cloud liquid water path of MRR is obtained by multiplying the LWC of MRR and the estimated cloud physical thickness. The trend of MWR liquid water path agrees with that of the MRR during small precipitation. We study these characteristics of MRR and MWR for small precipitation to obtain the combined cloud water content of MRR and MWR, constantly operated regardless to the rainfall.

Yang, H.; Chang, K.; Jeong, J.; Lee, S.; Jang, Y.; Lee, M.; Kim, K.

2008-12-01

369

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

370

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

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

2014-09-15

371

Dispersive liquid-liquid microextraction combined with ultra-high performance liquid chromatography for the simultaneous determination of 25 sulfonamide and quinolone antibiotics in water samples.  

PubMed

In this work, a dispersive liquid-liquid microextraction (DLLME) procedure combined with ultra-high performance liquid chromatography with diode-array detection was developed to determine 25 antibiotics in mineral and run-off waters. Optimum DLLME conditions (5 mL of water at pH=7.6, 20% (w/v) NaCl, 685 ?L of CHCl? as extractant solvent, and 1250 ?L of ACN as disperser solvent) allowed the repeatable, accurate and selective determination of 11 sulfonamides (sulfanilamide, sulfacetamide, sulfadiazine, sulfathiazole, sulfadimidin, sulfamethoxypyridazine, sulfadoxine, sulfamethoxazole, sulfisoxazole, sulfadimethoxine and sulfaquinoxaline) and 14 quinolones (pipemidic acid, marbofloxacin, fleroxacin, levofloxacin, pefloxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, moxifloxacin, oxolinic acid and flumequine). The method was validated by means of the obtention of calibration curves of the whole method as well as a recovery study at two levels of concentration. The LODs of the method were in the range 0.35-10.5 ?g/L with recoveries between 78% and 117%. PMID:23246932

Herrera-Herrera, Antonio V; Hernández-Borges, Javier; Borges-Miquel, Teresa M; Rodríguez-Delgado, Miguel Ángel

2013-03-01

372

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

373

[Simultaneous determination of four phthalate esters in water samples using ultrasound-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography].  

PubMed

Ultrasound-assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography (UA-DLLME-HPLC) was developed for the determination of four typical phthalate esters (PAEs). The analyzed PAEs included dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and di-n-octyl phthalate (DnOP). The UA-DLLME parameters such as types/volumes of extraction/dispersion solvents, ultrasonic time, ionic strength and extraction time, were investigated. Enrichment factor (EF)was employed to evaluate the extraction efficiency. The conditions were finally chosen: CCl4 (40 microL)/ acetonitrile (1.0 mL) as extraction/dispersion solvents; 30 g/L NaCl; ultrasound/centrifugation of 5 min. Under the optimized extraction conditions, UA-DLLME exhibited strong enrichment ability for the four PAEs. The EFs for DMP, DEP, DBP and DnOP obtained were 71, 144, 169 and 159, respectively. The limits of detection were 3.78, 1.77, 3.07 and 3.30 microg/L for DMP, DEP, DBP and DnOP, respectively. The satisfactory recoveries for three water samples at three spiked levels ranged from 82.99%-114.47%, with the relative standard deviations of 1.93%-8.31%. It is a convenient, speedy, environmentally benign method for the routine analysis of PAEs in water samples. PMID:23697182

Ma, Yanling; Chen, Lingxin; Ding, Yangjun; Ming, Yongfei; Li, Jinhua

2013-02-01

374

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

SciTech Connect

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

Lue, L.; Blankschtein, D. [Massachusetts Inist. of Technology, Cambridge, MA (United States)

1992-10-15

375

Dynamics of a liquid lamella resulting from the impact of a water drop on a small target  

Microsoft Academic Search

The dynamics of a circular liquid lamella resulting from the collision of a water drop with a small disc-like target was studied experimentally and theoretically. Such a type of collision also acts as a model of drop impacts on plane surfaces in the absence of liquid friction, and therefore for more widespread collisions of drops of inviscid liquid with solid

A. Rozhkov; B. Prunet-Foch; M. Vignes-Adler

2004-01-01

376

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

SciTech Connect

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

Cheng, I.F. (Seton Hall Univ., South Orange, NJ (United States)); Jordan, J. (Pennsylvania State Univ., University Park (United States))

1991-05-02

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

Experimental Observation of Bulk Liquid Water Structure in ``No Man's Land''  

NASA Astrophysics Data System (ADS)

Experiments on pure bulk water below about 235 K have so far been difficult: water crystallization occurs very rapidly below the homogeneous nucleation temperature of 232 K and above 160 K, leading to a ``no man's land'' devoid of experimental results regarding the structure. Here, we demonstrate a new, general experimental approach to study the structure of liquid states at supercooled conditions below their limit of homogeneous nucleation. We use femtosecond x-ray pulses generated by the LCLS x-ray laser to probe evaporatively cooled droplets of supercooled bulk water and find experimental evidence for the existence of metastable bulk liquid water down to temperatures of 223 K in the previously largely unexplored ``no man's land''.

Sellberg, Jonas; McQueen, Trevor; Huang, Congcong; Loh, Duane; Laksmono, Hartawan; Sierra, Raymond; Hampton, Christina; Starodub, Dmitri; Deponte, Daniel; Martin, Andrew; Barty, Anton; Wikfeldt, Thor; Schlesinger, Daniel; Pettersson, Lars; Beye, Martin; Nordlund, Dennis; Weiss, Thomas; Feldkamp, Jan; Caronna, Chiara; Seibert, Marvin; Messerschmidt, Marc; Williams, Garth; Boutet, Sebastien; Bogan, Michael; Nilsson, Anders

2013-03-01

379

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

380

Potential transient liquid water flow features in fresh craters on Vesta  

NASA Astrophysics Data System (ADS)

Observations made by the Dawn spacecraft reveal unexpected potential transient liquid water flow features (PTFs) in fresh craters on Vesta. The PTFs have features similar to the headward alcoves, channels and distal aprons of the Martian gullies and related features on Earth (e.g. Malin & Edgett 2000), and have been identified in multiple Vestan craters. All of the craters have relatively fresh rims, which suggests that they, and the PTFs, formed relatively recently in the history of Vesta's evolution. There is some correlation between craters that contain PTFs and craters that contain pitted terrain, which Denevi et al. (2012) propose formed as volatile-bearing material degassed after being heated by an impact. Cornelia crater contains good examples of PTFs and a geological map was made of Cornelia crater based on ~20 m/pixel resolution images. Cross-cutting relationships derived from the map make it is possible to discern a geological history: firstly, an early damp stage, during which the PTFs formed; secondly, a transitional damp to dry stage, during which the pitted terrain formed and thirdly, a dry stage. There is considerable morphological evidence that the formation of the PTFs in Cornelia was by flow of liquid water and not by dry granular flow, flow of impact melt or flow of liquid CO2. The channels are not as sinuous as those on the Earth and Mars, but the fact that the PTFs formed on the relatively high slopes of the crater walls and under conditions of Vesta's low gravity, means that the channels may not need to divert around obstacles. The PTFs in Cornelia crater tend to form in the dark material dominated areas of the crater, which Reddy et al. (2012) conclude has a composition similar to carbonaceous chondrite (CC) and think originates from the impactor that formed Vesta's Veneneia impact basin. Vesta's current surface temperatures and pressures make it an inhospitable environment for liquid water. But, energy from a high velocity impactor that impacts an area of CC could release the mineralogically bound water from the CC and provide temporarily increased temperatures and pressures in the newly formed crater, which would allow liquid water to briefly flow and form the PTFs before it spontaneously boils and evaporates. Results from Dawn's Gamma Ray and Neutron Detector imply up to 106 kg of water within the 150 g/cm2 top portion of Vesta's regolith that the instrument senses (Prettyman et al. 2012). The potential for transient flow of liquid water on the classically "dry" Vesta illuminates the possibility that liquid water could be present in previously unconsidered locations and have previously unconsidered influences on the history of our solar system.

Scully, J. E.; Yin, A.; Russell, C. T.; Denevi, B. W.; Reddy, V.

2012-12-01

381

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 ...

382

Reaktive fluessig/fluessig Extraktion von Schwermetallen aus Deponiesickerwasser. Charakterisierung und Anwendung. (Reactive liquid/liquid extraction of heavy metals from landfill seepage waters. Its characterisation and application).  

National Technical Information Service (NTIS)

This study demonstrates the applicability of liquid-liquid extraction by means of the commercial complexers LIX26(sup R) and LIX84(sup R) to heavy metal removal from waste waters. The composition of this oil-soluble complex is MeR(sub 2), where Me denotes...

N. Woller

1994-01-01

383

Optimization and validation of liquid-liquid extraction with low temperature partitioning for determination of carbamates in water.  

PubMed

Using a 2(3) experimental design, liquid-liquid extraction with low temperature partitioning (LLE-LTP) was optimized and validated for analysis of three carbamates (aldicarb, carbofuran and carbaryl) in water samples. In this method, 2.0 mL of sample is placed in contact with 4.0 mL of acetonitrile. After agitation, the sample is placed in a freezer for 3 h for phase separation. The organic extract is analyzed by high performance liquid chromatography with ultraviolet detection (HPLC-UV). For validation of the technique, the following figures of merit were evaluated: accuracy, precision, detection and quantification limits, linearity, sensibility and selectivity. Extraction recovery percentages of the carbamates aldicarb, carbofuran and carbaryl were 90%, 95% and 96%, respectively. Even though extremely low volumes of sample and solvent were used, the extraction method was selective and the detection and quantification limits were between 5.0 and 10.0 microg L(-1), and 17.0 and 33.0 microg L(-1), respectively. PMID:20541641

Goulart, Simone Machado; Alves, Renata Domingos; Neves, Antônio Augusto; de Queiroz, José Humberto; de Assis, Tamires Condé; de Queiroz, Maria Eliana L R

2010-06-25

384

Restriction Fragment Length Polymorphisms Associated with Water Use Efficiency in Tomato  

Microsoft Academic Search

Improvement of crop water use efficiency (WUE) has not been successful because evaluation for this component of drought resistance is unreliable in field-grown plants. The composition of stable isotopes of plant carbon (delta 13C) was earlier shown to be an excellent indicator of WUE in tomato and other species. It is now reported that delta 13C can be satisfactorily predicted

Bjorn Martin; James Nienhuis; Gretchen King; Alison Schaefer

1989-01-01

385

On the possibility of liquid water on present-day Mars  

NASA Astrophysics Data System (ADS)

Using a validated general circulation model, we determine where and for how long the surface pressure and surface temperature on Mars meet the minimum requirements for the existence of liquid water in the present climate system: pressures and temperatures above the triple point of water but below the boiling point. We find that for pure liquid water, there are five ``favorable'' regions where these requirements are satisfied: between 0° and 30°N in the plains of Amazonis, Arabia, and Elysium; and in the Southern Hemisphere impact basins of Hellas and Argyre. The combined area of these regions represents 29% of the planet's surface area. In the Amazonis region these requirements are satisfied for a total integrated time of 37 sols each Martian year. In the Hellas basin the number of degree days above zero is 70, which is well above those experienced in the dry valley lake region of Antarctica. These regions are remarkably well correlated with the location of Amazonian paleolakes mapped by Cabrol and Grin [2000] but are poorly correlated with the seepage gullies found by Malin and Edgett [2000]. In both instances, obliquity variations may play a role. For brine solutions the favorable regions expand and could potentially include most of the planet for highly concentrated solutions. Whether liquid water ever forms in these regions depends on the availability of ice and heat and on the evaporation rate. The latter is poorly understood for low-pressure CO2 environments but is likely to be so high that melting occurs rarely, if at all. However, even rare events of liquid water formation would be significant since they would dominate the chemistry of the soil and would have biological implications as well. It is therefore worth reassessing the potential for liquid water formation on present day Mars, particularly in light of recent Mars Global Surveyor observations.

Haberle, Robert M.; McKay, Christopher P.; Schaeffer, James; Cabrol, Nathalie A.; Grin, Edmon A.; Zent, Aaron P.; Quinn, Richard

2001-10-01

386

Formation of prebiotic molecules in liquid water environments on the surface of Titan  

NASA Astrophysics Data System (ADS)

Saturn's moon Titan represents a unique locale for studying prebiotic chemistry. Reactions occurring in its thick nitrogen-methane atmosphere produce a wide variety of carbon, hydrogen, and nitrogen containing organic molecules. If these molecules are exposed to liquid water, they may react further to produce oxygen-containing species, a key step in the formation of terrestrial biomolecules. On average, Titan's surface is too cold for liquid water. However, models indicate that melting caused by impacts and/or cryovolcanism may lead to its episodic availability. One possible cryovolcanic dome, Ganesa Macula, was identified in early observations by the Cassini spacecraft. In this work, I estimate the height and morphology of this feature using a synthetic aperture radar (SAR) image. I then use a thermal conduction code to calculate the freezing timescale for an initially liquid dome, yielding freezing timescales of ~10^2 - 10^5 years. To determine how far aqueous organic chemistry can proceed in liquid water environments on Titan, I measure the rate coefficients of Titan analogue organic molecules ("tholins") with low temperature aqueous solutions to produce oxygenated species. These reactions display first-order kinetics with half- lives between 0.4 and 7 days at 273 K (in water) and between 0.3 and 14 days at 253 K (in 13 wt. % ammonia-water). Tholin hydrolysis in aqueous solutions is thus very fast compared to the freezing timescales of impact melts and volcanic sites on Titan, which take hundreds to thousands of years to freeze. The fast incorporation of oxygen, along with new chemistry made available by the introduction of ammonia, may lead to the formation of molecules of prebiotic interest in these transient liquid water environments. This chemistry makes impact craters and cryovolcanoes important targets for future missions to Titan.

Neish, Catherine Dorothy

387

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

388

Vapor-liquid equilibrium in low pressure water+congener mixtures  

Microsoft Academic Search

Vapor-liquid equilibrium in binary water+congeners mixtures found in alcoholic distillation has been analyzed using the Peng-Robinson\\u000a equation of state and one of the most popular modern mixing rules, the Wong-Sandler model. Accurate modeling of the concentration\\u000a of congeners (substances different from ethanol and water) in the vapor phase is of special importance because these substances\\u000a give some special characteristics of

Claudio Alonso Faúndez; Felipe Andrés Urbina; José Omar Valderrama

2009-01-01

389

Electron impact ionization of liquid and gaseous water: a single-center partial-wave approach  

Microsoft Academic Search

In this work, we report a unified methodology to express the molecular wavefunctions of water in both vapor and liquid phases by means of a single-center approach. These latter are then used as input data in a theoretical treatment---previously published and successfully tested---for describing the water ionization process in the first Born approximation (Champion et al 2006 Phys. Rev. A

C. Champion

2010-01-01

390

Liquid crystalline phase behavior of silica nanorods in dimethyl sulfoxide and water.  

PubMed

We report lyotropic smectic liquid crystalline phase behavior of silica nanorods dispersed in binary mixtures of dimethyl sulfoxide (DMSO) and water (H2O). The phase behavior is affected by nanorod size polydispersity and DMSO concentration in the binary solvent. The isotropic to biphasic transition is strongly affected by the relative amount of DMSO in the solvent, but the solvent has little effect on the biphasic to liquid crystal transition above 40/60 DMSO/H2O by volume. At less than 40% DMSO, increasing silica nanorod concentration initially results in the formation of liquid crystalline domains, but further increasing silica concentration results in crystal solvate formation. The morphology of the liquid crystalline phase is strongly affected by the size polydispersity, with lower polydispersity leading to a more uniform structure. As in other lyotropic nanocylinder systems, the microstructure of continuous solid films produced from the dispersions was affected by both the initial microstructure and the applied shear. PMID:24730665

Xu, Teng; Davis, Virginia A

2014-04-29

391

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

392

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

NASA Astrophysics Data System (ADS)

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

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

1988-02-01

393

The Kohn-Sham density of states and band gap of water: from small clusters to liquid water.  

PubMed

Electronic properties of water clusters (H2O)(n), with n=2, 4, 8, 10, 15, 20, and 30 molecules were investigated by sequential Monte Carlo/density-functional theory (DFT) calculations. DFT calculations were carried out over uncorrelated configurations generated by Monte Carlo simulations of liquid water with a reparametrized exchange-correlation functional that reproduces the experimental information on the electronic properties (first ionization energy and highest occupied molecular orbital-lowest unoccupied molecular orbital gap) of the water dimer. The dependence of electronic properties on the cluster size (n) shows that the density of states (DOS) of small water clusters (n>10) exhibits the same basic features that are typical of larger aggregates, such as the mixing of the 3a1 and 1b1 valence bands. When long-ranged polarization effects are taken into account by the introduction of embedding charges, the DOS associated with 3a1 orbitals is significantly enhanced. In agreement with valence-band photoelectron spectra of liquid water, the 1b1, 3a1, and 1b2 electron binding energies in water aggregates are redshifted by approximately 1 eV relative to the isolated molecule. By extrapolating the results for larger clusters the threshold energy for photoelectron emission is 9.6+/-0.15 eV (free clusters) and 10.58+/-0.10 eV (embedded clusters). Our results for the electron affinity (V0=-0.17+/-0.05 eV) and adiabatic band gap (E(G,Ad)=6.83+/-0.05 eV) of liquid water are in excellent agreement with recent information from theoretical and experimental works. PMID:16108672

Cabral do Couto, P; Estácio, S G; Costa Cabral, B J

2005-08-01

394

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

395

Effect of Adsorbed Water Upon the Spreading of Organic Liquids on Soda-Lime Glass.  

National Technical Information Service (NTIS)

Results are given of an investigation of the extent to which water adsorbed on a silicate glass surface affects the spreading and the equilibrium contact angle of various pure organic liquids. Of especial interest is the effect of the transition of the ph...

E. G. Shafrin W. A. Zisman

1967-01-01

396

Vapor–liquid equilibrium of systems containing alcohols, water, carbon dioxide and hydrocarbons using SAFT  

Microsoft Academic Search

The statistical associating fluid theory (SAFT) equation of state is employed for the correlation and prediction of vapor–liquid equilibrium (VLE) of eighteen binary mixtures. These include water with methane, ethane, propane, butane, propylene, carbon dioxide, methanol, ethanol and ethylene glycol (EG), ethanol with ethane, propane, butane and propylene, methanol with methane, ethane and carbon dioxide and finally EG with methane

Xiao-Sen Li; Peter Englezos

2004-01-01

397

Comparison of gas and liquid chromatography for analysing polar pesticides in water samples  

Microsoft Academic Search

This review describes the applications of gas chromatography (GC) and liquid chromatography (LC) in the analysis of selected groups of pesticides in water. The attention is focussed on the most popular (in terms of amounts produced and applied) pesticide classes, i.e., carbamates, phenylureas, triazines, phenoxy acetic acid derivatives and chlorinated phenols. The use of GC and LC for the analysis

I. Liška; J. Slobodník

1996-01-01

398

Water disinfection using the novel approach of ozone and a liquid whistle reactor  

Microsoft Academic Search

A novel approach of ozone treatment assisted by a liquid whistle reactor (LWR), which generates hydrodynamic cavitation, has been explored for water disinfection using a simulated effluent containing Escherichia coli (E. coli), one of the dominant markers in faecal coliforms. A suspension having an E. coli concentration of approximately 108 to 109CFUmL?1 was introduced into the LWR to examine the

Rashmi Chand; David H. Bremner; Kyu C. Namkung; Phillip J. Collier; Parag R. Gogate

2007-01-01

399

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

PubMed

We present a complete yet computationally simple model for the dielectric response function of liquid water over the energy-momentum plane, which, in contrast to earlier models, is consistent with the recent inelastic X-ray scattering spectroscopy data at both zero and finite momentum transfer values. The model follows Ritchie's extended-Drude algorithm and is particularly effective at the region of the Bethe ridge, substantially improving previous models. The present development allows for a more accurate simulation of the inelastic scattering and energy deposition process of low-energy electrons in liquid water and other biomaterials. As an example, we calculate the stopping power of liquid water for electrons over the 0.1-10 keV range where direct experimental measurements are still impractical and the Bethe stopping formula is inaccurate. The new stopping power values are up to 30-40% lower than previous calculations. Within the range of validity of the first Born approximation, the new values are accurate to within the experimental uncertainties (a few percent). At the low end, the introduction of Born corrections raises the uncertainty to perhaps approximately 10%. Thus the present model helps extend the ICRU electron stopping power database for liquid water down to about two orders of magnitude with a comparable level of uncertainty. PMID:16038591

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

2005-08-01

400

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

NASA Technical Reports Server (NTRS)

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

DelGenio, Anthony

1999-01-01

401

Unconventional physical mechanisms between stimulated Brillouin scattering and backward stimulated Raman scattering in liquid water  

Microsoft Academic Search

In this paper, the stimulated Brillouin scattering (SBS) and the backward stimulated Raman scattering (BSRS) excited by a focused Gaussian laser in liquid water with different attenuation coefficients are investigated experimentally. Experimental results indicate that the relationships between SBS and BSRS are not merely competitive; the former has an obvious amplifying effect on the latter. Also, two different physical mechanisms

Jiulin Shi; Juan Liu; Shujing Li; Jian Xia; Jian’an Liu; Wei Fang; Kecheng Yang; Xingdao He

2011-01-01

402

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

SciTech Connect

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

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

1990-02-01

403

Radium measurement in water samples by ?-liquid scintillation counting with ?\\/? discrimination  

Microsoft Academic Search

A fast and inexpensive sample preparation method for quantitative determination of radium in water involving ?-liquid scintillation with ?\\/? discrimination has been assessed. The optimal extraction of 226Ra by the extractive-scintillator cocktail RADAEX® requires pH above 10, which leads to salt precipitation in samples of high salinity. Salt precipitation can be prevented by addition of ?-hydroxyisobutyric acid (HIBA). This methodology,

J. Aupiais

2005-01-01

404

Research on balance control for ship roll stability based on transferring liquid among water cabins  

Microsoft Academic Search

This paper focuses on the ship roll balance control based on the ship roll dynamic model and special actuator. According to the ship dynamics model for roll stability and an actuator with the transferring liquid among Water cabins for ship, a control model for ship roll balance adjustment is built and also the control system is designed. And then, the

Tang Meng; Guo Juan; Gan Feng

2010-01-01

405

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; María-José Torres

2000-01-01

406

Infrared Reflectance of Water Frosts Condensed on Liquid-Nitrogen-Cooled Surface in Vacuum.  

National Technical Information Service (NTIS)

Spectral absolute reflectance measurements from 0.5 to 12.0 micrometers were made for water cryodeposits formed on liquid-nitrogen-cooled surfaces in a vacuum infrared integrating sphere. The results are presented as functions of view angle, deposit thick...

A. M. Smith B. A. Seiber B. E. Wood J. A. Roux

1970-01-01

407

Isobaric vapor-liquid equilibrium data for the ethanol-water-strontium bromide system  

Microsoft Academic Search

Isobaric experimental data of vapor-liquid equilibrium for the ethanol-water-strontium bromide system at different mole fractions of strontium bromide have been measured at 100.6 kPa. Data were correlated by Jaques and Furter's method. Thermodynamic consistency was checked by Herington's method with satisfactory results.

Ernesto Vercher; M. Pilar Pena; Antoni Martinez-Andreu

1994-01-01

408

Satellite Microwave Sensing of Oceanic Cloud Liquid Water: Application to the Earth Radiation Budget and Climate  

Microsoft Academic Search

Understanding the various complex interactions of cloud properties with the Earth's radiation budget, thermodynamical processes and atmospheric dynamics is crucial in determining the role of clouds in global climate. The following research addresses one aspect of this broad problem by attempting to describe the large-scale characteristics of cloud liquid water and the relationships of this bulk cloud property to the

Thomas Joseph Greenwald

1994-01-01

409

Equations Governing Space-Time Variability of Liquid Water Path in Stratus Clouds  

Microsoft Academic Search

We present a method on how to derive an underlying mathematical (statistical or model free) equation for a liquid water path (LWP) signal directly from empirical data. The evolution of the probability density functions (PDFs) from small to large time scales is explicitly derived in the framework of Fokker-Planck equation. A drift and a diffusion term describing the deterministic and

K. Ivanova; T. P. Ackerman; M. Ausloos

2004-01-01

410

Cloud liquid water content responses to hygroscopic seeding of warm clouds  

Microsoft Academic Search

The cloud liquid water content (CLWC) data in time and space from a total of 96 pairs of target (T) and control (C) experiments were analyzed in this study to compare the responses of CLWC to hygroscopic seeding of warm clouds. Our results of various approaches taken for this analysis have indicated significant modifications in the CLWC for the T

S. S. Kandalgaonkar; G. K. Manohar; M. I. R. Tinmaker

2000-01-01

411

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

EPA Science Inventory

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

412

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

PubMed

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

Attri, Pankaj; Venkatesu, P; Kumar, Anil

2012-10-01

413

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

NASA Astrophysics Data System (ADS)

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

Sidiq, Sumyra; Pal, Santanu Kumar

2014-04-01

414

Retrieving fog liquid water content using a new 94 GHz FMCW cloud radar  

Microsoft Academic Search

The vertical distribution of the liquid water content (LWC) in fog and low stratus is a critical microphysical parameter since it essentially influences the interaction between these low level clouds and the solar and terrestrial radiation. Despite of this importance there are only few investigations concerning LWC-profiles during fog events, which are mainly restricted to balloon borne measurements and suffer

F. Maier; B. Thies; J. Bendix

2010-01-01

415

Liquid–liquid equilibria of the systems dipropyl ether + n-propanol + water and dipropyl ether + n-propanol + ethylene glycol at different temperatures  

Microsoft Academic Search

In this work, experimental liquid–liquid equilibria (LLE) data of the dipropyl ether+n-propanol+water and dipropyl ether+n-propanol+ethylene glycol systems are presented. The LLE of both systems have been measured at 283.15 and 323.15K. The equilibrium data presented are correlated using NRTL and UNIQUAC equations. The reliability of these models is tested by comparison with experimental results. Moreover, the solvent capabilities of water

A. Cháfer; M. C. Burguet; J. B. Monton; E. Lladosa

2007-01-01

416

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

PubMed

A fast and simple technique composed of dispersive liquid-liquid microextraction (DLLME) and online preconcentration MEKC with diode array detection was developed for the determination of four phenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, 2,6-dichlorophenoxyacetic acid, and 4-chlorophenoxyacetic acid, in drinking water. The four phenoxyacetic acids were separated in reversed-migration MEKC to the baseline. About 145-fold increases in detection sensitivity were observed with online concentration strategy, compared with standard hydrodynamic injection (5 s at 25 mbar pressure). LODs ranged from 0.002 to 0.005 mg/L using only the online preconcentration procedures without any offline concentration of the extract. A DLLME procedure was used in combination with the proposed online preconcentration strategies, which achieved the determination of analytes at limits of quantification ranging from 0.2 to 0.5 ?g/kg, which is far lower than the maximum residue limits established by China. The satisfactory recoveries obtained by DLMME spiked at two levels ranged from 67.2 to 99.4% with RSD <15%, making this proposed method suitable for the determination of phenoxyacetic acids in water samples. PMID:23897833

Zhang, Yaohai; Jiao, Bining

2013-09-01

417

Dispersive liquid-liquid microextraction combined with nonaqueous capillary electrophoresis for the determination of fluoroquinolone antibiotics in waters.  

PubMed

Dispersive liquid-liquid microextraction (DLLME) was combined for the first time with NACE-UV for the selective determination of eight fluoroquinolone antibiotics (lomefloxacin, levofloxacin, marbofloxacin, ciprofloxacin, sarafloxacin, enrofloxacin, danofloxacin and difloxacin) in mineral and run-off waters. Field-enhanced sample injection was carried out in order to improve the sensitivity, whereas pipemidic acid was used as internal standard. The BGE that provided complete separation of the eight analytes and the internal standard was composed of 3 M acetic acid, 49 mM ammonium acetate in 55:45 v/v methanol:ACN. Optimum DLLME conditions (extraction of 5 mL of water at pH 7.6 with 685 ?L of CHCl(3) and 1250??L of ACN, extractant and disperser solvents, respectively) were achieved by means of experimental design methodology. Calibration curves of the whole method were obtained with correlation coefficients (R) higher than 0.994 in all cases. An accuracy and precision study was carried out at different levels of concentration, finding that there were no significant differences (Student's t-test) between real and spiked concentrations. PMID:20859952

Herrera-Herrera, Antonio V; Hernández-Borges, Javier; Borges-Miquel, Teresa M; Rodríguez-Delgado, Miguel Á

2010-10-01

418

Duration of liquid water habitats on early Mars  

NASA Astrophysics Data System (ADS)

The duration of ice-covered lakes after the initial freezing of the early Mars is presently estimated via a climate model whose critical parameter is the existence of peak seasonal temperatures above freezing, and in which the variability of insolation is included. Under conditions in which meltwater was supplied by an ice source, it is found that water habitats could have been maintained under relatively thin ice sheets for as many as 700 million years after the onset of below-freezing global temperatures. The duration of such habitats on the early Mars therefore exceeds the upper limit of the time envisioned for the emergence of aquatic life on earth.

McKay, C. P.; Davis, W. L.

1991-04-01

419

Interaction of a long alkyl chain protic ionic liquid and water  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

420

Identification of Nontuberculous Mycobacteria Existing in Tap Water by PCR-Restriction Fragment Length Polymorphism  

Microsoft Academic Search

This paper presents the finding of the possible cause of the high false-positive rate in acid-fast staining in histological examinations. Using acid-fast staining, culture, and PCR, acid-fast bacilli were detected in 83.7% of 49 hospital tap water samples and nontuberculous mycobacteria (NTM) were detected in 20.4% of the same 49 samples. The 10 NTM isolates were also identified to the

Chiao-tang Chang; Ling-yu Wang; Chen-yi Liao; Shiao-ping Huang

2002-01-01