WorldWideScience

Sample records for air water interfaces

  1. Methylglyoxal at the Air-Water Interface

    Science.gov (United States)

    Wren, S. N.; Gordon, B. P.; McWilliams, L.; Valley, N. A.; Richmond, G.

    2014-12-01

    Recently, it has been suggested that aqueous-phase processing of atmospheric α-dicarbonyl compounds such as methylglyoxal (MG) could constitute an important source of secondary organic aerosol (SOA). The uptake of MG to aqueous particles is higher than expected due to the fact that its carbonyl moieties can hydrate to form diols, as well as the fact that MG can undergo aldol condensation reactions to form larger oligomers in solution. MG is known to be surface active but an improved description of its surface behaviour is crucial to understanding MG-SOA formation, in addition to understanding its gas-to-particle partitioning and cloud forming potential. Here, we employ a combined experimental and theoretical approach involving vibrational sum frequency generation spectroscopy (VSFS), surface tensiometry, molecular dynamics simulations, and density functional theory calculations to study MG's surface adsorption, in both the presence and absence of salts. We are particularly interested in determining MG's hydration state at the surface. Our experimental results indicate that MG slowly adsorbs to the air-water interface and strongly perturbs the water structure there. This perturbation is enhanced in the presence of NaCl. Together our experimental and theoretical results suggest that singly-hydrated MG is the dominant form of MG at the surface.

  2. Anisotropic diffusion of volatile pollutants at air-water interface

    Institute of Scientific and Technical Information of China (English)

    Li-ping CHEN; Jing-tao CHENG; Guang-fa DENG

    2013-01-01

    The volatile pollutants that spill into natural waters cause water pollution. Air pollution arises from the water pollution because of volatilization. Mass exchange caused by turbulent fluctuation is stronger in the direction normal to the air-water interface than in other directions due to the large density difference between water and air. In order to explore the characteristics of anisotropic diffusion of the volatile pollutants at the air-water interface, the relationship between velocity gradient and mass transfer rate was established to calculate the turbulent mass diffusivity. A second-order accurate smooth transition differencing scheme (STDS) was proposed to guarantee the boundedness for the flow and mass transfer at the air-water interface. Simulations and experiments were performed to study the trichloroethylene (C2HCl3) release. By comparing the anisotropic coupling diffusion model, isotropic coupling diffusion model, and non-coupling diffusion model, the features of the transport of volatile pollutants at the air-water interface were determined. The results show that the anisotropic coupling diffusion model is more accurate than the isotropic coupling diffusion model and non-coupling diffusion model. Mass transfer significantly increases with the increase of the air-water relative velocity at a low relative velocity. However, at a higher relative velocity, an increase in the relative velocity has no effect on mass transfer.

  3. Ultrafast dynamics of water at the water-air interface studied by femtosecond surface vibrational spectroscopy

    Directory of Open Access Journals (Sweden)

    Bakker Huib J.

    2013-04-01

    Full Text Available We study the dynamics of water molecules at the water-air interface, using surfacespecific two-dimensional infrared sum-frequency generation (2D-SFG spectroscopy. The data reveal the occurrence of surprisingly fast energy transfer and reorientational dynamics at aqueous interfaces.

  4. Bacterial Swimming at Air/Water and Oil/Water Interfaces

    Science.gov (United States)

    Morse, Michael; Huang, Athena; Li, Guanglai; Tang, Jay

    2012-02-01

    The microbes inhabiting the planet over billions of years have adapted to diverse physical environments of water, soil, and interfaces between water and either solid or air. Following recent studies on bacterial swimming and accumulation near solid surfaces, we turn our attention to the behavior of Caulobacter crescentus, a singly flagellated bacterium, at water/air and water/oil interfaces. The latter is motivated by relevance to microbial degradation of crude oil in light of the recent oil spill in the Gulf of Mexico. Our ongoing study suggests that Caulobacter swarmer cells tend to get physically trapped at both water/air and water/oil interfaces, accumulating at the surface to a greater degree than boundary confinement properties like that of solid surfaces would predict. At the water/air interface, swimmers move in tight circles at half the speed of swimmers in the bulk fluid. At the water/oil interface, swimming circles are even tighter with further reduced swimming speed. We report experimental data and present preliminary analysis of the findings based on low Reynolds number hydrodynamics, the known surface tension, and surface viscosity at the interface. The analysis will help determine properties of the bacterium such as their surface charge and hydrophobicity.

  5. Microscopic dynamics of nanoparticle monolayers at air-water interface.

    Science.gov (United States)

    Bhattacharya, R; Basu, J K

    2013-04-15

    We present results of surface mechanical and particle tracking measurements of nanoparticles trapped at the air-water interface as a function of their areal density. We monitor both the surface pressure (Π) and isothermal compression modulus (ϵ) as well as the dynamics of nanoparticle clusters, using fluorescence confocal microscopy while they are compressed to very high density near the two dimensional close packing density Φ∼0.82. We observe non-monotonic variation in both ϵ and the dynamic heterogeneity, characterized by the dynamical susceptibility χ4 with Φ, in such high density monolayers. We provide insight into the underlying nature of such transitions in close packed high density nanoparticle monolayers in terms of the morphology and flexibility of these soft colloidal particles. We discuss the significance our results in the context of related studies on two dimensional granular or colloidal systems. PMID:23411354

  6. Structure and dynamics of egg white ovalbumin adsorbed at the air/water interface

    NARCIS (Netherlands)

    Kudryashova, E.V.; Meinders, M.B.J.; Visser, A.J.W.G.; Hoek, A. van; Jongh, H.H.J. de

    2003-01-01

    The molecular properties of egg white ovalbumin adsorbed at the air/water interface were studied using infrared reflection absorption spectroscopy (IRRAS) and time-resolved fluorescence anisotropy (TRFA) techniques. Ovalbumin adsorbed at the air/ water interface adopts a characteristic partially unf

  7. Surface Tension of Ab Initio Liquid Water at the Water-Air Interface

    OpenAIRE

    Nagata, Yuki; Ohto, Tatsuhiko; Bonn, Mischa; Kühne, Thomas D.

    2016-01-01

    We report calculations of the surface tension of the water-air interface using ab initio molecular dynamics (AIMD) simulations. We investigate the simulation cell size dependence of the surface tension of water from force field molecular dynamics (MD) simulations, which show that the calculated surface tension increases with increasing simulation cell size, thereby illustrating that a correction for finite size effects is required for the small system used in the AIMD simulation. The AIMD sim...

  8. Anomalous transparency of water-air interface for low-frequency sound

    CERN Document Server

    Godin, O A

    2006-01-01

    Sound transmission through water-air interface is normally weak because of a strong mass density contrast. Here we show that the transparency of the interface increases dramatically at low frequencies. Rather counterintuitively, almost all acoustic energy emitted by a sufficiently shallow monopole source under water is predicted to be radiated into atmosphere. Physically, increased transparency at lower frequencies is due to the increasing role of inhomogeneous waves and a destructive interference of direct and surface-reflected waves under water. The phenomenon of anomalous transparency has significant implications for acoustic communication across the water-air interface, generation of ambient noise, and detection of underwater explosions.

  9. Neutron reflectivity measurement of polymer monolayer and brush at the air/water interface

    International Nuclear Information System (INIS)

    We have been studied on amphiphilic polymer monolayer structure at the air/water interface by X-ray and neutron reflectometry. By complemently use of X-ray and neutron reflectometry, we have found (1) the existence of carpet layer in ionic polymer brush in monolayer system and (2) characteristic structural change in polymer/subphase interface. Furthermore, interesting experiment on small ion distribution was carried out by NR with contrast variation method. With our experimental examples, characteristic points in the neutron reflectivity measurement at the air/water interface and further possibility in this research area are discussed. (author)

  10. Estimating pH at the Air/Water Interface with a Confocal Fluorescence Microscope.

    Science.gov (United States)

    Yang, Haiya; Imanishi, Yasushi; Harata, Akira

    2015-01-01

    One way to determine the pH at the air/water interface with a confocal fluorescence microscope has been proposed. The relation between the pH at the air/water interface and that in a bulk solution has been formulated in connection with the adsorption equilibrium and the dissociation equilibrium of the dye adsorbed. Rhodamine B (RhB) is used as a surface-active fluorescent pH probe. The corrected fluorescence spectrum of RhB molecules at the air/water interface with the surface density of 1.0 nmol m(-2) level shows pH-dependent shifts representing an acid-base equilibrium. Two ways to determine the unknown acid-base equilibrium constant of RhB molecules at the air/water interface have been discussed. With surface-tension measurements, the adsorption properties, maximum surface density, and adsorption equilibrium constants were estimated for both cationic and zwitterionic forms of RhB molecules at the air/water interface.

  11. Scanning force microscopy at the air-water interface of an air bubble coated with pulmonary surfactant.

    OpenAIRE

    Knebel, D; Sieber, M; Reichelt, R.; Galla, H-J; Amrein, M

    2002-01-01

    To study the structure-function relationship of pulmonary surfactant under conditions close to nature, molecular films of a model system consisting of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylglycerol, and surfactant-associated protein C were prepared at the air-water interface of air bubbles about the size of human alveoli (diameter of 100 microm). The high mechanical stability as well as the absence of substantial film flow, inherent to small air bubbles, allowed for scanning ...

  12. Locomotion and phenotypic transformation of the amoeboflagellate Naegleria gruberi at the water-air interface.

    Science.gov (United States)

    Preston, Terence M; King, Conrad A

    2003-01-01

    The protozoon Naegleria gruberi is able to carry out amoeboid locomotion at the water-air interface in a manner indistinguishable from that exhibited on solid substrata with the production of focal contacts and associated filopodia. The speed of locomotion at this interface can be modulated by changes in electrolyte concentrations; these speed changes are identical to those observed at a water-glass interface. The nature of the water-air interface is discussed leading to the hypothesis that surface tension alone could provide suitable properties for the adhesion and translocation of amoebae at this interface without necessitating specific, absorbed molecules. The temporary swimming flagellate stage of Naegleria is able to dock at the interface, make stable adhesions to it, and revert to the amoeboid phenotype. Conversely, amoebae resident at the water-air interface can transform to swimming flagellates and escape into the bulk liquid phase. We report the presence of Naegleria amoebae in the surface microlayers of natural ponds; thus, in freshwater bodies there may be active shuttling of Naegleria amoebae from the benthos to the surface microlayers by means of the non-feeding, swimming flagellate phenotype. The public health implication of this behaviour in the case of the pathogenic relative, Naegleria fowleri, is discussed.

  13. Effect of Particulate Contaminants on the Development of Biofilms at Air/Water Interfaces.

    Science.gov (United States)

    Zhang, Zhenhuan; Christopher, Gordon

    2016-03-22

    The development of biofilms at air/water or oil/water interfaces has important ramifications on several applications, but it has received less attention than biofilm formation on solid surfaces. A key difference between the growth of biofilms on solid surfaces versus liquid interfaces is the range of complicated boundary conditions the liquid interface can create that may affect bacteria, as they adsorb onto and grow on the interface. This situation is exacerbated by the existence of complex interfaces in which interfacially adsorbed components can even more greatly affect interfacial boundary conditions. In this work, we present evidence as to how particle-laden interfaces impact biofilm growth at an air/water interface. We find that particles can enhance the rate of growth and final strength of biofilms at liquid interfaces by providing sites of increased adhesive strength for bacteria. The increased adhesion stems from creating localized areas of hydrophobicity that protrude in the water phase and provide sites where bacteria preferentially adhere. This mechanism is found to be primarily controlled by particle composition, with particle size providing a secondary effect. This increased adhesion through interfacial conditions creates biofilms with properties similar to those observed when adhesion is increased through biological means. Because of the generally understood ubiquity of increased bacteria attachment to hydrophobic surfaces, this result has general applicability to pellicle formation for many pellicle-forming bacteria. PMID:26943272

  14. Thermodynamics of iodide adsorption at the instantaneous air-water interface

    Science.gov (United States)

    Stern, Abraham C.; Baer, Marcel D.; Mundy, Christopher J.; Tobias, Douglas J.

    2013-03-01

    We performed molecular dynamics simulations using both polarizable and non-polarizable force fields to study the adsorption of iodide to the air-water interface. A novel aspect of our analysis is that the progress of ion adsorption is measured as the distance from the instantaneous interface, which is defined by a coarse-graining scheme proposed recently by Willard and Chandler ["Instantaneous liquid interfaces," J. Phys. Chem. B 114, 1954-1958 (2010), 10.1021/jp909219k]. Referring structural and thermodynamic quantities to the instantaneous interface unmasks molecular-scale details that are obscured by thermal fluctuations when the same quantities are referred to an average measure of the position of the interface, such as the Gibbs dividing surface. Our results suggest that an ion adsorbed at the interface resides primarily in the topmost water layer, and the interfacial location of the ion is favored by enthalpy and opposed by entropy.

  15. Characterization of predominantly hydrophobic poly(styrene)-poly(ethylene oxide) copolymers at air/water and cyclohexane/water interfaces

    International Nuclear Information System (INIS)

    Interfacial tension measurements are employed to explore the spreading behavior of predominantly hydrophobic poly(styrene)--poly(ethylene oxide), PS-PEO, diblock copolymers at air/water and cyclohexane/water interfaces. Two copolymers with 7%- and 15.5%-PEO are examined in this study. The former is expected to have a PS block limiting area in air roughly equal to the limiting PEO pancake area, whereas the latter is expected to have a limiting PS block area in air approximately 3 times smaller than the limiting PEO pancake area. At the air/water interface, the 7%-PEO copolymer does not spread well, which is attributed to interference from the hydrophobic PS block. In contrast, the 7%-PEO copolymer spreads well at the cyclohexane/water interface, producing an isotherm with a terminating mean molecular area 3 times smaller than that obtained at the air/water interface. The 15.5%-PEO copolymer spreads well at both the air/water ad cyclohexane/water interfaces due to less interference from the smaller hydrophobic PS block. These observations are compared to compression isotherms, and the results are discussed in terms of the solvating nature of the adjacent cyclohexane phase for the PS block

  16. Demonstration of adaptive optics for mitigating laser propagation through a random air-water interface

    Science.gov (United States)

    Land, Phillip; Majumdar, Arun K.

    2016-05-01

    This paper describes a new concept of mitigating signal distortions caused by random air-water interface using an adaptive optics (AO) system. This is the first time the concept of using an AO for mitigating the effects of distortions caused mainly by a random air-water interface is presented. We have demonstrated the feasibility of correcting the distortions using AO in a laboratory water tank for investigating the propagation effects of a laser beam through an airwater interface. The AO system consisting of a fast steering mirror, deformable mirror, and a Shack-Hartmann Wavefront Sensor for mitigating surface water distortions has a unique way of stabilizing and aiming a laser onto an object underneath the water. Essentially the AO system mathematically takes the complex conjugate of the random phase caused by air-water interface allowing the laser beam to penetrate through the water by cancelling with the complex conjugates. The results show the improvement of a number of metrics including Strehl ratio, a measure of the quality of optical image formation for diffraction limited optical system. These are the first results demonstrating the feasibility of developing a new sensor system such as Laser Doppler Vibrometer (LDV) utilizing AO for mitigating surface water distortions.

  17. Surface Tension of Ab Initio Liquid Water at the Water-Air Interface

    CERN Document Server

    Nagata, Yuki; Bonn, Mischa; Kühne, Thomas D

    2016-01-01

    We report calculations of the surface tension of the water-air interface using ab initio molecular dynamics (AIMD) simulations. We investigate the simulation cell size dependence of the surface tension of water from force field molecular dynamics (MD) simulations, which show that the calculated surface tension increases with increasing simulation cell size, thereby illustrating that a correction for finite size effects is required for the small system used in the AIMD simulation. The AIMD simulations reveal that the double-{\\xi} basis set overestimates the experimentally measured surface tension due to the Pulay stress, while the triple and quadruple-{\\xi} basis sets give similar results. We further demonstrate that the van der Waals corrections critically affect the surface tension. AIMD simulations without the van der Waals correction substantially underestimate the surface tension, while van der Waals correction with the Grimme's D2 technique results in the value for the surface tension that is too high. T...

  18. Differential Effects of Lysophosphatidylcholine on the Adsorption of Phospholipids to an Air/Water Interface

    OpenAIRE

    Biswas, Samares C.; Rananavare, Shankar B.; Hall, Stephen B.

    2006-01-01

    To determine how the hydrophobic surfactant proteins promote insertion of the surfactant lipids into an air/water interface, we measured the effect of lysophosphatidylcholine (LPC) on adsorption. Existing models contend that the proteins function either by disordering the lipids or by stabilizing a negatively curved structure located between the adsorbing vesicle and the interface. Because LPC produces greater disorder but positive curvature, the models predict opposite effects. With vesicles...

  19. Hydrodynamics of a self-propelled camphor boat at the air-water interface

    Science.gov (United States)

    Akella, Sathish; Singh, Dhiraj; Singh, Ravi; Bandi, Mahesh

    2015-11-01

    A camphor tablet, when placed at the air-water interface undergoes sublimation and camphor vapour spreads radially outwards across the surface due to Marangoni forces. This steady camphor influx from tablet onto the air-water interface is balanced by the camphor outflux due to evaporation. When spontaneous fluctuations in evaporation break the axial symmetry of Marangoni force acting radially outwards, the camphor tablet is propelled like a boat along the water surface. We report experiments on the hydrodynamics of a self-propelled camphor boat at air-water interfaces. We observe three different modes of motion, namely continuous, harmonic and periodic, due to the volatile nature of camphor. We explain these modes in terms of ratio of two time-scales: the time-scale over which viscous forces are dominant over the Marangoni forces (τη) and the time-scale over which Marangoni forces are dominant over the viscous forces (τσ). The continuous, harmonic and periodic motions are observed when τη /τσ ~ 1 , τη /τσ >= 1 and τη /τσ >> 1 respectively. Experimentally, the ratio of the time scales is varied by changing the interfacial tension of the air-water interface using Sodium Dodecyl Sulfate. This work was supported by the Collective Interactions Unit, OIST Graduate University.

  20. Seismic reflection and transmission coefficients at an air-water interface of saturated porous soil

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xin-min; XIA Tang-dai; XU Ping; ZOU Zhen-xuan

    2006-01-01

    Based on the modified Biot's theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences between air-saturated soils and water-saturated soils were theoretically discussed, and the theoretical formulas of reflection and transmission coefficients at an air-water interface were derived. The characteristics of propagation and attenuation of elastic waves in air-saturated soils were given and the relations among the frequency, the angle of incidence and the reflection, transmission coefficients were analyzed by using numerical methods. Numerical results show that the propagation characteristic of the wave in air-saturated soils is great different from that in water-saturated soils. The frequency and the angle of incidence can have great influences on the reflection and transmission coefficients at interface. Some new cognition about the wave propagation is obtained and the study suggests that we may carefully pay attention to the influence of air on the dynamic analysis of seismic wave.

  1. Emulsion droplet spreading at air/water interfaces: mechanisms and relevance to the whipping of cream

    NARCIS (Netherlands)

    Hotrum, N.E.

    2004-01-01

    Keywords:emulsion, spreading coefficient, surface tension, emulsifier, whipped cream, dairy foam, partial coalescence In this thesis, the interaction between emulsion droplets and expanding air/water interfaces was investigated. The

  2. Protonation, Hydrolysis, and Condensation of Mono- and Trifunctional Silanes at the Air/Water Interface

    OpenAIRE

    Britt, David W; Hlady, Vladimir

    1999-01-01

    The protonation, hydrolysis, and condensation kinetics of octadecyldimethylmethoxysilane (OMMS) and octadecyltrimethoxysilane (OTMS) at the air/water interface were investigated using a monolayer trough. OTMS chemical condensation within physically condensed phases was observed in transferred monolayers using fluorescence microscopy. Molecular area increases and decreases attributed to protonation and hydrolysis, respectively, of silane methoxy groups were measured by a surface balance. These...

  3. Molecular details of ovalbumin-pectin complexes at the air/water interface: A spectroscopic study

    NARCIS (Netherlands)

    Kudryashova, E.V.; Visser, A.J.W.G.; Hoek, A. van; Jongh, H.H.J. de

    2007-01-01

    To stabilize air-water interfaces, as in foams, the adsorption of surface-active components is a prerequisite. An approach to controlling the surface activity of proteins is noncovalent complex formation with a polyelectrolyte in the bulk phase. The molecular properties of egg white ovalbumin in a c

  4. Spreading of partially crystallized oil droplets on an air/water interface

    NARCIS (Netherlands)

    Hotrum, N.E.; Cohen Stuart, M.A.; Vliet, van T.; Aken, van G.A.

    2004-01-01

    The influence of crystalline fat on the amount and rate of oil spreading out of emulsion droplets onto either a clean or a protein-covered air/water interface was measured for ß-lactoglobulin stabilized emulsions prepared with either anhydrous milk fat or a blend of hydrogenated palm fat and sunflow

  5. Surface tension of ab initio liquid water at the water-air interface

    Science.gov (United States)

    Nagata, Yuki; Ohto, Tatsuhiko; Bonn, Mischa; Kühne, Thomas D.

    2016-05-01

    We report calculations on the surface tension of the water-air interface using ab initio molecular dynamics (AIMD) simulations. We investigate the influence of the cell size on surface tension of water from force field molecular dynamics simulations. We find that the calculated surface tension increases with increasing simulation cell size, thereby illustrating that a correction for finite size effects is essential for small systems that are customary in AIMD simulations. Moreover, AIMD simulations reveal that the use of a double-ζ basis set overestimates the experimentally measured surface tension due to the Pulay stress while more accurate triple and quadruple-ζ basis sets give converged results. We further demonstrate that van der Waals corrections critically affect the surface tension. AIMD simulations without the van der Waals correction substantially underestimate the surface tension while the van der Waals correction with the Grimme's D2 technique results in a value for the surface tension that is too high. The Grimme's D3 van der Waals correction provides a surface tension close to the experimental value. Whereas the specific choices for the van der Waals correction and basis sets critically affect the calculated surface tension, the surface tension is remarkably insensitive to the details of the exchange and correlation functionals, which highlights the impact of long-range interactions on the surface tension. Our simulated values provide important benchmarks, both for improving van der Waals corrections and AIMD simulations of aqueous interfaces.

  6. Photosensitized Formation of Secondary Organic Aerosols above the Air/Water Interface.

    Science.gov (United States)

    Bernard, F; Ciuraru, R; Boréave, A; George, C

    2016-08-16

    In this study, we evaluated photosensitized chemistry at the air-sea interface as a source of secondary organic aerosols (SOA). Our results show that, in addition to biogenic emissions, abiotic processes could also be important in the marine boundary layer. Photosensitized production of marine secondary organic aerosol was studied in a custom-built multiphase atmospheric simulation chamber. The experimental chamber contained water, humic acid (1-10 mg L(-1)) as a proxy for dissolved organic matter, and nonanoic acid (0.1-10 mM), a fatty acid proxy which formed an organic film at the air-water interface. Dark secondary reaction with ozone after illumination resulted in SOA particle concentrations in excess of 1000 cm(-3), illustrating the production of unsaturated compounds by chemical reactions at the air-water interface. SOA numbers via photosensitization alone and in the absence of ozone did not exceed background levels. From these results, we derived a dependence of SOA numbers on nonanoic acid surface coverage and dissolved organic matter concentration. We present a discussion on the potential role of the air-sea interface in the production of atmospheric organic aerosol from photosensitized origins. PMID:27434860

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

    Science.gov (United States)

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

    2015-07-23

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

  8. Ozonolysis of Uric Acid at the Air/Water Interface

    OpenAIRE

    Enami, Shinichi; Hoffmann, M. R.; Colussi, A. J.

    2008-01-01

    Uric acid (UA) epoxide, peroxide, and ozonide species produced in aqueous UA microdroplets exposed to O3(g) are detected by online mass spectrometry within ∼1 ms. UA conversions are independent of its initial concentration below ∼0.1 mM and are unaffected by addition of excess H2O2 or t-butanol. UA reactivity increases ∼380 times from pH 4 to 7, which is at variance with the pH-independent rates reported for the UA + O3(aq) reaction in bulk water. At pH ∼7, UA and ascorbic acid (AH2) microdro...

  9. Comparison of the dilational behaviour of adsorbed milk proteins at the air-water and oil-water interfaces.

    NARCIS (Netherlands)

    Williams, A.; Prins, A.

    1996-01-01

    The interfacial dilational properties of two milk proteins, β-casein and β-lactoglobulin, have been compared at the air-water and paraffin oil-water interfaces. The measurements were performed as a function of bulk protein concentration using a modified Langmuir trough technique at a frequency of 0.

  10. Mercury Exchange at the Air-Water-Soil Interface: An Overview of Methods

    Directory of Open Access Journals (Sweden)

    Fengman Fang

    2002-01-01

    Full Text Available An attempt is made to assess the present knowledge about the methods of determining mercury (Hg exchange at the air-water-soil interface during the past 20 years. Methods determining processes of wet and dry removal/deposition of atmospheric Hg to aquatic and terrestrial ecosystems, as well as methods determining Hg emission fluxes to the atmosphere from natural surfaces (soil and water are discussed. On the basis of the impressive advances that have been made in the areas relating to Hg exchange among air-soil-water interfaces, we analyzed existing problems and shortcomings in our current knowledge. In addition, some important fields worth further research are discussed and proposed.

  11. An investigation of channel flow with a smooth air-water interface

    Science.gov (United States)

    Madad, Reza; Elsnab, John; Chin, Cheng; Klewicki, Joseph; Marusic, Ivan

    2015-06-01

    Experiments and numerical simulation are used to investigate fully developed laminar and turbulent channel flow with an air-water interface as the lower boundary condition. Laser Doppler velocimetry measurements of streamwise and wall-normal velocity components are made over a range of Reynolds number based upon channel height and bulk velocity from 1100 to 4300, which encompasses the laminar, transitional and low Reynolds numbers turbulent regimes. The results show that the airflow statistics near the stationary wall are not significantly altered by the air-water moving interface and reflect those found in channel flows. The mean statistics on the water interface side largely exhibit results similar to simulated Poiseuille-Couette flow (PCF) with a solid moving wall. For second-order statistics, however, the simulation and experimental results show some discrepancies near the moving water surface, suggesting that a full two-phase simulation is required. A momentum and energy transport tubes analysis is investigated for laminar and turbulent PCFs. This analysis builds upon the classical notion of a streamtube and indicates that part of the energy from the pressure gradient is transported towards the stationary wall and is dissipated as heat inside the energy tubes, while the remainder is transmitted to the moving wall. For the experiments, the airflow energy is transmitted towards the water to overcome the drag force and drive the water forward; therefore, the amount of energy transferred to the water is higher than the energy transferred to a solid moving wall.

  12. Hydrodynamics of a fixed camphor boat at the air-water interface

    Science.gov (United States)

    Singh, Dhiraj; Akella, Sathish; Singh, Ravi; Mandre, Shreyas; Bandi, Mahesh

    2015-11-01

    A camphor tablet, when introduced at the air-water interface undergoes sublimation and the camphor vapour spreads radially outwards across the surface. This radial spreading of camphor is due to Marangoni forces setup by the camphor concentration gradient. We report experiments on the hydrodynamics of this process for a camphor tablet held fixed at the air-water interface. During the initial transient, the time-dependent spread radius R (t) of camphor scales algebraically with time t (R (t) ~t 1 / 2) in agreement with empirical scalings reported for spreading of volatile oils on water surface. But unlike surfactants, the camphor stops spreading when the influx of camphor from the tablet onto the air-water interface is balanced by the outflux of camphor due to evaporation, and a steady-state condition is reached. The spreading camphor however, shears the underlying fluid and sets up bulk convective flow. We explain the coupled steady-state dynamics between the interfacial camphor spreading and bulk convective flow with a boundary layer approximation, supported by experimental evidence. This work was supported by the Collective Interactions Unit, OIST Graduate University.

  13. Formation, disruption and mechanical properties of a rigid hydrophobin film at an air-water interface

    Science.gov (United States)

    Walker, Lynn; Kirby, Stephanie; Anna, Shelley; CMU Team

    Hydrophobins are small, globular proteins with distinct hydrophilic and hydrophobic regions that make them extremely surface active. The behavior of hydrophobins at surfaces has raised interest in their potential industrial applications, including use in surface coatings, food foams and emulsions, and as dispersants. Practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, both individually and in the presence of surfactants. Cerato-ulmin (CU) is a hydrophobin that has been shown to strongly stabilize air bubbles and oil droplets through the formation of a persistent protein film at the interface. In this work, we characterize the adsorption behavior of CU at air/water interfaces by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to strongly, irreversibly adsorb at air/water interfaces; the magnitude of the dilatational modulus increases with adsorption time and surface pressure, until the CU eventually forms a rigid film. The persistence of this film is tested through the addition of SDS, a strong surfactant, to the bulk. SDS is found to co-adsorb to interfaces pre-coated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU. These results lend insight into the complex interfacial interactions between hydrophobins and surfactants. Funding from GoMRI.

  14. Crystalline self-assembly into monolayers of folded oligomers at the air-water interface

    DEFF Research Database (Denmark)

    Lederer, K.; Godt, A.; Howes, P.B.;

    2000-01-01

    Insertion of the 115-bis(ethynylene)benzene unit as a rigid spacer into a linear alkyl chain, thus separating the two resulting stems by 9 Angstrom, induces chain folding at the air-water interface. These folded molecules self-assemble into crystalline monolayers at this interface, with the plane...... and position of the hydrophilic groups in the molecule. The molecules form ribbons with a higher crystal coherence in the direction of stacking between the molecular ribbons, and a lower coherence along the ribbon direction. A similar molecule, but with a spacer unit that imposes a 5 Angstrom separation...

  15. Separating Octadecyltrimethoxysilane Hydrolysis and Condensation at the Air/Water Interface through Addition of Methyl Stearate

    OpenAIRE

    Britt, David W; Hlady, Vladimir

    1999-01-01

    The hydrolysis and condensation of octadecyltrimethoxysilane (OTMS) at the air/water interface were monitored through molecular area changes at a constant surface pressure of 10 mN/m. The onset of condensation was delayed through the addition of methyl stearate (SME) acting as an inert filler molecule. In the absence of SME, complete gelation of OTMS required 30 h, during which time OTMS condensation occurred concomitantly with hydrolysis. In the presence of SME, the OTMS monolayer gelation r...

  16. Two-dimensional Insect Flight on an Air-Water Interface is a Chaotic Oscillator

    CERN Document Server

    Mukundarajan, Haripriya; Prakash, Manu

    2014-01-01

    Two-dimensional flapping wing insect flight on an air-water interface provides a successful foraging strategy to explore an ecological niche on the surface of a pond. However, the complex interplay of surface tension, aerodynamic forces, biomechanics and neural control that enables two-dimensional flight is unknown. Here we report the discovery of two-dimensional flight in the waterlily beetle Galerucella nymphaeae, which is the fastest reported propulsion mode for an insect on a fluid interface. Using kinematics derived from high-speed videography coupled with analytical models, we demonstrate that two-dimensional flight is a chaotic interfacial oscillator, thus significantly constraining the possible range of flight parameters. Discovery of this complex dynamics in two-dimensional flight on time scales similar to neural responses indicates the challenge of evolving active flight control on a fluid interface.

  17. Role of mixed boundaries on flow in open capillary channels with curved air-water interfaces.

    Science.gov (United States)

    Zheng, Wenjuan; Wang, Lian-Ping; Or, Dani; Lazouskaya, Volha; Jin, Yan

    2012-09-01

    Flow in unsaturated porous media or in engineered microfluidic systems is dominated by capillary and viscous forces. Consequently, flow regimes may differ markedly from conventional flows, reflecting strong interfacial influences on small bodies of flowing liquids. In this work, we visualized liquid transport patterns in open capillary channels with a range of opening sizes from 0.6 to 5.0 mm using laser scanning confocal microscopy combined with fluorescent latex particles (1.0 μm) as tracers at a mean velocity of ∼0.50 mm s(-1). The observed velocity profiles indicate limited mobility at the air-water interface. The application of the Stokes equation with mixed boundary conditions (i.e., no slip on the channel walls and partial slip or shear stress at the air-water interface) clearly illustrates the increasing importance of interfacial shear stress with decreasing channel size. Interfacial shear stress emerges from the velocity gradient from the adjoining no-slip walls to the center where flow is trapped in a region in which capillary forces dominate. In addition, the increased contribution of capillary forces (relative to viscous forces) to flow on the microscale leads to increased interfacial curvature, which, together with interfacial shear stress, affects the velocity distribution and flow pattern (e.g., reverse flow in the contact line region). We found that partial slip, rather than the commonly used stress-free condition, provided a more accurate description of the boundary condition at the confined air-water interface, reflecting the key role that surface/interface effects play in controlling flow behavior on the nanoscale and microscale.

  18. Atmospheric photochemistry at a fatty acid-coated air-water interface.

    Science.gov (United States)

    Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D James; George, Christian

    2016-08-12

    Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation. PMID:27516601

  19. Atmospheric photochemistry at a fatty acid-coated air-water interface

    Science.gov (United States)

    Rossignol, Stéphanie; Tinel, Liselotte; Bianco, Angelica; Passananti, Monica; Brigante, Marcello; Donaldson, D. James; George, Christian

    2016-08-01

    Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

  20. Root-soil air gap and resistance to water flow at the soil-root interface of Robinia pseudoacacia.

    Science.gov (United States)

    Liu, X P; Zhang, W J; Wang, X Y; Cai, Y J; Chang, J G

    2015-12-01

    During periods of water deficit, growing roots may shrink, retaining only partial contact with the soil. In this study, known mathematical models were used to calculate the root-soil air gap and water flow resistance at the soil-root interface, respectively, of Robinia pseudoacacia L. under different water conditions. Using a digital camera, the root-soil air gap of R. pseudoacacia was investigated in a root growth chamber; this root-soil air gap and the model-inferred water flow resistance at the soil-root interface were compared with predictions based on a separate outdoor experiment. The results indicated progressively greater root shrinkage and loss of root-soil contact with decreasing soil water potential. The average widths of the root-soil air gap for R. pseudoacacia in open fields and in the root growth chamber were 0.24 and 0.39 mm, respectively. The resistance to water flow at the soil-root interface in both environments increased with decreasing soil water potential. Stepwise regression analysis demonstrated that soil water potential and soil temperature were the best predictors of variation in the root-soil air gap. A combination of soil water potential, soil temperature, root-air water potential difference and soil-root water potential difference best predicted the resistance to water flow at the soil-root interface.

  1. Dynamic Study of Gemini Surfactant and Single-chain Surfactant at Air/Water Interface

    Institute of Scientific and Technical Information of China (English)

    Yi Jian CHEN; Gui Ying XU; Shi Ling YUAN; Hai Ying SUN

    2005-01-01

    Molecular dynamics (MD) simulation are used to study the properties of gemini surfactant of ethyl-α,ω-bis(dodecyldimethylammonium bromide) (C12C2C12) and dodecyltrimethylammonium bromide (DTAB) at the air/water interface, respectively. In the two systems,the surfactant concentrations are both 28 wt. %, and other conditions are also the same. After reaching the thermodynamic equilibrium, the concentration profiles, the radial distributions functions (RDF) and the mean squared displacement (MSD) are investigated. Theresults reveal that the surface activity of C12C2C12 suffactant is higher than DTAB surfactant.

  2. Formation of H-type liquid crystal dimer at air-water interface

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, C., E-mail: karthik.c@pilani.bits-pilani.ac.in; Gupta, Adbhut, E-mail: karthik.c@pilani.bits-pilani.ac.in; Joshi, Aditya, E-mail: karthik.c@pilani.bits-pilani.ac.in; Manjuladevi, V., E-mail: karthik.c@pilani.bits-pilani.ac.in; Gupta, Raj Kumar, E-mail: karthik.c@pilani.bits-pilani.ac.in [Department of Physics, Birla Institute of Technology and Science, Pilani, Rajasthan -333031 (India); Varia, Mahesh C.; Kumar, Sandeep [Raman Research Institute, Sadashivanagar, Bangalore - 560080 (India)

    2014-04-24

    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.

  3. Field observations of turbulent dissipation rate profiles immediately below the air-water interface

    Science.gov (United States)

    Wang, Binbin; Liao, Qian

    2016-06-01

    Near surface profiles of turbulence immediately below the air-water interface were measured with a free-floating Particle Image Velocimetry (PIV) system on Lake Michigan. The surface-following configuration allowed the system to measure the statistics of the aqueous-side turbulence in the topmost layer immediately below the water surface (z≈0˜15 cm, z points downward with 0 at the interface). Profiles of turbulent dissipation rate (ɛ) were investigated under a variety of wind and wave conditions. Various methods were applied to estimate the dissipation rate. Results suggest that these methods yield consistent dissipation rate profiles with reasonable scattering. In general, the dissipation rate decreases from the water surface following a power law relation in the top layer, ɛ˜z-0.7, i.e., the slope of the decrease was lower than that predicted by the wall turbulence theory, and the dissipation was considerably higher in the top layer for cases with higher wave ages. The measured dissipation rate profiles collapse when they were normalized with the wave speed, wave height, water-side friction velocity, and the wave age. This scaling suggests that the enhanced turbulence may be attributed to the additional source of turbulent kinetic energy (TKE) at the "skin layer" (likely due to micro-breaking), and its downward transport in the water column.

  4. Biogenic amine – surfactant interactions at the air-water interface.

    Science.gov (United States)

    Penfold, J; Thomas, R K; Li, P X

    2015-07-01

    The strong interaction between polyamines and anionic surfactants results in pronounced adsorption at the air-water interface and can lead to the formation of layered surface structures. The transition from monolayer adsorption to more complex surface structures depends upon solution pH, and the structure and molecular weight of the polyamine. The effects of manipulating the polyamine molecular weight and structure on the adsorption of the anionic surfactant sodium dodecyl sulphate at the air-water interface are investigated using neutron reflectivity and surface tension, for the biogenic amines putrescine, spermidine and spermine. The results show how changing the number of amine groups and the spacing between the amine groups impacts upon the surface adsorption. At lower pH, 3-7, and for the higher molecular weight polyamines, spermidine and spermine, ordered multilayer structures are observed. For putrescine at all pH and for spermidine and spermine at high pH, monolayer adsorption with enhanced surfactant adsorption compared to the pure surfactant is observed. The data for the biogenic amines, when compared with similar data for the polyamines ethylenediamine, diethylenetriamine and triethylenetetramine, indicate that the spacing between amines groups is more optimal for the formation of ordered surface multilayer structures.

  5. Hydration, Orientation, and Conformation of Methylglyoxal at the Air-Water Interface.

    Science.gov (United States)

    Wren, Sumi N; Gordon, Brittany P; Valley, Nicholas A; McWilliams, Laura E; Richmond, Geraldine L

    2015-06-18

    Aqueous-phase processing of methylglyoxal (MG) has been suggested to constitute an important source of secondary organic aerosol (SOA). The uptake of MG to aqueous particles is higher than expected because its carbonyl moieties can hydrate to form geminal diols, as well as because MG and its hydration products can undergo aldol condensation reactions to form larger oligomers in solution. MG is known to be surface active, but an improved description of its surface behavior is crucial to understanding MG-SOA formation. These studies investigate MG adsorption, focusing on its hydration state at the air-water interface, using a combined experimental and theoretical approach that involves vibrational sum frequency spectroscopy, molecular dynamics simulations, and density functional theory calculations. Together, the experimental and theoretical data show that MG exists predominantly in a singly hydrated state (diol) at the interface, with a diol-tetrol ratio at the surface higher than that for the bulk. In addition to exhibiting a strong surface activity, we find that MG significantly perturbs the water structure at the interface. The results have implications for understanding the atmospheric fate of methylglyoxal. PMID:25989368

  6. Catechol oxidation by ozone and hydroxyl radicals at the air-water interface.

    Science.gov (United States)

    Pillar, Elizabeth A; Camm, Robert C; Guzman, Marcelo I

    2014-12-16

    Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air-water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon the encounter of 40 ppbv-6.0 ppmv O3(g) with microdroplets containing [catechol] = 1-150 μM. While the previous pathway results in the instantaneous formation of mono- and polyhydroxylated aromatic rings (PHA) and chromophoric mono- and polyhydroxylated quinones (PHQ), a different channel produces oxo- and dicarboxylic acids of low molecular weight (LMW). The cleavage of catechol occurs at the 1,2 carbon-carbon bond at the air-water interface through the formation of (1) an ozonide intermediate, (2) a hydroperoxide, and (3) cis,cis-muconic acid. However, variable [catechol] and [O3(g)] can affect the ratio of the primary products (cis,cis-muconic acid and trihydroxybenzenes) and higher order products observed (PHA, PHQ, and LMW oxo- and dicarboxylic acids). Secondary processing is confirmed by mass spectrometry, showing the production of crotonic, maleinaldehydic, maleic, glyoxylic, and oxalic acids. The proposed pathway can contribute precursors to aqueous SOA (AqSOA) formation, converting aromatic hydrocarbons into polyfunctional species widely found in tropospheric aerosols with light-absorbing brown carbon. PMID:25423038

  7. Ultrafast Reorientational Dynamics of Leucine at the Air-Water Interface.

    Science.gov (United States)

    Donovan, Michael A; Yimer, Yeneneh Y; Pfaendtner, Jim; Backus, Ellen H G; Bonn, Mischa; Weidner, Tobias

    2016-04-27

    Ultrafast dynamics of protein side chains are involved in important biological processes such as ligand binding, protein folding, and hydration. In addition, the dynamics of a side chain can report on local environments within proteins. While protein side chain dynamics have been probed for proteins in solution with nuclear magnetic resonance and infrared methods for decades, information about side chain dynamics at interfaces is lacking. At the same time, the dynamics and motions of side chains can be particularly important for interfacial binding and protein-driven surface manipulation. We here demonstrate that ultrafast reorientation dynamics of leucine amino acids at interfaces can be recorded in situ and in real time using polarization- and time-resolved pump-probe sum frequency generation (SFG). Combined with molecular dynamics simulations, time-resolved SFG was used to probe the reorientation of the isopropyl methyl groups of l-leucine at the air-water interface. The data show that the methyl units reorient diffusively at an in plane rate of Dφ = 0.07 rad(2)/ps and an out of plane rate of Dθ = 0.05 rad(2)/ps. PMID:27057584

  8. [Diurnal variations of greenhouse gas fluxes at the water-air interface of aquaculture ponds in the Min River estuary].

    Science.gov (United States)

    Yang, Ping; Tong, Chuan; He, Qing-Hua; Huang, Jia-Fang

    2012-12-01

    Wetland reclamation and aquaculture is one of the main disturbance types in coastal wetlands. Diurnal variations of CO2, CH4 and N2O fluxes at the water-air interface were determined using a floating chambers + gas chromatography method in a shrimp pond, and a mixed culture pond of fish and shrimp in October in the Shanyutan Wetland of the Min River estuary, southeast China. Meanwhile, the meteorological indicators in ground surface and physical, chemical and biological indicators of surface water were also measured. CO2, CH4 and N2O fluxes at the water-air interface all demonstrated distinct diurnal variations. Both shrimp pond and mixed culture pond of fish and shrimp functioned as a sink of CO2 [the diurnal averaged CO2 fluxes were -48.79 and -105.25 mg x (m2 x h)(-1), respectively], and a source of CH4 [the diurnal averaged CH4 fluxes were 1.00 and 5.74 mg x (m2 x h)(-1), respectively]; the diurnal averaged CO2 and CH4 fluxes at the water-air interface of the mixed culture of fish and shrimp pond were higher than that of the shrimp pond. Greenhouse gas fluxes at the water-air interface from the aquaculture ponds were influenced by many factors. Multiple stepwise regression analysis showed that the concentration of Chlorophyll was the major factor affecting the CO2 fluxes, and the concentrations of SO4(2-) and PO4(3-) were the major factors affecting the CH4 fluxes at the water-air interface of the shrimp pond; whereas water temperature and Chlorophyll were the major factors affecting the CO2 fluxes, and dissolved oxygen, PO4(3-) and pH were the major factors affecting the CH4 fluxes at the water-air interface of the mixed culture pond of fish and shrimp. PMID:23379142

  9. Correlation reflectance spectroscopy of heterogeneous silver nanoparticle films upon compression at the air/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Gassin, Gaelle [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Harfouch, Yara El [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Benichou, Emmanuel [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Bachelier, Guillaume [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Russier-Antoine, Isabelle [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Jonin, Christian [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Roux, Stephane [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR CNRS 5260, Universite Claude Bernard Lyon 1, Batiment Claude Louis Berthollet, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Tillement, Olivier [Laboratoire de Physico-Chimie des Materiaux Luminescents, UMR CNRS 5260, Universite Claude Bernard Lyon 1, Batiment Claude Louis Berthollet, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France); Brevet, Pierre-Francois [Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, Universite Claude Bernard Lyon 1, Batiment Alfred Kastler, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex (France)

    2008-02-06

    Alkanethiol passivated silver nanoparticles were spread at an air/water interface to form a single monolayer film. The surface pressure isotherms and the UV-visible absorbance spectra of the film were recorded as a function of compression, whereas the dynamic behaviour was investigated by reflectance correlation spectroscopy. The film is shown to be inhomogeneous, formed by domains of particles separated by large areas of low particle density. Two distinct motions were observed: Brownian diffusion of the domains and their translational flow due to convection. From the characteristic diffusion time of the domains, and using a Stokes-Einstein analysis, the domain size is determined as a function of surface compression. The domains start to form and grow once a fixed average particle density is reached. Above this density threshold, the attractive van der Waals forces between the particles are dominating compared with the repulsion forces due to the alkanethiol chains.

  10. Mechanical tuning of molecular machines for nucleotide recognition at the air-water interface

    Directory of Open Access Journals (Sweden)

    Shinoda Satoshi

    2011-01-01

    Full Text Available Abstract Molecular machines embedded in a Langmuir monolayer at the air-water interface can be operated by application of lateral pressure. As part of the challenge associated with versatile sensing of biologically important substances, we here demonstrate discrimination of nucleotides by applying a cholesterol-armed-triazacyclononane host molecule. This molecular machine can discriminate ribonucleotides based on a twofold to tenfold difference in binding constants under optimized conditions including accompanying ions in the subphase and lateral surface pressures of its Langmuir monolayer. The concept of mechanical tuning of the host structure for optimization of molecular recognition should become a novel methodology in bio-related nanotechnology as an alternative to traditional strategies based on increasingly complex and inconvenient molecular design strategies.

  11. Anomalous spreading behaviour of polyethyleneglycoldistearate monolayers at air/water interface

    Indian Academy of Sciences (India)

    S John Collins; Aruna Dhathathreyan; T Ramasami

    2001-04-01

    Spreading behaviour of the dimeric surfactant polyethyleneglycoldistearate (PEGDS) monolayer at air/water interface has been studied using surface pressure-area ( -) isotherms as a function of temperature. The isotherms show a plateau suggesting a transition between a liquid expanded (LE) and a condensed state. The condensed state possibly arises due to nucleation and growth of multilayers from the monolayer. Isobaric measurements of both - and - at constant area show transitions at = 295 K. These plots suggest a melting followed by formation of condensed microcrystallites. Structure optimization carried out using various angles of orientation of the alkyl tails with respect to the backbone in PEGDS reveals tilt transitions of the tails in different states which can be related to the packing behaviour seen in the isotherms. Optical microscopy has been used to confirm the structures in these states.

  12. Surface Pressure Study of Lipid Aggregates at the Air Water Interface

    Science.gov (United States)

    Shew, Woody; Ploplis Andrews, Anna

    1996-11-01

    Qualitative and quantitative descriptions of the growth of fatty acid aggregates on a water/air interface were made by analyzing surface pressure measurements taken with a Langmuir Balance. High concentrations of palmitic acid, lauric acid, myristic acid, and also phosphatidylethanolamine in solution with chloroform were applied with a syringe to the surface of the Langmuir Balance and surface pressure was monitored as aggregates assembled spontaneously. The aggregation process for palmitic acid was determined to consist of three distinct parts. Exponential curves were fit to the individual regions of the data and growth and decay constants were determined. Surface pressure varied in very complex ways for lauric acid, myristic acid, and phosphatidylethanolamine yet kinetic measurements yield qualitative information about assembly of those aggregates. This research was supported by NSF Grant No. DMR-93-22301.

  13. DNS and measurements of scalar transfer across an air-water interface during inception and growth of Langmuir circulation

    Science.gov (United States)

    Hafsi, A.; Ma, Y.; Buckley, M.; Tejada-Martinez, A. E.; Veron, F.

    2016-05-01

    Direct numerical simulations (DNS) of an initially quiescent coupled air-water interface driven by an air flow with free stream speed of 5 m/s have been conducted and scalar transfer from the air side to the water side and subsequent vertical transport in the water column have been analysed. Two simulations are compared: one with a freely deforming interface, giving rise to gravity-capillary waves and aqueous Langmuir turbulence (LT) characterized by small-scale (centimeter-scale) Langmuir cells (LC), and the other with the interface intentionally held flat, i.e., without LC. It is concluded that LT serves to enhance vertical transport of the scalar in the water side and in the process increases scalar transfer efficiency from the air side to the water side relative to the shear-dominated turbulence in the flat interface case. Furthermore, transition to LT was observed to be accompanied by a spike in scalar flux characterized by an order of magnitude increase. These episodic flux increases, if linked to gusts and overall unsteadiness in the wind field, are expected to be an important contributor in determining the long-term average of the air-sea gas fluxes.

  14. Investigation of adsorption of surfactant at the air-water interface with quantum chemistry method

    Institute of Scientific and Technical Information of China (English)

    CHEN MeiLing; WANG ZhengWu; WANG HaiJun; ZHANG GeXin; TAO FuMing

    2007-01-01

    Density functional theory (DFT) of quantum chemistry was used to optimize the configuration of the anionic surfactant complexes CH3(CH2)7OSO-3(H2O)n (n=0-6) and calculate their molecular frequencies at the B3LYP/6-311+G* level. The interaction of CH3(CH2)7OSO-3 with 1 to 6 water molecules was investigated at the air-water interface with DFT. The results revealed that the hydration shell was formed in the form of H-bond between the hydrophilic group of CH3(CH2)7OSO-3 and 6 waters. The strength of H-bonds belongs to medium. Binding free energy revealed that the hydration shell was stable. The increase of the number of water molecules will cause increases of the total charge of hydrophilic group and S10-O9-C8 bond angle, but decreases of the alkyl chain length and the bond lengths of S10-O11,S10-O12 as well as S10-O13, respectively.

  15. Surface shear rheology of WPI-monoglyceride mixed films spread at the air-water interface.

    Science.gov (United States)

    Carrera Sánchez, Cecilio; Rodríguez Patino, Juan M

    2004-07-01

    Surface shear viscosity of food emulsifiers may contribute appreciably to the long-term stability of food dispersions (emulsions and foams). In this work we have analyzed the structural, topographical, and shear characteristics of a whey protein isolate (WPI) and monoglyceride (monopalmitin and monoolein) mixed films spread on the air-water interface at pH 7 and at 20 degrees C. The surface shear viscosity (etas) depend on the surface pressure and on the composition of the mixed film. The surface shear viscosity varies greatly with the surface pressure. In general, the greater the surface pressure, the greater are the values of etas. The values of etas for the mixed WPI-monoolein monolayer were more than one order of magnitude lower than those for a WPI-monopalmitin mixed film, especially at the higher surface pressures. At higher surface pressures, collapsed WPI residues may be displaced from the interface by monoglyceride molecules with important repercussions on the shear characteristics of the mixed films. A shear-induced change in the topography and a segregation between domains of the film forming components were also observed. The displacement of the WPI by the monoglycerides is facilitates under shear conditions, especially for WPI-monoolein mixed films.

  16. Spread Films of Human Serum Albumin at the Air-Water Interface: Optimization, Morphology, and Durability.

    Science.gov (United States)

    Campbell, Richard A; Ang, Joo Chuan; Sebastiani, Federica; Tummino, Andrea; White, John W

    2015-12-22

    It has been known for almost one hundred years that a lower surface tension can be achieved at the air-water interface by spreading protein from a concentrated solution than by adsorption from an equivalent total bulk concentration. Nevertheless, the factors that control this nonequilibrium process have not been fully understood. In the present work, we apply ellipsometry, neutron reflectometry, X-ray reflectometry, and Brewster angle microscopy to elaborate the surface loading of human serum albumin in terms of both the macroscopic film morphology and the spreading dynamics. We show that the dominant contribution to the surface loading mechanism is the Marangoni spreading of protein from the bulk of the droplets rather than the direct transfer of their surface films. The films can be spread on a dilute subphase if the concentration of the spreading solution is sufficient; if not, dissolution of the protein occurs, and only a textured adsorbed layer slowly forms. The morphology of the spread protein films comprises an extended network with regions of less textured material or gaps. Further, mechanical cycling of the surface area of the spread films anneals the network into a membrane that approach constant compressibility and has increased durability. Our work provides a new perspective on an old problem in colloid and interface science. The scope for optimization of the surface loading mechanism in a range of systems leading to its exploitation in deposition-based technologies in the future is discussed. PMID:26607026

  17. Langmuir and Langmuir-Blodgett films of capsules of haemoglobin at air/water and solid/air interfaces

    Indian Academy of Sciences (India)

    J Maheshkumar; A Dhathathreyan

    2013-03-01

    Organized assemblies of capsules of haemoglobin (Hb), in the size range of 0.1 to 0.3 in Langmuir films have been studied at air/water interface below and above the isoelectric point. Spread films of these organizates suggest that there is no expulsion of individual particles or particle assemblies at the interface and the particles are stable. Dynamic surface tension and the associated dilational and shear visco-elasticity in these films suggest that the capsules are highly elastic. Multilayer films of the capsules using Langmuir-Blodgett technique have been fabricated by sequential deposition on solid surfaces. These films have been characterized by circular dichroism spectroscopy (CD), atomic force microscopy (AFM), quartz crystal microbalance (QCM) and Fourier transform infrared with reflection absorption spectroscopy (FTIR-RAS). No appreciable change in the secondary structural features of Hb is seen from CD studies indicating the stability of the protein in these organized assemblies. Sizes of these capsules change near the isoelectric point and large swollen multiwalled capsules are formed. The elastic films of capsules of Hb provide a useful post preparation approach for modification of the surface roughness, porosity, and permeability of pre-assembled polypeptide microcapsules.

  18. Hydrogen bonding and orientation effects on the accommodation of methylamine at the air-water interface

    Science.gov (United States)

    Hoehn, Ross D.; Carignano, Marcelo A.; Kais, Sabre; Zhu, Chongjing; Zhong, Jie; Zeng, Xiao C.; Francisco, Joseph S.; Gladich, Ivan

    2016-06-01

    Methylamine is an abundant amine compound detected in the atmosphere which can affect the nature of atmospheric aerosol surfaces, changing their chemical and optical properties. Molecular dynamics simulation results show that methylamine accommodation on water is close to unity with the hydrophilic head group solvated in the interfacial environment and the methyl group pointing into the air phase. A detailed analysis of the hydrogen bond network indicates stronger hydrogen bonds between water and the primary amine group at the interface, suggesting that atmospheric trace gases will likely react with the methyl group instead of the solvated amine site. These findings suggest new chemical pathways for methylamine acting on atmospheric aerosols in which the methyl group is the site of orientation specific chemistry involving its conversion into a carbonyl site providing hydrophilic groups for uptake of additional water. This conversion may explain the tendency of aged organic aerosols to form cloud condensation nuclei. At the same time, formation of NH2 radical and formaldehyde is suggested to be a new source for NH2 radicals at aerosol surfaces, other than by reaction of absorbed NH3. The results have general implications for the chemistry of other amphiphilic organics, amines in particular, at the surface of atmospherically relevant aerosols.

  19. Effects of thermodynamics parameters on mass transfer of volatile pollutants at air-water interface

    Directory of Open Access Journals (Sweden)

    Li-ping Chen

    2015-07-01

    Full Text Available A transient three-dimensional coupling model based on the compressible volume of fluid (VOF method was developed to simulate the transport of volatile pollutants at the air-water interface. VOF is a numerical technique for locating and tracking the free surface of water flow. The relationships between Henry’s constant, thermodynamics parameters, and the enlarged topological index were proposed for nonstandard conditions. A series of experiments and numerical simulations were performed to study the transport of benzene and carbinol. The simulation results agreed with the experimental results. Temperature had no effect on mass transfer of pollutants with low transfer free energy and high Henry’s constant. The temporal and spatial distribution of pollutants with high transfer free energy and low Henry’s constant was affected by temperature. The total enthalpy and total transfer free energy increased significantly with temperature, with significant fluctuations at low temperatures. The total enthalpy and total transfer free energy increased steadily without fluctuation at high temperatures.

  20. A comparison of recent methods for modelling mercury fluxes at the air-water interface

    Directory of Open Access Journals (Sweden)

    Fantozzi L.

    2013-04-01

    Full Text Available The atmospheric pathway of the global mercury flux is known to be the primary source of mercury contamination to most threatened aquatic ecosystems. Notwithstanding, the emission of mercury from surface water to the atmosphere is as much as 50% of total annual emissions of this metal into the atmosphere. In recent years, much effort has been made in theoretical and experimental researches to quantify the total mass flux of mercury to the atmosphere. In this study the most recent atmospheric modelling methods and the information obtained from them are presented and compared using experimental data collected during the Oceanographic Campaign Fenice 2011 (25 October – 8 November 2011, performed on board the Research Vessel (RV Urania of the CNR in the framework of the MEDOCEANOR ongoing program. A strategy for future numerical model development is proposed which is intended to gain a better knowledge of the long-term effects of meteo-climatic drivers on mercury evasional processes, and would provide key information on gaseous Hg exchange rates at the air-water interface.

  1. Substrateless Welding of Self-Assembled Silver Nanowires at Air/Water Interface.

    Science.gov (United States)

    Hu, Hang; Wang, Zhongyong; Ye, Qinxian; He, Jiaqing; Nie, Xiao; He, Gufeng; Song, Chengyi; Shang, Wen; Wu, Jianbo; Tao, Peng; Deng, Tao

    2016-08-10

    Integrating connected silver nanowire networks with flexible polymers has appeared as a popular way to prepare flexible electronics. To reduce the contact resistance and enhance the connectivity between silver nanowires, various welding techniques have been developed. Herein, rather than welding on solid supporting substrates, which often requires complicated transferring operations and also may pose damage to heat-sensitive substrates, we report an alternative approach to prepare easily transferrable conductive networks through welding of self-assembled silver nanowires at the air/water interface using plasmonic heating. The intriguing welding behavior of partially aligned silver nanowires was analyzed with combined experimental observation and theoretical modeling. The underlying water not only physically supports the assembled silver nanowires but also buffers potential overheating during the welding process, thereby enabling effective welding within a broad range of illumination power density and illumination duration. The welded networks could be directly integrated with PDMS substrates to prepare high-performance stable flexible heaters that are stretchable, bendable, and can be easily patterned to explore selective heating applications. PMID:27437907

  2. Interfacial behaviors of PMMA-PEO block copolymers at the air/water interface

    Institute of Scientific and Technical Information of China (English)

    CHENG Caixia; JIAO Tifeng; TANG Rupei; LIU Minghua; XI Fu

    2005-01-01

    Diblock copolymer of PMMA291-b-PEO114 and triblock copolymer of PMMA120-b- PEO227-b-PMMA120 were synthesized and their interfacial properties at the air-water interface were investigated, where both blocks of polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are surface active but the former is soluble in water while the latter is not. Both the block copolymers could form monolayers with two obvious transition regions. The first transition point is around 10 mN/m, which could be assigned to the pancake-brush change of the PEO chains. The other is around 18 mN/m, which could be ascribed to the condensed packing of PMMA. The surface morphological changes during the compression of the Langmuir monolayers are investigated by using the AFM and SEM methods for the films deposited at different surface pressure or molecular areas. At a lower surface pressure, a typical morphology of PEO-con- taining lipopolymers is observed. Upon compression, sphere-dominant morphologies were observed. While the diblock copolymer is easy to folding, the triblock copolymer is in favor of formation of circular domains through vesiculation.

  3. THIN-FILM BEHAVIOR OF POLY(METHYL METHACRYLATES) .1. MONOLAYERS AT THE AIR-WATER-INTERFACE

    NARCIS (Netherlands)

    BRINKHUIS, RHG; SCHOUTEN, AJ

    1991-01-01

    The monolayer behavior of PMMA of varying tacticities at the air-water interface was studied. A difference in lateral cohesive energy is argued to be responsible for the fact that the pressure area isotherms of isotactic PMMA deviate strongly from those of syndiotactic PMMA. At low surface pressures

  4. Thin-Film Behavior of Poly(methyl methacrylates). 1. Monolayers at the Air-Water Interface

    NARCIS (Netherlands)

    Brinkhuis, R.H.G.; Schouten, A.J.

    1991-01-01

    The monolayer behavior of PMMA of varying tacticities at the air-water interface was studied. A difference in lateral cohesive energy is argued to be responsible for the fact that the pressure area isotherms of isotactic PMMA deviate strongly from those of syndiotactic PMMA. At low surface pressures

  5. Protein Exposed Hydrophobicity Reduces the Kinetic Barrier for Adsorption of Ovalbumin to the Air-Water Interface

    NARCIS (Netherlands)

    Wierenga, P.A.; Meinders, M.B.J.; Egmond, M.R.; Voragen, F.A.G.J.; Jongh, H.H.J. de

    2003-01-01

    Using native and caprylated ovalbumin, the role of exposed hydrophobicity on the kinetics of protein adsorption to the air - water interface is studied. First, changes in the chemical properties of the protein upon caprylation were characterized followed by measurement of the changes in adsorption k

  6. Protein exposed hydrophobicity reduces the kinetic barrier for adsoption of ovalbumin to the air-water interface.

    NARCIS (Netherlands)

    Wierenga, P.A.; Meinders, M.B.J.; Egmond, M.R.; Voragen, A.G.J.

    2003-01-01

    Using native and caprylated ovalbumin, the role of exposed hydrophobicity on the kinetics of protein adsorption to the air-water interface is studied. First, changes in the chemical properties of the protein upon caprylation were characterized followed by measurement of the changes in adsorption kin

  7. epi-Fluorescence imaging at the air-water interface of fibrillization of bovine serum albumin and human insulin.

    Science.gov (United States)

    Sessions, Kristen; Sacks, Stuart; Li, Shanghao; Leblanc, Roger M

    2014-08-18

    Protein fibrillization is associated with many devastating neurodegenerative diseases. This process has been studied using spectroscopic and microscopic methods. In this study, epi-fluorescence at the air-water interface was developed as an innovative technique for observing fibrillization of bovine serum albumin and human insulin. PMID:24976597

  8. Chiral Discrimination in N-(O, O-dialkyl)phosphoamino Acid Monolayers at the Air-water Interface

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, chiral discrimination in N-(O,O-dialkyl)phosphoamino acid monolayers at the air/water interface was studied and it was revealed that the D:L=1:1 racemic monolayer of N-(O, O-dihexadecyl)phosphoalanine is packed more densely in solid phase while shows a higher LE to LC transition pressure than the enantiomeric ones.

  9. Formation of a Rigid Hydrophobin Film and Disruption by an Anionic Surfactant at an Air/Water Interface.

    Science.gov (United States)

    Kirby, Stephanie M; Zhang, Xujun; Russo, Paul S; Anna, Shelley L; Walker, Lynn M

    2016-06-01

    Hydrophobins are amphiphilic proteins produced by fungi. Cerato-ulmin (CU) is a hydrophobin that has been associated with Dutch elm disease. Like other hydrophobins, CU stabilizes air bubbles and oil droplets through the formation of a persistent protein film at the interface. The behavior of hydrophobins at surfaces has raised interest in their potential applications, including use in surface coatings, food foams, and emulsions and as dispersants. The practical use of hydrophobins requires an improved understanding of the interfacial behavior of these proteins, alone and in the presence of added surfactants. In this study, the adsorption behavior of CU at air/water interfaces is characterized by measuring the surface tension and interfacial rheology as a function of adsorption time. CU is found to adsorb irreversibly at air/water interfaces. The magnitude of the dilatational modulus increases with adsorption time and surface pressure until CU eventually forms a rigid film. The persistence of this film is tested through the sequential addition of strong surfactant sodium dodecyl sulfate (SDS) to the bulk liquid adjacent to the interface. SDS is found to coadsorb to interfaces precoated with a CU film. At high concentrations, the addition of SDS significantly decreases the dilatational modulus, indicating disruption and displacement of CU by SDS. Sequential adsorption results in mixed layers with properties not observed in interfaces generated from complexes formed in the bulk. These results lend insight to the complex interfacial interactions between hydrophobins and surfactants. PMID:27164189

  10. Two-dimensional crystallography of amphiphilic molecules at the air-water interface

    DEFF Research Database (Denmark)

    Jacquemain, D.; Grayer Wolf, S.; Leveiller, F.;

    1992-01-01

    The advent of well-collimated, high-intensity synchrotron X-ray sources and the consequent development of surface-specific X-ray diffraction and fluorescence techniques have recently revolutionized the study of Langmuir monolayers at the air-liquid interface. These methods allowed for the first t...

  11. Gas transfer at the air-water interface in a turbulent flow environment

    Energy Technology Data Exchange (ETDEWEB)

    Herlina

    2005-07-01

    The gas transfer process across the air-water interface in a bottom-shear-induced turbulent environment was investigated to gain improved fundamental understanding of the physical mechanisms that control the process. For this purpose, it is necessary to reveal the hydrodynamics of the flow field as well as the molecular diffusion and the turbulent transport contributions to the total flux. Therefore, detailed laboratory experiments were conducted to obtain this information. The experiments were performed in a grid-stirred tank using a combined Particle Image Velocimetry - Laser Induced Fluorescence (PIV-LIF) technique that has been developed for these near surface gas transfer measurements. The turbulence characteristics of the velocity near the interface were acquired from the PIV measurements and showed generally good agreement with the theoretical profiles from Hunt and Graham (1978). The LIF technique enabled visualization of the planar concentration fields which provided more insight into the gas transfer mechanisms. The high data resolution allowed detailed quantification of the concentration distribution within the thin aqueous boundary layer. The interrelated interpretation of the obtained results suggest that the gas transfer process is controlled by a spectrum of different eddy sizes and the gas transfer at different turbulence levels can be associated to certain eddy sizes. For high turbulence levels the gas transfer should be asymptotic to the small eddy model, whereas for low turbulence level to the large eddy model. The new results of turbulent mass flux should aid as an excellent database in refining numerical models and developing more accurate models for the prediction of the transfer velocity. (orig.)

  12. Interfacial Interactions and Nanostructure Changes in DPPG/HD Monolayer at the Air/Water Interface

    Directory of Open Access Journals (Sweden)

    Huaze Zhu

    2015-01-01

    Full Text Available Lung surfactant (LS plays a crucial role in regulating surface tension during normal respiration cycles by decreasing the work associated with lung expansion and therefore decreases the metabolic energy consumed. Monolayer surfactant films composed of a mixture of phospholipids and spreading additives are of optional utility for applications in lung surfactant-based therapies. A simple, minimal model of such a lung surfactant system, composed of 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-(1-gylcerol] (DPPG and hexadecanol (HD, was prepared, and the surface pressure-area (π-A isotherms and nanostructure characteristics of the binary mixture were investigated at the air/water interface using a combination of Langmuir-Blodgett (LB and atomic force microscopy (AFM techniques. Based on the regular solution theory, the miscibility and stability of the two components in the monolayer were analyzed in terms of compression modulus (Cs-1 , excess Gibbs free energy (ΔGexcπ , activity coefficients (γ, and interaction parameter (ξ. The results of this paper provide valuable insight into basic thermodynamics and nanostructure of mixed DPPG/HD monolayers; it is helpful to understand the thermodynamic behavior of HD as spreading additive in LS monolayer with a view toward characterizing potential improvements to LS performance brought about by addition of HD to lung phospholipids.

  13. Gas exchange rates across the sediment-water andd air-water interfaces in south San Francisco Bay

    International Nuclear Information System (INIS)

    Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainity of the determinations, about 20%. The annual average of bethic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water inteface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2--6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models

  14. Multi-scale modeling of mycosubtilin lipopeptides at the air/water interface: structure and optical second harmonic generation.

    Science.gov (United States)

    Loison, Claire; Nasir, Mehmet Nail; Benichou, Emmanuel; Besson, Françoise; Brevet, Pierre-François

    2014-02-01

    Monolayers of the lipopeptide mycosubtilin are studied at the air/water interface. Their structure is investigated using molecular dynamics simulations. All-atom models suggest that the lipopeptide is flexible and aggregates at the interface. To achieve simulation times of several microseconds, a coarse-grained (CG) model based on the MARTINI force field was also used. These CG simulations describe the formation of half-micelles at the interface for surface densities up to 1 lipopeptide per nm(2). In these aggregates, the tyrosine side chain orientation is found to be constrained: on average, its main axis, as defined along the C-OH bond, aligns along the interface normal and points towards the air side. The origin of the optical second harmonic generation (SHG) from mycosubtilin monolayers at the air/water interface is also investigated. The molecular hyperpolarizability of the lipopeptide is obtained from quantum chemistry calculations. The tyrosine side chain contribution to the hyperpolarizability is found to be dominant. The orientation distribution of tyrosine, associated with a dominant hyperpolarizability component along the C-OH bond of the tyrosine, yields a ratio of the susceptibility elements χ((2))(ZZZ)/χ((2))(ZXX) consistent with the experimental measurements recently reported by M. N. Nasir et al. [Phys. Chem. Chem. Phys., 2013, 15, 19919]. PMID:24346061

  15. Surface Tension Drives the Orientation of Crystals at the Air-Water Interface.

    Science.gov (United States)

    Chevalier, Nicolas R; Guenoun, Patrick

    2016-07-21

    The fabrication of oriented crystalline thin films is essential for a range of applications ranging from semiconductors to optical components, sensors, and catalysis. Here we show by depositing micrometric crystal particles on a liquid interface from an aerosol phase that the surface tension of the liquid alone can drive the crystallographic orientation of initially randomly oriented particles. The X-ray diffraction patterns of the particles at the interface are identical to those of a monocrystalline sample cleaved along the {104} (CaCO3) or {111} (CaF2) face. We show how this orientation effect can be used to produce thin coatings of oriented crystals on a solid substrate. These results also have important implications for our understanding of heterogeneous crystal growth beneath amphiphile monolayers and for 2D self-assembly processes at the air-liquid interface. PMID:27389283

  16. Energy and water vapor transport across a simplified cloud-clear air interface

    CERN Document Server

    Gallana, Luca; De Santi, Francesca; Iovieno, Michele; Tordella, Daniela

    2015-01-01

    We consider a simplified physics of the could interface where condensation, evaporation and radiation are neglected and momentum, thermal energy and water vapor transport is represented in terms of the Boussinesq model coupled to a passive scalar transport equation for the vapor. The interface is modeled as a layer separating two isotropic turbulent regions with different kinetic energy and vapor concentration. In particular, we focus on the small scale part of the inertial range as well as on the dissipative range of scales which are important to the micro-physics of warm clouds. We have numerically investigated stably stratified interfaces by locally perturbing at an initial instant the standard temperature lapse rate at the cloud interface and then observing the temporal evolution of the system. When the buoyancy term becomes of the same order of the inertial one, we observe a spatial redistribution of the kinetic energy which produce a concomitant pit of kinetic energy within the mixing layer. In this sit...

  17. Dissecting the Molecular Structure of the Air/Water Interface from Quantum Simulations of the Sum-Frequency Generation Spectrum.

    Science.gov (United States)

    Medders, Gregory R; Paesani, Francesco

    2016-03-23

    The molecular characterization of the air/water interface is a key step in understanding fundamental multiphase phenomena ranging from heterogeneous chemical processes in the atmosphere to the hydration of biomolecules. The apparent simplicity of the air/water interface, however, masks an underlying complexity associated with the dynamic nature of the water hydrogen-bond network that has so far hindered an unambiguous characterization of its microscopic properties. Here, we demonstrate that the application of quantum many-body molecular dynamics, which enables spectroscopically accurate simulations of water from the gas to the condensed phase, leads to a definitive molecular-level picture of the interface region. For the first time, excellent agreement is obtained between the simulated vibrational sum-frequency generation spectrum and the most recent state-of-the-art measurements, without requiring any empirical frequency shift or ad hoc scaling of the spectral intensity. A systematic dissection of the spectral features demonstrates that a rigorous representation of nuclear quantum effects as well as of many-body energy and electrostatic contributions is necessary for a quantitative reproduction of the experimental data. The unprecedented accuracy of the simulations presented here indicates that quantum many-body molecular dynamics can enable predictive studies of aqueous interfaces, which by complementing analogous experimental measurements will provide unique molecular insights into multiphase and heterogeneous processes of relevance in chemistry, biology, materials science, and environmental research. PMID:26943730

  18. Effect of glycyrrhetinic acid on lipid raft model at the air/water interface.

    Science.gov (United States)

    Sakamoto, Seiichi; Uto, Takuhiro; Shoyama, Yukihiro

    2015-02-01

    To investigate an interfacial behavior of the aglycon of glycyrrhizin (GC), glycyrrhetinic acid (GA), with a lipid raft model consisting of equimolar ternary mixtures of N-palmitoyl sphingomyelin (PSM), dioleoylphosphatidylcholine (DOPC), and cholesterol (CHOL), Langmuir monolayer techniques were systematically conducted. Surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms showed that the adsorbed GA at the air/water interface was desorbed into the bulk upon compression of the lipid monolayer. In situ morphological analysis by Brewster angle microscopy and fluorescence microscopy revealed that the raft domains became smaller as the concentrations of GA in the subphase (CGA) increased, suggesting that GA promotes the formation of fluid networks related to various cellular processes via lipid rafts. In addition, ex situ morphological analysis by atomic force microscopy revealed that GA interacts with lipid raft by lying down at the surface. Interestingly, the distinctive striped regions were formed at CGA=5.0 μM. This phenomenon was observed to be induced by the interaction of CHOL with adsorbed GA and is involved in the membrane-disrupting activity of saponin and its aglycon. A quantitative comparison of GA with GC (Sakamoto et al., 2013) revealed that GA interacts more strongly with the raft model than GC in the monolayer state. Various biological activities of GA are known to be stronger than those of GC. This fact allows us to hypothesize that differences in the interactions of GA/GC with the model monolayer correlate to their degree of exertion for numerous activities.

  19. Structural properties of phosphatidylcholine in a monolayer at the air/water interface

    DEFF Research Database (Denmark)

    Vaknin, D.; Kjær, K.; Als-Nielsen, J.;

    1991-01-01

    conception of the interface structure. It is found that in the LC phase (which is analogous to the L-beta phase in vesicle dispersions) the head group is interpenetrated with subphase water (4 +/- 2.5 molecules per lipid) and the average tilt angle of the hydrophobic chains from the surface normal is 33...

  20. Toward a unified picture of the water self-ions at the air-water interface: a density functional theory perspective.

    Science.gov (United States)

    Baer, Marcel D; Kuo, I-Feng W; Tobias, Douglas J; Mundy, Christopher J

    2014-07-17

    The propensities of the water self-ions, H3O(+) and OH(-), for the air-water interface have implications for interfacial acid-base chemistry. Despite numerous experimental and computational studies, no consensus has been reached on the question of whether or not H3O(+) and/or OH(-) prefer to be at the water surface or in the bulk. Here we report a molecular dynamics simulation study of the bulk vs interfacial behavior of H3O(+) and OH(-) that employs forces derived from density functional theory with a generalized gradient approximation exchange-correlation functional (specifically, BLYP) and empirical dispersion corrections. We computed the potential of mean force (PMF) for H3O(+) as a function of the position of the ion in the vicinity of an air-water interface. The PMF suggests that H3O(+) has equal propensity for the interface and the bulk. We compare the PMF for H3O(+) to our previously computed PMF for OH(-) adsorption, which contains a shallow minimum at the interface, and we explore how differences in solvation of each ion at the interface vs in the bulk are connected with interfacial propensity. We find that the solvation shell of H3O(+) is only slightly dependent on its position in the water slab, while OH(-) partially desolvates as it approaches the interface, and we examine how this difference in solvation behavior is manifested in the electronic structure and chemistry of the two ions. PMID:24762096

  1. Adsorption, Ordering, and Local Environments of Surfactant-Encapsulated Polyoxometalate Ions Probed at the Air-Water Interface.

    Science.gov (United States)

    Doughty, Benjamin; Yin, Panchao; Ma, Ying-Zhong

    2016-08-16

    The continued development and application of surfactant-encapsulated polyoxometalates (SEPs) relies on understanding the ordering and organization of species at their interface and how these are impacted by the various local environments to which they are exposed. Here, we report on the equilibrium properties of two common SEPs adsorbed to the air-water interface and probed with surface-specific vibrational sum-frequency generation (SFG) spectroscopy. These results reveal clear shifts in vibrational band positions, the magnitude of which scales with the charge of the SEP core, which is indicative of a static field effect on the surfactant coating and the associated local chemical environment. This static field also induces ordering in surrounding water molecules that is mediated by charge screening via the surface-bound surfactants. From these SFG measurements, we are able to show that Mo132-based SEPs are more polar than Mo72V30 SEPs. Disorder in the surfactant chain packing at the highly curved SEP surfaces is attributed to large conic volumes that can be sampled without interactions with neighboring chains. Measurements of adsorption isotherms yield free energies of adsorption to the air-water interface of -46.8 ± 0.4 and -44.8 ± 1.2 kJ/mol for the Mo132 and Mo72V30 SEPs, respectively, indicating a strong propensity for the fluid surface. The influence of intermolecular interactions on the surface adsorption energies is discussed. PMID:27452922

  2. Reactivity of aldehydes at the air-water interface. Insights from molecular dynamics simulations and ab initio calculations.

    Science.gov (United States)

    Martins-Costa, Marilia T C; García-Prieto, Francisco F; Ruiz-López, Manuel F

    2015-02-14

    Understanding the influence of solute-solvent interactions on chemical reactivity has been a subject of intense research in the last few decades. Theoretical studies have focused on bulk solvation phenomena and a variety of models and methods have been developed that are now widely used by both theoreticians and experimentalists. Much less attention has been paid, however, to processes that occur at liquid interfaces despite the important role such interfaces play in chemistry and biology. In this study, we have carried out sequential molecular dynamics simulations and quantum mechanical calculations to analyse the influence of the air-water interface on the reactivity of formaldehyde, acetaldehyde and benzaldehyde, three simple aldehydes of atmospheric interest. The calculated free-energy profiles exhibit a minimum at the interface, where the average reactivity indices may display large solvation effects. The study emphasizes the role of solvation dynamics, which are responsible for large fluctuations of some molecular properties. We also show that the photolysis rate constant of benzaldehyde in the range 290-308 nm increases by one order of magnitude at the surface of a water droplet, from 2.7 × 10(-5) s(-1) in the gas phase to 2.8 × 10(-4) s(-1) at the air-water interface, and we discuss the potential impact of this result on the chemistry of the troposphere. Experimental data in this domain are still scarce and computer simulations like those presented in this work may provide some insights that can be useful to design new experiments.

  3. Palmitate Luciferin: A molecular design for the second harmonic generation study of ion complexation at the air-water interface

    International Nuclear Information System (INIS)

    A molecular organic chromophore, Palmitate-Luciferin, has been synthesized for studying ion complexation at the air-water interface using second harmonic generation (SHG). This molecule was designed through the addition of a long hydrophobic palmitoyl alkyl chain to the aromatic π-electron system of Luciferin. We first demonstrate that this organic chromophore is a potential candidate for SHG studies of ion complexation with the measurement of its first hyper-polarizability in aqueous solutions by hyper Rayleigh scattering (HRS) with and without calcium ions. Then, we characterize the Palmitate-Luciferin surfactant properties at the air-water interface combining surface tension measurements with a surface SHG study and Brewster angle imaging. These results allow us to build a molecular description of the chromophore at the interface and observe its molecular reorganization during the monolayer compression leading to the formation of aggregates. Finally, we show that the initial goal of the designing work is achieved since Palmitate-Luciferin indeed exhibits a higher SHG response in the presence of calcium ions in the aqueous sub-phase as expected. (authors)

  4. Influence of dissolved humic substances on the mass transfer of organic compounds across the air-water interface.

    Science.gov (United States)

    Ramus, Ksenia; Kopinke, Frank-Dieter; Georgi, Anett

    2012-01-01

    The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal. PMID:22051345

  5. Influence of dissolved humic substances on the mass transfer of organic compounds across the air-water interface.

    Science.gov (United States)

    Ramus, Ksenia; Kopinke, Frank-Dieter; Georgi, Anett

    2012-01-01

    The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal.

  6. Water velocity at water-air interface is not zero: Comment on "Three-dimensional quantification of soil hydraulic properties using X-ray computed tomography and image-based modeling" by Saoirse R. Tracy et al.

    Science.gov (United States)

    Zhang, X. X.; Fan, X. Y.; Li, Z. Y.

    2016-07-01

    Tracy et al. (2015, doi: 10.1002/2014WR016020) assumed in their recent paper that water velocity at the water-air interface is zero in their pore-scale simulations of water flow in 3-D soil images acquired using X-ray computed tomography. We comment that such a treatment is physically wrong, and explain that it is the water-velocity gradient in the direction normal to the water-air interface, rather than the water velocity, that should be assumed to be zero at the water-air interface if one needs to decouple the water flow and the air flow. We analyze the potential errors caused by incorrectly taking water velocity at the water-air interface zero based on two simple examples, and conclude that it is not physically sound to make such a presumption because its associated errors are unpredictable.

  7. Towards Organized Hybrid Nanomaterials at the Air/Water Interface Based on Liquid-Crystal/ZnO Nanocrystals.

    Science.gov (United States)

    Paczesny, Jan; Wolska-Pietkiewicz, Małgorzata; Binkiewicz, Ilona; Wróbel, Zbigniew; Wadowska, Monika; Matuła, Kinga; Dzięcielewski, Igor; Pociecha, Damian; Smalc-Koziorowska, Julita; Lewiński, Janusz; Hołyst, Robert

    2015-11-16

    The ability to self-assemble nanosized ligand-stabilized metal oxide or semiconductor materials offers an intriguing route to engineer nanomaterials with new tailored properties from the disparate components. We describe a novel one-pot two-step organometallic approach to prepare ZnO nanocrystals (NCs) coated with deprotonated 4-(dodecyloxy)benzoic acid (i.e., an X-type liquid-crystalline ligand) as a model LC system (termed ZnO-LC1 NCs). Langmuir and Langmuir-Blodgett films of the resulting hybrids are investigated. The observed behavior of the ZnO NCs at the air/water interface is rationalized by invoking a ZnO-interdigitation process mediated by the anchored liquid-crystalline shell. The ordered superstructures form according to mechanism based on a ZnO-interdigitation process mediated by liquid crystals (termed ZIP-LC). The external and directed force applied upon compression at the air/water interface and the packing of the ligands that stabilize the ZnO cores drives the formation of nanorods of ordered internal structure. To study the process in detail, we follow a nontraditional protocol of thin-film investigation. We collect the films from the air/water interface in powder form (ZnO-LC1 LB), resuspend the powder in organic solvents and utilize otherwise unavailable experimental techniques. The structural and physical properties of the resulting superlattices were studied by using electron microscopy, atomic force microscopy, X-ray studies, dynamic light scattering, thermogravimetric analysis, UV/Vis absorption, and photoluminescence spectroscopy. PMID:26427916

  8. PREPARATION OF PERFLUOROOCTANOYL-MODIFIEDPOLY(VINYL-ALCOHOL)S AND THEIR ADSORPTION AT AN AIR-WATER INTERFACE

    Institute of Scientific and Technical Information of China (English)

    Pu-xin Zhu; Xiang-dong Luo; Rui-xia Li; Dac-heng Wu

    2002-01-01

    Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750. The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water. It was shown by experimental measurement at 30.0±0.1 C that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration, e.g. about 0.1 g/mL. Obviously,macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants.The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.

  9. Exchange of polycyclic aromatic hydrocarbons across the air-water interface in the Bohai and Yellow Seas

    Science.gov (United States)

    Chen, Yingjun; Lin, Tian; Tang, Jianhui; Xie, Zhiyong; Tian, Chongguo; Li, Jun; Zhang, Gan

    2016-09-01

    In this study, air and surface seawater samples collected from the Bohai (BS) and Yellow Seas (YS) in May 2012 were determined exchange of PAHs, especially of low-molecular-weight (LMW) PAHs (three- and four-ring PAHs) at the air-water interface. Net volatilization fluxes of LMW PAHs were 266-1454 ng/m2/d and decreased with distance from the coast, indicating that these PAHs transported from coastal runoff were potential contributors to the atmosphere in the BS and YS. Moreover, LMW PAHs were enriched in the dissolved phase compared with those in the particulate phase in the water column, possibly suggesting that the volatilized LMW PAHs were directly derived from wastewater discharge or petroleum pollution rather than released from contaminated sediments. The air-sea exchange fluxes of the three-ring PAHs were 2- to 20-fold higher than their atmospheric deposition fluxes in the BS and YS. The input to and output from the water reached equilibrium for four-ring PAHs. Differently, five- and six-ring PAHs were introduced into the marine environment primarily through dry and wet deposition, indicating that the water column was still a sink of these PAHs from the surrounding atmosphere.

  10. Exchange of polycyclic aromatic hydrocarbons across the air-water interface in the Bohai and Yellow Seas

    Science.gov (United States)

    Chen, Yingjun; Lin, Tian; Tang, Jianhui; Xie, Zhiyong; Tian, Chongguo; Li, Jun; Zhang, Gan

    2016-09-01

    In this study, air and surface seawater samples collected from the Bohai (BS) and Yellow Seas (YS) in May 2012 were determined exchange of PAHs, especially of low-molecular-weight (LMW) PAHs (three- and four-ring PAHs) at the air-water interface. Net volatilization fluxes of LMW PAHs were 266-1454 ng/m2/d and decreased with distance from the coast, indicating that these PAHs transported from coastal runoff were potential contributors to the atmosphere in the BS and YS. Moreover, LMW PAHs were enriched in the dissolved phase compared with those in the particulate phase in the water column, possibly suggesting that the volatilized LMW PAHs were directly derived from wastewater discharge or petroleum pollution rather than released from contaminated sediments. The air-sea exchange fluxes of the three-ring PAHs were 2- to 20-fold higher than their atmospheric deposition fluxes in the BS and YS. The input to and output from the water reached equilibrium for four-ring PAHs. Differently, five- and six-ring PAHs were introduced into the marine environment primarily through dry and wet deposition, indicating that the water column was still a sink of these PAHs from the surrounding atmosphere.

  11. Tensiometry and dilational rheology of mixed β-lactoglobulin/ionic surfactant adsorption layers at water/air and water/hexane interfaces.

    Science.gov (United States)

    Dan, Abhijit; Gochev, Georgi; Miller, Reinhard

    2015-07-01

    Oscillating drop tensiometry was applied to study adsorbed interfacial layers at water/air and water/hexane interfaces formed from mixed solutions of β-lactoglobulin (BLG, 1 μM in 10 mM buffer, pH 7 - negative net charge) and the anionic surfactant SDS or the cationic DoTAB. The interfacial pressure Π and the dilational viscoelasticity modulus |E| of the mixed layers were measured for mixtures of varying surfactant concentrations. The double capillary technique was employed which enables exchange of the protein solution in the drop bulk by surfactant solution (sequential adsorption) or by pure buffer (washing out). The first protocol allows probing the influence of the surfactant on a pre-adsorbed protein layer thus studying the protein/surfactant interactions at the interface. The second protocol gives access to the residual values of Π and |E| measured after the washing out procedure thus bringing information about the process of protein desorption. The DoTAB/BLG complexes exhibit higher surface activity and higher resistance to desorption in comparison with those for the SDS/BLG complexes due to hydrophobization via electrostatic binding of surfactant molecules. The neutral DoTAB/BLG complexes achieve maximum elastic response of the mixed layer. Mixed BLG/surfactant layers at the water/oil interface are found to reach higher surface pressure and lower maximum dilational elasticity than those at the water/air surface. The sequential adsorption mode experiments and the desorption study reveal that binding of DoTAB to pre-adsorbed BLG globules is somehow restricted at the water/air surface in comparison with the case of complex formation in the solution bulk and subsequently adsorbed at the water/air surface. Maximum elasticity is achieved with washed out layers obtained after simultaneous adsorption, i.e. isolation of the most surface active DoTAB/BLG complex. These specific effects are much less pronounced at the W/H interface.

  12. Water at Interfaces

    DEFF Research Database (Denmark)

    Björneholm, Olle; Hansen, Martin Hangaard; Hodgson, Andrew;

    2016-01-01

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives...

  13. [Diurnal changes in greenhouse gases at water-air interface of Xiangxi River in autumn and their influencing factors].

    Science.gov (United States)

    Huang, Wen-Min; Zhu, Kong-Xian; Zhao, Wei; Yu, Bo-Shi; Yuan, Xi-Gong; Feng, Rui-Jie; Bi, Yong-Hong; Hu, Zheng-Yu

    2013-04-01

    With the closed chamber and gas chromatography method, a 24-hour continuous monitoring was carried out to understand the greenhouse gases fluxes across the water-air interface of the Xiangxi River Bay, the Three-Gorges Reservoir in Autumn. Results indicated that the fluxes of CO2, CH4 and N2O across the water-air interface showed an obvious diurnal variation. The absorption and emission process of CH4 showed strong diurnal variation during the experimental period, reaching the highest emission at 1 am, whereas CO2 and N2O were emitted all day. The fluxes of CO2 ranged from 20.1-97.5 mg x (m2 x h)(-1) at day and 32.7-42.5 mg x (m2 x h)(-1) at night, the fluxes of N2O ranged from 18.4-133.7 microg x (m2 x h)(-1) at day and 42.1-102.6 microg x (m2 x h)(-1) at night. The fluxes of CO2 had positive correlation with wind speed and negative correlation with pH. The fluxes of N2O had positive correlation with pH.

  14. Photochemical formation of silver and gold nanostructures at the air-water interface and their electrocatalytic properties

    International Nuclear Information System (INIS)

    In this paper, we report a simple method of fabricating silver and gold nanostructures at the air-water interface, which can be spontaneously assembled through the reduction of AgNO3 and HAuCl4 with ultraviolet (UV) irradiation in the presence of polyacrylic acid (PAA), respectively. It was found that the building blocks in the silver nanostructure are mainly interwoven silver nanofilaments, while those of the gold nanostructure are mainly different sizes of gold nanoparticles and some truncated gold nanoplates, and even coalescence into networks. At the air-water interface, these silver and gold nanostructures can be easily transferred onto the surface of indium tin oxide (ITO) slides and used for electrochemical measurements. After a replacement reaction with H2PdCl4, the silver nanostructure is transformed into a Ag-Pd bimetallic nanostructure, with good electrocatalytic activity for O2 reduction. The gold nanostructure can also show high electrocatalytic activity to the oxidation of nitric oxide (NO) with a detection limit of about 10 μM NaNO2 at S/N = 3

  15. [Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi, China].

    Science.gov (United States)

    Li, Jian-hong; Pu, Jun-bing; Sun, Ping-an; Yuan, Dao-xian; Liu, Wen; Zhang, Tao; Mo, Xue

    2015-11-01

    Due to special hydrogeochemical characteristics of calcium-rich, alkaline and DIC-rich ( dissolved inorganic carbon) environment controlled by the weathering products from carbonate rock, the exchange characteristics, processes and controlling factors of greenhouse gas (CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs (Dalongdong reservoir-karst reservoir, Wulixia reservoir--semi karst reservoir, Si'anjiang reservoir-non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region, China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches, floating chamber (FC) and thin boundary layer models (TBL), were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: (1) surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4, while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. (2) CO2 and CH4 effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly, more attention should be paid to the CO2 and CH4 emission from discharging water under dam. (3) In the absence of submerged soil organic matters and plants, the difference of CH4 effluxes between karst groundwater-fed reservoir ( Dalongdong water reservoir) and non-karst area ( Wulixia water reservoir and Si'anjiang water reservoir) was less. However, CO2

  16. Water at Interfaces.

    Science.gov (United States)

    Björneholm, Olle; Hansen, Martin H; Hodgson, Andrew; Liu, Li-Min; Limmer, David T; Michaelides, Angelos; Pedevilla, Philipp; Rossmeisl, Jan; Shen, Huaze; Tocci, Gabriele; Tyrode, Eric; Walz, Marie-Madeleine; Werner, Josephina; Bluhm, Hendrik

    2016-07-13

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives many electrochemical reactions, and the liquid/vapor interface, which governs the uptake and release of trace gases by the oceans and cloud droplets. In this article we review some of the recent experimental and theoretical advances in our knowledge of the properties of aqueous interfaces and discuss open questions and gaps in our understanding. PMID:27232062

  17. Mechanical properties of protein adsorption layers at the air/water and oil/water interface: a comparison in light of the thermodynamical stability of proteins.

    Science.gov (United States)

    Mitropoulos, Varvara; Mütze, Annekathrin; Fischer, Peter

    2014-04-01

    Over the last decades numerous studies on the interfacial rheological response of protein adsorption layers have been published. The comparison of these studies and the retrieval of a common parameter to compare protein interfacial activity are hampered by the fact that different boundary conditions (e.g. physico-chemical, instrumental, interfacial) were used. In the present work we review previous studies and attempt a unifying approach for the comparison between bulk protein properties and their adsorption films. Among many common food grade proteins we chose bovine serum albumin, β-lactoglobulin and lysozyme for their difference in thermodynamic stability and studied their adsorption at the air/water and limonene/water interface. In order to achieve this we have i) systematically analyzed protein adsorption kinetics in terms of surface pressure rise using a drop profile analysis tensiometer and ii) we addressed the interfacial layer properties under shear stress using an interfacial shear rheometer under the same experimental conditions. We could show that thermodynamically less stable proteins adsorb generally faster and yield films with higher shear rheological properties at air/water interface. The same proteins showed an analog behavior when adsorbing at the limonene/water interface but at slower rates. PMID:24332621

  18. Effect of the spacer group on the behavior of the cationic Gemini surfactant monolayer at the air/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Chen Qibin; Zhang Dazhi; Li Rong [State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237 (China); Liu Honglai [State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237 (China)], E-mail: hlliu@ecust.edu.cn; Hu Ying [State Key Laboratory of Chemical Engineering and Department of Chemistry, East China University of Science and Technology, Shanghai 200237 (China)

    2008-10-01

    Surface properties of the insoluble cationic bis-(quaternary ammonium halide) surfactants (Gemini) with polymethylene spacer at the air/water interface were investigated. The monolayers were transferred onto mica by the Langmuir-Blodgett (LB) technique and the corresponding LB films were characterized by the atomic force microscopy (AFM) and the contact angle of water. For the Gemini surfactants with the different spacer length, it was found that the surface pressure-molecular area isotherms resemble to each other. The limiting area increases rapidly and almost linearly with the increase of spacer length for the short spacers, but reaches a maximum at s = 10 and decreases slightly at s > 10. The AFM images show that the surface micelles and the multilayer aggregates gradually appear with the increase of surface pressure. No matter what the surface pressures are, the main structure of the monolayer almost keeps the same, which suggested that the major molecules lie nearly flat on the water surface, while the increase of surface pressure forces the minor alkyl chains to turn only partly or completely vertical to the water surface and even to overturn. This is the cause that the contact angle of water on LB film increases slightly with the surface pressure.

  19. Structure and conformation of peptides at air/aqueous interface and their impact on interfacial water structure

    Science.gov (United States)

    Chandra Jena, Kailash; Tomar, Deepak

    Process of protein folding is very essential for the proper functioning of the protein molecules at membrane surface and other organelles. Understanding the process of protein folding at various biological relevant aqueous interfaces are very important to understand various complicated chemical and physical processes relevant to chemistry, physics, and medicine. The building blocks of proteins molecules are amino acids and the chemistry of each amino acid is very different; as a consequence their sequence plays an important role for various conformations upon adsorption for the protein molecules. In the present study, we have investigated the interfacial structure and conformation of two amino acids (L-Proline and L-Tyrosine) and peptide molecules formed from these two amino acids (L-Tyr-Pro). We have used sum frequency generation (SFG) vibrational spectroscopy to probe the air/aqueous interface. We have studied the impact of adsorption of the amino acids and the peptide molecules on the interfacial water structure by slowly varying concentration and ionic strength of the solutions. Our preliminary result shows a huge impact of the adsorption process of peptide molecules on the hydrogen bonding environment of interfacial structure of water. Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab-140001.

  20. Supramolecular 1-D polymerization of DNA origami through a dynamic process at the 2-dimensionally confined air-water interface.

    Science.gov (United States)

    Yonamine, Yusuke; Cervantes-Salguero, Keitel; Minami, Kosuke; Kawamata, Ibuki; Nakanishi, Waka; Hill, Jonathan P; Murata, Satoshi; Ariga, Katsuhiko

    2016-05-14

    In this study, a Langmuir-Blodgett (LB) system has been utilized for the regulation of polymerization of a DNA origami structure at the air-water interface as a two-dimensionally confined medium, which enables dynamic condensation of DNA origami units through variation of the film area at the macroscopic level (ca. 10-100 cm(2)). DNA origami sheets were conjugated with a cationic lipid (dioctadecyldimethylammonium bromide, 2C18N(+)) by electrostatic interaction and the corresponding LB-film was prepared. By applying dynamic pressure variation through compression-expansion processes, the lipid-modified DNA origami sheets underwent anisotropic polymerization forming a one-dimensionally assembled belt-shaped structure of a high aspect ratio although the thickness of the polymerized DNA origami was maintained at the unimolecular level. This approach opens up a new field of mechanical induction of the self-assembly of DNA origami structures. PMID:27091668

  1. The Equilibria of Diosgenin-Phosphatidylcholine and Diosgenin-Cholesterol in Monolayers at the Air/Water Interface.

    Science.gov (United States)

    Janicka, Katarzyna; Jastrzebska, Izabella; Petelska, Aneta Dorota

    2016-08-01

    Diosgenin (Dio) has shown many treatment properties, but the most important property is cytotoxic activity in cancer cells. In this study, we investigated monolayers of Dio, cholesterol (Ch), and phosphatidylcholine (PC) at the air/water interface. The measurements were carried with a Langmuir Teflon trough and a Nima 9000 tensiometer program. The surface tension values of pure and mixed monolayers were used to calculate π-A isotherms and determine molecular surface areas. We were able to demonstrate the formation of complexes between Dio and PC and Dio and Ch molecules also. We considered the equilibrium between individual components and the formed complexes. In addition, we established that diosgenin and the lipids formed highly stable 1:1 complexes. PMID:27350149

  2. Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface.

    Science.gov (United States)

    Dai, Wenyang; Shao, Feng; Szczerbiński, Jacek; McCaffrey, Ryan; Zenobi, Renato; Jin, Yinghua; Schlüter, A Dieter; Zhang, Wei

    2016-01-01

    A two-dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine-linked chemical structure of the obtained monolayer was characterized by tip-enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure-property relationships.

  3. Monolayer behaviour of chiral compounds at the air-water interface: 4-hexadecyloxy-butane-1,2-diol

    DEFF Research Database (Denmark)

    Rietz, R.; Rettig, W.; Brezesinski, G.;

    1996-01-01

    Monolayers of the pure S-enantiomer (x(S) = 1) and of two mixtures x(S) = 0.75 and x(S) = 0.5 (racemate) of 4-hexadecyloxy-butane-1,2-diol (C16H33-O-CH2-CH2-CHOH-CH2OH) (HOBD) have been studied at the air-water interface by thermodynamic measurements, fluorescence microscopy and X-ray diffraction...... clockwise and counterclockwise. The number of the left- and right-handed arms depends on the mixing ratio. At lower lateral pressures S-HOBD and the mixture with x(S) = 0.75 exhibit a chiral structure. At pressures above 25 mN m(-1) a centered rectangular structure with a tilt of the molecules towards...

  4. Structural and topographical characteristics of adsorbed WPI and monoglyceride mixed monolayers at the air-water interface.

    Science.gov (United States)

    Patino, Juan M Rodríguez; Fernández, Marta Cejudo

    2004-05-25

    In this work we have analyzed the structural and topographical characteristics of mixed monolayers formed by an adsorbed whey protein isolate (WPI) and a spread monoglyceride monolayer (monopalmitin or monoolein) on the previously adsorbed protein film. Measurements of the surface pressure (pi)-area (A) isotherm were obtained at 20 degrees C and at pH 7 for protein-adsorbed films from water in a Wilhelmy-type film balance. Since the surface concentration (1/A) is actually unknown for the adsorbed monolayer, the values were derived by assuming that the A values for adsorbed and spread monolayers were equal at the collapse point of the mixed film. The pi-A isotherm deduced for adsorbed WPI monolayer in this work is practically the same as that obtained directly by spreading. For WPI-monoglyceride mixed films, the pi-A isotherms for adsorbed and spread monolayers at pi higher than the equilibrium surface pressure of WPI are practically coincident, a phenomenon which may be attributed to the protein displacement by the monoglyceride from the interface. At lower surface pressures, WPI and monoglyceride coexist at the interface and the adsorbed and spread pi-A isotherms (i.e., the monolayer structure of the mixed films) are different. Monopalmitin has a higher capacity than monoolein for the displacement of protein from the air-water interface. However, some degree of interactions exists between proteins and monoglycerides and these interactions are higher for adsorbed than for spread films. The topography of the monolayer corroborates these conclusions.

  5. Tuning the Structure and Rheology of Polystyrene Particles at the Air-Water Interface by Varying the pH.

    Science.gov (United States)

    Truzzolillo, Domenico; Sharaf, Hossameldeen; Jonas, Ulrich; Loppinet, Benoit; Vlassopoulos, Dimitris

    2016-07-12

    We form films of carboxylated polystyrene particles (C-PS) at the air-water interface and investigate the effect of subphase pH on their structure and rheology by using a suite of complementary experimental techniques. Our results suggest that electrostatic interactions drive the stability and the structural order of the films. In particular, we show that by increasing the pH of the subphase from 9 up to 13, the films exhibit a gradual transition from solid to liquidlike, which is accompanied by a loss of the long-range order (that characterizes them at lower values of pH). Direct optical visualization of the layers, scanning electron microscopy, and surface pressure isotherms indicate that the particles deposited at the interface form three-dimensional structures involving clusters, with the latter being suppressed and a quasi-2D particle configuration eventually reached at the highest pH values. Evidently, the properties of colloidal films can be tailored significantly by altering the pH of the subphase.

  6. Impact of biogenic amine molecular weight and structure on surfactant adsorption at the air-water interface.

    Science.gov (United States)

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun

    2016-02-01

    The oligoamines, such as ethylenediamine to pentaethylenetetramine, and the aliphatic biogenic amines, such as putrescine, spermidine and spermine, strongly interact with anionic surfactants, such as sodium dodecylsulfate, SDS. It has been shown that this results in pronounced surfactant adsorption at the air-water interface and the transition from monolayer to multilayer adsorption which depends upon solution pH and oligoamine structure. In the neutron reflectivity, NR, and surface tension, ST, results presented here the role of the oligoamine structure on the adsorption of SDS is investigated more fully using a range of different biogenic amines. The effect of the extent of the intra-molecular spacing between amine groups on the adsorption has been extended by comparing results for cadavarine with putrescine and ethylenediamine. The impact of more complex biogenic amine structures on the adsorption has been investigated with the aromatic phenethylamine, and the heterocyclic amines histamine and melamine. The results provide an important insight into how surfactant adsorption at interfaces can be manipulated by the addition of biogenic amines, and into the role of solution pH and oligoamine structure in modifying the interaction between the surfactant and oligoamine. The results impact greatly upon potential applications and in understanding some of the important biological functions of biogenic amines. PMID:26524255

  7. Impact of biogenic amine molecular weight and structure on surfactant adsorption at the air-water interface.

    Science.gov (United States)

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun

    2016-02-01

    The oligoamines, such as ethylenediamine to pentaethylenetetramine, and the aliphatic biogenic amines, such as putrescine, spermidine and spermine, strongly interact with anionic surfactants, such as sodium dodecylsulfate, SDS. It has been shown that this results in pronounced surfactant adsorption at the air-water interface and the transition from monolayer to multilayer adsorption which depends upon solution pH and oligoamine structure. In the neutron reflectivity, NR, and surface tension, ST, results presented here the role of the oligoamine structure on the adsorption of SDS is investigated more fully using a range of different biogenic amines. The effect of the extent of the intra-molecular spacing between amine groups on the adsorption has been extended by comparing results for cadavarine with putrescine and ethylenediamine. The impact of more complex biogenic amine structures on the adsorption has been investigated with the aromatic phenethylamine, and the heterocyclic amines histamine and melamine. The results provide an important insight into how surfactant adsorption at interfaces can be manipulated by the addition of biogenic amines, and into the role of solution pH and oligoamine structure in modifying the interaction between the surfactant and oligoamine. The results impact greatly upon potential applications and in understanding some of the important biological functions of biogenic amines.

  8. Urban water interfaces

    Science.gov (United States)

    Gessner, M. O.; Hinkelmann, R.; Nützmann, G.; Jekel, M.; Singer, G.; Lewandowski, J.; Nehls, T.; Barjenbruch, M.

    2014-06-01

    Urban water systems consist of large-scale technical systems and both natural and man-made water bodies. The technical systems are essential components of urban infrastructure for water collection, treatment, storage and distribution, as well as for wastewater and runoff collection and subsequent treatment. Urban aquatic ecosystems are typically subject to strong human influences, which impair the quality of surface and ground waters, often with far-reaching impacts on downstream aquatic ecosystems and water users. The various surface and subsurface water bodies in urban environments can be viewed as interconnected compartments that are also extensively intertwined with a range of technical compartments of the urban water system. As a result, urban water systems are characterized by fluxes of water, solutes, gases and energy between contrasting compartments of a technical, natural or hybrid nature. Referred to as urban water interfaces, boundaries between and within these compartments are often specific to urban water systems. Urban water interfaces are generally characterized by steep physical and biogeochemical gradients, which promote high reaction rates. We hypothesize that they act as key sites of processes and fluxes with notable effects on overall system behaviour. By their very nature, urban water interfaces are heterogeneous and dynamic. Therefore, they increase spatial heterogeneity in urban areas and are also expected to contribute notably to the temporal dynamics of urban water systems, which often involve non-linear interactions and feedback mechanisms. Processes at and fluxes across urban water interfaces are complex and less well understood than within well-defined, homogeneous compartments, requiring both empirical investigations and new modelling approaches at both the process and system level. We advocate an integrative conceptual framework of the urban water system that considers interfaces as a key component to improve our fundamental

  9. Adsorption of egg phosphatidylcholine to an air/water and triolein/water bubble interface: use of the 2-dimensional phase rule to estimate the surface composition of a phospholipid/triolein/water surface as a function of surface pressure.

    Science.gov (United States)

    Mitsche, Matthew A; Wang, Libo; Small, Donald M

    2010-03-11

    Phospholipid monolayers play a critical role in the structure and stabilization of biological interfaces, including all membranes, the alveoli of the lungs, fat droplets in adipose tissue, and lipoproteins. The behavior of phospholipids in bilayers and at an air-water interface is well understood. However, the study of phospholipids at oil-water interfaces is limited due to technical challenges. In this study, egg phosphatidylcholine (EPC) was deposited from small unilamellar vesicles onto a bubble of either air or triolein (TO) formed in a low-salt buffer. The surface tension (gamma) was measured using a drop tensiometer. We observed that EPC binds irreversibly to both interfaces and at equilibrium exerts approximately 12 and 15 mN/m of pressure (Pi) at an air and TO interface, respectively. After EPC was bound to the interface, the unbound EPC was washed out of the cuvette, and the surface was compressed to study the Pi/area relationship. To determine the surface concentration (Gamma), which cannot be measured directly, compression isotherms from a Langmuir trough and drop tensiometer were compared. The air-water interfaces had identical characteristics using both techniques; thus, Gamma on the bubble can be determined by overlaying the two isotherms. Both TO and EPC are surface-active, so in a mixed TO/EPC monolayer, both molecules will be exposed to water. Since TO is less surface-active than EPC, as Pi increases, the TO is progressively ejected. To understand the Pi/area isotherm of EPC on a TO bubble, a variety of TO-EPC mixtures were spread at the air-water interface. The isotherms show an abrupt break in the curve caused by the ejection of TO from the monolayer into a new bulk phase. By overlaying the compression isotherm above the ejection point with a TO bubble compression isotherm, Gamma can be estimated. This allows determination of Gamma of EPC on a TO bubble as a function of Pi. PMID:20151713

  10. PREFACE: Water at interfaces Water at interfaces

    Science.gov (United States)

    Gallo, P.; Rovere, M.

    2010-07-01

    This special issue is devoted to illustrating important aspects and significant results in the field of modeling and simulation of water at interfaces with solutes or with confining substrates, focusing on a range of temperatures from ambient to supercooled. Understanding the behavior of water, in contact with different substrates and/or in solutions, is of pivotal importance for a wide range of applications in physics, chemistry and biochemistry. Simulations of confined and/or interfacial water are also relevant for testing how different its behavior is with respect to bulk water. Simulations and modeling in this field are of particular importance when studying supercooled regions where water shows anomalous properties. These considerations motivated the organization of a workshop at CECAM in the summer of 2009 which aimed to bring together scientists working with computer simulations on the properties of water in various environments with different methodologies. In this special issue, we collected a variety of interesting contributions from some of the speakers of the workshop. We have roughly classified the contributions into four groups. The papers of the first group address the properties of interfacial and confined water upon supercooling in an effort to understand the relation with anomalous behavior of supercooled bulk water. The second group deals with the specific problem of solvation. The next group deals with water in different environments by considering problems of great importance in technological and biological applications. Finally, the last group deals with quantum mechanical calculations related to the role of water in chemical processes. The first group of papers is introduced by the general paper of Stanley et al. The authors discuss recent progress in understanding the anomalies of water in bulk, nanoconfined, and biological environments. They present evidence that liquid water may display 'polymorphism', a property that can be present in

  11. Toward a simple molecular understanding of sum frequency generation at air-water interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Noah-Vanhoucke, Joyce; Smith, Jared D.; Geissler, Phillip L.

    2009-01-13

    Second-order vibrational spectroscopies successfully isolate signals from interfaces, but they report on intermolecular structure in a complicated and indirect way. Here we adapt a perspective on vibrational response developed for bulk spectroscopies to explore the microscopic fluctuations to which sum frequency generation (SFG), a popular surface-specific measurement, is most sensitive. We focus exclusively on inhomogeneous broadening of spectral susceptibilities for OH stretching of HOD as a dilute solute in D{sub 2}O. Exploiting a simple connection between vibrational frequency shifts and an electric field variable, we identify several functions of molecular orientation whose averages govern SFG. The frequency-dependence of these quantities is well captured by a pair of averages, involving alignment of OH and OD bonds with the surface normal at corresponding values of the electric field. The approximate form we obtain for SFG susceptibility highlights a dramatic sensitivity to the way a simulated liquid slab is partitioned for calculating second-order response.

  12. Theoretical model for diffusive greenhouse gas fluxes estimation across water-air interfaces measured with the static floating chamber method

    Science.gov (United States)

    Xiao, Shangbin; Wang, Chenghao; Wilkinson, Richard Jeremy; Liu, Defu; Zhang, Cheng; Xu, Wennian; Yang, Zhengjian; Wang, Yuchun; Lei, Dan

    2016-07-01

    Aquatic systems are sources of greenhouse gases on different scales, however the uncertainty of gas fluxes estimated using popular methods are not well defined. Here we show that greenhouse gas fluxes across the air-water interface of seas and inland waters are significantly underestimated by the currently used static floating chamber (SFC) method. We found that the SFC CH4 flux calculated with the popular linear regression (LR) on changes of gas concentration over time only accounts for 54.75% and 35.77% of the corresponding real gas flux when the monitoring periods are 30 and 60 min respectively based on the theoretical model and experimental measurements. Our results do manifest that nonlinear regression models can improve gas flux estimations, while the exponential regression (ER) model can give the best estimations which are close to true values when compared to LR. However, the quadratic regression model is proved to be inappropriate for long time measurements and those aquatic systems with high gas emission rate. The greenhouse gases effluxes emitted from aquatic systems may be much more than those reported previously, and models on future scenarios of global climate changes should be adjusted accordingly.

  13. Oxidation of monolayers of partly converted dimethoxy-substituted poly(p-phenylenevinylene) precursor polymers at the air-water interface

    NARCIS (Netherlands)

    Hagting, J.G.; Schouten, A.J.; Hagting, A

    2000-01-01

    We observed that the poly(p-phenylenevinylene) units in Langmuir monolayers of partly converted dimethoxy-substituted poly(p-phenylenevinylene) precursor polymers oxidize at the air-water interface. This reaction even happened in the dark and therefore can not be attributed to a photooxygenation rea

  14. Modulation of the adsorption properties at air-water interfaces of complexes of egg white ovalbumin with pectin by the dielectric constant

    NARCIS (Netherlands)

    Kudryashova, E.V.; Jongh, H.H.J.de

    2008-01-01

    The possibility of modulating the mesoscopic properties of food colloidal systems by the dielectric constant is studied by determining the impact of small amounts of ethanol (10%) on the adsorption of egg white ovalbumin onto the air-water interface in the absence and presence of pectin. The adsorpt

  15. The adsorption and unfolding kinetics determines the folding state of proteins at the air-water interface and thereby the equation of state

    NARCIS (Netherlands)

    Wierenga, P.A.; Egmond, M.R.; Voragen, A.G.J.; Jongh, H.H.J.de

    2006-01-01

    Unfolding of proteins has often been mentioned as an important factor during the adsorption process at air-water interfaces and in the increase of surface pressure at later stages of the adsorption process. This work focuses on the question whether the folding state of the adsorbed protein depends o

  16. Water, CO2 and Energy Exchange at Vegetation-air Interface

    Institute of Scientific and Technical Information of China (English)

    Li XIAO

    2012-01-01

    [Objective] The aim was to analyze water and heat fluxes, CO2 fluxes and energy balance in wheat ecosystem in Luancheng County of Hebei Province. [Method] Based on data of water and heat flux, and CO2 fluxes, routine meteorological and biomass data in Luancheng in 2008, water and heat fluxes, CO2 fluxes and energy balance in wheat ecosystem were explored. [Result] The results showed that latent and sensible heat and CO2 fluxes were of obvious daily and seasonal changes; latent and sensible heat fluxes shaped an inverted U in daily change, and CO2 fluxes were of a U-shape; daily flux peak differed significantly. Furthermore, the change of latent heat, sensible heat and CO2 fluxes were closely related to environ- mental factors. Detailedly, the three were sensitive to light intensity and net radiation, and correlation coefficients were 0.92, 0.66, 0.65 and 0.90, 0.69, 0.74, respectively. Besides, the fluxes, sensitive to temperature, proved better in sunny day, especially for latent flux which is more sensitive to water in soils after precipitation. In addition, closure degree of energy balance in wheat fields was 0.91 and non-closure, caused by measurement error and neglection of heat storage, was observed, too. What's more. closure degree differed in months and time periods within a day. [Conclusion] The research concluded water and heat fluxes, CO2 fluxes, transport mechanisms and concerning factors, providing scientific reference for revealing mechanism of evapo- ration and heat dissipation of canopy, relationship between photosynthesis and water use efficiencyand energy distribution mechanism.

  17. Crystalline mono- and multilayer self-assemblies of oligothiophenes at the air-water interface

    DEFF Research Database (Denmark)

    Isz, S.; Weissbuch, I.; Kjær, K.;

    1997-01-01

    pressure-area isotherms, by scanning force microscopy (SFM) after transfer of the films onto atomically smooth mica, by cryo-transmission electron microscopy (Cryo-TEM) on vitreous ice, and by grazing incidence synchrotron X-ray diffraction (GID) directly on the water surface. S-4 forms two polymorphic...

  18. Energy and Water Balance at Soil-Air Interface in a Sahelian Region

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The aim of this work is an improvement of the parameterization of the soil moisture in the scheme of the Land Surface Process Model (LSPM) for applications over desert areas. In fact, in very dry conditions, the water vapour flux plays an important role in the evaporation processes and influences the underground profiles of humidity and temperature. The improved version of soil moisture parametcrization in the LSPM scheme has been checked by using the data taken from the database of the field experiment HAPEX-Sahel (Hydrology-Atmosphere Pilot Experiment in the Sahel, 1990-1992). Model simulations refer to three dif ferent stations located in Niger (Fallow, Millet and Tiger sites) where input data for LSPM and observations were simultaneously available. The results of simulations taking into account the water vapour flux in the soil model LSPM, seem to compare better with the observed behaviour of soil moisture and turbulent heat fluxes than those overlooking the water vapour flux, confirming the great importance of the water vapour in such dry conditions.

  19. Computational study of shock waves propagating through air-plastic-water interfaces

    CERN Document Server

    Del Razo, Mauricio J

    2015-01-01

    The following study is motivated by experimental studies in traumatic brain injury (TBI). Recent research has demonstrated that low intensity non-impact blast wave exposure frequently leads to mild traumatic brain injury (mTBI); however, the mechanisms connecting the blast waves and the mTBI remain unclear. Collaborators at the Seattle VA Hospital are doing experiments to understand how blast waves can produce mTBI. In order to gain insight that is hard to obtain by experimental means, we have developed conservative finite volume methods for interface-shock wave interaction to simulate these experiments. A 1D model of their experimental setup has been implemented using Euler equations for compressible fluids. These equations are coupled with a Tammann equation of state (EOS) that allows us to model compressible gas along with almost incompressible fluids or elastic solids. A hybrid HLLC-exact Eulerian-Lagrangian Riemann solver for Tammann EOS with a jump in the parameters has been developed. The model has sho...

  20. Intraday evaporation and heat fluxes variation at air-water interface of extremely shallow lakes in Chilean Andean Plateau

    Science.gov (United States)

    Vergara, Jaime; de la Fuente, Alberto

    2016-04-01

    Salars are landscapes formed by evapo-concentration of salts that usually have extremely shallow terminal lagoons (de la Fuente & Niño, 2010). They are located in the altiplanic region of the Andes Mountains of Chile, Argentina, Bolivia and Peru, and they sustain highly vulnerable and isolated ecosystems in the Andean Desert. These ecosystems are sustained by benthic primary production, which is directly linked to mass, heat and momentum transfer between the water column and the atmosphere (de la Fuente, 2014). Despite the importance of these transport processes across the air-water interface, there are few studies describing their intraday variation and how they are influenced by the stability of the atmospheric boundary layer in the altiplano. The main objective of this work is to analyze the intraday vertical transport variation of water vapor, temperature and momentum between the atmosphere and a shallow water body on Salar del Huasco located in northern Chile (20°19'40"S, 68°51'25"W). To achieve this goal, we measured atmospheric and water variables in a campaign realized on late October 2015, using high frequency meteorological instruments (a sonic anemometer with an incorporated infrared gas analyzer, and a standard meteorological station) and water sensors. From these data, we characterize the intraday variation of water vapor, temperature and momentum fluxes, we quantify the influence of the atmospheric boundary layer stability on them, and we estimate transfer coefficients associated to latent heat, sensible heat, hydrodynamic drag and vertical transport of water vapor. As first results, we found that latent and sensible heat fluxes are highly influenced by wind speed rather buoyancy, and we can identify four intraday intervals with different thermo-hydrodynamic features: (1) cooling under stable condition with wind speed near 0 from midnight until sunrise; (2) free convection with nearly no wind speed under unstable condition from sunrise until midday

  1. Kinetics of marine surfactant adsorption at an air water interface. Baltic Sea studies

    Directory of Open Access Journals (Sweden)

    Stanis³aw J. Pogorzelski

    2001-12-01

    Full Text Available The paper contains the results of studies of natural surface film adsorption kinetics carried out in inland waters and in shallow offshore regions of the Baltic Sea during 2000-01 under calm sea conditions. The novel approach presented here for the adsorption dynamics is based on the mixed kinetic-diffusion model and analyses of the surface pressure-time plots at short (t ->0 and long( t -> ∞ adsorption time intervals. Values of the effective relative diffusion coefficient Deff / D (= 0.008-0.607 and energy barrier for adsorption Ea / RT (= 0.49-7.10 agree well with the data reported for model non-ionic surfactant solutions of pre-cmc concentrations. Wind speed is one of the factors affecting the adsorption barrier via the increased surface pressure of the natural film exposed to wind shear stress (~ U102, and enters the relation Ea / RT = 1.70 U101/3.

  2. Superposition-additive approach: thermodynamic parameters of clusterization of monosubstituted alkanes at the air/water interface.

    Science.gov (United States)

    Vysotsky, Yu B; Belyaeva, E A; Fomina, E S; Fainerman, V B; Aksenenko, E V; Vollhardt, D; Miller, R

    2011-12-21

    The applicability of the superposition-additive approach for the calculation of the thermodynamic parameters of formation and atomization of conjugate systems, their dipole electric polarisabilities, molecular diamagnetic susceptibilities, π-electron circular currents, as well as for the estimation of the thermodynamic parameters of substituted alkanes, was demonstrated earlier. Now the applicability of the superposition-additive approach for the description of clusterization of fatty alcohols, thioalcohols, amines, carboxylic acids at the air/water interface is studied. Two superposition-additive schemes are used that ensure the maximum superimposition of the graphs of the considered molecular structures including the intermolecular CH-HC interactions within the clusters. The thermodynamic parameters of clusterization are calculated for dimers, trimers and tetramers. The calculations are based on the values of enthalpy, entropy and Gibbs' energy of clusterization calculated earlier using the semiempirical quantum chemical PM3 method. It is shown that the proposed approach is capable of the reproduction with sufficiently enough accuracy of the values calculated previously. PMID:22042000

  3. Polymerization of a diacetylenic phospholipid monolayer at the air-water interface

    Science.gov (United States)

    Bourdieu, L.; Chatenay, D.; Daillant, J.; Luzet, D.

    1994-01-01

    Monolayers of a polymerizable phospholipid on water have been studied both before and after polymerization. Before polymerization, the phase diagram is established by isotherm measurements and optical microscopy (epifluorescence and direct observation between crossed polarizer and analyzer). This allows us to bring into evidence a coexistence region between a condensed and an expanded phase, above a triple point temperature T_t = 20 ^{circ}C. The dramatic influence of impurities on the size of coexistence domains between the condensed phase and the expanded one is clearly demonstrated, even at a very low concentration of impurities. Structural and morphological modifications during the polymerization where investigated using X-ray surface scattering together with atomic force microscopy. Whatever the polymerization conditions (constant area or constant pressure), X-ray reflectivity clearly shows the reorientation of the diacetylenic links. Only constant area polymerization leads to a viscoelastic behavior of the film, as shown by talcum decoration. The topochemical nature of the polymerization of diacetylenic groups induces strong constraints on the monolayers and, when the polymerization is achieved at constant area, leads to the collapse of the films evidenced by both techniques.

  4. Conversion of Iodide to Hypoiodous Acid and Molecular Iodine at the Air-Water Interface

    Science.gov (United States)

    Pillar, E. A.; Guzman, M. I.

    2013-12-01

    Sea spray aerosols continuously transfer a significant amount of halides to the marine boundary layer, where they play a major role in the depletion of tropospheric ozone. The reactivity of iodide is of special interest in sea spray aerosols, where this species is enriched relative to chloride and bromide in surface seawater. This work presents laboratory experiments that provide mechanistic information to understand the reactivity of halides in atmospheric aerosols. Pneumatically assisted electrospray is used to aerosolize solutions of sodium iodide (0.01-100 μM), which are rapidly (~3 μs) oxidized by ozone at 25 °C. Reaction products include HIO, IO2-, IO3-, I2, HI2O-, and I3-, all identified by mass spectrometry. The distribution of products varies along two different reaction pathways, one favoring the production of I2 and HIO for typical tropospheric ozone levels (~50 ppbv), and another one directed to the production of IO3- at higher oxidizer concentrations. The formation of products increases exponentially with rising concentrations of initial sodium iodide, [NaI]0. The process is determined to be pH independent for the pH range 6-8 representative of surface waters. The substitution of aqueous solutions by organic solvents, such as methanol or acetonitrile, causes a decrease in the surface tension and lifetime of the droplets, leading to larger I2 production. The presence of surface active organic compounds, which alter the structure of the interfacial region, promote the pathway of I2 formation over IO3-. In conclusion, this presentation will show how the oxidation of iodide in aqueous microdroplets can release reactive gas-phase species, such as I2 and HIO, capable to affect tropospheric ozone globally. Normalized intensity of products observed during the ozonolysis of iodide solutions at 130 ppbv ozone. Cone voltage = 70 V, needle voltage = 2.5 kV.

  5. Vibrational spectroscopy of water interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Du, Q.

    1994-12-01

    The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful and versatile tools for studying all kinds of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the second order nonlinear susceptibility. The technique of infrared-visible sum frequency generation (SFG) is particularly attractive because it offers a viable way to do vibrational spectroscopy on any surfaces accessible to light with submonolayer sensitivity. In this thesis, the author applies SFG to study a number of important water interfaces. At the air/water interface, hydrophobic solid/water and liquid/water interfaces, it was found that approximately 25% of surface water molecules have one of their hydrogen pointing away from the liquid water. The large number of unsatisfied hydrogen bonds contributes significantly to the large interfacial energy of the hydrophobic surfaces. At the hydrophilic fused quartz/water interface and a fatty acid monolayer covered water surface, the structure and orientation of surface water molecules are controlled by the hydrogen bonding of water molecules with the surface OH groups and the electrostatic interaction with the surface field from the ionization of surface groups. A change of pH value in the bulk water can significantly change the relative importance of the two interactions and cause a drastic change in orientation of the surface water molecules. SFG has also been applied to study the tribological response of some model lubricant films. Monolayers of Langmuir-Blodgett films were found to disorder orientationaly under mildly high pressure and recover promptly upon removal of the applied pressure.

  6. Miscibility of dl-α-tocopherol β-glucoside in DPPC monolayer at air/water and air/solid interfaces.

    Science.gov (United States)

    Neunert, G; Makowiecki, J; Piosik, E; Hertmanowski, R; Polewski, K; Martynski, T

    2016-10-01

    The role of newly synthesized tocopherol glycosidic derivative in modifying molecular organization and phase transitions of phospholipid monolayer at the air/water interface has been investigated. Two-component Langmuir films of dl-α-tocopheryl β-D-glucopyranoside (BG) mixed with dipalmitoyl phosphatidylcholine (DPPC) in the whole range of mole fractions were formed at the water surface. An analysis of surface pressure versus mean molecular area (π-A) isotherms and Brewster angle microscope images showed that the presence of BG molecules changes the structure and packing of the DPPC monolayer in a BG concentration dependent manner. BG molecules incorporated into DPPC monolayer inhibit its liquid expanded to liquid condensed phase transition proportionally to the BG concentration. The monolayers were also transferred onto solid substrates and visualized using an atomic force microscope. The results obtained indicate almost complete miscibility of BG and DPPC in the monolayers at surface pressures present in the biological cell membrane (30-35·10(-3) N·m(-1)) for a BG mole fraction as high as 0.3. This makes the monolayer less packed and more disordered, leading to an increased permeability. The results support our previous molecular dynamics simulation data. PMID:27287132

  7. Fullerene films and fullerene-dodecylamine adduct monolayers at air-water interfaces studied by neutron and x-ray reflection

    DEFF Research Database (Denmark)

    Wang, J.Y.; Vaknin, D.; Uphaus, R.A.;

    1994-01-01

    for by a single model structure defined in terms of the dimensions of an average cell and its chemical composition. This model ascribes a total thickness of about 29 angstrom to the molecular interface layer with the following internal structure. The fullerenes (with several alkyl chains attached) form a central...... stratum and the remainder alkyl tails are located close to both the air and the water interfaces. The alkyl moieties close to the aqueous substrate are hydrated. The reflection experiments and the isotherms suggest that on average 8 +/- 3 dodecylamine molecules are present per fullerene, consistent within...

  8. The interaction of eugenol with cell membrane models at the air-water interface is modulated by the lipid monolayer composition.

    Science.gov (United States)

    Gonçalves, Giulia E G; de Souza, Fernanda S; Lago, João Henrique G; Caseli, Luciano

    2015-12-01

    Eugenol, a natural phenylpropanoid derivative with possible action in biological surfaces as microbicide, anesthetic and antioxidant, was incorporated in lipid monolayers of selected lipids at the air-water interface, representing cell membrane models. Interaction of eugenol with the lipids dipalmitoylphosphatidylcholine (DPPC), dioctadecyldimethylammonium bromide (DODAB), and dipalmitoylphosphatidylserine (DPPS) could be inferred by means of surface pressure-area isotherms and Polarization-Modulation Reflection-Absorption Spectroscopy. The interaction showed different effects on the different lipids. A higher monolayer expansion was observed for DPPS and DODAB, while more significant effects on the polar groups of the lipids were observed for DPPS and DPPC. These results pointed to the fact that the interaction of eugenol with lipid monolayers at the air-water interface is modulated by the lipid composition, which may be important to comprehend at the molecular level the interaction of this drug with biological surfaces.

  9. Molecular assemblies of 4-(hexadecyloxy)-n-(pyridinylmethylene)anilines at the air-water interface and Cu(II)-promoted vesicle formation via metal coordination.

    Science.gov (United States)

    Wang, Haibo; Miao, Wangen; Liu, Huijin; Zhang, Xianfeng; Du, Xuezhong

    2010-09-01

    The molecular assemblies of 4-(hexadecyloxy)-N-(pyridinylmethylene)anilines (HPA) at the air-water interface on pure water and aqueous Cu(II) subphases have been investigated using in situ infrared reflection absorption spectroscopy (IRRAS). The Schiff base units were oriented with their long axes almost perpendicular to the water surface, and both imine and pyridinyl nitrogen atoms of the Schiff base units were coordinated to Cu(II) ions together with their geometrical conversions. The alkyl chains in the monolayers were quantitatively determined on the assumption that the HPA monolayers at the air-water interface were composed of sublayers of alkyl chains and Schiff base units, and the chain orientation angle on pure water was 30 +/- 2 degrees and increased to 37 +/- 2 degrees on the aqueous Cu(II) subphase. The HPA amphiphiles could not be dispersed in pure water but could self-organize into vesicles with metal-coordinated headgroups and interdigitated-packed alkyl chains in the presence of Cu(II) ions in aqueous solution. Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), UV-vis spectroscopy, and small-angle X-ray diffraction (XRD) were used to investigate the aggregate structures and specific properties of the coordinated vesicles. PMID:20698514

  10. Morphology and thermochromic phase transition of merocyanine J-aggregate monolayers at the air-water and solid-water interfaces

    Science.gov (United States)

    Kato, Noritaka; Saito, Kentaro; Serata, Toshinori; Aida, Hiroaki; Uesu, Yoshiaki

    2001-07-01

    Thermal changes of the merocyanine dye (MD) monolayer at the air-water interface were investigated under various subphase conditions in order to elucidate the formation mechanism and to control morphological and chromatic properties of two-dimensional MD J-aggregate crystallites (JC) formed in the monolayer. The dissociation temperature (Td) of the JC to the monomer MD was measured for different counterions of MD molecules in the subphase. The JC size was found to be dependent on the subphase temperature; it becomes larger when the JC is formed at a temperature closer to Td. This phenomenon is qualitatively reproduced by the numerical simulation of the Cahn-Hilliard equation. In the case of the MD monolayer on the subphase which contains two kinds of counterions, it exhibits a reversible thermochromic transition between two different JC states. The chromatic change is discrete, and is attributed to the structural phase transition of the JC induced by the mutual recombination of two kinds of counterions to MD molecules. The structural difference between the high and low temperature JC states is examined by the point dipole model. The transition temperature and thermal hysteresis width can be varied by the fraction of 2 counterions. In situ observations using a multipurpose nonlinear optical microscope revealed that the transition is of first order and the nucleation and growth process of the low temperature phase in the high temperature matrix was observed. The JC size of the low temperature phase became much larger through the recrystallization process. For future application of this phenomenon, an airtight cell consisting of two monolayers at the solid-water interface and the subphase was developed. In the cell, the same reversible transition occurs, but with a slow relaxation.

  11. Controlling the assembly of hydrophobized gold nanoparticles at the air-water interface by varying the interfacial tension

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Shweta; Singh, Nahar [Material Characterization Division, National Physical Laboratory, New Delhi-110012 (India); Sastry, Murali [Tata Chemical Innovation Center, Anmol Pride, Baner Road, Pune-45 (India); Kakkar, Rita [Department of Chemistry, Delhi University, Delhi-110007 (India); Pasricha, Renu, E-mail: pasrichar@mail.nplindia.ernet.i [Material Characterization Division, National Physical Laboratory, New Delhi-110012 (India)

    2010-11-30

    Controlled assembly is the key to harness the nanoscale properties of nanoparticles in most technological applications and it has been an important challenge as it leads to the manipulation of interparticle properties. The present work depicts the control of the assembly of nanoparticles in the monolayers by evaporation kinetics and particle interactions at the air-liquid interface. In the presence of attractive particle-particle and particle-monolayers interactions, nanoparticles self assemble into a superlattice structure upon drying from a colloidal suspension on to the preformed lipid monolayers. This self-assembly mechanism produces monolayers with long-range ordering. However, rapid dewetting and high rate of evaporation can significantly undermine the extent of ordering. Using gold nanoparticles as vehicles for experimentation and by changing the monolayers and solvent, we here demonstrate that the extent of ordering of nanoparticles can be controlled.

  12. Effects of the conjugation of whey proteins with gellan polysaccharides on surfactant-induced competitive displacement from the air-water interface.

    Science.gov (United States)

    Cai, B; Ikeda, S

    2016-08-01

    Whey proteins can be used to stabilize foams and emulsions against coalescence because of their ability to form viscoelastic films at the interface that resist film rupture on collision between colloidal particles. However, whey proteins are competitively displaced from the interface if small-molecule surfactants are added, leading to destabilization of the entire system. This is because surfactants are more effective in molecular packing at the interface, and they lower interfacial tension to a greater degree than whey proteins do, but their interfacial films are poor in viscoelasticity. We hypothesized that whey proteins would become more resistant to surfactant-induced competitive displacement if they were conjugated with network-forming polysaccharides. The protein moiety of the conjugate would be expected to enable its adsorption to the interface, and the polysaccharide moiety would be expected to form self-assembled networks, strengthening the interfacial film as a whole. In this study, whey proteins were conjugated with gellan polysaccharides using the Maillard reaction. Atomic force microscopy images of interfacial films formed by the whey protein-gellan conjugate at the air-water interface and transferred onto mica sheets using the Langmuir-Blodgett method revealed that gellan did form self-assembled networks at the interface and that interfacial films also contained a large number of unconjugated whey protein molecules. Following the addition of a small-molecule surfactant (Tween 20) to the sub-phase, surface pressure increased, indicating spontaneous adsorption of surfactants to the interface. Atomic force microscopy images showed decreases in interfacial area coverage by whey proteins as surface pressure increased. At a given surface pressure, the interfacial area coverage by whey protein-gellan conjugates was greater than coverage by unconjugated whey proteins, confirming that whey proteins became more resistant to surfactant-induced displacement after

  13. Savinase action on bovine serum albumin (BSA) monolayers demonstrated with measurements at the air-water interface and liquid Atomic Force Microscopy (AFM) imaging

    DEFF Research Database (Denmark)

    Balashev, Konstantin; Callisen, Thomas H; Svendsen, Allan;

    2011-01-01

    We studied the enzymatic action of Savinase on bovine serum albumin (BSA) organized in a monolayer spread at the air/water interface or adsorbed at the mica surface. We carried out two types of experiments. In the first one we followed the degradation of the protein monolayer by measuring...... the surface pressure and surface area decrease versus time. In the second approach we applied AFM imaging of the supported BSA monolayers adsorbed on mica solid supports and extracted information for the enzyme action by analyzing the obtained images of the surface topography in the course of enzyme action...

  14. LTE-advanced air interface technology

    CERN Document Server

    Zhang, Xincheng

    2012-01-01

    Opportunities are at hand for professionals eager to learn and apply the latest theories and practices in air interface technologies. Written by experienced researchers and professionals, LTE-Advanced Air Interface Technology thoroughly covers the performance targets and technology components studied by 3GPP for LTE-Advanced. Besides being an explanatory text about LTE-Advanced air interface technology, this book exploits the technical details in the 3GPP specification, and explains the motivation and implication behind the specifications.After a general description of wireless cellular techno

  15. Hydroxyl radical reactivity at the air-ice interface

    Directory of Open Access Journals (Sweden)

    T. F. Kahan

    2010-01-01

    Full Text Available Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at air-ice interfaces, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH anthracene at air-water interfaces, but no loss was observed at air-ice interfaces. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL that exists at air-ice interfaces.

  16. How does spacer length of imidazolium gemini surfactants control the fabrication of 2D-Langmuir films of silver-nanoparticles at the air-water interface?

    Science.gov (United States)

    Datta, Sougata; Biswas, Joydeep; Bhattacharya, Santanu

    2014-09-15

    A series of gemini surfactants based on cationic imidazolium ring as polar headgroup, abbreviated as [Im-n-Im], 2Br(-) (n=2, 5, 6 and 12), was synthesized. Their ability to stabilize silver nanoparticles in aqueous media was investigated. The resulting suspensions were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). They exhibit specific morphologies by adopting different supramolecular assemblies in aqueous media depending on the internal packing arrangements and on the number of spacer methylene units [-(CH2)n-]. Individual colloids were extracted from the aqueous to chloroform layer and spread at the air/water interface to allow the formation of well-defined Langmuir films. By analysis of the surface pressure-area isotherms, the details about the packing behavior and orientation of the imidazolium gemini surfactant capped silver nanoparticles were obtained. Morphological features of the dynamic process of monolayer compression at the air-water interface were elucidated using Brewster angle microscopy (BAM). These monolayers were further transferred on mica sheets by the Langmuir-Blodgett technique at their associated collapse pressure and the morphology of these monolayers was investigated by atomic force microscopy (AFM). The number of spacer methylene units [-(CH2)n-] of the gemini surfactants exerted critical influence in modulating the characteristics of the resulting Langmuir films. PMID:24998058

  17. A semi-analytical calculation of the electrostatic pair interaction between nonuniformly charged colloidal spheres at an air-water interface

    Science.gov (United States)

    Lian, Zengju

    2016-07-01

    We study the electrostatic pair interaction between two nonuniformly like-charged colloidal spheres trapped in an air-water interface. Under the linear Poisson-Boltzmann approximation, a general form of the electrostatic potential for the system is shown in terms of multipole expansions. After combining the translation-rotation transform of the coordinates with the numerical multipoint collection, we give a semi-analytical result of the electrostatic pair interaction between the colloids. The pair interaction changes quantitatively or even qualitatively with different distributions of the surface charges on the particles. Because of the anisotropic distribution of the surface charge and the asymmetric dielectric medium, the dipole moment of the ion cloud associating with the particle orients diagonally to the air-water interface with an angle α. When the angle is large, the colloids interact repulsively, while they attract each other when the angle is small. The attractive colloids may be "Janus-like" charged and be arranged with some specific configurations. Whatever the repulsions or the attractions, they all decay asymptotically ∝1/d3 (d is the center-center distance of the particles) which is consistent with our general acknowledge. The calculation results also provide an insight of the effect of the ion concentration, particle size, and the total charge of the particle on the pair interaction between the particles.

  18. Simulated Solvation of Organic Ions II: Study of Linear Alkylated Carboxylate Ions in Water Nanodrops and in Liquid Water. Propensity for Air/Water Interface and Convergence to Bulk Solvation Properties.

    Science.gov (United States)

    Houriez, Céline; Meot-Ner Mautner, Michael; Masella, Michel

    2015-09-10

    We investigated the solvation of carboxylate ions from formate to hexanoate, in droplets of 50 to 1000 water molecules and neat water, by computations using standard molecular dynamics and sophisticated polarizable models. The carboxylate ions from methanoate to hexanoate show strong propensity for the air/water interface in small droplets. Only the ions larger than propanoate retain propensity for the interface in larger droplets, where their enthalpic stabilization by ion/water dispersion is reduced there by 3 kcal mol(-1) per CH2 group. This is compensated by entropy effects over +3.3 cal mol(-1) K(-1) per CH2 group. On the surface, the anionic headgroups are strongly oriented toward the aqueous core, while the hydrophobic alkyl chains are repelled into air and lose their structure-making effects. These results reproduce the structure-making effects of alkyl groups in solution, and suggest that the hydrocarbon chains of ionic headgroups and alkyl substituents solvate independently. Extrapolation to bulk solution using standard extrapolation schemes yields absolute carboxylate solvation energies. The results for formate and acetate yield a proton solvation enthalpy of about 270 kcal mol(-1), close to the experiment-based value. The largest carboxylate ions yield a value smaller by about 10 kcal mol(-1), which requires studies in much larger droplets. PMID:26287943

  19. Point-spread function associated with underwater imaging through a wavy air-water interface: theory and laboratory tank experiment.

    Science.gov (United States)

    Brown, W C; Majumdar, A K

    1992-12-20

    The point-spread function needed for imaging underwater objects is theoretically derived and compared with experimental results. The theoretical development is based on the emergent-ray model, in which the Gram-Charlier series for the non-Gaussian probability-density function for emergent angles through a wavy water surface was assumed. To arrive at the point-spread model, we used a finite-element methodology with emergent-ray angular probability distributions as fundamental building functions. The model is in good agreement with the experiment for downwind conditions. A slight deviation between theory and experiment was observed for the crosswind case; this deviation may be caused by the possible interaction of standing waves with the original air-ruffled capillary waves that were not taken into account in the model.

  20. Study of the iron corrosion at the interface of different media (water, air) submitted to protons irradiation

    International Nuclear Information System (INIS)

    During the deep geological disposal, stainless steel containers of the vitrified waste will be put in carbon steel overpacks. After the closing of the storage site, overpacks will be in contact with a humid air and a radioactive medium. After hundred years, overpacks could be in contact with water radiolysis in an anoxic medium. In this context, my PhD work is a fundamental study which is the understanding of the corrosion mechanisms of pure iron under proton irradiation. This corrosion is affected by the contact of iron with different atmospheres (air, nitrogen) and water. In the case of the atmospheric iron corrosion under irradiation, we have studied the influence of the proton beam flux. During this work, we have characterized the structure of the oxides formed at the iron surface. The structure formed does not correspond to iron oxides and hydroxides indexed. However, we have shown that the oxide structure is close to that of lepidocrocite and bernalite. Moreover, we have determined the oxygen diffusion coefficient in iron under irradiation and we have shown that the irradiation accelerates of 6 orders of magnitude the iron corrosion. In addition, the irradiations which were realized in different gas have put in evidence the negligible role of nitrates, and the importance of the O2/H2O coupling on the iron corrosion. Finally, we have shown the influence of the relative humidity, the maximum of the corrosion being observed for a relative humidity close to 45%. In the case of the iron corrosion in aqueous media under irradiation, the influence of the oxygen dissolved in water has been studied using a surface marker. We have put in evidence that the corrosion is twice more significant in aerated medium than in deaerated medium. Moreover, the influence of radicals has been shown. An irradiated sample is more corroded than a sample put in contact with a H2O2 solution. Finally, the follow-up of the iron potential under irradiation have shown the majority role of the

  1. Reorientation of the ‘free OH’ group in the top-most layer of air/water interface of sodium fluoride aqueous solution probed with sum-frequency generation vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Ran-Ran; Guo, Yuan; Wang, Hongfei

    2014-09-17

    Many experimental and theoretical studies have established the specific anion, as well as cation effects on the hydrogen-bond structures at the air/water interface of electrolyte solutions. However, the ion effects on the top-most layer of the air/water interface, which is signified by the non-hydrogen-bonded so-called ‘free O-H’ group, has not been discussed or studied. In this report, we present the measurement of changes of the orientational angle of the ‘free O-H’ group at the air/water interface of the sodium fluoride (NaF) solutions at different concentrations using the interface selective sum-frequency generation vibrational spectroscopy (SFG-VS) in the ssp and ppp polarizations. The polarization dependent SFG-VS results show that the average tilt angle of the ‘free O-H’ changes from about 35.3 degrees ± 0.5 degrees to 43.4 degrees ± 2.1degrees as the NaF concentration increase from 0 to 0.94M (nearly saturated). Such tilt angle change is around the axis of the other O-H group of the same water molecule at the top-most layer at the air/water interface that is hydrogen-bonded to the water molecules below the top-most layer. These results provide quantitative molecular details of the ion effects of the NaF salt on the structure of the water molecules at the top-most layer of the air/water interfacial, even though both the Na+ cation and the F- anion are believed to be among the most excluded ions from the air/water interface.

  2. Hydrodynamical entrapment of ciliates at the air-liquid interface

    Science.gov (United States)

    Ferracci, Jonathan; Ueno, Hironori; Numayama-Tsuruta, Keiko; Imai, Yohsuke; Yamaguchi, Takami; Ishikawa, Takuji

    2012-11-01

    We found the new phenomenon of the entrapment of ciliates at the air-water interface, though they are not trapped by a solid interface. We first characterize the behaviours of cells at the interface by comparing it to those away from interfaces. The results showed that the cell's swimming velocity is considerably reduced at the air-water interface. In order to experimentally verify the possible physiological causes of the entrapment, we observed their behaviours in absence of positive chemotaxis for oxygen and the negative geotaxis. The results illustrated that the entrapment phenomenon was not dependent on these physiological conditions. The experiments using surfactant revealed that the entrapment phenomenon was strongly affected by the velocity-stress conditions at the interface. This fact was confirmed numerically by a boundary element method, i.e. the stress-free condition at the air-liquid interface is one of the main mechanisms of the entrapment phenomenon found in the experiments. Since the entrapment phenomenon found in this study affects the cell-cell interactions and the mass transport at the interface, the knowledge obtained in this study is useful for better understanding the complex behaviours of swimming microorganisms in nature. PhD student in the Physiological Flow Studies Laboratory.

  3. Adsorption of Egg-PC to an Air/Water and Triolein/Water Bubble Interface: Use of the 2-Dimensional Phase Rule to Estimate the Surface Composition of a Phospholipid/Triolein/Water Surface as a Function of Surface Pressure

    OpenAIRE

    Mitsche, Matthew A.; Wang, Libo; Small, Donald M.

    2010-01-01

    Phospholipid monolayers play a critical role in the structure and stabilization of biological interfaces including all membranes, the alveoli of the lung, fat droplets in adipose tissue, and lipoproteins. The behavior of phospholipids in bilayers and at an air-water interface is well understood. However, the study of phospholipids at oil-water interfaces is limited due to technical challenges. In this study, egg-phosphatidylcholine (EPC) was deposited from small unilamellar vesicles onto a bu...

  4. Visualization of an adsorption model for surfactant transport from micelle solutions to a clean air/water interface using fluorescence microscopy.

    Science.gov (United States)

    Song, Qing; Yuan, Mingjun

    2011-05-01

    This work pertains to visualizing a transport model for adsorption of surfactants from micelle solutions onto a clean air/water interface. Under the condition of surfactant adsorption from very dilute solutions, the time scale for diffusion of a surfactant monomer is much slower than the time scale for kinetic breakdown of the aggregates. A theoretical model predicts two regimes for the adsorption dynamics. We visualize these two regimes under the mechanism of solubilization using fluorescence microscopy, in which an insoluble fluorescent probe, NBD-HAD (4-(hexadecylamino)-7-nitrobenz-2-oxa-1,3-diazole), is used to illuminate the micelles. The dye fluoresces in the microenvironment of micelles but is quenched in the aqueous solution on laser excitation. The region containing micelles is illuminated, but the region which does not contain micelles appears dark. For surfactant solution of C(14)E(6) at concentration just above the critical micelle concentration (C(CMC)), C(CMC)=4.4 mg/L, a dark region between the bright image of the air/water interface and the micelle-containing zone is observed. This dark region becomes smaller with time and finally disappears once equilibrium is reached. For a surfactant solution of C(14)E(6) at the concentration of 4.74C(CMC), which is higher than a critical total surfactant concentration (C(T)(c)) of 4.25C(CMC), we observe bright images through surfactant solutions during the adsorption process. Fluorescence images validate the theoretical model. PMID:21349535

  5. Thin film formation at the air-water interface and on solid substrates of soluble axial substituted cis-bis-decanoate tin phthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Campos-Teran, Jose, E-mail: jcampos@correo.cua.uam.mx [Departamento de Procesos y Tecnologia, DCNI, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40-sexto piso, Col. Hidalgo, D. F., 001120 (Mexico); Garza, Cristina [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, P. O. Box 20-364, D. F., 01000 (Mexico); Beltran, Hiram I. [Departamento de Ciencias Naturales, DCNI, Universidad Autonoma Metropolitana-Cuajimalpa, Artificios 40-sexto piso, Col. Hidalgo, D. F., 001120 (Mexico); Castillo, Rolando [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, P. O. Box 20-364, D. F., 01000 (Mexico)

    2012-01-01

    Herein we study thin films of a recent kind of soluble axial substituted cis-bis-decanoate-tin{sup IV} phthalocyanine (PcSn10) at the air/water interface, which were compressed isothermally and observed with Brewster Angle Microscopy. The air/water interfacial behavior of the films suggests that there are strong interactions among the PcSn10 molecules, which produces multilayers and 3D self-assemblies that prevent the formation of a Langmuir monolayer. Langmuir-Blodgett deposits of these films on both mica (negatively charged) and mild steel (positively charged) surfaces were developed. Information about the morphology of the film was obtained by using atomic force microscopy. We found structural differences in the PcSn10 thin films deposited on both substrates, suggesting that a combination of {pi}-{pi}, {sigma}-{pi} and Van der Waals interactions are the leading factors for the deposition, and consequently, for the control of supramolecular order. Our findings provide insights in the design of phthalocyanine molecules for the development of highly ordered and reproducible thin films.

  6. Spread mixed monolayers of deoxycholic and dehydrocholic acids at the air-water interface, effect of subphase pH. Characterization by axisymmetric drop shape analysis.

    Science.gov (United States)

    Messina, Paula V; Fernández-Leyes, Marcos D; Prieto, Gerardo; Ruso, Juan M; Sarmiento, Félix; Schulz, Pablo C

    2008-01-01

    Bile acids (deoxycholic and dehydrocholic acids) spread mixed monolayers behavior at the air/water interface were studied as a function of subphase pH using a constant surface pressure penetration Langmuir balance based on the Axisymmetric Drop Shape Analysis (ADSA). We examined the influence of electrostatic, hydrophobic and hydration forces on the interaction between amphiphilic molecules at the interface by the collapse area values, the thermodynamic parameters and equation of state virial coefficients analysis. The obtained results showed that at neutral (pH=6.7) or basic (pH=10) subphase conditions the collapse areas values are similar to that of cholanoic acid and consistent with the cross-sectional area of the steroid nucleus (approximately 40 A(2)). The Gibbs energy of mixing values (DeltaG(mix) or =1). Such behavior indicates that the polar groups of the molecules interacts each other more strongly by repulsive electrostatic forces than with the more hydrophobic part of the molecule.

  7. Nanostructure of polymer monolayer and polyelectrolyte brush at air/water interface by X-ray and neutron reflectometry

    CERN Document Server

    Matsuoka, H; Matsumoto, K

    2003-01-01

    The nanostructure of amphiphilic diblock copolymer monolayer on water was directly investigated by in situ X-ray and neutron reflectivity techniques. The diblock copolymer consists of polysilacyclobutane, which is very flexible, as a hydrophobic block and polymethacrylic acid, an anionic polymer, as a hydrophilic block. The polymers with shorter hydrophilic segment formed a very smooth and uniform monolayer with hydrophobic layer on water and dense hydrophilic layer under the water. But the longer hydrophilic segment polymer formed three-layered monolayer with polyelectrolyte brush in addition to hydrophobic and dense hydrophilic layers. The dense hydrophilic layer is thought to be formed to avoid a contact between hydrophobic polymer layer and water. Its role is something like a 'carpet'. An additional interesting information is that the thickness of the 'carpet layer' is almost 15A, independent the surface pressure and hydrophilic polymer length. Highly quantitative information was obtained about the nanost...

  8. Binding structure and kinetics of surfactin monolayer formed at the air/water interface to counterions: A molecular dynamics simulation study.

    Science.gov (United States)

    Gang, Hongze; Liu, Jinfeng; Mu, Bozhong

    2015-10-01

    The binding structure and kinetics of ionized surfactin monolayer formed at the air/water interface to five counterions, Li+, Na+, K+, Ca2+, and Ba2+ (molar ratios of surfactin to monovalent and divalent counterions are 1:2 and 1:1 respectively), have been studied using molecular dynamics simulation. The results show that surfactin exhibits higher binding affinity to divalent counterions, Ca2+, and Ba2+, and smaller monovalent counterion, Li+, than Na+ and K+. Both carboxyl groups in surfactin are accessible for counterions, but the carboxyl group in Glu1 is easier to access by counterions than Asp5. Salt bridges are widely built between carboxyl groups by counterions, and the probability of the formation of intermolecular salt bridge is markedly larger than that of intramolecular salt bridge. Divalent counterions perform well in forming salt bridges between carboxyl groups. The salt bridges mediated by Ca2+ are so rigid that the lifetimes are about 0.13 ns, and the break rates of these salt bridges are 1-2 orders of magnitude smaller than those mediated by K+ which is about 5 ps in duration. The positions of the hydration layer of carboxyl groups are independent of counterions, but the bound counterions induce the dehydration of carboxyl groups and disturb the hydrogen bonds built between carboxyl group and hydration water.

  9. Clean Air and Water

    Centers for Disease Control (CDC) Podcasts

    2007-04-10

    The air we breathe and the water we drink are both vital components of our health. Nevertheless, bacteria, pollutants, and other contaminates can alter life-giving air and water into health-threatening hazards. Learn about how scientists at the Centers for Disease Control and Prevention work to protect the public from air and water-related health risks.  Created: 4/10/2007 by CDC National Center for Environmental Health.   Date Released: 4/13/2007.

  10. Conformational analysis of gramicidin-gramicidin interactions at the air/water interface suggests that gramicidin aggregates into tube-like structures similar as found in the gramicidin-induced hexagonal HII phase

    NARCIS (Netherlands)

    Brasserua, R.; Killian, J.A.; Kruijff, B. de; Ruysschaert, J.M.

    1987-01-01

    The energetics of interaction and the type of aggregate structure in lateral assemblies of up to five gramicidin molecules in the β6.3 helical conformation at the air/water interface was calculated using conformational analysis procedures. It was found that within the aggregate two types of gramicid

  11. Organization of lipids in the artificial outer membrane of bull spermatozoa reconstructed at the air-water interface.

    Science.gov (United States)

    Le Guillou, J; Ropers, M-H; Gaillard, C; David-Briand, E; Desherces, S; Schmitt, E; Bencharif, D; Amirat-Briand, L; Tainturier, D; Anton, M

    2013-08-01

    Cryopreservation is widely used to preserve the quality of bull spermatozoa over time. Sequestration of seminal plasma proteins by low density lipoproteins and formation of a protective film around the spermatozoa membrane by low density lipoproteins were the main mechanisms proposed. However, the organization of lipids in the outer leaflet of the spermatozoa membrane has been never considered as a possible parameter. This study evaluated whether a change in the organization of the outer leaflet of the spermotozoa membrane could occur during cooling down. The organization of the main components of the spermatozoa membrane's outer layer at the liquid-gas interface was analysed. Cryopreservative media (at 8° and 34°C) were used to study the miscibility of the spermatozoa membrane lipids using epifluorescence imaging and by tensiometry on Langmuir films. The results show that the four lipids: sphingomyelin, cholesterol, 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PC) and plasmalogen 1-(1Z-octadecenyl)-2-docosahexaenoyl-sn-glycero-3-phosphocholine (P-PC) were not fully miscible and their organization was controlled by temperature. Cholesterol and sphingomyelin form condensed domains surrounded by a mixture of PC and P-PC at 34°C while these condensed domains are surrounded by separated domains of pure PC and pure P-PC at 8°C. The organization of the outer membrane lipids, in particular the separation of PC and P-PC lipids during cooling down, must be considered to fully understand preservation of membrane integrity during cryopreservation. PMID:23563290

  12. Measurement of the Surface Dilatational Viscosity of an Insoluble Surfactant Monolayer at the Air/Water Interface Using a Pendant Drop Apparatus

    Science.gov (United States)

    Lorenzo, Jose; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

    2000-01-01

    When a fluid interface with surfactants is at rest, the interfacial stress is isotropic (as given by the equilibrium interfacial tension), and is described by the equation of state which relates the surface tension to the surfactant surface concentration. When surfactants are subjected to shear and dilatational flows, flow induced interaction of the surfactants; can create interfacial stresses apart from the equilibrium surface tension. The simplest relationship between surface strain rate and surface stress is the Boussinesq-Scriven constitutive equation completely characterized by three coefficients: equilibrium interfacial tension, surface shear viscosity, and surface dilatational viscosity Equilibrium interfacial tension and surface shear viscosity measurements are very well established. On the other hand, surface dilatational viscosity measurements are difficult because a flow which change the surface area also changes the surfactant surface concentration creating changes in the equilibrium interfacial tension that must be also taken into account. Surface dilatational viscosity measurements of existing techniques differ by five orders of magnitude and use spatially damped surface waves and rapidly expanding bubbles. In this presentation we introduce a new technique for measuring the surface dilatational viscosity by contracting an aqueous pendant drop attached to a needle tip and having and insoluble surfactant monolayer at the air-water interface. The isotropic total tension on the surface consists of the equilibrium surface tension and the tension due to the dilation. Compression rates are undertaken slow enough so that bulk hydrodynamic stresses are small compared to the surface tension force. Under these conditions we show that the total tension is uniform along the surface and that the Young-Laplace equation governs the drop shape with the equilibrium surface tension replaced by the constant surface isotropic stress. We illustrate this technique using

  13. Monolayers of gemini surfactants and their catanionic mixtures with sodium dodecyl sulfate at the air-water interface: Chain length and composition effects

    International Nuclear Information System (INIS)

    Monolayers of cationic gemini surfactants and their catanionic mixtures with sodium dodecyl sulfate (SDS), have been investigated with the Langmuir trough technique, at the air-water interface. The gemini surfactants are of the alkanediyl-α,ω-bis(alkyldimethylammonium) type, here designated as m-2-m, where m and 2 are the alkyl chain and spacer lengths, respectively. For the neat geminis, the stability of the monolayer increases as the chain length increases, starting from soluble films of 12-2-12 to stable films of 18-2-18. For the equicharged m-2-m/SDS mixtures (with m = 12, 14, 16 and 18), stable monolayers are obtained. The effect of the gemini chain length on the phase behavior and molecular organization of the films is discussed on the basis of pressure-area isotherms for compression or compression-expansion cycles. The pressure-temperature plots, at constant trough area, yield the desorption temperature and suggest the desorption mechanism of the film molecules. Furthermore, the effect of the mixing molar ratio between m-2-m and SDS on the isotherms, for m = 12 and 14, has also been investigated. It is concluded from the mean area per molecule that the gemini molecules when in excess with respect to equicharged composition desorb from the film, so that the electroneutral composition is maintained

  14. Surface interactions, thermodynamics and topography of binary monolayers of Insulin with dipalmitoylphosphatidylcholine and 1-palmitoyl-2-oleoylphosphatidylcholine at the air/water interface.

    Science.gov (United States)

    Grasso, E J; Oliveira, R G; Maggio, B

    2016-02-15

    The molecular packing, thermodynamics and surface topography of binary Langmuir monolayers of Insulin and DPPC (dipalmitoylphosphatidylcholine) or POCP (1-palmitoyl-2-oleoylphosphatidylcholine) at the air/water interface on Zn(2+) containing solutions were studied. Miscibility and interactions were ascertained by the variation of surface pressure-mean molecular area isotherms, surface compressional modulus and surface (dipole) potential with the film composition. Brewster Angle Microscopy was used to visualize the surface topography of the monolayers. Below 20mN/m Insulin forms stable homogenous films with DPPC and POPC at all mole fractions studied (except for films with XINS=0.05 at 10mN/m where domain coexistence was observed). Above 20mN/m, a segregation process between mixed phases occurred in all monolayers without squeezing out of individual components. Under compression the films exhibit formation of a viscoelastic or kinetically trapped organization leading to considerable composition-dependent hysteresis under expansion that occurs with entropic-enthalpic compensation. The spontaneously unfavorable interactions of Insulin with DPPC are driven by favorable enthalpy that is overcome by unfavorable entropic ordering; in films with POPC both the enthalpic and entropic effects are unfavorable. The surface topography reveals domain coexistence at relatively high pressure showing a striped appearance. The interactions of Insulin with two major membrane phospholipids induces composition-dependent and long-range changes of the surface organization that ought to be considered in the context of the information-transducing capabilities of the hormone for cell functioning.

  15. Combined effect of synthetic protein, Mini-B, and cholesterol on a model lung surfactant mixture at the air-water interface.

    Science.gov (United States)

    Chakraborty, Aishik; Hui, Erica; Waring, Alan J; Dhar, Prajnaparamita

    2016-04-01

    The overall goal of this work is to study the combined effects of Mini-B, a 34 residue synthetic analog of the lung surfactant protein SP-B, and cholesterol, a neutral lipid, on a model binary lipid mixture containing dipalmitolphosphatidylcholine (DPPC) and palmitoyl-oleoyl-phosphatidylglycerol (POPG), that is often used to mimic the primary phospholipid composition of lung surfactants. Using surface pressure vs. mean molecular area isotherms, fluorescence imaging and analysis of lipid domain size distributions; we report on changes in the structure, function and stability of the model lipid-protein films in the presence and absence of varying composition of cholesterol. Our results indicate that at low cholesterol concentrations, Mini-B can prevent cholesterol's tendency to lower the line tension between lipid domain boundaries, while maintaining Mini-B's ability to cause reversible collapse resulting in the formation of surface associated reservoirs. Our results also show that lowering the line tension between domains can adversely impact monolayer folding mechanisms. We propose that small amounts of cholesterol and synthetic protein Mini-B can together achieve the seemingly opposing requirements of efficient LS: fluid enough to flow at the air-water interface, while being rigid enough to oppose irreversible collapse at ultra-low surface tensions. PMID:26775740

  16. Multiple H-bonds directed self-assembly of an amphiphilic and plate-like codendrimer with janus faces at water-air interface.

    Science.gov (United States)

    Yang, Miao; Wang, Wei; Lieberwirth, Ingo; Wegner, Gerhard

    2009-05-01

    An amphiphilic diblock codendrimer composed of a third generation poly(methallyl dichloride) end-capped by eight hydroxyl groups (PMDC(OH)(8)) and a second generation poly(urethane amide) end-capped by four alkyl groups (PUA(C16)(4)) were found to self-assemble into highly oriented ribbons at the water-air interface. Further investigation on the ribbon formation shows that the ribbons are hierarchically self-organized by the janus and plate-like shape of g3-PMDC(OH)(8)-b-g2-PUA(C16)(4). Sextuple H-bonds existing at different positions of the molecular plate are the main driving force for the one-dimensional growth of the ribbon. The recognition of these H-bonds leads to a highly ordered stacking of the codendrimers, and the crystallization of the alkyl chains results in a primary ribbon with a ca. 7.6 +/- 0.5 nm width. The primary ribbons prefer to organize into secondary ribbons with an average width of 53 +/- 6.0 nm. The manner of recognition and assembly is similar to the organization of a kind of toy building block with janus faces, which provides a new strategy to the design of well-defined nanomaterials. PMID:19361164

  17. Sea spray production by bag breakup mode of fragmentation of the air-water interface at strong and hurricane wind

    Science.gov (United States)

    Troitskaya, Yuliya; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil; Zilitinkevich, Sergej

    2016-04-01

    Sea sprays is a typical element of the marine atmospheric boundary layer (MABL) of large importance for marine meteorology, atmospheric chemistry and climate studies. They are considered as a crucial factor in the development of hurricanes and severe extratropical storms, since they can significantly enhance exchange of mass, heat and momentum between the ocean and the atmosphere. This exchange is directly provided by spume droplets with the sizes from 10 microns to a few millimeters mechanically torn off the crests of a breaking waves and fall down to the ocean due to gravity. The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Experimental core of our work comprise laboratory experiments employing high-speed video-filming, which have made it possible to disclose how water surface looks like at extremely strong winds and how exactly droplets are torn off wave crests. We classified events responsible for spume droplet, including bursting of submerged bubbles, generation and breakup of "projections" or liquid filaments (Koa, 1981) and "bag breakup", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film, "bags". The process is similar to "bag-breakup" mode of fragmentation of liquid droplets and jets in gaseous flows. Basing on statistical analysis of results of these experiments we show that the main mechanism of spray-generation is attributed to "bag-breakup mechanism On the base of general principles

  18. Water at interface with proteins

    CERN Document Server

    Franzese, Giancarlo; Iskrov, Svilen

    2010-01-01

    Water is essential for the activity of proteins. However, the effect of the properties of water on the behavior of proteins is only partially understood. Recently, several experiments have investigated the relation between the dynamics of the hydration water and the dynamics of protein. These works have generated a large amount of data whose interpretation is debated. New experiments measure the dynamics of water at low temperature on the surface of proteins, finding a qualitative change (crossover) that might be related to the slowing down and stop of the protein's activity (protein glass transition), possibly relevant for the safe preservation of organic material at low temperature. To better understand the experimental data several scenarios have been discussed. Here, we review these experiments and discuss their interpretations in relation with the anomalous properties of water. We summarize the results for the thermodynamics and dynamics of supercooled water at an interface. We consider also the effect o...

  19. Controlled deposition of functionalized silica coated zinc oxide nano-assemblies at the air/water interface for blood cancer detection.

    Science.gov (United States)

    Pandey, Chandra Mouli; Dewan, Srishti; Chawla, Seema; Yadav, Birendra Kumar; Sumana, Gajjala; Malhotra, Bansi Dhar

    2016-09-21

    We report results of the studies relating to controlled deposition of the amino-functionalized silica-coated zinc oxide (Am-Si@ZnO) nano-assemblies onto an indium tin oxide (ITO) coated glass substrate using Langmuir-Blodgett (LB) technique. The monolayers have been deposited by transferring the spread solution of Am-Si@ZnO stearic acid prepared in chloroform at the air-water interface, at optimized pressure (16 mN/m), concentration (10 mg/ml) and temperature (23 °C). The high-resolution transmission electron microscopic studies of the Am-Si@ZnO nanocomposite reveal that the nanoparticles have a microscopic structure comprising of hexagonal assemblies of ZnO with typical dimensions of 30 nm. The surface morphology of the LB multilayer observed by scanning electron microscopy shows uniform surface of the Am-Si@ZnO film in the nanometer range (<80 nm). These electrodes have been utilized for chronic myelogenous leukemia (CML) detection by covalently immobilizing the amino-terminated oligonucleotide probe sequence via glutaraldehyde as a crosslinker. The response studies of these fabricated electrodes carried out using electrochemical impedance spectroscopy show that this Am-Si@ZnO LB film based nucleic acid sensor exhibits a linear response to complementary DNA (10(-6)-10(-16) M) with a detection limit of 1 × 10(-16) M. This fabricated platform is validated with clinical samples of CML positive patients and the results demonstrate its immense potential for clinical diagnosis. PMID:27590542

  20. Conformational analysis of gramicidin-gramicidin interactions at the air/water interface suggests that gramicidin aggregates into tube-like structures similar as found in the gramicidin-induced hexagonal HII phase

    OpenAIRE

    Brasserua, R.; Killian, J A; Kruijff, B. de; Ruysschaert, J M

    1987-01-01

    The energetics of interaction and the type of aggregate structure in lateral assemblies of up to five gramicidin molecules in the β6.3 helical conformation at the air/water interface was calculated using conformational analysis procedures. It was found that within the aggregate two types of gramicidin interaction occur. One leading to a linear organization with a mean interaction energy between monomers of −6 kcal/mol and one in a perpendicular direction leading to a circularly organization w...

  1. Ordering of solid microparticles at liquid crystal-water interfaces.

    Science.gov (United States)

    Lin, I-Hsin; Koenig, Gary M; de Pablo, Juan J; Abbott, Nicholas L

    2008-12-25

    We report a study of the organization of solid microparticles at oil-water interfaces, where the oil is a thermotropic liquid crystal (LC). The study was motivated by the proposition that microparticle organization and LC ordering would be coupled at these interfaces. Surfactant-functionalized polystyrene microparticles were spread at air-water interfaces at prescribed densities and then raised into contact with supported films of nematic 4-pentyl-4'-cyanobiphenyl (5CB). Whereas this method of sample preparation led to quantitative transfer of microparticles from the air-water interface to an isotropic oil-water interface, forces mediated by the nematic order of 5CB were observed to rapidly displace microparticles laterally across the interface of the water upon contact with nematic 5CB, thus leading to a 65% decrease in the density of microparticles at the LC-water interface. These lateral forces were determined to be caused by microparticle-induced deformation of the LC, the energy of which was estimated to be approximately 10(4) kT. We also observed microparticles transferred to the LC-water interface to assemble into chainlike structures that were not seen when using isotropic oils, indicating the presence of LC-mediated interparticle interactions at this interface. Optical textures of the LC in the vicinity of the microparticles were consistent with formation of topological defects with dipolar symmetry capable of promoting the chaining of the microparticles. The presence of microparticles at the interface also impacted the ordering of the LCs, including a transition from parallel to perpendicular ordering of the LC with increasing microparticle density. These observations, when combined, demonstrate that LC-mediated interactions can direct the assembly of solid microparticles at LC-water interfaces and that the ordering of the LC is also strongly coupled to the presence of microparticles.

  2. DIFFUSIVE EXCHANGE OF GASEOUS POLYCYCLIC AROMATIC HYDROCARBONS AND POLYCHLORINATED BIPHENYLS ACROSS THE AIR-WATER INTERFACE OF THE CHESAPEAKE BAY. (R825245)

    Science.gov (United States)

    Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air-water gas exchange rates. Gaseous PAHs ar...

  3. The trade-off between heat tolerance and metabolic cost drives the bimodal life strategy at the air-water interface

    Science.gov (United States)

    Fusi, Marco; Cannicci, Stefano; Daffonchio, Daniele; Mostert, Bruce; Pörtner, Hans-Otto; Giomi, Folco

    2016-01-01

    The principle of oxygen and capacity limitation of thermal tolerance in ectotherms suggests that the long-term upper limits of an organism's thermal niche are equivalent to the upper limits of the organism's functional capacity for oxygen provision to tissues. Air-breathing ectotherms show wider thermal tolerances, since they can take advantage of the higher availability of oxygen in air than in water. Bimodal species move from aquatic to aerial media and switch between habitats in response to environmental variations such as cyclical or anomalous temperature fluctuations. Here we tested the prediction that bimodal species cope better with thermal stress than truly aquatic species using the crab Pachygrapsus marmoratus as a model species. When in water, oxygen consumption rates of P. marmoratus acutely rise during warming. Beyond a temperature threshold of 23 °C the crab's aerobic metabolism in air remains lower than in water. In parallel, the haemolymph oxygen partial pressure of submerged animals progressive decreases during warming, while it remains low but constant during emersion. Our results demonstrate the ability of a bimodal breathing ectotherm to extend its thermal tolerance during air-breathing, suggesting that there are temperature-related physiological benefits during the evolution of the bimodal life style. PMID:26758742

  4. The trade-off between heat tolerance and metabolic cost drives the bimodal life strategy at the air-water interface

    KAUST Repository

    Fusi, Marco

    2016-01-13

    The principle of oxygen and capacity limitation of thermal tolerance in ectotherms suggests that the long-term upper limits of an organism\\'s thermal niche are equivalent to the upper limits of the organism\\'s functional capacity for oxygen provision to tissues. Air-breathing ectotherms show wider thermal tolerances, since they can take advantage of the higher availability of oxygen in air than in water. Bimodal species move from aquatic to aerial media and switch between habitats in response to environmental variations such as cyclical or anomalous temperature fluctuations. Here we tested the prediction that bimodal species cope better with thermal stress than truly aquatic species using the crab Pachygrapsus marmoratus as a model species. When in water, oxygen consumption rates of P. marmoratus acutely rise during warming. Beyond a temperature threshold of 23 °C the crab\\'s aerobic metabolism in air remains lower than in water. In parallel, the haemolymph oxygen partial pressure of submerged animals progressive decreases during warming, while it remains low but constant during emersion. Our results demonstrate the ability of a bimodal breathing ectotherm to extend its thermal tolerance during air-breathing, suggesting that there are temperature-related physiological benefits during the evolution of the bimodal life style.

  5. Pulmonary surfactant proteins SP-B and SP-C in spread monolayers at the air-water interface: II. Monolayers of pulmonary surfactant protein SP-C and phospholipids.

    OpenAIRE

    Taneva, S; Keough, K M

    1994-01-01

    The interaction of the hydrophobic pulmonary surfactant protein SP-C with dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) and DPPC:DPPG (7:3, mol:mol) in spread monolayers at the air-water interface has been studied. At low concentrations of SP-C (about 0.5 mol% or 3 weight%protein) the protein-lipid films collapsed at surface pressures of about 70 mN.m-1, comparable to those of the lipids alone. At initial protein concentrations higher than 0.8 mol%, or 4 weight...

  6. Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air-water interface and of the sea surface microlayer

    Science.gov (United States)

    Zhou, S.; Gonzalez, L.; Leithead, A.; Finewax, Z.; Thalman, R.; Vlasenko, A.; Vagle, S.; Miller, L.; Li, S.-M.; Bureekul, S.; Furutani, H.; Uematsu, M.; Volkamer, R.; Abbatt, J.

    2013-07-01

    Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acid (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air-seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) and light-emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon-carbon double bonds in the PUFA molecules. In addition, two highly reactive di-carbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and atmosphere of the marine boundary layer is discussed.

  7. Isotopic composition of carbon in atmospheric air; use of a diffusion model at the water/atmosphere interface in Velenje Basin

    Directory of Open Access Journals (Sweden)

    Tjaša Kanduč

    2015-07-01

    Full Text Available CO2 concentrations (partial pressure of CO2, pCO2, and isotope compositions of carbon dioxide in air (δ13CCO2, temperature (T and relative humidity (H have been measured in the atmosphere in the Velenje Basin. Samples were collected monthly in the calendar year 2011 from 9 locations in the area where the largest thermal power plant in Slovenia with the greatest emission of CO2 to the atmosphere (around 4M t/year is located. Values of pCO2 ranged from 239 to 460 ppm with an average value of 294 ppm, which is below the average atmospheric CO2 pressure (360 ppm. δ13CCO2 ranged from -18.0 to -6.4 ‰, with an average value of -11.7 ‰. These values are similar to those measured in Wroclaw, Poland. We performed the comparison of δ13CCO2 values in atmospheric air with Wroclaw since researchers used similar approach to trace δ13CCO2 around anthropogenic sources. The isotopic composition of dissolved inorganic carbon (δ13CDIC in rivers and lakes from the Velenje basin changes seasonally from -13.5 to -7.1‰. The values of δ13CDIC indicate the occurrence of biogeochemical processes in the surface waters, with dissolution of carbonates and degradation of organic matter being the most important. A concentration and diffusion model was used to calculate the time of equilibration between dissolved inorganic carbon in natural sources (rivers and atmospheric CO2.

  8. The effect of diesters and lauric acid on rheological properties of air/water interfaces stabilized by oligofructose lauric acid monoesters

    NARCIS (Netherlands)

    Kempen, van S.E.H.J.; Schols, H.A.; Linden, van der E.; Sagis, L.M.C.

    2013-01-01

    In this study, the rheological properties of interfaces stabilized by oligofructose fatty acid esters were elucidated. First, the properties of interfaces stabilized by monoesters (ME), diesters (DE), lauric acid (LA), oligofructose (OF), and mixtures of ME with DE, LA, or OF were studied. Second, t

  9. Automatic Web-Based, Radio-Network System To Monitor And Control Equipment For Investigating Gas Flux At Water - Air Interfaces

    Science.gov (United States)

    Duc, N. T.; Silverstein, S.; Wik, M.; Beckman, P.; Crill, P. M.; Bastviken, D.; Varner, R. K.

    2015-12-01

    Aquatic ecosystems are major sources of greenhouse gases (GHG). Robust measurements of natural GHG emissions are vital for evaluating regional to global carbon budgets and for assessing climate feedbacks on natural emissions to improve climate models. Diffusive and ebullitive (bubble) transport are two major pathways of gas release from surface waters. To capture the high temporal variability of these fluxes in a well-defined footprint, we designed and built an inexpensive automatic device that includes an easily mobile diffusive flux chamber and a bubble counter, all in one. Besides a function of automatically collecting gas samples for subsequent various analyses in the laboratory, this device utilizes low cost CO2 sensor (SenseAir, Sweden) and CH4 sensor (Figaro, Japan) to measure GHG fluxes. To measure the spatial variability of emissions, each of the devices is equipped with an XBee module to enable a local radio communication DigiMesh network for time synchronization and data readout at a server-controller station on the lakeshore. Software of this server-controller is operated on a low cost Raspberry Pi computer which has a 3G connection for remote monitoring - controlling functions from anywhere in the world. From field studies in Abisko, Sweden in summer 2014 and 2015, the system has resulted in measurements of GHG fluxes comparable to manual methods. In addition, the deployments have shown the advantage of a low cost automatic network system to study GHG fluxes on lakes in remote locations.

  10. Modeling of Kinetics of Air Entrainment in Water Produced by Vertically Falling Water Flow

    Directory of Open Access Journals (Sweden)

    Adelė VAIDELIENĖ

    2014-09-01

    Full Text Available This study analyzes the process of air entrainment in water caused by vertically falling water flow in the free water surface. The new kinetic model of air entrainment in water was developed. This model includes the process of air entrapment, as well as air removal, water sputtering and resorption. For the experimental part of this study a new method based on digital image processing was developed. Theoretical and experimental methods were used for determining air concentration and its distribution in water below the air-water interface. A new presented mathematical model of air entrainment process allows determining of air bubbles and water droplets concentrations distribution. The obtained theoretical and experimental results were in good agreement. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4871

  11. Chemical physics of water-water interfaces

    NARCIS (Netherlands)

    Vis, Mark; Erné, Ben H; Tromp, Robert H

    2016-01-01

    A brief review is given on recent progress in experimental and theoretical investigations of the interface between coexisting aqueous phases of biopolymers. The experimental aspects are introduced using results obtained from a model system consisting of aqueous mixtures of nongelling gelatin and dex

  12. Surface Pressure and Elasticity of Hydrophobin HFBII Layers on the Air-Water Interface: Rheology Versus Structure Detected by AFM Imaging

    NARCIS (Netherlands)

    Stanimirova, R.D.; Gurkov, T.D.; Kralchevsky, P.A.; Balashev, K.T.; Stoyanov, S.D.; Pelan, E.G.

    2013-01-01

    Here, we combine experiments with Langmuir trough and atomic force microscopy (AFM) to investigate the reasons for the special properties of layers from the protein HFBII hydrophobin spread on the airwater interface. The hydrophobin interfacial layers possess the highest surface dilatational and she

  13. 3种芦丁脂肪酸酯在空气/水界面的成膜性质%Monolayers of Three Amphiphilic Esters of Rutin at the Air-water Interface

    Institute of Scientific and Technical Information of China (English)

    段煜; 杜宗良; 李瑞霞; 吴大诚

    2011-01-01

    The π - A isotherms for monolayers of three amphiphilic rutin esters, rutin - 4''' - 0 - stearate ( RS ), rutin - 4''' - 0 -laurate (RL) and rutin -4''' -0 -caproate (RC), were measured at the air-water interface and air-aqueous aluminum sulfate solution interface.The properties of the monolayers of three rutin esters were related to the carbon number of alkyl, the compression rate and the property of substrate.Although RS and RL showed scant water solubility, they formed monolayers with the liquid-expanded phase when spread on water.While RC could not form insoluble monolayer at the air-water interface, which may be due to the larger water solubility of RC.Appropriately low compression rate was critical to the formation of relatively stable monolayers.When spread on an aqueous aluminum sulfate solution, the formation of a complex between the aluminum ions and the rutin ester resulted in higher values of acoll for RS and RL monolayers compared with their values on water, and RC could spread as liquid-expanded phase monolayer.The present results provided valuable information for investigating the interaction of flavonoids and biomembranes and the anti-oxidant mechanism of flavonoids.%采用LB膜分析仪分别研究了芦丁硬脂酸酯(RS)、芦丁月桂酸酯(RL)和芦丁正己酸酯(RC)在空气/水界面的成膜性质,及亚相中的Al3+对3种芦丁脂肪酸酯成膜性质的影响.结果显示,3种芦丁脂肪酸酯的成膜性质与其疏水基的碳链长度、压膜速度和亚相性质有关.RS和RL能在水面铺展为液态扩张膜,RC则不能成膜.引入芦丁分子中的疏水基碳链越长,成膜越稳定.慢速压膜利于膜稳定性,膜的崩溃压大;较快速压膜能使更多膜分子保留在水表面,膜的平均分子面积大.选择适宜的压膜速度对得到比较稳定的芦丁脂肪酸酯膜很关键.当亚相中含Al3+时,RS、RL和RC均铺展成液态扩张膜,且RS膜和RL膜崩溃时的分子面积(acoll)大于它们在水表

  14. Rheology of asphaltene-toluene/water interfaces.

    Science.gov (United States)

    Sztukowski, Danuta M; Yarranton, Harvey W

    2005-12-01

    The stability of water-in-crude oil emulsions is frequently attributed to a rigid asphaltene film at the water/oil interface. The rheological properties of these films and their relationship to emulsion stability are ill defined. In this study, the interfacial tension, elastic modulus, and viscous modulus were measured using a drop shape analyzer for model oils consisting of asphaltenes dissolved in toluene for concentrations varying from 0.002 to 20 kg/m(3). The effects of oscillation frequency, asphaltene concentration, and interface aging time were examined. The films exhibited viscoelastic behavior. The total modulus increased as the interface aged at all asphaltene concentrations. An attempt was made to model the rheology for the full range of asphaltene concentration. The instantaneous elasticity was modeled with a surface equation of state (SEOS), and the elastic and viscous moduli, with the Lucassen-van den Tempel (LVDT) model. It was found that only the early-time data could be modeled using the SEOS-LVDT approach; that is, the instantaneous, elastic, and viscous moduli of interfaces aged for at most 10 minutes. At longer interface aging times, the SEOS-LVDT approach was invalid, likely because of irreversible adsorption of asphaltenes on the interface and the formation of a network structure. PMID:16316096

  15. Attractions between charged colloids at water interfaces

    OpenAIRE

    Oettel, M.; Dominguez, A; Dietrich, S.

    2005-01-01

    The effective potential between charged colloids trapped at water interfaces is analyzed. It consists of a repulsive electrostatic and an attractive capillary part which asymptotically both show dipole--like behavior. For sufficiently large colloid charges, the capillary attraction dominates at large separations. The total effective potential exhibits a minimum at intermediate separations if the Debye screening length of water and the colloid radius are of comparable size.

  16. 水库水气界面温室气体通量监测方法综述%Review of methods for measuring greenhouse gas flux from the air-water interface of reservoirs

    Institute of Scientific and Technical Information of China (English)

    赵炎; 曾源; 吴炳方; 陈永柏; 王强; 袁超

    2011-01-01

    Carbon dioxide (CO2) and methane ( CH4 ) produced during decomposition of organic matter (OM) in reservoirs are emitted from the air-water interface either by diffusion or ebullition.The static-chamber, gradient descent, invert funnel, TDLAS (Tunable Diode Laser Absorption Spectroscopy) and eddy covariance are commonly used methods for measuring CO2 and CH4 fluxes from the air-water interface of reservoirs in abroad.In this study, we review the principle and application of above mentioned methods, their pros and cons, as well as applicability limitations.Factors affecting the emission of greenhouse gases from reservoirs are analyzed from the perspective of water,terrestrial and climatic environment.Prospects of the application of remote sensing technologies for monitoring greenhouse gas emissions from reservoirs are presented.Using remote sensing technologies and surface measuring methods can be complementary to each other in both time and space.Our study provides a valuable reference for monitoring greenhouse gas emissions from reservoirs in China.%水库水体中的有机碳,经过水中微生物代谢分解,生成甲烷、二氧化碳等温室气体,通过扩散、气泡等方式,经由水气界面排向大气.目前国外对水库水气界面的温室气体通量监测已经发展了静态箱法、梯度法、倒置漏斗法、TDLAS法以及涡度相关法等.综述了以上监测方法的原理、应用、优缺点及适用范围,从水体、陆地和气候环境方面分析了影响水气界面温室气体排放通量的因素,展望了遥感技术在水库温室气体通量监测中的应用前景,通过遥感技术与水面监测相结合,实现两者的时空互补.对国外开展水库温室气体通量监测的方法进行综述,可为国内水库开展相关监测提供参考.

  17. The apparent charge of nanoparticles trapped at a water interface.

    Science.gov (United States)

    Bossa, Guilherme Volpe; Roth, Joseph; Bohinc, Klemen; May, Sylvio

    2016-05-14

    Charged spherical nanoparticles trapped at the interface between water and air or water and oil exhibit repulsive electrostatic forces that contain a long-ranged dipolar and a short-ranged exponentially decaying component. The former are induced by the unscreened electrostatic field through the non-polar low-permittivity medium, and the latter result from the overlap of the diffuse ion clouds that form in the aqueous phase close to the nanoparticles. The magnitude of the long-ranged dipolar interaction is largely determined by the residual charges that remain attached to the air- (or oil-) exposed region of the nanoparticle. In the present work we address the question to what extent the charges on the water-immersed part of the nanoparticle provide an additional contribution to the dipolar interaction. To this end, we model the electrostatic properties of a spherical particle - a nanoparticle or a colloid - that partitions equatorially to the air-water interface, thereby employing nonlinear Poisson-Boltzmann theory in the aqueous solution and accounting for the propagation of the electric field through the interior of the particle. We demonstrate that the apparent charge density on the air-exposed region of the particle, which determines the dipole potential, is influenced by the electrostatic properties in the aqueous solution. We also show that this electrostatic coupling through the particle can be reproduced qualitatively by a simple analytic planar capacitor model. Our results help to rationalize the experimentally observed weak but non-vanishing salt dependence of the forces that stabilize ordered two-dimensional arrays of interface-trapped nanoparticles or colloids. PMID:27049110

  18. Specific Na+ and K+ Cation Effects on the Interfacial Water Molecules at the Air/Aqueous Salt Solution Interfaces Probed with Non-resonant Second Harmonic Generation (SHG)

    OpenAIRE

    Bian, Hong-tao; Feng, Ran-Ran; Guo, Yuan; Wang, Hong-fei

    2008-01-01

    Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data,the orientational parameter D value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six sal...

  19. TPPS和Gemini表面活性剂的复合膜及其手性的研究%Supramolecular Assembly and Chirality of a Complex Film between Achiral TPPS and a Gemini Surfactant at the Air/water Interface

    Institute of Scientific and Technical Information of China (English)

    张莉; 王金本; 刘鸣华

    2004-01-01

    研究了一种新的gemini表面活性剂(C 12H24-α,ω-(C12H25N+(CH3)2Br-)2,(简写为C12-C12-C12)和TPPS在气液界面上形成的复合膜及其手性.实验发现,单独C12-C12-C12不能在纯水表面形成稳定的单分子膜,但当亚相中存在TPPS时,可形成稳定的单分子膜.通过水平提拉法将复合膜转移到固体基板上,发现在适当的pH值条件下,TPPS可在复合膜中形成J-聚集体,并且发现,尽管Gemini表面活性剂和TPPS都是非手性的,TPPS的J-聚集体表现出强烈的Cotton效应.另外,gemini表面活性剂的两个正电荷中心对TPPS的J-聚集体的手性并不能表现出协同效应.%Supramolecular assembly and chirality between a novel gemini surfactant (C12H24-α, ω-(C12H25N + (CH3)2Br-)2,(abbreviated as C12-C12-C12) and TPPS (tetrakis(4-sulfonatophenyl) porphine) at the air/water interface were investigated. It was found that although the gemini surfactant itself could not form a stable monolayer at the air/water interface, when there existed TPPS in the subphase, a stable complex monolayer could be formed. The complex monolayer could be transferred onto solid substrate by a horizontal lifting method. At a certain pH value of the subphase, TPPS could form a J-aggregate. It was further found that the J-aggregate of TPPS showed a strong split Cotton effect in the transferred film although both the gemini surfactant and TPPS are achiral. Further investigation through AFM measurements revealed that the nanothread formed in the transferred film was responsible for the chirality of the multilayer film. In addition, the two positive charge center of the gemini surfactant did not necessarily play the cooperative role in inducing the chirality of TPPS J-aggregate.

  20. Specific Na+ and K+ Cation Effects on the Interfacial Water Molecules at the Air/Aqueous Salt Solution Interfaces Probed with Non-resonant Second Harmonic Generation (SHG)

    CERN Document Server

    Bian, Hong-tao; Guo, Yuan; Wang, Hong-fei

    2008-01-01

    Here we report the polarization dependent non-resonant second harmonic generation (SHG) measurement of the interfacial water molecules at the aqueous solution of the following salts: NaF, NaCl, NaBr, KF, KCl, and KBr. Through quantitative polarization analysis of the SHG data,the orientational parameter D value and the relative surface density of the interfacial water molecules at these aqueous solution surfaces were determined. From these results we found that addition of each of the six salts caused increase of the thickness of the interfacial water layer at the surfaces to a certain extent. Noticeably, both the cations and the anions contributed to the changes, and the abilities to increase the thickness of the interfacial water layer were in the following order: KBr > NaBr > KCl > NaCl ~ NaF > KF. Since these changes can not be factorized into individual anion and cation contributions, there are possible ion pairing or association effects, especially for the NaF case. We also found that the orientational ...

  1. The impact and bounce of air bubbles at a flat fluid interface.

    Science.gov (United States)

    Manica, Rogerio; Klaseboer, Evert; Chan, Derek Y C

    2016-04-01

    The rise and impact of bubbles at an initially flat but deformable liquid-air interface in ultraclean liquid systems are modelled by taking into account the buoyancy force, hydrodynamic drag, inertial added mass effect and drainage of the thin film between the bubble and the interface. The bubble-surface interaction is analyzed using lubrication theory that allows for both bubble and surface deformation under a balance of normal stresses and surface tension as well as the long-range nature of deformation along the interface. The quantitative result for collision and bounce is sensitive to the impact velocity of the rising bubble. This velocity is controlled by the combined effects of interfacial tension via the Young-Laplace equation and hydrodynamic stress on the surface, which determine the deformation of the bubble. The drag force that arises from the hydrodynamic stress in turn depends on the hydrodynamic boundary conditions on the bubble surface and its shape. These interrelated factors are accounted for in a consistent manner. The model can predict the rise velocity and shape of millimeter-size bubbles in ultra-clean water, in two silicone oils of different densities and viscosities and in ethanol without any adjustable parameters. The collision and bounce of such bubbles with a flat water/air, silicone oil/air and ethanol/air interface can then be predicted with excellent agreement when compared to experimental observations. PMID:26924623

  2. Cascades of popping bubbles along air/foam interfaces.

    Science.gov (United States)

    Vandewalle, N; Lentz, J F

    2001-08-01

    We report image analysis of popping bubbles during the collapsing of two-dimensional (2D) and 3D aqueous foams. Although temporal and spatial correlations between successive popping bubbles within avalanches are emphasized, the breaking of a soap film at the air/foam interface seems to be independent of (i) the topology, (ii) the local curvature, and (iii) the size of the popping bubble. Possible mechanisms for cascades of pops are proposed and discussed. PMID:11497589

  3. AirJump: Using Interfaces to Instantly Perform Simultaneous Extractions.

    Science.gov (United States)

    Berry, Scott M; Pezzi, Hannah M; LaVanway, Alex J; Guckenberger, David J; Anderson, Meghan A; Beebe, David J

    2016-06-22

    Analyte isolation is an important process that spans a range of biomedical disciplines, including diagnostics, research, and forensics. While downstream analytical techniques have advanced in terms of both capability and throughput, analyte isolation technology has lagged behind, increasingly becoming the bottleneck in these processes. Thus, there exists a need for simple, fast, and easy to integrate analyte separation protocols to alleviate this bottleneck. Recently, a new class of technologies has emerged that leverages the movement of paramagnetic particle (PMP)-bound analytes through phase barriers to achieve a high efficiency separation in a single or a few steps. Specifically, the passage of a PMP/analyte aggregate through a phase interface (aqueous/air in this case) acts to efficiently "exclude" unbound (contaminant) material from PMP-bound analytes with higher efficiency than traditional washing-based solid-phase extraction (SPE) protocols (i.e., bind, wash several times, elute). Here, we describe for the first time a new type of "exclusion-based" sample preparation, which we term "AirJump". Upon realizing that much of the contaminant carryover stems from interactions with the sample vessel surface (e.g., pipetting residue, wetting), we aim to eliminate the influence of that factor. Thus, AirJump isolates PMP-bound analyte by "jumping" analyte directly out of a free liquid/air interface. Through careful characterization, we have demonstrated the validity of AirJump isolation through comparison to traditional washing-based isolations. Additionally, we have confirmed the suitability of AirJump in three important independent biological isolations, including protein immunoprecipitation, viral RNA isolation, and cell culture gene expression analysis. Taken together, these data sets demonstrate that AirJump performs efficiently, with high analyte yield, high purity, no cross contamination, rapid time-to-isolation, and excellent reproducibility.

  4. Quantum chemical clarification of the alkyl chain length threshold of nonionic surfactants for monolayer formation at the air/water interface.

    Science.gov (United States)

    Vysotsky, Yu B; Kartashynska, E S; Belyaeva, E A; Vollhardt, D; Fainerman, V B; Miller, R

    2016-03-21

    A theoretical basis is provided for the experimental fact that for various surfactant classes the alkyl chain length threshold varies for the formation of condensed monolayers. The existence of the alkyl chain length threshold for a surfactant enabling the formation of monolayers is determined by the entropy increment to the Gibbs' energy, assessed by using the quantum chemical semiempiric method PM3. The value of the clusterization threshold is not stipulated by the surfactant solubility in water, rather by the electron-donor and electron-seeking properties of the head groups. These properties in turn impact the value of the solubility threshold for surfactants. The value of the clusterization threshold depends quadratically on the substituent constants, i.e. it is independent of whether the functional group is a donor or an acceptor of electrons. Rather it depends only on the donor or the acceptor 'force' of the substituent. The square-law dependence of the surface clusterization threshold of the amphiphile on the solubility threshold is evidenced. PMID:26957020

  5. Ordered supramolecular assembly of bis[3,4,12,13,21,22,30, 31-octa(dodecylthio)-2,3-naphthalocyaninato] erbium at the air/water interface

    Institute of Scientific and Technical Information of China (English)

    CHEN; Ya; nli

    2001-01-01

    -type (na)phthalocyaninato and porphyrinato rare earth complexes, Polyhedron, 2000, 19:1381.[12]Jiang. J.. Kasuga, K., Dennis, P. et al., Supramolecular Photosensitive and Electroactive Materials, New York: Academic Press. 2001. 113-210.[13]Van Nostrum. C. F., Nolte, R. J. M., Functional supramolecular material: self-assembly of phthalocyanines and porphyraszines. Chem. Commun., 1996: 2385.[14]Liu. Y., Shigehara, K., Yamada, A., Purification of lutetium diphthalocyanine and electrochromism of its Langmuir-Blodgett films, Thin Solid Films, 1989, 179: 303.[15]Liu. Y.. Shigehara, K., Hara, M. et al., Electrochemistry and electrochromic behavior of Langmuir-Blodgett films of octakis-substituted rare-earth metal diphthalocyanines, J. Am. Chem. Soc., 1991,113: 440.[16]Jones, R., Hunter, R. A., Davidson, K., Ordered Langmuir-Blodgett films of a substituted lutetium bisphthalocyanine, Thin Solid Films,1994, 250: 249.[17]Jones, R., Krier, A., Davidosn, K., Structure electrical conductivity and electrochromism in thin film of substituted and unsubstituted lanthanide bisphthalocyanines, Thin Solid Films, 1997, 298: 228.[18]Qian, D. -J., Liu, H. -G., Jiang, J., Monolayers and Langmuir-Blodgett films of (phthalocyaninato)(tetra-4-pyridylporphyrinato) cerium double-decker heteto complex, Colloids and Surfaces A, 2000,163:191.[19]Honig, E. P., Hengst, J. H. T., Engelsen, D. D., Langmuir-Blodgett deposition ratios, J. Colloid Interface Sci., 1973, 45:92.[20]Smolenyak, P., Peterson, R., Nesesny, K. et al., Highly ordered thin films of octasubstituted phthalocyanines, J. Am. Chem.Soc., 1999, 121: 8628.[21]Kasha, M., Rawls, H. R., E1-Bayoumi, M. A., The excition model in molecular spectroscopy, Pure Appl. Chem., 1965, 11: 371.[22]Fujiki, M., Tabei, H., Kurihara, T., Self-assembling features of soluble nickel phthalocyanines, J. Phys. Chem., 1988, 92:1281.[23]Osburn, E. J., Chau, L. -K., Chen, S. -Y. et al., Novel amphiphilic phthalocyanines

  6. Diurnal methane flux across water-air interface in summer in Nihe reservoir%泥河水库夏季水-气界面甲烷通量日变化研究

    Institute of Scientific and Technical Information of China (English)

    于洪贤; 慈雪伦; 黄璞祎

    2012-01-01

    为研究东北地区灌溉型水库的甲烷日排放特征,试验采用静态浮箱法于2008年7月测定了泥河水库水-气界面的甲烷通量.结果发现,泥河水库夏季甲烷平均排放通量为13.48 mg/(m2·h);夜间(21:00)甲烷排放最低,日间(5:00和9:00)最高.不同时刻的甲烷通量存在显著差异(P<0.05),21:00的甲烷排放通量显著低于5:00和9:00的甲烷通量.泥河水库出水口、库中心和进水口的甲烷通量差异不显著.相关分析表明,甲烷通量与总氮存在显著正相关(P<0.05),与气温、水温、水中总有机碳、水中溶解有机碳、总磷、水深、风速、溶氧等环境因子均未达到显著相关.%In order to study diurnal methane emission of irrigated reservoir in northeast China, Static floating chamber methods were used to measure methane flux across water-air interface in Nihe reservoir in July 2008. The results indicated that the mean methane flux of Nihe reservoir was 13.48 mg/(m2 · H) in summer; the lowest emission occurred at night (21:00) and the emission peak observed at day (5:00 and 9:00). There was significant difference between different time of day (P <0.05) and the methane flux at 21:00 was significantly lower than that of at 5 :00 and 9:00. There was no significant difference in outlet, center and outlet of reservoir. Correlation analysis showed that methane flux was positive relation significantly with total nitrogen (P <0.05 ) , and there were no significant relation with other environmental factors including air temperature, water temperature, total organic carbon , dissolved organic carbon, total phosphoric, water depth, wind speed and dissolved oxygen.

  7. Long term stability of immiscible ferrofluid/water interfaces

    Science.gov (United States)

    Malouin, Bernard; Posada, David; Hirsa, Amir

    2010-11-01

    Recently we have demonstrated pinned-contact, coupled droplet pairs of aqueous ferrofluids in air that can form electromagnetically-activated capillary switches and oscillators. The great variety of available ferrofluids, however, enables the use of immiscible oil-based ferrofluid droplets in a water environment to obtain the same behavior. Such immersed ferrofluid oscillators exhibit natural frequencies (for 5 mm devices) of about 10 Hz. Here we report on the observation of a gradual increase in the resonant frequency of the system in time. Experimental observations suggest that the drift in the natural frequency is a consequence of changes occurring at the ferrofluid/water interface. The interfacial structure of such a complex system (water, oil, surfactant, iron particles) is examined along with its evolution in time, using various microscopy techniques.

  8. Self-Organization of Polystyrene-b-polyacrylic Acid (PS-b-PAA) Monolayer at the Air/Water Interface: A Process Driven by the Release of the Solvent Spreading.

    Science.gov (United States)

    Guennouni, Zineb; Cousin, Fabrice; Fauré, Marie-Claude; Perrin, Patrick; Limagne, Denis; Konovalov, Oleg; Goldmann, Michel

    2016-03-01

    We present an in situ structural study of the surface behavior of PS-b-PAA monolayers at the air/water interface at pH 2, for which the PAA blocks are neutral and using N,N-dimethyformamide (DMF) as spreading solvent. The surface pressure versus molecular area isotherm shows a perfectly reversible pseudoplateau over several cycles of compression/decompression. The width of such plateau enlarges when increasing temperature, conversely to what is classically observed in the case of an in-plane first order transition. We combined specular neutron reflectivity (SNR) experiments with contrast variation to solve the profile of each block perpendicular to the surface with grazing-incidence small-angle scattering (GISAXS) measurements to determine the in-plane structure of the layer. SNR experiments showed that both PS and PAA blocks remain adsorbed on the surface for all surface pressure probed. A correlation peak at Q(xy)* = 0.021 Å(-1) is evidenced by GISAXS at very low surface pressure which intensity first increases on the plateau. When compressing further, its intensity decays while Q(xy)* is shifted toward low Q(xy). The peak fully disappears at the end of the plateau. These results are interpreted by the formation of surface aggregates induced by DMF molecules at the surface. These DMF molecules remain adsorbed within the PS core of the aggregates. Upon compression, they are progressively expelled from the monolayer, which gives rise to the pseudoplateau on the isotherm. The intensity of the GISAXS correlation peak is set by the amount of DMF within the monolayer as it vanishes when all DMF molecules are expelled. This result emphizes the role of the solvent in Langmuir monolayer formed by amphiphilic copolymers which hydrophobic and hydrophilic parts are composed by long polymer chains.

  9. Stereoselective synthesis of (2S,3S,4Z-4-fluoro-1,3-dihydroxy-2-(octadecanoylaminooctadec-4-ene, [(Z-4-fluoroceramide], and its phase behavior at the air/water interface

    Directory of Open Access Journals (Sweden)

    2008-04-01

    for natural ceramide.ConclusionsAsymmetric aldol reaction proved to be successful for the preparation of enantiopure 4-fluoroceramide. Surface/pressure isotherms and hysteresis curves of ceramide and its 4-fluoro derivative showed that the presence of fluorine leads to stronger intermolecular interactions between the hydrophobic chains of neighboring molecules, and therefore to increasing stability of the monolayer of 4-fluoroceramide at the air water interface.

  10. Crystalline architectures at the air-liquid interface: From nucleation to engineering

    DEFF Research Database (Denmark)

    Rapaport, H.; Kuzmenko, I.; Kjær, K.;

    1999-01-01

    Ordered molecular clusters with a length scale down to few nanometers are currently attracting wide attention in the physical and biological sciences. The design and preparation of functional materials such as thin-layered microstructures, reagent films for biosensors, and devices for optoelectro......Ordered molecular clusters with a length scale down to few nanometers are currently attracting wide attention in the physical and biological sciences. The design and preparation of functional materials such as thin-layered microstructures, reagent films for biosensors, and devices...... of molecular ordering at interfaces provides a means to probe the early stages of molecular assembly. One route involves the spontaneous formation, at the air-water interface, of crystalline films ranging from one to several layers thick, composed of water-insoluble molecules in pure form or complexed...... with water-soluble ions or molecules from the aqueous subphase. In this review much use is made of grazing incidence X-ray diffraction (GIXD) using synchrotron radiation that provides structural information at the subnanometer scale of crystalline films at the air-liquid interface [1,2]. The topics described...

  11. Patterns of a slow air-water flow in a semispherical container

    DEFF Research Database (Denmark)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.;

    2016-01-01

    This numerical study analyzes the development of eddies in a slow steady axisymmetric air-water flow in a sealed semispherical container, driven by a rotating top disk. As the water height, Hw, increases, new flow cells emerge in both water and air. First, an eddy emerges near the axis......-bottom intersection. Then this eddy expands and reaches the interface, inducing a new cell in the air flow. This cell appears as a thin near-axis layer which then expands and occupies the entire air domain. As the disk rotation intensifies at Hw = 0.8, the new air cell shrinks to the axis and disappears. The bulk...... water circulation becomes separated from the interface by a thin layer of water counter-circulation. These changes in the flow topology occur due to (a) competing effects of the air meridional flow and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow...

  12. Improving the indoor air quality using water

    International Nuclear Information System (INIS)

    The article briefly describes the principle of a Danish air cleaning device called the Aqua-Wall. This is a clear acrylic wall with filters and pump and liquid that ripples down the vertical wall. The liquid is cleaned water to which is added harmless chemicals that prevent bacteria and algal growth. By means of this falling water and a patent that makes the water bind microorganisms and dust particles the system cleans the air and creates a natural air humidity

  13. The effect of the nasopharyngeal air cavity on x-ray interface doses

    Energy Technology Data Exchange (ETDEWEB)

    Kan, W.K. [Hong Kong Polytechnic University, Department of Optometry and Radiography, Hung Hom, Kowloon (Hong Kong); Hong Kong Baptist Hospital, 222 Waterloo Road, Kowloon (Hong Kong); Wu, P.M.; Leung, H.T.; Lo, T.C.; Chung, C.W.; Kwong, D.L.W.; Sham, S.T. [Queen Mary Hospital, Department of Radiotherapy (Hong Kong)

    1998-03-01

    We investigated the impact of air cavities in head and neck cancer patients treated by photon beams based on clinical set-ups. The phantom for investigation was constructed with a cubic air cavity of 4x4x4cm{sup 3} located at the centre of a 30x30x16cm{sup 3} solid water slab. The cavity cube was used to resemble an extreme case for the nasal cavity. Apart from measuring the dose profiles and central axis percentage depth dose distribution, the dose values in 0.25x0.25x0.25cm{sup 3} voxels at regions around the air cavity were obtained by Monte Carlo simulations. A mean dose value was taken over the voxels of interest at each depth for evaluation. Single-field results were added to study parallel opposed field effects. For 10x10cm{sup 2} parallel opposed fields at 4, 6 and 8 MV, the mean dose at regions near the lateral interfaces of the cavity cube were decreased by 1 to 2% due to the lack of lateral scatter, while the mean dose near the proximal and distal interfaces was increased by 2 to 4% due to the greater transmission through air. Secondary build-up effects at points immediately beyond the air cavity cube are negligible using field sizes greater than 4x4cm{sup 2}. For most head and neck treatment, the field sizes are usually 6x6cm{sup 2} or greater, and most cavity volumes are smaller than our chosen dimensions. Therefore, the influence of closed air cavities on photon interface doses is not significant in clinical treatment set-ups. (author)

  14. ELECTROHYDRODYNAMIC ENHANCED TRANSPORT AND TRAPPING OF AIRBORNE PARTICLES TO A MICROFLUIDIC AIR-LIQUID INTERFACE

    OpenAIRE

    Sandström, Niklas; Frisk, Thomas; Stemme, Göran; van der Wijngaart, Wouter

    2008-01-01

    We introduce a novel approach for greatly improved transport and trapping of airborne sample to a microfluidic analysis system by integrating an electrohydrodynamic (EHD) air pump with a microfluidic air-liquid interface. In our system, a negative corona discharge partially ionizes the air around a sharp electrode tip while the electrostatic field accelerates airborne particles towards an electrically grounded liquid surface, where they absorb. The air-liquid interface is fixated at the micro...

  15. Environmental Chemistry: Air and Water Pollution.

    Science.gov (United States)

    Stoker, H. Stephen; Seager, Spencer L.

    This is a book about air and water pollution whose chapters cover the topics of air pollution--general considerations, carbon monoxide, oxides of nitrogen, hydrocarbons and photochemical oxidants, sulfur oxides, particulates, temperature inversions and the greenhouse effect; and water pollution--general considerations, mercury, lead, detergents,…

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

    Science.gov (United States)

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

    2016-03-01

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

  17. Study of the iron corrosion at the interface of different media (water, air) submitted to protons irradiation; Etude de la corrosion du fer a l'interface de differents milieux (eau, air) soumis a l'irradiation de protons

    Energy Technology Data Exchange (ETDEWEB)

    Lapuerta, S

    2005-10-15

    During the deep geological disposal, stainless steel containers of the vitrified waste will be put in carbon steel overpacks. After the closing of the storage site, overpacks will be in contact with a humid air and a radioactive medium. After hundred years, overpacks could be in contact with water radiolysis in an anoxic medium. In this context, my PhD work is a fundamental study which is the understanding of the corrosion mechanisms of pure iron under proton irradiation. This corrosion is affected by the contact of iron with different atmospheres (air, nitrogen) and water. In the case of the atmospheric iron corrosion under irradiation, we have studied the influence of the proton beam flux. During this work, we have characterized the structure of the oxides formed at the iron surface. The structure formed does not correspond to iron oxides and hydroxides indexed. However, we have shown that the oxide structure is close to that of lepidocrocite and bernalite. Moreover, we have determined the oxygen diffusion coefficient in iron under irradiation and we have shown that the irradiation accelerates of 6 orders of magnitude the iron corrosion. In addition, the irradiations which were realized in different gas have put in evidence the negligible role of nitrates, and the importance of the O{sub 2}/H{sub 2}O coupling on the iron corrosion. Finally, we have shown the influence of the relative humidity, the maximum of the corrosion being observed for a relative humidity close to 45%. In the case of the iron corrosion in aqueous media under irradiation, the influence of the oxygen dissolved in water has been studied using a surface marker. We have put in evidence that the corrosion is twice more significant in aerated medium than in deaerated medium. Moreover, the influence of radicals has been shown. An irradiated sample is more corroded than a sample put in contact with a H{sub 2}O{sub 2} solution. Finally, the follow-up of the iron potential under irradiation have shown

  18. Ellipsoidal Janus Nanoparticles Assembled at Spherical Oil/Water Interfaces

    OpenAIRE

    Luu, X-C; Striolo, A.

    2014-01-01

    The equilibrium behavior of ellipsoidal Janus nanoparticles adsorbed at spherical oil/water interfaces was investigated using dissipative particle dynamics simulations. Several phenomena were documented that were not observed on similar simulations for planar oil/water interfaces. The nanoparticles were found to yield isotropic, radial nematic phases, and axial nematic domains, depending on the nanoparticle characteristics (aspect ratio and surface chemistry), particle density at the interfac...

  19. The production of drops by the bursting of a bubble at an air liquid interface

    Science.gov (United States)

    Darrozes, J. S.; Ligneul, P.

    1982-01-01

    The fundamental mechanism arising during the bursting of a bubble at an air-liquid interface is described. A single bubble was followed from an arbitrary depth in the liquid, up to the creation and motion of the film and jet drops. Several phenomena were involved and their relative order of magnitude was compared in order to point out the dimensionless parameters which govern each step of the motion. High-speed cinematography is employed. The characteristic bubble radius which separates the creation of jet drops from cap bursting without jet drops is expressed mathematically. The corresponding numerical value for water is 3 mm and agrees with experimental observations.

  20. 表面活性素单分子膜在空气/水界面的迟滞现象%Hysteresis Behavior of Surfactin Monolayer at the Air/Water Interface

    Institute of Scientific and Technical Information of China (English)

    杨莹; 宋昌盛; 叶汝强; 牟伯中

    2011-01-01

    Surfactin,one of the most surface-active microbial lipopeptides,can readily form an insoluble monolayer at the air/water interface.Consecutive compression-expansion cycles of surfactin with a β-hydroxyl fatty acid chain consisting of 14 carbon atoms were studied by a Langmuir film balance.A larger hysteresis loop was observed when the compression isotherm reached a plateau compared with that expanded at a lower surface pressure (20 mN· m-1).The 2nd cycle was shifted towards smaller molecular areas compared with the 1st cycle.We also studied the hysteresis cycles of the surfactin monolayer on subphase of different pH values.With a decrease in the subphase pH the hysteresis loop became smaller and the expansion isotherm curve underwent a longer pseudo plateau.Furthermore,the morphologies of the surfactin monolayers in the plateau region,which were transferred onto a mica surface,were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM).Both AFM and SEM images gave three-dimensional surface aggregates with heights ranging from tens to hundreds of nanometers.The above results suggest that the formation of three-dimensional surface aggregates at the plateau region induces a large hysteresis loop in the surfactin monolayer,which can also be attributed to the submergence of molecules into the subphase when the peptide loop in the surfactin molecule is ionized.%表面活性素是一类具有较强表面活性的微生物脂肽类化合物,能在空气/水界面形成不溶性单分子膜.利用Langmuir膜天平测定了表面活性素单分子膜的压缩-扩张循环曲线,发现单分子膜在经历了“平台区”后出现较大的迟滞环,迟滞环的形状与亚相pH有关.将“平台区”的单分子膜转移到云母表面后,用原子力显微镜(AFM)和扫描电子显微镜(SEM)均观察到高度达几十至数百纳米的表面聚集体,说明表面活性素在单分子膜的“平台区”伴随着自聚集.研究结果

  1. Nitrous oxide supersaturation at the liquid/air interface of animal waste

    International Nuclear Information System (INIS)

    Concentrated animal feeding operations around the globe generate large amounts of nitrous oxide (N2O) in the surrounding atmosphere. Liquid animal waste systems have received little attention with respect to N2O emissions. We hypothesized that the solution chemistry of animal waste aqueous suspensions would promote conditions that lead to N2O supersaturation at the liquid/air interface. The concentration of dissolved N2O in poultry litter (PL) aqueous suspensions at 25 deg. C was 0.36 μg N2O mL-1, at least an order of magnitude greater than that measured in water in equilibrium with ambient air, suggesting N2O supersaturation. There was a nonlinear increase in the N2O Henry constants of PL from 2810 atm/mole fraction at 35 deg. C to 17 300 atm/mole fraction at 41 deg. C. The extremely high N2O Henry constants were partially ascribed to N2O complexation with aromatic moieties. Complexed N2O structures were unstable at temperatures > 35 deg. C, supplying the headspace with additional free N2O concentrations. - Temperature-dependent N2O supersaturation at the liquid/air interface of animal waste.

  2. Deposition and retention of air pollutants on vegetation and other atmospheric interfaces

    International Nuclear Information System (INIS)

    The question of the deposition of aerosols and gases are applied to biological and ecological problems concerning the filtering aspect of atmospheric interfaces, especially vegetation, with respect to air pollution, and also the resulting pollutant effect. In order to determine the deposition of aerosols, numerous field experiments were carried out. The deposition of gases was treated on the basis of current literature data. The experiments indicate that the deposition of aerosols on grass largely depends on aerosol diameter, dry weight per unit area and the wind velocity or turbulence of the air layer near the ground. Of the interfaces studied, namely soil without vegetation, water, filter paper, smooth and structured metals, grass, clover and trees, the latter had the greatest dust collecting capability. It is recommended that in the afforestation of areas in the close proximity of industrial regions the common beech, silver birch and Japanese larch should be taken into particular consideration due to their great deposition effectiveness with respect to dusts and their comparatively high resistance to pollutant gases. Silver birch and moreover red horse chestnut should be considered for filtering the air in urban regions because of the high aerosol deposition. (orig./HP)

  3. Cleaning verification by air/water impingement

    Science.gov (United States)

    Jones, Lisa L.; Littlefield, Maria D.; Melton, Gregory S.; Caimi, Raoul E. B.; Thaxton, Eric A.

    1995-01-01

    This paper will discuss how the Kennedy Space Center intends to perform precision cleaning verification by Air/Water Impingement in lieu of chlorofluorocarbon-113 gravimetric nonvolatile residue analysis (NVR). Test results will be given that demonstrate the effectiveness of the Air/Water system. A brief discussion of the Total Carbon method via the use of a high temperature combustion analyzer will also be given. The necessary equipment for impingement will be shown along with other possible applications of this technology.

  4. Theoretical study on wettability of graphene/water interface

    Science.gov (United States)

    Ishimoto, Takayoshi

    2015-12-01

    We analyzed the interaction energy between water clusters and graphene model compound by using density functional theory. The mono- and multi-layer interaction of water on graphene models are regarded as the low and high contact angles, which correspond to the wettability of interface, respectively. We clearly found the size dependency of water molecules on graphene model compound for the wettability.

  5. The Influence of Air Cavity on Interface Doses for Photon Beams

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Bum; Kwon, Young Ho; Chung, Se Young [Dept. of Radiation Oncology, Korea University Hospital, Seoul (Korea, Republic of); Kim, You Hyun [Dept. of Radiologic Technology, Junior College of Allied Health Sciences Korea University, Seoul (Korea, Republic of)

    1998-11-15

    When a high energy photon beam is used to treat lesions located in the upper respiratory air passages or in maxillary sinus, the beams often must traverse an air cavity before it reaches the lesion. Because of this traversal of air, it is not clear that the surface layers of the lesion forming the air-tumor tissue interface will be in a state of near electronic equilibrium; if they are not, underdosing of these layers could result. Although dose corrections at large distances beyond an air cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. This problem has been investigated for 4 MV and 10 MV X-ray beams which are becoming widely available for radiotherapy with linear accelerator. Markus chamber was used for measurement with various air cavity geometries in X-ray beams. Underdosing effects occur at both the distal and proximal air cavity interface. The magnitude depended on geometry, energy, field sizes and distance from the air-tissue interfaces. As the cavity thickness increased, the central axis dose at the distal interface decreased. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Following a 20 x 2 x 2 cm{sup 3} air cavity, 4 x 4 cm field there was an 11.5% and 13% underdose at the distal interface, while a 20 x 20 x 2 cm{sup 3} air cavity yield a 24% and 29% loss for the 4 MV and 10 MV beams, respectively. The losses were slightly larger for the 10 MV beams. The measurements reported here can be used to guide the development of new calculation models under non-equilibrium conditions. This situation is of clinical concern when lesions such as larynx and maxillary carcinoma beyond air cavities are irradiated.

  6. Graphical User Interface Development for Representing Air Flow Patterns

    Science.gov (United States)

    Chaudhary, Nilika

    2004-01-01

    In the Turbine Branch, scientists carry out experimental and computational work to advance the efficiency and diminish the noise production of jet engine turbines. One way to do this is by decreasing the heat that the turbine blades receive. Most of the experimental work is carried out by taking a single turbine blade and analyzing the air flow patterns around it, because this data indicates the sections of the turbine blade that are getting too hot. Since the cost of doing turbine blade air flow experiments is very high, researchers try to do computational work that fits the experimental data. The goal of computational fluid dynamics is for scientists to find a numerical way to predict the complex flow patterns around different turbine blades without physically having to perform tests or costly experiments. When visualizing flow patterns, scientists need a way to represent the flow conditions around a turbine blade. A researcher will assign specific zones that surround the turbine blade. In a two-dimensional view, the zones are usually quadrilaterals. The next step is to assign boundary conditions which define how the flow enters or exits one side of a zone. way of setting up computational zones and grids, visualizing flow patterns, and storing all the flow conditions in a file on the computer for future computation. Such a program is necessary because the only method for creating flow pattern graphs is by hand, which is tedious and time-consuming. By using a computer program to create the zones and grids, the graph would be faster to make and easier to edit. Basically, the user would run a program that is an editable graph. The user could click and drag with the mouse to form various zones and grids, then edit the locations of these grids, add flow and boundary conditions, and finally save the graph for future use and analysis. My goal this summer is to create a graphical user interface (GUI) that incorporates all of these elements. I am writing the program in

  7. Dynamics of charged microparticles at oil-water interfaces.

    Science.gov (United States)

    Wu, Chih-Yuan; Tarimala, Sowmitri; Dai, Lenore L

    2006-02-28

    Solid-stabilized emulsions have been used as a model system to investigate the dynamics of charged microparticles with diameters of 1.1 microm at oil-water interfaces. Using confocal microscopy, we investigated the influences of interfacial curvature, cluster size, and temperature on the diffusion of solid particles. Our work suggests that a highly curved emulsion interface slows the motion of solid particles. This qualitatively supports the theoretical work by Danov et al. (Danov, K. D.; Dimova, R.; Pouligny, B. Phys. Fluids 2000, 12, 2711); however, the interfacial curvature effect decreases with increasing oil-phase viscosity. The diffusion of multiparticle clusters at oil-water interfaces is a strong function of cluster size and oil-phase viscosity and can be quantitatively related to fractal dimension. Finally, we report the influence of temperature and quantify the diffusion activation energy and friction factor of the particles at the investigated oil-water interfaces.

  8. Molecular dynamics study of the water/n-alkane interface

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Molecular dynamics simulations on the interface between liquid water and liquid n-alkane (including octane, nonane, decane, undecane and dodecane) have been performed with the purpose to study the interfacial properties: (Ⅰ) density profile; (Ⅱ) molecular orientation; (Ⅲ) interfacial tension and the temperature effect on the interfacial tension. Simulation results show that at the interface the structures of both water and n-alkane are different from those in the bulk. Water has an orientational preference due to the number of hydrogen bonds per molecule maximized. N-alkane has a more lateral orientation with respect to the interface in order to be in close contact with water. The calculated individual phase bulk density and interfacial tension of water/n-alkane systems are in good agreement with the corresponding experimental ones.

  9. Effects of air polishing on the resin composite-dentin interface.

    Science.gov (United States)

    Shimizu, Yutaka; Tada, Kazuhiro; Seki, Hideaki; Kakuta, Kiyoshi; Miyagawa, Yukio; Shen, Jie-Fei; Morozumi, Yuko; Kamoi, Hisahiro; Sato, Soh

    2014-07-01

    The aim of this study was to examine defect depths and volumes at the resin composite-dentin (R/D) interface after air polishing with different particles and spray angles. Samples were 54 dentin specimens that were formed in saucer-shaped cavities filled with resin composite. Each specimen was air polished with either sodium bicarbonate (NaHCO3) or one of two glycine (Gly) powders. The air polisher was set at angles of 90° to the interface and at 45° to the interface from both the dentin and resin composite sides. Air polishing with Gly powder produced defects with less depth and volume than NaHCO3 powder (p resin composite side produced fewer defects (p resin composite side produced fewer defects to the interface because the hardness of the resin composite was higher than that of dentin.

  10. Novel method for Ag colloidal cluster formation by laser ablation at the air-liquid interface

    Science.gov (United States)

    Nishi, Teppei; Akimoto, Yusuke; Takahashi, Naoko; Kitazumi, Kosuke; Kajiya, Shuji; Watanabe, Yoshihide

    2015-09-01

    We report a novel method for formation of sub-nanoclusters by laser ablation at the air-liquid interface. The density of plasma induced by laser ablation at the air-liquid interface should be lower than that produced by laser ablation in liquid. In the lower density plasma, the produced clusters rarely grow or aggregate into larger clusters because the collision probability is low, resulting in the formation of small clusters. Ag sub-nanoclusters were observed by electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). These results show that low-density plasma can be applied to small-cluster formation and that laser ablation at the air-liquid interface produces a good reactive field for the formation of sub-nanoclusters. Our results highlight the importance of low-density plasma induced at the air-liquid interface for sub-nanocluster formation.

  11. Cavity-water interface is polar

    OpenAIRE

    Friesen, Allan D.; Matyushov, Dmitry V.

    2010-01-01

    We present the results of numerical simulations of the electrostatics and dynamics of water hydration shells surrounding Kihara cavities given by a Lennard-Jones (LJ) layer at the surface of a hard-sphere cavity. The local dielectric response of the hydration layer substantially exceeds that of bulk water, with the magnitude of the dielectric constant peak in the shell increasing with the growing cavity size. The polar shell propagates into bulk water to approximately the cavity radius. The s...

  12. Injection of Helium 3 and SF{sub 6} in a lake for the determination of gaseous exchange rates at the water-air interface: implementation, analysis and experimental results; Injection d`helium-3 et SF{sub 6} en lac pour la determination des coefficients gazeux a l`interface eau-air: deploiement, analyse et resultats experimentaux

    Energy Technology Data Exchange (ETDEWEB)

    Poisson, A. [Paris-6 Univ., 75 (France); Jean-Baptiste, P. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Sciences de la Matiere

    1994-12-31

    In order to study the hypothesis of an under-rating of the exchange velocity at the ocean-atmosphere interface that could explain the lack of CO{sub 2} in the global CO{sub 2} balance, an experiment was carried out in two lakes at the Kerguelen Islands where strong winds are common, in order to evaluate precisely the relation between the transfer coefficient and the wind velocity: {sup 3}He and SF{sub 6} tracers were injected in the lakes; concentration evolutions were recorded and results are shown to validate the above assumption. 6 figs., 1 tab., 9 refs.

  13. Development of a Bench-Top Air-to-Water Heat Pump Experimental Apparatus

    OpenAIRE

    H. I. Abu-Mulaweh

    2009-01-01

    A bench-top air-to-water heat pump experimental apparatus was designed,developed, and constructed for instructional and demonstrative purposes. Thisair-to-water heat pump experimental apparatus is capable of demonstratingthermodynamics and heat transfer concepts and principles. This heat pumpexperimental setup was designed around the vapor compression refrigerationcycle. This experimental apparatus has an intuitive user interface, reliable, safefor student use, and portable. The interface is ...

  14. AIRS total precipitable water over high latitudes

    Science.gov (United States)

    Ye, H.; Fetzer, E. J.; Bromwich, D. H.; Fishbein, E.; Olsen, E. T.; Granger, S.; Lee, S.; Lambrigtsen, B.; Chen, L.

    2006-12-01

    Given the importance of atmospheric conditions over the Arctic and Antarctica to the global climate system, hydrological cycles, and cryopspheric dynamics, and the poor coverage of traditional data over these region, AIRS data will play a significant role in filling the information gaps. In this study, we examine the quality of AIRS total atmospheric precipitable water (PWV) and explore its potential applications over the Antarctica and Arctic. For Antarctica, both Level II matching files and Level III gridded products of AIRS are compared with radiosonde records at Dome C and ECMWF's analysis products during December 10, 2003 to January 26, 2004. Results will testify to the quality of AIRS moisture data over glacial surfaces. For the Arctic region, AIRS level III data are used to compare with AMSR-E data and ECMWF analysis product during September of 2004. Results will reveal the quality of AIRS data over high-latitude water, sea ice, and land surfaces. The potential of AIRS data to improve model simulation will be discussed.

  15. Interfacial nanobubbles are leaky: permeability of the gas/water interface.

    Science.gov (United States)

    German, Sean R; Wu, Xi; An, Hongjie; Craig, Vincent S J; Mega, Tony L; Zhang, Xuehua

    2014-06-24

    Currently there is no widespread agreement on an explanation for the stability of surface nanobubbles. One means by which several explanations can be differentiated is through the predictions they make about the degree of permeability of the gas-solution interface. Here we test the hypothesis that the gas-solution interface of surface nanobubbles is permeable by experimental measurements of the exchange of carbon dioxide. We present measurements by attenuated total reflection Fourier transform infrared (ATR-FTIR) and atomic force microscopy (AFM), demonstrating that the gas inside surface nanobubbles is not sealed inside the bubbles, but rather exchanges with the dissolved gas in the liquid phase. Such gas transfer is measurable by using the infrared active gas CO2. We find that bubbles formed in air-saturated water that is then perfused with CO2-saturated water give rise to distinctive gaseous CO2 signals in ATR-FTIR measurements. Also the CO2 gas inside nanobubbles quickly dissolves into the surrounding air-saturated water. AFM images before and after fluid exchange show that CO2 bubbles shrink upon exposure to air-equilibrated liquid but remain stable for hours. Also air bubbles in contact with CO2-saturated water increase in size and Ostwald ripening occurs more rapidly due to the relatively high gas solubility of CO2 in water. PMID:24863586

  16. Temporal variability of CO₂ fluxes at the sediment-air interface in mangroves (New Caledonia).

    Science.gov (United States)

    Leopold, Audrey; Marchand, Cyril; Deborde, Jonathan; Allenbach, Michel

    2015-01-01

    Carbon budgets in mangrove forests are uncertain mainly due to the lack of data concerning carbon export in dissolved and gaseous forms. Temporal variability of in situ CO2 fluxes was investigated at the sediment-air interface in different seasons in different mangrove stands in a semi-arid climate. Fluxes were measured using dynamic closed incubation chambers (transparent and opaque) connected to an infra-red gas analyzer. Microclimatic conditions and chl-a contents of surface sediments were determined. Over all mangrove stands, CO2 fluxes on intact sediments were relatively low, ranging from -3.93 to 8.85 mmolCO₂·m(-2)·h(-1) in the light and in the dark, respectively. Changes in the fluxes over time appeared to depend to a great extent on the development of the biofilm at the sediment surface. We suggest that in intact sediments and in the dark, CO2 fluxes measured at the sediment-air interface rather reflect the metabolism of benthic organisms than sediment respiration (heterotrophic and autotrophic). However, without the biofilm, sediment water content and air temperature were main drivers of seasonal differences in CO2 fluxes, and their influence differed depending on the intertidal location of the stand. After removal of the biofilm, Q10 values in the Avicennia and the Rhizophora stands were 1.84 and 2.1, respectively, revealing the sensitivity of mangrove sediments to an increase in temperature. This study provides evidence that, if the influence of the biofilm is not taken into account, the in situ CO2 emission data currently used to calculate the budget will lead to underestimation of CO2 production linked to heterotrophic respiration fueled by organic matter detritus from the mangrove. PMID:25302449

  17. Penguin vision in air and water.

    Science.gov (United States)

    Howland, H C; Sivak, J G

    1984-01-01

    Refractive states measured by retinoscopy and photorefraction indicate that rockhopper (Eudyptes crestatus), Magellanic (Spheniscus magellanicus) and gentoo (Pygoscelis papua) penguins are approximately emmetropic in air and water. Extensive myopia in air, as predicted by early authors, is nonexistent. Photorefractive measurements of refractive state in water indicate that rockhopper, gentoo, Magellanic and king (Aptenodytes patagonica) penguins can accommodate sufficiently to make up for the loss of refractive power of the cornea. Corneas of rockhopper and Megellanic penguins are flattened relative to the overall size of the eye. This feature minimizes the optical effect of submergence. PMID:6534014

  18. Water Intercalation for Seamless, Electrically Insulating, and Thermally Transparent Interfaces.

    Science.gov (United States)

    Wang, Yanlei; Xu, Zhiping

    2016-01-27

    The interface between functional nanostructures and host substrates is of pivotal importance in the design of their nanoelectronic applications because it conveys energy and information between the device and environment. We report here an interface-engineering approach to establish a seamless, electrically insulating, while thermally transparent interface between graphene and metal substrates by introducing water intercalation. Molecular dynamics simulations and first-principles calculations are performed to demonstrate this concept of design, showing that the presence of the interfacial water layer helps to unfold wrinkles formed in the graphene membrane, insulate the electronic coupling between graphene and the substrate, and elevate the interfacial thermal conductance. The findings here lay the ground for a new class of nanoelectronic setups through interface engineering, which could lead to significant improvement in the performance of nanodevices, such as the field-effect transistors. PMID:26720217

  19. INFLUENCE OF FILLING WATER ON AIR CONCENTRATION

    Institute of Scientific and Technical Information of China (English)

    WU Jian-hua; MA Fei; DAI Hui-chao

    2011-01-01

    The filling water inside the cavity below an aerator occurs for the flow of low Froude number or the small bottom slope of a spillway.The aerator may cease to protect against cavitation damages,and may even act as a generator of cavitation if it is fully filled by water.The experiments were conducted to investigate the influences of the geometric parameters,and then the filling water on the air concentration.The results show that the filling water,or the net cavity length,is closely related to the plunging jet length for a given aerator,and the air concentration at some section is proportional to the ratio Ln/Lj at a fixed Lj for different geometric parameters of aerators.Secondly,at the same ratio of Ln / Lj,the aerator with a larger height or a larger angle of ramp,or a larger bottom slope,would have a larger plunging jet length,and then a larger net cavity length based on the ratio of Ln / Lj.As a result,the large space of cavity,or the high air concentration of the flow could be obtained although the filling water increases also based on the fact that Lf=Lj- Ln.It is the space of the cavity that is the dominant factor to affect the air concentration of the flow.

  20. Acid-base chemistry of frustrated water at protein interfaces.

    Science.gov (United States)

    Fernández, Ariel

    2016-01-01

    Water molecules at a protein interface are often frustrated in hydrogen-bonding opportunities due to subnanoscale confinement. As shown, this condition makes them behave as a general base that may titrate side-chain ammonium and guanidinium cations. Frustration-based chemistry is captured by a quantum mechanical treatment of proton transference and shown to remove same-charge uncompensated anticontacts at the interface found in the crystallographic record and in other spectroscopic information on the aqueous interface. Such observations are untenable within classical arguments, as hydronium is a stronger acid than ammonium or guanidinium. Frustration enables a directed Grotthuss mechanism for proton transference stabilizing same-charge anticontacts.

  1. Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures

    DEFF Research Database (Denmark)

    Zambrano, H.A.; Walther, Jens Honore; Jaffe, R.L.

    2014-01-01

    on the system. Our simulations reveal the presence of a nanometer thick layer of gas at the water–silica interface. We believe that this gas layer could promote nucleation and stabilization of surface nanobubbles at amorphous silica surfaces. © 2014 Elsevier B.V. All rights reserved.......Wepresent a force field forMolecular Dynamics (MD) simulations ofwater and air in contactwith an amorphous silica surface. We calibrate the interactions of each species present in the systemusing dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility...... of air in water at different pressures. Using the calibrated force field, we conduct MD simulations to study the interface between a hydrophilic silica substrate and water surrounded by air at different pressures. We find that the static water contact angle is independent of the air pressure imposed...

  2. Combined air and water pollution control system

    Science.gov (United States)

    Wolverton, Billy C. (Inventor); Jarrell, Lamont (Inventor)

    1990-01-01

    A bioaquatic air pollution control system for controlling both water and atmospheric pollution is disclosed. The pollution control system includes an exhaust for directing polluted gases out of a furnace and a fluid circulating system which circulates fluid, such as waste water, from a source, past the furnace where the fluid flow entrains the pollutants from the furnace. The combined fluid and pollutants are then directed through a rock/plant/microbial filtering system. A suction pump pumps the treated waste water from the filter system past the exhaust to again entrain more pollutants from the furnace where they are combined with the fluid (waste water) and directed to the filter system.

  3. Unitary water-to-air heat pumps

    Energy Technology Data Exchange (ETDEWEB)

    Christian, J.E.

    1977-10-01

    Performance and cost functions for nine unitary water-to-air heat pumps ranging in nominal size from /sup 1///sub 2/ to 26 tons are presented in mathematical form for easy use in heat pump computer simulations. COPs at nominal water source temperature of 60/sup 0/F range from 2.5 to 3.4 during the heating cycle; during the cooling cycle EERs range from 8.33 to 9.09 with 85/sup 0/F entering water source temperatures. The COP and EER values do not include water source pumping power or any energy requirements associated with a central heat source and heat rejection equipment.

  4. The Role of Wind Waves in Dynamics of the Air-Sea Interface

    CERN Document Server

    Polnikov, Vladislav G

    2010-01-01

    Wind waves are considered as an intermediate small-scale dynamic process at the air-sea interface,which modulates radically middle-scale dynamic processes of the boundary layers in water and air. It is shown that with the aim of a quantitative description of the impact said, one can use the numerical wind wave models which are added with the blocks of the dynamic atmosphere boundary layer (DABL) and the dynamic water upper layer (DWUL). A mathematical formalization for the problem of energy and momentum transfer from the wind to the upper ocean is given on the basis of the well known mathematical representations for mechanisms of a wind wave spectrum evolution. The problem is solved quantitatively by means of introducing special system parameters: the relative rate of the wave energy input, IRE, and the relative rate of the wave energy dissipation, DRE. For two simple wave-origin situations, the certain estimations for values of IRE and DRE are found, and the examples of calculating an impact of a wind sea on...

  5. SPECIATION OF HEAVY METALS AT WATER-SEDIMENT INTERFACE

    OpenAIRE

    Chiara Ferronato; Livia Vittori Antisari; Monica Marianna Modesto; Gilmo Vianello

    2013-01-01

    The objective of the study was to understand the equilibrium relationship between the heavy metals concentrations in superficial water and pore water. At  water-sediment interface, the equilibrium rapidly changed and it is influenced by chemico-physical parameters of aquatic ecosystems. The hydraulic safety of Bologna plain (North Italy) depends on network of artificial canals and they are related with natural rivers of Reno basin (Reno river and its tributaries). The natural and artificial w...

  6. Assembly of transmembrane proteins on oil-water interfaces

    Science.gov (United States)

    Yunker, Peter; Landry, Corey; Chong, Shaorong; Weitz, David

    2015-03-01

    Transmembrane proteins are difficult to handle by aqueous solution-based biochemical and biophysical approaches, due to the hydrophobicity of transmembrane helices. Detergents can solubilize transmembrane proteins; however, surfactant coated transmembrane proteins are not always functional, and purifying detergent coated proteins in a micellar solution can be difficult. Motivated by this problem, we study the self-assembly of transmembrane proteins on oil-water interfaces. We found that the large water-oil interface of oil drops prevents nascent transmembrane proteins from forming non-functional aggregates. The oil provides a hydrophobic environment for the transmembrane helix, allowing the ectodomain to fold into its natural structure and orientation. Further, modifying the strength or valency of hydrophobic interactions between transmembrane proteins results in the self-assembly of spatially clustered, active proteins on the oil-water interface. Thus, hydrophobic interactions can facilitate, rather than inhibit, the assembly of transmembrane proteins.

  7. Ethylene-air detonation in water spray

    Science.gov (United States)

    Jarsalé, G.; Virot, F.; Chinnayya, A.

    2016-07-01

    Detonation experiments are conducted in a 52 mm square channel with an ethylene-air gaseous mixture with dispersed liquid water droplets. The tests were conducted with a fuel-air equivalence ratio ranging from 0.9 to 1.1 at atmospheric pressure. An ultrasonic atomizer generates a polydisperse liquid water spray with droplet diameters of 8.5-12 μm, yielding an effective density of 100-120 g/m3 . Pressure signals from seven transducers and cellular structure are recorded for each test. The detonation structure in the two-phase mixture exhibits a gaseous-like behaviour. The pressure profile in the expansion fan is not affected by the addition of water. A small detonation velocity deficit of up to 5 % was measured. However, the investigation highlights a dramatic increase in the cell size (λ ) associated with the increase in the liquid water mass fraction in the two-phase mixture. The detonation structure evolves from a multi-cell to a half-cell mode. The analysis of the decay of the post-shock pressure fluctuations reveals that the ratio of the hydrodynamic thickness over the cell size (x_{{HT}}/{λ } ) remains quite constant, between 5 and 7. A slight decrease of this ratio is observed as the liquid water mass fraction is increased, or the ethylene-air mixture is made leaner.

  8. Ethylene-air detonation in water spray

    Science.gov (United States)

    Jarsalé, G.; Virot, F.; Chinnayya, A.

    2016-09-01

    Detonation experiments are conducted in a 52 {mm} square channel with an ethylene-air gaseous mixture with dispersed liquid water droplets. The tests were conducted with a fuel-air equivalence ratio ranging from 0.9 to 1.1 at atmospheric pressure. An ultrasonic atomizer generates a polydisperse liquid water spray with droplet diameters of 8.5-12 μm, yielding an effective density of 100-120 g/m3. Pressure signals from seven transducers and cellular structure are recorded for each test. The detonation structure in the two-phase mixture exhibits a gaseous-like behaviour. The pressure profile in the expansion fan is not affected by the addition of water. A small detonation velocity deficit of up to 5 % was measured. However, the investigation highlights a dramatic increase in the cell size (λ ) associated with the increase in the liquid water mass fraction in the two-phase mixture. The detonation structure evolves from a multi-cell to a half-cell mode. The analysis of the decay of the post-shock pressure fluctuations reveals that the ratio of the hydrodynamic thickness over the cell size (x_{{HT}}/{λ }) remains quite constant, between 5 and 7. A slight decrease of this ratio is observed as the liquid water mass fraction is increased, or the ethylene-air mixture is made leaner.

  9. interfaces

    Directory of Open Access Journals (Sweden)

    Dipayan Sanyal

    2005-01-01

    macroscopic conservation equations with an order parameter which can account for the solid, liquid, and the mushy zones with the help of a phase function defined on the basis of the liquid fraction, the Gibbs relation, and the phase diagram with local approximations. Using the above formalism for alloy solidification, the width of the diffuse interface (mushy zone was computed rather accurately for iron-carbon and ammonium chloride-water binary alloys and validated against experimental data from literature.

  10. Melittin at a membrane/water interface: Effects on water orientation and water penetration

    Science.gov (United States)

    Bachar, Michal; Becker, Oren M.

    1999-11-01

    Melittin, a small peptide found in bee venom, is known to induce membrane lysis. A molecular dynamics simulation of melittin embedded in a hydrated dipalmitoylphosphatidylcholine bilayer is analyzed in order to study the peptide's effect on water molecules at the membrane/water interface. The peptide, with a protonated N-terminus, was embedded in a trans-bilayer orientation. The simulation highlights the microscopic mechanism by which melittin induces the formation of transmembrane water "pores," leading to membrane lysis. It was found that melittin has a profound effect on the behavior of the water molecules at the membrane/water interface. It modifies the orientation of the water dipoles and induces water penetration into the bilayer. In fact, melittin's residue Lys-7 and its protonated N-terminus facilitate the formation of transmembrane water pores by steering water penetration from both sides of the bilayer. The initial step towards pore formation takes about 200 ps, and the process relays on melittin's bent conformation and tilted orientation. A large body of experimental observations supports the simulation results and the suggested microscopic mechanism.

  11. Nitrous oxide supersaturation at the liquid/air interface of animal waste.

    Science.gov (United States)

    Makris, Konstantinos C; Andra, Syam S; Hardy, Michael; Sarkar, Dibyendu; Datta, Rupali; Bach, Stephan B H; Mullens, Conor P

    2009-12-01

    Concentrated animal feeding operations around the globe generate large amounts of nitrous oxide (N(2)O) in the surrounding atmosphere. Liquid animal waste systems have received little attention with respect to N(2)O emissions. We hypothesized that the solution chemistry of animal waste aqueous suspensions would promote conditions that lead to N(2)O supersaturation at the liquid/air interface. The concentration of dissolved N(2)O in poultry litter (PL) aqueous suspensions at 25 degrees C was 0.36 microg N(2)O mL(-1), at least an order of magnitude greater than that measured in water in equilibrium with ambient air, suggesting N(2)O supersaturation. There was a nonlinear increase in the N(2)O Henry constants of PL from 2810 atm/mole fraction at 35 degrees C to 17 300 atm/mole fraction at 41 degrees C. The extremely high N(2)O Henry constants were partially ascribed to N(2)O complexation with aromatic moieties. Complexed N(2)O structures were unstable at temperatures > 35 degrees C, supplying the headspace with additional free N(2)O concentrations. PMID:19573962

  12. The critical crossover at the n-hexane-water interface

    International Nuclear Information System (INIS)

    According to estimates of the parameters of the critical crossover in monolayers of long-chain alcohol molecules adsorbed at the n-hexane-water interface, all systems in which this phenomenon is observed are characterized by the same value of the critical exponent ν ∼ 1.8.

  13. Local order of liquid water at the electrochemical interface

    CERN Document Server

    Pedroza, Luana S; Fernández-Serra, M -V

    2014-01-01

    We study the structure and dynamics of liquid water in contact with Pd and Au (111) surfaces using \\emph{ab initio} molecular dynamics simulations with and without van der Waals interactions. Our results show that the structure of water at the interface of these two metals is very different. For Pd, we observe the formation of two different domains of preferred orientations, with opposite net interfacial dipoles. One of these two domains has a large degree of in-plane hexagonal order. For Au a single domain exists with no in-plane order. For both metals, the structure of liquid water at the interface is strongly dependent on the use of dispersion forces. The origin of the structural domains observed in Pd is associated to the interplay between water/water and water/metal interactions. This effect is strongly dependent on the charge transfer that occurs at the interface, and which is not modeled by current state of the art semi-empirical force fields.

  14. Conjugated polymelectrolyte assembly at water-oil interfaces

    Science.gov (United States)

    Liu, Feng; Huang, Caili; Thomas, Russell; Russell Team

    Conjugated polyelectrolytes featured with conjugated backbone and functional side chains are interesting optoelectronic materials and widely used to modify electrodes in electronic devices such as light emitting diodes and solar cells to enhance device performance. Conjugated polyelectrolyte can be designed to have alternating hydrophilic and hydrophobic side chains, and thus inducing interesting surface and interface properties. In this work, we using polyfluorene based material, to study its behavior at water-toluene interface. The aliphatic side-chains will favorably interact with toluene, and amine side-chains will interact with water, making this material a good surfactant. At interface the polymer chain is stretched to a Janus type of geometry. Flattened molecules will assemble into ultra thin films via pi-pi intermolecular stacking, and thus creating barriers between liquids. When liquid volume is reduced, jamming at interface will show up. These properties are strongly affected by the environment of the liquids, such as temperature and PH values, and polyelectrolyte diffusion to interfaces. This study leads to new methods to structure liquids using single component, which can be extended to applications such as electro-spinning or fabricate flow devices.

  15. User interface for ground-water modeling: Arcview extension

    Science.gov (United States)

    Tsou, M.-S.; Whittemore, D.O.

    2001-01-01

    Numerical simulation for ground-water modeling often involves handling large input and output data sets. A geographic information system (GIS) provides an integrated platform to manage, analyze, and display disparate data and can greatly facilitate modeling efforts in data compilation, model calibration, and display of model parameters and results. Furthermore, GIS can be used to generate information for decision making through spatial overlay and processing of model results. Arc View is the most widely used Windows-based GIS software that provides a robust user-friendly interface to facilitate data handling and display. An extension is an add-on program to Arc View that provides additional specialized functions. An Arc View interface for the ground-water flow and transport models MODFLOW and MT3D was built as an extension for facilitating modeling. The extension includes preprocessing of spatially distributed (point, line, and polygon) data for model input and postprocessing of model output. An object database is used for linking user dialogs and model input files. The Arc View interface utilizes the capabilities of the 3D Analyst extension. Models can be automatically calibrated through the Arc View interface by external linking to such programs as PEST. The efficient pre- and postprocessing capabilities and calibration link were demonstrated for ground-water modeling in southwest Kansas.

  16. A theoretical remark about waves on a static water surface beneath a layer of moving air

    Science.gov (United States)

    Kida, T.; Hayashi, R.; Yasutomi, Z.

    1990-12-01

    Grundy and Tuck (1987) treat the problem of large-amplitude waves on an air-water interface where the air is a steady nonuniform flow and the water is stationary. Both periodic nonlinear Stokes-like waves far downstream and a configuration of the water surface from the edge region of a hovercraft were computed. However, there is no work that treats the existence of such Stokes-like waves theoretically. The present work aims to prove the existence of such solutions in the case where the cushion pressure is low, that is, the depression at the upstream stagnation point from the mean water level is small.

  17. Protein denaturation by combined effect of shear and air-liquid interface.

    Science.gov (United States)

    Maa, Y F; Hsu, C C

    1997-06-20

    The effect of shear alone on the aggregation of recombinant human growth hormone (rhGH) and recombinant human deoxyribonuclease (rhDNase) has been found to be insignificant. This study focused on the synergetic effect of shear and gas-liquid interface on these two model proteins. Two shearing systems, the concentric-cylinder shear device (CCSD) and the rotor/stator homogenizer, were used to generate high shear (> 10(6)) in aqueous solutions in the presence of air. High shear in the presence of an air-liquid interface had no major effect on rhDNase but caused rhGH to form noncovalent aggregates. rhGH aggregation was induced by the air-liquid interface and was found to increase with increasing protein concentration and the air-liquid interfacial area. The aggregation was irreversible and exhibited a first-order kinetics with respect to the protein concentration and air-liquid interfacial area. Shear and shear rate enhanced the interaction because of its continuous generation of new air-liquid interfaces. In the presence of a surfactant, aggregation could be delayed or prevented depending upon the type and the concentration of the surfactant. The effect of air-liquid interface on proteins at low shear was examined using a nitrogen bubbling method. We found that foaming is very detrimental to rhGH even though the shear involved is low. The use of anti-foaming materials could prevent rhGH aggregation during bubbling. The superior stability exhibited by rhDNase may be linked to the higher surface tension and lower foaming tendency of its aqueous solution. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 503-512, 1997. PMID:18636406

  18. Simulation study of water/silicon oxide interface

    Science.gov (United States)

    Lorenz, Christian; Rempe, Susan; Stevens, Mark; Grest, Gary; Tsige, Mesfin

    2006-03-01

    The interaction of water with solid surfaces plays a crucial role in many phenomena. The water-silica interface is one of the typical systems encountered in technological and natural materials. Numerous technological applications of silica were found to rely on its specific surface properties. Large scale quantum mechanics (QM) and classical molecular dynamics (MD) simulations are used to study the molecular configurations and wetting properties of water at the interface of different silicon oxide surfaces. In order to understand how the surface coverage of silanols (-SiOH) affects the wetting behavior of the silica surfaces, both crystalline ((001) α-quartz (coverage 9.6 nm-2) and (100) β-cristobalite (7.8 nm-2)) and amorphous silica (5.0 nm-2) substrates have been studied. The binding energy of the water, the number of water molecules hydrogen-bonded to the surface and the configuration of the hydrogen-bonded water molecules are determined as a function of silanol coverage from QM simulations. The number of water molecules within a monolayer and the orientation of the water molecules within the monolayer and in the bulk are determined from MD simulations. Results from two classical force fields are compared to one another and to the relevant quantities from the QM simulations. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Oriented crystalline monolayers and bilayers of 2 x 2 silver(1) grid architectures at the air-solution interface: Their assembly and crystal structure elucidation

    DEFF Research Database (Denmark)

    Weissbuch, J.; Baxter, P.N.W.; Kuzmenko, I.;

    2000-01-01

    Oriented crystalline monolayers, similar to 14 Angstrom thick, of a 2 x 2 Ag+ grid complex, self-assembled at the air-solution interface starting from an water-insoluble ligand 3,6-bis[2-(6-phenylpyridine)]pyridazine spread on silver-ion-containing solutions,were examined by grazing-incidence X...

  20. Adsorption of diatoms at the oil-water interface

    Science.gov (United States)

    Fathollahi, Niloofar; Sheng, Jian

    2013-11-01

    Statistically robust experimental observations on 3D trajectory of diatoms approaching an oil-water interface is crucial for understanding sorption mechanisms of active particles, and interfacial rheology with over-arching implications in interfacial dynamics, droplet break and coalescence. Digital Holographic Cinematography is utilized to measure 3-D trajectories of diatoms, Thalassiosira pseudomona and T. weissflogii and simultaneously track the interface. Experiments are conducted in a 300 × 100 × 100 mm chamber containing 32 ppt artificial seawater. A stationary pendant drop is created on the tip of a needle located at the center of the chamber. Three oil samples, Louisiana crude, hexadecane, and mineral oil, are used. Diatoms are injected at a height above the drop with a negligible velocity, where Diatom precipitates freely on its excess weight. Holograms of diatom and drop are recorded at 5 fps with a magnification of 1.3X and are streamed in real time allowing for long-term study of sorption onto a slowly aging interface. A novel autofocus algorithm enables us to determine 3D locations within an uncertainty of 0.05 particle diameter. This allows us to perform super-resolution measurement to determine the effects of location and orientation of diatoms on the adsorption rate at the oil-water interface. Funded by GoMRI.

  1. Design and Implementation of a Single-Frequency Mesh Network Using OpenAirInterface

    Directory of Open Access Journals (Sweden)

    Kaltenberger Florian

    2010-01-01

    Full Text Available OpenAirInterface is an experimental open-source real-time hardware and software platform for experimentation in wireless communications and signal processing. With the help of OpenAirInterface, researchers can demonstrate novel ideas quickly and verify them in a realistic environment. Its current implementation provides a full open-source software modem comprising physical and link layer functionalities for cellular and mesh network topologies. The physical (PHY layer of the platform targets fourth generation wireless networks and thus uses orthogonal frequency division multiple access (OFDMA together with multiple-input multiple-output (MIMO techniques. The current hardware supports 5 MHz bandwidth and two transmit/receive antennas. The media access (MAC layer of the platform supports an abundant two-way signaling for enabling collaboration, scheduling protocols, as well as traffic and channel measurements. In this paper, we focus on the mesh topology and show how to implement a single-frequency mesh network with OpenAirInterface. The key ingredients to enable such a network are a dual-stream MIMO receiver structure and a distributed network synchronization algorithm. We show how to implement these two algorithms in real-time on the OpenAirInterface platform. Further more, we provide results from field trials and compare them to the simulation results.

  2. Toward a Reconfigurable MIMO Downlink Air Interface and Radio Resource Management

    DEFF Research Database (Denmark)

    Kovacs, Istvan Zsolt; Luis, Garcia Ordonez; Ferrández, Miguel Navarro;

    2010-01-01

    This article presents a reconfigurable multiple-input multiple-output air interface design combined with radio resource management algorithms applicable to multi-user MIMO transmission in downlink orthogonal frequency-division multiple access systems. A low-complexity, adaptive, and channel...... communication systems....

  3. FLOW CURVES OF AN ADSORBED PROTEIN LAYER AT THE SALIVA-AIR INTERFACE

    NARCIS (Netherlands)

    HOLTERMAN, HJ; SGRAVENMADE, EJ; WATERMAN, HA; BLOM, C; Mellema, J.

    1990-01-01

    At the air-liquid interface of human saliva a protein layer is absorbed. An apparatus is described with which a flow curve of this layer was measured. In the majority of samples the viscosity of the surface layer changed gradually and could be described by a power-law dependence on the shear rate. T

  4. An exploratory study of the human-machine interface for controlling Maritime Unmanned Air Vehicles

    NARCIS (Netherlands)

    Breda, L. van

    1995-01-01

    Under contract by the Royal Netherlands Navy an exploratory study was conducted on the design of the user interface for Maritime Unmanned Air Vehicles (MUAVs) control. The goal of this study was to gain more insight into the various parameters that may influence system performance, given the present

  5. Biopolymers form a gelatinous microlayer at the air-sea interface when Arctic sea ice melts.

    Science.gov (United States)

    Galgani, Luisa; Piontek, Judith; Engel, Anja

    2016-07-20

    The interface layer between ocean and atmosphere is only a couple of micrometers thick but plays a critical role in climate relevant processes, including the air-sea exchange of gas and heat and the emission of primary organic aerosols (POA). Recent findings suggest that low-level cloud formation above the Arctic Ocean may be linked to organic polymers produced by marine microorganisms. Sea ice harbors high amounts of polymeric substances that are produced by cells growing within the sea-ice brine. Here, we report from a research cruise to the central Arctic Ocean in 2012. Our study shows that microbial polymers accumulate at the air-sea interface when the sea ice melts. Proteinaceous compounds represented the major fraction of polymers supporting the formation of a gelatinous interface microlayer and providing a hitherto unrecognized potential source of marine POA. Our study indicates a novel link between sea ice-ocean and atmosphere that may be sensitive to climate change.

  6. Biopolymers form a gelatinous microlayer at the air-sea interface when Arctic sea ice melts

    Science.gov (United States)

    Galgani, Luisa; Piontek, Judith; Engel, Anja

    2016-07-01

    The interface layer between ocean and atmosphere is only a couple of micrometers thick but plays a critical role in climate relevant processes, including the air-sea exchange of gas and heat and the emission of primary organic aerosols (POA). Recent findings suggest that low-level cloud formation above the Arctic Ocean may be linked to organic polymers produced by marine microorganisms. Sea ice harbors high amounts of polymeric substances that are produced by cells growing within the sea-ice brine. Here, we report from a research cruise to the central Arctic Ocean in 2012. Our study shows that microbial polymers accumulate at the air-sea interface when the sea ice melts. Proteinaceous compounds represented the major fraction of polymers supporting the formation of a gelatinous interface microlayer and providing a hitherto unrecognized potential source of marine POA. Our study indicates a novel link between sea ice-ocean and atmosphere that may be sensitive to climate change.

  7. SPECIATION OF HEAVY METALS AT WATER-SEDIMENT INTERFACE

    Directory of Open Access Journals (Sweden)

    Chiara Ferronato

    2013-09-01

    Full Text Available The objective of the study was to understand the equilibrium relationship between the heavy metals concentrations in superficial water and pore water. At  water-sediment interface, the equilibrium rapidly changed and it is influenced by chemico-physical parameters of aquatic ecosystems. The hydraulic safety of Bologna plain (North Italy depends on network of artificial canals and they are related with natural rivers of Reno basin (Reno river and its tributaries. The natural and artificial water courses flowed in agricultural, urban and industrial land. The heavy metals concentration in water and sediment discriminated the human pressure on the land and their spatial distribution in sediment could predict the hazard of pollution in aquatic ecosystems. We compared the heavy metals concentrations in pore water and superficial water determined in natural rivers and artificial canals, and more pollution in artificial canals than natural rivers was found. Furthermore, the coefficient of partition (log Kd between water and sediments was calculated to evaluate the bioavailability of heavy metals adsorbed on the sediments. The heavy metals extracted in deionised water at equilibrium after 16 h showed higher concentrations than those determined directly on water samples.

  8. Photodetoxification and purification of water and air

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, M. [Univ. of Wisconsin, Madison, WI (United States); Blake, D.M. [National Renewable Energy Lab., Golden, CO (United States)

    1996-09-01

    The scope of interest in this section is basic research in photochemistry that can remove barriers to the development of photochemical technologies for the removal of hazardous chemicals from contaminated air or water (photodetoxification). Photochemistry is be broadly interpreted to include direct photochemistry, indirect photochemistry (sensitized and photocatalytic), photochemistry of species adsorbed on inert surfaces, and complementary effects of high energy radiation photons and particles. These may occur in either homogeneous or heterogeneous media. The photon source may span the range from ionizing radiation to the near infrared.

  9. Air-water transfer of hydrogen sulfide

    DEFF Research Database (Denmark)

    Yongsiri, C.; Vollertsen, J.; Rasmussen, M. R.;

    2004-01-01

    The emissions process of hydrogen sulfide was studied to quantify air–water transfer of hydrogen sulfide in sewer networks. Hydrogen sulfide transfer across the air–water interface was investigated at different turbulence levels (expressed in terms of the Froude number) and pH using batch...... experiments. By means of the overall mass–transfer coefficient (KLa), the transfer coefficient of hydrogen sulfide (KLaH2S), referring to total sulfide, was correlated to that of oxygen (KLaO2) (i.e., the reaeration coefficient). Results demonstrate that both turbulence and pH in the water phase play...... a significant role for KLaH2S. An exponential expression is a suitable representation for the relationship between KLaH2S and the Froude number at all pH values studied (4.5 to 8.0). Because of the dissociation of hydrogen sulfide, KLaH2S increased with decreasing pH at a constant turbulence level. Relative...

  10. Adhesive interfaces of enamel and dentin prepared by air-abrasion at different distances

    International Nuclear Information System (INIS)

    The purpose of this study was to analyse, by scanning electron microscopy (SEM), the morphology of enamel and dentin/adhesive interfaces in cavities prepared by air-abrasion at different working distances. Thirty sound third human molars were selected and, on both their buccal and lingual surfaces, class V cavities were prepared by air-abrasion, at 2-, 4-, 6-, 8- and 10-mm working distances, or high-speed bur (control group). After preparation, all cavities were etched with 35% phosphoric acid gel and restored with Single Bond/Filtek Z-250. Buccal and lingual surfaces were separated and restorations sectioned in a buccolingual direction, providing two sections of each cavity, which were analysed by scanning electron microscopy. It was observed that the distances of 6 and 8 mm promoted more homogeneous dentin/adhesive interfaces, with tags formation, and more uniform for enamel, which were similar to the control group. It may be concluded that the air-abrasion working distance can influence the morphology of enamel and dentin/adhesive interfaces, and the intermediate distances provided better adhesive interfaces

  11. Ion Transfer Voltammetry Associated with Two Polarizable Interfaces Within Water and Moderately Hydrophobic Ionic Liquid Systems

    DEFF Research Database (Denmark)

    Gan, Shiyu; Zhou, Min; Zhang, Jingdong;

    2013-01-01

    An electrochemical system composed of two polarizable interfaces (the metallic electrode|water and water|ionic liquid interfaces), namely two‐polarized‐interface (TPI) technique, has been proposed to explore the ion transfer processes between water and moderately hydrophobic ionic liquids (W|mIL)...

  12. Computational study of effect of water finger on ion transport through water-oil interface

    Science.gov (United States)

    Kikkawa, Nobuaki; Wang, Lingjian; Morita, Akihiro

    2016-07-01

    When an ion transports from water to oil through water-oil interface, it accompanies hydrated water molecules and transiently forms a chain of water, called "water finger." We thoroughly investigated the role of the water finger in chloride ion transport through water-dichloromethane interface by using molecular dynamics technique. We developed a proper coordinate w to describe the water finger structure and calculated the free energy landscape and the friction for the ion transport as a function of ion position z and the water finger coordinate w. It is clearly shown that the formation and break of water finger accompanies an activation barrier for the ion transport, which has been overlooked in the conventional free energy curve along the ion position z. The present analysis of the friction does not support the hypothesis of augmented local friction (reduced local diffusion coefficient) at the interface. These results mean that the experimentally observed rate constants of interfacial ion transfer are reduced from the diffusion-limited one because of the activation barrier associated to the water finger, not the anomalous local diffusion. We also found that the nascent ion just after the break of water finger has excessive hydration water than that in the oil phase.

  13. Evanescent-wave dynamic light scattering at an oil-water interface: Diffusion of interface-adsorbed colloids

    OpenAIRE

    STOCCO, Antonio; Mokhtari, Tahereh; Haseloff, Günter; Erbe, Andreas; Sigel, Reinhard

    2011-01-01

    A light-scattering goniometer for evanescent-wave dynamic light scattering (EWDLS) measurements at a liquid-fluid interface is introduced, and used for measurements on two charge-stabilized polystyrene colloid systems adsorbed to alkane-water interfaces. The goniometer allows an independent variation of the penetration depth and the scattering vector components parallel and perpendicular to a liquid-fluid interface. The possible illumination geometries are compared. Ellipsometry at the liquid...

  14. Water at an electrochemical interface - a simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Willard, Adam; Reed, Stewart; Madden, Paul; Chandler, David

    2008-08-22

    The results of molecular dynamics simulations of the properties of water in an aqueous ionic solution close to an interface with a model metallic electrode are described. In the simulations the electrode behaves as an ideally polarizable hydrophilic metal, supporting image charge interactions with charged species, and it is maintained at a constant electrical potential with respect to the solution so that the model is a textbook representation of an electrochemical interface through which no current is passing. We show how water is strongly attracted to and ordered at the electrode surface. This ordering is different to the structure that might be imagined from continuum models of electrode interfaces. Further, this ordering significantly affects the probability of ions reaching the surface. We describe the concomitant motion and configurations of the water and ions as functions of the electrode potential, and we analyze the length scales over which ionic atmospheres fluctuate. The statistics of these fluctuations depend upon surface structure and ionic strength. The fluctuations are large, sufficiently so that the mean ionic atmosphere is a poor descriptor of the aqueous environment near a metal surface. The importance of this finding for a description of electrochemical reactions is examined by calculating, directly from the simulation, Marcus free energy profiles for transfer of charge between the electrode and a redox species in the solution and comparing the results with the predictions of continuum theories. Significant departures from the electrochemical textbook descriptions of the phenomenon are found and their physical origins are characterized from the atomistic perspective of the simulations.

  15. Food-Growing, Air- And Water-Cleaning Module

    Science.gov (United States)

    Sauer, R. L.; Scheld, H. W.; Mafnuson, J. W.

    1988-01-01

    Apparatus produces fresh vegetables and removes pollutants from air. Hydroponic apparatus performs dual function of growing fresh vegetables and purifying air and water. Leafy vegetables rooted in granular growth medium grow in light of fluorescent lamps. Air flowing over leaves supplies carbon dioxide and receives fresh oxygen from them. Adaptable to production of food and cleaning of air and water in closed environments as in underwater research stations and submarines.

  16. Electromagnetic Resonances of a Straight Wire on an Earth-Air Interface

    OpenAIRE

    Myers, John M.; Sandler, Sheldon S.; Wu, Tai Tsun

    2011-01-01

    Using a variational method, we recently determined an electromagnetic “signature” for characterizing a straight wire in free space. The signature consists of the first five resonant frequencies and their widths, more compactly expressed as the first five complex-valued resonant frequencies. Here we apply the variational method to the much more complicated case of determining the same signature for a straight wire or wire pair on a flat interface between a homogeneous earth and air. To calcula...

  17. Conformational transitions of cytochrome c in sub-micron-sized capsules at air/buffer interface.

    Science.gov (United States)

    Jaganathan, Maheshkumar; Dhathathreyan, Aruna

    2014-09-30

    This work presents the design of sub-micron-sized capsules of Cytochrome c (cyt c) in the range 300-350 nm and the conformational transitions of the protein that occur when the films of these capsules spread at the air/buffer interface are subjected to repeated compression-expansion cycles. Steady state fluorescence, time-resolved fluorescence, and circular dichroic (CD) spectra have been used to study the highly compact native conformation (70% helicity) of the protein in the capsules and its stability has been analyzed using cyclic voltammetry. The capsules have been characterized using zeta sizer and high resolution transmission electron microscopy (HRTEM). Surface concentration-surface pressure (Γ-π) isotherms of the films of the capsules spread at air/buffer interface following compression-expansion show destabilizing effect on cyt c. FTIR and CD spectra of these films skimmed from the surface show that the protein transitions gradually from its native helical to an anomalous beta sheet aggregated state. This results from a competition between stabilizing hydrated polar segments of the protein in the capsule and destabilizing nonspecific hydrophobic interactions arising at the air/buffer interface. This 2D model could further our understanding of the spatial and temporal roles of proteins in confined spaces and also in the design of new drug delivery vehicles using proteins.

  18. Air quality in natural areas: Interface between the public, science and regulation

    International Nuclear Information System (INIS)

    Natural areas are important interfaces between air quality, the public, science and regulation. In the United States and Canada, national parks received over 315 million visits during 2004. Many natural areas have been experiencing decreased visibility, increased ozone (O3) levels and elevated nitrogen deposition. Ozone is the most pervasive air pollutant in North American natural areas. There is an extensive scientific literature on O3 exposure-tree response in chambered environments and, lately, free-air exposure systems. Yet, less is known about O3 impacts on natural terrestrial ecosystems. To advance scientifically defensible O3 risk assessment for natural forest areas, species-level measurement endpoints must be socially, economically and ecologically relevant. Exposure-based indices, based on appropriate final endpoints, present an underused opportunity to meet this need. Exposure-plant indices should have a high degree of statistical significance, have high goodness of fit, be biologically plausible and include confidence intervals to define uncertainty. They must be supported by exposure-response functions and be easy to use within an air quality regulation context. Ozone exposure-response indices developed within an ambient air context have great potential for improving risk assessment in natural forest areas and enhancing scientific literacy. - Appropriate endpoints and exposure-response indices can improve assessment of air pollutant risk to forests in natural areas

  19. Dynamic Surface Properties of Asphaltenes and Resins at the Oil-Air Interface.

    Science.gov (United States)

    Bauget, Fabrice; Langevin, Dominique; Lenormand, Roland

    2001-07-15

    Because of the existence of large reserves, the production of heavy oils is presently the object of much interest. Some heavy oil reservoirs show anomalous behavior in primary production, with rates of production better than predicted. In Canada and Venezuela some heavy oils are produced in the form of "bubbly" oil, which is stable for several hours in open vessels. These crude oils are therefore commonly called "foamy oils". Since the presence of bubbles could be responsible for an enhanced rate of production, a better knowledge of the properties of the gas-oil interface is desirable. We have experimentally studied the effect of concentration of asphaltenes and resins on static and dynamic properties of oil-air interfaces and also on bulk viscosity. The experiments include surface tension measurements using the pendant-drop method, surface viscosity by the oscillating-drop method, foamability by continuous gas injection, and film lifetime. All the experiments were performed using resins and asphaltenes in toluene solutions at 20 degrees C. At first asphaltenes enhance foamability and film lifetime. All the experiments performed showed a change in regime for asphaltene concentrations around 10% by weight, possibly due to clustering. At the studied concentrations, the adsorption process at the air-oil interface is not diffusion controlled but rather involves a reorganization of asphaltene molecules in a network structure. The formation of a solid skin is well identified by the increase of the elastic modulus. This elastic modulus is also an important property for foam stability, since a rigid interface limits bubble rupture. The interface rigidity at long times decreases with increases in resin fraction, which could decrease foam stability as well as emulsion stability. Copyright 2001 Academic Press. PMID:11427016

  20. High resolution microprofiling, fractionation and speciation at sediment water interfaces

    Science.gov (United States)

    Fabricius, Anne-Lena; Duester, Lars; Ecker, Dennis; Ternes, Thomas A.

    2016-04-01

    Within aquatic environments, the exchange between the sediment and the overlaying water is often driven by steep gradients of, e.g., the oxygen concentration, the redox potential or the pH value at the sediment water interface (SWI). Important transport processes at the SWI are sedimentation and resuspension of particulate matter and diffusional fluxes of dissolved substances. To gain a better understanding of the key factors and processes determining the fate of substances at the SWI, methods with a spatial high resolution are required that enable the investigation of several sediment parameters in parallel to different analytes of interest in the sediment pore water. Moreover, beside the total content, questions concerning the speciation and fractionation are of concern in studying the different (transport) processes. Due to the availability of numerous micro-sensors and -electrodes (e.g., O2, redox potential, pH value, H2S, N2O) and the development of methods for pore water sampling [1], the toolbox to study the heterogeneous and often dynamic conditions at the SWI at a sub-millimetre scale were considerably improved. Nevertheless, the methods available for pore water sampling often require the installation of the sampling devices at the sampling site and/or intensive preparation procedures that may influence the conditions at the area studied and/or the characteristics of the samples taken. By combination of a micro profiling system with a new micro filtration probe head connected to a pump and a fraction collector, a micro profiling and micro sampling system ("missy") was developed that enables for the first time a direct, automate and low invasive sampling of small volumes (Micro-scale biogeochemical heterogeneity in sediments: A review of available technology and observed evidence. Earth-Science Reviews, 2009. 92(1-2): p. 81-97. 2. Fabricius, A.-L., et al., New Microprofiling and Micro Sampling System for Water Saturated Environmental Boundary Layers

  1. Water orientation and hydrogen-bond structure at the fluorite/water interface

    Science.gov (United States)

    Khatib, Rémi; Backus, Ellen H. G.; Bonn, Mischa; Perez-Haro, María-José; Gaigeot, Marie-Pierre; Sulpizi, Marialore

    2016-04-01

    Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water, and are responsible for the “free OH” signature in the VSFG spectrum, which can be explained from local electronic structure effects. The quantification of the surface termination, near-surface ion distribution and water arrangement is enabled by a combination of advanced phase-resolved Vibrational Sum Frequency Generation spectra of CaF2/water interfaces and state-of-the-art ab initio molecular dynamics simulations which include electronic structure effects.

  2. Solid mesostructured polymer-surfactant films at the air-liquid interface.

    Science.gov (United States)

    Pegg, Jonathan C; Eastoe, Julian

    2015-08-01

    Pioneering work by Edler et al. has spawned a new sub-set of mesostructured materials. These are solid, self-supporting films comprising surfactant micelles encased within polymer hydrogel; composite polymer-surfactant films can be grown spontaneously at the air-liquid interface and have defined and controllable mesostructures. Addition of siliconalkoxide to polymer-surfactant mixtures allows for the growth of mesostructured hybrid polymer-surfactant silica films that retain film geometry after calcinations and exhibit superior mechanical properties to typically brittle inorganic films. Growing films at the air-liquid interface provides a rapid and simple means to prepare ordered solid inorganic films, and to date the only method for generating mesostructured films thick enough (up to several hundred microns) to be removed from the interface. Applications of these films could range from catalysis to encapsulation of hydrophobic species and drug delivery. Film properties and mesostructures are sensitive to surfactant structure, polymer properties and polymer-surfactant phase behaviour: herein it will be shown how film mesostructure can be tailored by directing these parameters, and some interesting analogies will be drawn with more familiar mesostructured silica materials. PMID:25127447

  3. Virtual prototype interface for the Air Force Manned SpacePlane project

    Science.gov (United States)

    Stytz, Martin R.; Banks, Sheila B.; Lewis, John; Johnson, Troy D.

    1998-08-01

    The advent of requirements for worldwide deployment of space assets in support of Air Force operational missions has resulted in the need for a Manned SpacePlane (MSP) that can perform these missions with minimal preflight preparation and little, if any, in-orbit support from a mission control center. Because successful mission accomplishment will depend almost completely upon the MSP crew and the on-board capabilities of the spaceplane, the MSP user interface is a crucial component of successful mission accomplishment. In recognition of this fact, the USAF Phillips Laboratory in conjunction with USAF Space Command initiated the Virtual SpacePlane (VSP) project. To function effectively as an MSP interface development platform, the VSP must demonstrate the capability to simulate anticipated MSP missions and portray the MSP in operation throughout its entire flight regime, from takeoff through space operations and on to recovery via a horizontal landing at an airfield. Therefore, we architected, designed, and implemented a complete VSP that can be used to simulate anticipated Manned SpacePlane missions. The primary objective of the VSP is to be a virtual prototype for user interface design and development, the VSP software architecture and design facilities uncovering, refining and validating MSP user interface requirements. The Virtual SpacePlane reuses software components developed for the Virtual Cockpit and Solar System Modeler (SM) distributed virtual environment (DVE) applications, the Common Object Database (CODB) architecture, and Information Pod (Pod) interface tools developed in our labs. The Virtual Cockpit and Solar System Modeler supplied baseline interface components and tools, 3D graphical models, vehicle motion dynamics models, and DVE communication capabilities. Because we knew that the VSP's requirements would expand and evolve over the life of the project, we use the CODB architecture to facilitate our use of Rapid Evolutionary and Exploratory

  4. Thermodynamic and transport properties of air/water mixtures

    Science.gov (United States)

    Fessler, T. E.

    1981-01-01

    Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.

  5. Interfacial phenomena at the compressed co2-water interface

    Directory of Open Access Journals (Sweden)

    B. Bharatwaj

    2006-06-01

    Full Text Available Compressed CO2 is considered to be a viable alternative to toxic volatile organic solvents with potential applications in areas including separation reactions, and materials formation processes. Thus an interest in CO2 stems from the fact that it is very inexpensive, has low toxicity, and is not a regulated. However, compressed CO2 has a zero dipole moment and weak van der Waals forces and thus is a poor solvent for both polar and most high molecular weight solutes, characteristics that severely restrict its applicability. In order to overcome this inherent inability, surfactant-stabilized organic and aqueous dispersions in CO2 have been proposed. This work will discuss fundamentals and recent advances in the design of amphiphiles for the novel CO2-water interface.

  6. Removal of colloidal particles from quartz collector surfaces as stimulated by the passage of liquid-air interfaces

    NARCIS (Netherlands)

    Suarez, CG; van der Mei, HC; Busscher, HJ

    1999-01-01

    Micron-sized particles adhering to collector surfaces can be detached by passing a liquid-air interface over the adhering particles. Theoretically, the efficiency of particle detachment depends on the interface velocity, the liquid surface tension, the viscosity, and the particle-substratum interact

  7. Adsorption of Small Molecules at Water--Hexane and Water--Membrane Interfaces

    Science.gov (United States)

    Wilson, Michael A.

    1996-03-01

    The interaction of solutes with aqueous interfaces plays a significant role in a variety of physical processes, including general anesthesia and atmospheric chemistry. We present molecular dynamics results for the transfer of several small solutes across water liquid--vapor, water--hexane and water--GMO bilayer membrane interfaces. (A. Pohorille and M. A. Wilson, J. Chem. Phys. (in press, 1995).)^, (A. Pohorille, P. CIeplak, and M. A. Wilson, Chem. Phys. (in press, 1995).) The free energies of transferring small polar molecules across the interface exhibit fairly deep minima while those of nonpolar molecules do not. This is due to a balance between nonelectrostatic contributions --- primarily the work required to create a cavity large enough to accommodate the solute --- and the solute--solvent electrostatic interactions.^1 The surface excess of solute is calculated and compared with experimental results from the Gibbs adsorption isotherm. The interfacial solubilities correlate with measured anesthetic potencies of these compounds, implying that the binding sites for anesthetics are located near the water--membrane interface.

  8. Method to estimate drag coefficient at the air/ice interface over drifting open pack ice from remotely sensed data

    Science.gov (United States)

    Feldman, U.

    1984-01-01

    A knowledge in near real time, of the surface drag coefficient for drifting pack ice is vital for predicting its motions. And since this is not routinely available from measurements it must be replaced by estimates. Hence, a method for estimating this variable, as well as the drag coefficient at the water/ice interface and the ice thickness, for drifting open pack ice was developed. These estimates were derived from three-day sequences of LANDSAT-1 MSS images and surface weather charts and from the observed minima and maxima of these variables. The method was tested with four data sets in the southeastern Beaufort sea. Acceptable results were obtained for three data sets. Routine application of the method depends on the availability of data from an all-weather air or spaceborne remote sensing system, producing images with high geometric fidelity and high resolution.

  9. Linear GPR inversion for lossy soil and a planar air-soil interface

    DEFF Research Database (Denmark)

    Meincke, Peter

    2001-01-01

    A three-dimensional inversion scheme for fixed-offset ground penetrating radar (GPR) is derived that takes into account the loss in the soil and the planar air-soil interface. The forward model of this inversion scheme is based upon the first Born approximation and the dyadic Green function...... for a two-layer medium. The forward model is inverted using the Tikhonov-regularized pseudo-inverse operator. This involves two steps: filtering and backpropagation. The filtering is carried out by numerically solving Fredholm integral equations of the first kind and the backpropagation is performed using...

  10. Interference-Robust Air Interface for 5G Ultra-dense Small Cells

    DEFF Research Database (Denmark)

    Tavares, Fernando Menezes Leitão; Berardinelli, Gilberto; Mahmood, Nurul Huda;

    2016-01-01

    An ultra-dense deployment of small cells is foreseen as the solution to cope with the exponential increase of the data rate demand targeted by the 5th Generation (5G) radio access technology. In this article, we propose an interference-robust air interface built upon the usage of advanced receivers...... as main interference mitigation technique. Both Interference Rejection Combining (IRC) and Successive Interference Cancellation (SIC) principles are considered. An efficient usage of such receivers is ensured by a proper frame structure design and system assumptions. Different approaches for the rank...

  11. Dispersion Relation of a Surface Wave at a Rough Metal-Air Interface

    CERN Document Server

    Kotelnikov, Igor

    2016-01-01

    We derived a dispersion relation of a surface wave at a rough metal-air interface. In contrast to previous publications, we assumed that an intrinsic surface impedance due to a finite electric conductivity of the metal can be of the same order as the roughness-induced impedance. We then applied our results to the analysis of a long-standing problem of the discrepancy between the experimental data on the propagation of surface waves in the terahertz range of frequencies and the classical Drude theory.

  12. Light production at an explosive/air interface. Period covered: October--December 1976

    Energy Technology Data Exchange (ETDEWEB)

    Canada, C.E.

    1976-01-01

    Detonation front arrival time measurements are compared for an optoelectronic and an antenna technique. Fiber optics and photodiodes are used for the optoelectronic method while the antenna technique depends on radiated signals at an explosive/air interface. Analysis indicates that signals measured by the respective techniques are not caused by the same physical mechanism; thus, even though the results are not directly comparable the signals should be self-consistent for a given technique. The optical signals were found to have greater jitter in time and larger variation in magnitude than those signals obtained by the antenna technique.

  13. Diffusion-controlled Adsorption Kinetics of Surfactant at Air/Solution Interface

    Institute of Scientific and Technical Information of China (English)

    刘俊吉; 徐芸; 孙红秀

    2013-01-01

    For the diffusion-controlled adsorption, the expression of dynamic surface adsorption Γ(t) was ob-tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate (SDS) solutions at 25 °C, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.

  14. The Behavior of Amphiphile at Oil-Water Interface by Monte Carlo Simulation

    Institute of Scientific and Technical Information of China (English)

    潘海华; 李啸风; 李浩然; 刘迪霞; 韩世钧

    2003-01-01

    A novel simple two-dimensional square-lattice model of amphiphile at oil-water interface is developed,in which oil and water act as solvent and occupy empty sites and amphiphile occupies chains of sites. In this model, the oil-water interface is fixed, And amphiphile molecules will be enriched at the oil-water interface. The interfacial concentration of amphiphile calculated by Monte Carlo method shows that it is easier for the hydrophilic-hydrophobic balanced amphiphile to stay at the interface. And the adsorption of amphiphile increases with the increase of amphiphile concentration and the decrease with temperature.

  15. Adsorption of oleic acid at sillimanite/water interface.

    Science.gov (United States)

    Kumar, T V Vijaya; Prabhakar, S; Raju, G Bhaskar

    2002-03-15

    The interaction of oleic acid at sillimanite-water interface was studied by adsorption, FT-IR, and zeta potential measurements. The isoelectric point (IEP) of sillimanite obtained at pH 8.0 was found to shift in the presence of oleic acid. This shift in IEP was attributed to chemisorption of oleic acid on sillimanite. Adsorption experiments were conducted at pH 8.0, where the sillimanite surface is neutral. The adsorption isotherm exhibited a plateau around 5 micromol/m2 that correspond to a monolayer formation. Adsorption of oleic acid on sillimanite, alumina, and aluminum hydroxide was studied by FT-IR. Chemisorption of oleic acid on the above substrates was confirmed by FT-IR studies. Hydroxylation of mineral surface was found to be essential for the adsorption of oleic acid molecules. These surface hydroxyl sites were observed to facilitate deprotonation of oleic acid and its subsequent adsorption. Thus protons from oleic acid react with surface hydroxyl groups and form water molecules. Based on the experimental results, the mechanism of oleic acid adsorption on mineral substrate was proposed. Free energy of adsorption was estimated using the Stern-Graham equation for a sillimanite-oleate system. PMID:16290466

  16. Bifurcations of a creeping air-water flow in a conical container

    Science.gov (United States)

    Balci, Adnan; Brøns, Morten; Herrada, Miguel A.; Shtern, Vladimir N.

    2016-10-01

    This numerical study describes the eddy emergence and transformations in a slow steady axisymmetric air-water flow, driven by a rotating top disk in a vertical conical container. As water height Hw and cone half-angle β vary, numerous flow metamorphoses occur. They are investigated for β =30°, 45°, and 60°. For small Hw, the air flow is multi-cellular with clockwise meridional circulation near the disk. The air flow becomes one cellular as Hw exceeds a threshold depending on β . For all β , the water flow has an unbounded number of eddies whose size and strength diminish as the cone apex is approached. As the water level becomes close to the disk, the outmost water eddy with clockwise meridional circulation expands, reaches the interface, and induces a thin layer with anticlockwise circulation in the air. Then this layer expands and occupies the entire air domain. The physical reasons for the flow transformations are provided. The results are of fundamental interest and can be relevant for aerial bioreactors.

  17. STUDY ON THE FUEL AIR MIXING INDUCED BY A SHOCK WAVE PROPAGATING INTO A H2-AIR INTERFACE

    Institute of Scientific and Technical Information of China (English)

    徐胜利; 岳朋涛; 韩肇元

    2001-01-01

    2 nd-order upwind TVD scheme was used to solve the laminar, fully Navier Stokes equations. The numerical simulations were done on the propagation of a shock wave with la 8 = 2 and 4 into a hydrogen and air mixture in a duct and a duct with a rearward step. The results indicate that a swirling vortex may be generated in the lopsided interface behind the moving shock. Meanwhile, the complex shock system is also formed in this shear flow region. A large swirling vortex is produced and the fuel mixing can be enhanced by a shock wave at lov Mach number. But in a duct with a rearward step, the shock almost disappears in hydrogen for Mas = 2. The shock in hydrogen will become strong if Mas is large. Similar to the condition ofa shock moving in a duct full of hydrogen and air, a large vortex can be formed in the shear flow region. The large swirling vortex even gets through the reflected shock and impacts on the lower wall. Then, the distribution of hydrogen behind the rearward step is divided into two regions. The transition from regular reflection to Mach reflection vas observed as well in case Mas = 4 .

  18. Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers

    OpenAIRE

    Kalenik Marek

    2015-01-01

    Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers. The paper presents the analysis of results of the investigations concerning the influence of various constructive solutions of the air-water mixers on hydraulic operating conditions of the air lift pump. The scope of the investigations encompassed the determination of characteristics of delivery head and delivery rate for three types of air-water mixers applied in the constructed air lift p...

  19. Theoretical vibrational sum-frequency generation spectroscopy of water near lipid and surfactant monolayer interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Roy, S.; Gruenbaum, S. M.; Skinner, J. L. [Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2014-11-14

    Understanding the structure of water near cell membranes is crucial for characterizing water-mediated events such as molecular transport. To obtain structural information of water near a membrane, it is useful to have a surface-selective technique that can probe only interfacial water molecules. One such technique is vibrational sum-frequency generation (VSFG) spectroscopy. As model systems for studying membrane headgroup/water interactions, in this paper we consider lipid and surfactant monolayers on water. We adopt a theoretical approach combining molecular dynamics simulations and phase-sensitive VSFG to investigate water structure near these interfaces. Our simulated spectra are in qualitative agreement with experiments and reveal orientational ordering of interfacial water molecules near cationic, anionic, and zwitterionic interfaces. OH bonds of water molecules point toward an anionic interface leading to a positive VSFG peak, whereas the water hydrogen atoms point away from a cationic interface leading to a negative VSFG peak. Coexistence of these two interfacial water species is observed near interfaces between water and mixtures of cationic and anionic lipids, as indicated by the presence of both negative and positive peaks in their VSFG spectra. In the case of a zwitterionic interface, OH orientation is toward the interface on the average, resulting in a positive VSFG peak.

  20. Water orientation and hydrogen-bond structure at the fluorite/water interface

    CERN Document Server

    Khatib, Rémi; Bonn, Mischa; Perez-Haro, María-José; Gaigeot, Marie-Pierre; Sulpizi1, Marialore

    2016-01-01

    Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical-experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important flourite-water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water, and are responsible for the free OH signature in the SFG spectrum, which can be explained from local electronic structure effects. The quantification of the surface termination, near-surface ion distribution and water arrangement is enabled by a combination of advanced phase-resolved Vibrational Sum Frequency Generation spectra of flourite-water interfa...

  1. Forced convection heat transfer to air/water vapor mixtures

    Science.gov (United States)

    Richards, D. R.; Florschuetz, L. W.

    1986-01-01

    Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components.

  2. Structure and Depletion at Fluoro- and Hydro-carbon/Water Liquid/Liquid Interfaces

    OpenAIRE

    Kashimoto, Kaoru; Yoon, Jaesung; Hou, Binyang; Chen, Chiu-hao; Lin, Binhua; Aratono, Makoto; Takiue, Takanori; Schlossman, Mark L.

    2008-01-01

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

  3. Concentrations of anesthetics across the water-membrane interface; the Meyer-Overton hypothesis revisited

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.; New, M. H.; Chipot, C.

    1998-01-01

    The free energies of transferring a variety of anesthetic and nonanesthetic compounds across water-oil and water-membrane interfaces were obtained using computer simulations. Anesthetics exhibit greatly enhanced concentrations at these interfaces, compared to nonanesthetics. The substitution of the interfacial solubilites of the anesthetics for their bulk lipid solubilities in the Meyer-Overton relation, was found to give a better correlation, indicating that the potency of an anesthetic is directly proportional to its solubility at the interface.

  4. Arsenate adsorption mechanisms at the allophane - Water interface

    Science.gov (United States)

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2005-01-01

    We investigated arsenate (As(V)) reactivity and surface speciation on amorphous aluminosilicate mineral (synthetic allophane) surfaces using batch adsorption experiments, powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS). The adsorption isotherm experiments indicated that As(V) uptake increased with increasing [As(V)]0 from 50 to 1000 ??M (i.e., Langmuir type adsorption isotherm) and that the total As adsorption slightly decreased with increasing NaCl concentrations from 0.01 to 0.1 M. Arsenate adsorption was initially (0-10 h) rapid followed by a slow continuum uptake, and the adsorption processes reached the steady state after 720 h. X-ray absorption spectroscopic analyses suggest that As(V) predominantly forms bidentate binuclear surface species on aluminum octahedral structures, and these species are stable up to 11 months. Solubility calculations and powder XRD analyses indicate no evidence of crystalline AI-As(V) precipitates in the experimental systems. Overall, macroscopic and spectroscopic evidence suggest that the As(V) adsorption mechanisms at the allophane-water interface are attributable to ligand exchange reactions between As(V) and surface-coordinated water molecules and hydroxyl and silicate ions. The research findings imply that dissolved tetrahedral oxyanions (e.g., H2PO42- and H2AsO42-) are readily retained on amorphous aluminosilicate minerals in aquifer and soils at near neutral pH. The innersphere adsorption mechanisms might be important in controlling dissolved arsenate and phosphate in amorphous aluminosilicate-rich low-temperature geochemical environments. ?? 2005 American Chemical Society.

  5. ATMOSPHERIC MOISTURE CONDENSATION TO WATER RECOVERY BY HOME AIR CONDITIONERS

    Directory of Open Access Journals (Sweden)

    Amir Hossein Mahvi

    2013-01-01

    Full Text Available Earth’s atmosphere contains billion cubic meters of fresh water, which is considerable as a reliable water resource, especially in sultry areas. What is important in this context, how to extract the water, in an economic manner. In order to extract water from air conditioner, no need to spend any cost, because water produced as a by-product and trouble production. This cross-sectional study was conducted to evaluate the quantity and chemical quality of water obtained from Bandar Abbas air conditioners; at intervals beginning of March to early December of 2010. Sixty six samples were taken in cluster random plan. Bandar Abbas divided into four clusters; based on distance to shore and population density. Chemical tests which included: Turbidity, alkalinity, total hardness, Dissolved Solids (TDS and Electrical Conductivity (EC and quantity measurement were performed on them. Obtained water had slightly acidic pH, near to neutral range. Total dissolved solids, electrical conductivity, total hardness and alkalinity of extracted water were in low rate. Each air conditioner produced 36 liter per day averagely. Split types obtained more water to window air conditioners. With regard to some assumptions, approximately 4680 to 9360 cubic meter per day water is obtainable which is suitable for many municipal and industrial water applications.

  6. Air flotation treatment of salmon processing waste water

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This paper discusses methods for the reduction of the pollution strength of salmon processing waste water. Past research has indicated the success of air pressure...

  7. A study of the ice-water interface using the TIP4P/2005 water model

    CERN Document Server

    Benet, Jorge; Sanz, Eduardo

    2014-01-01

    In this work we study the ice-water interface under coexistence conditions by means of molecular simulations using the TIP4P/2005 water model. Following the methodology proposed by Hoyt and co-workers [J. J. Hoyt, M. Asta and A. Karma, Phys. Rev. Lett., 86, 5530, (2001)] we measure the interfacial free energy of ice with liquid water by analysing the spectrum of capillary fluctuations of the interface. We get an orientationally averaged interfacial free energy of 27(2) mN/m, in good agreement with a recent estimate obtained from simulation data of the size of critical clusters [E. Sanz, C. Vega, J. R. Espinosa, R. Caballero-Bernal, J. L. F. Abascal and C. Valeriani, JACS, 135, 15008, (2013)]. We also estimate the interfacial free energy of different planes and obtain 27(2), 28(2)and 28(2) mN/m for the basal, the primary prismatic and the secondary prismatic planes respectively. Finally, we inspect the structure of the interface and find that its thickness is of approximately 4-5 molecular diameters. Moreover,...

  8. Drop Impact on Liquid Surfaces: Formation of Lens and Spherical Drops at the Air-Liquid Interface

    CERN Document Server

    Yakhshi-Tafti, Ehsan; Kumar, Ranganathan; 10.1016/j.jcis.2010.06.029

    2010-01-01

    Droplets at the air-liquid interface of immiscible liquids usually form partially-submerged lens shapes (e.g. water on oil). In addition to this structure, we showed that droplets released from critical heights above the target liquid can sustain the impact and at the end maintain a spherical ball-shape configuration above the surface, despite undergoing large deformation. Spherical drops are unstable and will transform into the lens mode due to slight disturbances. Precision dispensing needles with various tip diameter sizes were used to release pendant drops of deionized water onto the surface of fluorocarbon liquid (FC-43, 3M). A cubic relationship was found between the nozzle tip diameter and the released droplet diameter. Drop impact was recorded by a high speed camera at a rate of 2000 frames per second. In order for the water drops to sustain the impact and retain a spherical configuration at the surface of the target liquid pool, it is required that they be of a critical size and be released from a ce...

  9. Langmuir films of solids-free bitumen and bitumen fractions at toluene/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Solovyev, A.; Zhang, L.; Xu, Z.; Masliyah, J. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

    2006-07-01

    This study examined the interfacial behaviour of bitumen and bitumen fractions at an organic solvent/water interface using a Langmuir trough and atomic force microscope (AFM). The objective was to better understand the stability of water-in-solvent diluted bitumen emulsions. The accumulation of interfacially active components at the oil/water interfaces promotes the formation of interfacial films, which resist the coalescence of water droplets thereby stabilizing water-in-oil emulsions. The bitumen fractions included maltene, and asphaltene films at the toluene/de-ionized water interface. Langmuir films of bitumen, maltene and asphaltene were spread at toluene/water interfaces where they exhibited different interfacial pressure-area isotherms. Asphaltenes were found to be irreversibly adsorbed at the toluene/water interface when the films were subjected to multiple washings with fresh toluene. Interfacial pressure-area isotherms remained unchanged. Consecutive washings of maltene films with fresh toluene showed a progressive loss of interfacial materials from the toluene/water interface. However, the pressure-area isotherms showed a consistent shift during the first 2 consecutive bitumen film washings and then no further shift with subsequent washings. After the first 2 washings, the isotherms were same as the original asphaltene films. According to AFM images of Langmuir-Blodgett films deposited from the toluene/water interface, the topographical features of asphaltene films resembled that of bitumen films. However, they were very different from that of maltene films. The study results demonstrated that the bitumen film at a toluene/water interface is composed primarily of asphaltenes. The asphaltenes contribute to the stability of water-in-diluted bitumen emulsions because they are irreversibly adsorbed at the interface. tabs., figs.

  10. The exchange of SVOCs across the air-sea interface in Singapore's coastal environment

    OpenAIRE

    He, J.; Balasubramanian, R

    2010-01-01

    Coastal areas are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs, OCPs and PCBs from atmospheric inputs. Dry particulate and wet depositions, and air-water diffusive exchange in the Singapore's south coastal area, where most of chemical and oil refinery industries are situated in, were estimated. Based on a yearly dataset, the mean annual dry particulate deposition fluxes of ∑16-PAHs, ∑7 OCPs and &am...

  11. Free-surface Flow Interface And Air-Entrainment Modelling Using OpenFOAM

    OpenAIRE

    Lopes, Pedro

    2013-01-01

    The use of hydraulic structures to control flooding has a history of long practice within civil engineering infrastructure. Hydraulic structures under turbulent flow conditions frequently involve free surface fl ow and interactions between air and water. This can be observed in different kinds of structures, e.g. gullies, manholes or stepped spillways. In this doctoral program, Computational Fluid Dynamics numerical models will be used to simulate...

  12. The Richtmyer-Meshkov instability of a "V" shaped air/helium interface subjected to a weak shock

    Science.gov (United States)

    Zhai, Zhigang; Dong, Ping; Si, Ting; Luo, Xisheng

    2016-08-01

    The Richtmyer-Meshkov instability of a "V" shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a "V" shaped interface with accurate initial conditions. Five kinds of air/helium "V" shaped interfaces with different vertex angles (60°, 90°, 120°, 140°, and 160°), i.e., different amplitude-wavelength ratios, are formed to highlight the effects of initial conditions, especially the initial amplitude, on the flow characteristics. The interface morphologies identified by the high-speed schlieren photography show that a spike is generated from the vertex after the shock impact, and grows constantly with time accompanied by the occurrence of the phase reversal. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of the interface mixing width of a heavy/light interface configuration after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. It is found for the first time in a heavy/light interface configuration that the linear growth rate of interface width is a non-monotonous function of the initial perturbation amplitude-wavelength ratio. In the nonlinear stage, it is confirmed that the width growth rate of interface with high initial amplitudes can be well predicted by a model proposed by Dimonte and Ramaprabhu ["Simulations and model of the nonlinear Richtmyer-Meshkov instability," Phys. Fluids 22, 014104 (2010)].

  13. Numerical research on the mechanism of contaminant release through the porous sediment-overlying water interface

    Institute of Scientific and Technical Information of China (English)

    郑淑君; 曹洋; 郭加宏

    2014-01-01

    After the pollutant discharged into the river or lake has been reduced, the release of the contaminant from the sediment to the overlying water may cause the river and lake be contaminated again. On the condition that the overlying water flow does not lead to sediment suspension, numerical researches are carried out for the mechanism of contaminant release through the sediment-overlying water interface. The overlying water flow is calculated as turbulence. The sediment is regarded as isotropic homogeneous porous medium, therefore the seepage field in the porous sediment layer is obtained by solving Darcy’s equations. Coupled two dimensional steady flows of the overlying water and the pore water in the sediment are calculated. Based on the flow fields obtained, the unsteady contaminant solute transportation process in the pore water in the sediment and the overlying water is numerically simulated, as the shapes of the sediment-overlying water interface are flat or periodic triangular respectively. Numerical results show that the exchange of the pore water and the overlying water is an important factor which decides the release flux of the contaminant from the sediment to the overlying water. The pressure distribution produced by the overlying water flow along the sediment-overlying water interface, as it is not flat, may induce the seepage of the pore water in the sediment and through the sediment-overlying water interface, which may increase the release flux of the contaminant from the sediment to the overlying water.

  14. A dose-controlled system for air-liquid interface cell exposure and application to zinc oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    Ferron George A

    2009-12-01

    Full Text Available Abstract Background Engineered nanoparticles are becoming increasingly ubiquitous and their toxicological effects on human health, as well as on the ecosystem, have become a concern. Since initial contact with nanoparticles occurs at the epithelium in the lungs (or skin, or eyes, in vitro cell studies with nanoparticles require dose-controlled systems for delivery of nanoparticles to epithelial cells cultured at the air-liquid interface. Results A novel air-liquid interface cell exposure system (ALICE for nanoparticles in liquids is presented and validated. The ALICE generates a dense cloud of droplets with a vibrating membrane nebulizer and utilizes combined cloud settling and single particle sedimentation for fast (~10 min; entire exposure, repeatable (2. The cell-specific deposition efficiency is currently limited to 0.072 (7.2% for two commercially available 6-er transwell plates, but a deposition efficiency of up to 0.57 (57% is possible for better cell coverage of the exposure chamber. Dose-response measurements with ZnO nanoparticles (0.3-8.5 μg/cm2 showed significant differences in mRNA expression of pro-inflammatory (IL-8 and oxidative stress (HO-1 markers when comparing submerged and air-liquid interface exposures. Both exposure methods showed no cellular response below 1 μg/cm2 ZnO, which indicates that ZnO nanoparticles are not toxic at occupationally allowed exposure levels. Conclusion The ALICE is a useful tool for dose-controlled nanoparticle (or solute exposure of cells at the air-liquid interface. Significant differences between cellular response after ZnO nanoparticle exposure under submerged and air-liquid interface conditions suggest that pharmaceutical and toxicological studies with inhaled (nano-particles should be performed under the more realistic air-liquid interface, rather than submerged cell conditions.

  15. Behaviour of cetyltrimethylammonium bromide, Triton X-100 and Triton X-114 in mixed monolayer at the (water–air) interface

    International Nuclear Information System (INIS)

    Graphical abstract: Synergetic effect of the binary and ternary mixtures of surfactants at their concentration equal to 1 · 10−5 M in the reduction of the water surface tension. -- Highlights: • Joos equation modified by us is useful for the ternary mixtures of surfactant. • Composition of the CTAB + TX-100 + TX-114 monolayer is not proportional to the bulk phase. • Synergetic effect of the TX-100, TX-114 and CTAB mixtures is confirmed by the adsorption efficiency. • Adsorption efficiency of ternary mixtures is not related to their effectiveness. -- Abstract: The measured values of the surface tension of aqueous solution of binary and ternary mixtures including CTAB, TX-100 and TX-114 were compared to those calculated from the Joos equation modified by us. It appeared that it is possible to predict, at the first approximation, the changes of the surface tension of aqueous solutions studied as a function of concentration of all possible binary and ternary mixtures in the range from 0 to the minimal value of their surface tension. However, the deviations of the calculated values of surface tension from those measured depend on the synergetic effect in the reduction of water surface tension. This effect was established by the values of the molecular interaction parameter calculated from the Rosen and Hua equations. From these equations the relative mole fraction of three surfactants in the mixed monolayer at the (water–air) interface was also determined and compared to that obtained by using surface excess concentrations of particular surfactants in this monolayer. As follows from this comparison the Rosen and Hua equations give the proper relation between the mole fraction of TX-100, TX-114 and CTAB in the monolayer but on the condition it is determined at the same concentration of each surfactant in the mixture. The synergetic effect of ternary mixture in the reduction of the water surface tension is also reflected in the changes of the values of the

  16. Liquid-Air Interface Corrosion Testing Simulating The Environment Of Hanford Double Shell Tanks

    Energy Technology Data Exchange (ETDEWEB)

    Wiersma, B.; Gray, J. R.; Garcia-Diaz, B. L.; Murphy, T. H.; Hicks, K. R.

    2014-01-30

    Coupon tests on A537 carbon steel materials were conducted to evaluate the Liquid-Air Interface (LAI) corrosion susceptibility in a series of solutions designed to simulate conditions in the radioactive waste tanks located at the Hanford Nuclear Facility. The new stress corrosion cracking requirements and the impact of ammonia on LAI corrosion were the primary focus. The minimum R value (i.e., molar ratio of nitrite to nitrate) of 0.15 specified by the new stress corrosion cracking requirements was found to be insufficient to prevent pitting corrosion at the LAI. The pH of the test solutions was 10, which was actually less than the required pH 11 defined by the new requirements. These tests examined the effect of the variation of the pH due to hydroxide depletion at the liquid air interface. The pits from the current testing ranged from 0.001 to 0.008 inch in solutions with nitrate concentrations of 0.4 M and 2.0 M. The pitting and general attack that occurred progressed over the four-months. No significant pitting was observed, however, for a solution with a nitrate concentration of 4.5 M. The pitting depths observed in these partial immersion tests in unevaporated condensates ranged from 0.001 to 0.005 inch after 4 months. The deeper pits were in simulants with low R values. Simulants with R values of approximately 0.6 to 0.8 appeared to significantly reduce the degree of attack. Although, the ammonia did not completely eliminate attack at the LAI, the amount of corrosion in an extremely corrosive solution was significantly reduced. Only light general attack (< 1 mil) occurred on the coupon in the vicinity of the LAI. The concentration of ammonia (i.e., 50 ppm or 500 ppm) did not have a strong effect.

  17. Development of a Bench-Top Air-to-Water Heat Pump Experimental Apparatus

    Directory of Open Access Journals (Sweden)

    H. I. Abu-Mulaweh

    2009-09-01

    Full Text Available A bench-top air-to-water heat pump experimental apparatus was designed,developed, and constructed for instructional and demonstrative purposes. Thisair-to-water heat pump experimental apparatus is capable of demonstratingthermodynamics and heat transfer concepts and principles. This heat pumpexperimental setup was designed around the vapor compression refrigerationcycle. This experimental apparatus has an intuitive user interface, reliable, safefor student use, and portable. The interface is capable of allowing dataacquisition by a computer. A PC-based control system which consists ofLabVIEW and data acquisition unit is employed to monitor and control thisexperimental laboratory apparatus. This paper provides details about thedevelopment of this unit and the integration of the electrical/electronic componentand the control system.

  18. Small-angle reflectometry of milk protein (β -casein) at the air/serum interface and its conformational changes due to fat content and temperature

    International Nuclear Information System (INIS)

    Full text: The surface structure of dispersed emulsions play a key role in stability of the system. Proteins being one of the most important surface-active components in foods stabilise interfaces by self-interaction, resulting in a stiff visco-elastic adsorbed layer. These interactions are sensitive to disruptive effects of lipids. Previous kinetics studies by the group 1 using the X-ray reflectivity method to investigate the surface adsorption of milk proteins indicate that β -casein had a stronger affinity for the air-liquid interface compared to whey proteins. It has been shown that initially a dense protein layer, with the thickness of 20 Angstroms is formed then a second more diffuse layer with lower volume density of protein follows. Here we report the conformational changes (with particular emphasise on the β -casein tail) occurred at the air-milk serum interface due to the effects of milk fat content, temperature and the milk preparation technique (ie homogenisation vs microfluidisation). In the effect of fat content on the adsorption of protein into the interface the key conclusion is that at lower temperatures the surface composition remains unchanged. The compositional changes, however, become significant at room temperature indicating adsorption of less reflective-water-soluble components into the surface layer. Repulsive interactions between casein aggregates are also involved. Microfluidised samples having the advantage of smaller particle size prove to be more stable to fat or temperature effects compared to the corresponding homogenised milks

  19. The role of transition metal interfaces on the electronic transport in lithium–air batteries

    DEFF Research Database (Denmark)

    Chen, Jingzhe; Hummelshøj, Jens S.; Thygesen, Kristian Sommer;

    2011-01-01

    at the top of the anti bonding peroxide π*(2px) and π*(2py) levels in the Li2O2 valence band. Under an applied bias, this can result in a reduced transmission, since the anti bonding σ*(2pz) level in the Li2O2 conduction band is found to couple strongly to the metal substrate and create localized interface......Low electronic conduction is expected to be a main limiting factor in the performance of reversible lithium–air, Li–O2, batteries. Here, we apply density functional theory and non-equilibrium Green's function calculations to determine the electronic transport through lithium peroxide, Li2O2, formed...... at the cathode during battery discharge. We find the transport to depend on the orientation and lattice matching of the insulator–metal interface in the presence of Au and Pt catalysts. Bulk lithium vacancies are found to be available and mobile under battery charging conditions, and found to pin the Fermi level...

  20. Numerical simulation and experimental detection of leaky Lamb waves induced by pulse laser at air-solid interfaces

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on the thermoelastic mechanism of laser ultrasonic, the problems of the thermal conduction and the coupling between the motion of solid and fluid are solved by using the finite element method. And then the transient waveforms of leaky Lamb waves induced by pulse laser action on the air-aluminum interface are obtained. Experimental signals of laser-induced leaky Lamb waves at the air-alu- minum interface are detected by applying an our-developed detector, based on the light deflection principle. The dispersion and attenuation properties of leaky Lamb waves are analyzed through the phase spectral analysis.

  1. A mixed air/air and air/water heat pump system ensures the air-conditioning of a cinema; Un systeme mixte PAC air/air et air/eau climatise un cinema

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2001-03-01

    This article presents the air conditioning system of a new cinema complex of Boulogne (92, France) which comprises a double-flux air processing plant and two heat pumps. Each heat pump has two independent refrigerating loops: one with a air condenser and the other with a water condenser. This system allows to limit the power of the loop and to reduce the size of the cooling tower and of the vertical ducts. This article describes the technical characteristics of the installation: thermodynamic units, smoke clearing, temperature control, air renewing. (J.S.)

  2. Heat and mass transfer of water at nanoscale solid-liquid interfaces

    OpenAIRE

    Fasano, Matteo

    2015-01-01

    A better physical understanding of heat and mass transfer of water at nanoscale solid interfaces is essential for the rational design of novel nanoconstructs for clean water and energy as well as for biomedical applications. Both nanoscale transfer phenomena are strongly influenced by solid-liquid nonbonded interactions occurring at the interface. First, classical Molecular Dynamics (MD) is used for investigating water transport in the proximity of several inorganic and biological solid surfa...

  3. Interrelationships of petiole air canal architecture, water depth and convective air flow in Nymphaea odorata (Nymphaeaceae)

    Science.gov (United States)

    Premise of the study--Nymphaea odorata grows in water up to 2 m deep, producing fewer, larger leaves in deeper water. This species has a convective flow system that moves gases from younger leaves through submerged parts to older leaves, aerating submerged parts. Petiole air canals are in the conv...

  4. New type of capillary for use as ion beam collimator and air-vacuum interface

    Science.gov (United States)

    Stoytschew, V.; Schulte-Borchers, M.; Božičević Mihalića, Iva; Perez, R. D.

    2016-08-01

    Glass capillaries offer a unique way to combine small diameter ion beam collimation with an air-vacuum interface for ambient pressure ion beam applications. Usually they have an opening diameter of a few microns, limiting the air inflow sufficiently to maintain stable conditions on the vacuum side. As the glass capillaries generally are quite thin and fragile, handling of the capillary in the experiment becomes difficult. They also introduce an X-ray background produced by the capillary wall material, which has to be shielded or subtracted from the data for Particle Induced X-ray Emission (PIXE) applications. To overcome both drawbacks, a new type of conical glass capillary has been developed. It has a higher wall thickness eliminating the low energy X-ray background produced by common capillaries and leading to a more robust lens. The results obtained in first tests show, that this new capillary is suitable for ion beam collimation and encourage further work on the capillary production process to provide thick wall capillaries with an outlet diameter in the single digit micro- or even nanometre range.

  5. Plants Clean Air and Water for Indoor Environments

    Science.gov (United States)

    2007-01-01

    Wolverton Environmental Services Inc., founded by longtime government environmental scientist B.C. "Bill" Wolverton, is an environmental consulting firm that gives customers access to the results of his decades of cutting-edge bioremediation research. Findings about how to use plants to improve indoor air quality have been published in dozens of NASA technical papers and in the book, "How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office." The book has now been translated into 12 languages and has been on the shelves of bookstores for nearly 10 years. A companion book, "Growing Clean Water: Nature's Solution to Water Pollution," explains how plants can clean waste water. Other discoveries include that the more air that is allowed to circulate through the roots of the plants, the more effective they are at cleaning polluted air; and that plants play a psychological role in welfare in that people recover from illness faster in the presence of plants. Wolverton Environmental is also working in partnership with Syracuse University, to engineer systems consisting of modular wicking filters tied into duct work and water supplies, essentially tying plant-based filters into heating, ventilation, and air conditioning (HVAC) systems. Also, the company has recently begun to assess the ability of the EcoPlanter to remove formaldehyde from interior environments. Wolverton Environmental is also in talks with designers of the new Stennis Visitor's Center, who are interested in using its designs for indoor air-quality filters

  6. Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention

    Directory of Open Access Journals (Sweden)

    Petra Ditsche-Kuru

    2011-03-01

    Full Text Available Superhydrophobic surfaces of plants and animals are of great interest for biomimetic applications. Whereas the self-cleaning properties of superhydrophobic surfaces have been extensively investigated, their ability to retain an air film while submerged under water has not, in the past, received much attention. Nevertheless, air retaining surfaces are of great economic and ecological interest because an air film can reduce friction of solid bodies sliding through the water. This opens perspectives for biomimetic applications such as low friction fluid transport or friction reduction on ship hulls. For such applications the durability of the air film is most important. While the air film on most superhydrophobic surfaces usually lasts no longer than a few days, a few semi-aquatic plants and insects are able to hold an air film over a longer time period. Currently, we found high air film persistence under hydrostatic conditions for the elytra of the backswimmer Notonecta glauca which we therefore have chosen for further investigations. In this study, we compare the micro- and nanostructure of selected body parts (sternites, upper side of elytra, underside of elytra in reference to their air retaining properties. Our investigations demonstrate outstanding air film persistence of the upper side of the elytra of Notonecta glauca under hydrostatic and hydrodynamic conditions. This hierarchically structured surface was able to hold a complete air film under hydrostatic conditions for longer than 130 days while on other body parts with simple structures the air film showed gaps (underside of elytra or even vanished completely after a few days (sternites. Moreover, the upper side of the elytra was able to keep an air film up to flow velocities of 5 m/s. Obviously the complex surface structure with tiny dense microtrichia and two types of larger specially shaped setae is relevant for this outstanding ability. Besides high air film persistence, the

  7. Properties of Nanocrystalline Thin Films of Metals and Semiconductors Obtained at the Water-Oil Interface

    OpenAIRE

    Stansfield, Gemma Louise

    2013-01-01

    The natural world artfully harnesses the interface between immiscible liquids tocarry out vital processes such as growing bones and contracting muscles. In contrast,synthetic chemists generally regard such an interface as an intractable barrier to becircumvented by the use of phase transfer reagents. A small number of studies haveexplored the use of the water-oil interface to synthesize inorganic nanostructures, materialsthat have assumed great significance in recent times. In these studies, ...

  8. Self-motion of soap at an oil-water interface

    Science.gov (United States)

    Nakata, Satoshi; Hiromatsu, Shin-ichi

    2005-03-01

    The self-motion of a sodium oleate (soap) disk at an oil/water interface was investigated as an autonomous system under nonequilibrium and isothermal conditions. The oleate molecules that developed from the disk transferred to both the toluene and water phases during self-motion. When the sodium oleate disk was removed from the toluene/water interface, the interfacial tension nearly recovered to the value without the disk. The duration of the motion increased as the volume of both phases increased. These results suggest that this self-motion continues due to a significant transfer of oleate molecules from the interface to both phases.

  9. A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)] [and others

    1995-09-01

    This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within {plus_minus}8%.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-01-01

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

  11. Behavior of Water Jet Accompanied with Air Suction

    Science.gov (United States)

    Kawakami, Hironobu; Ishido, Tsutomu; Ihara, Akio

    In order to atomize a liquid, the authors have investigated the behavior of air-water jets. In a series of experiments, we have discovered a strange phenomenon that the water jet accompanied with air suction from the free surface has made a periodic radial splash of water drop. The purpose of the present paper is to clear out the origin of this phenomenon and the behavior of water jet accompanied with air suction. The behavior of water jet has been photographed by a digital camera aided with a flashlight and high-speed video camera. Those experiments enable us to find the origin of a periodic radial splash due to a formation of single air bubble at the flow separation region inside the nozzle and due to explosive expansion of the bubble after injected in the free space. In order to analyze the radial splash of water, we have conducted the equation of spherical liquid membrane. The numerical results obtained have been compared with the experimental results and good agreement has been obtained in radial expansion velocity.

  12. Influence of Water Salinity on Air Purification from Hydrogen Sulfide

    Directory of Open Access Journals (Sweden)

    Leybovych L.I.

    2015-12-01

    Full Text Available Mathematical modeling of «sliding» water drop motion in the air flow was performed in software package FlowVision. The result of mathematical modeling of water motion in a droplet with diameter 100 microns at the «sliding» velocity of 15 m/s is shown. It is established that hydrogen sulfide oxidation occurs at the surface of phases contact. The schematic diagram of the experimental setup for studying air purification from hydrogen sulfide is shown. The results of the experimental research of hydrogen sulfide oxidation by tap and distilled water are presented. The dependence determining the share of hydrogen sulfide oxidized at the surface of phases contact from the dimensionless initial concentration of hydrogen sulfide in the air has been obtained.

  13. Water Tank with Capillary Air/Liquid Separation

    Science.gov (United States)

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

    2010-01-01

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

  14. Emission to air, water and ground: legislation in Norway

    International Nuclear Information System (INIS)

    The article discusses Norwegian legislation on emission to air, water and ground. Pollution in the sense of the law is defined as ''the addition of solid matter, gas or liquid to air, water or ground''. The concept of pollution is, however, more far-reaching as even noise, light and radiation may be regarded as pollution although these are not discussed. Any pollution is prohibited. But there are two exceptions: commonly accepted pollutions such as arising from wood burning and agriculture, and emissions allowed by special permission from the National State Pollution Control Authority. The article also discusses liability issues

  15. Transport-limited water splitting at ion-selective interfaces during concentration polarization

    DEFF Research Database (Denmark)

    Nielsen, Christoffer Peder; Bruus, Henrik

    2014-01-01

    We present an analytical model of salt- and water-ion transport across an ion-selective interface based on an assumption of local equilibrium of the water-dissociation reaction. The model yields current-voltage characteristics and curves of water-ion current versus salt-ion current, which are in ...

  16. Numerical Evaluation of Fluid Mixing Phenomena in Boiling Water Reactor Using Advanced Interface Tracking Method

    Science.gov (United States)

    Yoshida, Hiroyuki; Takase, Kazuyuki

    Thermal-hydraulic design of the current boiling water reactor (BWR) is performed with the subchannel analysis codes which incorporated the correlations based on empirical results including actual-size tests. Then, for the Innovative Water Reactor for Flexible Fuel Cycle (FLWR) core, an actual size test of an embodiment of its design is required to confirm or modify such correlations. In this situation, development of a method that enables the thermal-hydraulic design of nuclear reactors without these actual size tests is desired, because these tests take a long time and entail great cost. For this reason, we developed an advanced thermal-hydraulic design method for FLWRs using innovative two-phase flow simulation technology. In this study, a detailed Two-Phase Flow simulation code using advanced Interface Tracking method: TPFIT is developed to calculate the detailed information of the two-phase flow. In this paper, firstly, we tried to verify the TPFIT code by comparing it with the existing 2-channel air-water mixing experimental results. Secondary, the TPFIT code was applied to simulation of steam-water two-phase flow in a model of two subchannels of a current BWRs and FLWRs rod bundle. The fluid mixing was observed at a gap between the subchannels. The existing two-phase flow correlation for fluid mixing is evaluated using detailed numerical simulation data. This data indicates that pressure difference between fluid channels is responsible for the fluid mixing, and thus the effects of the time average pressure difference and fluctuations must be incorporated in the two-phase flow correlation for fluid mixing. When inlet quality ratio of subchannels is relatively large, it is understood that evaluation precision of the existing two-phase flow correlations for fluid mixing are relatively low.

  17. Culturing of Human Nasal Epithelial Cells at the Air Liquid Interface

    Science.gov (United States)

    Müller, Loretta; Brighton, Luisa E.; Carson, Johnny L.; Fischer, William A.; Jaspers, Ilona

    2013-01-01

    In vitro models using human primary epithelial cells are essential in understanding key functions of the respiratory epithelium in the context of microbial infections or inhaled agents. Direct comparisons of cells obtained from diseased populations allow us to characterize different phenotypes and dissect the underlying mechanisms mediating changes in epithelial cell function. Culturing epithelial cells from the human tracheobronchial region has been well documented, but is limited by the availability of human lung tissue or invasiveness associated with obtaining the bronchial brushes biopsies. Nasal epithelial cells are obtained through much less invasive superficial nasal scrape biopsies and subjects can be biopsied multiple times with no significant side effects. Additionally, the nose is the entry point to the respiratory system and therefore one of the first sites to be exposed to any kind of air-borne stressor, such as microbial agents, pollutants, or allergens. Briefly, nasal epithelial cells obtained from human volunteers are expanded on coated tissue culture plates, and then transferred onto cell culture inserts. Upon reaching confluency, cells continue to be cultured at the air-liquid interface (ALI), for several weeks, which creates more physiologically relevant conditions. The ALI culture condition uses defined media leading to a differentiated epithelium that exhibits morphological and functional characteristics similar to the human nasal epithelium, with both ciliated and mucus producing cells. Tissue culture inserts with differentiated nasal epithelial cells can be manipulated in a variety of ways depending on the research questions (treatment with pharmacological agents, transduction with lentiviral vectors, exposure to gases, or infection with microbial agents) and analyzed for numerous different endpoints ranging from cellular and molecular pathways, functional changes, morphology, etc. In vitro models of differentiated human nasal epithelial

  18. Culturing of human nasal epithelial cells at the air liquid interface.

    Science.gov (United States)

    Müller, Loretta; Brighton, Luisa E; Carson, Johnny L; Fischer, William A; Jaspers, Ilona

    2013-10-08

    In vitro models using human primary epithelial cells are essential in understanding key functions of the respiratory epithelium in the context of microbial infections or inhaled agents. Direct comparisons of cells obtained from diseased populations allow us to characterize different phenotypes and dissect the underlying mechanisms mediating changes in epithelial cell function. Culturing epithelial cells from the human tracheobronchial region has been well documented, but is limited by the availability of human lung tissue or invasiveness associated with obtaining the bronchial brushes biopsies. Nasal epithelial cells are obtained through much less invasive superficial nasal scrape biopsies and subjects can be biopsied multiple times with no significant side effects. Additionally, the nose is the entry point to the respiratory system and therefore one of the first sites to be exposed to any kind of air-borne stressor, such as microbial agents, pollutants, or allergens. Briefly, nasal epithelial cells obtained from human volunteers are expanded on coated tissue culture plates, and then transferred onto cell culture inserts. Upon reaching confluency, cells continue to be cultured at the air-liquid interface (ALI), for several weeks, which creates more physiologically relevant conditions. The ALI culture condition uses defined media leading to a differentiated epithelium that exhibits morphological and functional characteristics similar to the human nasal epithelium, with both ciliated and mucus producing cells. Tissue culture inserts with differentiated nasal epithelial cells can be manipulated in a variety of ways depending on the research questions (treatment with pharmacological agents, transduction with lentiviral vectors, exposure to gases, or infection with microbial agents) and analyzed for numerous different endpoints ranging from cellular and molecular pathways, functional changes, morphology, etc. In vitro models of differentiated human nasal epithelial

  19. Photoelectrochemical water splitting: optimizing interfaces and light absorption

    NARCIS (Netherlands)

    Park, S.

    2015-01-01

    In this thesis several photoelectrochemical water splitting devices based on semiconductor materials were investigated. The aim was the design, characterization, and fabrication of solar-to-fuel devices which can absorb solar light and split water to produce hydrogen.

  20. Balancing soft elasticity and low surface polarity in films of charged BSA capsules at air/fluid interface.

    Science.gov (United States)

    D, Madhumitha; Jaganathan, Maheshkumar; Dhathathreyan, Aruna; Miller, Reinhard

    2016-10-01

    Interaction between charged BSA colloids and the buffer at air/fluid interface has been studied using spread films of the capsules of the protein prepared at pH 4.5 and 7.5 (below and above the pI of BSA). Surface pressure-surface concentration plots, interfacial dilational rheology and Quartz crystal microbalance with dissipation have been used to characterize the films. The study shows that below the pI of the protein, the positively charged colloids entrain more water on the surface which leads to partial neutralization of the charges. Results suggest that the charged capsules are elastic due to the strongly adsorbed protein layers that restrict deformation and any small shape fluctuations is likely due to the distortion of the viscoelastic surface layer at pH=4.5. Capsules of BSA behave as 'soft elastic membrane' with interfacial properties lying between that of an elastic membrane and a slightly soluble diffuse capsule with low interfacial tension. Such elastic capsules would find applications in drug delivery and food colloids.

  1. Balancing soft elasticity and low surface polarity in films of charged BSA capsules at air/fluid interface.

    Science.gov (United States)

    D, Madhumitha; Jaganathan, Maheshkumar; Dhathathreyan, Aruna; Miller, Reinhard

    2016-10-01

    Interaction between charged BSA colloids and the buffer at air/fluid interface has been studied using spread films of the capsules of the protein prepared at pH 4.5 and 7.5 (below and above the pI of BSA). Surface pressure-surface concentration plots, interfacial dilational rheology and Quartz crystal microbalance with dissipation have been used to characterize the films. The study shows that below the pI of the protein, the positively charged colloids entrain more water on the surface which leads to partial neutralization of the charges. Results suggest that the charged capsules are elastic due to the strongly adsorbed protein layers that restrict deformation and any small shape fluctuations is likely due to the distortion of the viscoelastic surface layer at pH=4.5. Capsules of BSA behave as 'soft elastic membrane' with interfacial properties lying between that of an elastic membrane and a slightly soluble diffuse capsule with low interfacial tension. Such elastic capsules would find applications in drug delivery and food colloids. PMID:27318961

  2. An electrical conductivity based method of determining the particle deposition rate in air-liquid interface devices.

    Science.gov (United States)

    Wiegand, Harald; Meyer, Jörg; Kasper, Gerhard

    2015-08-01

    A new in-situ method of determining the particle deposition rate onto cell cultures inside air-liquid interface devices is described. It is based on depositing a surrogate aerosol of salt particles onto the water filled wells of a culture plate while measuring the resulting change in electrical conductivity of the solution in situ, in order to derive the accumulated particle mass. For evaluation purposes, the wells of a six-well cell culture plate were equipped with custom designed electrodes and calibrated with a series of commercially available standard solutions. After the necessary corrections prescribed by theory, the calibration resulted in an accuracy and comparability between cells of ±3% in terms of measured conductivity. The method was then applied to a specific ALI device consisting essentially of the calibrated six-well culture plate inside an electrostatic cross-flow precipitator, and tested with submicron NaCl aerosol of defined size distribution produced by nebulization of a salt solution. 2h of particle accumulation were sufficient to accumulate between 30 and 10 μg of salt per well, depending on the location in the precipitator. Resulting deposition rates varied narrowly between the wells by about 2 ng min(-1) cm(-2). Factors affecting the overall accuracy and reproducibility are discussed.

  3. Water, Air, Earth and Cosmic Radiation

    Science.gov (United States)

    Bassez, Marie-Paule

    2015-06-01

    In the context of the origin of life, rocks are considered mainly for catalysis and adsorption-desorption processes. Here it is shown how some rocks evolve in energy and might induce synthesis of molecules of biological interest. Radioactive rocks are a source of thermal energy and water radiolysis producing molecular hydrogen, H2. Mafic and ultramafic rocks evolve in water and dissolved carbon dioxide releasing thermal energy and H2. Peridotites and basalts contain ferromagnesian minerals which transform through exothermic reactions with the generation of heat. These reactions might be triggered by any heating process such as radioactive decay, hydrothermal and subduction zones or post-shock of meteorite impacts. H2 might then be generated from endothermic hydrolyses of the ferromagnesian minerals olivine and pyroxene. In both cases of mafic and radioactive rocks, production of CO might occur through high temperature hydrogenation of CO2. CO, instead of CO2, was proven to be necessary in experiments synthesizing biological-type macromolecules with a gaseous mixture of CO, N2 and H2O. In the geological context, N2 is present in the environment, and the activation source might arise from cosmic radiation and/or radionuclides. Ferromagnesian and radioactive rocks might consequently be a starting point of an hydrothermal chemical evolution towards the abiotic formation of biological molecules. The two usually separate worlds of rocks and life are shown to be connected through molecular and thermodynamic chemical evolution. This concept has been proposed earlier by the author (Bassez J Phys: Condens Matter 15:L353-L361, 2003, 2008a, 2008b; Bassez Orig Life Evol Biosph 39(3-4):223-225, 2009; Bassez et al. 2011; Bassez et al. Orig Life Evol Biosph 42(4):307-316, 2012, Bassez 2013) without thermodynamic details. This concept leads to signatures of prebiotic chemistry such as radionuclides and also iron and magnesium carbonates associated with serpentine and/or talc, which

  4. Modern methods of water and air purification from mercury

    OpenAIRE

    Dolina, L. F.; Chornaya, A. Yu.; Nagornaya, E. K.

    2015-01-01

    People can be exposed to mercury in any form in different circumstances. Depending on the amount of mercury and duration of exposure potential acute poisoning, chronic poisoning, micromercurialism. As of release into the environment (air, sediment, water), it undergoes a series of complex transformations. Methylmercury is the most highly toxic form of mercury, it is especially enhanced in the food chain. Extreme danger as contaminants in natural waters are heavy metals, have a toxic effect on...

  5. Forming Nanoparticle Monolayers at Liquid-Air Interfaces by Using Miscible Liquids.

    Science.gov (United States)

    Zhang, Datong; Hu, Jiayang; Kennedy, Kathleen M; Herman, Irving P

    2016-08-23

    One standard way of forming monolayers (MLs) of nanoparticles (NPs) is to drop-cast a NP dispersion made using one solvent onto a second, immiscible solvent; after this upper solvent evaporates, the NP ML can be transferred to a solid substrate by liftoff. We show that this previously universal use of only immiscible solvent pairs can be relaxed and close-packed, hexagonally ordered NP monolayers can self-assemble at liquid-air interfaces when some miscible solvent pairs are used instead. We demonstrate this by drop-casting an iron oxide NP dispersion in toluene on a dimethyl sulfoxide (DMSO) liquid substrate. The NPs are energetically stable at the DMSO surface and remain there even with solvent mixing. Excess NPs coagulate and precipitate in the DMSO, and this limits NPs at the surface to approximately 1 ML. The ML domains at the surface nucleate independently, which is in contrast to ML growth at the receding edge of the drying drop, as is common in immiscible solvent pair systems and seen here for the toluene/diethylene glycol immiscible solvent pair system. This new use of miscible solvent pairs can enable the formation of MLs for a wider range of NPs. PMID:27458656

  6. Characterisation of pellicles formed by Acinetobacter baumannii at the air-liquid interface.

    Directory of Open Access Journals (Sweden)

    Yassine Nait Chabane

    Full Text Available The clinical importance of Acinetobacter baumannii is partly due to its natural ability to survive in the hospital environment. This persistence may be explained by its capacity to form biofilms and, interestingly, A. baumannii can form pellicles at the air-liquid interface more readily than other less pathogenic Acinetobacter species. Pellicles from twenty-six strains were morphologically classified into three groups: I egg-shaped (27%; II ball-shaped (50%; and III irregular pellicles (23%. One strain representative of each group was further analysed by Brewster's Angle Microscopy to follow pellicle development, demonstrating that their formation did not require anchoring to a solid surface. Total carbohydrate analysis of the matrix showed three main components: Glucose, GlcNAc and Kdo. Dispersin B, an enzyme that hydrolyzes poly-N-acetylglucosamine (PNAG polysaccharide, inhibited A. baumannii pellicle formation, suggesting that this exopolysaccharide contributes to pellicle formation. Also associated with the pellicle matrix were three subunits of pili assembled by chaperon-usher systems: the major CsuA/B, A1S_1510 (presented 45% of identity with the main pilin F17-A from enterotoxigenic Escherichia coli pili and A1S_2091. The presence of both PNAG polysaccharide and pili systems in matrix of pellicles might contribute to the virulence of this emerging pathogen.

  7. Characterisation of pellicles formed by Acinetobacter baumannii at the air-liquid interface.

    Science.gov (United States)

    Nait Chabane, Yassine; Marti, Sara; Rihouey, Christophe; Alexandre, Stéphane; Hardouin, Julie; Lesouhaitier, Olivier; Vila, Jordi; Kaplan, Jeffrey B; Jouenne, Thierry; Dé, Emmanuelle

    2014-01-01

    The clinical importance of Acinetobacter baumannii is partly due to its natural ability to survive in the hospital environment. This persistence may be explained by its capacity to form biofilms and, interestingly, A. baumannii can form pellicles at the air-liquid interface more readily than other less pathogenic Acinetobacter species. Pellicles from twenty-six strains were morphologically classified into three groups: I) egg-shaped (27%); II) ball-shaped (50%); and III) irregular pellicles (23%). One strain representative of each group was further analysed by Brewster's Angle Microscopy to follow pellicle development, demonstrating that their formation did not require anchoring to a solid surface. Total carbohydrate analysis of the matrix showed three main components: Glucose, GlcNAc and Kdo. Dispersin B, an enzyme that hydrolyzes poly-N-acetylglucosamine (PNAG) polysaccharide, inhibited A. baumannii pellicle formation, suggesting that this exopolysaccharide contributes to pellicle formation. Also associated with the pellicle matrix were three subunits of pili assembled by chaperon-usher systems: the major CsuA/B, A1S_1510 (presented 45% of identity with the main pilin F17-A from enterotoxigenic Escherichia coli pili) and A1S_2091. The presence of both PNAG polysaccharide and pili systems in matrix of pellicles might contribute to the virulence of this emerging pathogen. PMID:25360550

  8. Evaluation of Nitrate and Nitrite Reduction Kinetics Related to Liquid-Air-Interface Corrosion

    International Nuclear Information System (INIS)

    Liquid-air interface (LAI) corrosion has been a concern for causing leaks in the carbon steel tanks used for holding high-level radioactive liquid waste. To assist in understanding the mechanism of LAI corrosion, the kinetics of nitrate and nitrite reduction reactions were investigated electrochemically. Cyclic voltammetry and cathodic polarization measurements indicated that the nitrite reduction reaction exhibited faster kinetics than the nitrate reduction reaction at higher cathodic overpotential. However, the primary reduction reaction at the open circuit potential under aerated conditions was the oxygen reduction reaction. The reduction of residual oxygen was also the dominant cathodic reaction at open circuit potential in deaerated conditions. Moreover, the kinetics of oxygen reduction on steel electrodes were significantly influenced by the sample immersion conditions (partial vs. full) for aerated liquid nuclear waste simulants, but not for deaerated conditions. Lastly, the gaseous products formed during LAI corrosion were analyzed using the gas detector tube method and gas chromatography-mass spectrometry and found to contain NH3, NO2 and NO. However, the results suggested that these products were caused by the local acidification generated by the hydrolysis of cations after LAI corrosion underwent extensive propagation, instead of being directly reduced in alkaline conditions. Thus, the results in this work showed that the kinetics of nitrate and nitrite reduction could not generate a salt concentration cell in the meniscus region to cause LAI corrosion

  9. Earth, Air, Fire and Water in Our Elements

    Science.gov (United States)

    Lievesley, Tara

    2007-01-01

    The idea that everything is made of the four "elements", earth, air, fire and water, goes back to the ancient Greeks. In this article, the author talks about the origins of ideas about the elements. The author provides an account that attempts to summarise thousands of years of theoretical development of the elements in a thousand words or so.

  10. Flooding velocities for air and water in vertical tubes

    International Nuclear Information System (INIS)

    An investigation of the limiting, or flooding, velocities for countercurrent annular flow of air and water in vertical tubes is reported. The data are correlated in terms of dimensionless groups which are similar to those already in use for describing flooding in packed towers. The relevance of the results to the problem of burnout in boiling equipment is discussed. (author)

  11. Solvent-Induced Proton Hopping at a Water-Oxide Interface.

    Science.gov (United States)

    Tocci, Gabriele; Michaelides, Angelos

    2014-02-01

    Despite widespread interest, a detailed understanding of the dynamics of proton transfer at interfaces is lacking. Here, we use ab initio molecular dynamics to unravel the connection between interfacial water structure and proton transfer for the widely studied and experimentally well-characterized water-ZnO(101̅0) interface. We find that upon going from a single layer of adsorbed water to a liquid multilayer, changes in the structure are accompanied by a dramatic increase in the proton-transfer rate at the surface. We show how hydrogen bonding and rather specific hydrogen-bond fluctuations at the interface are responsible for the change in the structure and proton-transfer dynamics. The implications of this for the chemical reactivity and for the modeling of complex wet oxide interfaces in general are also discussed.

  12. Heat exchange at air-sea interface in the South China Sea during monsoon periods in 1986

    Institute of Scientific and Technical Information of China (English)

    WU Disheng; LU Boming; FENG Weizhong; XU Jianping; YAN Jinghua; ZHAO Xue; ZHOU Shuihua; ZHANG Jiwei; QIAO Guanyu; LIN Fu

    2006-01-01

    In order to explore the interaction between the sea and monsoon in the South China Sea, the heat exchanges at air-sea interface during monsoon periods in 1986 were calculated using observational data. It shows that when the summer monsoon bursts and prevails over the South China Sea, the air-sea interface heat exchange is strong and the latent heat rises rapidly in the intertropical convergence zone and the tropic cyclone system near 20.49°N, 114.14°E. On May 24, 1986, the sensible heat became positive in the typhoon system. The heating exchange indicates that heat is transported from ocean to atmosphere, with major contribution of latent heat. When the summer monsoon prevails over the South China Sea and the weather is fine, even SST (sea surface temperature) is high, but sensible heat appears to be negative. The heat exchange indicates that heat is transported from atmosphere to ocean, with major contribution of short-wave radiation absorbed by sea surface and sensible heat. When summer monsoon is over and the northeast monsoon prevails over the South China Sea, the heat exchange at air-sea interface is very strong. The heating exchange shows that the ocean heats the atmosphere, with major contribution of latent heat when cold air arrives at the sea surface and the sensible heat rises to positive rapidly. Therefore it can be concluded that the heat exchange at air-sea interface is different from the SST in South China Sea. When the summer monsoon prevails over the South China Sea, the main trend is the ocean responding to the atmosphere.

  13. Stationary rotary force waves on the liquid-air core interface of a swirl atomizer

    Science.gov (United States)

    Chinn, J. J.; Cooper, D.; Yule, A. J.; Nasr, G. G.

    2016-10-01

    A one-dimensional wave equation, applicable to the waves on the surface of the air-core of a swirl atomizer is derived analytically, by analogy to the similar one-dimensional wave equation derivation for shallow-water gravity waves. In addition an analogy to the flow of water over a weir is used to produce an analytical derivation of the flow over the lip of the outlet of a swirl atomizer using the principle of maximum flow. The principle of maximum flow is substantiated by reference to continuity of the discharge in the direction of streaming. For shallow-water gravity waves, the phase velocity is the same expression as for the critical velocity over the weir. Similarly, in the present work, the wave phase velocity on the surface of the air-core is shown to be the same expression as for the critical velocity for the flow at the outlet. In addition, this wave phase velocity is shown to be the square root of the product of the radial acceleration and the liquid thickness, as analogous with the wave phase velocity for shallow water gravity waves, which is the square root of the product of the acceleration due to gravity and the water depth. The work revisits the weirs and flumes work of Binnie et al. but using a different methodology. The results corroborate with the work of Binnie. High speed video, Laser Doppler Anemometry and deflected laser beam experimental work has been carried out on an oversize Perspex (Plexiglas) swirl atomizer. Three distinctive types of waves were detected: helical striations, low amplitude random ripples and low frequency stationary waves. It is the latter wave type that is considered further in this article. The experimentally observed waves appear to be stationary upon the axially moving flow. The mathematical analysis allows for the possibility of a negative value for the phase velocity expression. Therefore the critical velocity and the wave phase velocity do indeed lead to stationary waves in the atomizer. A quantitative comparison

  14. Air and water quality monitor assessment of life support subsystems

    Science.gov (United States)

    Whitley, Ken; Carrasquillo, Robyn L.; Holder, D.; Humphries, R.

    1988-01-01

    Preprotype air revitalization and water reclamation subsystems (Mole Sieve, Sabatier, Static Feed Electrolyzer, Trace Contaminant Control, and Thermoelectric Integrated Membrane Evaporative Subsystem) were operated and tested independently and in an integrated arrangement. During each test, water and/or gas samples were taken from each subsystem so that overall subsystem performance could be determined. The overall test design and objectives for both subsystem and integrated subsystem tests were limited, and no effort was made to meet water or gas specifications. The results of chemical analyses for each of the participating subsystems are presented along with other selected samples which were analyzed for physical properties and microbiologicals.

  15. Relating water and air flow characteristics in coarse granular materials

    DEFF Research Database (Denmark)

    Andreasen, Rune Røjgaard; Canga, Eriona; Poulsen, Tjalfe Gorm;

    2013-01-01

    Water pressure drop as a function of velocity controls w 1 ater cleaning biofilter operation 2 cost. At present this relationship in biofilter materials must be determined experimentally as no 3 universal link between pressure drop, velocity and filter material properties have been established. 4...... from air flow data. The objective of this study was, therefore, to investigate if this approach is valid 8 also for coarse granular biofilter media which usually consists of much larger particles than soils. In 9 this paper the connection between the pressure drop – velocity relationships for air...... and water flow was 10 investigated using a common biofilter medium, Leca® consisting of rounded porous particles of 2 – 16 11 mm diameter. Pressure drop – velocity relations for water flow were measured for 14 different Leca ® 12 particle size fractions and compared to measurements of the pressure drop...

  16. Role of air on local water retention behavior in the shallow heterogeneous vadose zone

    Science.gov (United States)

    Sakaki, T.; Limsuwat, A.; Illangasekare, T. H.

    2009-12-01

    simple heterogeneous column. The column was packed using two sands to form three layers where the coarser sand was sandwitched by two layers of a finer sand. In each layer, soil moisture, water pressure and air pressure were monitored. The soil was initially saturated and suction at the bottom was gradually increased to induce wetting fluid drainage, and followed by a wetting cycle. In the drainage cycle, the coarse middle layer did not drain until air front reached the bottom of the top fine layer. Once the air front reached the fine-coarse interface, air was quickly pulled into the coarse layer. The results showed that the newly developed hydrophobic material showed very small time lag and captured the abrupt air pressure change in the wet soil. In the wetting cycle, we observed positive air pressure which indicated entrapment of air and its compression as wetting proceeded. This behavior cannot be evaluated properly without the rapid measurement of air pressure. The method is currently being applied in a large 2D vertical aquifer with a structured heterogeneity to investigate how air pathways are formed under various flux/temperature conditions at the soil surface.

  17. Richtmyer-Meshkov instability of a three-dimensional SF_{6}-air interface with a minimum-surface feature.

    Science.gov (United States)

    Luo, Xisheng; Guan, Ben; Si, Ting; Zhai, Zhigang; Wang, Xiansheng

    2016-01-01

    The Richmyer-Meshkov instability of a three-dimensional (3D) SF_{6}-air single-mode interface with a minimum-surface feature is investigated experimentally. The interface produced by the soap film technique is subjected to a planar shock and the evolution of the shocked interface is captured by time-resolved schlieren photography. Different from the light-heavy single-mode case, a phase inversion occurs in the shock-interface interaction and a bubblelike structure is observed behind the shocked interface, which may be ascribed to the difference in pressure perturbation at different planes. The superimposition of spikelike forward-moving jets forms a complex structure, indicating a distinctly 3D effect. Quantitatively, it is also found that the instability at the symmetry plane grows much slower than the prediction of two-dimensional linear model, but matches the extended 3D linear and nonlinear models accounting for the curvature effects. Therefore, the opposite curvatures of the 3D interface are beneficial for suppressing the growth of the instability. PMID:26871149

  18. Richtmyer-Meshkov instability of a three-dimensional SF6-air interface with a minimum-surface feature

    Science.gov (United States)

    Luo, Xisheng; Guan, Ben; Si, Ting; Zhai, Zhigang; Wang, Xiansheng

    2016-01-01

    The Richmyer-Meshkov instability of a three-dimensional (3D) SF6-air single-mode interface with a minimum-surface feature is investigated experimentally. The interface produced by the soap film technique is subjected to a planar shock and the evolution of the shocked interface is captured by time-resolved schlieren photography. Different from the light-heavy single-mode case, a phase inversion occurs in the shock-interface interaction and a bubblelike structure is observed behind the shocked interface, which may be ascribed to the difference in pressure perturbation at different planes. The superimposition of spikelike forward-moving jets forms a complex structure, indicating a distinctly 3D effect. Quantitatively, it is also found that the instability at the symmetry plane grows much slower than the prediction of two-dimensional linear model, but matches the extended 3D linear and nonlinear models accounting for the curvature effects. Therefore, the opposite curvatures of the 3D interface are beneficial for suppressing the growth of the instability.

  19. Dosimetry Modeling for Predicting Radiolytic Production at the Spent Fuel - Water Interface

    Energy Technology Data Exchange (ETDEWEB)

    Miller, William H.; Kline, Amanda J.; Hanson, Brady D.

    2006-04-30

    Modeling of the alpha, beta, and gamma dose from spent fuel as a function of particle size and fuel to water ratio was examined. These doses will be combined with modeling of G values and interactions to determine the concentration of various species formed at the fuel water interface and their affect on dissolution rates.

  20. Volume entrained in the wake of a disc intruding into an oil-water interface

    CERN Document Server

    Peters, Ivo R; Lohse, Detlef; van der Meer, Devaraj

    2016-01-01

    An object moving through a plane interface into a fluid deforms the interface in such a way that fluid from one side of the interface is entrained into the other side, a phenomenon known as Darwin's drift. We investigate this phenomenon experimentally using a disc which is started exactly at the interface of two immiscible fluids, namely oil and water. First, we observe that due to the density difference between the two fluids the deformation of the interface is influenced by gravity, and show that there exits a time window of universal behavior. Secondly, we show by comparing with boundary integral simulations that, even though the deformation is universal, our results cannot be fully explained by potential flow solutions. We attribute this difference to the starting vortex, which is created in the wake of the disc. Universal behavior is preserved, however, because the size and strength of the vortex shows the same universality as the potential flow solution.

  1. Reflection and transmission of light waves from the air-magnetoplasma interface: Spatial and angular Imbert-Fedorov shifts

    Energy Technology Data Exchange (ETDEWEB)

    Borhanian, Jafar, E-mail: borhanian@uma.ac.ir [Department of Physics, Faculty of Science, University of Mohaghegh Ardabili, P. O. Box 179, Ardabil (Iran, Islamic Republic of)

    2015-03-15

    We have investigated the reflection and transmission of an electromagnetic wave from the air-magnetoplasma interface. The reflection and transmission coefficients are obtained for an arbitrary polarized incident wave. The spatial and angular Imbert-Fedorov (IF) shifts are discussed. The numerical results are presented to study the dependence of the reflection and transmission coefficients and IF shifts on relevant parameters of the system. The plasma and wave parameters can be used to control the reflection coefficients and IF shifts.

  2. Optical Measurement of Surface Tension in a Miniaturized Air-Liquid Interface and its Application in Lung Physiology

    OpenAIRE

    C Bertocchi; Ravasio, A.; Bernet, S.; Putz, G; Dietl, P.; Haller, T.

    2005-01-01

    We have previously shown that lamellar body-like particles, the form in which pulmonary surfactant is secreted, spontaneously disintegrate when they contact an air-liquid interface, eventually creating an interfacial film. Here, we combined these studies with a new technique enabling the simultaneous and non-invasive measurement of surface tension (γ). This method is a refinement of the pendant-drop principle. A sapphire cone with a 300-μm aperture keeps the experimental fluid by virtue of su...

  3. Ciprofloxacin Is Actively Transported across Bronchial Lung Epithelial Cells Using a Calu-3 Air Interface Cell Model

    OpenAIRE

    Ong, Hui Xin; Traini, Daniela; Bebawy, Mary; Young, Paul M.

    2013-01-01

    Ciprofloxacin is a well-established broad-spectrum fluoroquinolone antibiotic that penetrates well into the lung tissues; still, the mechanisms of its transepithelial transport are unknown. The contributions of specific transporters, including multidrug efflux transporters, organic cation transporters, and organic anion-transporting polypeptide transporters, to the uptake of ciprofloxacin were investigated in vitro using an air interface bronchial epithelial model. Our results demonstrate tha...

  4. Active oil-water interfaces: buckling and deformation of oil drops by bacteria

    Science.gov (United States)

    Juarez, Gabriel; Stocker, Roman

    2014-11-01

    Bacteria are unicellular organisms that seek nutrients and energy for growth, division, and self-propulsion. Bacteria are also natural colloidal particles that attach and self-assemble at liquid-liquid interfaces. Here, we present experimental results on active oil-water interfaces that spontaneously form when bacteria accumulate or grow on the interface. Using phase-contrast and fluorescence microscopy, we simultaneously observed the dynamics of adsorbed Alcanivorax bacteria and the oil-water interface within microfluidic devices. We find that, by growing and dividing, adsorbed bacteria form a jammed monolayer of cells that encapsulates the entire oil drop. As bacteria continue to grow at the interface, the drop buckles and the interface undergoes strong deformations. The bacteria act to stabilize non-equilibrium shapes of the oil-phase such wrinkling and tubulation. In addition to presenting a natural example of a living interface, these findings shape our understanding of microbial degradation of oil and may have important repercussions on engineering interventions for oil bioremediation.

  5. Application of a laser Doppler vibrometer for air-water to subsurface signature detection

    Science.gov (United States)

    Land, Phillip; Roeder, James; Robinson, Dennis; Majumdar, Arun

    2015-05-01

    There is much interest in detecting a target and optical communications from an airborne platform to a platform submerged under water. Accurate detection and communications between underwater and aerial platforms would increase the capabilities of surface, subsurface, and air, manned and unmanned vehicles engaged in oversea and undersea activities. The technique introduced in this paper involves a Laser Doppler Vibrometer (LDV) for acousto-optic sensing for detecting acoustic information propagated towards the water surface from a submerged platform inside a 12 gallon water tank. The LDV probes and penetrates the water surface from an aerial platform to detect air-water surface interface vibrations caused by an amplifier to a speaker generating a signal generated from underneath the water surface (varied water depth from 1" to 8"), ranging between 50Hz to 5kHz. As a comparison tool, a hydrophone was used simultaneously inside the water tank for recording the acoustic signature of the signal generated between 50Hz to 5kHz. For a signal generated by a submerged platform, the LDV can detect the signal. The LDV detects the signal via surface perturbations caused by the impinging acoustic pressure field; proving a technique of transmitting/sending information/messages from a submerged platform acoustically to the surface of the water and optically receiving the information/message using the LDV, via the Doppler Effect, allowing the LDV to become a high sensitivity optical-acoustic device. The technique developed has much potential usage in commercial oceanography applications. The present work is focused on the reception of acoustic information from an object located underwater.

  6. In situ Observation of the Photochromism in the Langmuir Monolayer of a Non—typical Amphiphilic Spiropyran Derivative at the Air/Water Interface

    Institute of Scientific and Technical Information of China (English)

    贡浩飞; 唐季安; 王聪敏; 樊美公; 刘鸣华

    2003-01-01

    In situ photochromic process in the monolayer of aphotochromic spiropyran derivative without long alkyl chain,was investigated.The photochromism at the air/water interface under differnet surface pressures was studied by surface pressure-area isotherms,surface pressure-time curves,area-time curves and Brewster angle microscopy.Both forms of the compound were found to form monolayers at the air/water interface althouhg it does not have long alkyl chain.A large area expansion in the monolayer corresponding to a zreoth order reaction was found at the initial stage of the UV light irradiation.A series of dynamic investigations revealed that at high pressure after phase transition in the monolayer,the surface pressure changes greatly umder alternative irradiation of UV and visible light.An obvious morphological change accompanying with the photochromism was observed in situ.

  7. Interface diffusion and chemical reaction of PZT layer/Si(111)sample during the annealing treatment in air

    Institute of Scientific and Technical Information of China (English)

    ZHU, Yong-Fa(朱永法); CAO, Li-Li(曹立礼); YAN, Pei-Yu(阎培渝); LI, Long-Tu(李龙土); YI, Tao(易涛)

    2000-01-01

    The interface diffusion and chemical reaction between a PZT (PbZrxTi1-xO3) layer and a Si(111) substrate during the annealing treatment in air have been studied by using XPS (XRay Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy). The results indicate that the Ti element in the PZT precursor reacted with residual carbou and silicon, diffused from the Si substrate, to form TiCx, TiSix species in the PZT layer during the thermal treatment. A great interface diffusion and chemical reactiou took place on the interface of PZT/Si also. The silicon atoms diffused from silicon substrate onto the surface of PZT layer. The oxygen atoms, which came from air, diffused into silicon substrate also and reacted with Si atoms to form a SiO2 interlayer between the PZT layer and the Si (111) substrate. The thickness of SiO2 interlayer was proportional to the square root of treatment time. The formation of the SiO2 interlayer was governed by the diffusion of oxygen in the PZT layer at low annealing temperature, and governed by the diffusion of oxygen in SiO2 interlayer at high annealing temperature. The apparent activation energy of the interface oxidation reaction was about 39.1 kJ/mol.

  8. Infrared Spectroscopy of Bilberry Extract Water-in-Oil Emulsions: Sensing the Water-Oil Interface.

    Science.gov (United States)

    Kiefer, Johannes; Frank, Kerstin; Zehentbauer, Florian M; Schuchmann, Heike P

    2016-01-01

    Water-in-oil (w/o) emulsions are of great interest in many areas of the life sciences, including food technology, bioprocess engineering, and pharmaceuticals. Such emulsions are complex multi-component systems and the molecular mechanisms which lead to a stable emulsion are yet to be fully understood. In this work, attenuated total reflection (ATR) infrared (IR) spectroscopy is applied to a series of w/o emulsions of an aqueous anthocyanin-rich bilberry extract dispersed in a medium chain triglyceride (MCT) oil phase. The content of the emulsifier polyglycerin-polyricinoleat (PGPR) has been varied systematically in order to investigate whether or not its concentration has an impact on the molecular stabilization mechanisms. The molecular stabilization is accessed by a careful analysis of the IR spectrum, where changes in the vibrational frequencies and signal strengths indicate alterations of the molecular environment at the water/oil interface. The results suggest that adding emulsifier in excess of 1% by weight does not lead to an enhanced stabilization of the emulsion. PMID:27089376

  9. Infrared Spectroscopy of Bilberry Extract Water-in-Oil Emulsions: Sensing the Water-Oil Interface

    Directory of Open Access Journals (Sweden)

    Johannes Kiefer

    2016-04-01

    Full Text Available Water-in-oil (w/o emulsions are of great interest in many areas of the life sciences, including food technology, bioprocess engineering, and pharmaceuticals. Such emulsions are complex multi-component systems and the molecular mechanisms which lead to a stable emulsion are yet to be fully understood. In this work, attenuated total reflection (ATR infrared (IR spectroscopy is applied to a series of w/o emulsions of an aqueous anthocyanin-rich bilberry extract dispersed in a medium chain triglyceride (MCT oil phase. The content of the emulsifier polyglycerin-polyricinoleat (PGPR has been varied systematically in order to investigate whether or not its concentration has an impact on the molecular stabilization mechanisms. The molecular stabilization is accessed by a careful analysis of the IR spectrum, where changes in the vibrational frequencies and signal strengths indicate alterations of the molecular environment at the water/oil interface. The results suggest that adding emulsifier in excess of 1% by weight does not lead to an enhanced stabilization of the emulsion.

  10. Similarity of coupled heat and mass transfer between air-water and air-liquid desiccant direct-contact systems

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiao-Hua; Jiang, Yi [Department of Building Science, School of Architecture, Tsinghua University, Beijing 100084 (China); Li, Zhen [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2009-12-15

    Packed-bed heat and mass transfer devices are widely used in air-conditioning systems, such as cooling tower, evaporative cooler of air-water direct-contact devices, dehumidifier and regenerator of air-liquid desiccant direct-contact devices. Similarities of heat and mass transfer characteristics between air-water and air-liquid desiccant devices are considered and investigated in this paper. Same reachable handling region of outlet air can be obtained for both air-water and air-liquid desiccant devices, which is among three boundary lines, isenthalpic line of inlet air, iso-relative humidity line of inlet fluid (water or desiccant), and the connecting line of inlet statuses of air and fluid. Inlet conditions of air and fluid affect heat and mass transfer characteristics to some extent, so that a zonal method is proposed only according to the relative statuses of inlet air to inlet fluid. Four zones, dehumidification zones A, D and regeneration zones B, C, are divided for air-desiccant direct-contact devices. The first three zones A, B and C are divided for air-water direct-contact devices, with the same zonal properties as those of air-desiccant devices. In order to obtain better humidification performance, fluid should be heated (in zone C) rather than air (in zone B). And fluid should be cooled (in zone A) rather than air (in zone D) to obtain better dehumidification performance. Counter-flow pattern should be applied for best mass transfer performance in the same conditions within the recommended zone A or C, while parallel-flow pattern is the best in zone B or D. (author)

  11. LASE Measurements of Water Vapor, Aerosol, and Cloud Distributions in Saharan Air Layers and Tropical Disturbances

    Science.gov (United States)

    Ismail, Syed; Ferrare, Richard A.; Browell, Edward V.; Kooi, Susan A.; Dunion, Jason P.; Heymsfield, Gerry; Notari, Anthony; Butler, Carolyn F.; Burton, Sharon; Fenn, Marta; Krishnamurti, T. N.; Chen, Gao; Anderson, Bruce

    2010-01-01

    LASE (Lidar Atmospheric Sensing Experiment) on-board the NASA DC-8 measured high resolution profiles of water vapor and aerosols, and cloud distributions in 14 flights over the eastern North Atlantic during the NAMMA (NASA African Monsoon Multidisciplinary Analyses) field experiment. These measurements were used to study African easterly waves (AEWs), tropical cyclones (TCs), and the Saharan Air Layer(s) (SAL). Interactions between the SAL and tropical air were observed during the early stages of the TC development. These LASE measurements represent the first simultaneous water vapor and aerosol lidar measurements to study the SAL and its impact on AEWs and TCs. Examples of profile measurements of aerosol scattering ratios, aerosol extinction coefficients, aerosol optical thickness, water vapor mixing ratios, RH, and temperature are presented to illustrate their characteristics in SAL, convection, and clear air regions. LASE data suggest that the SAL suppresses low-altitude convection at the convection-SAL interface region. Mid-level convection associated with the AEW and transport are likely responsible for high water vapor content observed in the southern regions of the SAL on August 20, 2008. This interaction is responsible for the transfer of about 7 x 10(exp 15) J latent heat energy within a day to the SAL. Measurements of lidar extinction-to-backscatter ratios in the range 36+/-5 to 45+/-5 are within the range of measurements from other lidar measurements of dust. LASE aerosol extinction and water vapor profiles are validated by comparison with onboard in situ aerosol measurements and GPS dropsonde water vapor soundings, respectively.

  12. Use of Surfactants to Decrease Air-Water Interfacial Tension During Sparging

    Science.gov (United States)

    Air sparging is a remediation procedure of injecting air into polluted ground water. The primary intention of air sparging is to promote biodegradation of volatile organic compounds (VOCs) in the groundwater passing through the treatment sector. Sparging treatment efficiency dep...

  13. Use of Surfactants to Decrease Air-Water Interfacial Tension During Sparging (OKC, OK)

    Science.gov (United States)

    Air sparging is a remediation procedure of injecting air into polluted ground water. The primary intention of air sparging is to promote biodegradation of volatile organic compounds (VOCs) in the groundwater passing through the treatment sector. Sparging treatment efficiency dep...

  14. Estimating the radon concentration in water and indoor air.

    Science.gov (United States)

    Maged, A F

    2009-05-01

    The paper presents the results of radon concentration measurements in the vicinity of water, indoor air and in contact to building walls. The investigations were carried out using CR-39 track detectors. Samples of ground water flowing out of many springs mostly in Arabian Gulf area except one from Germany have been studied. The results are compared with international recommendations and the values are found to be lower than the recommended value. Measuring the mean indoor radon concentrations in air and in contact to building walls in the dwellings of Kuwait University Campus were found 24.2 +/- 7.7, and 462 +/- 422 Bq m(-3) respectively. These values lead to average effective dose equivalent rates of 1.3 +/- 0.4 and 23 +/- 21 mSv year(-1), respectively.

  15. Transport-limited water splitting at ion-selective interfaces during concentration polarization

    OpenAIRE

    Nielsen, Christoffer Peder; Bruus, Henrik

    2013-01-01

    We present an analytical model of salt- and water-ion transport across an ion-selective interface based on an assumption of local equilibrium of the water-dissociation reaction. The model yields current-voltage characteristics and curves of water-ion current versus salt-ion current, which are in qualitative agreement with experimental results published in the literature. The analytical results are furthermore in agreement with direct numerical simulations. As part of the analysis, we find app...

  16. Water percolation through the root-soil interface

    Science.gov (United States)

    Benard, Pascal; Kroener, Eva; Vontobel, Peter; Kaestner, Anders; Carminati, Andrea

    2016-04-01

    Plant roots exude a significant fraction of the carbon assimilated via photosynthesis into the soil. The mucilaginous fraction of root exudates affects the hydraulic properties of the soil near the roots, the so called rhizosphere, in a remarkable and dynamic way. After drying, mucilage becomes hydrophobic and limits the rewetting of the rhizosphere. Here, we aim to find a quantitative relation between rhizosphere rewetting, particle size, soil matric potential and mucilage concentration. We used a pore-network model in which mucilage was randomly distributed in a cubic lattice. The general idea was that the mucilage concentration per solid soil surface increases the contact angle between the liquid and solid phases consequently limiting the rewetting of pores covered with dry mucilage. We used the Young-Laplace equation to calculate the mucilage concentration at which pores are not wettable for varying particle sizes and matric potentials. Then, we simulated the percolation of water across a cubic lattice. Our simulations predicted that above a critical mucilage concentration water could not flow through the porous medium. The critical mucilage concentration decreased with increasing particle size and decreasing matric potential. The model was compared with experiments of capillary rise in soils of different particle size and mucilage concentration. The experiments confirmed the percolation behaviour of the rhizosphere rewetting. Mucilage turned hydrophobic at concentrations above 0.1 mg/cm². The critical mucilage concentration at matric potential of -2.5 hPa was ca. 1% [g/g] for fine sand and 0.1 % [g/g] for coarse sand. Our conceptual model is a first step towards a better understanding of the water dynamics in the rhizosphere during rewetting and it can be used to predict in what soil textures rhizosphere water repellency becomes a critical issue for root water uptake.

  17. Water percolation through the root-soil interface

    Science.gov (United States)

    Benard, Pascal; Kroener, Eva; Vontobel, Peter; Kaestner, Anders; Carminati, Andrea

    2016-09-01

    Plant roots exude a significant fraction of the carbon assimilated via photosynthesis into the soil. The mucilaginous fraction of root exudates affects the hydraulic properties of the soil near the roots, the so called rhizosphere, in a remarkable and dynamic way. After drying, mucilage becomes hydrophobic and limits the rewetting of the rhizosphere. Here, we aim to find a quantitative relation between rhizosphere rewetting, particle size, soil matric potential and mucilage concentration. We used a pore-network model in which mucilage was randomly distributed in a cubic lattice. The general idea was that the mucilage concentration per solid soil surface increases the contact angle between the liquid and solid phases consequently limiting the rewetting of pores covered with dry mucilage. We used the Young-Laplace equation to calculate the mucilage concentration at which pores are not wettable for varying particle sizes and matric potentials. Then, we simulated the percolation of water across a cubic lattice. Our simulations predicted that above a critical mucilage concentration water could not flow through the porous medium. The critical mucilage concentration decreased with increasing particle size and decreasing matric potential. The model was compared with experiments of capillary rise in soils of different particle size and mucilage concentration. The experiments confirmed the percolation behaviour of the rhizosphere rewetting. Mucilage turned hydrophobic at concentrations above 0.1 mg/cm2. The critical mucilage concentration at matric potential of -2.5 hPa was ca. 1% [g/g] for fine sand and 0.1 % [g/g] for coarse sand. Our conceptual model is a first step towards a better understanding of the water dynamics in the rhizosphere during rewetting and it can be used to predict in what soil textures rhizosphere water repellency becomes a critical issue for root water uptake.

  18. Fluctuations of fresh-saline water interface and of water table induced by sea tides in unconfined aquifers

    Science.gov (United States)

    Levanon, Elad; Shalev, Eyal; Yechieli, Yoseph; Gvirtzman, Haim

    2016-10-01

    This study examines effects of tides on fluctuations of the fresh-saline water interface and the groundwater level in unconfined coastal aquifers using a two-dimensional numerical model. The time-lags of the simulated hydraulic heads and salinities fluctuations compared to sea level fluctuations are analyzed using cross-correlation analysis. The results show that both the fresh-saline water interface and the groundwater level are affected harmonically by sea tide fluctuations. However, significantly different time-lags are obtained between the hydraulic head in the deeper and upper parts of the aquifer, and between head and salinity in the fresh-saline water interface. The hydraulic head in the deeper part of the aquifer responses much faster to sea level fluctuations than in the upper part. Surprisingly, a similar difference is detected between the time-lag of the hydraulic head in the fresh-saline water interface and the time-lag of the salinity at the same location. Furthermore, the time-lag of the salinity in the fresh-saline water interface is similar to the time-lag of the water table. We suggest a comprehensive mechanism for tidal influence on the coastal groundwater system, in which two main processes act simultaneously. First, sea tide causes a pressure head wave which propagates into the saturated zone of the aquifer, governed by the diffusivity of the aquifer (Ks/Ss). Second, this pressure head wave is attenuated at the water table due to the unsaturated flow within the capillary fringe which occurs during groundwater level oscillations. Because the tidal forcing acts on the sea-floor boundary and the attenuation of the groundwater level due to capillary effect acts on the groundwater table, two dimensional distributions of time-lag and hydraulic head amplitude are created. The capillary effect in the unsaturated zone plays a key role not only in the water table fluctuations as shown previously, but also on the salinity fluctuations in the fresh

  19. Dynamic modeling of an air source heat pump water heater

    OpenAIRE

    Fardoun, Farouk; Ibrahim, Oussama; Zoughaib, Assaad

    2011-01-01

    International audience This paper presents a dynamic simulation model to predict the performance of an air source heat pump water heater (ASHPWH). The mathematical model consists of submodels of the basic system components i.e. evaporator, condenser, compressor, and expansion valve. These submodels were built based on fundamental principles of heat transfer, thermodynamics, fluid mechanics, empirical relationships and manufacturer's data as necessary. The model simulation was carried out u...

  20. Geochemical Insight from Nonlinear Optical Studies of Mineral-Water Interfaces

    Science.gov (United States)

    Covert, Paul A.; Hore, Dennis K.

    2016-05-01

    The physics and chemistry of mineral-water interfaces are complex, even in idealized systems. Our need to understand this complexity is driven by both pure and applied sciences, that is, by the need for basic understanding of earth systems and for the knowledge to mitigate our influences upon them. The second-order nonlinear optical techniques of second-harmonic generation and sum-frequency generation spectroscopy have proven adept at probing these types of interfaces. This review focuses on the contributions to geochemistry made by nonlinear optical methods. The types of questions probed have included a basic description of the structure adopted by water molecules at the mineral interface, how flow and porosity affect this structure, adsorption of trace metal and organic species, and dissolution mechanisms. We also discuss directions and challenges that lie ahead and the outlook for the continued use of nonlinear optical methods for studies of mineral-water boundaries.

  1. Adsorption and rheological behavior of an amphiphilic protein at oil/water interfaces.

    Science.gov (United States)

    Richter, Marina J; Schulz, Alexander; Subkowski, Thomas; Böker, Alexander

    2016-10-01

    Hydrophobins are highly surface active proteins which self-assemble at hydrophilic-hydrophobic interfaces into amphipathic membranes. We investigate hydrophobin self-assembly at oil/water interfaces to deepen the understanding of protein behavior in order to improve our biomimetic synthesis. Therefore, we carried out pendant drop measurements of hydrophobin stabilized oil/water systems determining the time-dependent IFT and the dilatational rheology with additional adaptation to the Serrien protein model. We show that the class I hydrophobin H(∗)Protein B adsorbs at an oil/water interface where it forms a densely-packed interfacial protein layer, which dissipates energy during droplet oscillation. Furthermore, the interfacial protein layer exhibits shear thinning behavior. PMID:27388134

  2. Mechanism of temperature fluctuation phenomena below steam-water interface in a pressurizer spray pipe

    International Nuclear Information System (INIS)

    In a PWR plant, a steam-water two-phase flow may exist in the pressurizer spray pipe under a normal operating condition since the flow rate of the spray water is not sufficient to fill the horizontal section of the pipe completely. Initiation of high cycle fatigue cracks is suspected to occur under such thermally stratified two phase flow conditions. Experiments for a steam-water flow have been conducted to investigate the temperature fluctuation phenomena. It has been shown that the wall temperature fluctuations were not caused by the waves on the water surface, but were caused by temperature fluctuations in water layer below the interface. An experiment with visualization test section of rectangular pipe was conducted to investigate the temperature fluctuation mechanism in water layer in this paper. The black stripe pattern was observed below the steam-water interface due to the density change. The water temperature fluctuations had the dominant frequency of about 1Hz. The Richardson number calculated with the measured temperature and velocity gradient was larger than 0.25. The dominant frequency of temperature fluctuations was nearly equal to the Brunt-Väisälä frequency. It was shown that the temperature fluctuations in water layer below the interface were caused by the internal gravity wave in the thermal stratified flow. (author)

  3. Interfacial assembly of Graphene Oxide at oil/water and polymer/polymer interfaces

    Science.gov (United States)

    Sun, Zhiwei; Feng, Tao; Russell, Thomas

    2013-03-01

    Amphiphilic structure of graphene oxide makes it a candidate ``surfactant'' to preferentially segregate to the interface between different fluids. The affinity of graphene oxide towards different phases was tuned by grafting with polystyrene (PS-NH2) through hydrogen bonding, and its interfacial behavior, both in toluene/water and polystyrene/poly(methyl methacrylate), was studied. The surface tension of the toluene/water interface decreases in the presence of PS-NH2 grafted graphene oxide, indicating that graphene oxide flakes can be forced to the toluene/water interface when grafted with PS-NH2. Transmission electron microscopy shows that graphene oxide can even be forced into a ``jammed'' state at the water/toluene interface. In addition, polystyrene and poly(methyl methacrylate) were blended with graphene oxide, its morphology changes from island type to co-continuous structure, but the mechanism of this behavior is still not clear. These interfacial sheets may provide a model system to study buckling and crumpling behavior at interfaces.

  4. New research on bioregenerative air/water purification systems

    Science.gov (United States)

    Johnson, Anne H.; Ellender, R. D.; Watkins, Paul J.

    1991-01-01

    For the past several years, air and water purification systems have been developed and used. This technology is based on the combined activities of plants and microorganisms as they function in a natural environment. More recently, researchers have begun to address the problems associated with indoor air pollution. Various common houseplants are currently being evaluated for their abilities to reduce concentrations of volatile organic compounds (VOCS) such as formaldehyde and benzene. With development of the Space Exploration Initiative, missions will increase in duration, and problems with resupply necessitates implementation of regenerative technology. Aspects of bioregenerative technology have been included in a habitat known as the BioHome. The ultimate goal is to use this technology in conjunction with physicochemical systems for air and water purification within closed systems. This study continued the risk assessment of bioregenerative technology with emphasis on biological hazards. In an effort to evaluate the risk for human infection, analyses were directed at enumeration of fecal streptococci and enteric viruses with the BioHome waste water treatment system.

  5. The exchange of SVOCs across the air-sea interface in Singapore's coastal environment

    Directory of Open Access Journals (Sweden)

    J. He

    2010-02-01

    Full Text Available Coastal areas are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs, OCPs and PCBs from atmospheric inputs. Dry particulate and wet depositions, and air-water diffusive exchange in the Singapore's south coastal area, where most of chemical and oil refinery industries are situated in, were estimated. Based on a yearly dataset, the mean annual dry particulate deposition fluxes of ∑16-PAHs, ∑7 OCPs and ∑21 PCBs were 1328.8±961.1 μg m−2 y−1, 5421.4±3426.7 ng m−2 y−1 and 811.8±578.3 ng m−2 y−1, and the wet deposition of ∑16-PAHs and ∑7 OCPs were 6667.1±1745.2 and 115.4±98.3 μg m−2 y−1, respectively. Seasonal variation of atmospheric depositions was influenced by meteorological conditions. Air-water gas exchange fluxes were shown to be negative values for PAHs, HCHs and DDXs, indicating Singapore's south coast as a sink for the above-mentioned SVOCs. The relative contribution of each depositional process to the total atmospheric input was assessed by annual fluxes. The profile of dry particulate deposition, wet deposition and gas exchange fluxes seemed to be correlated with individual pollutant's properties such as molecular weight and Henry's law constant, etc. For the water column partitioning, the organic carbon-normalized partition coefficients between particulate and dissolved phases (KOC for both PAHs and OCPs were obtained. The relationships between KOC of PAHs and OCPs and their respective octanol-water partition coefficient (KOW were examined. In addition, both adsorption onto combustion-derived soot carbon and absorption into natural organic matter for PAHs in marine water column were investigated. Enrichment factors in the sea-surface microlayer (SML of the particulate phase were 1.2

  6. Air-sea heat exchange, an element of the water cycle

    Science.gov (United States)

    Chahine, M. T.

    1984-01-01

    The distribution and variation of water vapor, clouds and precipitation are examined. Principal driving forces for these distributions are energy exchange and evaporation at the air-sea interface, which are also important elements of air-sea interaction studies. The overall aim of air-sea interaction studies is to quantitatively determine mass, momentum and energy fluxes, with the goal of understanding the mechanisms controlling them. The results of general circulation simulations indicate that the atmosphere in mid-latitudes responds to changes in the oceanic surface conditions in the tropics. This correlation reflects the strong interaction between tropical and mid-latitude conditions caused by the transport of heat and momentum from the tropics. Studies of air-sea exchanges involve a large number of physica, chemical and dynamical processes including heat flux, radiation, sea-surface temperature, precipitation, winds and ocean currents. The fluxes of latent heat are studied and the potential use of satellite data in determining them evaluated. Alternative ways of inferring heat fluxes will be considered.

  7. Energy and air emission effects of water supply.

    Science.gov (United States)

    Stokes, Jennifer R; Horvath, Arpad

    2009-04-15

    Life-cycle air emission effects of supplying water are explored using a hybrid life-cycle assessment For the typically sized U.S. utility analyzed, recycled water is preferable to desalination and comparable to importation. Seawater desalination has an energy and air emission footprint that is 1.5-2.4 times larger than that of imported water. However, some desalination modes fare better; brackish groundwater is 53-66% as environmentally intensive as seawater desalination. The annual water needs (326 m3) of a typical Californian that is met with imported water requires 5.8 GJ of energy and creates 360 kg of CO2 equivalent emissions. With seawater desalination, energy use would increase to 14 GJ and 800 kg of CO2 equivalent emissions. Meeting the water demand of California with desalination would consume 52% of the state's electricity. Supply options were reassessed using alternative electricity mixes, including the average mix of the United States and several renewable sources. Desalination using solar thermal energy has lower greenhouse gas emissions than that of imported and recycled water (using California's electricity mix), but using the U.S. mix increases the environmental footprint by 1.5 times. A comparison with a more energy-intensive international scenario shows that CO2 equivalent emissions for desalination in Dubai are 1.6 times larger than in California. The methods, decision support tool (WEST), and results of this study should persuade decision makers to make informed water policy choices by including energy consumption and material use effects in the decision-making process.

  8. Energy and air emission effects of water supply.

    Science.gov (United States)

    Stokes, Jennifer R; Horvath, Arpad

    2009-04-15

    Life-cycle air emission effects of supplying water are explored using a hybrid life-cycle assessment For the typically sized U.S. utility analyzed, recycled water is preferable to desalination and comparable to importation. Seawater desalination has an energy and air emission footprint that is 1.5-2.4 times larger than that of imported water. However, some desalination modes fare better; brackish groundwater is 53-66% as environmentally intensive as seawater desalination. The annual water needs (326 m3) of a typical Californian that is met with imported water requires 5.8 GJ of energy and creates 360 kg of CO2 equivalent emissions. With seawater desalination, energy use would increase to 14 GJ and 800 kg of CO2 equivalent emissions. Meeting the water demand of California with desalination would consume 52% of the state's electricity. Supply options were reassessed using alternative electricity mixes, including the average mix of the United States and several renewable sources. Desalination using solar thermal energy has lower greenhouse gas emissions than that of imported and recycled water (using California's electricity mix), but using the U.S. mix increases the environmental footprint by 1.5 times. A comparison with a more energy-intensive international scenario shows that CO2 equivalent emissions for desalination in Dubai are 1.6 times larger than in California. The methods, decision support tool (WEST), and results of this study should persuade decision makers to make informed water policy choices by including energy consumption and material use effects in the decision-making process. PMID:19475934

  9. AirSWOT: An Airborne Platform for Surface Water Monitoring

    Science.gov (United States)

    Rodriguez, E.; Moller, D.; Smith, L. C.; Pavelsky, T. M.; Alsdorf, D. E.

    2010-12-01

    The SWOT mission, expected to launch in 2020, will provide global measurements of surface water extent and elevation from which storage change and discharge can be derived. SWOT-like measurements are not routinely used by the hydrology community, and their optimal use and associated errors are areas of active research. The purpose of AirSWOT, a system that has been proposed to NASA’s Instrument Incubator Program, is to provide SWOT-like measurements to the hydrology and ocean community to be used to advance the understanding and use of SWOT data in the pre-launch phase. In the post-launch phase, AirSWOT will be used as the SWOT calibration/validation platform. The AirSWOT payload will consist of Kaspar, a multi-beam Ka-band radar interferometer able to produce elevations over a 5 km swath with centimetric precision. The absolute elevation accuracy of the AirSWOT system will be achieved with a combination of high precision Inertial Motion Units (IMUs), ground calibration points, and advanced calibration techniques utilizing a priori knowledge. It is expected that the accuracy of AirSWOT will exceed or match SWOT’s accuracy requirements. In addition to elevation measurements, the AirSWOT payload will include a near-infrared camera able to provide coincident high-resolution optical imagery of the water bodies imaged by the radar. In its initial hydrology deployments, AirSWOT will investigate four field sites: the Ohio-Mississippi confluence, the lower Atchafalaya River on the Mississippi River Delta, the Yukon River basin near Fairbanks, and the Sacramento River, California. The Ohio-Mississippi confluence is targeted for its large discharge, modest slope, and control structures that modulate Ohio but not Mississippi River slopes and elevations. The lower Atchafalaya River includes low slopes, wetlands with differing vegetation types, and some open lakes. Vegetation includes Cyprus forests, floating macrophytes, and grass marshes, all of which impact radar returns

  10. The Silica-Water Interface from the Analysis of Molecular Dynamic Simulations

    KAUST Repository

    Lardhi, Sheikha F.

    2013-05-01

    Surface chemistry is an emerging field that can give detailed insight about the elec- tronic properties and the interaction of complex material surfaces with their neigh- bors. This is for both solid-solid and solid-liquid interfaces. Among the latter class, the silica-water interface plays a major role in nature. Silica is among the most abundant materials on earth, as well in advanced technological applications such as catalysis and nanotechnology. This immediately indicates the relevance of a detailed understanding of the silica-water interface. In this study, we investigate the details of this interaction at microscopic level by analyzing trajectories obtained with ab initio molecular dynamic simulations. The system we consider consists of bulk liquid water confined between two β-cristobalite silica surfaces. The molecular dynamics were generated with the CP2K, an ab initio molecular dynamic simulation tool. The simulations are 25 picoseconds long, and the CP2K program was run on 64 cores on a supercomputer cluster. During the simulations the program integrates Newton’s equations of motion for the system and generates the trajectory for analysis. For analysis, we focused on the following properties that characterize the silica water interface. We calculated the density profile of the water layers from the silica surface, and we also calculated the radial distribution function (RDF) of the hydrogen bond at the silanols on the silica surface. The main focus of this thesis is to write the programs for calculating the atom density profile and the RDF from the generated MD trajectories. The atomic probability density profile shows that water is strongly adsorbed on the (001) cristobalite surface, while the RDF indicates differently ad- sorbed water molecules in the first adsorption layer. As final remark, the protocol and the tools developed in this thesis can be applied to the study of basically any crystal-water interface.

  11. Surface Mechanical and Rheological Behaviors of Biocompatible Poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) and Poly((D,L-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL-PEG) Block Copolymers at the Air-Water Interface.

    Science.gov (United States)

    Kim, Hyun Chang; Lee, Hoyoung; Khetan, Jawahar; Won, You-Yeon

    2015-12-29

    Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a nonglassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG isotherm behavior. Upon cessation of compression, the high surface pressure of the PLGA-PEG monolayer typically relaxes over time with a stretched exponential decay, suggesting that in this diblock copolymer situation, the hydrophobic domain formed by the PLGA blocks undergoes glass transition in the high lateral compression state, analogously to the PLGA homopolymer monolayer. In the high PEG grafting density regime, the contribution of the PEG brush chains to the high monolayer surface pressure is significantly lower than what is predicted by the SCF model because of the many-body attraction among PEG segments (referred to in the literature as the "n-cluster" effects). The end-grafted PEG chains were found to be protein resistant even under the influence of the "n-cluster" effects.

  12. Hole localization, water dissociation mechanisms, and band alignment at aqueous-titania interfaces

    Science.gov (United States)

    Lyons, John L.

    Photocatalytic water splitting is a promising method for generating clean energy, but materials that can efficiently act as photocatalysts are scarce. This is in part due to the fact that exposure to water can strongly alter semiconductor surfaces and therefore photocatalyst performance. Many materials are not stable in aqueous environments; in other cases, local changes in structure may occur, affecting energy-level alignment. Even in the simplest case, dynamic fluctuations modify the organization of interface water. Accounting for such effects requires knowledge of the dominant local structural motifs and also accurate semiconductor band-edge positions, making quantitative prediction of energy-level alignments computationally challenging. Here we employ a combined theoretical approach to study the structure, energy alignment, and hole localization at aqueous-titania interfaces. We calculate the explicit aqueous-semiconductor interface using ab initio molecular dynamics, which provides the fluctuating atomic structure, the extent of water dissociation, and the resulting electrostatic potential. For both anatase and rutile TiO2 we observe spontaneous water dissociation and re-association events that occur via distinct mechanisms. We also find a higher-density water layer occurring on anatase. In both cases, we find that the second monolayer of water plays a crucial role in controlling the extent of water dissociation. Using hybrid functional calculations, we then investigate the propensity for dissociated waters to stabilize photo-excited carriers, and compare the results of rutile and anatase aqueous interfaces. Finally, we use the GW approach from many-body perturbation theory to obtain the position of semiconductor band edges relative to the occupied 1b1 level and thus the redox levels of water, and examine how local structural modifications affect these offsets. This work was performed in collaboration with N. Kharche, M. Z. Ertem, J. T. Muckerman, and M. S

  13. Hydrated goethite (alpha-FeOOH) (100) interface structure: Ordered water and surface functional groups.

    Energy Technology Data Exchange (ETDEWEB)

    Ghose, S.K.; Waychunas, G.A.; Trainor, T.P.; Eng, P.J.

    2009-12-15

    Goethite({alpha}-FeOOH), an abundant and highly reactive iron oxyhydroxide mineral, has been the subject of numerous stud-ies of environmental interface reactivity. However, such studies have been hampered by the lack of experimental constraints on aqueous interface structure, and especially of the surface water molecular arrangements. Structural information of this type is crucial because reactivity is dictated by the nature of the surface functional groups and the structure or distribution of water and electrolyte at the solid-solution interface. In this study we have investigated the goethite(100) surface using surface diffraction techniques, and have determined the relaxed surface structure, the surface functional groups, and the three dimensional nature of two distinct sorbed water layers. The crystal truncation rod (CTR) results show that the interface structure consists of a double hydroxyl, double water terminated interface with significant atom relaxations. Further, the double hydroxyl terminated surface dominates with an 89% contribution having a chiral subdomain structure on the(100) cleavage faces. The proposed interface stoichiometry is ((H{sub 2}O)-(H{sub 2}O)-OH{sub 2}-OH-Fe-O-O-Fe-R) with two types of terminal hydroxyls; a bidentate (B-type) hydroxo group and a monodentate (A-type) aquo group. Using the bond-valence approach the protonation states of the terminal hydroxyls are predicted to be OH type (bidentate hydroxyl with oxygen coupled to two Fe{sup 3+} ions) and OH{sub 2} type (monodentate hydroxyl with oxygen tied to only one Fe{sup 3+}). A double layer three dimensional ordered water structure at the interface was determined from refinement of fits to the experimental data. Application of bond-valence constraints to the terminal hydroxyls with appropriate rotation of the water dipole moments allowed a plausible dipole orientation model as predicted. The structural results are discussed in terms of protonation and H-bonding at the interface

  14. Growth of gravity-capillary waves in countercurrent air/water turbulence

    Science.gov (United States)

    Soldati, Alfredo; Zonta, Francesco; Onorato, Miguel

    2015-11-01

    We use Direct Numerical Simulation (DNS) of the Navier Stokes equations to analyze the dynamics of the interface between air and water when both phases are driven by opposite pressure gradients (countercurrent configuration). The Reynolds number (Reτ), the Weber number (We) and the Froude number (Fr) fully describe the physical problem. We examine the problem of the transient growth of interface waves for different combinations of physical parameters. Keeping Reτ constant and varying We and Fr , we show that, in the initial stages of the wave generation process, the amplitude of the interface elevation η grows in time as η ~t 2 / 5 . Wavenumber spectra, E (kx) , of the surface elevation in the capillary range are in good agreement with the prediction of the Wave Turbulence Theory. Finally, the wave-induced modification of the average wind and current velocity profiles will be addressed. Support from Regione Autonoma Friuli Venezia Giulia under grant PAR FSC 2007/2013 is gratefully acknowledged.

  15. Experimental investigation of air bubble flows in a water pool

    International Nuclear Information System (INIS)

    This paper presents experimental results on rising bubbles in the wetwell of a boiling water reactor (BWR) in a loss-of-coolant accident in the pressure suppression pool (PSP). This accident scenario includes three processes: blowdown and associated water slug phenomena, bubble dynamics and related water flow during continuous release of gases and development of a thermal stratification. The paper covers the middle phase where air is fed through a downcomer. The developments of bubble formation and bubble flow are investigated by means of high speed videos. Diameter, velocity, formation frequency and breakup distance of bubbles are evaluated using automated image evaluation procedures. The experiments have been performed in the cylindrical vessel of the THAI test facility with a height of 9.2 m and a diameter of 3.2 m. (author)

  16. Anomalous change in interfacial tension induced by collapses of AOT microemulsions at heptane/water interface

    Science.gov (United States)

    Takahashi, Masahiko; Yui, Hiroharu; Ikezoe, Yasuhiro; Sawada, Tsuguo

    2004-05-01

    Dynamic behavior of water-in-oil microemulsions at the oil/water interface was investigated using the quasi-elastic laser scattering method. We observed an anomalous rebound behavior of interfacial tension γ induced by collapses of microemulsions and adsorptions of AOT molecules at the interface. γ rapidly decreased and reached a minimum value (5.5 mN/m) at about 500 s after the preparation of the interface, and then increased gradually for about 2000 s to the equilibrium value (8.0 mN/m). We considered the mechanism of the rebound behavior in terms of transient change in interfacial thickness induced by the collapses of AOT microemulsions.

  17. "Phantom ion effect" and the contact potential of the water-vapor interface.

    Science.gov (United States)

    Levin, Yan

    2008-09-28

    The contact (junction) potential between water-vapor and water-oil interfaces is studied theoretically. Unlike the previous studies, we show that ionic contribution to the contact potential vanishes when the concentration of aqueous electrolyte goes to zero. The incorrect prediction of a large ionic contribution to the junction potential in the infinite dilution limit, obtained in the earlier studies, is traced back to the inappropriate use of the grand-canonical ensemble for strongly inhomogeneous Coulomb systems. It is shown that for these systems, the thermodynamic limit is not reached even when the number of particles is astronomically large, on the order of 10(24). There is, therefore, no equivalence between statistical ensembles. For realistic, finite size systems, canonical calculation predicts a vanishing ionic contribution to the junction potentials of water-vapor and water-oil interfaces even for very concentrated electrolyte solutions.

  18. Characterization of spherical domains at the polystyrene thin film–water interface

    Science.gov (United States)

    Ahmad, Khurshid; Zhao, Xuezeng; Hussain, Danish

    2016-01-01

    Summary Spherical domains that readily form at the polystyrene (PS)–water interface were studied and characterized using atomic force microscopy (AFM). The study showed that these domains have similar characteristics to micro- and nanobubbles, such as a spherical shape, smaller contact angle, low line tension, and they exhibit phase contrast and the coalescence phenomenon. However, their insensitivity to lateral force, absence of long-range hydrophobic attraction, and the presence of possible contaminants and scratches on these domains suggested that these objects are most likely blisters formed by the stretched PS film. Furthermore, the analysis of the PS film before and after contact with water suggested that the film stretches and deforms after being exposed to water. The permeation of water at the PS–silicon interface, caused by osmosis or defects present on the film, can be a reasonable explanation for the nucleation of these spherical domains. PMID:27335748

  19. Thermal Interface Evaluation of Heat Transfer from a Pumped Loop to Titanium-Water Thermosyphons

    Science.gov (United States)

    Jaworske, Donald A.; Sanzi, James L.; Gibson, Marc A.; Sechkar, Edward A.

    2009-01-01

    Titanium-water thermosyphons are being considered for use in the heat rejection system for lunar outpost fission surface power. Key to their use is heat transfer between a closed loop heat source and the heat pipe evaporators. This work describes laboratory testing of several interfaces that were evaluated for their thermal performance characteristics, in the temperature range of 350 to 400 K, utilizing a water closed loop heat source and multiple thermosyphon evaporator geometries. A gas gap calorimeter was used to measure heat flow at steady state. Thermocouples in the closed loop heat source and on the evaporator were used to measure thermal conductance. The interfaces were in two generic categories, those immersed in the water closed loop heat source and those clamped to the water closed loop heat source with differing thermal conductive agents. In general, immersed evaporators showed better overall performance than their clamped counterparts. Selected clamped evaporator geometries offered promise.

  20. Molecular dynamics study of two-dimensional sum frequency generation spectra at vapor/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Ishiyama, Tatsuya, E-mail: ishiyama@eng.u-toyama.ac.jp [Department of Applied Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555 (Japan); Morita, Akihiro, E-mail: morita@m.tohoku.ac.jp [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan and Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8520 (Japan); Tahara, Tahei [Molecular Spectroscopy Laboratory, RIKEN and Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako 351-0198 (Japan)

    2015-06-07

    Two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) spectra at vapor/water interface were studied by molecular dynamics (MD) simulation with a classical flexible and nonpolarizable model. The present model well describes the spectral diffusion of 2D infrared spectrum of bulk water as well as 2D HD-VSFG at the interface. The effect of isotopic dilution on the 2D HD-VSFG was elucidated by comparing the normal (H{sub 2}O) water and HOD water. We further performed decomposition analysis of 2D HD-VSFG into the hydrogen-bonding and the dangling (or free) OH vibrations, and thereby disentangled the different spectral responses and spectral diffusion in the 2D HD-VSFG. The present MD simulation demonstrated the role of anharmonic coupling between these modes on the cross peak in the 2D HD-VSFG spectrum.

  1. Characterization of mineral-solution interface and its implications for water-rock interactions

    International Nuclear Information System (INIS)

    Olivine-water interface under hydrothermal conditions (600-790degC, 1kb) are characterized by SEM, XPS and hydrogen depth profiling using nuclear reaction. The near surface region is rich in H and depleted with Mg. The chemical shift of XPS peaks indicates structural reconstruction at the near surface. The present results and the previous studied indicate the formation of the hydrogen rich surface layer depends on various factors including mineral structure, solution composition and temperature. It is correlated with dissolution rate. Probably, permeation of water into mineral through defects or micropore space and diffusion in the permeating water are important processes in water-rock interactions. (author)

  2. Biodiversity links above and below the marine sediment-water interface that may influence community stability

    NARCIS (Netherlands)

    Austen, M.C.; Lambshead, P.J.D.; Hutchings, P.; Boucher, G.; Snelgrove, P.V.R.; Heip, C.H.R.; King, G.; Koike, I.; Smith, C.

    2002-01-01

    Linkages across the sediment-water interface (SWI) between biodiversity and community stability appear to exist but are very poorly studied. Processes by which changes in biodiversity could affect stability on the other side of the SWI include carbon transfer during feeding, decomposition of organic

  3. Modeling Nitrogen Fate and Transport at the Sediment-Water Interface

    Science.gov (United States)

    Diffusive mass transfer at media interfaces exerts control on the fate and transport of pollutants originating from agricultural and urban landscapes and affects the con-ditions of water bodies. Diffusion is essentially a physical process affecting the distribution and fate of va...

  4. Atomic-Scale Analysis of the RuO2/Water Interface under Electrochemical Conditions

    DEFF Research Database (Denmark)

    Watanabe, Eriko; Rossmeisl, Jan; Björketun, Mårten;

    2016-01-01

    The structure of the interface between ruthenium oxide and water was examined using density functional theory calculations for a range of pH and electrode potential values, and the results were summarized in a surface Pourbaix diagram. The results indicate that pH affects the interfacial structur...

  5. Surface-water interface induces conformational changes critical for protein adsorption: Implications for monolayer formation of EAS hydrophobin

    Directory of Open Access Journals (Sweden)

    Kamron eLey

    2015-11-01

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

  6. A simplified physically-based model to calculate surface water temperature of lakes from air temperature in climate change scenarios

    Science.gov (United States)

    Piccolroaz, S.; Toffolon, M.

    2012-12-01

    Modifications of water temperature are crucial for the ecology of lakes, but long-term analyses are not usually able to provide reliable estimations. This is particularly true for climate change studies based on Global Circulation Models, whose mesh size is normally too coarse for explicitly including even some of the biggest lakes on Earth. On the other hand, modeled predictions of air temperature changes are more reliable, and long-term, high-resolution air temperature observational datasets are more available than water temperature measurements. For these reasons, air temperature series are often used to obtain some information about the surface temperature of water bodies. In order to do that, it is common to exploit regression models, but they are questionable especially when it is necessary to extrapolate current trends beyond maximum (or minimum) measured temperatures. Moreover, water temperature is influenced by a variety of processes of heat exchange across the lake surface and by the thermal inertia of the water mass, which also causes an annual hysteresis cycle between air and water temperatures that is hard to consider in regressions. In this work we propose a simplified, physically-based model for the estimation of the epilimnetic temperature in lakes. Starting from the zero-dimensional heat budget, we derive a simplified first-order differential equation for water temperature, primarily forced by a seasonally varying external term (mainly related to solar radiation) and an exchange term explicitly depending on the difference between air and water temperatures. Assuming annual sinusoidal cycles of the main heat flux components at the atmosphere-lake interface, eight parameters (some of them can be disregarded, though) are identified, which can be calibrated if two temporal series of air and water temperature are available. We note that such a calibration is supported by the physical interpretation of the parameters, which provide good initial

  7. A Reactive Molecular Dynamics Simulation Of The Silica-Water Interface

    OpenAIRE

    Fogarty, Joseph C.; Aktulga, Hasan Metin; Grama, Ananth Y.; van Duin, Adri C. T.; Pandit, Sagar A.

    2010-01-01

    We report our study of a silica-water interface using reactive molecular dynamics. This first-of-its-kind simulation achieves length and time scales required to investigate the detailed chemistry of the system. Our molecular dynamics approach is based on the ReaxFF force field of van Duin [J. Phys. Chem. A 107, 3803 (2003)]. The specific ReaxFF implementation (SERIALREAX) and force fields are first validated on structural properties of pure silica and water systems. Chemical reactions between...

  8. Modeling the Assembly of Polymer-Grafted Nanoparticles at Oil-Water Interfaces.

    Science.gov (United States)

    Yong, Xin

    2015-10-27

    Using dissipative particle dynamics (DPD), I model the interfacial adsorption and self-assembly of polymer-grafted nanoparticles at a planar oil-water interface. The amphiphilic core-shell nanoparticles irreversibly adsorb to the interface and create a monolayer covering the interface. The polymer chains of the adsorbed nanoparticles are significantly deformed by surface tension to conform to the interface. I quantitatively characterize the properties of the particle-laden interface and the structure of the monolayer in detail at different surface coverages. I observe that the monolayer of particles grafted with long polymer chains undergoes an intriguing liquid-crystalline-amorphous phase transition in which the relationship between the monolayer structure and the surface tension/pressure of the interface is elucidated. Moreover, my results indicate that the amorphous state at high surface coverage is induced by the anisotropic distribution of the randomly grafted chains on each particle core, which leads to noncircular in-plane morphology formed under excluded volume effects. These studies provide a fundamental understanding of the interfacial behavior of polymer-grafted nanoparticles for achieving complete control of the adsorption and subsequent self-assembly. PMID:26439456

  9. Volume entrained in the wake of a disk intruding into an oil-water interface

    Science.gov (United States)

    Peters, Ivo R.; Madonia, Matteo; Lohse, Detlef; van der Meer, Devaraj

    2016-07-01

    An object moving through a plane interface into a fluid deforms the interface in such a way that fluid from one side of the interface is entrained into the other side, a phenomenon known as Darwin's drift. We investigate this phenomenon experimentally using a disk which is started exactly at the interface of two immiscible fluids, namely, oil and water. First, we observe that due to the density difference between the two fluids the deformation of the interface is influenced by gravity and show that there exists a time window of universal behavior. Second, we show by comparing with boundary integral simulations that, even though the deformation is universal, our results cannot be fully explained by potential flow solutions. We attribute this difference to the starting vortex, which is created in the wake of the disk. Besides contributing significantly to entrainment directly, the vortex also influences the interface deformation due to Darwin's drift. Universal behavior is preserved, however, because the size and strength of the vortex shows the same universality as the potential flow solution.

  10. Computer simulation of partitioning of ten pentapeptides Ace-WLXLL at the cyclohexane/water and phospholipid/water interfaces

    Directory of Open Access Journals (Sweden)

    Aliste Marcela P

    2005-12-01

    Full Text Available Abstract Background Peptide-membrane interactions play a key role in the binding, partitioning and folding of membrane proteins, the activity of antimicrobial and fusion peptides, and a number of other processes. To gain a better understanding of the thermodynamics of such interactions, White and Wimley created an interfacial hydrophobicity scale based of the transfer free energy from water to octanol or lipid bilayers of a series of synthetic peptapeptides (Ace-WLXLL, with X being any of the twenty natural amino acids (White and Wimley (1996 Nat. Struct. Biol. 3, 842–848. In this study, we performed molecular dynamics simulations of a representative set of ten of these peptides (X = D, K, R, N, A, T, S, I, F and W in two membrane mimetic interfaces: water-cyclohexane (10 ns and a fully solvated dioleoylphosphatidylcholine (DOPC bilayer (50 ns using both constant pressure and constant area ensembles. We focus on partitioning of the ten peptides at the cyclohexane/water and lipid/water interfaces. Results The peptides rapidly equilibrate (2 and simulations at constant pressure that approximately yield the same average area of 0.66 nm2. Conclusion These peptides were designed to assume extended conformations, which is confirmed by the simulations. The distribution of the X3 side chain depends on its nature, and can be determined from molecular dynamics simulations. The time scale of peptide motion at a phospholipids-water interface is too long to directly calculate the experimentally measured hydrophobicity scale to test and improve the simulation parameters. This should be possible at the water/cyclohexane interface and likely will become feasible in the future for the phospholipids/water case.

  11. Effect of bovine serum albumin on the functionality and structure of catanionic surfactant at air-buffer interface

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, Kajari; Bhattacharya, Subhash C.; Moulik, Satya P. [Centre for Surface Science, Department of Chemistry, Jadavpur University, Kolkata 700 032 (India); Panda, Amiya K., E-mail: akpanda1@yahoo.com [Department of Chemistry, University of North Bengal, Darjeeling 734 013 (India)

    2013-03-01

    Interaction of bovine serum albumin (BSA) with the solvent spread monolayer of a catanionic surfactant, octadecyltrimethylammonium dodecylsulfate, (C{sub 18}TA{sup +}DS{sup -}) at the air-buffer interface was investigated by measuring the surface pressure with time and change in surface area. Dipalmitoylphosphatidylcholine (DPPC) was used as reference. Kinetics of BSA desorption from the interface to the buffer subphase, that of C{sub 18}TA{sup +}DS{sup -} and DPPC through their interaction with BSA, were also studied at different BSA concentrations (in the subphase) and surface pressures. Surface pressure ({pi})-area (A) isotherms (at pH = 5.4, {mu} = 0.01, T = 298 K) revealed that the coacervate/DPPC monolayer becomes expanded in the presence of BSA at low {pi} while their protein bound species are released into the subphase at high {pi}. Film morphology, studied by epifluorescence microscopy (EFM) and atomic force microscopy (AFM), reveals that the sizes of the domains of both DPPC and coacervate decrease in the presence of BSA. Presence of BSA in the coacervate and DPPC monolayer was supported from AFM data analysis. Highlights: Black-Right-Pointing-Pointer Effect of BSA on the functionality and structure of C{sub 18}TA{sup +}DS{sup -}/DPPC at the air-buffer interface was studied. Black-Right-Pointing-Pointer BSA molecules coadsorb at lower surface pressure, while they abstract amphiphiles at higher surface pressure into the bulk. Black-Right-Pointing-Pointer Kinetic studies of adsorption/desorption of BSA at/from the interface were performed. Black-Right-Pointing-Pointer Organized amphiphiles are perturbed in the presence of BSA.

  12. Hydroxynitrile lyase at the diisopropyl ether/water interface: Evidence for interfacial enzyme activity

    Energy Technology Data Exchange (ETDEWEB)

    Hichel, A.; Radke, C.J.; Blanch, H.W. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

    1999-11-20

    A novel recycle reactor has been designed to determine the interfacial activity of hydroxynitrile lyase in a diisopropyl ether (DIPE)/water two-phase system. The reactor provides a known interfacial area. Enzyme activity toward mandelonitrile cleavage is continuously measured in the reactor by following benzaldehyde product formation in the DIPE organic phase with an optical flow cell. For the first time, the authors establish that this enzymatic reaction is carried out by the hydroxynitrile lyase residing at the organic solvent/water interface and not in the aqueous bulk phase. Hydroxynitrile lyase adsorbs at the interface and exhibits extraordinary stability. Denaturation does not occur over several hours, although the surface pressure increases under the same conditions over this time span. Increases in surface pressure indicate enzyme penetration through the interface although no loss of enzyme activity is observed. Adsorption of p-Hnl at the interface is fit by the Langmuir equilibrium adsorption model with an adsorption equilibrium constant of 0.032 L mg{sup {minus}1}. For the mandelonitrile cleavage reaction at ambient temperature, p-Hnl follows Michaelis-Menten kinetics at the interface with a Michaelis constant of 14.4 mM and a specific activity close that for the bulk aqueous phase.

  13. Micrometeorological Measurement of Fetch- and Atmospheric Stability-Dependent Air- Water Exchange of Legacy Semivolatile Organic Contaminants in Lake Superior

    Science.gov (United States)

    Perlinger, J. A.; Tobias, D. E.; Rowe, M. D.

    2008-12-01

    Coastal waters including the Laurentian Great Lakes are particularly susceptible to local, regional, and long- range transport and deposition of semivolatile organic contaminants (SOCs) as gases and/or associated with particles. Recently-marketed SOCs can be expected to undergo net deposition in surface waters, whereas legacy SOCs such as polychlorinated biphenyls (PCBs) are likely to be at equilibrium with respect to air-water exchange, or, if atmospheric concentrations decrease through, e.g., policy implementation, to undergo net gas emission. SOC air-water exchange flux is usually estimated using the two-film model. This model describes molecular diffusion through the air and water films adjacent to the air-water interface. Air-water exchange flux is estimated as the product of SOC fugacity, typically based on on-shore gaseous concentration measurements, and a transfer coefficient, the latter which is estimated from SOC properties and environmental conditions. The transfer coefficient formulation commonly applied neglects resistance to exchange in the internal boundary layer under atmospherically stable conditions, and the use of on-shore gaseous concentration neglects fetch-dependent equilibration, both of which will tend to cause overestimation of flux magnitude. Thus, for legacy chemicals or in any highly contaminated surface water, the rate at which the water is cleansed through gas emission tends to be over-predicted using this approach. Micrometeorological measurement of air-water exchange rates of legacy SOCs was carried out on ships during four transect experiments during off-shore flow in Lake Superior using novel multicapillary collection devices and thermal extraction technology to measure parts-per-quadrillion SOC levels. Employing sensible heat in the modified Bowen ratio, fluxes at three over-water stations along the transects were measured, along with up-wind, onshore gaseous concentration and aqueous concentration. The atmosphere was unstable for

  14. Radon transferred from drinking water into house air

    International Nuclear Information System (INIS)

    A study was conducted to locate homes with high values of Rn-222 in the state of Maine. Forty Maine houses were selected with alleged Rn-222 in water concentrations higher than 5,000 pCi/L. Rn-222 measurements were performed during two periods in each residence from Oct 1986 to June 1987. During one period of approximately two hours duration, measurements were made while a series of simulated water use activities were conducted. Radon monitoring was performed over a second period of 24 hours, during which the residents used water according to their normal daily routine. Radon in water ranged up to 193,000 pCi/L. Water bursts ranged from 160-928 L. House volumes ranged from 190,000 to 2.2 million L. Air exchange was measured by both SF6 tracer diffusion and Rn-222 loss. The decay constant for SF6 ranged from 0.188 to 1.65 per hour, and the decay constant for Rn-222 ranged from 0.142 to 1.33 per hour. Emissivity ranged from 0.00 to 5.10, and Rn-222 transfer coefficients ranged from 0.00116 to 0.0000000301. The average value of the 24-hour transfer coefficient is 0.0000267 and is lower than the previous average of 0.00010. 20 refs., 5 figs., 6 tabs

  15. Deformation of a water shell during free fall in air

    Science.gov (United States)

    Nakoryakov, V. E.; Kuznetsov, G. V.; Strizhak, P. A.

    2016-04-01

    The basic regularities of the change in the shape and sizes (the initial volume is 0.05-0.5 L) of a water shell are singled out in its deformation during free fall in air from a height of 3 m. The 3D recording of the basic stages of deformation (flattening of the shell, nucleation, growth, and destruction of bubbles, formation of the droplet cloud) is carried out using high-speed (up to 105 frames per second) Phantom V411 and Phantom Miro M310 video cameras and the program complex Tema Automotive (with the function of continuous tracking). The physical model of destruction of large water bodies is formulated at free fall with the formation of the droplet cloud.

  16. Instrumented Water Tanks can Improve Air Shower Detector Sensitivity

    CERN Document Server

    Atkins, R; Berley, D; Chen, M L; Coyne, D G; Delay, R S; Dingus, B L; Dorfan, D E; Ellsworth, R W; Evans, D; Falcone, A D; Fleysher, L; Fleysher, R; Gisler, G; Goodman, J A; Haines, T J; Hoffman, C M; Hugenberger, S; Kelley, L A; Leonor, I; Macri, J R; McConnell, M; McCullough, J F; McEnery, J E; Miller, R S; Mincer, A I; Morales, M F; Némethy, P; Ryan, J M; Schneider, M; Shen, B; Shoup, A L; Sinnis, G; Smith, A J; Sullivan, G W; Thompson, T N; Tümer, T O; Wang, K; Wascko, M O; Westerhoff, S; Williams, D A; Yang, T; Yodh, G B

    1999-01-01

    Previous works have shown that water Cherenkov detectors have superior sensitivity to those of scintillation counters as applied to detecting extensive air showers (EAS). This is in large part due to their much higher sensitivity to EAS photons which are more than five times more numerous than EAS electrons. Large area water Cherenkov detectors can be constructed relatively cheaply and operated reliably. A sparse detector array has been designed which uses these types of detectors to substantially increase the area over which the Milagro Gamma Ray Observatory collects EAS information. Improvements to the Milagro detector's performance characteristics and sensitivity derived from this array and preliminary results from a prototype array currently installed near the Milagro detector will be presented.

  17. The Binding of Roxarsone at the Silica/Water Interface Studied with Second Harmonic Generation

    Science.gov (United States)

    Konek, Christopher; Ostrowski, David; Geiger, Franz

    2005-03-01

    Arsenic is a carcinogen that can also cause chronic poisoning when ingested via drinking water in quantities as low as 10 micrograms/L. In the US, organic arsenicals such as Roxarsone are commonly used as feed additives in the poultry industry. The use of poultry litter as fertilizer results in environmental arsenic deposition rates of up to 50 metric tons per year; the subsequent environmental fate of Roxarsone is unknown. We use second harmonic generation (SHG) to study the thermodynamics and kinetics of Roxarsone binding to environmentally relevant mineral oxide/water interfaces. Roxarsone binding to water/SiO2 interfaces is fully reversible, consistent with high Roxarsone mobility. Results from Langmuir isotherm measurements and surface SHG spectra are presented as well.

  18. Transport-limited water splitting at ion-selective interfaces during concentration polarization

    CERN Document Server

    Nielsen, Christoffer P

    2013-01-01

    We present an analytical model of salt- and water-ion transport across an ion-selective interface based on an assumption of local equilibrium of the water-dissociation reaction. The model yields current-voltage characteristics and curves of water-ion current versus salt-ion current, which are in qualitative agreement with experimental results published in the literature. The analytical results are furthermore in agreement with direct numerical simulations. As part of the analysis, we find approximate solutions to the classical problem of pure salt transport across an ion-selective interface. These solutions provide closed-form expressions for the current-voltage characteristics, which include the overlimiting current due to the development of an extended space charge region. Finally, we discuss how the addition of an acid or a base affects the transport properties of the system and thus provide predictions accessible to further experimental tests of the model.

  19. Adsorption dynamics of L-glutamic acid copolymers at a heptane/water interface.

    Science.gov (United States)

    Beverung, C J; Radke, C J; Blanch, H W

    1998-02-16

    Random copolymers of glutamic acid (glu-ala, glu-leu, glu-phe, glu-tyr) were employed to investigate the relationship between side chain structure and peptide charge on adsorption behavior at an oil/water boundary. Adsorption of a series of glutamate copolymers at a heptane/water interface was examined by the dynamic pendant-drop method to determine interfacial tension. Incorporation of leucine or phenylalanine into a glutamate copolymer results in greater tension reduction than incorporation of alanine or tyrosine. These effects are amplified at pH values near the isoelectric point of glutamate, where macroscopic adsorbed films of glu-leu and glu-phe exhibit gel-like properties in response to interfacial area compression. Differences in interfacial tension behavior of glu-tyr and glu-phe indicate the importance of the tyrosine p-hydroxyl group on adsorption and aggregation at the oil/water interface. PMID:9540205

  20. Relationship between Formation Water Rate, Equivalent Penetration Rate and Volume Flow Rate of Air in Air Drilling

    Institute of Scientific and Technical Information of China (English)

    Wang Kexiong; Zhang Laibin; Jiang Hongwei

    2007-01-01

    Formation water invasion is the most troublesome problem associated with air drilling. However, it is not economical to apply mist drilling when only a small amount of water flows into wellbore from formation during air drilling. Formation water could be circulated out of the wellbore through increasing the gas injection rate. In this paper,the Angel model was modified by introducing Nikurade friction factor for the flow in coarse open holes and translating formation water rate into equivalent penetration rate. Thus the distribution of annular pressure and the relationship between minimum air injection rate and formation water rate were obtained. Real data verification indicated that the modified model is more accurate than the Angel model and can provide useful information for air drilling.

  1. CLOUDS, AEROSOLS, RADIATION AND THE AIR-SEA INTERFACE OF THE SOUTHERN OCEAN: ESTABLISHING DIRECTIONS FOR FUTURE RESEARCH

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Robert [University of Washington; Bretherton, Chris [University of Washington; McFarquhar, Greg [University of Illinois - Urbana; Protat, Alain [Bureau of Meteorology - Melbourne; Quinn, Patricia [NOAA PMEL; Siems, Steven [Monash Univ., Melbourne, VIC (Australia); Jakob, Christian [Monash Univ., Melbourne, VIC (Australia); Alexander, Simon [Australian Antarctic Division; Weller, Bob [Woods Hole Oceanographic Institute

    2014-09-29

    A workshop sponsored by the Department of Energy was convened at the University of Washington to discuss the state of knowledge of clouds, aerosols and air-sea interaction over the Southern Ocean and to identify strategies for reducing uncertainties in their representation in global and regional models. The Southern Ocean plays a critical role in the global climate system and is a unique pristine environment, yet other than from satellite, there have been sparse observations of clouds, aerosols, radiation and the air-sea interface in this region. Consequently, much is unknown about atmospheric and oceanographic processes and their linkage in this region. Approximately 60 scientists, including graduate students, postdoctoral fellows and senior researchers working in atmospheric and oceanic sciences at U.S. and foreign universities and government laboratories, attended the Southern Ocean Workshop. It began with a day of scientific talks, partly in plenary and partly in two parallel sessions, discussing the current state of the science for clouds, aerosols and air-sea interaction in the Southern Ocean. After the talks, attendees broke into two working groups; one focused on clouds and meteorology, and one focused on aerosols and their interactions with clouds. This was followed by more plenary discussion to synthesize the two working group discussions and to consider possible plans for organized activities to study clouds, aerosols and the air-sea interface in the Southern Ocean. The agenda and talk slides, including short summaries of the highlights of the parallel session talks developed by the session chars, are available at http://www.atmos.washington.edu/socrates/presentations/SouthernOceanPresentations/.

  2. Water corrosion of spent nuclear fuel:radiolysis driven dissolution at the UO2/water interface

    OpenAIRE

    Springell, Ross S; Rennie, Sophie L; COSTELLE Leila; Darnbrough, James E; Stitt, C A D; Cocklin, Elizabeth; Lucas, Chris; Burrows, Robbert; SIMS, Howard; Wermeille, Didier; RAWLE Jonathan; Nicklin, Chris; Nuttall , William; Scott, Thomas Bligh; Lander, Gerard

    2015-01-01

    X-ray diffraction has been used to probe the radiolytic corrosion of uranium dioxide. Single crystal thin films of UO2 were exposed to an intense X-ray beam at a synchrotron source in the presence of water, in order to simultaneously provide radiation fields required to split the water into highly oxidising radiolytic products, and to probe the crystal structure and composition of the UO2 layer, and the morphology of the UO2/water interface. By modeling the electron density, surface roughness...

  3. Structure and functions of simple membrane-water interfaces. [Abstract only

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.

    1994-01-01

    The structure and functions of the earliest ancestors of contemporary cells are focal points in studies of the origin of life. Probably the first cell-like structures were vesicles - closed, spheroidal structures with aqueous medium trapped inside. The membranous walls of vesicles were most likely bilayers composed of simple amphiphilic material available on early earth. The membrane studied was composed of glycerol 1-monooleate (GMO). Glycerol forms the polar head group and the oily tail contains 18 carbon atoms. All head groups have been found to be located in two narrow regions at the interfaces with water. The membrane interior, formed by the hydrophobic tails, is quite fluid with chain disorder increasing towards the center of the bilayer. These results are in agreement with x-ray and neutron scattering data from related bilayers. The width of the membrane is not constant, but fluctuates in time and space. Occasional thinning defects in the membrane, observed during the course of the simulations, may have a significant influence on rates of passive transport of small molecules across membranes. It has been found that water penetrates the head group region but not the oily interior of the membrane. Water molecules near the interface are oriented by dipoles of the head groups. The resulting electrostatic potential across the interface, determined in our simulations, has been found to be markedly larger than across the water-oil interface. This quantity has been implicated as the source of selectivity, with respect to the sign of the charge, as an ion approaches the interface and during transport of hydrophobic ions across membranes.

  4. Air humidity and water pressure effects on the performance of air-cathode microbial fuel cell cathodes

    KAUST Repository

    Ahn, Yongtae

    2014-02-01

    To better understand how air cathode performance is affected by air humidification, microbial fuel cells were operated under different humidity conditions or water pressure conditions. Maximum power density decreased from 1130 ± 30 mW m-2 with dry air to 980 ± 80 mW m -2 with water-saturated air. When the cathode was exposed to higher water pressures by placing the cathode in a horizontal position, with the cathode oriented so it was on the reactor bottom, power was reduced for both with dry (1030 ± 130 mW m-2) and water-saturated (390 ± 190 mW m-2) air. Decreased performance was partly due to water flooding of the catalyst, which would hinder oxygen diffusion to the catalyst. However, drying used cathodes did not improve performance in electrochemical tests. Soaking the cathode in a weak acid solution, but not deionized water, mostly restored performance (960 ± 60 mW m-2), suggesting that there was salt precipitation in the cathode that was enhanced by higher relative humidity or water pressure. These results showed that cathode performance could be adversely affected by both flooding and the subsequent salt precipitation, and therefore control of air humidity and water pressure may need to be considered for long-term MFC operation. © 2013 Elsevier B.V. All rights reserved.

  5. Environmental application of nanotechnology: air, soil, and water.

    Science.gov (United States)

    Ibrahim, Rusul Khaleel; Hayyan, Maan; AlSaadi, Mohammed Abdulhakim; Hayyan, Adeeb; Ibrahim, Shaliza

    2016-07-01

    Global deterioration of water, soil, and atmosphere by the release of toxic chemicals from the ongoing anthropogenic activities is becoming a serious problem throughout the world. This poses numerous issues relevant to ecosystem and human health that intensify the application challenges of conventional treatment technologies. Therefore, this review sheds the light on the recent progresses in nanotechnology and its vital role to encompass the imperative demand to monitor and treat the emerging hazardous wastes with lower cost, less energy, as well as higher efficiency. Essentially, the key aspects of this account are to briefly outline the advantages of nanotechnology over conventional treatment technologies and to relevantly highlight the treatment applications of some nanomaterials (e.g., carbon-based nanoparticles, antibacterial nanoparticles, and metal oxide nanoparticles) in the following environments: (1) air (treatment of greenhouse gases, volatile organic compounds, and bioaerosols via adsorption, photocatalytic degradation, thermal decomposition, and air filtration processes), (2) soil (application of nanomaterials as amendment agents for phytoremediation processes and utilization of stabilizers to enhance their performance), and (3) water (removal of organic pollutants, heavy metals, pathogens through adsorption, membrane processes, photocatalysis, and disinfection processes).

  6. Environmental application of nanotechnology: air, soil, and water.

    Science.gov (United States)

    Ibrahim, Rusul Khaleel; Hayyan, Maan; AlSaadi, Mohammed Abdulhakim; Hayyan, Adeeb; Ibrahim, Shaliza

    2016-07-01

    Global deterioration of water, soil, and atmosphere by the release of toxic chemicals from the ongoing anthropogenic activities is becoming a serious problem throughout the world. This poses numerous issues relevant to ecosystem and human health that intensify the application challenges of conventional treatment technologies. Therefore, this review sheds the light on the recent progresses in nanotechnology and its vital role to encompass the imperative demand to monitor and treat the emerging hazardous wastes with lower cost, less energy, as well as higher efficiency. Essentially, the key aspects of this account are to briefly outline the advantages of nanotechnology over conventional treatment technologies and to relevantly highlight the treatment applications of some nanomaterials (e.g., carbon-based nanoparticles, antibacterial nanoparticles, and metal oxide nanoparticles) in the following environments: (1) air (treatment of greenhouse gases, volatile organic compounds, and bioaerosols via adsorption, photocatalytic degradation, thermal decomposition, and air filtration processes), (2) soil (application of nanomaterials as amendment agents for phytoremediation processes and utilization of stabilizers to enhance their performance), and (3) water (removal of organic pollutants, heavy metals, pathogens through adsorption, membrane processes, photocatalysis, and disinfection processes). PMID:27074929

  7. Influence of gold species (AuCl4(-) and AuCl2(-)) on self-assembly of PS-b-P2VP in solutions and morphology of composite thin films fabricated at the air/liquid interfaces.

    Science.gov (United States)

    Zhao, Xingjuan; Wang, Qian; Zhang, Xiaokai; Lee, Yong-Ill; Liu, Hong-Guo

    2016-01-21

    Composite thin films doped with Au species were fabricated at an air/liquid interface via a series of steps, including the mass transfer of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) across the liquid/liquid interface between a DMF/CHCl3 solution and an aqueous solution containing either AuCl4(-) or AuCl2(-), self-assembly of PS-b-P2VP in a mixed DMF-water solution, and adsorption and further self-organization of the formed aggregates at the air/liquid interface. This is a new approach for fabricating composite polymer films and can be completed within a very short time. AuCl4(-) and AuCl2(-) ions were found to significantly influence the self-assembly behavior of the block copolymer and the morphologies of the composite films, leading to the formation of nanowire arrays and a foam structure at the air/liquid interface, respectively, which originated from rod-like micelles and microcapsules that had formed in the respective solutions. The effect of the metal complex was analyzed based on the packing parameters of the amphiphilic polymer molecules in different microenvironments and the interactions between the pyridine groups and the metal chloride anions. In addition, these composite thin films exhibited stable and durable performance as heterogeneous catalysts for the hydrogenation of nitroaromatics in aqueous solutions. PMID:26688280

  8. Unsteady aspects of sodium-water-air reaction

    International Nuclear Information System (INIS)

    One important issue for the Sodium Fast Reactor (SFR) concept is the reactivity of metallic sodium and its exothermal reaction with water. In particular during equipments washing operations, sodium needs to be firstly converted ('destroyed') into non reactive species via a chemical reaction with water. Today, such operations are performed in tanks that confine the system and mitigate the consequences of any possible abnormal condition. Some data were obtained from experiments run by the French Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA) and were used as a basis for modelling. Among the principal phenomena identified so far are rapid water vaporization, hydrogen emission and explosion in air. High explosive-like pressure waves are generated from which sodium fragmentation and dispersion in water may ensue increasing the overall reactivity. It is extremely important to clarify the phenomenology to allow realistic extrapolation to full scale plants. A state of the art is proposed in this paper, starting from available experimental data and present perception of the physics. A comparison with present modelling strategy is also performed, underlining the necessity to improve a different and more physical approach aimed to well represent dynamic aspects of reaction. (authors)

  9. 45 CFR 2543.86 - Clean Air Act and the Federal Water Pollution Control Act.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Clean Air Act and the Federal Water Pollution..., HOSPITALS, AND OTHER NON-PROFIT ORGANIZATIONS Statutory Compliance § 2543.86 Clean Air Act and the Federal... regulations issued pursuant to the Clean Air Act (42 U.S.C. 7401 et seq.) and the Federal Water...

  10. Quantification of Water Content Across a Cement-clay Interface Using High Resolution Neutron Radiography

    Science.gov (United States)

    Shafizadeh, A.; Gimmi, T.; Van Loon, L.; Kaestner, A.; Lehmann, E.; Maeder, U. K.; Churakov, S. V.

    In many designs for radioactive waste repositories, cement and clay will come into direct contact. The geochemical contrast between cement and clay will lead to mass fluxes across the interface, which consequently results in alteration of structural and transport properties of both materials that may affect the performance of the multi-barrier system. We present an experimental approach to study cement-clay interactions with a cell to accommodate small samples of cement and clay. The cell design allows both in situ measurement of water content across the sample using neutron radiography and measurement of transport parameters using through-diffusion tracer experiments. The aim of the high-resolution neutron radiography experiments was to monitor changes in water content (porosity) and their spatial extent. Neutron radiographs of several evolving cement-clay interfaces delivered quantitative data which allow resolving local water contents within the sample domain. In the present work we explored the uncertainties of the derived water contents with regard to various input parameters and with regard to the applied image correction procedures. Temporal variation of measurement conditions created absolute uncertainty of the water content in the order of ±0.1 (m3/m3), which could not be fully accounted for by correction procedures. Smaller relative changes in water content between two images can be derived by specific calibrations to two sample regions with different, invariant water contents.

  11. Experimental study on fragmentation behaviors of molten LBE and water contact interface

    Institute of Scientific and Technical Information of China (English)

    黄望哩; 洒荣园; 周丹娜; 姜华磊; 黄群英

    2015-01-01

    Based on the design of CLEAR (China LEAd-based Reactor), it is important to study the molten LBE (Lead-Bismuth Eutectic)/water interaction following an incidental steam generator tube rupture (SGTR) accident. Experiments were carried out to investigate the fragmentation behavior of the molten LBE/water contacting interface, with a high-speed video camera to record the fragmentation behavior of 300–600◦C LBE at 20◦C and 80◦C of water temperature. Violent explosion phenomenon occurred at water temperature of 20◦C, while no explosion occurred at 80◦C. Shapes of the LBE debris became round at 80◦C of water temperature, whereas the debris was of the needle-like shape at 20◦C. For all the molten LBE and water temperatures in the present study, the debris sized at 2.8–5.0 mm had the largest mass fraction. The results indicate that the dominant physical mechanism of the molten LBE fragmentation was the Kelvin-Helmholtz instability between LBE/water direct contact interface.

  12. Comparison of phase behavior between water soluble and insoluble surfactants at the air-water interface

    International Nuclear Information System (INIS)

    The surface phase behavior of 2-hydroxyethyl myristate (2-HEM) has been studied in Langmuir monolayers by measuring surface pressure (π)-area (A) isotherms with a film balance and observing monolayer morphology with a Brewster angle microscope (BAM). These results are compared with the phase behavior of 2-hydroxyethyl laurate (2-HEL) in Gibbs monolayers studied by measuring π-time (t) curves and observing monolayer morphology. The π-A isotherms of 2-HEM show a first-order phase transition from a liquid expanded (LE) phase to a liquid condensed (LC) phase in the temperature range between 5 and 35 deg. C whereas the π-t curves of 2-HEL represent a similar phase transition in the temperature range between 2 and 25 deg. C. The critical surface pressure, πc necessary for the phase transitions increases with increasing temperature in both the cases. The LC domains formed in 2-HEM show circular shapes, which are independent of the temperature. In contrast, the circular domains having stripe texture formed at lower temperatures show a shape transition to fingering domains with uniform brightness at 15 deg. C. The amphiphile, 2-HEM having 13-carbon chain has higher line tension than 2-HEL that has 11-carbon chain as tail. Thus, for 2-HEM, this high line tension always dominates over other factors giving rise to circular domains at the all studied temperatures.

  13. Analysis of the Metals in Soil-Water Interface in a Manganese Mine

    Directory of Open Access Journals (Sweden)

    Bozhi Ren

    2015-01-01

    Full Text Available In order to reveal the influence of the metals of soil-water interface in a manganese mine (Xiangtan, China, on local water environment, there are six kinds of metals (Mn, Ni, Cu, Zn, Cd, and Pb characterized by measuring their concentration, correlation, source, and special distribution using principal component analysis, single factor, and Nemero comprehensive pollution index. The results showed that the corresponding average concentration was 0.3358, 0.045, 0.0105, 0.0148, 0.0067, and 0.0389 mg/L. The logarithmic concentration of Mn, Zn, and Pb was normal distribution. The correlation coefficients (between Mn and Pb, Mn and Zn, Mn and Ni, Cu and Zn, Cu and Pb, and Zn and Cd were found to range from 0.5 to 0.6, and those between Cu and Ni and Cu and Cd were below 0.3. It was found that Zn and Mn pollution were caused primarily by ore mining, mineral waste transportation, tailing slag, and smelting plants, while Cu and Ni mainly originate from the mining industry activities and the traffic transportation in the mining area. In addition, the Cd was considered to be produced primarily from the agricultural or anthropogenic activities. The pollution indexes indicated that metal pollution degree was different in soil-water interface streams as listed in increasing order of pollution level as Zn > Ni > Cu > Pb > Mn > Cd. For all of the pollution of the soil-water interface streams, there was moderate metal pollution but along the eastern mine area the pollution seemed to get more serious. There was only a small amount of soil-water interface streams not contaminated by the metals.

  14. A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

    Science.gov (United States)

    Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

    2014-12-16

    Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 μg m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes. PMID:25377990

  15. Interfacial rheometry of polymer at a water-oil interface by intra-pair magnetophoresis.

    Science.gov (United States)

    Cappelli, Stefano; de Jong, Arthur M; Baudry, Jean; Prins, Menno W J

    2016-07-01

    We describe an interfacial rheometry technique based on pairs of micrometer-sized magnetic particles at a fluid-fluid interface. The particles are repeatedly attracted and repelled by well-controlled magnetic dipole-dipole forces, so-called interfacial rheometry by intra-pair magnetophoresis (IPM). From the forces (∼pN), displacements (∼μm) and velocities (∼μm s(-1)) of the particles we are able to quantify the interfacial drag coefficient of particles within a few seconds and over very long timescales. The use of local dipole-dipole forces makes the system insensitive to fluid flow and suited for simultaneously recording many particles in parallel over a long period of time. We apply IPM to study the time-dependent adsorption of an oil-soluble amino-modified silicone polymer at a water-oil interface using carboxylated magnetic particles. At low polymer concentration the carboxylated particles remain on the water side of the water-oil interface, while at high polymer concentrations the particles transit into the oil phase. Both conditions show a drag coefficient that does not depend on time. However, at intermediate polymer concentrations data show an increase of the interfacial drag coefficient as a function of time, with an increase over more than three orders of magnitude (10(-7) to 10(-4) N s m(-1)), pointing to a strong polymer-polymer interaction at the interface. The time-dependence of the interfacial drag appears to be highly sensitive to the polymer concentration and to the ionic strength of the aqueous phase. We foresee that IPM will be a very convenient technique to study fluid-fluid interfaces for a broad range of materials systems. PMID:27253322

  16. Mean-Field Approximation to the Hydrophobic Hydration in the Liquid-Vapor Interface of Water.

    Science.gov (United States)

    Abe, Kiharu; Sumi, Tomonari; Koga, Kenichiro

    2016-03-01

    A mean-field approximation to the solvation of nonpolar solutes in the liquid-vapor interface of aqueous solutions is proposed. It is first remarked with a numerical illustration that the solvation of a methane-like solute in bulk liquid water is accurately described by the mean-field theory of liquids, the main idea of which is that the probability (Pcav) of finding a cavity in the solvent that can accommodate the solute molecule and the attractive interaction energy (uatt) that the solute would feel if it is inserted in such a cavity are both functions of the solvent density alone. It is then assumed that the basic idea is still valid in the liquid-vapor interface, but Pcav and uatt are separately functions of different coarse-grained local densities, not functions of a common local density. Validity of the assumptions is confirmed for the solvation of the methane-like particle in the interface of model water at temperatures between 253 and 613 K. With the mean-field approximation extended to the inhomogeneous system the local solubility profiles across the interface at various temperatures are calculated from Pcav and uatt obtained at a single temperature. The predicted profiles are in excellent agreement with those obtained by the direct calculation of the excess chemical potential over an interfacial region where the solvent local density varies most rapidly. PMID:26595441

  17. Recent Findings Based on Airborne Measurements at the Interface of Coastal California Clouds and Clear Air

    Science.gov (United States)

    Sorooshian, A.; Crosbie, E.; Wang, Z.; Chuang, P. Y.; Craven, J. S.; Coggon, M. M.; Brunke, M.; Zeng, X.; Jonsson, H.; Woods, R. K.; Flagan, R. C.; Seinfeld, J.

    2015-12-01

    Recent aircraft field experiments with the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter have targeted interfaces between clear and cloudy areas along the California coast. These campaigns, based out of Marina, California in the July-August time frame, include the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE, 2011), Nucleation in California Experiment (NiCE, 2013), and the Biological Ocean Atmospheric Study (BOAS, 2015). Results will be presented related to (i) aqueous processing of natural and anthropogenic emissions, (ii) vertical re-distribution of ocean micronutrients, and (iii) stratocumulus cloud clearings and notable thermodynamic and aerosol contrasts across the clear-cloudy interface. The results have implications for modeling and observational studies of marine boundary layer clouds, especially in relation to aerosol-cloud interactions.

  18. THE ASSESSMENT OF AIR AND WATER QUALITY OF SHARRA LANDFILL

    Directory of Open Access Journals (Sweden)

    A. Bani

    2011-04-01

    Full Text Available The waste disposal site of Sharra represents the first landfill for the management of solid wastes in Albania designed in accordance to the European Union standards for the management and administration of solid wastes. The objective of this study was to realize a general assessment of the environmental state in the areas nearby Sharra, after the implementation of the landfill as a remediation method. Water and air samples have been periodically collected and analyzed before and after the remediation of the waste disposal site of Sharra, respectively on the years 2008 and 2009. Results show that the measured indicators used to assess the quality of air such as; solid particles, PM10, NO2, H2S, CH4 reach the respective average values of 372 μg m-3, 216 μg m-3, 97 μg m-3, 0.8 μg m-3, 350 μg m-3 in 2008 and 72 μg m-3, 30 μg m-3, 29 μg m-3, 0.22 μg m-3, 41 μg m-3, in the year 2009. Before the remediation, except H2S the concentrations of all the other components in air exceed the Albanian and European Union limits whereas in 2009 these values have dropped under the mentioned limits. The concentration of heavy metals (mg L-1 in the surface waters exceeds the allowed limits for Ni (0.002-0.08, Mn (0.6, Cr (0.19-0.33 and Fe (0.2-3.5. As regards to the quality of surface water; some of the indicators such as EC, Cl-, NO2- resulted to surpass the above mentioned limits even after the implementation of the landfill. Based on the obtained results, further actions should be considered to be carried out in order to assure the collection and remediation of the landfill leaching prior they join the Erzeni River.

  19. Water-induced correlation between single ions imaged at the solid-liquid interface.

    Science.gov (United States)

    Ricci, Maria; Spijker, Peter; Voïtchovsky, Kislon

    2014-01-01

    When immersed into water, most solids develop a surface charge, which is neutralized by an accumulation of dissolved counterions at the interface. Although the density distribution of counterions perpendicular to the interface obeys well-established theories, little is known about counterions' lateral organization at the surface of the solid. Here we show, by using atomic force microscopy and computer simulations, that single hydrated metal ions can spontaneously form ordered structures at the surface of homogeneous solids in aqueous solutions. The structures are laterally stabilized only by water molecules with no need for specific interactions between the surface and the ions. The mechanism, studied here for several systems, is controlled by the hydration landscape of both the surface and the adsorbed ions. The existence of discrete ion domains could play an important role in interfacial phenomena such as charge transfer, crystal growth, nanoscale self-assembly and colloidal stability. PMID:25027990

  20. Air-water gas exchange by waving vegetation stems

    Science.gov (United States)

    Foster-Martinez, M. R.; Variano, E. A.

    2016-07-01

    Exchange between wetland surface water and the atmosphere is driven by a variety of motions, ranging from rainfall impact to thermal convection and animal locomotion. Here we examine the effect of wind-driven vegetation movement. Wind causes the stems of emergent vegetation to wave back and forth, stirring the water column and facilitating air-water exchange. To understand the magnitude of this effect, a gas transfer velocity (k600 value) was measured via laboratory experiments. Vegetation waving was studied in isolation by mechanically forcing a model canopy to oscillate at a range of frequencies and amplitudes matching those found in the field. The results show that stirring due to vegetation waving produces k600 values from 0.55 cm/h to 1.60 cm/h. The dependence of k600 on waving amplitude and frequency are evident from the laboratory data. These results indicate that vegetation waving has a nonnegligible effect on gas transport; thus, it can contribute to a mechanistic understanding of the fluxes underpinning biogeochemical processes.

  1. Chapter 1 Surface Structure and Reactivity of Iron Oxide-Water Interfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Ghose, S.K.; Petitto, S.C.; Tanwar, K.S.; Lo, C.S.; Eng, P.J.; Chaka, A.M.; Trainor, T.P. (Univ Alaska Fairbanks); (UofC)

    2008-04-29

    The surface structure and composition of the three distinct iron-(hydr)oxide systems, goethite (1 0 0), hematite (1{bar 1}02), and magnetite (1 1 1) were determined under hydrated conditions at room temperature using crystal truncation rod (CTR) analysis. The prediction of surface protonation states and the overall chemical plausibility of the experimental surface models are performed using a bond-valence (BV) analysis. Further analysis of the surface energetics is carried out using density functional theory (DFT). The analysis of three common iron-(hydr)oxide surface systems reveals the differences in interface structure and distribution of hydroxyl groups at substrate-water interfaces. The goethite (1 0 0) interface structure is determined to have a relaxed double hydroxyl termination with the presence of two semi-ordered water layers that expose a surface with A-type (Fe-OH{sub 2}) and B-type (Fe{sub 2}-OH) hydroxyl groups. The hydrated hematite (1{bar 1}02) interface structure has vacancies in the near surface metal sites, resulting in three types of surface functional groups: A type, B type, and C type (Fe{sub 3}-O). The interface structure of magnetite (1 1 1) shows two chemically nonequivalent oxygen surface terminations in the surface ratio of 70 O{sub 4}-Fe{sub oh}-O{sub 4}-Fe{sub td1-oh-td2}:30 O{sub 4}-Fe{sub td1-oh-td2}-O{sub 4}-Fe{sub oh} suggesting that the octahedral irons are the principal irons involved at the environmental interfaces. In the above three systems, there also is evidence for multiple domains with fractional ordered unit cell steps determined by atomic force microscopy (AFM). Results obtained for the structure of the iron-(hydr)oxide-water interfaces from the CTR and DFT analyses are different from stoichiometric termination of the bulk structure or hydroxylation of the ultra high vacuum (UHV) determined surface structures.

  2. Measurement System to Monitor Interface Level Between Oil and Water in a Rapidly Rotating System

    OpenAIRE

    Saeed, Mohsin

    2013-01-01

    Alfa Laval is a market leader in centrifugal separators that develops and sells separators for a wide range of uses. Clarification of beer, wine, water purification, drug production and purification of marine fuels are just a few of the hundreds of different uses for Alfa Laval separators. To further optimize their separator performance, Alfa Laval is interested in the development of a measurement system, which can find the interface position between the lighter and the heavier liquid phases ...

  3. Interfacial rheology and conformations of triblock copolymers adsorbed onto the water-oil interface

    OpenAIRE

    Ramirez, Pablo; STOCCO, Antonio; Munoz, José; Miller, Reinhard

    2012-01-01

    The conformation and the dilatational properties of three non-ionic triblock PEO-PPO-PEO (where PEO is polyethyleneoxide and PPO is polypropyleneoxide) copolymers of different hydrophobicity and molecular weight were investigated at the water-hexane interface. The interfacial behavior of the copolymers was studied by combining dilatational rheology using the oscillating drop method and ellipsometry. From the dilatational rheology measurements the limiting elasticity values, E_0, of the Pluron...

  4. MM-PBSA Captures Key Role of Intercalating Water Molecules at a Protein−Protein Interface

    OpenAIRE

    Wong, Sergio; Amaro, Rommie E.; McCammon, J. Andrew

    2009-01-01

    The calculation of protein interaction energetics is of fundamental interest, yet accurate quantities are difficult to obtain due to the complex and dynamic nature of protein interfaces. This is further complicated by the presence of water molecules, which can exhibit transient interactions of variable duration and strength with the protein surface. The T-cell receptor (TCR) and its staphylococcal enterotoxin 3 (SEC3) binding partner are well-characterized examples of a protein−protein intera...

  5. Adsorption Kinetics of Alkyl Polyglucoside at the Air-Solution Interface

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The air-solution equilibrium tension ye and dynamic surface tension ye, of nonionic surfactant alkyl polyglucoside have been studied. ye was measured by the Wilhelmy method with tension vs. concentration curve. The ye decays were measured in the range 0.2~20 s using a maximum bubble pressure instrument and analyzed with the Ward and Tordai cquation.

  6. Interfacial structure in an air-water planar bubble jet

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X. [Purdue University, School of Nuclear Engineering, West Lafayette, IN (United States); The Ohio State University, Department of Mechanical Engineering, Columbus, OH (United States); Vasavada, S.; Choi, S.W.; Ishii, M. [Purdue University, School of Nuclear Engineering, West Lafayette, IN (United States); Kim, S. [Purdue University, School of Nuclear Engineering, West Lafayette, IN (United States); University of Missouri-Rolla, Nuclear Engineering, Rolla, MO (United States); Beus, S.G. [Bechtel Bettis Inc., West Mifflin, PA (United States)

    2005-04-01

    The objective of the current study is to better understand the interfacial structure and its development in an air-water planar bubble jet, as well as to provide a unique benchmark data set for a 3D thermal-hydraulic analysis code. Both flow visualization and local measurements were performed in three characteristic flow conditions at four elevations along a test section with a cross section of 200 mm in width and 10 mm in gap. A high-speed digital video camera was applied in the flow visualization study to capture the flow structures and bubble interaction phenomena, while a miniaturized four-sensor conductivity probe was used to acquire the time-averaged local void fraction, interfacial velocity, and bubble number frequency. Also, the interfacial area concentration and the averaged bubble Sauter mean diameter were obtained from the local measurements. The lateral bubble transport and bubble interaction mechanisms were clearly demonstrated in the acquired data. (orig.)

  7. Disponibilidad de agua-aire en sustratos para plantas Water-air availability in plant substrates

    Directory of Open Access Journals (Sweden)

    Lilia Beatriz Vence

    2008-12-01

    Full Text Available Las propiedades físicas de los sustratos especialmente las relacionadas con la disponibilidad de agua-aire para las raíces de las plantas son las más importantes dentro del estudio de estos materiales usados en cultivos en contenedores. Para un óptimo crecimiento de la planta un sustrato debe contener suficiente cantidad de agua y aire y ambos estar disponibles. A nivel mundial el estudio de las propiedades que determinan esta disponibilidad comenzó desde las ciencias del suelo y fue adaptándose a las características propias de la amplia gama de productos que pueden ser utilizados, surgiendo así variables y métodos de medida específicos para la caracterización física de sustratos. En la Argentina el estudio de sustratos para plantas constituye un área de conocimiento nueva y en desarrollo, por ello exige un trabajo interdisciplinario donde hay que concordar un lenguaje común de términos técnicos, la elección de los métodos analíticos de referencia específicos y una legislación actualizada para sustratos. Haciendo un estudio crítico de la gran cantidad de información al respecto que proviene de otros países se podrán adaptar a nuestra realidad y a nuestros materiales. En esta revisión se enumeran resumidamente los más importantes conceptos a tener en cuenta para la evaluación física de sustratos a fin de que puedan servir de base para una mejor comprensión y discusión del tema.The study of the physical properties of substrates for container plant production is very important because the water and air availability for plant roots is involved. A substrate must contain a sufficient amount of available water and air to produce an optimum plant growth and development. Worldwide, the study of the properties that determine the water and air availability started from soil sciences and has been evolving to the present existence of a great variety of products that can be used, concomitant with the identification of parameters

  8. A comparison of didodecyldimethylammonium bromide adsorbed at mica/water and silica/water interfaces using neutron reflection.

    Science.gov (United States)

    Griffin, Lucy R; Browning, Kathryn L; Truscott, Chris L; Clifton, Luke A; Webster, John; Clarke, Stuart M

    2016-09-15

    The layer structure of the dichain alkyl ammonium surfactant, didodecyldimethylammonium bromide (DDAB), adsorbed from water on to silica and mica surfaces has been determined using neutron reflection. Although sometimes considered interchangeable surfaces for study, we present evidence of significant differences in the adsorbed layer structure below the critical micelle concentration. A complete DDAB bilayer was assembled at the water/mica interface at concentrations below the critical micelle concentration (CMC). In contrast it is not until the CMC was reached that the complete bilayer structure formed on the oxidised silicon crystal. Removal of the complete bilayer on both surfaces was attempted by both washing and ion exchange yet the adsorbed structure proved tenacious.

  9. Ultrasonic Measurement of Water Layer Thickness by Flow Pattern Profile in a Horizontal Air Water Loop

    International Nuclear Information System (INIS)

    Ultrasonic methods have the advantage, compared to other water layer thickness measurement techniques, of applicability to large volume objects, since most radiation techniques are limited by the thickness of the pipe and plate walls. The ultrasonic experiment was performed to do an analysis for cooling performance in a complete test channel by the investigation of the two phase flow that develops in an inclined gap with heating from the top. This ultrasonic technique for measuring water layer thickness measurement employ the higher relative acoustic impedance of air with respect to that of liquids. By this method it is possible to determine both liquid water distance, void fraction in a gas-liquid two-phase flow. Instantaneous measurement of the water layer thickness is useful in understanding heat and mass transfer characteristics in a two-phase separated flow. An ultrasonic measurement technique for determining water layer thickness in the wavy and slug flow regime of horizontal tube flow has been produced

  10. 15 CFR 923.45 - Air and water pollution control requirements.

    Science.gov (United States)

    2010-01-01

    ... 15 Commerce and Foreign Trade 3 2010-01-01 2010-01-01 false Air and water pollution control....45 Air and water pollution control requirements. The program must incorporate, by reference or otherwise, all requirements established by the Federal Water Pollution Control Act, as amended (Clean...

  11. 14 CFR 1274.926 - Clean Air-Water Pollution Control Acts.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Clean Air-Water Pollution Control Acts...-Water Pollution Control Acts. Clean Air-Water Pollution Control Acts July 2002 If this cooperative... Violating Facilities” published pursuant to 40 CFR 15.20. By acceptance of a cooperative agreement in...

  12. Adsorption kinetics of alkanethiol-capped gold nanoparticles at the hexane–water interface

    International Nuclear Information System (INIS)

    The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol-capped gold nanoparticles at the hexane–water interface. The adsorption process was studied by analyzing the dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately after the interface between the fluids is made and once equilibrium has been established). A series of gold colloids were made using nanoparticles ranging in size from 1.60 to 2.85 nm dissolved in hexane for the interfacial tension analysis. Following free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles at the interface and formation of a dense monolayer. With increasing interfacial coverage, the diffusion-controlled adsorption for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov et al. (Phys Chem Chem Phys 9:6351–6358, 2007). The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol-capped gold nanoparticles at liquid–liquid interfaces.

  13. Generation of Air/SF6 Interface with Minimum Surface Feature by Soap Film Technique

    Science.gov (United States)

    Wang, Xiansheng; Si, Ting; Luo, Xisheng; Yang, Jiming

    The Richtmyer-Meshkov (RM) instability occurs on an initially perturbed interface subjecting to a sudden acceleration by a shock [2]. Due to the deposition of baroclinic vorticity, the initial perturbation will grow with time, which generally intensifies the mixing between fluids and eventually induces turbulence in flow. Because of its academic significance in vortex dynamics and turbulent mixing as well as wide applications ranging from inertial confinement fusion, supernova explosions to supersonic combustion, the hydrodynamic instability becomes increasingly attractive. Specifically, several comprehensive reviews on this topic have been made [1, 2, 3].

  14. Theoretical ultrasonic reflection at a wave/composite laminate/water interface

    International Nuclear Information System (INIS)

    This study describes analysis for ultrasonic leaky plate wave propagation in multidirectional composite laminates. Specifically, the analytical reflection coefficient is derived for a water/composite laminate/water interface. Theoretical predictions of reflected beam amplitudes are also presented. Four different composite laminates are investigated: T300/5208 graphite/epoxy [0]31T [45/90/-45/0]3s [45/-45]2-s, and S-2 glass/epoxy [0/90]4s. The analytical dispersion curves for the unidirectional laminate and other three laminates can be obtained by searching for the minimum magnitude of the reflection coefficient.

  15. The adsorption behavior of octafluoropropane at the water/gas interface

    International Nuclear Information System (INIS)

    We studied the adsorption behavior of the gas octafluoropropane at the water/gas interface as a function of different pressures. In a custom-made measurement cell, the gas pressure was varied in a range between 1 bar and close to the condensation pressure of octafluoropropane. The electron density profiles of the adsorption layers show that the layer thickness increases with pressure. The evolution of the layer electron density indicates that the bulk electron density is reached if a layer consisting of more than one monolayer of octafluoropropane is adsorbed on the water surface

  16. SPECIATION OF ARSENIC ACROSS WATER-SEDIMENT INTERFACE OF FALGU RIVER

    OpenAIRE

    Rajeeva Ranjan; Rekha Rani; Ashay Bavishi; Shivadhar Sharma; Madhusudan Choudhary

    2012-01-01

    Two predominant species of arsenic compounds, As(III) and As(V), are found in soils and natural water and they have been classified as carcinogens. The focus of the present study was to examine the speciation of Arsenic (As) across the water-sediment interface at the confluence of drainage for Gaya city and the Falgu River. Gas Chromatography (GC) coupled to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to analyze the organic arsenic species while the inorganic arsenic specie...

  17. Nutrient exchange and release experiment and its simulation study in lake water-sediment interface

    Institute of Scientific and Technical Information of China (English)

    XUE Lian-qing; HAO Zhen-chun

    2006-01-01

    The sediment distributed and insolated under lake was collected for experiments. The nutrient layer distribution conditions of sampled sediment and its physical and chemical characteristics were analyzed to simulate and assess the influence degree to lake water quality. Based on the dynamic water exchanging experiments the nutrient release process in sediment and influence mechanism to substance exchanging on water-sediment interface was studied, and the correlation between the changing content of total phosphors and total nitrogen in sediment and covered water were analyzed for setting up a simulation model. At the same time the influence degree is explained in detail. The experimental results indicated that even if clean water without nutrient contents was used for water exchangement so as to decrease pollution or prevent eutrophication, however owing to the vertical nutrient distribution in lake sediment, it will lead to the increasing release amount greatly especially when the organic nutrient contained in sediment turns into inorganic status because of isolation. Besides the release process of total phosphate (TP) and total nitrogen (TN) were modeled and each nutrient's exchanging equation at interface caused by covered water nutrient concentration changing was set up. According to the simulating prediction, TP and TN content of cover water will also sustain a steady higher level in a long period. The nutrient release amount of sediment is not only affected by the covered water concentration but also connects with accumulative time. The experiments provide the fundamental theoretical and practical basis for taking ecological restoration project. And research is helpful to prevent or restore lake eutrophication.

  18. Nutrient exchange and release experiment and its simulation study in lake water-sediment interface.

    Science.gov (United States)

    Xue, Lian-Qing; Hao, Zhen-Chun

    2006-01-01

    The sediment distributed and insolated under lake was collected for experiments. The nutrient layer distribution conditions of sampled sediment and its physical and chemical characteristics were analyzed to simulate and assess the influence degree to lake water quality. Based on the dynamic water exchanging experiments the nutrient release process in sediment and influence mechanism to substance exchanging on water-sediment interface was studied, and the correlation between the changing content of total phosphors and total nitrogen in sediment and covered water were analyzed for setting up a simulation model. At the same time the influence degree is explained in detail. The experimental results indicated that even if clean water without nutrient contents was used for water exchangement so as to decrease pollution or prevent eutrophication, however owing to the vertical nutrient distribution in lake sediment, it will lead to the increasing release amount greatly especially when the organic nutrient contained in sediment turns into inorganic status because of isolation. Besides the release process of total phosphate (TP) and total nitrogen (TN) were modeled and each nutrient's exchanging equation at interface caused by covered water nutrient concentration changing was set up. According to the simulating prediction, TP and TN content of cover water will also sustain a steady higher level in a long period. The nutrient release amount of sediment is not only affected by the covered water concentration but also connects with accumulative time. The experiments provide the fundamental theoretical and practical basis for taking ecological restoration project. And research is helpful to prevent or restore lake eutrophication. PMID:17294663

  19. Relay cropping for improved air and water quality.

    Science.gov (United States)

    Schepers, James S; Francis, Dennis D; Shanahan, John F

    2005-01-01

    Using plants to extract excess nitrate from soil is important in protecting against eutrophication of standing water, hypoxic conditions in lakes and oceans, or elevated nitrate concentrations in domestic water supplies Global climate change issues have raised new concerns about nitrogen (N) management as it relates to crop production even though there may not be an immediate threat to water quality. Carbon dioxide (CO2) emissions are frequently considered the primary cause of global climate change, but under anaerobic conditions, animals can contribute by expelling methane (CH4) as do soil microbes. In terms of the potential for global climate change, CH4 is approximately 25 times more harmful than CO2. This differential effect is minuscule compared to when nitrous oxide (N2O) is released into the atmosphere because it is approximately 300 times more harmful than CO2. N2O losses from soil have been positively correlated with residual N (nitrate, NO3-) concentrations in soil. It stands to reason that phytoremediation via nitrate scavenger crops is one approach to help protect air quality, as well as soil and water quality. Winter wheat was inserted into a seed corn/soybean rotation to utilize soil nitrate and thereby reduce the potential for nitrate leaching and N2O emissions. The net effect of the 2001-2003 relay cropping sequence was to produce three crops in two years, scavenge 130 kg N/ha from the root zone, produce an extra 2 Mg residue/ha, and increase producer profitability by approximately 250 dollars/ha. PMID:15948582

  20. Science-policy interfacing in support of the Water Framework Directive implementation.

    Science.gov (United States)

    Vaes, G; Willems, P; Swartenbroekx, P; Kramer, K; de Lange, W; Kober, K

    2009-01-01

    Many current water-related RTD projects have established operational links with practitioners, which allow the needs of policy makers to be taken into account. However, RTD results are not easily available to water policy implementers and research scientists may lack insight in the needs of policy makers and implementers (i.e. the European Commission and water managers). The SPI-Water project worked out a number of concrete actions to bridge these gaps in communication by developing and implementing a 'science-policy interface', enhancing the use of RTD results in the Water Framework Directive (WFD) implementation. This project is part of a wider EC perspective aiming to bridge the gap between science and policy, specifically with respect to the WFD implementation. As a first action, existing science-policy links are investigated. RTD and LIFE projects that are of direct relevance for the implementation of the WFD are identified and analysed. Secondly, an information system (Harmoni-CA's WISE RTD Web Portal) has been further developed to cater for an efficient and easy to use tool for dissemination as well as retrieval of RTD results. As third action, this science-policy interfacing of WFD related topics are extended to non-EU countries taking into account their specific needs.

  1. Transporting of a Cell-Sized Phospholipid Vesicle Across Water/Oil Interface

    CERN Document Server

    Hase, M; Hamada, T; Yoshikawa, K; Hase, Masahiko; Yamada, Ayako; Hamada, Tsutomu; Yoshikawa, Kenichi

    2006-01-01

    When a cell-sized water droplet, with a diameter of several tens of micro meter, is placed in oil containing phospholipids, a stable cell-sized vesicle is spontaneously formed as a water-in-oil phospholipid emulsion (W/O CE) with a phospholipid monolayer. We transferred the lipid vesicle thus formed in the oil phase to the water phase across the water/oil interface by micromanipulation, which suggests that the vesicle is transformed from a phospholipid monolayer as W/O CE into a bilayer. The lipid vesicle can then be transported back into the oil phase. This novel experimental procedure may be a useful tool for creating a model cellular system, which, together with a microreactor, is applicable as a micrometer-scale biochemical reaction field.

  2. Modelling Air and Water Two-Phase Annular Flow in a Small Horizontal Pipe

    Science.gov (United States)

    Yao, Jun; Yao, Yufeng; Arini, Antonino; McIiwain, Stuart; Gordon, Timothy

    2016-06-01

    Numerical simulation using computational fluid dynamics (CFD) has been carried out to study air and water two-phase flow in a small horizontal pipe of an inner diameter of 8.8mm, in order to investigate unsteady flow pattern transition behaviours and underlying physical mechanisms. The surface liquid film thickness distributions, determined by either wavy or full annular flow regime, are shown in reasonable good agreement with available experimental data. It was demonstrated that CFD simulation was able to predict wavy flow structures accurately using two-phase flow sub-models embedded in ANSYS-Fluent solver of Eulerian-Eulerian framework, together with a user defined function subroutine ANWAVER-UDF. The flow transient behaviours from bubbly to annular flow patterns and the liquid film distributions revealed the presence of gas/liquid interferences between air and water film interface. An increase of upper wall liquid film thickness along the pipe was observed for both wavy annular and full annular scenarios. It was found that the liquid wavy front can be further broken down to form the water moisture with liquid droplets penetrating upwards. There are discrepancies between CFD predictions and experimental data on the liquid film thickness determined at the bottom and the upper wall surfaces, and the obtained modelling information can be used to assist further 3D user defined function subroutine development, especially when CFD simulation becomes much more expense to model full 3D two-phase flow transient performance from a wavy annular to a fully developed annular type.

  3. The entrainment of air by water jet impinging on a free surface

    Energy Technology Data Exchange (ETDEWEB)

    Soh, Wee King [University of Wollongong, School of Mechanical, Materials and Mechatronics Engineering, Northfields Ave, NSW (Australia); Khoo, Boo Cheong [National University of Singapore, Department of Mechanical and Production Engineering, 10 Kent Ridge Crescent (Singapore); Yuen, W.Y. Daniel [BlueScope Steel Research, Port Kembla, NSW (Australia)

    2005-09-01

    High-speed cine and video photographs were used to capture the flow patterns of a column of water jet impinging into a pool of water. The impact results in air entrainment into water in the form of a void with no mixing between the water in the jet and the surrounding water. Conservation of fluid momentum shows that the rate of increase of the height of the air void depends on the drag coefficient of the jet front. By neglecting the frictional losses, the application of energy conservation yields an expression that relates the maximum height of the air void with the properties of the water jet. (orig.)

  4. Portable Amperometric Perchlorate Selective Sensors with Microhole Array-water/organic Gel Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Hyuk; Girault, Hubert H.; Lee, Hye Jin [Kyungpook National Univ., Daegu (Korea, Republic of); Kim, Hyungi [Gyeongbuk Technopark, Gyeongsan (Korea, Republic of); Girault, Hubert H. [Ecole Polytechnique Federale de Lausanne, Lausanne (Switzerland)

    2013-09-15

    A novel stick-shaped portable sensing device featuring a microhole array interface between the polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) gel and water phase was developed for in-situ sensing of perchlorate ions in real water samples. Perchlorate sensitive sensing responses were obtained based on measuring the current changes with respect to the assisted transfer reaction of perchlorate ions by a perchlorate selective ligand namely, bis(dibenzoylmethanato)Ni(II) (Ni(DBM){sub 2}) across the polarized microhole array interface. Cyclic voltammetry was used to characterize the assisted transfer reaction of perchlorate ions by the Ni(DBM){sub 2} ligand when using the portable sensing device. The current response for the transfer of perchlorate anions by Ni(DBM){sub 2} across the micro-water/gel interface linearly increased as a function of the perchlorate ion concentration. The technique of differential pulse stripping voltammetry was also utilized to improve the sensitivity of the perchlorate anion detection down to 10 ppb. This was acquired by preconcentrating perchlorate anions in the gel layer by means of holding the ion transfer potential at 0 mV (vs. Ag/AgCl) for 30 s followed by stripping the complexed perchlorate ion with the ligand. The effect of various potential interfering anions on the perchlorate sensor was also investigated and showed an excellent selectivity over Br{sup -}, NO{sub 2}{sup -}, NO{sub 3}{sup -}, CO{sub 3}{sup 2-}, CH{sub 3}COO{sup -} and SO{sub 4}{sup 2-} ions. As a final demonstration, some regional water samples from the Sincheon river in Daegu city were analyzed and the data was verified with that of ion chromatography (IC) analysis from one of the Korean-certified water quality evaluation centers.

  5. The exchange of SVOCs across the air-sea interface in Singapore's coastal environment

    OpenAIRE

    He, J.; Balasubramanian, R

    2009-01-01

    Coastal areas are vulnerable to the accumulation of semi-volatile organic compounds such as PAHs, OCPs and PCBs from atmospheric inputs. Dry particulate and wet depositions, and air-water diffusive exchange in the Singapore's south coastal area, where most of chemical and oil refinery industries are situated in, were estimated. Based on a yearly dataset, the mean annual dry particulate deposition fluxes of ∑16PAHs, ∑7OCPs and ...

  6. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

    2016-04-19

    Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the

  7. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

    2016-04-19

    Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the

  8. Non-thermal plasma for air and water remediation.

    Science.gov (United States)

    Hashim, Siti Aiasah; Samsudin, Farah Nadia Dayana Binti; Wong, Chiow San; Abu Bakar, Khomsaton; Yap, Seong Ling; Mohd Zin, Mohd Faiz

    2016-09-01

    A modular typed dielectric barrier discharge (DBD) device is designed and tested for air and water remediation. The module is made of a number of DBD tubes that can be arranged in series or parallel. Each of the DBD tubes comprises inner electrode enclosed with dielectric barrier and arranged as such to provide a gap for the passage of gases. Non-thermal plasma generated in the gap effectively creates gaseous chemical reactions. Its efficacy in the remediation of gas stream containing high NOx, similar to diesel emission and wastewater containing latex, are presented. A six tubes DBD module has successfully removed more than 80% of nitric oxide from the gas stream. In another arrangement, oxygen was fed into a two tubes DBD to generate ozone for treatment of wastewater. Samples of wastewater were collected from a treatment pond of a rubber vulcanization pilot plant. The water pollution load was evaluated by the chemical oxygen demand (COD) and biological oxygen demand (BOD5) values. Preliminary results showed some improvement (about 13%) on the COD after treatment and at the same time had increased the BOD5 by 42%. This results in higher BOD5/COD ratio after ozonation which indicate better biodegradability of the wastewater. PMID:27056469

  9. Macroscopic investigation of hydrate film growth at the hydrocarbon/water interface

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, C.J.; Miller, K.T.; Koh, C.A.; Sloan, E.D. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates are ice-like crystalline compounds that form as thin porous crystalline films at the interface between the water phase and the hydrocarbon guest molecule phase. The growth characteristics of these hydrate films are important in seafloor carbon dioxide sequestration, gas hydrate transport, and flow assurance in oil and gas pipelines. This paper presented a study that employed digital video microscopy to investigate the hydrate film thickness as a function of time, as well as the propagation rate for methane and cyclopentane hydrate. The purpose of the study was to enhance past measurements of hydrate film growth by incorporating gas consumption measurements simultaneously with film thickness measurements to determine which phase supplied the hydrate former during hydrate formation. The study also advanced the physical knowledge of hydrate formation by relating film formation with the water droplet to hydrate shell conversion. The paper included a schematic of the hydrate film growth apparatus and image acquisition and analysis as well as an illustration of the nucleation of a water droplet immersed in cyclopentane. The results were presented for cyclopentane hydrate film growth; methane hydrate film growth; film growth in an oil/methane/ water system; film growth/development into water phase; and gas consumption for hydrate film growth. The paper also discussed the source of methane for hydrate formation; solubility of methane in water; growth rates; proposed mechanism of hydrate film growth at the hydrocarbon/water interface; and, transferability between hydrate formation for a pool of liquid versus a water droplet. It was concluded that gas consumption data during hydrate formation presented evidence of an aqueous phase supply of hydrate former to the initial hydrate growth, followed by a vapor phase supply of hydrate former in the thickening stage of hydrate film formation. 25 refs., 18 figs.,.

  10. Effects of air vessel on water hammer in high-head pumping station

    International Nuclear Information System (INIS)

    Effects of air vessel on water hammer process in a pumping station with high-head were analyzed by using the characteristics method. The results show that the air vessel volume is the key parameter that determines the protective effect on water hammer pressure. The maximum pressure in the system declines with increasing air vessel volume. For a fixed volume of air vessel, the shape of air vessel and mounting style, such as horizontal or vertical mounting, have little effect on the water hammer. In order to obtain good protection effects, the position of air vessel should be close to the outlet of the pump. Generally, once the volume of air vessel is guaranteed, the water hammer of a entire pipeline is effectively controlled

  11. A passive brain-computer interface application for the mental workload assessment on professional air traffic controllers during realistic air traffic control tasks.

    Science.gov (United States)

    Aricò, P; Borghini, G; Di Flumeri, G; Colosimo, A; Pozzi, S; Babiloni, F

    2016-01-01

    In the last decades, it has been a fast-growing concept in the neuroscience field. The passive brain-computer interface (p-BCI) systems allow to improve the human-machine interaction (HMI) in operational environments, by using the covert brain activity (eg, mental workload) of the operator. However, p-BCI technology could suffer from some practical issues when used outside the laboratories. In particular, one of the most important limitations is the necessity to recalibrate the p-BCI system each time before its use, to avoid a significant reduction of its reliability in the detection of the considered mental states. The objective of the proposed study was to provide an example of p-BCIs used to evaluate the users' mental workload in a real operational environment. For this purpose, through the facilities provided by the École Nationale de l'Aviation Civile of Toulouse (France), the cerebral activity of 12 professional air traffic control officers (ATCOs) has been recorded while performing high realistic air traffic management scenarios. By the analysis of the ATCOs' brain activity (electroencephalographic signal-EEG) and the subjective workload perception (instantaneous self-assessment) provided by both the examined ATCOs and external air traffic control experts, it has been possible to estimate and evaluate the variation of the mental workload under which the controllers were operating. The results showed (i) a high significant correlation between the neurophysiological and the subjective workload assessment, and (ii) a high reliability over time (up to a month) of the proposed algorithm that was also able to maintain high discrimination accuracies by using a low number of EEG electrodes (~3 EEG channels). In conclusion, the proposed methodology demonstrated the suitability of p-BCI systems in operational environments and the advantages of the neurophysiological measures with respect to the subjective ones. PMID:27590973

  12. Time dependent FTIR spectra of mineral waters after contact with air

    CERN Document Server

    Kondyurin, Alexey

    2010-01-01

    FTIR spectra of mineral waters of Slavyanovskaya, Aqua Montana, Bad Harzburger and Christinen with time from first contact of water with open air were analysed. The kinetic of spectral changes of Slavyanovskaya mineral water in the regions of stretch, deformation and intermolecular vibrations was measured. The spectral changes do not correlate with chemical contamination of mineral water and degassing process. The observed spectral changes could be due to different structure of mineral water in liquid state, which is destroyed after air contact. The observed spectral behaviour of Slavyanovskaya is correlated with the catalytic activity of mineral water, which was saved without contact with air. The characteristic time of spectral dependence (669 seconds) is close to the characteristic time of catalytic activity loss (600 seconds) of mineral water at air contact. The spectra results support the medical studies that show the activity of mineral water near spring, and the loosing activity of water after long tim...

  13. Spatial and temporal variation in methane distribution at the ground water/surface water interface in headwater catchments

    Energy Technology Data Exchange (ETDEWEB)

    Baker, M.A.; Dahm, C.N.; Valett, H.M.; Morrice, J.A.; Henry, K.S.; Campana, M.E.; Wroblicky, G.J. [Univ. of New Mexico, Albuquerque, NM (United States)

    1994-12-31

    High concentrations of methane can be found in anoxic zones of ground water near its interface with surface water in montane streams. Lithology, sediment characteristics, flow regimes and season affect the concentration and distribution of methane. Seasonal and spatial patterns of methane distribution were studied in surface and subsurface waters from three first-order montane streams in New Mexico. Alluvium at Aspen Creek (sandstone/siltstone) has low hydraulic conductivity, Rio Calaveras has intermediate hydraulic conductivity (volcanic tuff), and Gallina creek has high hydraulic conductivity (granite/gneiss). Methane is abundant (often >100 {mu}g/L) in ground water samples from the sites with lower hydraulic conductivity, especially with base flow discharge during late summer. Concentrations of methane are lowest at Gallina Creek, the site with high hydraulic conductivity. Methane concentrations are generally lowest during the winter and following spring snow melt at all three sites. Within a site, methane concentrations are commonly high in zones of ground water discharge (upwelling) and low in zones of ground water recharge (downwelling). Surface waters in all three sites are supersaturated with methane, indicating production and/or import form adjacent ground water environments.

  14. Radiation transport in earth for neutron and gamma ray point sources above an air-ground interface

    International Nuclear Information System (INIS)

    Two-dimensional discrete ordinates methods were used to calculate the instantaneous dose rate in silicon and neutron and gamma ray fluences as a function of depth in earth from point sources at various heights (1.0, 61.3, and 731.5 meters) above an air--ground interface. The radiation incident on the earth's surface was transported through an earth-only and an earth--concrete model containing 0.9 meters of borated concrete beginning 0.5 meters below the earth's surface to obtain fluence distributions to a depth of 3.0 meters. The inclusion of borated concrete did not significantly reduce the total instantaneous dose rate in silicon and, in all cases, the secondary gamma ray fluence and corresponding dose are substantially larger than the primary neutron fluence and corresponding dose for depths greater than 0.6 meter. 4 figures, 4 tables

  15. Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

    Science.gov (United States)

    Falk von Rudorff, Guido; Jakobsen, Rasmus; Rosso, Kevin M.; Blumberger, Jochen

    2016-10-01

    The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O-) and doubly protonated oxygens (-OH2+ ) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.

  16. Non-equilibrium magnetic colloidal dispersions at liquid-air interfaces: dynamic patterns, magnetic order and self-assembled swimmers.

    Science.gov (United States)

    Snezhko, Alexey

    2011-04-20

    Colloidal dispersions of interacting particles subjected to an external periodic forcing often develop nontrivial self-assembled patterns and complex collective behavior. A fundamental issue is how collective ordering in such non-equilibrium systems arises from the dynamics of discrete interacting components. In addition, from a practical viewpoint, by working in regimes far from equilibrium new self-organized structures which are generally not available through equilibrium thermodynamics can be created. In this review spontaneous self-assembly phenomena in magnetic colloidal dispersions suspended at liquid-air interfaces and driven out of equilibrium by an alternating magnetic field are presented. Experiments reveal a new type of nontrivially ordered self-assembled structures emerging in such systems in a certain range of excitation parameters. These dynamic structures emerge as a result of the competition between magnetic and hydrodynamic forces and have complex unconventional magnetic ordering. Nontrivial self-induced hydrodynamic fields accompany each out-of-equilibrium pattern. Spontaneous symmetry breaking of the self-induced surface flows leading to a formation of self-propelled microstructures has been discovered. Some features of the self-localized structures can be understood in the framework of the amplitude equation (Ginzburg-Landau type equation) for parametric waves coupled to the conservation law equation describing the evolution of the magnetic particle density and the Navier-Stokes equation for hydrodynamic flows. To understand the fundamental microscopic mechanisms governing self-assembly processes in magnetic colloidal dispersions at liquid-air interfaces a first-principle model for a non-equilibrium self-assembly is presented. The latter model allows us to capture in detail the entire process of out-of-equilibrium self-assembly in the system and reproduces most of the observed phenomenology.

  17. The neuroergonomic evaluation of human machine interface design in air traffic control using behavioral and EGG/ERP measures.

    Science.gov (United States)

    Giraudet, L; Imbert, J-P; Bérenger, M; Tremblay, S; Causse, M

    2015-11-01

    The Air Traffic Control (ATC) environment is complex and safety-critical. Whilst exchanging information with pilots, controllers must also be alert to visual notifications displayed on the radar screen (e.g., warning which indicates a loss of minimum separation between aircraft). Under the assumption that attentional resources are shared between vision and hearing, the visual interface design may also impact the ability to process these auditory stimuli. Using a simulated ATC task, we compared the behavioral and neural responses to two different visual notification designs--the operational alarm that involves blinking colored "ALRT" displayed around the label of the notified plane ("Color-Blink"), and the more salient alarm involving the same blinking text plus four moving yellow chevrons ("Box-Animation"). Participants performed a concurrent auditory task with the requirement to react to rare pitch tones. P300 from the occurrence of the tones was taken as an indicator of remaining attentional resources. Participants who were presented with the more salient visual design showed better accuracy than the group with the suboptimal operational design. On a physiological level, auditory P300 amplitude in the former group was greater than that observed in the latter group. One potential explanation is that the enhanced visual design freed up attentional resources which, in turn, improved the cerebral processing of the auditory stimuli. These results suggest that P300 amplitude can be used as a valid estimation of the efficiency of interface designs, and of cognitive load more generally. PMID:26200718

  18. Countercurrent air/water and steam/water flow above a perforated plate. Report for October 1978-October 1979

    International Nuclear Information System (INIS)

    The perforated plate weeping phenomena have been studied in both air/water and steam/cold water systems. The air/water experiment is designed to investigate the effect of geometric factors of the perforated plate on the rate of weeping. A new dimensionless flow rate in the form of H star is suggested. The data obtained are successfully correlated by this H star scaling in the conventional flooding equation. The steam/cold water experiment is concentrated on locating the boundary between weeping and no weeping. The effects of water subcooling, water inlet flow rate, and position of water spray are investigated. Depending on the combination of these factors, several types of weeping were observed. The data obtained at high water spray position can be related to the air/water flooding correlation by replacing the stream flow rate to an effective stream flow rate, which is determined by the mixing efficiency above the plate

  19. Bifluoride ([HF2](-)) formation at the fluoridated aluminium hydroxide/water interface.

    Science.gov (United States)

    Shimizu, Kenichi; Driver, Gordon W; Lucas, Marie; Sparrman, Tobias; Shchukarev, Andrey; Boily, Jean-François

    2016-05-31

    This study uncovers bifluoride-type (difluorohydrogenate(i); [HF2](-)) species formed at mineral/water interfaces. Bifluoride forms at [triple bond, length as m-dash]Al-F surface sites resulting from the partial fluoridation of gibbsite (γ-Al(OH3)) and bayerite (α-Al(OH3)) particles exposed to aqueous solutions of 50 mM NaF. Fluoride removal from these solutions is proton-promoted and results in a strongly self-buffered suspensions at circumneutral pH, proceeds at a F : H consumption ratio of 2 : 1, and with recorded losses of up to 17 mM fluoride (58 F nm(-2)). These loadings exceed crystallographic site densities by a factor of 3-4, yet the reactions have no resolvable impact on particle size, shape and mineralogy. X-ray photoelectron spectroscopy (XPS) of frozen (-155 °C) wet mineral pastes revealed coexisting surface F(-) and HF(0) species. Electron energy loss features pointed to multilayer distribution of these species at the mineral/water interface. XPS also uncovered a distinct form of Na(+) involved in binding fluoride-bearing species. XPS and solid state magic angle spinning (19)F nuclear magnetic resonance measurements showed that these fluoride species were highly comparable to a sodium-bifluoride (NaHF2) reference. First layer surface species are represented as [triple bond, length as m-dash]Al-F-H-F-Al[triple bond, length as m-dash] and [triple bond, length as m-dash]Al-F-Na-F-Al[triple bond, length as m-dash], and may form multi-layered species into the mineral/water interface. These results consequently point to a potentially overlooked inorganic fluorine species in a technologically relevant mineral/water interfacial systems.

  20. Interaction of Alcanivorax borkumensis with a Surfactant Decorated Oil-Water Interface.

    Science.gov (United States)

    Bookstaver, Michelle; Bose, Arijit; Tripathi, Anubhav

    2015-06-01

    Alcanivorax borkumensis is a hydrocarbon degrading bacterium linked to oil degradation around oil spill sites. It is known to be a surface bacterium leading to substantial interaction with the oil-water interface. Because of its abundance in oil spill regions, it has great potential to be used actively in oil spill remediation. Dispersants are thought to be important in the creation of oil-in-water emulsions that are meant to aid in the biodegradation process by bacteria. Although it is likely that some sort of dispersant will be used again in the case of another oil spill, to date, no studies have shown the impact of dispersants on the bacteria population. Corexit 9500 was the main dispersant used during the Deepwater Horizon oil spill, but little is known about its effect on the bacteria community. We built an experimental platform to quantitatively measure the transient growth of Alcanivorax borkumensis at the interface of oil and water. To our knowledge, this is the first study of how A. borkumensis interacts with a surfactant decorated oil-water interface. We use COREXIT EC9500A, cetylytrimethylamonium bromide, dioctyl sulfosuccinate sodium salt, l-α-phosphatidylcholine, sodium dodecyl sulfate, and Tween 20 to investigate the impact of dispersants on Alcanivorax borkumensis. We assess the impact of these dispersants on the growth rate, lag time, and maximum concentration of Alcanivorax borkumensis. We show that the charge, structure, and surface activity of these surfactants greatly impact the growth of A. borkumensis. Our results indicated that out of the surfactants tested only Tween 20 assists Acanivorax borkumensis growth. The results of this study will be important in the decision of dispersant use in the future.

  1. High density gas state at water/graphite interface studied by molecular dynamics simulation

    Institute of Scientific and Technical Information of China (English)

    Wang Chun-Lei; Li Zhao-Xia; Li Jing-Yuan; Xiu Peng; Hu Jun; Fang Hai-Ping

    2008-01-01

    In this paper molecular dynamics simulations are performed to study the accumulation behaviour of N2 and H2 at water/graphite interface under ambient temperature and pressure. It finds that both N2 and H2 molecules can accumulate at the interface and form one of two states according to the ratio of gas molecules number to square of graphite surface from our simulation results: gas films (pancake-like) for a larger ratio and nanobubbles for a Smaller ratio. In addition, we discuss the stabilities of nanobubbles at different environment temperatures. Surprisingly, it is found that the density of both kinds of gas states can be greatly increased, even comparable with that of the liquid N2 and liquid H2. The present results are expected to be helpful for the understanding of the stable existence of gas film (pancake-like) and nanobubbles.

  2. Numerical and experimental study of dissociation in an air-water single-bubble sonoluminescence system.

    Science.gov (United States)

    Puente, Gabriela F; Urteaga, Raúl; Bonetto, Fabián J

    2005-10-01

    We performed a comprehensive numerical and experimental analysis of dissociation effects in an air bubble in water acoustically levitated in a spherical resonator. Our numerical approach is based on suitable models for the different effects considered. We compared model predictions with experimental results obtained in our laboratory in the whole phase parameter space, for acoustic pressures from the bubble dissolution limit up to bubble extinction. The effects were taken into account simultaneously to consider the transition from nonsonoluminescence to sonoluminescence bubbles. The model includes (1) inside the bubble, transient and spatially nonuniform heat transfer using a collocation points method, dissociation of O2 and N2, and mass diffusion of vapor in the noncondensable gases; (2) at the bubble interface, nonequilibrium evaporation and condensation of water and a temperature jump due to the accommodation coefficient; (3) in the liquid, transient and spatially nonuniform heat transfer using a collocation points method, and mass diffusion of the gas in the liquid. The model is completed with a Rayleigh-Plesset equation with liquid compressible terms and vapor mass transfer. We computed the boundary for the shape instability based on the temporal evolution of the computed radius. The model is valid for an arbitrary number of dissociable gases dissolved in the liquid. We also obtained absolute measurements for R(t) using two photodetectors and Mie scattering calculations. The robust technique used allows the estimation of experimental results of absolute R0 and P(a). The technique is based on identifying the bubble dissolution limit coincident with the parametric instability in (P(a),R0) parameter space. We take advantage of the fact that this point can be determined experimentally with high precision and replicability. We computed the equilibrium concentration of the different gaseous species and water vapor during collapse as a function of P(a) and R0. The

  3. Drying nano particles solution on an oscillating tip at an air liquid interface: what we can learn, what we can do

    Directory of Open Access Journals (Sweden)

    Mariolle Denis

    2007-01-01

    Full Text Available AbstractEvaporation of fluid at micro and nanometer scale may be used to self-assemble nanometre-sized particles in suspension. Evaporating process can be used to gently control flow in micro and nanofluidics, thus providing a potential mean to design a fine pattern onto a surface or to functionalize a nanoprobe tip. In this paper, we present an original experimental approach to explore this open and rather virgin domain. We use an oscillating tip at an air liquid interface with a controlled dipping depth of the tip within the range of the micrometer. Also, very small dipping depths of a few ten nanometers were achieved with multi walls carbon nanotubes glued at the tip apex. The liquid is an aqueous solution of functionalized nanoparticles diluted in water. Evaporation of water is the driving force determining the arrangement of nanoparticles on the tip. The results show various nanoparticles deposition patterns, from which the deposits can be classified in two categories. The type of deposit is shown to be strongly dependent on whether or not the triple line is pinned and of the peptide coating of the gold nanoparticle. In order to assess the classification, companion dynamical studies of nanomeniscus and related dissipation processes involved with thinning effects are presented.

  4. Stability of the volume of air trapped on the abdomen of the water spider Argyroneta aquatica

    OpenAIRE

    Neumann, Dietrich; Woermann, Dietrich

    2013-01-01

    The water spider Argyroneta aquatica lives under water, diving to various depths from time to time. At rest, it breathes air trapped within its diving bell with a hydrophilic surface. Outside their diving bell water spiders trap air on their abdomen under a layer of hydrophobic hair. Is the structure of the layer of hair trapping a volume of air on the abdomen of the water spider Argyroneta aquatica under water related to its observed diving depth (of the order of decimetre)? A positive answe...

  5. Formation of alkenes and oxygenated VOCs from light mediated surface chemistry of nonanoic acid at the air-seawater interface

    Science.gov (United States)

    Gonzalez, L.; Volkamer, R.; Ciuraru, R.; Bernard, F.; George, C.

    2013-12-01

    Organic carbon is relevant in the atmosphere because it affects oxidative capacity that determines the removal rate of climate active gases and modifies aerosols. The significant presence of organic compounds at the surface of the ocean is a source for primary and secondary aerosol formation that potentially can modify cloud cover. Field observations of glyoxal over the remote marine boundary layer, and the tropical free troposphere remain unexplained by atmospheric models, and indicate missing sources of marine organic carbon species from heterogeneous processes mediated by light. We have studied the light induced surface chemistry of synthetic aqueous -mixtures containing NaCl, NaBr, NaI, photosensitizers (humic acids) and an organic surfactant (nonanoic acid) in a photochemical Quartz flowreactor. The air from the flowreactor was transferred to a dark reactor where the products from photosensitized reactions at the air/sea interface were further exposed to ozone. The products were sampled in the presence/absence of light and ozone by Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS) and Light-Emitting-Diode Cavity-Enhanced Differential Optical Absorption Spectroscopy (LED-CE-DOAS). In the presence of light nonenal formation is observed. Addition of ozone leads to the formation of glyoxal, among other products. Further experiments were conducted in an atmospheric simulation chamber. We discuss first results and atmospheric implications.

  6. Energy performance of air-to-water and water-to-water heat pumps in hotel applications

    International Nuclear Information System (INIS)

    We present work on measurement of the energy performance of heat pumps for hotel operations in subtropical climates. Two city hotels in Hong Kong were investigated. The first case was an application of an air-to-water heat pump to provide heating for an outdoor swimming pool during the heating season. The second case was the installation of three water-to-water heat pumps to complement an existing boiler system for hot water supply. The heating energy output and corresponding electricity use were measured. The heat pump energy efficiency was evaluated in terms of the coefficient of performance (COP), defined as the heating energy output to the electrical energy use. The air-to-water heat pump provided 49.1 MW h heating while consuming 24.6 MW h electricity during the 6((1)/(2))-month heating season from mid-October to April. For the water-to-water heat pumps, the estimated annual heating output and the electricity use were 952 and 544 MW h, respectively. It was found that the heat pumps generally operated in a COP range of 1.5-2.4, and the payback period was about two years, which was considered financially attractive

  7. Effect of surfactant structure on properties of oil/water interfaces : A coarse-grained molecular simulation study.

    OpenAIRE

    Rekvig, Live

    2004-01-01

    The elastic properties of oil/water/surfactant interfaces play an important role in the phase behaviour of microemulsions and for the stability of macroemulsions. The aim of this thesis is to obtain an understanding of the relationship between the structure of the surfactant molecules, the structure of the interface, and macroscopic interfacial properties. To achieve this aim, we performed molecular simulations of oil/water/surfactant systems. We made a quantitative comparison of various mo...

  8. Air and blood fluid dynamics: at the interface between engineering and medicine

    Science.gov (United States)

    Pollard, A.; Secretain, F.; Milne, B.

    2014-08-01

    The flows in the human upper airway and human heart during open heart surgery are considered. Beginning with idealized models of the human upper airway, current methods to extract realistic airway geometries using a novel implementation of optical coherent tomography modality are introduced. Complementary direct numerical simulations are considered that will assist in pre-surgery planning for obstructive sleep apnea. Cardiac air bubbles often arise during open heart surgery. These bubbles are potential emboli that can cause neurological impairment and even death. An experimental programme is outlined that uses acoustic sound to instil bubble surface oscillations that result in bubble breakup. A novel algorithm is introduced that enables a surgical team to obtain real-time in-vivo bubble data to aid cardiac de-airation procedures.

  9. Automated system for measuring the surface dilational modulus of liquid-air interfaces

    Science.gov (United States)

    Stadler, Dominik; Hofmann, Matthias J.; Motschmann, Hubert; Shamonin, Mikhail

    2016-06-01

    The surface dilational modulus is a crucial parameter for describing the rheological properties of aqueous surfactant solutions. These properties are important for many technological processes. The present paper describes a fully automated instrument based on the oscillating bubble technique. It works in the frequency range from 1 Hz to 500 Hz, where surfactant exchange dynamics governs the relaxation process. The originality of instrument design is the consistent combination of modern measurement technologies with advanced imaging and signal processing algorithms. Key steps on the way to reliable and precise measurements are the excitation of harmonic oscillation of the bubble, phase sensitive evaluation of the pressure response, adjustment and maintenance of the bubble shape to half sphere geometry for compensation of thermal drifts, contour tracing of the bubbles video images, removal of noise and artefacts within the image for improving the reliability of the measurement, and, in particular, a complex trigger scheme for the measurement of the oscillation amplitude, which may vary with frequency as a result of resonances. The corresponding automation and programming tasks are described in detail. Various programming strategies, such as the use of MATLAB® software and native C++ code are discussed. An advance in the measurement technique is demonstrated by a fully automated measurement. The instrument has the potential to mature into a standard technique in the fields of colloid and interface chemistry and provides a significant extension of the frequency range to established competing techniques and state-of-the-art devices based on the same measurement principle.

  10. Air-water oxygen exchange in a large whitewater river

    Science.gov (United States)

    Hall, Robert O.; Kennedy, Theodore A.; Rosi-Marshall, Emma J.

    2012-01-01

    Air-water gas exchange governs fluxes of gas into and out of aquatic ecosystems. Knowing this flux is necessary to calculate gas budgets (i.e., O2) to estimate whole-ecosystem metabolism and basin-scale carbon budgets. Empirical data on rates of gas exchange for streams, estuaries, and oceans are readily available. However, there are few data from large rivers and no data from whitewater rapids. We measured gas transfer velocity in the Colorado River, Grand Canyon, as decline in O2 saturation deficit, 7 times in a 28-km segment spanning 7 rapids. The O2 saturation deficit exists because of hypolimnetic discharge from Glen Canyon Dam, located 25 km upriver from Lees Ferry. Gas transfer velocity (k600) increased with slope of the immediate reach. k600 was -1 in flat reaches, while k600 for the steepest rapid ranged 3600-7700 cm h-1, an extremely high value of k600. Using the rate of gas exchange per unit length of water surface elevation (Kdrop, m-1), segment-integrated k600 varied between 74 and 101 cm h-1. Using Kdrop we scaled k600 to the remainder of the Colorado River in Grand Canyon. At the scale corresponding to the segment length where 80% of the O2 exchanged with the atmosphere (mean length = 26.1 km), k600 varied 4.5-fold between 56 and 272 cm h-1 with a mean of 113 cm h-1. Gas transfer velocity for the Colorado River was higher than those from other aquatic ecosystems because of large rapids. Our approach of scaling k600 based on Kdrop allows comparing gas transfer velocity across rivers with spatially heterogeneous morphology.

  11. Cell deformation at the air-liquid interface induces Ca2+-dependent ATP release from lung epithelial cells.

    Science.gov (United States)

    Ramsingh, Ronaldo; Grygorczyk, Alexandra; Solecki, Anna; Cherkaoui, Lalla Siham; Berthiaume, Yves; Grygorczyk, Ryszard

    2011-04-01

    Extracellular nucleotides regulate mucociliary clearance in the airways and surfactant secretion in alveoli. Their release is exquisitely mechanosensitive and may be induced by stretch as well as airflow shear stress acting on lung epithelia. We hypothesized that, in addition, tension forces at the air-liquid interface (ALI) may contribute to mechanosensitive ATP release in the lungs. Local depletion of airway surface liquid, mucins, and surfactants, which normally protect epithelial surfaces, facilitate such release and trigger compensatory mucin and fluid secretion processes. In this study, human bronchial epithelial 16HBE14o(-) and alveolar A549 cells were subjected to tension forces at the ALI by passing an air bubble over the cell monolayer in a flow-through chamber, or by air exposure while tilting the cell culture dish. Such stimulation induced significant ATP release not involving cell lysis, as verified by ethidium bromide staining. Confocal fluorescence microscopy disclosed reversible cell deformation in the monolayer part in contact with the ALI. Fura 2 fluorescence imaging revealed transient intracellular Ca(2+) elevation evoked by the ALI, which did not entail nonspecific Ca(2+) influx from the extracellular space. ATP release was reduced by ∼40 to ∼90% from cells loaded with the Ca(2+) chelator BAPTA-AM and was completely abolished by N-ethylmalemide (1 mM). These experiments demonstrate that in close proximity to the ALI, surface tension forces are transmitted directly on cells, causing their mechanical deformation and Ca(2+)-dependent exocytotic ATP release. Such a signaling mechanism may contribute to the detection of local deficiency of airway surface liquid and surfactants on the lung surface. PMID:21239538

  12. The Interface Conditions for Pressures at Oil-water Flood Front in the Porous Media Considering Capillary Pressure

    CERN Document Server

    Peng, Xiaolong; Du, Zhimin

    2016-01-01

    Flood front is the jump interface where fluids distribute discontinuously, whose interface condition is the theoretical basis of a mathematical model of the multiphase flow in porous medium. The conventional interface condition at the jump interface is expressed as the continuous Darcy velocity and fluid pressure (named CPVCM). This paper has inspected it via the studying the water-oil displacement in one dimensional reservoir with considering capillary pressure but ignoring the compressibility and gravity. It is proved theoretically that the total Darcy velocity and total pressure (defined by Antoncev etc.), instead of the Darcy velocities and pressures of water and oil, are continuous at the flood front without considering the compressibility of fluid and porous media. After that, new interface conditions for the pressures and Darcy velocity of each fluid are established, which are collectively named as Jump Pressures and Velocities Conditions Model (JPVCM) because the model has shown the jump pressures and...

  13. Enhancement of nitrate removal at the sediment-water interface by carbon addition plus vertical mixing.

    Science.gov (United States)

    Chen, Xuechu; He, Shengbing; Zhang, Yueping; Huang, Xiaobo; Huang, Yingying; Chen, Danyue; Huang, Xiaochen; Tang, Jianwu

    2015-10-01

    Wetlands and ponds are frequently used to remove nitrate from effluents or runoffs. However, the efficiency of this approach is limited. Based on the assumption that introducing vertical mixing to water column plus carbon addition would benefit the diffusion across the sediment-water interface, we conducted simulation experiments to identify a method for enhancing nitrate removal. The results suggested that the sediment-water interface has a great potential for nitrate removal, and the potential can be activated after several days of acclimation. Adding additional carbon plus mixing significantly increases the nitrate removal capacity, and the removal of total nitrogen (TN) and nitrate-nitrogen (NO3(-)-N) is well fitted to a first-order reaction model. Adding Hydrilla verticillata debris as a carbon source increased nitrate removal, whereas adding Eichhornia crassipe decreased it. Adding ethanol plus mixing greatly improved the removal performance, with the removal rate of NO3(-)-N and TN reaching 15.0-16.5 g m(-2) d(-1). The feasibility of this enhancement method was further confirmed with a wetland microcosm, and the NO3(-)-N removal rate maintained at 10.0-12.0 g m(-2) d(-1) at a hydraulic loading rate of 0.5 m d(-1). PMID:25556005

  14. Ecosystem engineering at the sediment-water interface: bioturbation and consumer-substrate interaction.

    Science.gov (United States)

    Nogaro, Géraldine; Mermillod-Blondin, Florian; Valett, Maurice H; François-Carcaillet, Frédérique; Gaudet, Jean-Paul; Lafont, Michel; Gibert, Janine

    2009-08-01

    In soft-bottom sediments, consumers may influence ecosystem function more via engineering that alters abiotic resources than through trophic influences. Understanding the influence of bioturbation on physical, chemical, and biological processes of the water-sediment interface requires investigating top-down (consumer) and bottom-up (resource) forces. The objective of the present study was to determine how consumer bioturbation mode and sediment properties interact to dictate the hydrologic function of experimental filtration systems clogged by the deposition of fine sediments. Three fine-grained sediments characterized by different organic matter (OM) and pollutant content were used to assess the influence of resource type: sediment of urban origin highly loaded with OM and pollutants, river sediments rich in OM, and river sediments poor in OM content. The effects of consumer bioturbation (chironomid larvae vs. tubificid worms) on sediment reworking, changes in hydraulic head and hydraulic conductivity, and water fluxes through the water-sediment interface were measured. Invertebrate influences in reducing the clogging process depended not only on the mode of bioturbation (construction of biogenic structures, burrowing and feeding activities, etc.) but also on the interaction between the bioturbation process and the sediments of the clogging layer. We present a conceptual model that highlights the importance of sediment influences on bioturbation and argues for the integration of bottom-up influence on consumer engineering activities. PMID:19462183

  15. Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces

    Science.gov (United States)

    Voïtchovsky, Kislon; Giofrè, Daniele; José Segura, Juan; Stellacci, Francesco; Ceriotti, Michele

    2016-01-01

    At the interface with solids, the mobility of liquid molecules tends to be reduced compared with bulk, often resulting in increased local order due to interactions with the surface of the solid. At room temperature, liquids such as water and methanol can form solvation structures, but the molecules remain highly mobile, thus preventing the formation of long-lived supramolecular assemblies. Here we show that mixtures of water with methanol can form a novel type of interfaces with hydrophobic solids. Combining in situ atomic force microscopy and multiscale molecular dynamics simulations, we identify solid-like two-dimensional interfacial structures that nucleate thermally, and are held together by an extended network of hydrogen bonds. On graphite, nucleation occurs above ∼35 °C, resulting in robust, multilayered nanoscopic patterns. Our findings could have an impact on many fields where water-alcohol mixtures play an important role such as fuel cells, chemical synthesis, self-assembly, catalysis and surface treatments. PMID:27713413

  16. Study on air carry-under by water jet plunging into water pool

    International Nuclear Information System (INIS)

    When liquid flows down into a liquid pool as a jet flow or a film flow on a wall, it sometimes accompanies gas into the pool. If the penetrated gas drifts up and leaves from the pool surface, the phenomenon is harmless. However, when the pool is highly agitated or strong flow exists from the pool, the mingled gas in liquid is carried out from the pool. The mixed gas in the coolant may reach the reactor core such as the light water reactor or the fast bleeder reactor. It severely affects the reactivity. Thus, the carry-under of gas into the water pool by the liquid down-flow is important issue for nuclear reactors. In the present study, air carry-under into the water pool is examined in visually approach. (author)

  17. Computational Molecular Modeling of the Multi-Scale Dynamics of Water and Ions at Cement Interfaces

    International Nuclear Information System (INIS)

    Structural and dynamic behavior of H2O molecules and aqueous at interfaces and in nano-pores of model C-S-H binding phase (tobermorite) is quantified on the basis of molecular dynamics computer simulations. At the (001) surface of tobermorite in contact with 0.25 M KCl aqueous solution, we can effectively distinguish water molecules that spend most of their time within channels between the 'drierketten chains' of silica on the tobermorite surface from the adsorbed molecules residing slightly above the interface. Within the channels, H2O molecules donate H-bonds to both the bridging and non-bridging oxygens of the Si-tetrahedra as well as to other H2O. Some of these molecules form very strong H-bonds persisting over 100 ps and longer, but many others undergo frequent liberations and occasional diffusional jumps from one surface site to another. The average diffusion coefficients of the surface-associated H2O molecules that spend most of their time in the channels and those that lie above the nominal interface differ by about an order of magnitude (D(H2O)[internal]=5.0*10-11 m2/s and D(H2O)[external]=6.0*10-10 m2/s, respectively). The average diffusion coefficient for all surface-associated H2O molecules is about 1.0*10-10 m2/s. All of these values are significantly less than the value of 2.3*10-9 m2/s, characteristic of H2O self-diffusion in bulk liquid water, but they are in very good quantitative agreement with experimental data on the dynamics surface-associated water in similar cement materials obtained by 1H NMR. (authors)

  18. Co-current air-water flow in downward sloping pipes: Transport of capacity reducing gas pockets in wastewater mains

    OpenAIRE

    Pothof, I.W.M.

    2011-01-01

    Air-water flow is an undesired condition in many systems for the transportation of water or wastewater. Air in storm water tunnels may get trapped and negatively affect the system. Air pockets in hydropower tunnels or sewers may cause blow-back events and inadmissible pressure spikes. Water pipes and wastewater pressure mains in particular are subject to air pocket formation in downward-sloping reaches, such as inverted siphons or terrain slopes. Air pocket accumulation causes energy losses a...

  19. Surfactant controlled switching of water-in-oil wetting behaviour of porous silica films grown at oil-water interfaces

    Indian Academy of Sciences (India)

    Manish M Kulkarni; Rajdip Bandyopadhyaya; Ashutosh Sharma

    2008-11-01

    Selective permeation of oil and water across a porous medium, as in oil recovery operations, depends on the preferential wetting properties of the porous medium. We show a profound influence of surfactants in wetting of porous media and thus demonstrate a new route for the control of water-in-oil wetting of porous substrates by changing the concentration of surfactants in an aqueous sub-phase below the substrate. This strategy is employed to engineer partial reversible wetting transitions on a porous silica film. The film itself is grown and stabilized on a flat, macroscopic interface between an oil phase and an aqueous sub-phase. On increasing the surfactant (CTAB) concentration in the sub-phase, contact angle of a water drop (placed on the oil side of the film) changes from 140° to 16° in 25 min by diffusion of the surfactant across the porous film. On further replacement of the sub-phase with pure water, diffusion of the surfactant from the water drop back to the sub-phase was slower, increasing the contact angle in the process from 16° to 90° in 2 h. Wettability control by a cationic surfactant (CTAB) was found to be much faster (6 deg/min) than that offered by an anionic surfactant, SDS (0.05 deg/min). Switching of the surface wettability due to the surfactant diffusion may have implications in oil-water separation, chemical bed reactors and microfluidic devices.

  20. Influence of mangrove zonation on CO2 fluxes at the sediment-air interface (New Caledonia)

    OpenAIRE

    Leopold, A.; Marchand, Cyril; Deborde, J.; Chaduteau, C.; Allenbach, M.

    2013-01-01

    Mangroves are the major ecosystems of tropical and subtropical coastlines. They are considered as a sink for atmospheric CO2 because they are characterized both by high net primary production, and by low rates of organic matter decomposition. However, a recent reassessment of the global mangrove budget suggests that organic carbon sinks have been underestimated, notably CO2 efflux from sediments and creek waters, and tidal export of dissolved inorganic carbon. Our objective was to understand ...

  1. Managing the Drivers of Air Flow and Water Vapor Transport in Existing Single Family Homes (Revised)

    Energy Technology Data Exchange (ETDEWEB)

    Cummings, J.; Withers, C.; Martin, E.; Moyer, N.

    2012-10-01

    This document focuses on managing the driving forces which move air and moisture across the building envelope. While other previously published Measure Guidelines focus on elimination of air pathways, the ultimate goal of this Measure Guideline is to manage drivers which cause air flow and water vapor transport across the building envelope (and also within the home), control air infiltration, keep relative humidity (RH) within acceptable limits, avoid combustion safety problems, improve occupant comfort, and reduce house energy use.

  2. A comparison of didodecyldimethylammonium bromide adsorbed at mica/water and silica/water interfaces using neutron reflection.

    Science.gov (United States)

    Griffin, Lucy R; Browning, Kathryn L; Truscott, Chris L; Clifton, Luke A; Webster, John; Clarke, Stuart M

    2016-09-15

    The layer structure of the dichain alkyl ammonium surfactant, didodecyldimethylammonium bromide (DDAB), adsorbed from water on to silica and mica surfaces has been determined using neutron reflection. Although sometimes considered interchangeable surfaces for study, we present evidence of significant differences in the adsorbed layer structure below the critical micelle concentration. A complete DDAB bilayer was assembled at the water/mica interface at concentrations below the critical micelle concentration (CMC). In contrast it is not until the CMC was reached that the complete bilayer structure formed on the oxidised silicon crystal. Removal of the complete bilayer on both surfaces was attempted by both washing and ion exchange yet the adsorbed structure proved tenacious. PMID:27318715

  3. Influence of water depth on the sound generated by air-bubble vibration in the water musical instrument

    Science.gov (United States)

    Ohuchi, Yoshito; Nakazono, Yoichi

    2014-06-01

    We have developed a water musical instrument that generates sound by the falling of water drops within resonance tubes. The instrument can give people who hear it the healing effect inherent in the sound of water. The sound produced by falling water drops arises from air- bubble vibrations. To investigate the impact of water depth on the air-bubble vibrations, we conducted experiments at varying values of water pressure and nozzle shape. We found that air-bubble vibration frequency does not change at a water depth of 50 mm or greater. Between 35 and 40 mm, however, the frequency decreases. At water depths of 30 mm or below, the air-bubble vibration frequency increases. In our tests, we varied the nozzle diameter from 2 to 4 mm. In addition, we discovered that the time taken for air-bubble vibration to start after the water drops start falling is constant at water depths of 40 mm or greater, but slower at depths below 40 mm.

  4. Co-current air-water flow in downward sloping pipes: Transport of capacity reducing gas pockets in wastewater mains

    NARCIS (Netherlands)

    Pothof, I.W.M.

    2011-01-01

    Air-water flow is an undesired condition in many systems for the transportation of water or wastewater. Air in storm water tunnels may get trapped and negatively affect the system. Air pockets in hydropower tunnels or sewers may cause blow-back events and inadmissible pressure spikes. Water pipes an

  5. High electrical permittivity of ultrapure water at the water-platinum interface

    Science.gov (United States)

    Musumeci, Francesco; Pollack, Gerald H.

    2014-10-01

    The discharge of a platinum parallel-plate capacitor filled with ultrapure water has been measured. The observed discharge trend can be described by a Modified Poisson-Boltzmann Equation (MPB) only when the voltage is very low. Increasing the applied voltage creates an ‘exclusion zone' in which the MPB equation no longer fits, and the system capacitance shows a dependence on the spacing between the two platinum plates. The permittivity of water, calculated considering the system as a plane capacitor, appears to be very high. This implies that the exclusion zone could have extraordinary dielectric properties.

  6. Effects of Female Sex Hormones on Susceptibility to HSV-2 in Vaginal Cells Grown in Air-Liquid Interface.

    Science.gov (United States)

    Lee, Yung; Dizzell, Sara E; Leung, Vivian; Nazli, Aisha; Zahoor, Muhammad A; Fichorova, Raina N; Kaushic, Charu

    2016-01-01

    The lower female reproductive tract (FRT) is comprised of the cervix and vagina, surfaces that are continuously exposed to a variety of commensal and pathogenic organisms. Sexually transmitted viruses, such as herpes simplex virus type 2 (HSV-2), have to traverse the mucosal epithelial lining of the FRT to establish infection. The majority of current culture systems that model the host-pathogen interactions in the mucosal epithelium have limitations in simulating physiological conditions as they employ a liquid-liquid interface (LLI), in which both apical and basolateral surfaces are submerged in growth medium. We designed the current study to simulate in vivo conditions by growing an immortalized vaginal epithelial cell line (Vk2/E6E7) in culture with an air-liquid interface (ALI) and examined the effects of female sex hormones on their growth, differentiation, and susceptibility to HSV-2 under these conditions, in comparison to LLI cultures. ALI conditions induced Vk2/E6E7 cells to grow into multi-layered cultures compared to the monolayers present in LLI conditions. Vk2 cells in ALI showed higher production of cytokeratin in the presence of estradiol (E2), compared to cells grown in progesterone (P4). Cells grown under ALI conditions were exposed to HSV-2-green fluorescent protein (GFP) and the highest infection and replication was observed in the presence of P4. Altogether, this study suggests that ALI cultures more closely simulate the in vivo conditions of the FRT compared to the conventional LLI cultures. Furthermore, under these conditions P4 was found to confer higher susceptibility to HSV-2 infection in vaginal cells. The vaginal ALI culture system offers a better alternative to study host-pathogen interactions. PMID:27589787

  7. Ab initio study on microscopic properties of III-V/water interfaces for photoelectrochemical hydrogen production

    Science.gov (United States)

    Wood, Brandon; Choi, Woon Ih; Schwegler, Eric; Ogitsu, Tadashi

    2013-03-01

    Photoelectrodes made of III-V semiconductors are known to exhibit very high solar-to-hydrogen conversion efficiency (from solar energy to chemical energy as H2 bond); however, photocorrosion of the electrode in electrolyte solution remains an issue. Based on ab-initio molecular dynamics simulations, we study the structure, stability, and chemical activity of GaP/InP(001) semiconductor electrodes in contact with water. We will show how surface oxygen and hydroxyl change the electronic and chemical properties of water at the interface, leading to the formation of a strong hydrogen-bond network where fast surface hydrogen transport seems to be realized. Implications from our findings will be discussed in detail at the presentation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.

  8. Viscous memory effects on the generation of hierarchical morphologies at an emulsified oil/water interface

    Science.gov (United States)

    Morris, Melanie L.; Gross, Michael C.; Panigrahi, Asmi; Deacon, Ryan M.; Chan, Patrick; Benkoski, Jason J.

    2012-02-01

    A defining feature of biological materials is their fractal morphology. Cancellous bone, pulmonary alveoli, small intestine villi, neural networks, and bladder epithelium are just a few examples of biological structures with hierarchically organized topographies spanning multiple length scales. Herein we present a self-assembly method that faithfully reproduces the topographic features of these biomaterials. The system consists of a photocurable monomer and water. To this quasi-two-component system we add surfactants that sculpt the interface into the desired shape. The resulting structures are then solidi?ed by crosslinking with UV light. Drawing from the rich phase behavior of oil/water/surfactant systems, we demonstrate complex fractal morphologies over many length scales ranging from several mm down to 100 nm. Quantitative image analysis reveals fractal morphologies with at least four distinct levels of hierarchy. Increasing viscosity, in particular, shows a strong correlation with the number of hierarchical levels.

  9. Hydrophobicity-induced drying transition in alkanethiol self-assembled monolayer–water interface

    Indian Academy of Sciences (India)

    V Lakshminarayanan; Ujjal Kumar Sur

    2003-08-01

    During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon by a model for the alkanethiol monolayer–aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance. This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading to the possible creation of a hydrophobic interfacial gap.

  10. Viruses at Solid-Water Interfaces: A Systematic Assessment of Interactions Driving Adsorption.

    Science.gov (United States)

    Armanious, Antonius; Aeppli, Meret; Jacak, Ronald; Refardt, Dominik; Sigstam, Thérèse; Kohn, Tamar; Sander, Michael

    2016-01-19

    Adsorption to solid-water interfaces is a major process governing the fate of waterborne viruses in natural and engineered systems. The relative contributions of different interaction forces to adsorption and their dependence on the physicochemical properties of the viruses remain, however, only poorly understood. Herein, we systematically studied the adsorption of four bacteriophages (MS2, fr, GA, and Qβ) to five model surfaces with varying surface chemistries and to three dissolved organic matter adlayers, as a function of solution pH and ionic strength, using quartz crystal microbalance with dissipation monitoring. The viruses were selected to have similar sizes and shapes but different surface charges, polarities, and topographies, as identified by modeling the distributions of amino acids in the virus capsids. Virus-sorbent interactions were governed by long-ranged electrostatics and favorable contributions from the hydrophobic effect, and shorter-ranged van der Waals interactions were of secondary importance. Steric effects depended on the topographic irregularities on both the virus and sorbent surfaces. Differences in the adsorption characteristics of the tested viruses were successfully linked to differences in their capsid surface properties. Besides identifying the major interaction forces, this work highlights the potential of computable virus surface charge and polarity descriptors to predict virus adsorption to solid-water interfaces. PMID:26636722

  11. Molecular-scale Description of SPAN80 Desorption from the Squalane-Water Interface

    CERN Document Server

    Tan, L; Chaudhari, M I

    2016-01-01

    Extensive all-atom molecular dynamics calculations on the water-squalane interface for nine different loadings with sorbitan monooleate (SPAN80), at $T=300$K, are analyzed for the surface tension equation of state, desorption free energy profiles as they depend on loading, and to evaluate escape times for absorbed SPAN80 into the bulk phases. These results suggest that loading only weakly affects accommodation of a SPAN80 molecule by this squalane-water interface. Specifically, the surface tension equation of state is simple through the range of high tension to high loading studied, and the desorption free energy profiles are weakly dependent on loading here. The perpendicular motion of the centroid of the SPAN80 head-group ring is well-described by a diffusional model near the minimum of the desorption free energy profile. Lateral diffusional motion is weakly dependent on loading. Escape times evaluated on the basis of a diffusional model and the desorption free energies are $7\\times 10^{-2}$ s (into the squ...

  12. Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

    International Nuclear Information System (INIS)

    It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

  13. Experimental investigation on the droplet entrainment from interfacial waves in air-water horizontal stratified flow

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Byeong Geon; Yun, Byong Jo [Pusan national Univ., Pusan (Korea, Republic of); Kim, Kyoung Du [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    It was mainly due to the fact that droplet entrainment affects the Peak Cladding Temperature (PCT) of the nuclear fuel rod in the Postulated accident conditions of NPP. Recently, droplet entrainment in the horizontally arranged primary piping system for the NPP is of interest because it affects directly the steam binding phenomena in the steam generators. Pan and Hanratty correlation is the only applicable one for the droplet entrainment rate model for horizontal flow. Moreover, there are no efforts for the model development on the basis of the droplet entrainment principal and physics phenomena. More recently, Korea Atomic Energy Research Institute (KAERI) proposed a new mechanistic droplet generation model applicable in the horizontal pipe for the SPACE code. However, constitutive relations in this new model require three model coefficients which have not yet been decided. The purpose of present work is determining three model coefficients by visualization experiment. For these model coefficients, the major physical parameters regarding the interfacial disturbance wave should be measured in this experiments. There are the wave slope, liquid fraction, wave hypotenuse length, wave velocity, wave frequency, and wavelength in the major physical parameters. The experiment was conducted at an air water horizontal rectangular channel with the PIV system. In this study, the experimental conditions were stratified-way flow during the droplet generation. Three coefficients were determined based on several data related to the interfacial wave. Additionally, we manufactured the parallel wire conductance probe to measure the fluctuating water level over time, and compared the wave height measured by the parallel wire conductance probe and image processing from images taken by high speed camera. Experimental investigation was performed for droplet entrainment from phase interface wave in an air-water stratified flow. In the experiments, we measured major physical parameters

  14. Raman spectroscopy of solutions and interfaces containing nitrogen dioxide, water, and 1,4 dioxane: Evidence for repulsion of surface water by NO{sub 2} gas

    Energy Technology Data Exchange (ETDEWEB)

    Murdachaew, Garold [Institute of Chemistry and the Fritz Haber Research Center for Molecular Dynamics, Hebrew University, Jerusalem 91904 (Israel); Varner, Mychel E.; Veer, Wytze E. van der [Department of Chemistry, University of California, Irvine, California 92697 (United States); Gerber, R. Benny [Institute of Chemistry and the Fritz Haber Research Center for Molecular Dynamics, Hebrew University, Jerusalem 91904 (Israel); Department of Chemistry, University of California, Irvine, California 92697 (United States); Phillips, Leon F., E-mail: leon.phillips@canterbury.ac.nz [Department of Chemistry, University of California, Irvine, California 92697 (United States); Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)

    2014-05-14

    The interaction of water, 1,4 dioxane, and gaseous nitrogen dioxide, has been studied as a function of distance measured through the liquid-vapour interface by Raman spectroscopy with a narrow (<0.1 mm) laser beam directed parallel to the interface. The Raman spectra show that water is present at the surface of a dioxane-water mixture when gaseous NO{sub 2} is absent, but is virtually absent from the surface of a dioxane-water mixture when gaseous NO{sub 2} is present. This is consistent with recent theoretical calculations that show NO{sub 2} to be mildly hydrophobic.

  15. Turbulent heat exchange between water and ice at an evolving ice-water interface

    CERN Document Server

    Ramudu, Eshwan; Olson, Peter; Gnanadesikan, Anand

    2015-01-01

    We conduct laboratory experiments on the time evolution of an ice layer cooled from below and subjected to a turbulent shear flow of warm water from above. Our study is motivated by observations of warm water intrusion into the ocean cavity under Antarctic ice shelves, accelerating the melting of their basal surfaces. The strength of the applied turbulent shear flow in our experiments is represented in terms of its Reynolds number $\\textit{Re}$, which is varied over the range $2.0\\times10^3 \\le \\textit{Re} \\le 1.0\\times10^4$. Depending on the water temperature, partial transient melting of the ice occurs at the lower end of this range of $\\textit{Re}$ and complete transient melting of the ice occurs at the higher end. Following these episodes of transient melting, the ice reforms at a rate that is independent of $\\textit{Re}$. We fit our experimental measurements of ice thickness and temperature to a one-dimensional model for the evolution of the ice thickness in which the turbulent heat transfer is parameter...

  16. Turbulent heat exchange between water and ice at an evolving ice–water interface

    Science.gov (United States)

    Ramudu, Eshwan; Hirsh, Benjamin Henry; Olson, Peter; Gnanadesikan, Anand

    2016-07-01

    We conduct laboratory experiments on the time evolution of an ice layer cooled from below and subjected to a turbulent shear flow of warm water from above. Our study is motivated by observations of warm water intrusion into the ocean cavity under Antarctic ice shelves, accelerating the melting of their basal surfaces. The strength of the applied turbulent shear flow in our experiments is represented in terms of its Reynolds number $\\textit{Re}$, which is varied over the range $2.0\\times10^3 \\le \\textit{Re} \\le 1.0\\times10^4$. Depending on the water temperature, partial transient melting of the ice occurs at the lower end of this range of $\\textit{Re}$ and complete transient melting of the ice occurs at the higher end. Following these episodes of transient melting, the ice reforms at a rate that is independent of $\\textit{Re}$. We fit our experimental measurements of ice thickness and temperature to a one-dimensional model for the evolution of the ice thickness in which the turbulent heat transfer is parameterized in terms of the friction velocity of the shear flow. The melting mechanism we investigate in our experiments can easily account for the basal melting rate of Pine Island Glacier ice shelf inferred from observations.

  17. Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Gabriel V.; Müller, Erich A.; Jackson, George [Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Ford, Ian J. [Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT (United Kingdom); Hunt, Patricia A. [Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)

    2015-03-21

    The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large

  18. Second harmonic generation response by gold nanoparticles at the polarized water/2-octanone interface: from dispersed to aggregated particles

    Energy Technology Data Exchange (ETDEWEB)

    Galletto, P [Laboratoire d' Electrochimie Physique et Analytique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Girault, H H [Laboratoire d' Electrochimie Physique et Analytique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Gomis-Bas, C [Centre for Nanoscale Science, Department of Chemistry, University of Liverpool, Liverpool L69 3BX (United Kingdom); Schiffrin, D J [Centre for Nanoscale Science, Department of Chemistry, University of Liverpool, Liverpool L69 3BX (United Kingdom); Antoine, R [Universite Lyon 1, Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France); Broyer, M [Universite Lyon 1, Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France); Brevet, P F [Universite Lyon 1, Laboratoire de Spectrometrie Ionique et Moleculaire, UMR CNRS 5579, 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne Cedex (France)

    2007-09-19

    Gold nanoparticles with a diameter of approximately 20 nm have been observed at the polarized water/2-octanone interface by the nonlinear optical technique of second harmonic generation. Electric field induced adsorption of the gold particles at this liquid/liquid interface is clearly observed and confirms that these are negatively charged. The process is quasi-reversible at high potential sweep rates, but aggregation at the interface is observed at slower sweep rates through the loss of the nonlinear optical signal. The time evolution of the second harmonic signal is also reported during potential step experiments. After a rapid increase due to adsorption, a continuous decrease in the nonlinear optical signal intensity is observed due to aggregation of the particles into large islands at the interface. Diffusion of these large islands at the interface was observed for a longer timescale through large signal fluctuations.

  19. Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water

    Directory of Open Access Journals (Sweden)

    ANDRÉ G. SIMÃO

    2016-06-01

    Full Text Available Abstract The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert’s period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium.

  20. Subseafloor to Sea-Air Interface Characterization of Methane Dynamics in the northern US Atlantic Margin Seep Province

    Science.gov (United States)

    Ruppel, C. D.; Kluesner, J.; Danforth, W. W.; Casso, M.; Pohlman, J.

    2015-12-01

    Since the discovery of hundreds of northern US Atlantic margin (USAM) cold seeps in 2012 and 2013, the USGS Gas Hydrates Project has undertaken intensive studies of the along-margin gas hydrate/free gas distribution, the plumbing systems sustaining seeps, seafloor gas emissions, and sea-air methane flux. Interest in the USAM is motivated both by climate change (i.e., documented ocean warming may contribute to seepage) and energy resource (i.e., the amount of gas-in-place in hydrates on the USAM is about the same as that in the northern Gulf of Mexico) issues. USGS-led field efforts have included an April 2015 study to acquire high-resolution multichannel seismic data, coincident split-beam water column methane plume imaging data, and real-time sea-air methane flux measurements between Wilmington and Norfolk Canyons and a September 2015 cruise (with OSU, UCLA, and Geomar) to collect piston cores, multicores, heat flow data, subbottom imagery, CTDs, and coincident water column imagery from Block Canyon to the Currituck Slide. In April 2015, we discovered methane seeps not included in the previously-published database, but found that some known seeps were not active. New high-resolution multi-channel seismic data revealed clear differences between the deep gas distribution in mid-Atlantic upper slope zones that are replete with (up to 240 sites) and lacking in seeps. Based on sea-air flux measurements, even shallow-water outer shelf (~125 m water depth) seeps and a 900-m-high methane plume originating on the mid-slope do not contribute methane to the atmosphere. Using thermistors placed on piston core outriggers, we will in September 2015 acquire thermal data to identify zones of high fluid advection and to constrain background geotherms in areas where heat flow has never been measured. During that same cruise, we will collect a series of piston cores across the no-hydrate/hydrate transition on the upper slope to constrain fluid and gas dynamics in this zone.